Jet Dynamics Associated with Drop Impact on Micropillared Substrate

Abstract

The jetting phenomenon associated with droplet impact upon a hydrophilic micropillared substrate was analyzed in detail using a high-speed camera. Viscosities of the fluids were varied using differing concentrations of glycerol in deionized water. This paper aims to connect similarities between this form of capillary jetting and another well-known jetting phenomenon from the bubble bursting. Both experience a cavity collapse when opposing fluid fronts collide which causes a singularity at the liquid surface, thus leading to the occurrence of jetting. Following processes used to define scaling laws for bubble bursting, a similar approach was taken to derive scaling laws for the dimensionless jet height, jet radius, base height, and radius of the jet base with respect to dimensionless time for the jetting phenomenon associated with the droplet impact. The development of a top droplet before the breakup of the jet also allows the examination of a scaling law for the necking diameter. We find that with the proper scaling factors, the evolution of the jet profile can collapse into a master profile for different fluids and impact velocities. The time dependence of the necking diameter before the jet breakup follows the power law with an exponent of ~2/3. Contrastingly, for other jet parameters such as the radius and height, the power law relationship with time dependence was not found to have a clear pattern that emerged from these studies.

Droplet-Impact Driven Formation of Ultralow Volume Liquid Marbles with Enhanced Mechanical Stability and Sensing Ability

“…in such a way that daughter droplets are produced from a microliter-sized droplet. Impacting the droplet at a higher Weber number, We > 46, could result in the jetting of the droplet on retraction and breakage of the liquid column to emit a single satellite droplet. ,,, Sprittles et al demonstrated the formation of large spherical liquid marbles along with uncoated satellite droplets at We = 46 . They observed the production of multiple satellite droplets at a higher We (>52), but not all resulted in the formation of completely covered marbles.…”

Jetting Dynamics of Viscous Droplets on Superhydrophobic Surfaces

“…These jetting events are often accompanied by the capillary end-pinching of the jet as it reaches the maximum height and the subsequent release of the secondary droplet(s). Siddique et al and Asai et al showed that for the impact of viscous droplets (viscosity higher than DI-water) on a micropatterned hydrophilic surface, the jet velocity ( U j ) and the top secondary droplet size ( d j ) religiously follows the scaling law of Gañán-Calvo, i.e., γ ρ d j η 2 ∼ ( η U j γ ) − 5 / 3 . Here, the variables ρ, γ, and η denote the experimental fluids’ density, surface tension, and dynamic viscosity, respectively.…”