Evidence for van der Waals adhesion in gecko setae
Evidence for van der Waals adhesion in gecko setae
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DOI：
10.1073/pnas.192252799
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发表时间：
2002-09-17
影响因子：
11.1
通讯作者：
Full, RJ
中科院分区：
文献类型：
--
作者：
Autumn, K;Sitti, M;Full, RJ
壁虎已经进化出了一种最通用、最有效的粘合剂。一个多世纪以来，壁虎脚趾上数以百万计的毛的干燥粘附机制一直是科学研究的焦点。我们提供了壁虎刚毛在范德华力作用下干燥粘附的第一个直接实验证据，并拒绝使用依赖于高表面极性的机制，包括毛细粘附。活的东卡壁虎的脚趾是高度疏水性的，并且在强疏水性和强亲水性的极化表面上粘附得同样好。在微机电系统力传感器的疏水性和亲水性表面上，单个孤立壁虎集的粘附效果相同。范德华机制表明壁虎刚毛的显著粘附特性仅仅是刚毛尖端的大小和形状的结果，而不受表面化学的强烈影响。理论预测，更大的附着力仅仅是通过细分刚毛来增加表面密度，并提出了壁虎、蜥蜴、石龙子和昆虫中干燥粘附微观结构重复、趋同进化的可能设计原则。使用标准粘附模型和我们测量的力的估计非常接近于预测东京壁虎群的尖端尺寸。我们通过使用两种不同材料制成的纳米尖端的物理模型验证了对尺寸而不是表面类型的依赖。这两种人造刚毛尖端都像预期的那样粘住了，并为制造第一个干燥、粘接的微结构提供了途径。
Geckos have evolved one of the most versatile and effective adhesives known. The mechanism of dry adhesion in the millions of setae on the toes of geckos has been the focus of scientific-study for over a century. We provide the first direct experimental evidence for dry adhesion of gecko setae by van der Waals forces, and reject the use of mechanisms relying on high surface polarity, including capillary adhesion. The toes of live Tokay geckos were highly hydrophobic, and adhered equally well to strongly hydrophobic and strongly hydrophilic, polarizable surfaces. Adhesion of a single isolated gecko seta was equally effective on the hydrophobic and hydrophilic surfaces of a microelectro-mechanical systems force sensor. A van der Waals mechanism implies that the remarkable adhesive properties of gecko setae are merely a result of the size and shape of the tips, and are not strongly affected by surface chemistry. Theory predicts greater adhesive forces simply from subdividing setae to increase surface density, and suggests a possible design principle underlying the repeated, convergent evolution of dry adhesive microstructures in gecko, anoles, skinks, and insects. Estimates using a standard adhesion model and our measured forces come remarkably close to predicting the tip size of Tokay gecko seta. We verified the dependence on size and not surface type by using physical models of setal tips nanofabricated from two different materials. Both artificial setal tips stuck as predicted and provide a path to manufacturing the first dry, adhesive microstructures.