Surface modification of SiO2 microchannels with mPEG-silane to stabilize flow performance

Passive microfluidic devices primarily use capillary action to manipulate fluids in micro- and nanochannels. One of the most widely used materials for this type of device is SiO2 because of its inherent hydrophilicity and high mechanical strength. However, this hydrophilic behavior is not permanent and can degrade over time, promoting bubble formation when filled with aqueous solutions and negatively affecting fluid flow. In this study, we investigate a single-step, covalent, and hydrolytically stable surface modification of chemical vapor deposited SiO2 using methoxy poly(ethylene glycol) silane with molecular weights of 1000 and 2000. By grafting a permanent and stable hydrophilic layer, we report a stabilization of the apparent flow speed and reduced bubble formation when measured over a period of two weeks on treated microchannels.