Effects of Low Temperature and Humidity on Contact Angles of Water Droplets on Superhydrophobic Surfaces
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摘要: 超疏水表面的Cassie-Wenzel（C-W）润湿转变已经得到了广泛研究，然而对于覆膜成形的不规则表面来说，环境湿度对润湿转变的影响缺乏足够的探索。通过地面冷环境试验对不同温度、不同湿度诱导水滴静态接触角变化进行研究。结果表明：低温诱导水滴接触角降低，同时使表面发生冷凝现象，温度稳定后湿度成为了影响接触角变化的主要因素；温度可影响水滴冻结延迟时间，进而影响冻结前的接触角。通过水滴的低温和冻结试验可以定量得到温度和湿度对水滴接触角的影响，温度每降低5 ℃，接触角降低5° ± 1.7°；温度稳定后，水滴在相对湿度为88%时接触角每分钟降低2.4° ± 0.7°，在相对湿度为45%时接触角每分钟降低0.9° ± 0.2°。Abstract: The Cassie-Wenzel(C-W) wetting transition on superhydrophobic surfaces has been extensively explored. However, the influence of environmental humidity on wettability transformation of irregular surface formed by film mulch is not sufficiently explored. The static contact angle changes of water droplets induced by different temperature and ambient humidity were studied by ground cold environment test. The results show that low temperature induces the drop contact angle to decrease, and the surface condensation occurs. After the temperature is stabilized, humidity becomes the main factor affecting the change of contact angle The results show that the superhydrophobic surface condenses when the temperature decreases, and humidity becomes the main factor affecting the change of contact angle when the temperature stabilizes. The freezing delay time and contact angle before freezing are affected by different temperature. The effects of temperature and humidity on the contact angle can be quantitatively obtained by low temperature and freezing test of water droplet. The contact angle decreases by 5° ± 1.7° for every 5 °C decrease in temperature. When the temperature is stabilized, the contact angle of water droplets decreases by 2.4° ± 0.7° per minute at 88%RH and by 0.9° ± 0.2° per minute at 45%RH.
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Key words:
- superhydrophobic /
- low temperature /
- humidity /
- contact angle /
- wetting state transition
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图 1 超疏水涂层制备流程示意图
Figure 1. Schematic diagram of preparation process of superhydrophobic coating
图 2 显微镜拍摄超疏水涂层表面形貌
Figure 2. Microscope photographing of surface morphology of superhydrophobic coatings
图 3 显微镜拍摄超疏水涂层表面3D形貌
Figure 3. 3D topography of superhydrophobic coating surface captured by microscope
图 5 低温冷凝对水滴接触角影响
Figure 5. Effect of low temperature condensation on the contact angle of water droplets
图 6 不同环境湿度下接触角变化
Figure 6. Variation of contact angle under different ambient humidity
图 7 不同环境湿度下接触角降低速率
Figure 7. Contact angle reduction rate under different ambient humidity
图 8 不同基板温度下水滴接触角和温度的关系
Figure 8. Relationship between water droplet contact angle and temperature when the substrate temperature is different
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