Molding of Deep Polydimethylsiloxane Microstructures for Microfluidics and Biological Applications

TLDR

PDMS structures are widely used in microfluidics and biological applications. The study demonstrates microfabrication of deep (>25 μm) PDMS microstructures via replica molding from microfabricated silicon substrates. The authors compared deep plasma etching of SOI wafers and photolithographic patterning of a spin‑coated photoplastic layer to fabricate silicon molds for PDMS replica molding. The inexpensive photoplastic method produced replication fidelity comparable to high‑resolution SOI wafers, though mechanical stability limited the PDMS structures, and the technique enabled selective delivery of distinct cell suspensions to create micropatterned tissue cultures.

Abstract

Here we demonstrate the microfabrication of deep (>25 μm) polymeric microstructures created by replica-molding polydimethylsiloxane (PDMS) from microfabricated Si substrates. The use of PDMS structures in microfluidics and biological applications is discussed. We investigated the feasibility of two methods for the microfabrication of the Si molds: deep plasma etch of silicon-on-insulator (SOI) wafers and photolithographic patterning of a spin-coated photoplastic layer. Although the SOI wafers can be patterned at higher resolution, we found that the inexpensive photoplastic yields similar replication fidelity. The latter is mostly limited by the mechanical stability of the replicated PDMS structures. As an example, we demonstrate the selective delivery of different cell suspensions to specific locations of a tissue culture substrate resulting in micropatterns of attached cells.