Droplet orthogonal impact on nonuniform wettability surfaces

Abstract

The vast majority of prior studies on droplet impact have focused on collisions of liquid droplets with spatially homogeneous (i.e., uniform-wettability) surfaces. But in recent years, there has been growing interest on droplet impact on nonuniform wettability surfaces, which are more relevant in practice. This paper presents first 2 (i.e., the outer domain is more wettable than the inner one). The experimental observations are consistent with the scaling and predictions of the analytical model, thus outlining a strategy for predicting droplet impact behavior for more complex wettability patterns.

Understanding and Utilizing Droplet Impact on Superhydrophobic Surfaces: Phenomena, Mechanisms, Regulations, Applications, and Beyond

“…If wettability patterns or surface structures exhibit the simple 2D axis symmetry (such as the circular hydrophilic block, [62] sphere, [99,100] cylinder, [101] circular grooves, [102] etc. ), droplets impacting on the center of the modified region spread and retract isotropically.…”

“…Starting from a conventional SHS, the shapes and positions of patterns are first settled and then hydrophilic/superhydrophilic decorations are selectively applied to the designed patterns. Various methods have been developed to modify the local wettability of the surface, such as local printing, [ 61 ] local etching, [ 62 ] and local ultraviolet illumination, [ 60 ] which contributes to the feasible fabrication of wettability‐patterned SHSs. As shown in the upper row of Figure 1b, typical unit patterns include the point, [ 62 ] straight stripe, [ 63 ] arc stripe, [ 60 ] geometric block, [ 61 ] and filled area, [ 64 ] etc.…”

“…Various methods have been developed to modify the local wettability of the surface, such as local printing, [ 61 ] local etching, [ 62 ] and local ultraviolet illumination, [ 60 ] which contributes to the feasible fabrication of wettability‐patterned SHSs. As shown in the upper row of Figure 1b, typical unit patterns include the point, [ 62 ] straight stripe, [ 63 ] arc stripe, [ 60 ] geometric block, [ 61 ] and filled area, [ 64 ] etc. Diverse unit patterns serve as basic elements to customize various patterns through combination.…”

Sprayable Superoleophobic Coatings for Pumpless Handling of Low‐Surface‐Tension Liquids

“…to impart uniform roughness before coating it with a low‐surface‐energy material. There are numerous prior works [ 33–37 ] that fabricated surfaces focused on high‐surface‐tension liquids, especially water (γ = 72 mN m −1 ). However, when the fluid surface tension drops below 30 mN m −1 , repellency becomes extremely difficult.…”