甲醇/水混合溶液在蝴蝶翅表面的润湿行为

使用视频光学接触角测量仪和扫描电子显微镜研究了甲醇/水混合溶液在蝴蝶翅表面的润湿行为,根据Cassie方程分析了甲醇对蝴蝶翅表面的润湿机理。结果表明,蝴蝶翅表面具有较强的疏水性(蒸馏水接触角为134.0°～159.2°)和疏甲醇性(45%甲醇溶液接触角为91.3°～128.5°)。甲醇溶液在32种蝴蝶翅表面润湿和铺展的临界体积分数分别为50%和70%。在黄钩蛱蝶(Polygonia c-aureum)翅表面,当甲醇体积分数<45%时,液滴在纳米级结构上的体相力大于表面力,液体填满纳米级缝隙,而在微米级结构上体相力小于表面力,液滴由微米级结构支撑,翅表面不发生润湿;当45%≤甲醇体积分数<65%时,液滴在纳/微米级结构上的体相力均大于表面力,液滴塌陷;当甲醇体积分数≥65%时,翅表面发生润湿,由复合接触转为湿接触。

Wetting behaviors of methanol/water solution on butterfly wing surface

The wetting behaviors of methanol/water solution on butterfly wing surface were investigated using a video-based contact angle meter and a scanning electron microscope,and the mechanism of wetting by methanol on butterfly wing surface was discussed by Cassie model.The butterfly wing surfaces display high hydrophobicity(contact angles of distilled water 134.0°～159.2°) and resistant ability against wetting by methanol solution(contact angles of 45% methanol solution 91.3°～128.5°).On wing surfaces of 32 butterfly species tested,the critical concentrations for wetting and spreadingwetting of methanol solution are 50% and 70%,respectively.On wing surface of Polygonia c-aureum,when methanol concentration is lower than 45%,the body force of a droplet is bigger than the surface force on nanometer-structures,liquid fills up the nanometer-grooves;while the body force on micrometer-structures is smaller than the surface force,droplets are upheld by micrometer-structures,wetting does not occur on the wing surface.When 45%≤methanol concentration<65%,the body force of a droplet is bigger than the surface force on both nanometer-and micrometer-structures,droplets collapse.When methanol concentration is increased to 65%,the wing surfaces are wetted,composite contact is transferred to wet contact.