Electrically Controlled Wetting and Dewetting Transition on Silicon Micro-Pillar Arrays

We investigate here electrically-controlled wetting and dewetting on rough surfaces comprised of silicon micro-pillars coated with a hydrophobic material. Electro-wetting experiments indicate that water droplets wet the micro-array when the applied voltage is raised beyond a threshold value. When the applied bias is removed, the water droplets can be made to partially dewet the surface and revert back into a stable hydrophobic state by appropriate design of the porosity of the micro-array, the aspect ratio of the micro-pillars and the wetting property of the coating material. Such electrically-controlled wetting of hydrophobic (rough) surfaces can have significant impact in micro-fluidic and lab-on-chip applications.