Effect of Equilibrium Contact Angle on Drainage Property at Microperiodic Structure with Staggered Pillar Array

Abstract

Keywords: periodic structure, drainage property, equilibrium contact angle, sliding angle, staggered array, micro-electromechanical systems (MEMS) The purpose of this research is to clarify the effects of the equilibrium contact angle on the drainage property of water from microperiodic structures. Resin samples with 3 different equilibrium contact angles were fabricated by lithography and the UV nanoimprint technique. To consider the effect of the Cassie-Baxter and Wenzel states on drainage property, four types of microperiodic structures with varying aspect ratios were fabricated. Thus, in total, 12 test pieces, each consisting of a staggered pillar array, were used. We attempted to improve the drainage property by optimizing the microperiodic structure. A tilted plate method was modified to evaluate these microperiodic structures. From the results, the sliding angle and sliding velocity reached 14° and 171.9 mm/s, respectively, when a material with a sliding angle of 65° on a smooth surface was used. A promising result is that the threshold level for hydrophobicity introduced by the microperiodic structures was below 90° for a water droplet in the Cassie-Baxter state.