Drop Impact upon Micro- and Nanostructured Superhydrophobic Surfaces

Abstract

We experimentally investigate drop impact dynamics onto different superhydrophobic surfaces, consisting of regular polymeric micropatterns and rough carbon nanofibers, with similar static contact angles. The main control parameters are the Weber number We and the roughness of the surface. At small We, i.e., small impact velocity, the impact evolutions are similar for both types of substrates, exhibiting Fakir state, complete bouncing, partial rebouncing, trapping of an air bubble, jetting, and sticky vibrating water balls. At large We, splashing impacts emerge forming several satellite droplets, which are more pronounced for the multiscale rough carbon nanofiber jungles. The results imply that the multiscale surface roughness at nanoscale plays a minor role in the impact events for small We less than or approximately equal 120 but an important one for large We greater than or approximately equal 120. Finally, we find the effect of ambient air pressure to be negligible in the explored parameter regime We less than or approximately equal 150.

Fabrication of a Superhydrophobic Water-Repellent Mesh for Underwater Sensors

“…The chemical properties and structure of the hydrophobic surface affected the solidliquid interaction [20]. Fig.…”

Quantitative Testing of Robustness on Superomniphobic Surfaces by Drop Impact

“…When released on a super-omniphobic surface, a drop of any tested liquid deforms and spreads like a pancake, then retracts and bounces off the surface, as previously observed in details [18][19][20][21][22]. To determine P c , we increase the height of fall h (or impact velocity U ) until the tiniest visible amount of liquid remains at the impact location during the bouncing phase: this is observed in a typical sequence like in Figure 4.…”

“…Drop impact experiment is a particularly versatile way to test this robustness [18][19][20][21][22]. During impact, the sudden vertical deceleration of the liquid particles leads to momentum transfer that applies an effective dynamical pressure P dyn = 1/2ρU 2 , with U being the impact velocity and ρ the liquid density.…”

A study on the dynamic behaviors of water droplets impacting nanostructured surfaces

“…It was also noted that fragmentation occurred at lower overall We numbers on our nanostructured surfaces than has been reported with other systems. 5,20 According to known references 5 and 7, the existence of an air fraction in the surface results in minimization of the viscous dissipation in the water lamella film and makes the liquid smoothly spread over the surface when there is relatively low impact velocity.…”