Wet self-cleaning of biologically inspired elastomer mushroom shaped microfibrillar adhesives

We report that hydrophilic polyurethane mushroom shaped microfiber arrays possess wet self-cleaning ability using the lotus effect as biologically inspired synthetic fibrillar adhesives. In comparison with a flat surface made of the same polyurethane, the fiber array exhibited almost 100% wet self-cleaning without any degradation of adhesive strength. We attribute this cleaning ability to the mushroom shaped tip ending geometry of the fiber array, which causes the fiber array to be apparently hydrophobic even though the fiber material is hydrophilic. These results suggest that tip ending shape is one of the significant design parameters for developing contamination-resistant polymer fibrillar adhesives.