Nonspecular Reflection of Droplets

The bouncing of droplets on super-repellent surfaces normally resembles specular reflection that obeys the law of reflection. Here, the nonspecular reflection of droplet impingement onto solid surfaces with a dimple for energy-efficient, omnidirectional droplet transport is reported. With the dimple of the radius being comparable to that of the droplet, all the symmetries in the law of reflection can be broken down so that the droplet is endowed with a translational velocity finely tunable in both its direction and magnitude simply by varying the radii of the droplet and the dimple, the impinging position, and droplet Weber number. Tailoring the initial and translational velocity of impinging droplets would steer their reflected trajectories at will, thus enabling versatile droplet manipulation including trapping, shedding, antigravity transport, targeted positioning, and on-demand coalescence of droplets.

Automated summary

Adding a dimple on super-repellent surfaces can break the symmetries in the law of reflection, allowing for fine tuning of droplet translational velocity in both direction and magnitude. This enables versatile droplet manipulation including trapping, shedding, antigravity transport, targeted positioning, and on-demand coalescence of droplets.