基于树蛙脚掌的仿生六棱柱表面边界摩擦研究  

Boundary friction force of tree frog's toe pads and bio-inspired hexagon pillar surface

作　　者：张力文[1] 陈华伟[1] 张鹏飞[1] 张德远[1] 

机构地区：[1]北京航空航天大学机械工程及自动化学院,北京100191

出　　处：《科学通报》2016年第23期2596-2604,共9页Chinese Science Bulletin

基　　金：国家自然科学基金(51175020);国家自然科学基金重大项目(51290292)资助

摘　　要：湿润环境下软材料的摩擦受固液气多介质作用,一直都是摩擦理论的难点.师法自然,我们从自然界获取灵感,由树蛙脚掌能在湿环境中产生极强的摩擦力,来研究软材料在湿环境中的摩擦特性.本文表征了树蛙脚掌的结构和摩擦力,发现在边界摩擦状态下,界面间极薄的液膜有助于增大摩擦力.在树蛙脚掌湿摩擦力的启发下,设计制造出了一种仿生六棱柱增摩表面.通过对摩擦力表征发现,其边界摩擦能达到干摩擦的50倍.与光滑表面相比,仿生六棱柱表面能够产生稳定且持久的边界摩擦力,六棱柱表面亲水比疏水也有着更优异的边界摩擦性能.该研究结论有助于人们进一步认识软材料的湿摩擦机理,可以进一步帮助设计制造更强的湿吸附仿生表面.In our daily life, there is growing use of polymer soft materials, such as rubber and silica gel. In some circumstances, their wet anti-skidding property plays an important role, e.g., rubber tires on car, windscreen wiper and rubber gloves. Its friction under the wet environment is difficult to study since the interaction effect of fluid, capillary effect and soft solid coupling together. As millions years of evolution, creatures have evolved some special soft skins to attach to all kinds of surfaces. Inspired from mother nature, as the toe pad of the tree frog can greatly attach to wet surface, it was used to study the wet friction theory of soft materials. The structure of its toe pad has been characterized by SEM images. The toe surface was constructed by arrayed pillars with a height of 5 ？m, circumcircle diameter of 10 ？m and gap of 1 ？m. About half of these pillars was hexagon, and the rest was pentagon, heptagon, and quadrangle. The friction of toe pads has been tested with consecutive sliding steps on dry substrates. Its friction increases with secretion decreasing and boundary friction formed just like the friction tests on human skin. Under the inspiration of tree frog＇s toe pads, we designed and fabricated a bio-inspired soft surface（PDMS） with hexagon pillar array. With liquid between contact area decreasing from wet to dry condition, its friction shows a peak value, which is similar to the friction of tree frog＇s toe pads. During boundary friction condition, the value can be 50 times higher than dry friction. The liquid between contact interface forms strong capillary force to rise friction as it can be regarded as extra normal force. Comparing to smooth surface, bio-inspired surface can maintain stable and long term boundary friction since the micro-pillars can separately deform to steady friction and the channels can hold more liquid than smooth surface. As hydrophilic hexagon pillar surface can quickly spread liquid through channels to create uniform thin liquid films between contac

关 键 词：树蛙 黏液 边界摩擦 仿生表面 湿摩擦 

分 类 号：Q811[生物学—生物工程]