Design and fabrication of polymer-based microfluidic platforms for BioMEMS applications

The goal of this study is to design and fabricate polymer microfluidic devices for BioMEMS applications. The emphasis is on the design of microfluidic functions and the development of a new packaging technique.;A microfluidic platform was designed on a compact disk (CD) for medical diagnostics, which includes functions such as pumping, valving, sample/reagent loading, mixing, metering, and separation. The fluid propulsion was based on the centrifugal force. A passive capillary valve, which is based on a pressure barrier that develops when the cross-section of the capillary expands abruptly, was used to control the fluid flow. Micromixing was achieved by impinging mixing and bend-induced vortices. Integration of these microfluidic functions was applied in a two-point calibration system for medical diagnostics and a cascade micromixer for protein reconstitution. A specific application was for enzyme-linked immunosorbent assays (ELISA). It has been demonstrated successfully to realize the necessary microfluidic functions for the ELISA process on a CD. The preliminary analysis of rat IgG from hybridoma culture showed that the microchip-based ELISA has the same detection range as the conventional method on the 96-well microtiter plate, and has advantages such as less reagent consumption and shorter assay time over the conventional one.;A new resin-gas injection technique was developed for bonding and surface modification of polymer microfluidic devices. This method can easily bond biochips with complex flow patterns. By adding surface modification agents, the interfacial free energy of the substrate with water can be controlled. Local modification of the channel surface can also be achieved through sequential resin-gas injection in conjunction with the masking technique. For application, this technique was used to form a layer of dry monolithic stationary hydrogel on the walls of a microchannel, serving as a sieving material for electrophoresis separation of DNA fragments. The regent loading, and the electrophoresis separation efficiency of this new technique were compared experimentally with the conventional linear polymer solution method used in the microchannel based DNA sequencing process. It was found that our method has the advantages of more user-friendly operation, easier and faster sample loading, and better separation efficiency.