Biochar based self cleaning superhydrophobic surface with aqueous DESphobic properties

Abstract

In this work, facile fabrication of chemically stable superhydrophobic surfaces based on biocompatible, fluorine free, carbon rich biochar has been reported. Biochar synthesized from dried rice straw by pyrolysis at 550˚C, which was characterized using Fourier Transform Infrared (FTIR) and Scanning Electron Microscopy (SEM). The biochar coated surface demonstrated superhydrophobic behaviour with static water CA > 150°. Aqueous drops remain in superhydrophobic state due to stability of Cassie-Baxter wetting regime and can shows very high-water contact angle (WCA > 160°) and self-cleaning behaviour. Such a very high WCA have been achieved typically by combination of low energy chemicals (fluorine based) and surface textures. However, no harsh chemical treatment of biochar was performed and a simple methodology of creating biochar layer onto the substate was adopted. Such surface also demonstrated repellent properties against aqueous mixtures of deep eutectic solvent (DES). A spherical aqueous DES drop can be easily formed onto the biochar surface for image analysis. The density of the liquid sample with a small sample volume can be assessed using this drop shape that was measured on the superhydrophobic biochar surface.