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

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.