Self-propelled droplet behavior during condensation on superhydrophobic surfaces

Abstract

Self-propelled droplet motion has applications in various engineering fields such as self-cleaning surfaces, heat transfer enhancement, and anti-icing methods. A superhydrophobic surface was fabricated using two simultaneous chemical reactions with droplet condensation experiments performed on the horizontal superhydrophobic surface to characterize the droplet behavior. The droplet behavior is classified into three types based on their motion features and leftover marks as immobile droplet coalescence, self-propelled droplet jumping, and self-propelled droplet sweeping. This study focuses on the droplet sweeping that occurs due to the ultra-small rolling angle of the superhydrophobic surface, where the resulting droplet sweeps along the surface, merging with all the droplets it meets and leaving a long, narrow, clear track with a large droplet at the end of the track. An easy method is developed to predict the droplet sweeping direction based on the relative positions of the droplets just before coalescence. The droplet sweeping always absorbs dozens of droplets and is not limited by the surface structures; thus, this sweeping has many useful applications. In addition, the relationships between the droplet behavior and the number of participating droplets are also analyzed statistically.

Morphology evolution and dynamics of droplet coalescence on superhydrophobic surfaces

“…[33][34][35][36] In view of this situation, a system with high-speed cameras is designed as shown in Figure 2. However, it's difficult to capture the detailed coalescence process as droplet coalescence in a few milliseconds and the visibility under condensation is poor.…”

“…However, it's difficult to capture the detailed coalescence process as droplet coalescence in a few milliseconds and the visibility under condensation is poor. [33][34][35][36] In view of this situation, a system with high-speed cameras is designed as shown in Figure 2.…”

“…It can be seen that the data sets collapse into one line when plotted in dimensionless form, which demonstrates that the bridge front propagates with a square root in time scaling as confirmed in published works. 35. The motion of droplets with smaller sizes may be more sensitive to the propelling of the superhydrophobic copper wire.…”

Droplet re-icing characteristics on a superhydrophobic surface

“…9,10 Besides basic studies on icing, many anti-icing methods are proposed to suppress the ice accretion, one of which is the application of nanoengineered surfaces. 11,12 Researchers fabricated numerous surfaces with various structures and wettability with the purpose of delaying the ice nucleation, [13][14][15] retarding the ice propagation, 16,17 reducing the ice adhesion, 18,19 and even self-cleaning subcooled droplets or melting frost by a kind of self-jumping behavior, [20][21][22][23][24][25] and have achieved expected results.…”

Advances in Bio-inspired Tribology for Engineering Applications

“…7c exhibits sufficiently high contact angles with the skin that they were easily removed from the surface by tilting the surface less than two degrees. This anti-wetting property exhibited by the gecko's skin is already being considered for many tribological applications with regard to corrosion-resistant coating, which in a better sense is immune to moisture making the surface immune to corrosion [39][40][41][42][43]. To get a better perspective of what happens when a gecko skin is impacted upon by a water droplet, a time evolution picture [38] was taken as shown in Fig.…”