Abstract
This thesis develops the three-dimensional (3D) polymer microfabrication techniques with UV lithography and black photoresist shadow method for applications of microoptic biosensors and microfluidic reactors. It mainly consists of (1) a monolithic integration method to fabricate a total-internal- reflection (TIR) based biosensor with microprism arrays for fluorescence sensing, and (2) a planar 3D microfluidic flow-focusing device (MFFD) to produce monodisperse single/double emulsions in a closed/open microfluidic system. (1) Microoptic biosensors: we propose a monolithic TIR-based biosensor, which integrates a microfluidic chamber, polymer-based optics, and planar waveguides into a high-throughput platform. To fabricate the microprism array, a technology employing glycerol-compensated oblique-exposure is employed. Microprism arrays with various inclined surface angles on the planar optical waveguide have been successfully fabricated. Multiple total internal reflection spots can be observed, through this monolithically integrated optical system simultaneously. Real-time Brownian motions of fluorescent microspheres excited by the evanescent wave under this system are captured for motion analysis. The unique fabrication/integration aspects including on-chip micro-optics simplify current TIR optical configurations and could be integrated into a microsystem. (2) Microfluidic reactors: we present a planar 3D-MFFD that can produce monodisperse single/double emulsions in a closed/open microfluidic system. The proposed 3D MFFD can produce single emulsions for both water-in-oil (W/O) and oil-in-water (O/W) droplets utilizing the same device. Double emulsions containing one to several internal droplets were successfully produced in the closed channel configuration. In addition, we demonstrated for the first time the feasibility of forming W/O droplets and polymer particles by means of in-situ photopolymerization in an open channel configuration by withdrawing the fluid from the outlet channel. Bioconjugation of the carboxylated copolymer (EGDMA/AA) particles with the anti-rabbit IgG-Cy3 conjugates was also successfully achieved. The unique fabrication of the 3D MFFD device utilizing SU-8 resist overcomes problems for current 2D MFFD and provides flexibility for Lab-on-Chip microsystem.