Department of Mechanical Engineering, Carnegie Mellon University, , Pittsburgh, PA 15213, USA.
J R Soc Interface. 2014 Feb 19;11(94):20131205. doi: 10.1098/rsif.2013.1205. Print 2014 May 6.
The exceptionally adhesive foot of the gecko remains clean in dirty environments by shedding contaminants with each step. Synthetic gecko-inspired adhesives have achieved similar attachment strengths to the gecko on smooth surfaces, but the process of contact self-cleaning has yet to be effectively demonstrated. Here, we present the first gecko-inspired adhesive that has matched both the attachment strength and the contact self-cleaning performance of the gecko's foot on a smooth surface. Contact self-cleaning experiments were performed with three different sizes of mushroom-shaped elastomer microfibres and five different sizes of spherical silica contaminants. Using a load-drag-unload dry contact cleaning process similar to the loads acting on the gecko foot during locomotion, our fully contaminated synthetic gecko adhesives could recover lost adhesion at a rate comparable to that of the gecko. We observed that the relative size of contaminants to the characteristic size of the microfibres in the synthetic adhesive strongly determined how and to what degree the adhesive recovered from contamination. Our approximate model and experimental results show that the dominant mechanism of contact self-cleaning is particle rolling during the drag process. Embedding of particles between adjacent fibres was observed for particles with diameter smaller than the fibre tips, and further studied as a temporary cleaning mechanism. By incorporating contact self-cleaning capabilities, real-world applications of synthetic gecko adhesives, such as reusable tapes, clothing closures and medical adhesives, would become feasible.
壁虎异常黏附的脚部通过每一步都能脱落污染物来保持在肮脏环境中的清洁。受壁虎启发的合成黏附剂在光滑表面上已实现了与壁虎相当的附着强度，但接触自清洁的过程尚未得到有效证明。在这里，我们展示了第一个在光滑表面上既匹配了壁虎脚部的附着强度，又匹配了接触自清洁性能的受壁虎启发的黏附剂。使用类似于壁虎在运动过程中脚部所受的负载的负载-拖动-卸载干接触清洁过程，我们的完全污染的合成壁虎黏附剂能够以与壁虎相当的速度恢复失去的附着力。我们观察到，污染物的相对大小与合成黏附剂中微纤维的特征大小强烈决定了黏附剂从污染中恢复的方式和程度。我们的近似模型和实验结果表明，接触自清洁的主要机制是在拖动过程中颗粒的滚动。对于直径小于纤维尖端的颗粒，观察到颗粒嵌入相邻纤维之间，并且进一步作为一种临时清洁机制进行了研究。通过整合接触自清洁能力，合成壁虎黏附剂的实际应用，如可重复使用的胶带、衣物搭扣和医用黏附剂，将变得可行。
