We present a simple and economical method to produce a potential open microfluidic polymeric device. Biomimetic superhydrophobic surfaces were prepared on polystyrene using a phase separation methodology. Patterned two-dimensional channels were imprinted on the superhydrophobic substrates by exposing the surface to plasma or UV--ozone radiation. The wettability of the channels could be precisely controlled between the superhydrophobic and superhydrophilic states by changing the exposure time. The ability of superhydrophilic paths to drive liquid flows in a horizontal position was found to be significantly higher than for the case of hydrophilic paths patterned onto smooth surfaces.