Temperature-induced tunable adhesion of gecko setae/spatulae and their biomimics

Gecko lizards have a remarkable climbing capability that enables them to adapt to a variety of environments. Although the hierarchical structures and adhesion mechanism of gecko feet have been studied extensively, there lacks a fundamental understanding of adhesion at relatively low temperature, in particular below icing point. Here, we study the adhesion forces of nanoscale gecko spatulae and setae on multiple surfaces in a broad range of temperature from 40 to -10 degrees C. Results demonstrate that the adhesion force of a single gecko spatula on a mica substrate at -10 degrees C increased by similar to 100% compared with that at room temperature. The adhesion and friction forces of a single seta also display similar trends. It is found that hydrogen bonds play a key role in the temperature-induced tunable adhesion. Emulating gecko feet, we have fabricated fibrillary adhesive surfaces and tested them under different environments. Like their biological counterparts, regulating temperature can tune their adhesion and self-cleaning capacity. This study shed lights on the adhesion mechanism of gecko at low temperature, and provides a base for the design of new generations of smart tires, climbing robots and/or biomedical devices that would perform robustly under extreme environments. (C) 2018 Elsevier Ltd. All rights reserved.