Gorb S, Jiao Y, Scherge M
Biochemistry Department, Max-Planck-Institute of Developmental Biology, Tübingen, Germany.
J Comp Physiol A. 2000 Sep;186(9):821-31. doi: 10.1007/s003590000135.
Natural releasable attachment systems of insect legs, where attachment-detachment performances are often very fast, seem to be optimized to get a maximum of real contact to the substratum. Tarsi of Tettigonia viridissima bear flexible attachment pads with unusual ultrastructural architecture of the cuticle. The indentation of the attachment pads was measured under different loads using a force-tester. Since the mechanical properties are influenced by material structure, the freeze-substitution experiments were undertaken to investigate the influence of loads on material structure. Both profile changes of the surface and the orientation of cuticle microfibrils were visualized by means of scanning electron microscopy followed by fracturing of the frozen material. The results show that the flexible pad material deforms replicating the substrate profile down to the micrometer roughness. The pad material showed both elastic and viscous behavior under loads. Elastic deformation of the pad occurred under normal force applied for 4-6 s (elastic modulus 27.2 +/- 11.6 kPa). Two viscous relaxation processes were found, of time constants tau1 = 1.88+/-0.616 s and tau2 =41.2 +/- 9.95 s. Low stiffness of material studied here aids in surface replication and increase of area of real contact between the pad and the underlying substrate.
昆虫腿部的天然可释放附着系统，其附着-分离性能通常非常迅速，似乎经过了优化，以实现与基质的最大实际接触。绿螽斯的跗节带有具有异常超微结构的角质层的柔性附着垫。使用力测试仪在不同负载下测量附着垫的压痕。由于机械性能受材料结构影响，因此进行了冷冻置换实验以研究负载对材料结构的影响。通过扫描电子显微镜观察冷冻材料断裂后的表面轮廓变化和角质层微纤维的取向。结果表明，柔性垫材料会变形，复制出直至微米粗糙度的基底轮廓。垫材料在负载下表现出弹性和粘性行为。在施加4-6秒的法向力时，垫发生弹性变形（弹性模量为27.2 +/- 11.6 kPa）。发现了两个粘性松弛过程，时间常数分别为tau1 = 1.88 +/- 0.616秒和tau2 = 41.2 +/- 9.95秒。此处研究的材料的低刚度有助于表面复制并增加垫与下层基质之间的实际接触面积。
