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.

中文翻译：

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关于壁虎刮刀剥离中临界分离角的存在——使用粘附摩擦模型的数值研究

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。显示“摩擦粘附”行为，直到现在仅从刚毛到脚趾水平观察到，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。