Self-supporting superhydrophobic thin polymer sheets that mimic the nature's petal effect

Abstract

The high adhesive force between the red rose petal and the water droplet on its surface is termed as the ‘petal effect’, which is caused by the hierarchical array of micro papilla on the surfaces together with the nano-folds existing on top of each papilla. Because of that special surface topography, the surface is superhydrophobic, but at the same time highly adherent to the water droplet such that the droplet cannot move even if the surface is turned upside down. In this work, we produced a thin (thickness below 1μm) self-supporting polymer sheet that mimics the surface of a red rose petal. The product is a two-layer polymer sheet made from poly(glycidyl methacrylate) (PGMA) as the supporting layer and a hydrophobic poly(1H,1H,2H,2H-perfluorodecyl acrylate) (PPFDA) on top of it as the functional layer, both of which were deposited by initiated chemical vapor deposition (iCVD) process. The integration of conformal and solvent-free iCVD process into the classical two-step molding procedure allowed exact transfer of surface topography of the petal surface, which was verified by SEM analysis. The static contact angle of water droplet on the surface of the polymer replica was found to be 152±3°, and the water droplet did not roll-off even the polymer sheet is tilted or turned upside down.