High-resolution patterning and transfer of thin PDMS films: fabrication of hybrid self-sealing 3D microfluidic systems

This paper describes the fabrication procedure for a hybrid elastomer-Si structure. The procedure comprises embossing and curing a thin film in poly(dimethylsiloxane) (PDMS) with vias in the 30-micrometer regime, followed by a double transfer, first to an intermediate substrate and then, with registration, to the micromachined Si structure. A well-defined adhesion between the PDMS film, the mold, the transfer substrate and the target wafer is key to each successful transfer, and plays a crucial role in the efficient removal of nanometer-thick residual membranes that systematically obstruct vias formed by embossing. Inhibition of the cross-linking of the PDMS pre-polymer in the presence of SU-8 photoresist was observed, and overcome for our case. We fabricated hybrid PDMS-Si microfluidic systems that can be sealed reversibly on any smooth and flat substrate, and filled with different solutions.