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Modeling Microcapsules That Communicate through Nanoparticles To Undergo Self-Propelled Motion

O. Berk Usta, Alexander Alexeev^†, Guangdong Zhu^‡ and Anna C. Balazs*

Chemical Engineering Department, University of Pittsburgh, Pittsburgh, Pennsylvania 15261

ACS Nano, 2008, 2 (3), pp 471–476

DOI: 10.1021/nn700379v

Publication Date (Web): February 28, 2008

†

Current address: George W. Woodruff School of Mechanical Engineering, Georgia Institute of Technology, Atlanta, GA 30332-0405.

‡

Current address: Mechanical Engineering Department, University of New Mexico, Albuquerque, NM 87131.

* Address correspondence to balazs1@engr.pitt.edu.

Abstract

Using simulation and theory, we demonstrate how nanoparticles can be harnessed to regulate the interaction between two initially stationary microcapsules on a surface and promote the self-propelled motion of these capsules along the substrate. The first microcapsule, the “signaling” capsule, encases nanoparticles, which diffuse from the interior of this carrier and into the surrounding solution; the second capsule is the “target” capsule, which is initially devoid of particles. Nanoparticles released from the signaling capsule modify the underlying substrate and thereby initiate the motion of the target capsule. The latter motion activates hydrodynamic interactions, which trigger the signaling capsule to follow the target. The continued release of the nanoparticles sustains the motion of both capsules. In effect, the system constitutes a synthetic analogue of biological cell signaling and our findings can shed light on fundamental physical forces that control interactions between cells. Our findings can also yield guidelines for manipulating the interactions of synthetic microcapsules in microfluidic devices.

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