Department of Mechanical Engineering, University of California, Berkeley, California 94720, USA.
Langmuir. 2011 Sep 20;27(18):11278-81. doi: 10.1021/la202085j. Epub 2011 Aug 23.
Natural gecko array wearless dynamic friction has recently been reported for 30,000 cycles on a smooth substrate. Following these findings, stiff polymer gecko-inspired synthetic adhesives have been proposed for high-cycle applications such as robot feet. Here we examine the behavior of high-density polyethylene (HDPE) and polypropylene (PP) microfiber arrays during repeated cycles of engagement on a glass surface, with a normal preload of less than 40 kPa. We find that fiber arrays maintained 54% of the original shear stress of 300 kPa after 10,000 cycles, despite showing a marked plastic deformation of fiber tips. This deformation could be due to shear-induced plastic creep of the fiber tips from high adhesion forces, adhesive wear, or thermal effects. We hypothesize that a fundamental material limit has been reached for these fiber arrays and that future gecko synthetic adhesive designs must take into account the high adhesive forces generated to avoid damage. Although the synthetic material and natural gecko arrays have a similar elastic modulus, the synthetic material does not show the same wear-free dynamic friction as the gecko.
最近有报道称，天然壁虎阵列在光滑基底上经过 30000 次循环后具有无磨损的动态摩擦力。基于这些发现，人们提出了刚性聚合物壁虎启发式合成粘合剂，以用于机器人脚部等高循环应用。在这里，我们研究了高密度聚乙烯（HDPE）和聚丙烯（PP）微纤维阵列在玻璃表面上反复循环接触时的行为，预载小于 40 kPa。我们发现，尽管纤维尖端显示出明显的塑性变形，但纤维阵列在 10000 次循环后仍保持原始剪切应力 300 kPa 的 54%。这种变形可能是由于纤维尖端的高粘附力引起的剪切诱导塑性蠕变、粘着磨损或热效应。我们假设，这些纤维阵列已经达到了基本的材料极限，未来的壁虎合成粘合剂设计必须考虑到为避免损坏而产生的高粘附力。尽管合成材料和天然壁虎阵列具有相似的弹性模量，但合成材料并没有表现出与壁虎相同的无磨损动态摩擦力。
