Designing a Bioinspired Hydrophobic Surface with honeycomb-like microtextures*

We report the non-wetting characteristics of a hydrophobic leaf Colocasia and design a bioinspired microtexture surface based on the morphology of the leaf. SEM of the leaf surface shows a two-tier honeycomb-like microtextures. The static, advancing and receding contact angle of water droplet on the surface of the leaf were measured as 149, 153 and 144 degrees, respectively. One-tier SU-8 hexagonal cavities on a silicon wafer were manufactured in our lab using photolithography techniques. The measured static contact angle on the engineered surface was found to be function of the ratio of the radius of inner and outer circle, circumscribing the hexagonal cavity. The angle increases with the ratio and a maximum angle of 149 degrees was measured. The variation in the angle in Cassie state was consistent with an existing model (Patankar, Langmuir, 2005). We report evaporation characteristic of a sessile droplet and impact dynamics with different impact velocities on this surface. The evaporation characteristics were compared with a diffusion-limited evaporation model for a sessile droplet (Bhardwaj, Colloidal and Interface Science Communications, Vol. 24, 2018).