Toward the Assembly of 2D Tunable Crystal Patterns of Spherical Colloids on a Wafer-ScaleClick to copy article linkArticle link copied!
- Kai SotthewesKai SotthewesPhysics of Interfaces and Nanomaterials, MESA+ Institute, University of Twente, P.O. Box 217, 7500AE Enschede, The NetherlandsMore by Kai Sotthewes
- Gijs RoozendaalGijs RoozendaalPhysics of Interfaces and Nanomaterials, MESA+ Institute, University of Twente, P.O. Box 217, 7500AE Enschede, The NetherlandsMesoscale Chemical Systems, MESA+ Institute, University of Twente, P.O. Box 217, 7500AE Enschede, The NetherlandsMore by Gijs Roozendaal
- Andris ŠutkaAndris ŠutkaInstitute of Materials and Surface Engineering, Faculty of Materials Science and Applied Chemistry, Riga Technical University, LV-1048 Riga, LatviaMore by Andris Šutka
- Ignaas S. M. Jimidar*Ignaas S. M. Jimidar*Email: [email protected]Department of Chemical Engineering CHIS, Vrije Universiteit Brussel, Brussels 1050, BelgiumMesoscale Chemical Systems, MESA+ Institute, University of Twente, P.O. Box 217, 7500AE Enschede, The NetherlandsMore by Ignaas S. M. Jimidar
Abstract
Entering an era of miniaturization prompted scientists to explore strategies to assemble colloidal crystals for numerous applications, including photonics. However, wet methods are intrinsically less versatile than dry methods, whereas the manual rubbing method of dry powders has been demonstrated only on sticky elastomeric layers, hindering particle transfer in printing applications and applicability in analytical screening. To address this clear impetus of broad applicability, we explore here the assembly on nonelastomeric, rigid substrates by utilizing the manual rubbing method to rapidly (≈20 s) attain monolayers comprising hexagonal closely packed (HCP) crystals of monodisperse dry powder spherical particles with a diameter ranging from 500 nm to 10 μm using a PDMS stamp. Our findings elucidate that the tribocharging-induced electrostatic attraction, particularly on relatively stiff substrates, and contact mechanics force between particles and substrates are critical contributors to attain large-scale HCP structures on conductive and insulating substrates. The best performance was obtained with polystyrene and PMMA powder, while silica was assembled only in HCP structures on fluorocarbon-coated substrates under zero-humidity conditions. Finally, we successfully demonstrated the assembly of tunable crystal patterns on a wafer-scale with great control on fluorocarbon-coated wafers, which is promising in microelectronics, bead-based assays, sensing, and anticounterfeiting applications.
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License Summary*
You are free to share(copy and redistribute) this article in any medium or format and to adapt(remix, transform, and build upon) the material for any purpose, even commercially within the parameters below:
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1. Introduction
2. Experimental Section
2.1. Materials and Methods
Figure 1
Figure 1. (a) Schematic illustration of the manual rubbing technique to assemble dry powder into closely packed crystal (HCP) structures on substrates using a PDMS (rubber) stamp; inset shows the iridescence structures observed of a 3 μm PMMA monolayer on a fluorocarbon coating on a Au-coated substrate under illumination (scale bar: 2 cm). SEM images of the uniformly fluorocarbon-coated silicon substrate covered with a monolayer of 10 μm (b) PMMA and (c) silica microspheres rubbed under standard lab conditions (RH = 40–55%) and (d) silica microspheres rubbed under zero-humidity glovebox conditions (RH = 0%). (e) Average normalized shape factors ϑnorm of the monolayers obtained on various substrates under standard lab conditions (RH = 40–55%; N = 40). (f) Average normalized shape factors ϑnorm of the monolayers obtained under zero-humidity glovebox conditions (N2-controlled environment) and standard lab conditions [RH = 40–55% (data taken from Figure 1e); N = 40]. Scale bar, green: 50 μm.
2.2. Characterization and Visualization
3. Relevant Interaction Forces in Dry Assembling Colloidal Particles
4. Results and Discussion
4.1. Various Substrates under Ambient Conditions
4.1.1. Nonconducting Substrates
Figure 2
Figure 2. Results of the KPFM measurement performed on the (a) 500 nm SiO2 substrate before (pristine) and after rubbing the PMMA microspheres using a PDMS stamp. Inset (a) shows the topographic image (7 × 7 μm2, scale bar: 1 μm) of the SiO2 substrate. (b) Topographic (25 × 25 μm2, scale bar: 6 μm) and (c) simultaneously obtained surface potential map (25 × 25 μm2, scale bar: 6 μm) of the 10 μm PMMA microspheres after the rubbing experiment.
4.1.2. Conductive Substrates
4.2. Different Stamps
Figure 3
Figure 3. (a) Average normalized shape factor ϑnorm,av of the 10 μm PMMA microsphere results obtained on the fluorocarbon-coated samples (N = 40) using three different stamps: pristine PDMS, PDMS wrapped in aluminum foil, and PDMS covered with a (PEBA)/α-FeOOH layer performed under ambient lab conditions (RH = 40–55%). (b) Force–distance curves of a silica colloidal probe on three different stamps obtained using the colloidal probe technique performed with the AFM. Inset (b) displays a silica colloidal probe with a diameter of 10 μm.
4.3. Other Particle Types and Sizes
Figure 4
Figure 4. SEM images of HCP crystal structures obtained from 3 μm (a) PMMA powder and (b) polystyrene microspheres and 500 nm (c) PMMA powder and (d) silica powder (inside the glovebox) obtained after rubbing experiments were performed using a PDMS stamp on mainly fluorocarbon-coated substrates. Only experiment (b) was performed on a Au-coated substrate. Scale bar: green = 15 μm; white = 3 μm.
4.4. Tunable HCP Crystal Patterns on Wafer-Scale
Figure 5
Figure 5. (a) Large area of tunable 2D crystal structures on a 4 in. fluorocarbon-coated patterned 8 μm SiO2 wafer after 3 μm PMMA powder was rubbed and subsequently pressurized air of 4–5 bar was laterally blown across the wafer (cf. Figures S9–S11). SEM images of patterned HCP crystal structures obtained using (b,c) 10 μm and (d,e) 3 μm PMMA powder microspheres on the same 8 μm SiO2 patterned wafer. The experiments were performed under ambient lab conditions (RH = 40–55%). Scale bar: green = 7 mm; black = 100 μm.
5. Conclusions
Supporting Information
The Supporting Information is available free of charge at https://pubs.acs.org/doi/10.1021/acsami.3c16830.
Additional experimental details, Voronoi approach to quantify the quality of the assembled monolayers, force spectroscopy measurements, determining Young’s modulus, Kelvin probe force microscopy details, monolayers assembled on the different stamps, and wafer-scale assembly of HCP crystals on tunable patterns and iridescence structure colors observed under illumination (PDF)
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Acknowledgments
The authors gratefully acknowledge funding from the Methusalem grant from VUB (METH 7) and recognize pioneering work performed by Jelle Verburg. The authors thank Linards Lapčinskis for producing PEBA/α-FeOOH samples, Stefan Schlautmann and Mitch de Waard for sample fabrication, and Mark Smithers, Remco Sanders, and Bas Haartsen for their time in taking sample images. I.S.M.J. is grateful for the support received from Gert Desmet and Han Gardeniers.
References
This article references 47 other publications.
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- 5Pan, R.; Zhang, W.; Cheng, H.; Yang, J.; Gong, Y.; Hu, R.; Zhuo, Y.; Ding, J.; Zhang, X.; Chen, L. Capillary Self-Assembly Register Microspheres to Fabricate Anisotropic Conductive Film Used for Ultra-Fine Pitch Stable Electrical Interfacing Interconnection. Adv. Mater. Technol. 2023, 8, 2300514, DOI: 10.1002/admt.202300514Google Scholar5https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BB3sXhsF2mt7zI&md5=55f734b38831905bc50339ffa11672a7Capillary Self-Assembly Register Microspheres to Fabricate Anisotropic Conductive Film Used for Ultra-Fine Pitch Stable Electrical Interfacing InterconnectionPan, Rui; Zhang, Wei; Cheng, Hua; Yang, Jihua; Gong, Yi; Hu, Rui; Zhuo, Yizhi; Ding, Jianjun; Zhang, Xian; Chen, Lin; Tian, XingyouAdvanced Materials Technologies (Weinheim, Germany) (2023), 8 (18), 2300514CODEN: AMTDCM; ISSN:2365-709X. (Wiley-VCH Verlag GmbH & Co. KGaA)The trend to integrate more electronic components in a limited space range motivates the development of advanced electronic packaging. Conventional electronic packaging is difficult to perform in stable interfacing interconnection pitch below 7 μm due to the possibility of short-circuit problems. Herein, a kind of anisotropic conductive film (μ-ACF) contg. periodically arranged conductive microspheres for microscale pitch elec. interfacing interconnection is developed. The periodic arrangement can avert the contact of conductive microspheres, thus enabling stable interconnection with a pitch as small as 5 μm. By coating conductive microspheres with a layer of silicon insulation, the pitch can be further reduced to 3 μm, which can prevent the formation of conductive pathways between electrodes even if they come into contact with each other. Such high-quality arrangement is achieved by lithog. and capillary self-assembly method, which is expected to be used in high-throughput prodn. Thanks to the delicate design, the μ-ACF can achieve a low contact resistance of 4.62 mΩ mm-2 and a spatial resoln. of 3 μm without short-circuit failure. The spatial resoln. can be further improved by adjusting the size of conductive microspheres, which is conducive to the development of highly integrated devices.
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- 8Vankeerberghen, B.; Verloy, S.; Jimidar, I. S.; Gardeniers, H.; Desmet, G. Structured microgroove columns as a potential solution to obtain perfectly ordered particle beds. J. Chromatogr. A 2023, 1700, 464031, DOI: 10.1016/j.chroma.2023.464031Google Scholar8https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BB3sXptlWmtb0%253D&md5=a63a418b68f3d08917fa4ab9f3130668Structured microgroove columns as a potential solution to obtain perfectly ordered particle bedsVankeerberghen, Bert; Verloy, Sandrien; Jimidar, Ignaas S. M.; Gardeniers, Han; Desmet, GertJournal of Chromatography A (2023), 1700 (), 464031CODEN: JCRAEY; ISSN:0021-9673. (Elsevier B.V.)A novel concept is reported to produce ordered beds of spherical particles in a suitable format for liq. chromatog. In this concept, spherical particles are either positioned individually (single-layer column) or stacked (multi-layer column) in micromachined pockets that form an interconnected array of micro-grooves acting as a perfectly ordered chromatog. column. As a first step towards realizing this concept, the breakthrough is reported that is realized by obtaining a soln. to uniformly fill the micro-groove arrays with spherical particles. This can be achieved in a few sweeps using a dedicated rubbing approach wherein a particle suspension is manually rubbed over a silicon chip. In addn., numerical calcns. of the dispersion in the newly introduced column format have been carried out and demonstrate the combined advantage of order and reduced flow resistance the newly proposed concept has over the conventional packed bed. For fully-porous particles and a zone retention factor of k'' = 2, the hmin decreases from hmin = 1.9 for the best possible packed bed column to around hmin = 1.0 for the microgroove array, while the interstitial velocity-based sepn. impedance Ei (a direct measure for the required anal. time) decreases from 1450-200. The next steps will focus on the removal of occasional particles remaining on the sides of the micro-pockets, the addn. of a cover substrate to seal the column and the subsequent conduction of actual chromatog. sepns.
- 9Zhang, X. A.; Chen, I.-T.; Chang, C.-H. Recent progress in near-field nanolithography using light interactions with colloidal particles: from nanospheres to three-dimensional nanostructures. Nanotechnology 2019, 30, 352002, DOI: 10.1088/1361-6528/ab2282Google Scholar9https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC1MXhsl2mtb7K&md5=bb43e31c09261cd8565644d4ab15e8dbRecent progress in near-field nanolithography using light interactions with colloidal particles: from nanospheres to three-dimensional nanostructuresZhang, Xu A.; Chen, I-Te; Chang, Chih-HaoNanotechnology (2019), 30 (35), 352002CODEN: NNOTER; ISSN:1361-6528. (IOP Publishing Ltd.)A review. The advance of nanotechnol. is firmly rooted in the development of cost-effective, versatile, and easily accessible nanofabrication techniques. The ability to pattern complex two-dimensional and three-dimensional nanostructured materials are particularly desirable, since they can have novel phys. properties that are not found in bulk materials. This review article will report recent progress in utilizing self-assembly of colloidal particles for nanolithog. In these techniques, the near-field interactions of light and colloids are the sole mechanisms employed to generate the intensity distributions for patterning. Based on both 'bottom-up' self-assembly and 'top-down' lithog. approaches, these processes are highly versatile and can take advantage of a no. of optical effects, allowing the complex 3D nanostructures to be patterned using single exposures. There are several key advantages including low equipment cost, facile structure design, and patterning scalability, which will be discussed in detail. We will outline the underlying optical effects, review the geometries that can be fabricated, discuss key limitations, and highlight potential applications in nanophotonics, optoelectronic devices, and nanoarchitectured materials.
- 10Lotito, V.; Zambelli, T. Approaches to self-assembly of colloidal monolayers: A guide for nanotechnologists. Adv. Colloid Interface Sci. 2017, 246, 217– 274, DOI: 10.1016/j.cis.2017.04.003Google Scholar10https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2sXhtVyrsbvF&md5=54ceacca4f11411c035d494279729703Approaches to self-assembly of colloidal monolayers: A guide for nanotechnologistsLotito, Valeria; Zambelli, TomasoAdvances in Colloid and Interface Science (2017), 246 (), 217-274CODEN: ACISB9; ISSN:0001-8686. (Elsevier B.V.)A review. Self-assembly of quasi-spherical colloidal particles in two-dimensional (2D) arrangements is essential for a wide range of applications from optoelectronics to surface engineering, from chem. and biol. sensing to light harvesting and environmental remediation. Several self-assembly approaches have flourished throughout the years, with specific features in terms of complexity of the implementation, sensitivity to process parameters, characteristics of the final colloidal assembly. Selecting the proper method for a given application amidst the vast literature in this field can be a challenging task. In this review, we present an extensive classification and comparison of the different techniques adopted for 2D self-assembly in order to provide useful guidelines for scientists approaching this field. After an overview of the main applications of 2D colloidal assemblies, we describe the main mechanisms underlying their formation and introduce the math. tools commonly used to analyze their final morphol. Subsequently, we examine in detail each class of self-assembly techniques, with an explanation of the phys. processes intervening in crystn. and a thorough investigation of the tech. peculiarities of the different practical implementations. We point out the specific characteristics of the set-ups and apparatuses developed for self-assembly in terms of complexity, requirements, reproducibility, robustness, sensitivity to process parameters and morphol. of the final colloidal pattern. Such an anal. will help the reader to individuate more easily the approach more suitable for a given application and will draw the attention towards the importance of the details of each implementation for the final results.
- 11Cai, Z.; Li, Z.; Ravaine, S.; He, M.; Song, Y.; Yin, Y.; Zheng, H.; Teng, J.; Zhang, A. From colloidal particles to photonic crystals: Advances in self-assembly and their emerging applications. Chem. Soc. Rev. 2021, 50, 5898– 5951, DOI: 10.1039/D0CS00706DGoogle Scholar11https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BB3MXovVamu74%253D&md5=bb34879823900019afeff1e63687ce34From colloidal particles to photonic crystals: advances in self-assembly and their emerging applicationsCai, Zhongyu; Li, Zhiwei; Ravaine, Serge; He, Mingxin; Song, Yanlin; Yin, Yadong; Zheng, Hanbin; Teng, Jinghua; Zhang, AoChemical Society Reviews (2021), 50 (10), 5898-5951CODEN: CSRVBR; ISSN:0306-0012. (Royal Society of Chemistry)A review. Over the last three decades, photonic crystals (PhCs) have attracted intense interests thanks to their broad potential applications in optics and photonics. Generally, these structures can be fabricated via either "top-down" lithog. or "bottom-up" self-assembly approaches. The self-assembly approaches have attracted particular attention due to their low cost, simple fabrication processes, relative convenience of scaling up, and the ease of creating complex structures with nanometer precision. The self-assembled colloidal crystals (CCs), which are good candidates for PhCs, have offered unprecedented opportunities for photonics, optics, optoelectronics, sensing, energy harvesting, environmental remediation, pigments, and many other applications. The creation of high-quality CCs and their mass fabrication over large areas are the crit. limiting factors for real-world applications. This paper reviews the state-of-the-art techniques in the self-assembly of colloidal particles for the fabrication of large-area high-quality CCs and CCs with unique symmetries. The first part of this review summarizes the types of defects commonly encountered in the fabrication process and their effects on the optical properties of the resultant CCs. Next, the mechanisms of the formation of cracks/defects are discussed, and a range of versatile fabrication methods to create large-area crack/defect-free two-dimensional and three-dimensional CCs are described. Meanwhile, we also shed light on both the advantages and limitations of these advanced approaches developed to fabricate high-quality CCs. The self-assembly routes and achievements in the fabrication of CCs with the ability to open a complete photonic bandgap, such as cubic diamond and pyrochlore structure CCs, are discussed as well. Then emerging applications of large-area high-quality CCs and unique photonic structures enabled by the advanced self-assembly methods are illustrated. At the end of this review, we outlook the future approaches in the fabrication of perfect CCs and highlight their novel real-world applications.
- 12Sotthewes, K.; Gardeniers, H. J.; Desmet, G.; Jimidar, I. S. Triboelectric charging of particles, an ongoing matter: From the early onset of planet formation to assembling crystals. ACS Omega 2022, 7, 41828– 41839, DOI: 10.1021/acsomega.2c05629Google Scholar12https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BB38Xis1ahur3F&md5=604e21b4af3d010d0d2262dd6312dcfaTriboelectric Charging of Particles, an Ongoing Matter: From the Early Onset of Planet Formation to Assembling CrystalsSotthewes, Kai; Gardeniers, Han J. G. E.; Desmet, Gert; Jimidar, Ignaas S. M.ACS Omega (2022), 7 (46), 41828-41839CODEN: ACSODF; ISSN:2470-1343. (American Chemical Society)A review. Triboelectrification is the spontaneous charging of two bodies when released from contact. Even though its manifestation is commonplace, in for instance triboelec. nanogenerators, scientists find the tribocharging mechanism a mystery. The primary aim of this mini-review is to provide an overview of different tribocharging concepts that have been applied to study and realize the formation of ordered stable structures using different objects on various length scales. Relevance spans from materials to planet formations. Esp., dry assembly methods of particles of different shapes based on tribocharging to obtain crystal structures or monolayers are considered. In addn., the current technol. employed to examine tribocharging in (semi)dry environments is discussed as well as the relevant forces playing a role in the assembly process. In brief, this mini-review is expected to provide a better understanding of tribocharging in assembling objects on the nano- and micrometer scales.
- 13Verloy, S.; Vankeerberghen, B.; Jimidar, I. S.; Gardeniers, H.; Desmet, G. Wafer-scale particle assembly in connected and isolated micromachined pockets via PDMS rubbing. Langmuir 2022, 38, 7709– 7719, DOI: 10.1021/acs.langmuir.2c00593Google Scholar13https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BB38XhtlOksLfJ&md5=f77d5a143a4112c3e5d10af0187a8d96Wafer-Scale Particle Assembly in Connected and Isolated Micromachined Pockets via PDMS RubbingVerloy, Sandrien; Vankeerberghen, Bert; Jimidar, Ignaas S. M.; Gardeniers, Han; Desmet, GertLangmuir (2022), 38 (25), 7709-7719CODEN: LANGD5; ISSN:0743-7463. (American Chemical Society)The present contribution reports on a study aiming to find the most suitable rubbing method for filling arrays of sepd. and interconnected micromachined pockets with individual microspheres on rigid, uncoated silicon substrates without breaking the particles or damaging the substrate. The explored dry rubbing methods generally yielded unsatisfactory results, marked by very large percentages of empty pockets and misplaced particles. On the other hand, the combination of wet rubbing with a patterned rubbing tool provided excellent results (typically <1% of empty pockets and <5% of misplaced particles). The wet method also did not leave any damage marks on the silicon substrate or the particles. When the pockets were aligned in linear grooves, markedly the best results were obtained when the ridge pattern of the rubbing tool was moved under a 45° angle with respect to the direction of the grooves. The method was tested for both silica and polystyrene particles. The proposed assembly method can be used in the prodn. of medical devices, antireflective coatings, and microfluidic devices with applications in chem. anal. and/or catalysis.
- 14Kraus, T.; Malaquin, L.; Delamarche, E.; Schmid, H.; Spencer, N. D.; Wolf, H. Closing the gap between self-assembly and microsystems using self-assembly, transfer, and integration of particles. Adv. Mater. 2005, 17, 2438– 2442, DOI: 10.1002/adma.200501171Google Scholar14https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD2MXhtFOqs7rN&md5=502260dcdbbe9789d3307c3afc1d0943Closing the gap between self-assembly and microsystems using self-assembly, transfer, and integration of particlesKraus, Tobias; Malaquin, Laurent; Delamarche, Emmanuel; Schmid, Heinz; Spencer, Nicholas D.; Wolf, HeikoAdvanced Materials (Weinheim, Germany) (2005), 17 (20), 2438-2442CODEN: ADVMEW; ISSN:0935-9648. (Wiley-VCH Verlag GmbH & Co. KGaA)Self-assembly, transfer, and integration of particles is achieved by combining self-assembly processes with an adhesion cascade. This process complements and enhances existing fabrication methods as it allows the integration of particles into planar devices. Moreover, it is versatile in terms of particle size and materials, and can create arbitrary particle arrangements with functional particle-substrate connections.
- 15Khanh, N. N.; Yoon, K. B. Facile organization of colloidal particles into large, perfect one-and two-dimensional arrays by dry manual assembly on patterned substrates. J. Am. Chem. Soc. 2009, 131, 14228– 14230, DOI: 10.1021/ja905534kGoogle Scholar15https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD1MXhtFKktbrJ&md5=b39af43075b6a9c3efd51626f39728a4Facile Organization of Colloidal Particles into Large, Perfect One- and Two-Dimensional Arrays by Dry Manual Assembly on Patterned SubstratesKhanh, Nguyen Nguyen; Yoon, Kyung ByungJournal of the American Chemical Society (2009), 131 (40), 14228-14230CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)The ability to rapidly and reproducibly assemble colloidal particles into large (>mm) one- (1D) and two-dimensional (2D) single crystals with perfect control of the particle networking pattern would open a new world rich with high quality novel materials, technologies, and sciences. However, current methods rely on self-assembly of colloidal particles in soln. (wet self-assembly), which intrinsically makes the assembly of the colloidal particles into defect-free large 1D and 2D single crystals difficult. We now demonstrate a new paradigm of colloidal particle organization into 1D and 2D single crystals, a process we call 'dry manual assembly on nanolithog. patterned substrates', which enables facile and rapid organization of colloidal particles in dry states into 1D and 2D single crystals in the centimeter or larger scales with a well-defined particle networking pattern. We believe that this novel methodol. will serve as a key to open a new era of particle organization.
- 16Koh, K.; Hwang, H.; Park, C.; Lee, J. Y.; Jeon, T. Y.; Kim, S.-H.; Kim, J. K.; Jeong, U. Large-Area Accurate Position Registry of Microparticles on Flexible, Stretchable Substrates Using Elastomer Templates. ACS Appl. Mater. Interfaces 2016, 8, 28149– 28158, DOI: 10.1021/acsami.6b08270Google Scholar16https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC28XhsFKmsL3O&md5=4fcb41d296bc48f0bc07dbc02bd42696Large-Area Accurate Position Registry of Microparticles on Flexible, Stretchable Substrates Using Elastomer TemplatesKoh, Kunsuk; Hwang, Hyejin; Park, Choojin; Lee, Jae Yong; Jeon, Tae Yoon; Kim, Shin-Hyun; Kim, Jin Kon; Jeong, UnyongACS Applied Materials & Interfaces (2016), 8 (41), 28149-28158CODEN: AAMICK; ISSN:1944-8244. (American Chemical Society)This work introduces a robust means for excellent position registry of microparticles via a forced assembly technique on flexible or stretchable substrates. It is based on the dry powder rubbing process which allows assembly of a microparticle monolayer in a short time without requiring any solvent or thermal treatment. Elastic phys. templates are used as substrates for the forced assembly in this study. Since the elastic templates can reduce the stress accumulation between the closely packed particles, they can minimize the defect formation in the particle assembly in large areas. The method can be used with powders comprising irregularly shaped particles with a relatively large size distribution that cannot be periodically ordered by conventional self-assembly. Furthermore, a non-closely packed particle array can be fabricated readily in large area, which is highly desirable for practical uses of the particle monolayers. The particle monolayers formed on the elastomer templates can be transferred to surfaces coated with thermoplastic block copolymers. Once transferred, the particle monolayers are flexible and stretchable over their entire surface. This work uses the particle monolayers on a large-area flexible substrate as photomasks to produce various photoresist patterns.
- 17Hwang, H.; Choi, S.-E.; Han, S. W.; You, I.; Jeong, E. S.; Kim, S.; Yang, H.; Lee, S.; Choo, J.; Kim, J. W. Cut-and-Paste Transferrable Pressure Sensing Cartridge Films. Chem. Mater. 2018, 30, 6410– 6419, DOI: 10.1021/acs.chemmater.8b02695Google Scholar17https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC1cXhs1Siur%252FK&md5=f047528a5e6ceffed8a35e00f7ea8e37Cut-and-Paste Transferrable Pressure Sensing Cartridge FilmsHwang, Hyejin; Choi, Song-Ee; Han, Sang Woo; You, Insang; Jeong, Eun Sook; Kim, Sinae; Yang, Hakyeong; Lee, Sangyeop; Choo, Jaebum; Kim, Jin Woong; Jeong, UnyongChemistry of Materials (2018), 30 (18), 6410-6419CODEN: CMATEX; ISSN:0897-4756. (American Chemical Society)Flexible tactile sensors have been intensively studied for healthcare and electronic skin devices. Currently, a sensing material, electrode, and substrate are manufd. as one set by depositing the sensing material on the electrode. For this reason, when another electrode or substrate is used in the sensor or when different sensor characteristics are required, a new sensing material must be developed and the fabrication conditions should be changed. This study proposes a novel method of manufg. a pressure sensing material like a cartridge film. The cartridge film is made by filling the holes of a stencil film (one MP in each hole) with conductive microparticles (MPs). Using the cartridge film, the sensing material can be cut-and-pasted on electrodes and transferred to other electrodes for reuse. This study analyzes the elec. responses of the sensors made of the cartridge film on the basis of the Hertzian contact theory, and also correlates the sensing performance of the sensors with the cond. of the MPs and the degree of protrusion of the MPs from the stencil surface.
- 18Wang, Y.; Wei, X. Y.; Kuang, S. Y.; Li, H. Y.; Chen, Y. H.; Liang, F.; Su, L.; Wang, Z. L.; Zhu, G. Triboelectrification-Induced Self-Assembly of Macro-Sized Polymer Beads on a Nanostructured Surface for Self-Powered Patterning. ACS Nano 2018, 12, 441– 447, DOI: 10.1021/acsnano.7b06758Google Scholar18https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC1cXjtFChtA%253D%253D&md5=0f611d4ee325f94a593dc98db0050495Triboelectrification-Induced Self-Assembly of Macro-Sized Polymer Beads on a Nanostructured Surface for Self-Powered PatterningWang, Ying; Wei, Xiao Yan; Kuang, Shuang Yang; Li, Hua Yang; Chen, Yang Hui; Liang, Fei; Su, Li; Wang, Zhong Lin; Zhu, GuangACS Nano (2018), 12 (1), 441-447CODEN: ANCAC3; ISSN:1936-0851. (American Chemical Society)Here we report an electrostatic-templated self-assembly (ETSA) method for arbitrarily patterning millimeter-sized polymer beads on a nanostructured surface without using an extra voltage source. A patterned electrode underneath an electrification layer generates "potential wells" of the corresponding pattern at predefined window sites, which capture and anchor the beads within the window sites by electrostatic force. Anal. calcn. is combined with numerical modeling to derive the electrostatic force acting on the beads, which is in great agreement with exptl. measured values. The generated pattern is solely detd. by the predefined underlying electrode, making it arbitrarily switchable by using different electrode patterns. By transferring the assembled beads into an elastomer matrix, possible applications of the ETSA in fabricating optical and flexible displays are demonstrated.
- 19Van Geite, W.; Jimidar, I. S.; Sotthewes, K.; Gardeniers, H.; Desmet, G. Vacuum-driven assembly of electrostatically levitated microspheres on perforated surfaces. Mater. Des. 2022, 216, 110573, DOI: 10.1016/j.matdes.2022.110573Google Scholar19https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BB38Xhtlanur3M&md5=bb96941276d2c0dc6573c3daaf852327Vacuum-driven assembly of electrostatically levitated microspheres on perforated surfacesVan Geite, Ward; Jimidar, Ignaas S. M.; Sotthewes, Kai; Gardeniers, Han; Desmet, GertMaterials & Design (2022), 216 (), 110573CODEN: MADSD2; ISSN:0264-1275. (Elsevier Ltd.)At the onset of a miniaturized device era, several promising methods, primarily wet methods, have been developed to attain large-scale assemblies of microparticles. To improve the speed, versatility and robustness of the current methods for the structured assembly of microparticles, an automatable method capable of forming 2D arrays of microspheres on large silicon surfaces is devised. The method uses surfaces perforated with vacuum-suction holes, capable of aspiring and holding individual particles from a particle cloud generated by subjecting a lump of chargeable particles, e.g., silica, polystyrene, and polymethyl methacrylate (PMMA), to a strong elec. field under ambient air conditions. The microsphere levitation depends on the elec. cond. and permittivity of the particles. A single or double brush stroke can remove excess particles covering the formed arrays. We find that silica or polystyrene microspheres with a diam. of 5μm or 10μm can be assembled on the order of a few seconds, independently of the array size. Owing to the reversible nature of the arresting vacuum force, the assembled layers can be transferred to another surface, such as polydimethylsiloxane (PDMS) sheets, thus providing a key step for future particle printing processes for the fabrication of hierarchical materials, e.g., photonic crystals.
- 20Van Geite, W.; Jimidar, I. S.; Gardeniers, H.; Desmet, G. Impact-induced generation of single airborne microspheres and the subsequent vacuum-driven assembly of ordered arrays. Powder Technol. 2023, 415, 118177, DOI: 10.1016/j.powtec.2022.118177Google Scholar20https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BB38Xjt1SntrrE&md5=d9980e7fb3687370356beb273b67ac82Impact-induced generation of single airborne microspheres and tsubsequent vacuum-driven assembly of ordered arraysVan Geite, Ward; Jimidar, Ignaas S. M.; Gardeniers, Han; Desmet, GertPowder Technology (2023), 415 (), 118177CODEN: POTEBX; ISSN:0032-5910. (Elsevier B.V.)A myriad of wet assembly techniques exists to attain ordered arrays of micro- and nanoparticles. The present contribution proposes a universal and rapid (in order of a few seconds) dry assembly strategy that can be employed to assemble ordered arrays of particles with a designed spacing. This method involves shooting agglomerated monodisperse silica, polystyrene or PMMA powder microspheres with diams. ranging between 5-10μm against an impact plating using pressure exceeding 2.5 bar. Consequently, the fluidized microspheres are attracted towards the pores of a silicon membrane device by applying a vacuum force. Furthermore, a brushing step is added to remove excess particles in undesired positions on top of the ordered arrays. An asset of the proposed method is that for the investigated particle properties, the same optimized conditions could be used to attain any desired 2-D particle arrangement that can be transferred on soft surfaces, e.g., PDMS.
- 21Dimitrov, A. S.; Miwa, T.; Nagayama, K. A comparison between the optical properties of amorphous and crystalline monolayers of silica particles. Langmuir 1999, 15, 5257– 5264, DOI: 10.1021/la990225rGoogle Scholar21https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADyaK1MXjvFSrt70%253D&md5=40b8f6369c76ce53e743d0e111625fc8A comparison between the optical properties of amorphous and crystalline monolayers of silica particlesDimitrov, Antony S.; Miwa, Tetsuya; Nagayama, KuniakiLangmuir (1999), 15 (16), 5257-5264CODEN: LANGD5; ISSN:0743-7463. (American Chemical Society)We compared optical properties of amorphous and cryst. monolayers formed from silica particles on glass substrates. The cryst. monolayers were grown from water suspensions by forming suspension wetting film on the glass surface and controlling the rate of the receding glass-suspension-air three-phase contact line. To form the amorphous monolayers, the particle powder was pressed toward the substrate and smeared by using a silicon rubber piece specially prepd. with flat and smooth surface. The field emission SEM observations showed particles of slightly varying diams. randomly distributed within the amorphous monolayer. The cryst. layers were built of differently sized domains of hexagonally packed particles. Illuminated by daylight and obsd. by using a low power optical microscope or the naked eye, the amorphous monolayers of particles between 200 and 500 nm in diam. looked softly colored and matted. The cryst. monolayers of 500 and 1000 nm in diam. exhibited enhanced sharpness of color and brilliancy at some observation angles. The amorphous and cryst. 100 nm particle monolayers exhibited similar antireflective properties. The difference in color appearance between amorphous and cryst. monolayers was exptl. verified by the corresponding reflectivity spectra.
- 22Iler, R. The adhesion of submicron silica particles on glass. J. Colloid Interface Sci. 1972, 38, 496– 501, DOI: 10.1016/0021-9797(72)90266-4Google Scholar22https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADyaE38Xns12rtg%253D%253D&md5=93258476e4599e24b2558c7af35a9939Adhesion of submircron silica particles on glassIler, R. K.Journal of Colloid and Interface Science (1972), 38 (2), 496-501CODEN: JCISA5; ISSN:0021-9797.A monolayer of individual particles of colloidal silica can be spread on glass by rubbing the surface with a powder made by drying a sol of uniform spherical particles under conditions minimizing cohesion between particles.
- 23Kang, K.; Choi, S.-E.; Jang, H. S.; Cho, W. K.; Nam, Y.; Choi, I. S.; Lee, J. S. In vitro developmental acceleration of hippocampal neurons on nanostructures of self-assembled silica beads in filopodium-size ranges. Angew. Chem., Int. Ed. 2012, 51, 2855– 2858, DOI: 10.1002/anie.201106271Google Scholar23https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC3MXhsFeqtL7I&md5=6d3ddbca4a0c763089f90d294507ebfbIn-Vitro Developmental Acceleration of Hippocampal Neurons on Nanostructures of Self-Assembled Silica Beads in Filopodium-Size RangesKang, Kyungtae; Choi, Sung-Eun; Jang, Hee Su; Cho, Woo Kyung; Nam, Yoonkey; Choi, Insung S.; Lee, Jin SeokAngewandte Chemie, International Edition (2012), 51 (12), 2855-2858, S2855/1-S2855/5CODEN: ACIEF5; ISSN:1433-7851. (Wiley-VCH Verlag GmbH & Co. KGaA)To understand the function of filopodia as an antenna for study of the neuronal environment, it is necessary to investigate the developmental responses of neurons to nanostructures, the feature size of which is comparable to that of filopodia (100-300 nm). Herein, we systematically varied the feature sizes of nanostructures by organizing spherical nanoparticles with different diams. on a glass substrate, and found that the neuritogenetic acceleration of hippocampal neurons occurred on the nanostructures the period of which was larger than 200 nm. For the generation of nanosurfaces with various feature sizes, silica beads with the diams. ranging from 100 to 700 nm were synthesized by hydrolysis of tetra-Et orthosilicate. We showed that the developmental acceleration of hippocampal neurons occurred on the well-packed structures of silica beads bigger than 200 nm in diam. The biochem. inhibition of filopodia formation suggested that neurons sensed nanotopogs. through filopodial activities, which in turn modulated intracellular cytoskeletal dynamics, just as they sense the biochem. cues. Our results also imply that nanotopog. cues are an important feature for guiding neurites during the neural developments in vivo. We believe that this work would provide fundamental but crucial information for studying nanotopog. manipulation of neuronal development, and also be useful for designing sophisticated neural interfaces in neural tissue engineering and others.
- 24Lee, J. S.; Kim, J. H.; Lee, Y. J.; Jeong, N. C.; Yoon, K. B. Manual assembly of microcrystal monolayers on substrates. Angew. Chem., Int. Ed. 2007, 46, 3087– 3090, DOI: 10.1002/anie.200604367Google Scholar24https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD2sXkvFKktrs%253D&md5=6a1f3615d1b60eccbfde3fcf8218a3a0Manual assembly of microcrystal monolayers on substratesLee, Jin Seok; Kim, Jae Hyun; Lee, Young Ju; Jeong, Nak Cheon; Yoon, Kyung ByungAngewandte Chemie, International Edition (2007), 46 (17), 3087-3090CODEN: ACIEF5; ISSN:1433-7851. (Wiley-VCH Verlag GmbH & Co. KGaA)Monolayers of mols. and nanoparticles should be prepd. on substrates only by self-assembly, but monolayers of microparticles can be produced by both self-assembly and direct manual attachment as if they are tiles. The quality of the monolayers is better when they are assembled by hand than by self-assembly.
- 25Park, C.; Lee, T.; Xia, Y.; Shin, T. J.; Myoung, J.; Jeong, U. Quick, Large-Area Assembly of a Single-Crystal Monolayer of Spherical Particles by Unidirectional Rubbing. Adv. Mater. 2014, 26, 4633– 4638, DOI: 10.1002/adma.201305875Google Scholar25https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2cXlvVSqtb4%253D&md5=cab6be32ac8141dd31cf22cccb54c35dQuick, Large-Area Assembly of a Single-Crystal Monolayer of Spherical Particles by Unidirectional RubbingPark, Choo Jin; Lee, Taeil; Xia, Younan; Shin, Tae Joo; Myoung, Jaemin; Jeong, UnyongAdvanced Materials (Weinheim, Germany) (2014), 26 (27), 4633-4638CODEN: ADVMEW; ISSN:0935-9648. (Wiley-VCH Verlag GmbH & Co. KGaA)This study introduces unidirectional rubbing of a dry powder of particles between two rubber plates as a quick and highly reproducible means of fabricating a single-crystal colloidal monolayer on a flat or curved substrate. The unidirectional rubbing of the particles described in this study introduces a quick, simple, inexpensive route to the assembly of spherical particles into a single-crystal monolayer on a flat or curved substrate. Under rubbing, the particles collectively roll along the rubbing direction so that the initial multiple grains merge to form a large single domain. The practical key variables for the monolayer assembly are the adhesion energy of the substrate, the rubbing speed, and the normal pressure. Optimum rubbing conditions for a single-crystal monolayer vary according to particle size, but in general, the following tenets apply: (i) the process is applicable to any rubber surface as long as the surface is not too sticky or too hard; (ii) submicrometer particles require high pressure and slow rubbing, whereas microparticles need low pressure and fast rubbing; and (iii) repeated unidirectional rubbing can minimize line defects.
- 26Park, C.; Koh, K.; Jeong, U. Structural color painting by rubbing particle powder. Sci. Rep. 2015, 5, 8340, DOI: 10.1038/srep08340Google Scholar26https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2MXhtFKjur%252FJ&md5=5c24e5aa1e3aae48220c78d51fc831f2Structural Color Painting by Rubbing Particle PowderPark, Choo Jin; Koh, Kunsuk; Jeong, UnyongScientific Reports (2015), 5 (), 8340CODEN: SRCEC3; ISSN:2045-2322. (Nature Publishing Group)Structural colors originate from purely phys. structures. Scientists have been inspired to mimic the structures found in nature, the realization of these structures still presents a great challenge. We have recently introduced unidirectional rubbing of a dry particle powder on a rubbery surface as a quick, highly reproducible means to fabricate a single crystal monolayer assembly of particles over an unlimited area. This study extends the particle-rubbing process to a novel fine-art painting, structural color painting (SCP). SCP is based on structural coloring with varying iridescence according to the crystal orientation, as controlled by the rubbing direction. This painting technique can be applied on curved surfaces, which enriches the objects to be painted and helps the painter mimic the structures found in nature. It also allows for quick fabrication of complicated particle-assembly patterns, which enables replication of paintings.
- 27Israelachvilli, J. Intermolecular and Surface Forces; Elsevier Pte Singapore, 2011.Google ScholarThere is no corresponding record for this reference.
- 28McCarty, L. S.; Winkleman, A.; Whitesides, G. M. Electrostatic self-assembly of polystyrene microspheres by using chemically directed contact electrification. Angew. Chem., Int. Ed. 2007, 46, 206– 209, DOI: 10.1002/anie.200602914Google Scholar28https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD2sXitlGitw%253D%253D&md5=42bf23a4bbd61aa911b44c3deaf5b861Electrostatic self-assembly of polystyrene microspheres by using chemically directed contact electrificationMcCarty, Logan S.; Winkleman, Adam; Whitesides, George M.Angewandte Chemie, International Edition (2007), 46 (1+2), 206-209CODEN: ACIEF5; ISSN:1433-7851. (Wiley-VCH Verlag GmbH & Co. KGaA)Electrostatic charges can be induced in functionalized polystyrene beads. Oppositely charged beads then aggregate to form superstructures. A coat of small beads can self-assemble around a large bead. After annealing, another layer of beads can be added. The technique, based on contact electrification, avoids the use of expensive equipment and enables the use of large quantities of material.
- 29Grzybowski, B. A.; Winkleman, A.; Wiles, J. A.; Brumer, Y.; Whitesides, G. M. Electrostatic self-assembly of macroscopic crystals using contact electrification. Nat. Mater. 2003, 2, 241– 245, DOI: 10.1038/nmat860Google Scholar29https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD3sXisFWgs78%253D&md5=6291995a48069dc57a36536f33b91a74Electrostatic self-assembly of macroscopic crystals using contact electrificationGrzybowski, Bartosz A.; Winkleman, Adam; Wiles, Jason A.; Brumer, Yisroel; Whitesides, George M.Nature Materials (2003), 2 (4), 241-245CODEN: NMAACR; ISSN:1476-1122. (Nature Publishing Group)Self-assembly of components larger than mols. into ordered arrays is an efficient way of prepg. microstructured materials with interesting mech. and optical properties. Although crystn. of identical particles or particles of different sizes or shapes can be readily achieved, the repertoire of methods to assemble binary lattices of particles of the same sizes but with different properties is very limited. This paper describes electrostatic self-assembly of two types of macroscopic components of identical dimensions using interactions that are generated by contact electrification. The systems we have examd. comprise two kinds of objects (usually spheres) made of different polymeric materials that charge with opposite elec. polarities when agitated on flat, metallic surfaces. The interplay of repulsive interactions between like-charged objects and attractive interactions between unlike-charged ones results in the self-assembly of these objects into highly ordered, closed arrays. Remarkably, some of the assemblies that form are not electroneutral, i.e., they possess a net charge. The authors suggest that the stability of these unusual structures can be explained by accounting for the interactions between elec. dipoles that the particles in the aggregates induce in their neighbors.
- 30Cademartiri, R.; Stan, C. A.; Tran, V. M.; Wu, E.; Friar, L.; Vulis, D.; Clark, L. W.; Tricard, S.; Whitesides, G. M. A simple two-dimensional model system to study electrostatic-self-assembly. Soft Matter 2012, 8, 9771– 9791, DOI: 10.1039/c2sm26192hGoogle Scholar30https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC38XhtlekurnP&md5=ffa6c6e798ad346da6e09d4825bb2817A simple two-dimensional model system to study electrostatic-self-assemblyCademartiri, Rebecca; Stan, Claudiu A.; Tran, Vivian M.; Wu, Evan; Friar, Liam; Vulis, Daryl; Clark, Logan W.; Tricard, Simon; Whitesides, George M.Soft Matter (2012), 8 (38), 9771-9791CODEN: SMOABF; ISSN:1744-683X. (Royal Society of Chemistry)This paper surveys the variables controlling the lattice structure and charge in macroscopic Coulombic crystals made from elec. charged, millimeter-sized polymer objects (spheres, cubes, and cylinders). Mech. agitation of these objects inside planar, bounded containers caused them to charge elec. through contact electrification, and to self-assemble. The processes of electrification and self-assembly, and the characteristics of the assemblies, depended on the type of motion used for agitation, on the type of materials used for the objects and the dish, on the size and shape of the objects and the dish, and on the no. of objects. Each of the three different materials in the system (of the dish and of the two types of spheres) influenced the electrification. Three classes of structures formed by self-assembly, depending on the exptl. conditions: two-dimensional lattices, one-dimensional chains, and zero-dimensional rosettes'. The lattices were characterized by their structure (disordered, square, rhombic, or hexagonal) and by the elec. charges of individual objects; the whole lattices were approx. elec. neutral. The lattices obsd. in this study were qual. different from ionic crystals; the charge of objects had practically continuous values which changed during agitation and self-assembly, and depended on exptl. conditions which included the lattice structure itself. The relationship between charge and structure led to the coexistence of regions with different lattice structures within the same assembly, and to transformations between different lattice structures during agitation.
- 31Battat, S.; Nagarkar, A. A.; Spaepen, F.; Weitz, D. A.; Whitesides, G. M. Kinetics of formation of a macroscale binary Coulombic material. Phys. Rev. Mater. 2023, 7, L040401, DOI: 10.1103/physrevmaterials.7.l040401Google Scholar31https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BB3sXhtVCrt77M&md5=d0421662af8a23e243e4d1f2ee30cd70Kinetics of formation of a macroscale binary Coulombic materialBattat, Sarah; Nagarkar, Amit A.; Spaepen, Frans; Weitz, David A.; Whitesides, George M.Physical Review Materials (2023), 7 (4), L040401CODEN: PRMHBS; ISSN:2475-9953. (American Physical Society)The electrostatic self-assembly of charged Brownian objects typically occurs in cases of short-range interactions. The objects form Coulombic materials that are close-packed and have long-range order. Here, we present a system in which two kinds of non-Brownian millimeter-sized beads tribocharge differently, experience long-range electrostatic interactions, and still form ordered two-dimensional structures. We provide a complete characterization of the kinetics of formation of these materials, as the total no. of beads is held const. and the relative no. of beads that tribocharge neg. or pos. is modified. We agitate the beads by shaking the dish in which they are contained. We show that the beads commonly adopt a transient structure that we call a rosette. A rosette consists of a central bead surrounded by six close-packed neighbors of a different kind. The symmetry of the final structure depends on the relative no. of neg. and pos. charged beads, and it is not necessarily the same as that of the transient structure. Our results bear important implications in the de novo design of Coulombic materials given our ability to isolate transient structures, identify the moment of their appearance, and quantify the impact of agitation, tribocharging, and Coulombic energy minimization on their persistence.
- 32Battat, S.; Weitz, D. A.; Whitesides, G. M. Melting of a macroscale binary Coulombic crystal. Soft Matter 2023, 19, 3190– 3198, DOI: 10.1039/D2SM01635DGoogle Scholar32https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BB3sXotVeitb0%253D&md5=f9033e26c7eefe3db8ee727cfb537c57Melting of a macroscale binary Coulombic crystalBattat, Sarah; Weitz, David A.; Whitesides, George M.Soft Matter (2023), 19 (17), 3190-3198CODEN: SMOABF; ISSN:1744-6848. (Royal Society of Chemistry)The question of melting has been addressed theor. and exptl. for two-dimensional crystals in thermal equil. However, as it pertains to out-of-equil. systems, the question is unresolved. Here, we present a platform to study the melting of a two-dimensional, binary Coulombic crystal composed of equal nos. of nylon and polytetrafluoroethylene (PTFE) beads that measure a couple of millimeters in diam. The beads are tribocharged-nylon pos. and PTFE neg.-and they experience long-range electrostatic interactions. They form a square crystal in which nylon and PTFE beads sit at alternating sites on a checkerboard lattice. We melt the crystal by agitating the dish in which it resides using an orbital shaker. We compare the melting behavior of the crystal without impurities to that of the crystal with impurities, where we use gold-coated nylon beads as impurities because they tribocharge negligibly. Our results reveal that impurities do not influence the melting of the crystal. Instead, the crystal undergoes shear-induced melting, beginning from its edges, due to its collisions with the dish. As a result of repetitive collisions, the beads acquire kinetic energy, undergo rearrangements, and become disordered. Unlike most examples of shear-induced melting, portions of the crystal remain locally ordered given the persistence of electrostatic interactions and the occurrence of some collisions that are favorable to ordering clusters of beads. Our work clarifies the melting behavior of sheared crystals whose constituents have persistent long-range interactions. It may prove valuable in detg. the conditions under which such materials are immune to disorder.
- 33Lacks, D. J.; Shinbrot, T. Long-standing and unresolved issues in triboelectric charging. Nat. Rev. Chem 2019, 3, 465, DOI: 10.1038/s41570-019-0115-1Google Scholar33https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC1MXhtlOgurfK&md5=5afd3ec73757da5986995b2ba4d9ff6dLong-standing and unresolved issues in triboelectric chargingLacks, Daniel J.; Shinbrot, TroyNature Reviews Chemistry (2019), 3 (8), 465-476CODEN: NRCAF7; ISSN:2397-3358. (Nature Research)A review. Static electrification is among the earliest of the sciences, well known to us all and with widespread and important consequences. Yet, its most basic foundations remain poorly understood. For example, after centuries of research, it is still not clear whether electrons, ions or even bulk material transfer is responsible for the obsd. charging. Recent work has leveraged the most advanced exptl. and theor. approaches, and has addressed the phenomenon from perspectives of quantum mechanics, surface chem., mechanochem. and statistical physics. While the resulting findings have advanced many aspects of our understanding, they have also led to the discovery of new surprises that we are only beginning to appreciate. This Review addresses both recent advances and their accompanying surprises.
- 34Jimidar, I. S.; Sotthewes, K.; Gardeniers, H.; Desmet, G. Spatial segregation of microspheres by rubbing-induced triboelectrification on patterned surfaces. Langmuir 2020, 36, 6793– 6800, DOI: 10.1021/acs.langmuir.0c00959Google Scholar34https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BB3cXhtVCrsLrM&md5=3959d0aa8770a2a9b1bb52165dd90c16Spatial Segregation of Microspheres by Rubbing-Induced Triboelectrification on Patterned SurfacesJimidar, Ignaas S. M.; Sotthewes, Kai; Gardeniers, Han; Desmet, GertLangmuir (2020), 36 (24), 6793-6800CODEN: LANGD5; ISSN:0743-7463. (American Chemical Society)Particle (monolayer) assembly is essential to various scientific and industrial applications, such as the fabrication of photonic crystals, optical sensors, and surface coatings. Several methods, including rubbing, have been developed for this purpose. Here, we report on the serendipitous observation that microparticles preferentially partition onto the fluorocarbon-coated parts of patterned silicon and borosilicate glass wafers when rubbed with poly(dimethylsiloxane) slabs. To explore the extent of this effect, we varied the geometry of the pattern, the substrate material, the ambient humidity, and the material and size of the particles. Partitioning coeffs. amounted up to a factor of 12 on silicon wafers and even ran in the 100s on borosilicate glass wafers at zero humidity. Using Kelvin probe force microscopy, the observations can be explained by triboelectrification, inducing a strong electrostatic attraction between the particles and the fluorocarbon zones, while the interaction with the noncoated zones is insignificant or even weakly repulsive.
- 35Butt, H.-J.; Kappl, M. Surface and Interfacial Forces; John Wiley & Sons, 2018.Google ScholarThere is no corresponding record for this reference.
- 36Serra, M.; Ferraro, D.; Pereiro, I.; Viovy, J.-L.; Descroix, S. The power of solid supports in multiphase and droplet-based microfluidics: towards clinical applications. Lab Chip 2017, 17, 3979– 3999, DOI: 10.1039/C7LC00582BGoogle Scholar36https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2sXhsV2ls7bM&md5=12fd1abf85695043ebe65b43e9bd1369The power of solid supports in multiphase and droplet-based microfluidics: towards clinical applicationsSerra, M.; Ferraro, D.; Pereiro, I.; Viovy, J.-L.; Descroix, S.Lab on a Chip (2017), 17 (23), 3979-3999CODEN: LCAHAM; ISSN:1473-0189. (Royal Society of Chemistry)A review. Multiphase and droplet microfluidic systems are growing in relevance in bioanal.-related fields, esp. due to the increased sensitivity, faster reaction times and lower sample/reagent consumption of many of its derived bioassays. Often applied to homogeneous (liq./liq.) reactions, innovative strategies for the implementation of heterogeneous (typically solid/liq.) processes have recently been proposed. These involve, for example, the extn. and purifn. of target analytes from complex matrixes or the implementation of multi-step protocols requiring efficient washing steps. To achieve this, solid supports such as functionalized particles (micro or nanometric) presenting different phys. properties (e.g. magnetic, optical or others) are used for the binding of specific entities. The manipulation of such supports with different microfluidic principles has both led to the miniaturization of existing biomedical protocols and the development of completely new strategies for diagnostics and research. In this review, multiphase and droplet-based microfluidic systems using solid suspensions are presented and discussed with a particular focus on: i) working principles and technol. developments of the manipulation strategies and ii) applications, critically discussing the level of maturity of these systems, which can range from initial proofs of concept to real clin. validations.
- 37Li, X.; Chen, L.; Ma, Y.; Weng, D.; Li, Z.; Song, L.; Zhang, X.; Yu, G.; Wang, J. Ultrafast Fabrication of Large-Area Colloidal Crystal Micropatterns via Self-Assembly and Transfer Printing. Adv. Funct. Mater. 2022, 32, 2205462, DOI: 10.1002/adfm.202205462Google Scholar37https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BB38XitVChsb7O&md5=c0ae27a2420e62a0009ebb9568730250Ultrafast Fabrication of Large-Area Colloidal Crystal Micropatterns via Self-Assembly and Transfer PrintingLi, Xuan; Chen, Lei; Ma, Yuan; Weng, Ding; Li, Zhaoxin; Song, Lele; Zhang, Xuanhe; Yu, Guoxu; Wang, JiadaoAdvanced Functional Materials (2022), 32 (45), 2205462CODEN: AFMDC6; ISSN:1616-301X. (Wiley-VCH Verlag GmbH & Co. KGaA)Colloidal crystals have brought the promise of revolution to modern engineering, yet commonly used fabrication technologies are still limited by the small prepn. area, time-consuming process, and dependence on sophisticated equipment. Here, a surface tension gradient-driven self-assembly strategy is proposed for the ultrafast fabrication of large-area colloidal crystals. The hydrogel loaded with sodium dodecyl sulfate is devised to construct a stable and continuous liq.-air interfacial tension gradient, and the resulting Marangoni effect can drive the micro-nano particles to instantaneously form (within several seconds) highly ordered colloidal crystals. Benefiting from the long range of surface tension gradients, the fabrication area of colloidal crystal films is demonstrated to exceed an astonishing 1000 cm2 without compromising their quality, showing great potential in scale-up manuf. Moreover, particles of a wide variety of sizes, materials, and functionalities can form close-packed self-assembly monolayers and be transferred to various substrates without damage, exhibiting great versatility. Inspired by ink microprinting, an ultrafast nanoparticle transfer printing method is further proposed to convert the close-packed nanoparticle monolayers into large-area conformal micropatterns with single-nanoparticle resoln. The great potential of nanoparticle micropatterns is demonstrated in flexible micro-electronics/skin electronics. This user-friendly, efficient self-assembly, and micropatterning strategy provide promising opportunities for academic and real industrial applications.
- 38Šutka, A.; Lapčinskis, L.; Verners, O.; Ģe̅rmane, L.; Smits, K.; Pludons, A.; Gaidukovs, S.; Jera̅ne, I.; Zubkins, M.; Pudzs, K. Bio-Inspired Macromolecular Ordering of Elastomers for Enhanced Contact Electrification and Triboelectric Energy Harvesting. Adv. Mater. Technol. 2022, 7, 2200162, DOI: 10.1002/admt.202200162Google Scholar38https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BB38XhtlSgsrzP&md5=dec751246a50b040b5cc41244d729c1eBio-Inspired Macromolecular Ordering of Elastomers for Enhanced Contact Electrification and Triboelectric Energy HarvestingSutka, Andris; Lapcinskis, Linards; Verners, Osvalds; Germane, Liva; Smits, Krisjanis; Pludons, Arturs; Gaidukovs, Sergejs; Jerane, Ilze; Zubkins, Martins; Pudzs, Kaspars; Sherrell, Peter Cameron; Blums, JurisAdvanced Materials Technologies (Weinheim, Germany) (2022), 7 (10), 2200162CODEN: AMTDCM; ISSN:2365-709X. (Wiley-VCH Verlag GmbH & Co. KGaA)Triboelectrification of polymers enables mech. energy harvesting in triboelec. generators, droplet generators, and ferroelectrets. Herein, triboelec. polymers, inspired by the ordering in spider-silk, with strongly enhanced contact electrification are presented. The ordering in polyether block amide (PEBA) is induced by the addn. of inorg. goethite (α-FeOOH) nanowires that form H-bonds with the elastomeric matrix. The addn. of as little as 0.1 vol% of α-FeOOH into PEBA increases the surface charge by more than order of magnitude (from 0.069 to 0.93 nC cm-2). The H-bonds between α-FeOOH and PEBA promote the formation of inclusions with higher degree of macromol. ordering, analogous to the structure of spider silk. The formation of these inclusions is proven via nanoindentation hardness measurements and correlated with H-bond-induced chem. changes by Fourier transform IR spectroscopy and direct scanning calorimetry. Theor. studies reveal that the irregularity in hardness provides stress accumulation on the polymer surface during contact-sepn. Subsequent mol. dynamic studies demonstrate that stress accumulation promotes the mass-transfer mechanism of contact electrification. The proposed macromol. structure design provides a new paradigm for developing materials for applications in mech. energy harvesting.
- 39Jimidar, I. S.; Sotthewes, K.; Gardeniers, H.; Desmet, G.; van der Meer, D. Self-organization of agitated microspheres on various substrates. Soft Matter 2022, 18, 3660– 3677, DOI: 10.1039/D2SM00432AGoogle Scholar39https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BB38XhtFGnsLvK&md5=f15d9d34a33024a4a1eef549aa6e73a9Self-organization of agitated microspheres on various substratesJimidar, Ignaas S. M.; Sotthewes, Kai; Gardeniers, Han; Desmet, Gert; van der Meer, DevarajSoft Matter (2022), 18 (19), 3660-3677CODEN: SMOABF; ISSN:1744-6848. (Royal Society of Chemistry)The vibration dynamics of relatively large granular grains is extensively treated in the literature, but comparable studies on the self-assembly of smaller agitated beads are lacking. In this work, we investigate how the particle properties and the properties of the underlying substrate surface affect the dynamics and self-organization of horizontally agitated monodisperse microspheres with diams. between 3 and 10μm. Upon agitation, the agglomerated hydrophilic silica particles locally leave traces of particle monolayers as they move across the flat uncoated and fluorocarbon-coated silicon substrates. However, on the micromachined silicon tray with relatively large surface roughness, the agitated silica agglomerates form segregated bands reminiscent of earlier studies on granular suspensions or Faraday heaps. On the other hand, the less agglomerated hydrophobic polystyrene particles form densely occupied monolayer arrangements regardless of the underlying substrate. We explain the observations by considering the relevant adhesion and friction forces between particles and underlying substrates as well as those among the particles themselves. Interestingly, for both types of microspheres, large areas of the fluorocarbon-coated substrates are covered with densely occupied particle monolayers. By qual. examg. the morphol. of the self-organized particle monolayers using the Voronoi approach, it is understood that these monolayers are highly disordered, i.e., multiple symmetries coexist in the self-organized monolayers. However, more structured symmetries are identified in the monolayers of the agitated polystyrene microspheres on all the substrates, albeit not all precisely positioned on a hexagonal lattice. On the other hand, both the silica and polystyrene monolayers on the bare silicon substrates transition into less disordered structures as time progresses. Using Kelvin probe force microscopy measurements, we show that due to the tribocharging phenomenon, the formation of particle monolayers is promoted on the fluorocarbon surface, i.e., a local electrostatic attraction exists between the particle and the substrate.
- 40Jimidar, I. S.; Kwiecinski, W.; Roozendaal, G.; Kooij, E. S.; Gardeniers, H. J.; Desmet, G.; Sotthewes, K. Influence of Wettability and Geometry on Contact Electrification between Nonionic Insulators. ACS Appl. Mater. Interfaces 2023, 15, 42004– 42014, DOI: 10.1021/acsami.3c05729Google Scholar40https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BB3sXhtlCms7bJ&md5=16433f2640b53f669320aafe3458b8b2Influence of Wettability and Geometry on Contact Electrification between Nonionic InsulatorsJimidar, Ignaas S. M.; Kwiecinski, Wojciech; Roozendaal, Gijs; Kooij, E. Stefan; Gardeniers, Han J. G. E.; Desmet, Gert; Sotthewes, KaiACS Applied Materials & Interfaces (2023), 15 (35), 42004-42014CODEN: AAMICK; ISSN:1944-8244. (American Chemical Society)Contact electrification is an interfacial process in which two surfaces exchange elec. charges when they are in contact with one another. Consequently, the surfaces may gain opposite polarity, inducing an electrostatic attraction. Therefore, this principle can be exploited to generate electricity, which has been precisely done in triboelec. nanogenerators (TENGs) over the last decades. The details of the underlying mechanisms are still ill-understood, esp. the influence of relative humidity (RH). Using the colloidal probe technique, we convincingly show that water plays an important role in the charge exchange process when two distinct insulators with different wettability are contacted and sepd. in <1 s at ambient conditions. The charging process is faster, and more charge is acquired with increasing relative humidity, also beyond RH = 40% (at which TENGs have their max. power generation), due to the geometrical asymmetry (curved colloid surface vs planar substrate) introduced in the system. In addn., the charging time const. is detd., which is found to decrease with increasing relative humidity. Altogether, the current study adds to our understanding of how humidity levels affect the charging process between two solid surfaces, which is even enhanced up to RH = 90% as long as the curved surface is hydrophilic, paving the way for designing novel and more efficient TENGs, eco-energy harvesting devices which utilize water and solid charge interaction mechanism, self-powered sensors, and tribotronics.
- 41Jones, R.; Pollock, H. M.; Cleaver, J. A.; Hodges, C. S. Adhesion forces between glass and silicon surfaces in air studied by AFM: Effects of relative humidity, particle size, roughness, and surface treatment. Langmuir 2002, 18, 8045– 8055, DOI: 10.1021/la0259196Google Scholar41https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD38XmvFKrtrg%253D&md5=7dc74369cff7aeddb2909f165a875510Adhesion Forces between Glass and Silicon Surfaces in Air Studied by AFM: Effects of Relative Humidity, Particle Size, Roughness, and Surface TreatmentJones, Robert; Pollock, Hubert M.; Cleaver, Jamie A. S.; Hodges, Christopher S.Langmuir (2002), 18 (21), 8045-8055CODEN: LANGD5; ISSN:0743-7463. (American Chemical Society)Using the at. force microscope (AFM), the pull-off forces between flat glass or Si surfaces and Si AFM tips or glass microspheres of different sizes were extensively studied as a function of relative humidity (RH) in the range 5-90%, as model systems for the behavior of cohesive powders. The glass and Si substrates were treated to render them either hydrophobic or hydrophilic. All the hydrophilic surfaces gave simple force curves and pull-off forces increasing uniformly with RH. Small contacts (R ∼ 20 nm) gave pull-off forces close to values predicted by simple Laplace-Kelvin theory (∼20 nN), but the values with microspheres (R ∼ 20 μm) fell well below predictions for sphere-flat or sphere-sphere geometry, due to roughness and asperity contacts. The hydrophobic Si surfaces also exhibited simple behavior, with no significant RH dependence. The pull-off force again fell well below predicted values (Johnson-Kendall-Roberts contact mechanics theory) for the larger contacts. Hydrophobic glass gave similar adhesion to Si over most of the RH range, but against both Si tips and glass microspheres, there was an anomalously large adhesion in the RH range 20-40%, accompanied by a long-range noncontact force. The adhesion on fully hydrophilic surfaces and its RH dependence can be mostly explained by current theories of capillary bridges, but the interpretation is complicated by the sensitivity of theor. predictions to contact geometry (and hence to roughness effects) and by uncertainties in the thickness of adsorbed H2O layers. The anomalous behavior on hydrophobic glass surfaces at intermediate values of RH is not fully understood, but possible causes are (1) dipole layers in the partially formed H2O film, giving rise to patch charges and long-range forces, or (2) fixed charges at a reactive glass surface, involving specific bonding reactions. The results may be useful in explaining the behavior of cohesive powders with different coatings or those which show a large humidity dependence (e.g., zeolites) or show electrostatic charging effects (e.g., SiO2 aerogels).
- 42Preud’homme, N.; Lumay, G.; Vandewalle, N.; Opsomer, E. Tribocharging of granular materials and influence on their flow. Soft Matter 2023, 19, 8911– 8918, DOI: 10.1039/D3SM01322GGoogle Scholar42https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BB3sXitlGisLbM&md5=06a46570b078f4385af7fa978ac8d2fbTribocharging of granular materials and influence on their flowPreud'homme, Nicolas; Lumay, Geoffroy; Vandewalle, Nicolas; Opsomer, EricSoft Matter (2023), 19 (45), 8911-8918CODEN: SMOABF; ISSN:1744-6848. (Royal Society of Chemistry)Once granular materials flow, particles charge because of the triboelec. effect. When particles touch each other, charges are exchanged during contact whether they are made of the same material or not. Surprisingly, when different sizes of particles are mixed together, large particles tend to charge pos. while small particles charge neg. If the particles are relatively small (typically smaller than a millimeter), the electrostatic interaction between the particles becomes significant and leads to aggregation or sticking on the surface of the container holding them. Studying those effects is challenging as the mechanisms that govern the triboelec. effect are not fully understood yet. We show that the patch model (or mosaic model) is suitable to reproduce numerically the flow of triboelec. charged granular materials as the specific charging of bi-disperse granular materials can be retrieved. We investigate the influence of charging on the cohesion of granular materials and highlight the relevant parameters related to the patch model that influence cohesion. Our results shed new light on the mechanisms of the triboelec. effect as well as on how the charging of granular materials influences cohesion using numerical simulations.
- 43Lacks, D. J.; Mohan Sankaran, R. Contact electrification of insulating materials. J. Phys. D: Appl. Phys. 2011, 44, 453001, DOI: 10.1088/0022-3727/44/45/453001Google Scholar43https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC3MXhsFSltb3N&md5=55f4fe8577c6d9d38b759fd3df49d572Contact electrification of insulating materialsLacks, Daniel J.; Sankaran, R. MohanJournal of Physics D: Applied Physics (2011), 44 (45), 453001/1-453001/15CODEN: JPAPBE; ISSN:0022-3727. (Institute of Physics Publishing)A review. The electrostatic charge that is generated when two materials are contacted or rubbed and then sepd. is a well-known phys. process that has been studied for more than 2500 years. Contact electrification occurs in many contexts, both natural and technol. For example, in dust storms the collisions between particles lead to electrostatic charging and in extreme cases, extraordinary lightning displays. In electrophotog., toner particles are intentionally charged to guide their deposition in well-defined patterns. Despite such a long history and so many important consequences, a fundamental understanding of the mechanism behind contact electrification remains elusive. An open question is what type of species are transferred between the surfaces to generate charge-expts. suggest various species ranging from electrons to ions to nanoscopic bits of material, and theor. work suggests that non-equil. states may play an important role. Another open question is the contact electrification that occurs when two insulating materials with identical phys. properties touch-since there is no apparent driving force, it is not clear why charge transfer occurs. A third open question involves granular systems-models and expts. have shown that a particle-size dependence for the charging often exists. In this review, we discuss the fundamental aspects of contact electrification and highlight recent research efforts aimed at understanding these open questions.
- 44Lotito, V.; Zambelli, T. Pattern detection in colloidal assembly: A mosaic of analysis techniques. Adv. Colloid Interface Sci. 2020, 284, 102252, DOI: 10.1016/j.cis.2020.102252Google Scholar44https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BB3cXhvVOmurfF&md5=8931cd33d363c3615cad011cf583a749Pattern detection in colloidal assembly: A mosaic of analysis techniquesLotito, Valeria; Zambelli, TomasoAdvances in Colloid and Interface Science (2020), 284 (), 102252CODEN: ACISB9; ISSN:0001-8686. (Elsevier B.V.)A review. In addn., casting light on the structures formed by colloidal particles can help to get better insight into colloidal interactions and understand phase transitions. Finally, the growing interest in colloidal assemblies in materials science for practical applications going from optoelectronics to biosensing imposes a thorough characterization of the morphol. of colloidal assemblies because of the intimate relationship between morphol. and phys. properties (e.g. optical and mech.) of a material. Several image anal. techniques developed to investigate images (acquired via SEM, digital video microscopy and other imaging methods) provide variegated and complementary information on the colloidal structures under scrutiny. However, understanding how to use such image anal. tools to get information on the characteristics of the colloidal assemblies may represent a non-trivial task, because it requires the combination of approaches drawn from diverse disciplines such as image processing, computational geometry and computational topol. and their application to a primarily physico-chem. process. In this review we provide a methodical and extensive description of real-space image anal. tools by explaining their principles and their application to the investigation of two-dimensional colloidal assemblies with different morphol. characteristics.
- 45López-González, F.; Pacheco-Vázquez, F.; Donado, F. Ordering of a granular layer of cubes under strain-induced shear and vibration. Phys. A 2023, 620, 128768, DOI: 10.1016/j.physa.2023.128768Google ScholarThere is no corresponding record for this reference.
- 46Šutka, A.; Lapčinskis, L.; He, D.; Kim, H.; Berry, J. D.; Bai, J.; Knite, M.; Ellis, A. V.; Jeong, C. K.; Sherrell, P. C. Engineering Polymer Interfaces: A Review toward Controlling Triboelectric Surface Charge. Adv. Mater. Interfaces 2023, 10, 2300323, DOI: 10.1002/admi.202300323Google Scholar46https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BB3sXhsF2msbvL&md5=5d5f70235290cb2eecde9b3ab371445eEngineering Polymer Interfaces: A Review toward Controlling Triboelectric Surface ChargeSutka, Andris; Lapcinskis, Linards; He, Delong; Kim, Hyunseung; Berry, Joseph D.; Bai, Jinbo; Knite, Maris; Ellis, Amanda V.; Jeong, Chang Kyu; Sherrell, Peter C.Advanced Materials Interfaces (2023), 10 (26), 2300323CODEN: AMIDD2; ISSN:2196-7350. (Wiley-VCH Verlag GmbH & Co. KGaA)A review. Contact electrification and triboelec. charging are areas of intense research. Despite their low ability to accept or donate electrons, polymer insulator based triboelec. nanogenerators have emerged as highly efficient mech.-to-elec. conversion devices. Here, it is reviewed the structure-property-performance of polymer insulators in triboelec. nanogenerators and focus on tools that can be used to directly enhance charge generation, via altering a polymer's mech., thermal, chem., and topog. properties. In addn. to the discussion of these fundamental properties, the use of additives to locally manipulate the polymer surface structure is discussed. The link between each property and the underlying charging mechanism is discussed, in the context of both increasing surface charge and predicting the polarity of surface charge, and pathways to engineer triboelec. charging are highlighted. Key questions facing the field surrounding data reporting, the role of water, and synergy between mass, electron, and ion transfer mechanisms are highlighted with aspirational goals of a holistic model for triboelec. charging proposed.
- 47Verners, O.; Lapčinskis, L.; Sherrell, P. C.; Šutka, A. Contact Electrification at Dielectric Polymer Interfaces: On Bond Scission, Material Transfer, and Electron Transfer. Adv. Mater. Interfaces 2023, 10, 2300562, DOI: 10.1002/admi.202300562Google Scholar47https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BB3sXhvFyrurvO&md5=fcd1136039732b10965ee559119e9c21Contact Electrification at Dielectric Polymer Interfaces: On Bond Scission, Material Transfer, and Electron TransferVerners, Osvalds; Lapcinskis, Linards; Sherrell, Peter C.; Sutka, AndrisAdvanced Materials Interfaces (2023), 10 (36), 2300562CODEN: AMIDD2; ISSN:2196-7350. (Wiley-VCH Verlag GmbH & Co. KGaA)Triboelec. nanogenerators (TENGs) are revolutionizing mech.-to-elec. energy harvesting. TENGs harvest energy through the polymer-polymer contact electrification (PCE) mechanism, driven by nanoscale processes at the contact interface. Currently, when discussing PCE there are two distinct schools of thought on which nanoscale interactions drive charging at the contact interface; (1) electron transfer, where orbital overlap leads to charge tunneling between polymers; or (2) mass (material) transfer, where polymer chain entanglement and intermol. bonding leads to heterolytic bond scission. Here, a combination of in silico and benchtop expts. is used to elucidate the relative role of electron and mass transfer in PCE. In silico expts. show that covalent bond scission in a polymethylmethacrylate/polytetrafluoroethylene system occurs at 348 kcal mol-1, prior to electron cloud overlap, where the HOMO and LUMO of the system remain sepd. by 163 kcal mol-1. Benchtop expts. show PCE-generated charges cannot be simply discharged via elec. grounding, indicating the formation of bound surface charge from mass transfer. The calcns. and contact-electrification tests provide strong evidence to support mass transfer being the leading mechanism driving PCE.
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Abstract
Figure 1
Figure 1. (a) Schematic illustration of the manual rubbing technique to assemble dry powder into closely packed crystal (HCP) structures on substrates using a PDMS (rubber) stamp; inset shows the iridescence structures observed of a 3 μm PMMA monolayer on a fluorocarbon coating on a Au-coated substrate under illumination (scale bar: 2 cm). SEM images of the uniformly fluorocarbon-coated silicon substrate covered with a monolayer of 10 μm (b) PMMA and (c) silica microspheres rubbed under standard lab conditions (RH = 40–55%) and (d) silica microspheres rubbed under zero-humidity glovebox conditions (RH = 0%). (e) Average normalized shape factors ϑnorm of the monolayers obtained on various substrates under standard lab conditions (RH = 40–55%; N = 40). (f) Average normalized shape factors ϑnorm of the monolayers obtained under zero-humidity glovebox conditions (N2-controlled environment) and standard lab conditions [RH = 40–55% (data taken from Figure 1e); N = 40]. Scale bar, green: 50 μm.
Figure 2
Figure 2. Results of the KPFM measurement performed on the (a) 500 nm SiO2 substrate before (pristine) and after rubbing the PMMA microspheres using a PDMS stamp. Inset (a) shows the topographic image (7 × 7 μm2, scale bar: 1 μm) of the SiO2 substrate. (b) Topographic (25 × 25 μm2, scale bar: 6 μm) and (c) simultaneously obtained surface potential map (25 × 25 μm2, scale bar: 6 μm) of the 10 μm PMMA microspheres after the rubbing experiment.
Figure 3
Figure 3. (a) Average normalized shape factor ϑnorm,av of the 10 μm PMMA microsphere results obtained on the fluorocarbon-coated samples (N = 40) using three different stamps: pristine PDMS, PDMS wrapped in aluminum foil, and PDMS covered with a (PEBA)/α-FeOOH layer performed under ambient lab conditions (RH = 40–55%). (b) Force–distance curves of a silica colloidal probe on three different stamps obtained using the colloidal probe technique performed with the AFM. Inset (b) displays a silica colloidal probe with a diameter of 10 μm.
Figure 4
Figure 4. SEM images of HCP crystal structures obtained from 3 μm (a) PMMA powder and (b) polystyrene microspheres and 500 nm (c) PMMA powder and (d) silica powder (inside the glovebox) obtained after rubbing experiments were performed using a PDMS stamp on mainly fluorocarbon-coated substrates. Only experiment (b) was performed on a Au-coated substrate. Scale bar: green = 15 μm; white = 3 μm.
Figure 5
Figure 5. (a) Large area of tunable 2D crystal structures on a 4 in. fluorocarbon-coated patterned 8 μm SiO2 wafer after 3 μm PMMA powder was rubbed and subsequently pressurized air of 4–5 bar was laterally blown across the wafer (cf. Figures S9–S11). SEM images of patterned HCP crystal structures obtained using (b,c) 10 μm and (d,e) 3 μm PMMA powder microspheres on the same 8 μm SiO2 patterned wafer. The experiments were performed under ambient lab conditions (RH = 40–55%). Scale bar: green = 7 mm; black = 100 μm.
References
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- 2Schockmel, J.; Mersch, E.; Vandewalle, N.; Lumay, G. Melting of a confined monolayer of magnetized beads. Phys. Rev. E 2013, 87, 062201, DOI: 10.1103/PhysRevE.87.0622012https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC3sXhtFOqtr3K&md5=46b85ebbb7b35d96f446f64d694b3a9aMelting of a confined monolayer of magnetized beadsSchockmel, J.; Mersch, E.; Vandewalle, N.; Lumay, G.Physical Review E: Statistical, Nonlinear, and Soft Matter Physics (2013), 87 (6-A), 062201/1-062201/7CODEN: PRESCM; ISSN:1539-3755. (American Physical Society)We present an exptl. model system to study two-dimensional phase transitions. This system is composed of a monolayer of millimetric beads interacting through shor range magnetic dipole-dipole interactions. As the system is athermal, a mech. agitation is used to produce an erratic motion of the beads. The two-dimensional melting scenario predicted by the Kosterlitz-Thouless-Halperin-Nelson-Young theory is obsd. Each phase (liq.-hexatic-solid) has been highlighted with the use of both static and dynamic order parameters. Translational and orientational order are, resp., estd. through the pair correlation function g(r) and both orientational correlation function g6(r) and its temporal counterpart g6(t). We observe two transitions by tuning the applied magnetic field H. First, a loss of translational order without loss of orientational order is obsd. This is the signature of the transition from the solid phase to the so-called "hexatic" phase. Finally, the orientational order disappears, leading to a liquidlike structure.
- 3Vogel, N.; Retsch, M.; Fustin, C.-A.; del Campo, A.; Jonas, U. Advances in colloidal assembly: the design of structure and hierarchy in two and three dimensions. Chem. Rev. 2015, 115, 6265– 6311, DOI: 10.1021/cr400081d3https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2MXhtVKisb%252FI&md5=adcad128eeb6237084b51a884589cf38Advances in Colloidal Assembly: The Design of Structure and Hierarchy in Two and Three DimensionsVogel, Nicolas; Retsch, Markus; Fustin, Charles-Andre; del Campo, Aranzazu; Jonas, UlrichChemical Reviews (Washington, DC, United States) (2015), 115 (13), 6265-6311CODEN: CHREAY; ISSN:0009-2665. (American Chemical Society)A review. Colloidal self-assembly methods are discussed. The methods are divided into two major sections, two-dimensional and three-dimensional assemblies organized at a supporting surface. Each section introduces simple assembly methods and proceeds with increasing complexity of the structural hierarchies.
- 4Díaz-Marín, C. D.; Li, D.; Vázquez-Cosme, F. J.; Pajovic, S.; Cha, H.; Song, Y.; Kilpatrick, C.; Vaartstra, G.; Wilson, C. T.; Boriskina, S. Capillary Transfer of Self-Assembled Colloidal Crystals. Nano Lett. 2023, 23, 1888– 1896, DOI: 10.1021/acs.nanolett.2c048964https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BB3sXjtlOjurw%253D&md5=b3e727523acbd6d8abbdba09eb265f0aCapillary Transfer of Self-Assembled Colloidal CrystalsDiaz-Marin, Carlos D.; Li, Diane; Vazquez-Cosme, Fernando J.; Pajovic, Simo; Cha, Hyeongyun; Song, Youngsup; Kilpatrick, Cameron; Vaartstra, Geoffrey; Wilson, Chad T.; Boriskina, Svetlana; Wang, Evelyn N.Nano Letters (2023), 23 (5), 1888-1896CODEN: NALEFD; ISSN:1530-6984. (American Chemical Society)Colloidal self-assembly has attracted significant interest in numerous applications including optics, electrochem., thermofluidics, and biomol. templating. To meet the requirements of these applications, numerous fabrication methods have been developed. However, these are limited to narrow ranges of feature sizes, are incompatible with many substrates, and/or have low scalability, significantly limiting the use of colloidal self-assembly. In this work, we study the capillary transfer of colloidal crystals and demonstrate that this approach overcomes these limitations. Enabled by capillary transfer, we fabricate 2D colloidal crystals with nano/micro feature sizes spanning 2 orders of magnitude and on typically challenging substrates including those that are hydrophobic, rough, curved, or structured with microchannels. We developed and systemically validated a capillary peeling model, elucidating the underlying transfer physics. Due to its high versatility, good quality, and simplicity, this approach can expand the possibilities of colloidal self-assembly and enhance the performance of applications using colloidal crystals.
- 5Pan, R.; Zhang, W.; Cheng, H.; Yang, J.; Gong, Y.; Hu, R.; Zhuo, Y.; Ding, J.; Zhang, X.; Chen, L. Capillary Self-Assembly Register Microspheres to Fabricate Anisotropic Conductive Film Used for Ultra-Fine Pitch Stable Electrical Interfacing Interconnection. Adv. Mater. Technol. 2023, 8, 2300514, DOI: 10.1002/admt.2023005145https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BB3sXhsF2mt7zI&md5=55f734b38831905bc50339ffa11672a7Capillary Self-Assembly Register Microspheres to Fabricate Anisotropic Conductive Film Used for Ultra-Fine Pitch Stable Electrical Interfacing InterconnectionPan, Rui; Zhang, Wei; Cheng, Hua; Yang, Jihua; Gong, Yi; Hu, Rui; Zhuo, Yizhi; Ding, Jianjun; Zhang, Xian; Chen, Lin; Tian, XingyouAdvanced Materials Technologies (Weinheim, Germany) (2023), 8 (18), 2300514CODEN: AMTDCM; ISSN:2365-709X. (Wiley-VCH Verlag GmbH & Co. KGaA)The trend to integrate more electronic components in a limited space range motivates the development of advanced electronic packaging. Conventional electronic packaging is difficult to perform in stable interfacing interconnection pitch below 7 μm due to the possibility of short-circuit problems. Herein, a kind of anisotropic conductive film (μ-ACF) contg. periodically arranged conductive microspheres for microscale pitch elec. interfacing interconnection is developed. The periodic arrangement can avert the contact of conductive microspheres, thus enabling stable interconnection with a pitch as small as 5 μm. By coating conductive microspheres with a layer of silicon insulation, the pitch can be further reduced to 3 μm, which can prevent the formation of conductive pathways between electrodes even if they come into contact with each other. Such high-quality arrangement is achieved by lithog. and capillary self-assembly method, which is expected to be used in high-throughput prodn. Thanks to the delicate design, the μ-ACF can achieve a low contact resistance of 4.62 mΩ mm-2 and a spatial resoln. of 3 μm without short-circuit failure. The spatial resoln. can be further improved by adjusting the size of conductive microspheres, which is conducive to the development of highly integrated devices.
- 6Hwang, H.; Jeong, U. Microparticle-Based Soft Electronic Devices: Toward One-Particle/One-Pixel. Adv. Funct. Mater. 2019, 30, 1901810, DOI: 10.1002/adfm.201901810There is no corresponding record for this reference.
- 7Song, C.; Ye, B.; Xu, J.; Chen, J.; Shi, W.; Yu, C.; An, C.; Zhu, J.; Zhang, W. Large-Area Nanosphere Self-Assembly Monolayers for Periodic Surface Nanostructures with Ultrasensitive and Spatially Uniform SERS Sensing. Small 2022, 18, 2104202, DOI: 10.1002/smll.2021042027https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BB3MXislyjtLfJ&md5=4ea070111abd18ae210ae42b5743b6a4Large-Area Nanosphere Self-Assembly Monolayers for Periodic Surface Nanostructures with Ultrasensitive and Spatially Uniform SERS SensingSong, Changkun; Ye, Baoyun; Xu, Jianyong; Chen, Junhong; Shi, Wei; Yu, Chunpei; An, Chongwei; Zhu, Junwu; Zhang, WenchaoSmall (2022), 18 (8), 2104202CODEN: SMALBC; ISSN:1613-6810. (Wiley-VCH Verlag GmbH & Co. KGaA)Colloidal lithog. provides a rapid and low-cost approach to construct 2D periodic surface nanostructures. However, an impressive demonstration to prep. large-area colloidal template is still missing. Here, a high-efficient and flexible technique is proposed to fabricate self-assembly monolayers consisting of orderly-packed polystyrene spheres at air/water interface via ultrasonic spray. This "non-contact" technique exhibits great advantages in terms of scalability and adaptability due to its renitent interface dynamic balance. More importantly, this technique is not only competent for self-assembly of single-sized polystyrene spheres, but also for binary polystyrene spheres, completely reversing the current hard situation of prepg. large-area self-assembly monolayers. As a representative application, hexagonal-packed silver-coated silicon nanorods array (Si-NRs@Ag) is developed as an ultrasensitive surface-enhanced Raman scattering (SERS) substrate with very low limit-of-detection for selective detection of explosive 2,4,6-trinitrotoluene down to femtomolar (10-14M) range. The periodicity and orderliness of the array allow hot spots to be designed and constructed in a homogeneous fashion, resulting in an incomparable uniformity and reproducibility of Raman signals. All these excellent properties come from the Si-NRs@Ag substrate based on the ordered structure, open surface, and wide-range elec. field, providing a robust, consistent, and tunable platform for mol. trapping and SERS sensing for a wide range of org. mols.
- 8Vankeerberghen, B.; Verloy, S.; Jimidar, I. S.; Gardeniers, H.; Desmet, G. Structured microgroove columns as a potential solution to obtain perfectly ordered particle beds. J. Chromatogr. A 2023, 1700, 464031, DOI: 10.1016/j.chroma.2023.4640318https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BB3sXptlWmtb0%253D&md5=a63a418b68f3d08917fa4ab9f3130668Structured microgroove columns as a potential solution to obtain perfectly ordered particle bedsVankeerberghen, Bert; Verloy, Sandrien; Jimidar, Ignaas S. M.; Gardeniers, Han; Desmet, GertJournal of Chromatography A (2023), 1700 (), 464031CODEN: JCRAEY; ISSN:0021-9673. (Elsevier B.V.)A novel concept is reported to produce ordered beds of spherical particles in a suitable format for liq. chromatog. In this concept, spherical particles are either positioned individually (single-layer column) or stacked (multi-layer column) in micromachined pockets that form an interconnected array of micro-grooves acting as a perfectly ordered chromatog. column. As a first step towards realizing this concept, the breakthrough is reported that is realized by obtaining a soln. to uniformly fill the micro-groove arrays with spherical particles. This can be achieved in a few sweeps using a dedicated rubbing approach wherein a particle suspension is manually rubbed over a silicon chip. In addn., numerical calcns. of the dispersion in the newly introduced column format have been carried out and demonstrate the combined advantage of order and reduced flow resistance the newly proposed concept has over the conventional packed bed. For fully-porous particles and a zone retention factor of k'' = 2, the hmin decreases from hmin = 1.9 for the best possible packed bed column to around hmin = 1.0 for the microgroove array, while the interstitial velocity-based sepn. impedance Ei (a direct measure for the required anal. time) decreases from 1450-200. The next steps will focus on the removal of occasional particles remaining on the sides of the micro-pockets, the addn. of a cover substrate to seal the column and the subsequent conduction of actual chromatog. sepns.
- 9Zhang, X. A.; Chen, I.-T.; Chang, C.-H. Recent progress in near-field nanolithography using light interactions with colloidal particles: from nanospheres to three-dimensional nanostructures. Nanotechnology 2019, 30, 352002, DOI: 10.1088/1361-6528/ab22829https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC1MXhsl2mtb7K&md5=bb43e31c09261cd8565644d4ab15e8dbRecent progress in near-field nanolithography using light interactions with colloidal particles: from nanospheres to three-dimensional nanostructuresZhang, Xu A.; Chen, I-Te; Chang, Chih-HaoNanotechnology (2019), 30 (35), 352002CODEN: NNOTER; ISSN:1361-6528. (IOP Publishing Ltd.)A review. The advance of nanotechnol. is firmly rooted in the development of cost-effective, versatile, and easily accessible nanofabrication techniques. The ability to pattern complex two-dimensional and three-dimensional nanostructured materials are particularly desirable, since they can have novel phys. properties that are not found in bulk materials. This review article will report recent progress in utilizing self-assembly of colloidal particles for nanolithog. In these techniques, the near-field interactions of light and colloids are the sole mechanisms employed to generate the intensity distributions for patterning. Based on both 'bottom-up' self-assembly and 'top-down' lithog. approaches, these processes are highly versatile and can take advantage of a no. of optical effects, allowing the complex 3D nanostructures to be patterned using single exposures. There are several key advantages including low equipment cost, facile structure design, and patterning scalability, which will be discussed in detail. We will outline the underlying optical effects, review the geometries that can be fabricated, discuss key limitations, and highlight potential applications in nanophotonics, optoelectronic devices, and nanoarchitectured materials.
- 10Lotito, V.; Zambelli, T. Approaches to self-assembly of colloidal monolayers: A guide for nanotechnologists. Adv. Colloid Interface Sci. 2017, 246, 217– 274, DOI: 10.1016/j.cis.2017.04.00310https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2sXhtVyrsbvF&md5=54ceacca4f11411c035d494279729703Approaches to self-assembly of colloidal monolayers: A guide for nanotechnologistsLotito, Valeria; Zambelli, TomasoAdvances in Colloid and Interface Science (2017), 246 (), 217-274CODEN: ACISB9; ISSN:0001-8686. (Elsevier B.V.)A review. Self-assembly of quasi-spherical colloidal particles in two-dimensional (2D) arrangements is essential for a wide range of applications from optoelectronics to surface engineering, from chem. and biol. sensing to light harvesting and environmental remediation. Several self-assembly approaches have flourished throughout the years, with specific features in terms of complexity of the implementation, sensitivity to process parameters, characteristics of the final colloidal assembly. Selecting the proper method for a given application amidst the vast literature in this field can be a challenging task. In this review, we present an extensive classification and comparison of the different techniques adopted for 2D self-assembly in order to provide useful guidelines for scientists approaching this field. After an overview of the main applications of 2D colloidal assemblies, we describe the main mechanisms underlying their formation and introduce the math. tools commonly used to analyze their final morphol. Subsequently, we examine in detail each class of self-assembly techniques, with an explanation of the phys. processes intervening in crystn. and a thorough investigation of the tech. peculiarities of the different practical implementations. We point out the specific characteristics of the set-ups and apparatuses developed for self-assembly in terms of complexity, requirements, reproducibility, robustness, sensitivity to process parameters and morphol. of the final colloidal pattern. Such an anal. will help the reader to individuate more easily the approach more suitable for a given application and will draw the attention towards the importance of the details of each implementation for the final results.
- 11Cai, Z.; Li, Z.; Ravaine, S.; He, M.; Song, Y.; Yin, Y.; Zheng, H.; Teng, J.; Zhang, A. From colloidal particles to photonic crystals: Advances in self-assembly and their emerging applications. Chem. Soc. Rev. 2021, 50, 5898– 5951, DOI: 10.1039/D0CS00706D11https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BB3MXovVamu74%253D&md5=bb34879823900019afeff1e63687ce34From colloidal particles to photonic crystals: advances in self-assembly and their emerging applicationsCai, Zhongyu; Li, Zhiwei; Ravaine, Serge; He, Mingxin; Song, Yanlin; Yin, Yadong; Zheng, Hanbin; Teng, Jinghua; Zhang, AoChemical Society Reviews (2021), 50 (10), 5898-5951CODEN: CSRVBR; ISSN:0306-0012. (Royal Society of Chemistry)A review. Over the last three decades, photonic crystals (PhCs) have attracted intense interests thanks to their broad potential applications in optics and photonics. Generally, these structures can be fabricated via either "top-down" lithog. or "bottom-up" self-assembly approaches. The self-assembly approaches have attracted particular attention due to their low cost, simple fabrication processes, relative convenience of scaling up, and the ease of creating complex structures with nanometer precision. The self-assembled colloidal crystals (CCs), which are good candidates for PhCs, have offered unprecedented opportunities for photonics, optics, optoelectronics, sensing, energy harvesting, environmental remediation, pigments, and many other applications. The creation of high-quality CCs and their mass fabrication over large areas are the crit. limiting factors for real-world applications. This paper reviews the state-of-the-art techniques in the self-assembly of colloidal particles for the fabrication of large-area high-quality CCs and CCs with unique symmetries. The first part of this review summarizes the types of defects commonly encountered in the fabrication process and their effects on the optical properties of the resultant CCs. Next, the mechanisms of the formation of cracks/defects are discussed, and a range of versatile fabrication methods to create large-area crack/defect-free two-dimensional and three-dimensional CCs are described. Meanwhile, we also shed light on both the advantages and limitations of these advanced approaches developed to fabricate high-quality CCs. The self-assembly routes and achievements in the fabrication of CCs with the ability to open a complete photonic bandgap, such as cubic diamond and pyrochlore structure CCs, are discussed as well. Then emerging applications of large-area high-quality CCs and unique photonic structures enabled by the advanced self-assembly methods are illustrated. At the end of this review, we outlook the future approaches in the fabrication of perfect CCs and highlight their novel real-world applications.
- 12Sotthewes, K.; Gardeniers, H. J.; Desmet, G.; Jimidar, I. S. Triboelectric charging of particles, an ongoing matter: From the early onset of planet formation to assembling crystals. ACS Omega 2022, 7, 41828– 41839, DOI: 10.1021/acsomega.2c0562912https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BB38Xis1ahur3F&md5=604e21b4af3d010d0d2262dd6312dcfaTriboelectric Charging of Particles, an Ongoing Matter: From the Early Onset of Planet Formation to Assembling CrystalsSotthewes, Kai; Gardeniers, Han J. G. E.; Desmet, Gert; Jimidar, Ignaas S. M.ACS Omega (2022), 7 (46), 41828-41839CODEN: ACSODF; ISSN:2470-1343. (American Chemical Society)A review. Triboelectrification is the spontaneous charging of two bodies when released from contact. Even though its manifestation is commonplace, in for instance triboelec. nanogenerators, scientists find the tribocharging mechanism a mystery. The primary aim of this mini-review is to provide an overview of different tribocharging concepts that have been applied to study and realize the formation of ordered stable structures using different objects on various length scales. Relevance spans from materials to planet formations. Esp., dry assembly methods of particles of different shapes based on tribocharging to obtain crystal structures or monolayers are considered. In addn., the current technol. employed to examine tribocharging in (semi)dry environments is discussed as well as the relevant forces playing a role in the assembly process. In brief, this mini-review is expected to provide a better understanding of tribocharging in assembling objects on the nano- and micrometer scales.
- 13Verloy, S.; Vankeerberghen, B.; Jimidar, I. S.; Gardeniers, H.; Desmet, G. Wafer-scale particle assembly in connected and isolated micromachined pockets via PDMS rubbing. Langmuir 2022, 38, 7709– 7719, DOI: 10.1021/acs.langmuir.2c0059313https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BB38XhtlOksLfJ&md5=f77d5a143a4112c3e5d10af0187a8d96Wafer-Scale Particle Assembly in Connected and Isolated Micromachined Pockets via PDMS RubbingVerloy, Sandrien; Vankeerberghen, Bert; Jimidar, Ignaas S. M.; Gardeniers, Han; Desmet, GertLangmuir (2022), 38 (25), 7709-7719CODEN: LANGD5; ISSN:0743-7463. (American Chemical Society)The present contribution reports on a study aiming to find the most suitable rubbing method for filling arrays of sepd. and interconnected micromachined pockets with individual microspheres on rigid, uncoated silicon substrates without breaking the particles or damaging the substrate. The explored dry rubbing methods generally yielded unsatisfactory results, marked by very large percentages of empty pockets and misplaced particles. On the other hand, the combination of wet rubbing with a patterned rubbing tool provided excellent results (typically <1% of empty pockets and <5% of misplaced particles). The wet method also did not leave any damage marks on the silicon substrate or the particles. When the pockets were aligned in linear grooves, markedly the best results were obtained when the ridge pattern of the rubbing tool was moved under a 45° angle with respect to the direction of the grooves. The method was tested for both silica and polystyrene particles. The proposed assembly method can be used in the prodn. of medical devices, antireflective coatings, and microfluidic devices with applications in chem. anal. and/or catalysis.
- 14Kraus, T.; Malaquin, L.; Delamarche, E.; Schmid, H.; Spencer, N. D.; Wolf, H. Closing the gap between self-assembly and microsystems using self-assembly, transfer, and integration of particles. Adv. Mater. 2005, 17, 2438– 2442, DOI: 10.1002/adma.20050117114https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD2MXhtFOqs7rN&md5=502260dcdbbe9789d3307c3afc1d0943Closing the gap between self-assembly and microsystems using self-assembly, transfer, and integration of particlesKraus, Tobias; Malaquin, Laurent; Delamarche, Emmanuel; Schmid, Heinz; Spencer, Nicholas D.; Wolf, HeikoAdvanced Materials (Weinheim, Germany) (2005), 17 (20), 2438-2442CODEN: ADVMEW; ISSN:0935-9648. (Wiley-VCH Verlag GmbH & Co. KGaA)Self-assembly, transfer, and integration of particles is achieved by combining self-assembly processes with an adhesion cascade. This process complements and enhances existing fabrication methods as it allows the integration of particles into planar devices. Moreover, it is versatile in terms of particle size and materials, and can create arbitrary particle arrangements with functional particle-substrate connections.
- 15Khanh, N. N.; Yoon, K. B. Facile organization of colloidal particles into large, perfect one-and two-dimensional arrays by dry manual assembly on patterned substrates. J. Am. Chem. Soc. 2009, 131, 14228– 14230, DOI: 10.1021/ja905534k15https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD1MXhtFKktbrJ&md5=b39af43075b6a9c3efd51626f39728a4Facile Organization of Colloidal Particles into Large, Perfect One- and Two-Dimensional Arrays by Dry Manual Assembly on Patterned SubstratesKhanh, Nguyen Nguyen; Yoon, Kyung ByungJournal of the American Chemical Society (2009), 131 (40), 14228-14230CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)The ability to rapidly and reproducibly assemble colloidal particles into large (>mm) one- (1D) and two-dimensional (2D) single crystals with perfect control of the particle networking pattern would open a new world rich with high quality novel materials, technologies, and sciences. However, current methods rely on self-assembly of colloidal particles in soln. (wet self-assembly), which intrinsically makes the assembly of the colloidal particles into defect-free large 1D and 2D single crystals difficult. We now demonstrate a new paradigm of colloidal particle organization into 1D and 2D single crystals, a process we call 'dry manual assembly on nanolithog. patterned substrates', which enables facile and rapid organization of colloidal particles in dry states into 1D and 2D single crystals in the centimeter or larger scales with a well-defined particle networking pattern. We believe that this novel methodol. will serve as a key to open a new era of particle organization.
- 16Koh, K.; Hwang, H.; Park, C.; Lee, J. Y.; Jeon, T. Y.; Kim, S.-H.; Kim, J. K.; Jeong, U. Large-Area Accurate Position Registry of Microparticles on Flexible, Stretchable Substrates Using Elastomer Templates. ACS Appl. Mater. Interfaces 2016, 8, 28149– 28158, DOI: 10.1021/acsami.6b0827016https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC28XhsFKmsL3O&md5=4fcb41d296bc48f0bc07dbc02bd42696Large-Area Accurate Position Registry of Microparticles on Flexible, Stretchable Substrates Using Elastomer TemplatesKoh, Kunsuk; Hwang, Hyejin; Park, Choojin; Lee, Jae Yong; Jeon, Tae Yoon; Kim, Shin-Hyun; Kim, Jin Kon; Jeong, UnyongACS Applied Materials & Interfaces (2016), 8 (41), 28149-28158CODEN: AAMICK; ISSN:1944-8244. (American Chemical Society)This work introduces a robust means for excellent position registry of microparticles via a forced assembly technique on flexible or stretchable substrates. It is based on the dry powder rubbing process which allows assembly of a microparticle monolayer in a short time without requiring any solvent or thermal treatment. Elastic phys. templates are used as substrates for the forced assembly in this study. Since the elastic templates can reduce the stress accumulation between the closely packed particles, they can minimize the defect formation in the particle assembly in large areas. The method can be used with powders comprising irregularly shaped particles with a relatively large size distribution that cannot be periodically ordered by conventional self-assembly. Furthermore, a non-closely packed particle array can be fabricated readily in large area, which is highly desirable for practical uses of the particle monolayers. The particle monolayers formed on the elastomer templates can be transferred to surfaces coated with thermoplastic block copolymers. Once transferred, the particle monolayers are flexible and stretchable over their entire surface. This work uses the particle monolayers on a large-area flexible substrate as photomasks to produce various photoresist patterns.
- 17Hwang, H.; Choi, S.-E.; Han, S. W.; You, I.; Jeong, E. S.; Kim, S.; Yang, H.; Lee, S.; Choo, J.; Kim, J. W. Cut-and-Paste Transferrable Pressure Sensing Cartridge Films. Chem. Mater. 2018, 30, 6410– 6419, DOI: 10.1021/acs.chemmater.8b0269517https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC1cXhs1Siur%252FK&md5=f047528a5e6ceffed8a35e00f7ea8e37Cut-and-Paste Transferrable Pressure Sensing Cartridge FilmsHwang, Hyejin; Choi, Song-Ee; Han, Sang Woo; You, Insang; Jeong, Eun Sook; Kim, Sinae; Yang, Hakyeong; Lee, Sangyeop; Choo, Jaebum; Kim, Jin Woong; Jeong, UnyongChemistry of Materials (2018), 30 (18), 6410-6419CODEN: CMATEX; ISSN:0897-4756. (American Chemical Society)Flexible tactile sensors have been intensively studied for healthcare and electronic skin devices. Currently, a sensing material, electrode, and substrate are manufd. as one set by depositing the sensing material on the electrode. For this reason, when another electrode or substrate is used in the sensor or when different sensor characteristics are required, a new sensing material must be developed and the fabrication conditions should be changed. This study proposes a novel method of manufg. a pressure sensing material like a cartridge film. The cartridge film is made by filling the holes of a stencil film (one MP in each hole) with conductive microparticles (MPs). Using the cartridge film, the sensing material can be cut-and-pasted on electrodes and transferred to other electrodes for reuse. This study analyzes the elec. responses of the sensors made of the cartridge film on the basis of the Hertzian contact theory, and also correlates the sensing performance of the sensors with the cond. of the MPs and the degree of protrusion of the MPs from the stencil surface.
- 18Wang, Y.; Wei, X. Y.; Kuang, S. Y.; Li, H. Y.; Chen, Y. H.; Liang, F.; Su, L.; Wang, Z. L.; Zhu, G. Triboelectrification-Induced Self-Assembly of Macro-Sized Polymer Beads on a Nanostructured Surface for Self-Powered Patterning. ACS Nano 2018, 12, 441– 447, DOI: 10.1021/acsnano.7b0675818https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC1cXjtFChtA%253D%253D&md5=0f611d4ee325f94a593dc98db0050495Triboelectrification-Induced Self-Assembly of Macro-Sized Polymer Beads on a Nanostructured Surface for Self-Powered PatterningWang, Ying; Wei, Xiao Yan; Kuang, Shuang Yang; Li, Hua Yang; Chen, Yang Hui; Liang, Fei; Su, Li; Wang, Zhong Lin; Zhu, GuangACS Nano (2018), 12 (1), 441-447CODEN: ANCAC3; ISSN:1936-0851. (American Chemical Society)Here we report an electrostatic-templated self-assembly (ETSA) method for arbitrarily patterning millimeter-sized polymer beads on a nanostructured surface without using an extra voltage source. A patterned electrode underneath an electrification layer generates "potential wells" of the corresponding pattern at predefined window sites, which capture and anchor the beads within the window sites by electrostatic force. Anal. calcn. is combined with numerical modeling to derive the electrostatic force acting on the beads, which is in great agreement with exptl. measured values. The generated pattern is solely detd. by the predefined underlying electrode, making it arbitrarily switchable by using different electrode patterns. By transferring the assembled beads into an elastomer matrix, possible applications of the ETSA in fabricating optical and flexible displays are demonstrated.
- 19Van Geite, W.; Jimidar, I. S.; Sotthewes, K.; Gardeniers, H.; Desmet, G. Vacuum-driven assembly of electrostatically levitated microspheres on perforated surfaces. Mater. Des. 2022, 216, 110573, DOI: 10.1016/j.matdes.2022.11057319https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BB38Xhtlanur3M&md5=bb96941276d2c0dc6573c3daaf852327Vacuum-driven assembly of electrostatically levitated microspheres on perforated surfacesVan Geite, Ward; Jimidar, Ignaas S. M.; Sotthewes, Kai; Gardeniers, Han; Desmet, GertMaterials & Design (2022), 216 (), 110573CODEN: MADSD2; ISSN:0264-1275. (Elsevier Ltd.)At the onset of a miniaturized device era, several promising methods, primarily wet methods, have been developed to attain large-scale assemblies of microparticles. To improve the speed, versatility and robustness of the current methods for the structured assembly of microparticles, an automatable method capable of forming 2D arrays of microspheres on large silicon surfaces is devised. The method uses surfaces perforated with vacuum-suction holes, capable of aspiring and holding individual particles from a particle cloud generated by subjecting a lump of chargeable particles, e.g., silica, polystyrene, and polymethyl methacrylate (PMMA), to a strong elec. field under ambient air conditions. The microsphere levitation depends on the elec. cond. and permittivity of the particles. A single or double brush stroke can remove excess particles covering the formed arrays. We find that silica or polystyrene microspheres with a diam. of 5μm or 10μm can be assembled on the order of a few seconds, independently of the array size. Owing to the reversible nature of the arresting vacuum force, the assembled layers can be transferred to another surface, such as polydimethylsiloxane (PDMS) sheets, thus providing a key step for future particle printing processes for the fabrication of hierarchical materials, e.g., photonic crystals.
- 20Van Geite, W.; Jimidar, I. S.; Gardeniers, H.; Desmet, G. Impact-induced generation of single airborne microspheres and the subsequent vacuum-driven assembly of ordered arrays. Powder Technol. 2023, 415, 118177, DOI: 10.1016/j.powtec.2022.11817720https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BB38Xjt1SntrrE&md5=d9980e7fb3687370356beb273b67ac82Impact-induced generation of single airborne microspheres and tsubsequent vacuum-driven assembly of ordered arraysVan Geite, Ward; Jimidar, Ignaas S. M.; Gardeniers, Han; Desmet, GertPowder Technology (2023), 415 (), 118177CODEN: POTEBX; ISSN:0032-5910. (Elsevier B.V.)A myriad of wet assembly techniques exists to attain ordered arrays of micro- and nanoparticles. The present contribution proposes a universal and rapid (in order of a few seconds) dry assembly strategy that can be employed to assemble ordered arrays of particles with a designed spacing. This method involves shooting agglomerated monodisperse silica, polystyrene or PMMA powder microspheres with diams. ranging between 5-10μm against an impact plating using pressure exceeding 2.5 bar. Consequently, the fluidized microspheres are attracted towards the pores of a silicon membrane device by applying a vacuum force. Furthermore, a brushing step is added to remove excess particles in undesired positions on top of the ordered arrays. An asset of the proposed method is that for the investigated particle properties, the same optimized conditions could be used to attain any desired 2-D particle arrangement that can be transferred on soft surfaces, e.g., PDMS.
- 21Dimitrov, A. S.; Miwa, T.; Nagayama, K. A comparison between the optical properties of amorphous and crystalline monolayers of silica particles. Langmuir 1999, 15, 5257– 5264, DOI: 10.1021/la990225r21https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADyaK1MXjvFSrt70%253D&md5=40b8f6369c76ce53e743d0e111625fc8A comparison between the optical properties of amorphous and crystalline monolayers of silica particlesDimitrov, Antony S.; Miwa, Tetsuya; Nagayama, KuniakiLangmuir (1999), 15 (16), 5257-5264CODEN: LANGD5; ISSN:0743-7463. (American Chemical Society)We compared optical properties of amorphous and cryst. monolayers formed from silica particles on glass substrates. The cryst. monolayers were grown from water suspensions by forming suspension wetting film on the glass surface and controlling the rate of the receding glass-suspension-air three-phase contact line. To form the amorphous monolayers, the particle powder was pressed toward the substrate and smeared by using a silicon rubber piece specially prepd. with flat and smooth surface. The field emission SEM observations showed particles of slightly varying diams. randomly distributed within the amorphous monolayer. The cryst. layers were built of differently sized domains of hexagonally packed particles. Illuminated by daylight and obsd. by using a low power optical microscope or the naked eye, the amorphous monolayers of particles between 200 and 500 nm in diam. looked softly colored and matted. The cryst. monolayers of 500 and 1000 nm in diam. exhibited enhanced sharpness of color and brilliancy at some observation angles. The amorphous and cryst. 100 nm particle monolayers exhibited similar antireflective properties. The difference in color appearance between amorphous and cryst. monolayers was exptl. verified by the corresponding reflectivity spectra.
- 22Iler, R. The adhesion of submicron silica particles on glass. J. Colloid Interface Sci. 1972, 38, 496– 501, DOI: 10.1016/0021-9797(72)90266-422https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADyaE38Xns12rtg%253D%253D&md5=93258476e4599e24b2558c7af35a9939Adhesion of submircron silica particles on glassIler, R. K.Journal of Colloid and Interface Science (1972), 38 (2), 496-501CODEN: JCISA5; ISSN:0021-9797.A monolayer of individual particles of colloidal silica can be spread on glass by rubbing the surface with a powder made by drying a sol of uniform spherical particles under conditions minimizing cohesion between particles.
- 23Kang, K.; Choi, S.-E.; Jang, H. S.; Cho, W. K.; Nam, Y.; Choi, I. S.; Lee, J. S. In vitro developmental acceleration of hippocampal neurons on nanostructures of self-assembled silica beads in filopodium-size ranges. Angew. Chem., Int. Ed. 2012, 51, 2855– 2858, DOI: 10.1002/anie.20110627123https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC3MXhsFeqtL7I&md5=6d3ddbca4a0c763089f90d294507ebfbIn-Vitro Developmental Acceleration of Hippocampal Neurons on Nanostructures of Self-Assembled Silica Beads in Filopodium-Size RangesKang, Kyungtae; Choi, Sung-Eun; Jang, Hee Su; Cho, Woo Kyung; Nam, Yoonkey; Choi, Insung S.; Lee, Jin SeokAngewandte Chemie, International Edition (2012), 51 (12), 2855-2858, S2855/1-S2855/5CODEN: ACIEF5; ISSN:1433-7851. (Wiley-VCH Verlag GmbH & Co. KGaA)To understand the function of filopodia as an antenna for study of the neuronal environment, it is necessary to investigate the developmental responses of neurons to nanostructures, the feature size of which is comparable to that of filopodia (100-300 nm). Herein, we systematically varied the feature sizes of nanostructures by organizing spherical nanoparticles with different diams. on a glass substrate, and found that the neuritogenetic acceleration of hippocampal neurons occurred on the nanostructures the period of which was larger than 200 nm. For the generation of nanosurfaces with various feature sizes, silica beads with the diams. ranging from 100 to 700 nm were synthesized by hydrolysis of tetra-Et orthosilicate. We showed that the developmental acceleration of hippocampal neurons occurred on the well-packed structures of silica beads bigger than 200 nm in diam. The biochem. inhibition of filopodia formation suggested that neurons sensed nanotopogs. through filopodial activities, which in turn modulated intracellular cytoskeletal dynamics, just as they sense the biochem. cues. Our results also imply that nanotopog. cues are an important feature for guiding neurites during the neural developments in vivo. We believe that this work would provide fundamental but crucial information for studying nanotopog. manipulation of neuronal development, and also be useful for designing sophisticated neural interfaces in neural tissue engineering and others.
- 24Lee, J. S.; Kim, J. H.; Lee, Y. J.; Jeong, N. C.; Yoon, K. B. Manual assembly of microcrystal monolayers on substrates. Angew. Chem., Int. Ed. 2007, 46, 3087– 3090, DOI: 10.1002/anie.20060436724https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD2sXkvFKktrs%253D&md5=6a1f3615d1b60eccbfde3fcf8218a3a0Manual assembly of microcrystal monolayers on substratesLee, Jin Seok; Kim, Jae Hyun; Lee, Young Ju; Jeong, Nak Cheon; Yoon, Kyung ByungAngewandte Chemie, International Edition (2007), 46 (17), 3087-3090CODEN: ACIEF5; ISSN:1433-7851. (Wiley-VCH Verlag GmbH & Co. KGaA)Monolayers of mols. and nanoparticles should be prepd. on substrates only by self-assembly, but monolayers of microparticles can be produced by both self-assembly and direct manual attachment as if they are tiles. The quality of the monolayers is better when they are assembled by hand than by self-assembly.
- 25Park, C.; Lee, T.; Xia, Y.; Shin, T. J.; Myoung, J.; Jeong, U. Quick, Large-Area Assembly of a Single-Crystal Monolayer of Spherical Particles by Unidirectional Rubbing. Adv. Mater. 2014, 26, 4633– 4638, DOI: 10.1002/adma.20130587525https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2cXlvVSqtb4%253D&md5=cab6be32ac8141dd31cf22cccb54c35dQuick, Large-Area Assembly of a Single-Crystal Monolayer of Spherical Particles by Unidirectional RubbingPark, Choo Jin; Lee, Taeil; Xia, Younan; Shin, Tae Joo; Myoung, Jaemin; Jeong, UnyongAdvanced Materials (Weinheim, Germany) (2014), 26 (27), 4633-4638CODEN: ADVMEW; ISSN:0935-9648. (Wiley-VCH Verlag GmbH & Co. KGaA)This study introduces unidirectional rubbing of a dry powder of particles between two rubber plates as a quick and highly reproducible means of fabricating a single-crystal colloidal monolayer on a flat or curved substrate. The unidirectional rubbing of the particles described in this study introduces a quick, simple, inexpensive route to the assembly of spherical particles into a single-crystal monolayer on a flat or curved substrate. Under rubbing, the particles collectively roll along the rubbing direction so that the initial multiple grains merge to form a large single domain. The practical key variables for the monolayer assembly are the adhesion energy of the substrate, the rubbing speed, and the normal pressure. Optimum rubbing conditions for a single-crystal monolayer vary according to particle size, but in general, the following tenets apply: (i) the process is applicable to any rubber surface as long as the surface is not too sticky or too hard; (ii) submicrometer particles require high pressure and slow rubbing, whereas microparticles need low pressure and fast rubbing; and (iii) repeated unidirectional rubbing can minimize line defects.
- 26Park, C.; Koh, K.; Jeong, U. Structural color painting by rubbing particle powder. Sci. Rep. 2015, 5, 8340, DOI: 10.1038/srep0834026https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2MXhtFKjur%252FJ&md5=5c24e5aa1e3aae48220c78d51fc831f2Structural Color Painting by Rubbing Particle PowderPark, Choo Jin; Koh, Kunsuk; Jeong, UnyongScientific Reports (2015), 5 (), 8340CODEN: SRCEC3; ISSN:2045-2322. (Nature Publishing Group)Structural colors originate from purely phys. structures. Scientists have been inspired to mimic the structures found in nature, the realization of these structures still presents a great challenge. We have recently introduced unidirectional rubbing of a dry particle powder on a rubbery surface as a quick, highly reproducible means to fabricate a single crystal monolayer assembly of particles over an unlimited area. This study extends the particle-rubbing process to a novel fine-art painting, structural color painting (SCP). SCP is based on structural coloring with varying iridescence according to the crystal orientation, as controlled by the rubbing direction. This painting technique can be applied on curved surfaces, which enriches the objects to be painted and helps the painter mimic the structures found in nature. It also allows for quick fabrication of complicated particle-assembly patterns, which enables replication of paintings.
- 27Israelachvilli, J. Intermolecular and Surface Forces; Elsevier Pte Singapore, 2011.There is no corresponding record for this reference.
- 28McCarty, L. S.; Winkleman, A.; Whitesides, G. M. Electrostatic self-assembly of polystyrene microspheres by using chemically directed contact electrification. Angew. Chem., Int. Ed. 2007, 46, 206– 209, DOI: 10.1002/anie.20060291428https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD2sXitlGitw%253D%253D&md5=42bf23a4bbd61aa911b44c3deaf5b861Electrostatic self-assembly of polystyrene microspheres by using chemically directed contact electrificationMcCarty, Logan S.; Winkleman, Adam; Whitesides, George M.Angewandte Chemie, International Edition (2007), 46 (1+2), 206-209CODEN: ACIEF5; ISSN:1433-7851. (Wiley-VCH Verlag GmbH & Co. KGaA)Electrostatic charges can be induced in functionalized polystyrene beads. Oppositely charged beads then aggregate to form superstructures. A coat of small beads can self-assemble around a large bead. After annealing, another layer of beads can be added. The technique, based on contact electrification, avoids the use of expensive equipment and enables the use of large quantities of material.
- 29Grzybowski, B. A.; Winkleman, A.; Wiles, J. A.; Brumer, Y.; Whitesides, G. M. Electrostatic self-assembly of macroscopic crystals using contact electrification. Nat. Mater. 2003, 2, 241– 245, DOI: 10.1038/nmat86029https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD3sXisFWgs78%253D&md5=6291995a48069dc57a36536f33b91a74Electrostatic self-assembly of macroscopic crystals using contact electrificationGrzybowski, Bartosz A.; Winkleman, Adam; Wiles, Jason A.; Brumer, Yisroel; Whitesides, George M.Nature Materials (2003), 2 (4), 241-245CODEN: NMAACR; ISSN:1476-1122. (Nature Publishing Group)Self-assembly of components larger than mols. into ordered arrays is an efficient way of prepg. microstructured materials with interesting mech. and optical properties. Although crystn. of identical particles or particles of different sizes or shapes can be readily achieved, the repertoire of methods to assemble binary lattices of particles of the same sizes but with different properties is very limited. This paper describes electrostatic self-assembly of two types of macroscopic components of identical dimensions using interactions that are generated by contact electrification. The systems we have examd. comprise two kinds of objects (usually spheres) made of different polymeric materials that charge with opposite elec. polarities when agitated on flat, metallic surfaces. The interplay of repulsive interactions between like-charged objects and attractive interactions between unlike-charged ones results in the self-assembly of these objects into highly ordered, closed arrays. Remarkably, some of the assemblies that form are not electroneutral, i.e., they possess a net charge. The authors suggest that the stability of these unusual structures can be explained by accounting for the interactions between elec. dipoles that the particles in the aggregates induce in their neighbors.
- 30Cademartiri, R.; Stan, C. A.; Tran, V. M.; Wu, E.; Friar, L.; Vulis, D.; Clark, L. W.; Tricard, S.; Whitesides, G. M. A simple two-dimensional model system to study electrostatic-self-assembly. Soft Matter 2012, 8, 9771– 9791, DOI: 10.1039/c2sm26192h30https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC38XhtlekurnP&md5=ffa6c6e798ad346da6e09d4825bb2817A simple two-dimensional model system to study electrostatic-self-assemblyCademartiri, Rebecca; Stan, Claudiu A.; Tran, Vivian M.; Wu, Evan; Friar, Liam; Vulis, Daryl; Clark, Logan W.; Tricard, Simon; Whitesides, George M.Soft Matter (2012), 8 (38), 9771-9791CODEN: SMOABF; ISSN:1744-683X. (Royal Society of Chemistry)This paper surveys the variables controlling the lattice structure and charge in macroscopic Coulombic crystals made from elec. charged, millimeter-sized polymer objects (spheres, cubes, and cylinders). Mech. agitation of these objects inside planar, bounded containers caused them to charge elec. through contact electrification, and to self-assemble. The processes of electrification and self-assembly, and the characteristics of the assemblies, depended on the type of motion used for agitation, on the type of materials used for the objects and the dish, on the size and shape of the objects and the dish, and on the no. of objects. Each of the three different materials in the system (of the dish and of the two types of spheres) influenced the electrification. Three classes of structures formed by self-assembly, depending on the exptl. conditions: two-dimensional lattices, one-dimensional chains, and zero-dimensional rosettes'. The lattices were characterized by their structure (disordered, square, rhombic, or hexagonal) and by the elec. charges of individual objects; the whole lattices were approx. elec. neutral. The lattices obsd. in this study were qual. different from ionic crystals; the charge of objects had practically continuous values which changed during agitation and self-assembly, and depended on exptl. conditions which included the lattice structure itself. The relationship between charge and structure led to the coexistence of regions with different lattice structures within the same assembly, and to transformations between different lattice structures during agitation.
- 31Battat, S.; Nagarkar, A. A.; Spaepen, F.; Weitz, D. A.; Whitesides, G. M. Kinetics of formation of a macroscale binary Coulombic material. Phys. Rev. Mater. 2023, 7, L040401, DOI: 10.1103/physrevmaterials.7.l04040131https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BB3sXhtVCrt77M&md5=d0421662af8a23e243e4d1f2ee30cd70Kinetics of formation of a macroscale binary Coulombic materialBattat, Sarah; Nagarkar, Amit A.; Spaepen, Frans; Weitz, David A.; Whitesides, George M.Physical Review Materials (2023), 7 (4), L040401CODEN: PRMHBS; ISSN:2475-9953. (American Physical Society)The electrostatic self-assembly of charged Brownian objects typically occurs in cases of short-range interactions. The objects form Coulombic materials that are close-packed and have long-range order. Here, we present a system in which two kinds of non-Brownian millimeter-sized beads tribocharge differently, experience long-range electrostatic interactions, and still form ordered two-dimensional structures. We provide a complete characterization of the kinetics of formation of these materials, as the total no. of beads is held const. and the relative no. of beads that tribocharge neg. or pos. is modified. We agitate the beads by shaking the dish in which they are contained. We show that the beads commonly adopt a transient structure that we call a rosette. A rosette consists of a central bead surrounded by six close-packed neighbors of a different kind. The symmetry of the final structure depends on the relative no. of neg. and pos. charged beads, and it is not necessarily the same as that of the transient structure. Our results bear important implications in the de novo design of Coulombic materials given our ability to isolate transient structures, identify the moment of their appearance, and quantify the impact of agitation, tribocharging, and Coulombic energy minimization on their persistence.
- 32Battat, S.; Weitz, D. A.; Whitesides, G. M. Melting of a macroscale binary Coulombic crystal. Soft Matter 2023, 19, 3190– 3198, DOI: 10.1039/D2SM01635D32https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BB3sXotVeitb0%253D&md5=f9033e26c7eefe3db8ee727cfb537c57Melting of a macroscale binary Coulombic crystalBattat, Sarah; Weitz, David A.; Whitesides, George M.Soft Matter (2023), 19 (17), 3190-3198CODEN: SMOABF; ISSN:1744-6848. (Royal Society of Chemistry)The question of melting has been addressed theor. and exptl. for two-dimensional crystals in thermal equil. However, as it pertains to out-of-equil. systems, the question is unresolved. Here, we present a platform to study the melting of a two-dimensional, binary Coulombic crystal composed of equal nos. of nylon and polytetrafluoroethylene (PTFE) beads that measure a couple of millimeters in diam. The beads are tribocharged-nylon pos. and PTFE neg.-and they experience long-range electrostatic interactions. They form a square crystal in which nylon and PTFE beads sit at alternating sites on a checkerboard lattice. We melt the crystal by agitating the dish in which it resides using an orbital shaker. We compare the melting behavior of the crystal without impurities to that of the crystal with impurities, where we use gold-coated nylon beads as impurities because they tribocharge negligibly. Our results reveal that impurities do not influence the melting of the crystal. Instead, the crystal undergoes shear-induced melting, beginning from its edges, due to its collisions with the dish. As a result of repetitive collisions, the beads acquire kinetic energy, undergo rearrangements, and become disordered. Unlike most examples of shear-induced melting, portions of the crystal remain locally ordered given the persistence of electrostatic interactions and the occurrence of some collisions that are favorable to ordering clusters of beads. Our work clarifies the melting behavior of sheared crystals whose constituents have persistent long-range interactions. It may prove valuable in detg. the conditions under which such materials are immune to disorder.
- 33Lacks, D. J.; Shinbrot, T. Long-standing and unresolved issues in triboelectric charging. Nat. Rev. Chem 2019, 3, 465, DOI: 10.1038/s41570-019-0115-133https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC1MXhtlOgurfK&md5=5afd3ec73757da5986995b2ba4d9ff6dLong-standing and unresolved issues in triboelectric chargingLacks, Daniel J.; Shinbrot, TroyNature Reviews Chemistry (2019), 3 (8), 465-476CODEN: NRCAF7; ISSN:2397-3358. (Nature Research)A review. Static electrification is among the earliest of the sciences, well known to us all and with widespread and important consequences. Yet, its most basic foundations remain poorly understood. For example, after centuries of research, it is still not clear whether electrons, ions or even bulk material transfer is responsible for the obsd. charging. Recent work has leveraged the most advanced exptl. and theor. approaches, and has addressed the phenomenon from perspectives of quantum mechanics, surface chem., mechanochem. and statistical physics. While the resulting findings have advanced many aspects of our understanding, they have also led to the discovery of new surprises that we are only beginning to appreciate. This Review addresses both recent advances and their accompanying surprises.
- 34Jimidar, I. S.; Sotthewes, K.; Gardeniers, H.; Desmet, G. Spatial segregation of microspheres by rubbing-induced triboelectrification on patterned surfaces. Langmuir 2020, 36, 6793– 6800, DOI: 10.1021/acs.langmuir.0c0095934https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BB3cXhtVCrsLrM&md5=3959d0aa8770a2a9b1bb52165dd90c16Spatial Segregation of Microspheres by Rubbing-Induced Triboelectrification on Patterned SurfacesJimidar, Ignaas S. M.; Sotthewes, Kai; Gardeniers, Han; Desmet, GertLangmuir (2020), 36 (24), 6793-6800CODEN: LANGD5; ISSN:0743-7463. (American Chemical Society)Particle (monolayer) assembly is essential to various scientific and industrial applications, such as the fabrication of photonic crystals, optical sensors, and surface coatings. Several methods, including rubbing, have been developed for this purpose. Here, we report on the serendipitous observation that microparticles preferentially partition onto the fluorocarbon-coated parts of patterned silicon and borosilicate glass wafers when rubbed with poly(dimethylsiloxane) slabs. To explore the extent of this effect, we varied the geometry of the pattern, the substrate material, the ambient humidity, and the material and size of the particles. Partitioning coeffs. amounted up to a factor of 12 on silicon wafers and even ran in the 100s on borosilicate glass wafers at zero humidity. Using Kelvin probe force microscopy, the observations can be explained by triboelectrification, inducing a strong electrostatic attraction between the particles and the fluorocarbon zones, while the interaction with the noncoated zones is insignificant or even weakly repulsive.
- 35Butt, H.-J.; Kappl, M. Surface and Interfacial Forces; John Wiley & Sons, 2018.There is no corresponding record for this reference.
- 36Serra, M.; Ferraro, D.; Pereiro, I.; Viovy, J.-L.; Descroix, S. The power of solid supports in multiphase and droplet-based microfluidics: towards clinical applications. Lab Chip 2017, 17, 3979– 3999, DOI: 10.1039/C7LC00582B36https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2sXhsV2ls7bM&md5=12fd1abf85695043ebe65b43e9bd1369The power of solid supports in multiphase and droplet-based microfluidics: towards clinical applicationsSerra, M.; Ferraro, D.; Pereiro, I.; Viovy, J.-L.; Descroix, S.Lab on a Chip (2017), 17 (23), 3979-3999CODEN: LCAHAM; ISSN:1473-0189. (Royal Society of Chemistry)A review. Multiphase and droplet microfluidic systems are growing in relevance in bioanal.-related fields, esp. due to the increased sensitivity, faster reaction times and lower sample/reagent consumption of many of its derived bioassays. Often applied to homogeneous (liq./liq.) reactions, innovative strategies for the implementation of heterogeneous (typically solid/liq.) processes have recently been proposed. These involve, for example, the extn. and purifn. of target analytes from complex matrixes or the implementation of multi-step protocols requiring efficient washing steps. To achieve this, solid supports such as functionalized particles (micro or nanometric) presenting different phys. properties (e.g. magnetic, optical or others) are used for the binding of specific entities. The manipulation of such supports with different microfluidic principles has both led to the miniaturization of existing biomedical protocols and the development of completely new strategies for diagnostics and research. In this review, multiphase and droplet-based microfluidic systems using solid suspensions are presented and discussed with a particular focus on: i) working principles and technol. developments of the manipulation strategies and ii) applications, critically discussing the level of maturity of these systems, which can range from initial proofs of concept to real clin. validations.
- 37Li, X.; Chen, L.; Ma, Y.; Weng, D.; Li, Z.; Song, L.; Zhang, X.; Yu, G.; Wang, J. Ultrafast Fabrication of Large-Area Colloidal Crystal Micropatterns via Self-Assembly and Transfer Printing. Adv. Funct. Mater. 2022, 32, 2205462, DOI: 10.1002/adfm.20220546237https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BB38XitVChsb7O&md5=c0ae27a2420e62a0009ebb9568730250Ultrafast Fabrication of Large-Area Colloidal Crystal Micropatterns via Self-Assembly and Transfer PrintingLi, Xuan; Chen, Lei; Ma, Yuan; Weng, Ding; Li, Zhaoxin; Song, Lele; Zhang, Xuanhe; Yu, Guoxu; Wang, JiadaoAdvanced Functional Materials (2022), 32 (45), 2205462CODEN: AFMDC6; ISSN:1616-301X. (Wiley-VCH Verlag GmbH & Co. KGaA)Colloidal crystals have brought the promise of revolution to modern engineering, yet commonly used fabrication technologies are still limited by the small prepn. area, time-consuming process, and dependence on sophisticated equipment. Here, a surface tension gradient-driven self-assembly strategy is proposed for the ultrafast fabrication of large-area colloidal crystals. The hydrogel loaded with sodium dodecyl sulfate is devised to construct a stable and continuous liq.-air interfacial tension gradient, and the resulting Marangoni effect can drive the micro-nano particles to instantaneously form (within several seconds) highly ordered colloidal crystals. Benefiting from the long range of surface tension gradients, the fabrication area of colloidal crystal films is demonstrated to exceed an astonishing 1000 cm2 without compromising their quality, showing great potential in scale-up manuf. Moreover, particles of a wide variety of sizes, materials, and functionalities can form close-packed self-assembly monolayers and be transferred to various substrates without damage, exhibiting great versatility. Inspired by ink microprinting, an ultrafast nanoparticle transfer printing method is further proposed to convert the close-packed nanoparticle monolayers into large-area conformal micropatterns with single-nanoparticle resoln. The great potential of nanoparticle micropatterns is demonstrated in flexible micro-electronics/skin electronics. This user-friendly, efficient self-assembly, and micropatterning strategy provide promising opportunities for academic and real industrial applications.
- 38Šutka, A.; Lapčinskis, L.; Verners, O.; Ģe̅rmane, L.; Smits, K.; Pludons, A.; Gaidukovs, S.; Jera̅ne, I.; Zubkins, M.; Pudzs, K. Bio-Inspired Macromolecular Ordering of Elastomers for Enhanced Contact Electrification and Triboelectric Energy Harvesting. Adv. Mater. Technol. 2022, 7, 2200162, DOI: 10.1002/admt.20220016238https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BB38XhtlSgsrzP&md5=dec751246a50b040b5cc41244d729c1eBio-Inspired Macromolecular Ordering of Elastomers for Enhanced Contact Electrification and Triboelectric Energy HarvestingSutka, Andris; Lapcinskis, Linards; Verners, Osvalds; Germane, Liva; Smits, Krisjanis; Pludons, Arturs; Gaidukovs, Sergejs; Jerane, Ilze; Zubkins, Martins; Pudzs, Kaspars; Sherrell, Peter Cameron; Blums, JurisAdvanced Materials Technologies (Weinheim, Germany) (2022), 7 (10), 2200162CODEN: AMTDCM; ISSN:2365-709X. (Wiley-VCH Verlag GmbH & Co. KGaA)Triboelectrification of polymers enables mech. energy harvesting in triboelec. generators, droplet generators, and ferroelectrets. Herein, triboelec. polymers, inspired by the ordering in spider-silk, with strongly enhanced contact electrification are presented. The ordering in polyether block amide (PEBA) is induced by the addn. of inorg. goethite (α-FeOOH) nanowires that form H-bonds with the elastomeric matrix. The addn. of as little as 0.1 vol% of α-FeOOH into PEBA increases the surface charge by more than order of magnitude (from 0.069 to 0.93 nC cm-2). The H-bonds between α-FeOOH and PEBA promote the formation of inclusions with higher degree of macromol. ordering, analogous to the structure of spider silk. The formation of these inclusions is proven via nanoindentation hardness measurements and correlated with H-bond-induced chem. changes by Fourier transform IR spectroscopy and direct scanning calorimetry. Theor. studies reveal that the irregularity in hardness provides stress accumulation on the polymer surface during contact-sepn. Subsequent mol. dynamic studies demonstrate that stress accumulation promotes the mass-transfer mechanism of contact electrification. The proposed macromol. structure design provides a new paradigm for developing materials for applications in mech. energy harvesting.
- 39Jimidar, I. S.; Sotthewes, K.; Gardeniers, H.; Desmet, G.; van der Meer, D. Self-organization of agitated microspheres on various substrates. Soft Matter 2022, 18, 3660– 3677, DOI: 10.1039/D2SM00432A39https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BB38XhtFGnsLvK&md5=f15d9d34a33024a4a1eef549aa6e73a9Self-organization of agitated microspheres on various substratesJimidar, Ignaas S. M.; Sotthewes, Kai; Gardeniers, Han; Desmet, Gert; van der Meer, DevarajSoft Matter (2022), 18 (19), 3660-3677CODEN: SMOABF; ISSN:1744-6848. (Royal Society of Chemistry)The vibration dynamics of relatively large granular grains is extensively treated in the literature, but comparable studies on the self-assembly of smaller agitated beads are lacking. In this work, we investigate how the particle properties and the properties of the underlying substrate surface affect the dynamics and self-organization of horizontally agitated monodisperse microspheres with diams. between 3 and 10μm. Upon agitation, the agglomerated hydrophilic silica particles locally leave traces of particle monolayers as they move across the flat uncoated and fluorocarbon-coated silicon substrates. However, on the micromachined silicon tray with relatively large surface roughness, the agitated silica agglomerates form segregated bands reminiscent of earlier studies on granular suspensions or Faraday heaps. On the other hand, the less agglomerated hydrophobic polystyrene particles form densely occupied monolayer arrangements regardless of the underlying substrate. We explain the observations by considering the relevant adhesion and friction forces between particles and underlying substrates as well as those among the particles themselves. Interestingly, for both types of microspheres, large areas of the fluorocarbon-coated substrates are covered with densely occupied particle monolayers. By qual. examg. the morphol. of the self-organized particle monolayers using the Voronoi approach, it is understood that these monolayers are highly disordered, i.e., multiple symmetries coexist in the self-organized monolayers. However, more structured symmetries are identified in the monolayers of the agitated polystyrene microspheres on all the substrates, albeit not all precisely positioned on a hexagonal lattice. On the other hand, both the silica and polystyrene monolayers on the bare silicon substrates transition into less disordered structures as time progresses. Using Kelvin probe force microscopy measurements, we show that due to the tribocharging phenomenon, the formation of particle monolayers is promoted on the fluorocarbon surface, i.e., a local electrostatic attraction exists between the particle and the substrate.
- 40Jimidar, I. S.; Kwiecinski, W.; Roozendaal, G.; Kooij, E. S.; Gardeniers, H. J.; Desmet, G.; Sotthewes, K. Influence of Wettability and Geometry on Contact Electrification between Nonionic Insulators. ACS Appl. Mater. Interfaces 2023, 15, 42004– 42014, DOI: 10.1021/acsami.3c0572940https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BB3sXhtlCms7bJ&md5=16433f2640b53f669320aafe3458b8b2Influence of Wettability and Geometry on Contact Electrification between Nonionic InsulatorsJimidar, Ignaas S. M.; Kwiecinski, Wojciech; Roozendaal, Gijs; Kooij, E. Stefan; Gardeniers, Han J. G. E.; Desmet, Gert; Sotthewes, KaiACS Applied Materials & Interfaces (2023), 15 (35), 42004-42014CODEN: AAMICK; ISSN:1944-8244. (American Chemical Society)Contact electrification is an interfacial process in which two surfaces exchange elec. charges when they are in contact with one another. Consequently, the surfaces may gain opposite polarity, inducing an electrostatic attraction. Therefore, this principle can be exploited to generate electricity, which has been precisely done in triboelec. nanogenerators (TENGs) over the last decades. The details of the underlying mechanisms are still ill-understood, esp. the influence of relative humidity (RH). Using the colloidal probe technique, we convincingly show that water plays an important role in the charge exchange process when two distinct insulators with different wettability are contacted and sepd. in <1 s at ambient conditions. The charging process is faster, and more charge is acquired with increasing relative humidity, also beyond RH = 40% (at which TENGs have their max. power generation), due to the geometrical asymmetry (curved colloid surface vs planar substrate) introduced in the system. In addn., the charging time const. is detd., which is found to decrease with increasing relative humidity. Altogether, the current study adds to our understanding of how humidity levels affect the charging process between two solid surfaces, which is even enhanced up to RH = 90% as long as the curved surface is hydrophilic, paving the way for designing novel and more efficient TENGs, eco-energy harvesting devices which utilize water and solid charge interaction mechanism, self-powered sensors, and tribotronics.
- 41Jones, R.; Pollock, H. M.; Cleaver, J. A.; Hodges, C. S. Adhesion forces between glass and silicon surfaces in air studied by AFM: Effects of relative humidity, particle size, roughness, and surface treatment. Langmuir 2002, 18, 8045– 8055, DOI: 10.1021/la025919641https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD38XmvFKrtrg%253D&md5=7dc74369cff7aeddb2909f165a875510Adhesion Forces between Glass and Silicon Surfaces in Air Studied by AFM: Effects of Relative Humidity, Particle Size, Roughness, and Surface TreatmentJones, Robert; Pollock, Hubert M.; Cleaver, Jamie A. S.; Hodges, Christopher S.Langmuir (2002), 18 (21), 8045-8055CODEN: LANGD5; ISSN:0743-7463. (American Chemical Society)Using the at. force microscope (AFM), the pull-off forces between flat glass or Si surfaces and Si AFM tips or glass microspheres of different sizes were extensively studied as a function of relative humidity (RH) in the range 5-90%, as model systems for the behavior of cohesive powders. The glass and Si substrates were treated to render them either hydrophobic or hydrophilic. All the hydrophilic surfaces gave simple force curves and pull-off forces increasing uniformly with RH. Small contacts (R ∼ 20 nm) gave pull-off forces close to values predicted by simple Laplace-Kelvin theory (∼20 nN), but the values with microspheres (R ∼ 20 μm) fell well below predictions for sphere-flat or sphere-sphere geometry, due to roughness and asperity contacts. The hydrophobic Si surfaces also exhibited simple behavior, with no significant RH dependence. The pull-off force again fell well below predicted values (Johnson-Kendall-Roberts contact mechanics theory) for the larger contacts. Hydrophobic glass gave similar adhesion to Si over most of the RH range, but against both Si tips and glass microspheres, there was an anomalously large adhesion in the RH range 20-40%, accompanied by a long-range noncontact force. The adhesion on fully hydrophilic surfaces and its RH dependence can be mostly explained by current theories of capillary bridges, but the interpretation is complicated by the sensitivity of theor. predictions to contact geometry (and hence to roughness effects) and by uncertainties in the thickness of adsorbed H2O layers. The anomalous behavior on hydrophobic glass surfaces at intermediate values of RH is not fully understood, but possible causes are (1) dipole layers in the partially formed H2O film, giving rise to patch charges and long-range forces, or (2) fixed charges at a reactive glass surface, involving specific bonding reactions. The results may be useful in explaining the behavior of cohesive powders with different coatings or those which show a large humidity dependence (e.g., zeolites) or show electrostatic charging effects (e.g., SiO2 aerogels).
- 42Preud’homme, N.; Lumay, G.; Vandewalle, N.; Opsomer, E. Tribocharging of granular materials and influence on their flow. Soft Matter 2023, 19, 8911– 8918, DOI: 10.1039/D3SM01322G42https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BB3sXitlGisLbM&md5=06a46570b078f4385af7fa978ac8d2fbTribocharging of granular materials and influence on their flowPreud'homme, Nicolas; Lumay, Geoffroy; Vandewalle, Nicolas; Opsomer, EricSoft Matter (2023), 19 (45), 8911-8918CODEN: SMOABF; ISSN:1744-6848. (Royal Society of Chemistry)Once granular materials flow, particles charge because of the triboelec. effect. When particles touch each other, charges are exchanged during contact whether they are made of the same material or not. Surprisingly, when different sizes of particles are mixed together, large particles tend to charge pos. while small particles charge neg. If the particles are relatively small (typically smaller than a millimeter), the electrostatic interaction between the particles becomes significant and leads to aggregation or sticking on the surface of the container holding them. Studying those effects is challenging as the mechanisms that govern the triboelec. effect are not fully understood yet. We show that the patch model (or mosaic model) is suitable to reproduce numerically the flow of triboelec. charged granular materials as the specific charging of bi-disperse granular materials can be retrieved. We investigate the influence of charging on the cohesion of granular materials and highlight the relevant parameters related to the patch model that influence cohesion. Our results shed new light on the mechanisms of the triboelec. effect as well as on how the charging of granular materials influences cohesion using numerical simulations.
- 43Lacks, D. J.; Mohan Sankaran, R. Contact electrification of insulating materials. J. Phys. D: Appl. Phys. 2011, 44, 453001, DOI: 10.1088/0022-3727/44/45/45300143https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC3MXhsFSltb3N&md5=55f4fe8577c6d9d38b759fd3df49d572Contact electrification of insulating materialsLacks, Daniel J.; Sankaran, R. MohanJournal of Physics D: Applied Physics (2011), 44 (45), 453001/1-453001/15CODEN: JPAPBE; ISSN:0022-3727. (Institute of Physics Publishing)A review. The electrostatic charge that is generated when two materials are contacted or rubbed and then sepd. is a well-known phys. process that has been studied for more than 2500 years. Contact electrification occurs in many contexts, both natural and technol. For example, in dust storms the collisions between particles lead to electrostatic charging and in extreme cases, extraordinary lightning displays. In electrophotog., toner particles are intentionally charged to guide their deposition in well-defined patterns. Despite such a long history and so many important consequences, a fundamental understanding of the mechanism behind contact electrification remains elusive. An open question is what type of species are transferred between the surfaces to generate charge-expts. suggest various species ranging from electrons to ions to nanoscopic bits of material, and theor. work suggests that non-equil. states may play an important role. Another open question is the contact electrification that occurs when two insulating materials with identical phys. properties touch-since there is no apparent driving force, it is not clear why charge transfer occurs. A third open question involves granular systems-models and expts. have shown that a particle-size dependence for the charging often exists. In this review, we discuss the fundamental aspects of contact electrification and highlight recent research efforts aimed at understanding these open questions.
- 44Lotito, V.; Zambelli, T. Pattern detection in colloidal assembly: A mosaic of analysis techniques. Adv. Colloid Interface Sci. 2020, 284, 102252, DOI: 10.1016/j.cis.2020.10225244https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BB3cXhvVOmurfF&md5=8931cd33d363c3615cad011cf583a749Pattern detection in colloidal assembly: A mosaic of analysis techniquesLotito, Valeria; Zambelli, TomasoAdvances in Colloid and Interface Science (2020), 284 (), 102252CODEN: ACISB9; ISSN:0001-8686. (Elsevier B.V.)A review. In addn., casting light on the structures formed by colloidal particles can help to get better insight into colloidal interactions and understand phase transitions. Finally, the growing interest in colloidal assemblies in materials science for practical applications going from optoelectronics to biosensing imposes a thorough characterization of the morphol. of colloidal assemblies because of the intimate relationship between morphol. and phys. properties (e.g. optical and mech.) of a material. Several image anal. techniques developed to investigate images (acquired via SEM, digital video microscopy and other imaging methods) provide variegated and complementary information on the colloidal structures under scrutiny. However, understanding how to use such image anal. tools to get information on the characteristics of the colloidal assemblies may represent a non-trivial task, because it requires the combination of approaches drawn from diverse disciplines such as image processing, computational geometry and computational topol. and their application to a primarily physico-chem. process. In this review we provide a methodical and extensive description of real-space image anal. tools by explaining their principles and their application to the investigation of two-dimensional colloidal assemblies with different morphol. characteristics.
- 45López-González, F.; Pacheco-Vázquez, F.; Donado, F. Ordering of a granular layer of cubes under strain-induced shear and vibration. Phys. A 2023, 620, 128768, DOI: 10.1016/j.physa.2023.128768There is no corresponding record for this reference.
- 46Šutka, A.; Lapčinskis, L.; He, D.; Kim, H.; Berry, J. D.; Bai, J.; Knite, M.; Ellis, A. V.; Jeong, C. K.; Sherrell, P. C. Engineering Polymer Interfaces: A Review toward Controlling Triboelectric Surface Charge. Adv. Mater. Interfaces 2023, 10, 2300323, DOI: 10.1002/admi.20230032346https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BB3sXhsF2msbvL&md5=5d5f70235290cb2eecde9b3ab371445eEngineering Polymer Interfaces: A Review toward Controlling Triboelectric Surface ChargeSutka, Andris; Lapcinskis, Linards; He, Delong; Kim, Hyunseung; Berry, Joseph D.; Bai, Jinbo; Knite, Maris; Ellis, Amanda V.; Jeong, Chang Kyu; Sherrell, Peter C.Advanced Materials Interfaces (2023), 10 (26), 2300323CODEN: AMIDD2; ISSN:2196-7350. (Wiley-VCH Verlag GmbH & Co. KGaA)A review. Contact electrification and triboelec. charging are areas of intense research. Despite their low ability to accept or donate electrons, polymer insulator based triboelec. nanogenerators have emerged as highly efficient mech.-to-elec. conversion devices. Here, it is reviewed the structure-property-performance of polymer insulators in triboelec. nanogenerators and focus on tools that can be used to directly enhance charge generation, via altering a polymer's mech., thermal, chem., and topog. properties. In addn. to the discussion of these fundamental properties, the use of additives to locally manipulate the polymer surface structure is discussed. The link between each property and the underlying charging mechanism is discussed, in the context of both increasing surface charge and predicting the polarity of surface charge, and pathways to engineer triboelec. charging are highlighted. Key questions facing the field surrounding data reporting, the role of water, and synergy between mass, electron, and ion transfer mechanisms are highlighted with aspirational goals of a holistic model for triboelec. charging proposed.
- 47Verners, O.; Lapčinskis, L.; Sherrell, P. C.; Šutka, A. Contact Electrification at Dielectric Polymer Interfaces: On Bond Scission, Material Transfer, and Electron Transfer. Adv. Mater. Interfaces 2023, 10, 2300562, DOI: 10.1002/admi.20230056247https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BB3sXhvFyrurvO&md5=fcd1136039732b10965ee559119e9c21Contact Electrification at Dielectric Polymer Interfaces: On Bond Scission, Material Transfer, and Electron TransferVerners, Osvalds; Lapcinskis, Linards; Sherrell, Peter C.; Sutka, AndrisAdvanced Materials Interfaces (2023), 10 (36), 2300562CODEN: AMIDD2; ISSN:2196-7350. (Wiley-VCH Verlag GmbH & Co. KGaA)Triboelec. nanogenerators (TENGs) are revolutionizing mech.-to-elec. energy harvesting. TENGs harvest energy through the polymer-polymer contact electrification (PCE) mechanism, driven by nanoscale processes at the contact interface. Currently, when discussing PCE there are two distinct schools of thought on which nanoscale interactions drive charging at the contact interface; (1) electron transfer, where orbital overlap leads to charge tunneling between polymers; or (2) mass (material) transfer, where polymer chain entanglement and intermol. bonding leads to heterolytic bond scission. Here, a combination of in silico and benchtop expts. is used to elucidate the relative role of electron and mass transfer in PCE. In silico expts. show that covalent bond scission in a polymethylmethacrylate/polytetrafluoroethylene system occurs at 348 kcal mol-1, prior to electron cloud overlap, where the HOMO and LUMO of the system remain sepd. by 163 kcal mol-1. Benchtop expts. show PCE-generated charges cannot be simply discharged via elec. grounding, indicating the formation of bound surface charge from mass transfer. The calcns. and contact-electrification tests provide strong evidence to support mass transfer being the leading mechanism driving PCE.
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The Supporting Information is available free of charge at https://pubs.acs.org/doi/10.1021/acsami.3c16830.
Additional experimental details, Voronoi approach to quantify the quality of the assembled monolayers, force spectroscopy measurements, determining Young’s modulus, Kelvin probe force microscopy details, monolayers assembled on the different stamps, and wafer-scale assembly of HCP crystals on tunable patterns and iridescence structure colors observed under illumination (PDF)
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