ABSTRACT

A continuum-based computational contact model is employed to study coupled adhesion and friction in gecko spatulae. Nonlinear finite element analysis is carried out to simulate spatula peeling from a rigid substrate. It is shown that the “frictional adhesion” behavior, until now only observed from seta to toe levels, is also present at the spatula level. It is shown that for sufficiently small spatula pad thickness, the spatula detaches at a constant angle known as the critical detachment angle irrespective of the peeling and shaft angles. The spatula reaches the same energy states at the jump-off contact point, which directly relates to the invariance of the critical detachment angle. This study also reveals that there is an optimum pad thickness associated with the invariance of the critical detachment angle. It is further observed that the sliding of the spatula pad is essential for the invariance of the critical detachment angle. Further, it is found that the invariance of the critical detachment angle is unaffected for a wide range of spatula shaft lengths.

摘要

采用基于连续体的计算接触模型来研究壁虎刮刀中的耦合粘附和摩擦。进行非线性有限元分析以模拟刮刀从刚性基材上剥离。结果表明，迄今为止仅从刚毛到脚趾水平观察到的“摩擦粘附”行为也存在于刮刀水平。结果表明，对于足够小的刮刀垫厚度，刮刀以恒定角度分离，称为临界分离角度，而与剥离角度和轴角度无关。刮刀在跳跃接触点处达到相同的能量状态，这直接关系到临界分离角的不变性。该研究还表明，存在与临界分离角的不变性相关的最佳衬垫厚度。进一步观察到，抹刀垫的滑动对于临界分离角的不变性是必不可少的。此外，发现临界分离角的不变性对于大范围的刮刀轴长度不受影响。