The process by which human fingers gives rise to stable contacts with smooth, hard objects is surprisingly slow. Using high-resolution imaging, we found that, when pressed against glass, the actual contact made by finger pad ridges evolved over time following a first-order kinetics relationship. This evolution was the result of a two-stage coalescence process of microscopic junctions made between the keratin of the stratum corneum of the skin and the glass surface. This process was driven by the secretion of moisture from the sweat glands, since increased hydration in stratum corneum causes it to become softer. Saturation was typically reached within 20 s of loading the contact, regardless of the initial moisture state of the finger and of the normal force applied. Hence, the gross contact area, frequently used as a benchmark quantity in grip and perceptual studies, is a poor reflection of the actual contact mechanics that take place between human fingers and smooth, impermeable surfaces. In contrast, the formation of a steady-state contact area is almost instantaneous if the counter surface is soft relative to keratin in a dry state. It is for this reason that elastomers are commonly used to coat grip surfaces.

中文翻译：

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为什么钢笔的握把是橡胶的


人类的手指与光滑、坚硬的物体产生稳定接触的过程出奇地缓慢。使用高分辨率成像，我们发现，当压在玻璃上时，指垫脊线产生的实际接触会随着时间的推移而遵循一级动力学关系。这种演变是皮肤角质层角蛋白与玻璃表面之间形成的微观连接的两阶段合并过程的结果。这一过程是由汗腺分泌水分驱动的，因为角质层水合作用的增加会使其变得更柔软。无论手指的初始湿度状态和施加的法向力如何，通常会在触点加载后 20 秒内达到饱和。因此，经常用作抓握和感知研究中基准量的总接触面积并不能很好地反映人类手指与光滑、不渗透表面之间发生的实际接触力学。相反，如果相对表面相对于干燥状态下的角蛋白较软，则稳态接触区域的形成几乎是瞬时的。正是由于这个原因，弹性体通常用于涂覆抓握表面。