Our work on the wear and high-cycle properties of gecko synthetic adhesives has been published in Langmuir.
We examined 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 found 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.