Executive Summary : | Advances in microfabrication and microfluidics have led to the development of miniaturized lab-on-a-chip devices for various applications, including electrophoretic separations, nucleic acid analysis, counting and sorting of biological cells, and point-of-care diagnostics. PDMS has become the material of choice for fabricating microfluidic devices due to its good optical clarity and permeability to oxygen. PDMS microdevices are fabricated using replica molding, where a mixture of pre-polymer and cross-linker is poured on a master mold. However, this requires expensive clean-room techniques and highly trained manpower. Various rapid prototyping methods have been proposed for low-cost and rapid fabrication of templates for PDMS devices, but all have limited resolution of order 100 µm. Due to the resource-intensive nature of photolithography and its lack of rapid prototyping capability, a customizable technique for rapid fabrication of micrometer-resolution templates for PDMS devices is necessary. This project proposes a novel, rapid prototyping method for fabricating master molds for PDMS microfluidic devices using electrohydrodynamic (EHD) jetting. An EHD jet is formed when a liquid issuing out of a nozzle is accelerated and stretched by electrostatic forces due to an applied potential difference between the nozzle and a collector plate. The proposed process involves depositing an EHD jet of a polymeric solution on a precisely-controlled translating substrate, then using the printed templates to fabricate PDMS microdevices using replica molding. The fabricated PDMS microdevices will be demonstrated for various applications, including microchip electrophoresis, imaging flow-cytometry for biological cell analysis, electrokinetic mixing of fluids, and droplet generation. |