Liquid repellent properties of patterned surfaces and their applications to polymeric materials

It was studied how liquid repellent properties can be controlled on the basis of roughness at surfaces. Ultrafine-patterned surfaces were prepared by the photolithography. The surfaces were fully covered with fluoroalkyl silane coupling agent by chemical vapor deposition (CVD) for about two hours. Contact angle to water increased as increasing pitch of the pattern. The relation between water contact angle and pitch was well expressed by the Cassie mode, where assumed that the space between solid surface and water was occupied by air. Contact angle to dodecane was neither in agreement with Wenzel nor Cassie's modes. Instead, in the case of dodecane, both modes should be combined to reproduce the experimental results. Hence, it can be claimed that factors such as increase in surface area and formation of air layer at the interface between liquid and surface are important for excellent liquid repellent properties.