Surface nanostructuring of biocompatible polymer for wettability control in MEMS

We present a low-potential method to control surface roughness of doped polypyrrole through redox-induced transformation in surface morphology. By varying the electric potential of as-deposited doped polypyrrole in aqueous sodium dodecylbenzene sulfonate (0.1M) from -0.6 to +1.5V (vs. Ag/AgCl), doped polypyrrole transforms from being a hydrophilic film (60deg contact angle) to a hydrophobic film (107deg contact angle). Atomic force microscope measurements verify that the surface morphologies of doped polypyrrole, when subject to applied potentials from -0.6V to +1.5V, change from smooth (average roughness of 3.1 nm) to rough (average roughness of 31.1 nm), representing a 10-fold increase in surface roughness. Based on these evidence, we postulate that the degree of oxidation strongly influence surface roughness.