Department of Mechanical Engineering, University of Alberta, Edmonton, AB T6G2G8, Canada.
Bioinspir Biomim. 2013 Dec;8(4):044002. doi: 10.1088/1748-3182/8/4/044002. Epub 2013 Oct 4.
We demonstrate how introducing a deliberate defect on the overhanging caps of strongly adhering mushroom shaped dry adhesive fibers can produce directional adhesion behavior. We find that the shape and location of this defect controls both the total adhesion force and the degree of directionality for these bio-inspired adhesives. Linear beam theory is used to demonstrate how the application of a shear load to a fiber in tension can create a small compressive load to an asymmetric crack, thereby delaying adhesion failure and producing directional adhesion, and the theory is confirmed with finite element models and empirical data. Anisotropic adhesives have been fabricated and tested and can demonstrate normal adhesion force up to ~250 kPa with a shear displacement of 15 µm away from the defect and as small as ~5 kPa when sheared the same amount towards the defect.
我们展示了如何在强烈附着的蘑菇形干式胶粘剂纤维的悬垂帽上引入故意缺陷，从而产生定向附着行为。我们发现，该缺陷的形状和位置控制了这些仿生胶粘剂的总粘附力和定向程度。线性梁理论用于演示如何对纤维施加剪切载荷可以在不对称裂缝上产生小的压缩载荷，从而延迟粘附失效并产生定向粘附，并且该理论通过有限元模型和经验数据得到了证实。已经制造和测试了各向异性胶粘剂，当从缺陷处剪切 15 µm 时，它们可以表现出高达约 250 kPa 的正常粘附力，而当向缺陷处剪切相同量时，它们的粘附力可以小至约 5 kPa。
