Impacting Water Droplets Can Alleviate Dust from Slanted Hydrophobic Surfaces

Abstract

Water droplet impacting on a slanted dusty hydrophobic surface is examined in relation to dust mitigation from surfaces. Impacting droplet characteristics including droplet spreading/retraction rates, slipping length, and rebound heights are analyzed via high-speed recording and a tracker program. The environmental dust characteristics in terms of size, shape, elemental composition, and surface free energy are evaluated by adopting the analytical methods. The findings reveal that the dynamic characteristics of the impacting droplet on the slanted hydrophobic surface are significantly influenced by the dust particles. The maximum droplet spreading over the dusty surface becomes smaller than that of the nondusty surface. The presence of the dust particles on the slanted hydrophobic surface increases energy dissipation, and the water droplet slipping length over the surface becomes less than that corresponding to the nondusty surface. Impacting droplet fluid infuses over the dust particle surface, which enables mitigation of dust from the surface to the droplet fluid. A dust-mitigated area on the slanted surface is larger than that corresponding to the horizontal surface; in which case, the area ratio becomes almost six-fold, which slightly reduces with increasing Weber number. The optical transmittance of the dust-mitigated surface by the impacting droplet remains high.

Impacting Droplet Can Mitigate Dust from PDMS Micro-Post Array Surfaces

“…Since the hydrophobized surface possesses nanoporous webs, it can cause inflection of the droplet liquid during the initial period of impact. The volume of inflection of droplet liquid (d∀) into nanopore sites on the hydrophobized surface can be approximated by Hagen-Poiseuille's approach [22], i.e., d∀ ∼ = πD 4 H ∑ P 8µx…”

“…The impact of liquid droplets on hydrophobic surfaces has various applications, some of which include biomedicine [1], combustion [2], forming and coating [3], and self-cleaning [4]. Although various mechanisms are adopted for droplet mobility on surfaces such as polydimethylsiloxane (PDMS) surface [5], the surface texture [6] and droplet fluid properties [7] remain the important properties assessing the droplet behavior.…”

“…Although several methods have been proposed for dust mitigation from surfaces [14], the self-cleaning process offers advantages over the conventional methods in terms of operational costs. In general, self-cleaning of hydrophobic surfaces can be achieved either by utilizing rolling droplets [12] or impacting droplets [4]. Although dust mitigation from hydrophobic surfaces has been presented in an earlier study [4], the texture morphology consisting of micro/nanopillars gave rise to a large amount of dust residue remaining on the impacted surface.…”

“…In general, self-cleaning of hydrophobic surfaces can be achieved either by utilizing rolling droplets [12] or impacting droplets [4]. Although dust mitigation from hydrophobic surfaces has been presented in an earlier study [4], the texture morphology consisting of micro/nanopillars gave rise to a large amount of dust residue remaining on the impacted surface. This is due to the small size particles, which are anchored and remained in between the texture gaps.…”