Effect of surface roughness on the fabrication of electrowetting display cells its electro-optic switching behavior

Electrowetting is a new class of reflective display based on electric field controlled movement of oil/water interface across a hydrophobic layer. The focus of this paper is to fabricate electrowetting cells on a rough hydrophobic surface to study its effect on kinetics of electrowetting. The surface roughening found effective in two ways in the design operation of the electrowetting device: (i) It enhances the coating of photoresist (PR) on the hydrophobic surface, which is normally difficult due to low surface energy of Teflon (ii) the roughness changes the contact angle of the liquid (oil), which in turn changes the electro-optic switching behavior of the device. The kinetics of optical switch was checked by calculating theoretically the white area fraction (WA%), which is a measure of optical switching in electrowetting display by changing the roughness of the hydrophobic surface. The present study showed that the optical performance found to increase with the increase of roughness of the hydrophobic surface.