Sticky bio-inspired micropillars: Finding the best shape

Very recently, both experimental and theoretical investigations have shown that microstructured surfaces covered with mushroom-shaped micropillars present strongly enhanced adhesive properties if compared to flat surfaces made of the same material. However, different geometries lead to different adhesive performance, and finding the optimal solution has become of utmost importance. This paper presents on which physical basis the optimal mushroom pillar shape should be sought, and it provides a relatively simple methodology to achieve the result. Calculations demonstrate that the adhesive performance of the pillar strongly depends on the geometry of the terminal plate. The best performance is achieved when the ratio s/Ri between the plate thickness (s) and the pillar internal radius (Ri) is close to 0.20.3, and the ratio Re/Ri is larger than 2, where Re is the external radius of the plate.