UV/ozone modification of poly(dimethylsiloxane) microfluidic channels

Abstract

UV/ozone method of oxidation of poly(dimethylsiloxane) (PDMS) was investigated to enhance microfluidic device performance, i.e., increase electroosmotic flow (EOF) stability, minimize adsorption of analytes in microchannels, etc. PDMS microfluidic devices are easily fabricated at low cost, but high hydrophobicity and poor surface properties make this material inferior to glass or quartz in most high-performance microfluidic applications. PDMS can be converted into a silica-like material by UV/ozone treatment enabling much deeper oxidation of PDMS without crack failures compared to oxygen plasma treatment. In this study application of UV/ozone treatment to fabrication of microfluidic devices has been presented. Specifically, conversion of bulk PDMS by deep penetration and complete oxidation of thick-film membranes by UV/ozone were investigated. Changes of physical properties upon PDMS modification were monitored by FTIR spectroscopy, contact angle measurements, and channel cross-section visualization. Two microfabrication approaches were attempted and compared: microchannels molded in bulk PDMS were oxidized at the surface and sealed, as well as microchannels molded in a 15 μm PDMS membrane followed by sealing against glass and complete UV/ozone oxidation. Improved wettability, enhanced electroosmotic flow, and reduced adsorption properties were observed in the modified PDMS channels.