Key parameters of biomimetic patterned surface for wet adhesion

Inspired by the polygonal arrays on the toe pads of tree frogs and newts, micro hexagonal pillars were fabricated on a cast polyurethane elastomer (CPUE) surface so that a network of interconnected channels was formed. To investigate the effect of channel sizes, adhesion experiments were carried out with a flat polymethyl methacrylate (PMMA) probe and the patterned surface of CPUE samples under wet conditions. It was found that single factors alone, such as channel width (W), length (L), and height (H) have a slight effect on wet adhesion force. Comparatively, the values of width-to-length (W/L), height-to-length (H/L), and height-to-width (H/W) determine the wet adhesion force significantly. Actually, the wet adhesion force is reduced with increasing W/L values. Furthermore, optimal ranges of H/L and H/W values clearly enhance the wet adhesion force, even considering the reduction with the increasing W/L values.