Optimization of micromilled channels for microfluidic applications using gas-blowing-assisted PDMS coating

Abstract

Micromilling is a flexible, inexpensive and rapid prototyping technique for polymer microfluidic devices. However, the applications of microfluidic devices fabricated by micromilling have been compromised by their poor surface quality. In this study, we demonstrated a gas-blowing-assisted (GBA) polydimethylsiloxane (PDMS) coating that is used to reduce the surface roughness of micromilled channels, yielding optical grade channel walls while simultaneously offering high flexibility in channel dimensions and morphology by controlling the coating parameters. In this method, a thin layer of PDMS is coated on the engraved substrate, and then a computer numerical control (CNC)-guided gas-blowing is used to selectively remove surplus PDMS prepolymer in channels, which results in a thin residual and smooth PDMS coating on the walls of channels. With this GBA PDMS coating, the channel surface roughness of below 8 nm could be achieved without the need of advanced polishing equipment or procedures. Furthermore, this method has the capability to fabricate non-rectangular microchannels with different shapes in cross-section depending on the process parameters, which benefits microvascular research and tissue engineering.