Spatially controlled silica coating in poly(dimethylsiloxane) microchannels with the sol-gel process

Abstract

This study presents spatially controlled silica coating in poly(dimethylsiloxane) (PDMS) microchannels using the well-known sol-gel process. First, the corona discharge between two Pt electrodes inserted into the microchannels generated silanol groups at the desired location for further modifications. Next, the cross-linking of the silanol groups with silica sol produced a chemically bonded silica surface in the PDMS microchannels. After any remaining unreacted silica sol was removed from the channels with organic solvents, a spatially patterned glass-like surface was observed on the PDMS microchannels. The introduced hydrophilicity and chemical stability of the silica coated PDMS was characterized with various analytical techniques including contact angle analysis, charge-coupled device (CCD) imaging, scanning electron microscopy (SEM), electro-osmotic flow (EOF) mobility measurement, neutral dye BODIPY/organic solvents absorption test and capillary gel electrophoresis. The water contact angle of the silica coated PDMS decreased, and the absorption of BODIPY was substantially suppressed in the silica coated PDMS microchannels while the native ones exhibited an increased fluorescent background signal within 10 min after BODIPY injection. The EOF of the silica coated surface was one order of magnitude higher than the ones with the native PDMS surface for a wide range of pHs. Polyacrylamide gel was immobilized in the silica coated PDMS microchannels, and a DNA ladder was successfully separated in the microchannel. PDMS microfluidic devices with enhanced wettability and stability can be used in multistep chemical syntheses and in various bio- and medical technologies. (C) 2016 Elsevier B.V. All rights reserved.