Laser structured biomimetic artificial surfaces that quantitatively reproduce the water repellency of a Lotus leaf

Control over the wettability of solids and manufacturing of surfaces with special hydrophobic and self- cleaning properties have aroused great interest because of their significance for a vast range of applications in daily life, industry and agriculture. Hierarchical structures with a cone-like shape and features in both the micro- and the nano-scales are produced. By varying the laser pulse fluence on the surface, it is possible to achieve control of the wetting properties through a systematic and reproducible variation of roughness at micro- and nano-scale. In this paper, the Lotus-effect or the remarkable self-cleaning ability of the lotus leaf is reproduced on a laser structured silicon surface. Single crystal n-type Si wafers were irradiated by a laser source and its water repellent properties were investigated by measuring the restitution coefficient of water droplets bouncing off the surfaces as a function the droplet velocity for surfaces with varying degree of surface roughness.