Additive Analytics: Easy Transformation of Low-Cost Fused Deposition Modeling Three-Dimensional Printers for HPTLC Sample Application

Additive manufacturing, known as three-dimensional (3D) printing technologies, has revolutionized production in all domains of science and technology. Although 3D printing has a high impact on research and development, its capacity to implement low-cost, flexible, and robust sample handling automation has not been exploited in full. To this end, we have created a low-cost, robust, and easy-to-utilize kit to transform an off-the-shelf fused deposition modeling 3D printer to a thin layer chromatography (TLC) sample application device. Our technology solution improves TLC convenience when higher throughput of the established method is required. The developed dual-needle sprayer allows simple and exceptionally robust automatic sample application. The device is especially well-suited for high-performance TLC-assisted method selection in counter-current chromatography. A step-by-step guide and list of required parts, including 3D printable files with instruction, can be obtained from the Supporting Information for research usage and open development.

Part 7 a,b a: *atomizer*, b: *print_atomizer* Part 14 *TLC_bed*.stl Step-by-step assembly guide and standard operation information For Italic https://www.department.ch.tum.de/wssb/hptlc/ A SLA 3D printer can be used to manufacture these parts in your labarotory or alternatively the nearest CNC machine service or 3D printing service can be instructed. Syringes and especially needles can result in harm to your body. Always apply adequate safety precautions. No responsibility can be taken for health risks associated. S1 * a:*Syringe_quickrelease*, b: *Plunger_fix* Step 1, 3D Printer: Generally any 3D printer with a sufficient height and bed size can be used as HPLTC tool in conjunction with the sheat needle atomizer. The here presented parts are designed to fit 20 x 10 cm HPTLC analytical plates and an i3 Prusa based open source printer. A version of the recommended low-cost rigid metal frame Monoprice Maker Select 3D Printer v2 is depicted ( Figure S1) (Monoprice, Inc. Rancho Cucamonga, CA, USA.).

Part 1
Step 2, Syringe: Autosampler glass syringes (Trojan 25, 50, 100 µl, RN) with a removable needle ( Figure S2) can be used to apply different sample volumes. Unscrew the cap-nut ( Figure S2, Part 2b) and let a milling machine service thread it. Alternativley attach and seal the 3D printable Luer-Lock attachment (Part 7b, not shown).

Part 7a
Step 4, Syringe assembly: Assemble sheat-needle sprayer part and SGE syringe ( Figure S4). Shorten needles to the same length by using a cutting disc. *Elongate the SGE plunger with a 1.1 mm cannula by hot soldering. Insert the elongated plunger to the syringe ( Figure  S4, Part 2c*).

Part 7a
Part 2c* S2 Figure     Step 5, Syringehandler: Manufacture Part 3 ( Figure S5) by SLA (or other) 3D printing or CNC machine methods. Add threads and cut open all holes by a handheld drilling machine when necessary (e.g. Dremel).

Part 3a
Part 3b Step 6, Syringehandler assembly: Assemble GT2 pulley ( Figure S6, Part 6b) to Nema 14. When necessary add nudge to drive shaft to increase slip resistance force.

Part 4 Part 6b
Step 7, Syringe-plunger: Connect syringe plunger fixture (Figure S7, Part 9b) to the GT2 loop belt (Figure S7). Using a leather punch, create a hole in the loop belt. Add a drive belt spring when necessary.
Alternative solution: Use a non-looped GT2 belt. Punch two holes at a distance of 200 mm from the centre to centre. Connect both ends with Part 9b ( Figure S7).

Part 9b
S3 Figure     Step 4b, Printable Atomizer: Optional: use the 3D (SLA/SLS) printable connector Part 7b in conjunction with a standard Leur-Lock syringeneedle with a suitable diameter.
Step 9, Syringehandler assembly: Figure S8, Part 6b should be facing to the bottom side of Part 3a ( Figure S9).

Part 3a
Step 10a, Syringe fixing:     Step 11, Belt: Use the cylindrical pin as a shaft for the GT2 geared free pulley. ( Figure S13, Part 6b). First, add pully to drive belt. After that add cylindrical pin into the 5.0 mm through-hole.
Hold pulley in place with a 2 mm Allen key ( Figure S14). Force the cylindrical punch (Figure S13, Part 5) (DIN 7) trough the pulley.
The slight tension will keep the shaft in place ( Figure S15). Should shaft loosening be a problem, add a piece of Duct-tape to the sides of the shaft. Add a small amount of high grade drilling oil as a lubricant to the pulley.
Step 10b, Syringe fixing: Use 4 x M2,5 x 33 mm to mount Nema 14, Syringe and the quick-release ( Figure  S12). S5 Figure S12       Step 13, Belt: Connect the geared belt of the X-axis to the syringehandler, if necessary shorten belt. Connect towline cable drag chain to the side of the syringe holder ( Figure  S18, Part10b). Check free movement.
Step 14, Nitrogen flow: Connect solenoid ( Figure S19, Part 8) hose to sprayer (Part 7) and Nitrogen gas source. Connect the power cable to previous 3D printers cooling fan. Add a resistor (e.g. 50 Ohm) to restrict the load. ( Figure S19, Part 12) Step 15, Bed: Add HPTLC plate holder ( Figure S20, Part 14) to the previously heated printing bed. Remove temperature sensor and exchange with a constant resistor if firmware requires head bed temperature parameter (10k Ohm). Remove heat pad power cable and upcycle.   1. Never start a sampling process when the machine is unobserved and accessible to uninstructed colleagues.
2. Never shift positions of plates or samples or solvents when the printer is in operation. Pause or switch off, and continue after corrections.
3. The glass syringe is intentional the weakest part of the printer, should the GCODE do not match the physical setup this might lead to breakage of the glass cylinder. Which typically minimises further mechanical damage.
4. When using toxic organic solvents, place the device in a suitable hood. 5. Connect hose at a pressure of 2 bar nitrogen gas to the solenoid valve connected to the sprayer.
6. In order to apply samples, the 3D printer movements need to be set up to run a sequence of liquid handling operations. Make sure to program the right movements to the printing head. A sample GCODE sequence is added at the bottom of this document. 7. Before starting to apply samples, the syringe needs to be cleaned first, and in between samples. Therefore the machine needs to move the syringe to a vial filled with a suitable organic solvent. Engage the flow of nitrogen during dispensing. Numerical script guide GCODE GCODE commands can be wrtiten in any text editor. When saving the text file with the .gcode file extension, these will be recognized by any FDM 3D Printer. For further information see: https://reprap.org/wiki/G-code An commented example can be found below: Step 1, Coordinate system reset Initially, the cartesian coordinate system is zeroed with the help of end stop limits.
Take note: The syringe plunger must be in its lowest position when starting the script/ print.
Step 2, 1.Sample application, by initially moving the needle tips to the sample vail, withdrawing sample with the extruder (E). 2.Drying the dual needle before sample application by a burst of nitrogen is recomended! Nitrogen/Solenoid ON (M106 P2 S255). OFF (M106 P2 S0). 4.Sample application, with solenoid/nitrogen flow ON (moving back and forth for improved drying and atomization) These parameters can be altered to fit specific sample volume and solvent needs.
Step 3, Needle wash steps, required to clean syringe syringe and needle tip.