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Device Technologies and Biomedical Robotics

Device Technologies and Biomedical Robotics - Poster Session B

Poster J2 - Fabrication of Plastic-based Microfluidic Chips For in-line Cell Characterization

Thursday, October 24, 2024
2:45 PM - 3:45 PM EST
Location: Exhibit Hall E, F & G

Introduction:  Within the field of biomedicine, the characterization of distinct cell types based off surface markers is a necessary step in the commercialization of cell therapies. By sidestepping the time, material, and labor costs associated with conventional immunoassays such as flow cytometry, the immunophenotyping of cell therapies can be integrated into the bioreactors themselves and potentially be automated, further improving the process. Typical microfluidic chips made for research applications of this characterization consist often of PDMS (polydimethylsiloxane), glass slides, and other materials as components which inhibits the commercialization and further applications of these devices. This project aimed to take an existing autonomous microchip for immune cell analysis (Arifuzzman et al. 2023) and develop a fabrication protocol for making the microchips out of plastics as opposed to PDMS and glass to make the existing microchip design commercially viable. A successful prototype of the microfluidic chip was produced, however further work is needed to fully replicate the original device.

Materials and

Methods:  Hot embossing: a silicon master mold for the PDMS stamps used for hot embossing was fabricated by traditional lithography and taped to a petri dish. PDMS elastomer was mixed with a crosslinker in a 10:1 ratio before being poured on to the silicon wafer and degassed for 30 minutes before curing in an oven for 6-7 hours at 72°C. Polycarbonate chips for embossing were cut from a Polycarbonate sheet with titanium scissors. Polycarbonate chips were then placed on a flat PDMS piece and a PDMS stamp, 2”x3” borosilicate glass slide, and a weight were placed on top of the Polycarbonate chips in that order from bottom to top before being heated at 190°C for a time that was dependent on chip thickness.
Bonding: ¼ inch thick Polycarbonate pieces were prepared via cutting with a bandsaw before connection ports were drilled. The pieces were cleaned using Isopropyl alcohol. 2mL of a solution of 5% PVAC dispersed in 1:1 ethanol and acetone mixture was pipetted onto one side of theses polycarbonate pieces and spun coat at 2000 rpm for 30 seconds. The embossed chips were then placed on top of these pieces in a C clamp and heated in the oven for 1 hour at 45°C to bond the pieces.

Results, Conclusions, and Discussions: After optimizing source material and process parameters, a protocol was developed for distortion free PC chip embossing with an adjustable heating time based on chip thickness. In addition, we used a method of solvent bonding that had only been attempted on PLA chips before to successfully bond multiple configurations of two polycarbonate pieces. The reason this room temperature method was chosen was because the final protocol will involve open top functionalization of the microfluidic chip before components are bonded. The resultant chip successfully passed a dye flow test via syringe pump at a flow rate of 300 µL/ hr. Further work is needed to push this chip into a commercial quality testing system; however, the current prototype represents a novel fabrication protocol and a starting point for further microfluidic device mass production.

Acknowledgements (Optional):  Special thanks to Norh Asmare, Ahmadreza Rostamzadeh, Firat Usanmaz, and Professor A. Fatih Sarioglu
Additional thanks to the CMAT program and the Georgia Institute of Technology for funding and supporting this research