Mechanical, Materials, and Aerospace Engineering Department, Illinois Institute of Technology, Chicago, IL 60616, USA
Mechanical, Materials, and Aerospace Engineering Department, Illinois Institute of Technology, Chicago, IL 60616, USA.
J R Soc Interface. 2018 Sep 19;15(146):20180551. doi: 10.1098/rsif.2018.0551.
Anisotropic, gecko-inspired, microstructured adhesives are one of the most promising solutions for many applications in robotics and biomedical applications that require controllable adhesives to grip flat surfaces. In such adhesives, normal adhesion is negligible when loaded solely in the normal direction, but becomes available when the adhesive is loaded in shear first. However, much remains to be learned regarding the friction and failure mechanisms of microstructures loaded in shear. In response, we analysed the load-displacement profiles of wedge-shaped microstructured adhesives comprised of nine different silicone elastomers and their mixtures loaded in shear. The results show that the friction profile depends on at least three factors related to material properties: interfacial adhesion strength in the normal direction (work of separation), elastic modulus and the sample's imperfections (e.g. contamination, misalignment and moulding errors). Moreover, the work of separation influences the maximum friction load such that for materials with the same elastic modulus, the strongest interfacial adhesion yields the lowest friction force. To explain this, we suggest that strongly adhering materials will lead to a macroscopic frictional sliding of the array rather than previously reported stick-slip behaviour.
各向异性、仿壁虎、微结构化的粘合剂是许多机器人和生物医学应用中最有前途的解决方案之一，这些应用需要可控制的粘合剂来抓握平坦表面。在这种粘合剂中，当仅在法向加载时，正常粘附可以忽略不计，但当首先在剪切方向加载时，正常粘附变得可用。然而，对于在剪切下加载的微结构的摩擦和失效机制，仍有许多需要了解的地方。有鉴于此，我们分析了由九种不同的硅酮弹性体及其混合物组成的楔形微结构化粘合剂在剪切下的载荷-位移曲线。结果表明，摩擦曲线至少取决于三个与材料特性相关的因素：法向界面粘附强度（分离功）、弹性模量和样品的不完整性（例如污染、不对准和成型误差）。此外，分离功会影响最大摩擦力，使得对于具有相同弹性模量的材料，最强的界面粘附会产生最低的摩擦力。为了解释这一点，我们认为，强粘附的材料会导致阵列的宏观摩擦滑动，而不是以前报道的粘滑行为。
