仿生表面液固界面摩擦力的动态调控  

Regulation of Friction Force of a Water Droplet on Bioinspired Surface

作　　者：张晋红 石奎[1] 徐鹏 李倩 薛龙建[1] ZHANG Jin-Hong;SHI Kui;XU Peng;LI Qian;XUE Long-Jian(School of Power and Mechanical Engineering,Wuhan University,Wuhan 430072,China;Department of Mechanical Engineering,Shanxi Polytechnic College,Taiyuan 030006,China)

机构地区：[1]武汉大学动力与机械学院,武汉430072 [2]山西职业技术学院机械工程系,太原030006

出　　处：《应用化学》2022年第1期188-195,共8页Chinese Journal of Applied Chemistry

基　　金：科技部重点研发计划(No.2018YFB1105100);国家自然科学基金(No.51973165)项目资助。

摘　　要：仿生超疏水材料在自清洁、防雾抗冰、油水分离、集水等领域有着重要应用;而在不同疏水状态之间的转换将大大促进仿生超疏水材料在智能技术领域的应用。利用软印刷技术将玫瑰花表面微观结构转印到聚氨酯弹性体PU膜表面,利用机械应力实现表面微结构的动态实时调控,实现了表面微观结构在各向同性与各向异性之间的可逆转换;利用毛细管投影传感技术(MPCP)定量表征了水滴在仿生PU膜表面的摩擦力,详细讨论了PU膜在不同拉伸状态下拉伸量、拉伸方向以及液滴体积和移动速度对液固界面摩擦力的影响。结果表明,仿玫瑰花PU膜的静态接触角和滚动角均非常接近新鲜玫瑰花,保留了玫瑰花的超疏水、高黏附和各向同性的性质。样品拉伸后,表面微结构沿着拉伸方向(D_(S))和垂直方向(D_(V))表现为各向异性,但接触角和滚动角在两个方向无明显区别。但液滴在D_(S)和D_(V)方向的摩擦力大小不同,且对水滴体积具有不同的依赖性,呈现明显的各向异性。随着样品延伸率的增大,水滴在PU膜表面的静摩擦力(F_(S))和动摩擦力(F_(K))明显增大,而增强的幅度同样对方向具有一定的依赖性。沿着D_(S)方向,只有当液滴的移动速度高于1.55 mm/s时,摩擦阻力随着移动速度的增加而减小;而在D_(V)方向,摩擦阻力随着移动速度的增加而减小。本文利用机械应力实现了高黏附超疏水表面液固界面摩擦力在各向同性和各向异性两个状态之间的转变以及液固界面摩擦的调控,为智能润湿性表面的设计、表征和应用提供了新思路。Bioinspired superhydrophobic materials have important applications in the fields,like selfcleaning,anti-fogging,anti-icing,water-oil separation and water collection.The shifting between different hydrophobic states will greatly promote the application in the emerging smart technologies.Here,polyurethane(PU)films with microstructures identical to the rose petal surface were prepared by softlithography.The surface microstructure can be dynamically regulated by mechanical stress,which reversibly shifts the surface microstructure between isotropic and anisotropic states.Monitoring the position of capillary.s projection(MPCP)was used to quantitatively characterize the friction force of water droplets on the surface of PU films.The influences of the stretching(strain and direction),the volume and the moving speed of the droplet on the liquid-solid friction were investigated in detail.PU films very-well replicate the microstructures on rose petals that they have the similar static contact angle and sliding angle as rose petals.The PU films thus are superhydrophobic and isotropic,and show strong adhesion to water droplets.The size and spacing of the microstructures along the stretching direction(D_(S))and the vertical direction(D_(V))change upon the mechanical stretching;however,the water contact angles and sliding angles along the two directions remain same on the surfaces with various elongations.In contact,the friction forces,revealed by CPS,show clear difference along the directions of D_(S) and D_(V),and show clear different dependences on the droplet volume.Increasing the stretching(or in another word the elongation of the sample),the static friction force(F_(S))and dynamic friction force(F_(K))of water droplets on the PU film increase significantly,which also shows a clear direction dependence.Along the D_(S) direction,the frictional resistances decrease monotonically with the increase of the moving speed of the droplet,while in the D;direction,only when the moving speed of the droplet is higher than 1.55 mm/s,the

关 键 词：表面润湿性 接触角 滚动角 摩擦力 毛细管投影传感技术 仿生材料 

分 类 号：O647.[理学—物理化学]