Department of Mechanical Engineering, University of California, Santa Barbara, California 93106, United States.
Langmuir. 2013 Aug 27;29(34):10881-90. doi: 10.1021/la400835n. Epub 2013 Aug 12.
The importance of loading and unloading procedures has been shown in a variety of different methods for biological dry adhesives, such as the fibers on the feet of the Tokay gecko, but biomimetic dry adhesives have yet to be explored in a similar manner. To date, little work has systematically varied multiple parameters to discern the influence of the testing procedure, and the effect of the approach angle remains uncertain. In this study, a synthetic adhesive is moved in 13 individual approach and retraction angles relative to a flat substrate as well as 9 different shear lengths to discern how loading and unloading procedures influence the preload, adhesion, and shear/friction forces supported. The synthetic adhesive, composed of vertical 10 μm diameter semicircular poly(dimethylsiloxane) fibers, is tested against a 4 mm diameter flat glass puck on a home-built microtribometer using both vertical approach and retraction tests and angled approach and retraction tests. The results show that near maximum adhesion and friction can be obtained for most approach and retraction angles, provided that a sufficient shear length is performed. The results also show that the reaction forces during adhesive placement can be significantly reduced by using specific approach angles, resulting for the vertical fibers in a 38-fold increase in the ratio of adhesion force to preload force, μ', when compared to that when using a vertical approach. These results can be of use to those currently researching gecko-inspired adhesives when designing their testing procedures and control algorithms for climbing and perching robots.
装卸程序的重要性已经在各种不同的生物干粘合剂方法中得到了证明，例如壁虎脚上的纤维，但仿生干粘合剂尚未以类似的方式进行探索。迄今为止，很少有工作系统地改变多个参数来辨别测试程序的影响，并且接近角的影响仍然不确定。在这项研究中，将一种合成粘合剂相对于一个平面基底以 13 个单独的接近和缩回角度以及 9 个不同的剪切长度移动，以了解装卸程序如何影响预载、附着力和剪切/摩擦力。合成粘合剂由垂直的 10 μm 直径半圆形聚二甲基硅氧烷纤维组成，在自制的微摩擦仪上使用垂直接近和缩回测试以及倾斜的接近和缩回测试对 4 毫米直径的平面玻璃球进行测试。结果表明，在大多数接近和缩回角度下，都可以获得接近最大的附着力和摩擦力，只要进行足够的剪切长度即可。结果还表明，通过使用特定的接近角度可以显著降低粘合过程中的反作用力，对于垂直纤维，与使用垂直接近相比，附着力与预载力的比值 μ'增加了 38 倍。这些结果对于当前研究壁虎启发的粘合剂的人在设计其攀爬和栖息机器人的测试程序和控制算法时可能会有所帮助。
