| 微矩形凹槽表面液滴各向异性浸润行为的研究 |
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| 引用本文： | 乔小溪,张向军,陈平,田煜,孟永钢.微矩形凹槽表面液滴各向异性浸润行为的研究[J].物理学报,2020(3):199-205. |
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| 作者姓名： | 乔小溪 张向军 陈平 田煜 孟永钢 |
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| 作者单位： | 北京科技大学机械工程学院;清华大学摩擦学国家重点实验室 |
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| 基金项目： | 国家自然科学基金(批准号:51905032);中央高校基本科研业务费(批准号:FRF-TP-18-012A2);国家重点研发计划(批准号:2018YFC0810500)资助的课题~~ |
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| 摘 要： | 受自然界启发,仿生微结构被广泛用于调控固-液界面的性质.研究显示,液滴在微结构表面的各向异性浸润行为可用于实现微流动方向和速度的控制,且其各向异性浸润与微结构的尺寸和分布等密切相关.本文研究了微矩形凹槽尺寸对液滴各向异性浸润行为的影响规律.结果显示,液滴沿平行沟槽的方向具有较小的运动阻力、易铺展,因此具有较小接触角;而垂直于沟槽方向,由于沟槽的阻隔作用具有较大运动阻力,因而具有较大接触角,并且在垂直方向液滴的浸润过程是三相线一系列钉扎和跳跃行为.在微矩形凹槽表面,液滴沿平行方向接触角θ//与肋板宽度R和凹槽宽度G密切相关,其值与表面固体面积比成反比;而垂直于沟槽方向的接触角θ⊥随肋板宽度R和凹槽宽度G变化基本保持不变.同时各向异性液滴的变形比L/W、特征方向接触角比值θ⊥/θ//与表面固体面积比成正比.研究结果有助于加深理解微结构表面浸润行为的机制,并为微矩形凹槽在微流动控制方向的应用提供技术支持.
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| 关 键 词： | 微矩形凹槽 各向异性浸润 接触角 钉扎效应 |
Influences of micro-groove size on surface anisotropic wetting behaviors |
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| Qiao Xiao-Xi,Zhang Xiang-Jun,Chen Ping,Tian Yu,Meng Yong-Gang.Influences of micro-groove size on surface anisotropic wetting behaviors[J].Acta Physica Sinica,2020(3):199-205. |
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| Authors: | Qiao Xiao-Xi Zhang Xiang-Jun Chen Ping Tian Yu Meng Yong-Gang |
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| Affiliation: | (School of Mechanical Engineering,University of Science and Technology Beijing,Beijing 100083,China;State Key Laboratory of Tribology,Tsinghua University,Beijing 100084,China) |
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| Abstract: | Biomimetic microstructure has been used widely in the fields of microfluidics,micro-mixers,flow drag reduction,tribology,etc.When solid surface is modified with microstructure,it will inevitably influence the solid-liquid interfacial behaviors,such as adhesion,surface wetting,shear viscous resistance,and interfacial slip.Surface anisotropic wetting can be achieved by using either of anisotropic surface microstructure and chemically heterogeneous patterned surface,or both of them.And anisotropic wetting properties can be used to control the micro-flowing behaviors,like mixing,flowing direction and speed.The effect of microstructure on the surface wetting behavior is closely related to the size,shape and arrangement of microstructure.In the paper,the influence of micro-groove size on liquid anisotropic wetting behavior is studied.The results indicate that the droplet wetting state of the patterned surface used is Cassie state.According to the experimental results,we can see that the liquid flows easily along the groove direction with small motion resistance,thus resulting in a small contact angle.While the water droplet has a higher flowing resistance in the direction perpendicular to the groove direction due to the energy barrier caused by micro-groove,thus showing a larger contact angle.Meanwhile,the water droplet shows pinning and jump behavior during the spreading in the direction perpendicular to the micro-groove direction.The contact angle along the micro-groove direction θ//increases with groove width G increasing,and decreases with ridge width R increasing,which means that the parallel direction contact angle θ//is inversely proportional to the solid fraction R/(R+G).And the experimental contact angle θ//shows good consistence with that obtained from theoretical Cassie model.While the contact angle of water droplet perpendicular to groove direction θ⊥almost keeps no change with groove width G nor ridge width R.Both the droplet deformation ratio L/W and contact angle ratio of the two featured direction θ⊥/θ//are proportional to the solid fraction R/(R+G).The water droplet shows anisotropic wetting behaviors,which means that the liquid motion resistances are different in these directions.The high droplet deformation ratio L/W and the high contact angle ratio θ⊥/θ//correspond to the large difference in motion resistance.And surface wetting behavior has a great influence on the micro-flowing behavior.Thus,the micro-flowing behavior can be regulated by changing the microgroove size.The present research can conduce to the understanding the wetting mechanism and flowing behaviors of liquid droplet on patterned surface. |
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| Keywords: | micro-groove anisotropic wetting contact angle pinning effect |
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