Fabricating non-photodefinable polymer microstructures for micro-total-analysis

Fabrication of non-photodefinable polymer materials into microstructures is one of the major challenges for development of functional biomedical microchips. In this paper, we describe a vacuum-assisted microfluidic approach for patterning polydimethylsiloxane (PDMS) microstructures on a solid substrate of a different material. The results show that liquid prepolymer driven by the vacuum-induced differential pressure can fill microchannels at a greatly enhanced rate than that driven by capillary forces. This allows fast patterning of liquid prepolymer into small structures before the polymer becomes too viscous to flow. This approach also eliminates the diffusion of liquid prepolymer into undesired regions. Discrete polymer microstructures can thus be successfully fabricated on a solid substrate. The effectiveness of the fabrication method is demonstrated by creating helical structures, suspended microbridges, and double-layered structures. The characteristic dimensions of the demonstrated structures are less than 10 μm. This approach is expected to facilitate the use of these non-photodefinable polymer microstructures, into miniaturized systems for micro-total-analysis.