Analysis on the deflection of thin membrane with a droplet according to the surface tension and elasticity
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TECHNICAL PAPER
Analysis on the deflection of thin membrane with a droplet according to the surface tension and elasticity Hyeon-Gi Ryu1 • Kyoung-Su Park1 Received: 6 December 2019 / Accepted: 10 June 2020 Ó Springer-Verlag GmbH Germany, part of Springer Nature 2020
Abstract Thin membranes that may be exposed to water droplet deposition have been used in various industrial and research fields. Deflection of these membranes by water droplets may greatly affect their characteristics. Therefore, it is important to predict deflection of these thin membranes by water droplets. Here, the contact angle effect of a sessile drop was analyzed by a combination of deformation and surface energy; the deflection of elastomer thin membranes was investigated by experiment and simulation. Circular thin membranes were fabricated comprising various materials (i.e., expanded polytetrafluoroethylene, polytetrafluoroethylene, and polyethylene). Modal characteristics for thin membranes mounted on a ring fixture were measured when all edge points were clamped. Based on the measured fundamental frequency, initial tension was determined in accordance with circular thin membrane vibration theory. A numerical model was derived to describe the water droplet profile and membrane deflection by thermodynamics and mechanical energy. Contact angles and profiles were measured for three types of thin membrane and for various water droplet sizes, using a high-speed camera. Deflections were measured using a laser sensor with water droplets of various sizes and various contact angles, along with various ethanol concentrations on the thin membrane. Experimental results were consistent with simulation results. The degree of nonlinearity could be ignored for thin membranes with water droplet volume of B 200 lL. Maximum deflection of various thin membranes and various contact angles could be predicted using compensation factors. Maximum deflection of the thin membrane could be sufficiently predicted when considering the contact angle effect.
1 Introduction When immiscible fluids come into contact with a solid surface, wettability is defined by the attractive forces of the solid–liquid and solid–air interfacial areas. This interfacial attractive force has been referred to as surface tension, and it can be intuitively regarded as contact angle (De Gennes et al. 2013). The surface tension effect can be easily described between a solid material and an elastomer surface. For example, soft material adhesion effect is similar to a solid adhesion effect (Jensen et al. 2015). A droplet falling from the surface of a closed faucet acts like a pendent water droplet, because the faucet surface tension attracts the water droplet and the droplet surface tension attracts the faucet. To evaluate the surface tension or & Kyoung-Su Park [email protected] 1
Department of Mechanical Engineering, Gachon University, 1342 Seongnamdaero, Sujeong-gu, Seongnam-si 461-701, Gyeonggi-do, Korea
wettability of a material, it is necessa
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