The adhesion paradox refers to the observation that for most solid objects no adhesion can be detected when they are separated from a state of molecular contact. The adhesion paradox results from surface roughness, and we present experimental and theoretical results that show that adhesion in most cases is “killed” by the longest-wavelength roughness. In addition, adhesion experiments between a human finger and a clean glass plate were carried out, and for a dry finger no macroscopic adhesion occurred. We suggest that the observed decrease in the contact area with increasing shear force results from nonadhesive finger-glass contact mechanics, involving large deformations of complex layered material.

中文翻译：

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附着力悖论：为什么通常对于宏观固体观察不到附着力

粘附悖论指的是，对于大多数固体物体，当它们与分子接触状态分开时，就无法检测到粘附。附着力悖论是由表面粗糙度引起的，我们提供的实验和理论结果表明，在大多数情况下，附着力会被最长波长的粗糙度“杀死”。另外，进行了人的手指与干净的玻璃板之间的粘附实验，并且对于干手指没有宏观的粘附发生。我们建议观察到的接触面积随剪切力的增加而减小是由于非粘性手指-玻璃接触力学引起的，涉及复杂层状材料的大变形。