Micro-adhesive structure inspired by tree frog toe pads fabricated by femtosecond laser processing of PVA sponge.

This article focuses on the development of a bioinspired micro-adhesive structure fabricated on a polyvinyl alcohol (PVA) sponge, modeled after the hexagonal microstructure of the toe pads of the tree frog species Zhangixalus arboreus. Using femtosecond laser processing, hexagonal channels of varying sizes were created on the sponge surface, which releases liquid upon contact to maintain an optimal liquid phase thickness for adhesion in wet conditions. Experimental measurements showed that the microstructured sponge exhibited increased shear (frictional) forces when pressed and slid against flat and uneven surfaces, with maximum shear forces dependent on the microstructure size and surface roughness; excessive fineness reduced adhesion due to agglomeration of microstructures. The study highlights the role of microcapillary bridges formed by the liquid phase in enhancing friction and suggests potential applications in soft robotic grippers designed to handle delicate objects without damage.