Splash and anti-splash: observation and design.

We experiment with releasing ethanol droplets, from a specific height, onto both flexible and rigid surfaces. The study of the resulting impact and splashing provides new insights into the mechanisms of the short time-scale dynamics. Tuning and even suppressing a splash can be achieved by the use of elastic membranes with controlled tension. Under certain experimental conditions, i.e., droplet size and velocity of impact, for which a splash occurs after the impact of a droplet on a Petri dish Fig. 1 a , striking changes in the response occur when elastic membranes are used: as the film tension is decreased, the ability of the membrane to deflect during the impact increases until the complete suppression of the splash Fig. 1 b . We also use soft-lithography techniques to manufacture topographically microdecorated surfaces which consist of micropillars arranged on a square lattice with various lattice parameters. The use of these substrates allows us to alter the impact dynamics and, in particular, to achieve the tuning of a splash until the complete inhibition of the ejection of matter during the impact Fig. 2 . Rapidly moving the target surface is another way to control a splash. When the drop impacts a stationary surface, it splashes uniformly Fig. 3 a . However, when the target surface moves here a rotating disk is used , the splash is enhanced in the direction opposed to the motion and attenuated in the direction of motion Fig. 3 b . When a droplet impacts an inclined surface, asymmetric splashing is also observed Fig. 4 . In this example, a drop impacts a solid, smooth, and dry surface slightly above the splashing threshold. Above a critical inclination, splashing becomes suppressed only on the upward side Fig. 4 b . From the experiments presented above, we expect to better understand the fundamental physics of splashing. FIG. 1.