Atmospheric pressure microplasmas for modifying sealed microfluidic devices

A dc microdischarge technique for the chemical modification of microchannel walls is reported. In this method, an atmospheric pressure plasma is ignited directly in the channels of assembled microfluidic devices. Our results show that strongly hydrophilic or hydrophobic properties are imparted to the walls of polystyrene microchannels by the appropriate selection of a plasma gas. This localized tuning of the surface and wetting properties is expected to be useful in the manufacture of microfluidic channels in a variety of substrates. Small area x-ray photoelectron spectroscopy was used to identify oxygen and fluorine on polystyrene surfaces resulting from the plasma treatments. (C) 2004 American Institute of Physics.