마이크로 돌기 구조 표면의 이방성 흐름 특성 평가

Abstract

This study was conducted with the aim of optimizing and evaluating the performance of surfaces with micro-grooves and asymmetric micro-asperities capable of unidirectional flow control for the effectiveness of the manufacture of inclined micro-asperities, mold manufacturing using a high-power diode laser was tried but the limit of the hole inclination angle of the method was confirmed. A mold with a hole inclination angle was manufactured using an ultra-short pulse multi-wavelength laser, and a specimen was successfully manufactured according to changes in various influence factors such as inclination angle, spacing of the micro-asperities and spacing between grooves. The specimen was manufactured using PDMS, and the wettability of the droplets in static and dynamic states of the manufactured specimen was to be evaluated. As a result of measuring the static contact angle, the surfaces with spacing of asperities of 100 μm and 200 μm gives a high contact angle of about 160° due to the Cassie-Baxter state according to the relatively narrow asperity interval. As a result of measuring the dynamic contact angle, the difference in roll off angle according to the inclination direction was not significant at the surface with spacing of asperities of 100 μm due to the narrow asperity interval, but at the surface of 200 μm, the flow resistance was small due to the droplet flow consistent with the asperity tip direction, which result in the smallest contact angle history and roll off angle at 30°. It showed that the anisotropic flow occurs depending on the direction of the surface asperities. To evaluate the droplet flow control for a specimen with curved grooves and micro-asperities, the changes in the forward and backward contact angles of the droplet according to the change in the inclination angle of the specimen were measured. As a result, it was confirmed that the roll off angle increased to about 9 ˚ in the specimen with curved grooves and micro-asperities compared to the specimen with curved grooves due to the increase in contact area between droplets and micro asperities.