Self Cleaning Of Surfaces And Water Droplet Mobility PDF Download

Dust particles can adhere to surfaces, and thereby, can decrease the efficiency of diverse processes, such as light absorption by solar panels. To efficiently (in terms of energy and time) clean surfaces, it has been proposed to employ the bio-inspired "self-cleaning" mechanism, in which water droplets slide/roll along the surface, and thereby detach (clean) particles from the surfaces. It was shown that superhydrophobicity is beneficial for the self-cleaning mechanism: superhydrophobicity reduces the friction between water droplets and the surfaces, thus, allowing water droplets to slide on the surface. However, the forces that attach and detach particles from surfaces during the self-cleaning mechanism, and on the effect of nanotextures on these forces, are not fully understood. To shed light on these forces, and the effect of nanotexture on them, I prepared four Si-based samples (relevant to solar panels): (1) smooth or (2) nanotextured hydrophilic surfaces, and (3) smooth or (4) nano texturedhydrophobic surfaces. In agreement with previous publications, it is shown that the efficiency of particle removal increases with hydrophobicity. Furthermore, nanotexture enhances the hydrophobicity, and increases particle removal. Specifically, hydrophilic particle removal increased from ~41%, from hydrophilic smooth Si wafer, to ~98% from superhydrophobic Si-based nanotextured surfaces. However, my results and analysis show that the reason for the increased particle removal is not small friction between the droplets and the superhydrophobic surfaces; it is the reduction of the adhesion force between the particle and the surface, and the altered geometry of the water-particle-air line tension acting on the particles on superhydrophobic surfaces, which increases the force that can detach particles from the surfaces. The experimental methods and the derived criterion for particle removal can be implemented to engineer self-cleaning surfaces using other surfaces and dust particles, exhibiting different chemistries and/or textures.