Studies On Fabrication And Surface Modification Of Thermoplastic Microfludic Chips And Applications In Chip-based DNA Analysis

Thermoplastic microfluidic chips have recently attracted considerable attention because of their favorable mechanical and chemical properties, low cost, ease of fabrication, versatility for physical and chemical surface modification, biocompatibility, and easy integration with other components. Surface chemistry is of significance in chip-based microfluidic devices especially in highly miniaturized and integrated systems due to the high surface area-to-volume ratio. However, the development of routine, simple, well-defined surface modification protocols for thermoplastic microfluidic chips is still in its infancy, being yet a relatively weak link in microfluidic analysis. With the development of the fabrication and surface modification for microfluidic chips, the application of microfluidic analysis, especially in life science will become focus points because of the need for analysis of genetic function and structure in the post-genomic era. In this thesis, a simple hot embossing method was developed for the fabrication of poly(methyl methacrylate) (PMMA) or polycarbonate (PC) microfluidic chips. A simple and robust static adsorptive (dynamic) coating method was developed for PMMA or PC chips, and even silanized glass chips using 2% hydroxyethyl cellulose (HEC) as both the coating agent and sieving matrix for the chip-based capillary gel electrophoresis (CGE) separation of DNA restriction fragments. High speed, high resolution, reproducibility separation of DNA fragments and PCR products has been obtained in coated PMMA or PC chips with diode laser induced fluorescence detection.A cheap commercial pellet press was modified to perform hot embossing for the fabrication of PMMA or PC microfluidic chips, after installing devices for temperature control and water cooling. The channel networks were formed through hot compression molding with microfabricated silicon and glass masters, and the chips enclosed using thermal press bonding with a blank PMMA or PC wafer using the embossing system. CCD images of microchannels and SEM images of open channels on the substrates and the cross section of chips were given to show the effectiveness of the procedure. The electroosmotic flow and voltage-ampere curves of the PMMA chips corresponded to those reported in the literature. The performance of the PMMA chips was demonstrated in 11 consecutive electrophoretic separations of Cy5 from byproducts in about 70 min with a fluorescence intense precision of 2.2% RSD, a migration time precision of 1.4% RSD and an efficiency of 7.4 × 10~4 plates/m at...