Dynamic behavior of droplets under interfacial jamming of nanoparticles

Interfacial particle jamming can lock a droplet in a non-spherical shape; however, the effects of jamming on the dynamic behaviors of droplets are not well known. In this paper, droplet impact dynamics are studied on a mechanically weak superhydrophobic surface whose outer nanoparticles were detached by an impinging droplet and jammed at the droplet surface during retraction. The number and coverage of jammed particles were increased by increasing the impinging velocity, and unusual parachute-like shapes appeared at the rebounding moments for polyethylene oxide (PEO) droplets. Also, oscillation prohibition, bounce damping, and final deformation of the PEO droplets were each enhanced with increased velocity. The critical impinging velocity for the final deformation was much smaller than that required to generate complete droplet coverage, indicating that considerable local jamming was sufficient for generating droplet deformation. Local jamming was difficult to achieve during impact when droplet viscosity was low, as in the case of pure water, because particles were well dispersed under high surface flowability. Published by AIP Publishing.