posted on 2020-06-11, 22:29authored byXiaoxiao Dong, Rui Zhang, Yu Tian, Melvin A. Ramos, Travis Shihao Hu, Zhihang Wang, Hong Zhao, Lipeng Zhang, Yiyang Wan, Zhenhai Xia, Quan Xu
Geckos
have the extraordinary ability to adhere and move across
varied surfaces, while keeping their tiny high-aspect-ratio foot-hairs
intact for thousands of attachment–detachment cycles. Inspired
by the dry adhesive structure of gecko sole, various gecko-inspired
artificial mimics have been developed, but many of them suffer from
premature failures and short fatigue life. Herein, we discover that
individual gecko seta is a functionally graded material. Its Young’s
modulus gradually decreases from base to tip, with up to 20 times
of difference in magnitude. Finite element analysis indicates that
this gradient design is the key to make the natural setal stalks more
flexible (critical for producing large frictional adhesion on rough
surfaces) and less stressed (critical for achieving high fatigue resistance)
during each attachment. Inspired by these findings, we have fabricated
poly(dimethylsiloxane) (PDMS)-based artificial gecko foot-hairs with
a gradient distribution of magnetic nanoparticles as the reinforcements,
achieving similar varying modulus/stiffness. The biomimetic hairs/pillars
show enhanced fatigue resistance compared to the uniform counterparts.
This work opens a door in designing dry adhesives with both high adhesive
strength and long fatigue life.