Bouncing dynamics of liquid drops impact on ridge structure: an effective approach to reduce the contact time

Abstract

Surfaces designed so that liquid metals do not stick to them but instead rebound as soon as possible have received considerable attention due to their significant importance in many practical technologies. We herein design a ridge structure that can induce the drop to rapidly rebound through the combination effect of centre-drawing recoil and the resulting faster retraction velocity. The suitable sharp-angle of the ridge for minimizing the contact time is determined as 20-30°. Further analysis reveals that multi-ridge structure or two-ridge structure with gaps can reduce more contact time. We also highlight the role the impact velocity played in minimizing the contact time, which has been a neglected parameter previously. Our studies would open up a new way to reduce the contact time and control the bouncing dynamics of metal drops, which provides guidance for some potential applications, such as preventing splashing molten drops from depositing on clean surface.

Nanodroplets impact on surfaces decorated with ridges

“…Because when the velocity first starts growing, the rapid rise of upward force will stop the droplet more quickly, but then it takes longer to counteract this growing impact velocity as the upward force becomes stagnant. Next, a reduction in contact time appears in State 2, and this does not contradict previous results claiming a nearly constant [31], because apart from the expansion and retraction process, we also add up the elapsed time of On the other hand, the variation law of the bouncing height is much simpler than the contact time, as shown in Figure 8(a). There is a trend that the dimensionless bouncing height increases with the impact velocity, but with two small exceptions.…”

“…According to the snapshots shown in Figure 5 According to our simulation results, the contact time between nanodroplets and ridge-decorated surfaces do not present a simple step-like variation as the impact velocity increases, as shown in Figure 7. This distinction with the published work [31] may attribute to the different definition of contact time, and this kind of definition at nano scale can significantly affect the conclusions [37]. At first glance, the variation of dimensionless contact time with the impact velocity seems a little bit complicated.…”

“…Koishi et al [29] and Gao et al [30] used MD to study the bouncing performance of nanodroplets on columnar array structures, with a focus to develop the theories and models on the spreading dynamics and energy transformation, without the consideration of the contact time. Li et al [31] investigated the effect of nanoridges on reducing liquid-solid contact time. It should be noted that they defined the droplets detaching point from the flat substrate rather than the nanoridge peak.…”

Molecular Investigation of Contact Line Movement in Electrowetted Nanodroplets

“…To further elucidate the effect of temperature, the mean-square displacement of the droplet atoms in the x-direction (MSD x ) is plotted, as depicted in Figure 9. This approach has also been utilized in prior studies to demonstrate the effect of temperature 57 or substrate features 58,59 on molecular displacement and diffusion. It is evident from Figure 9 that increase in temperature leads to greater displacement along the dominant direction of spreading, i.e., the x-direction.…”

Nanowall Textured Hydrophobic Surfaces and Liquid Droplet Impact

“…Due to the shear rate at the droplet–solid interface, the frictional force significantly changes the droplet behavior on the surfaces [ 14 ]. The contact time and spreading lengths of the droplet can be considerably reduced, and the rebounding height improved with the impact on specially designed multi-ridge structure (with 20–30 ridge angles) or micropillar surface created by an array of nanotubes due to the combined effect of center-drawing recoil, weaker wettability of drops, and their penetrating ability into the valleys between surface protrusions [ 15 , 16 ]. The contact time of impacting droplets on carbon soot nanocoating also becomes shorter due to the irregular hierarchical nanoparticle (or flower-like) networks formed on the surface [ 17 , 18 ].…”