Animating Soft Matter with the Elastic Leidenfrost Effect

Liquid droplets near hot surfaces don't boil, but instead float on a cushion of vapor created beneath them. This is the Leidenfrost Effect, and while it is well-studied for liquids and even hard solids such as dry ice, nothing is known about the behavior of soft solids under such conditions. I will show how this leads to a new phenomenon: the Elastic Leidenfrost Effect. By dropping hydrogel spheres onto a hot substrate, we observe not hovering, but instead sustained bouncing dynamics accompanied by violent screeching. With a variety of experimental techniques, I will show that the underlying physics of both the bouncing and the screeching relies on the coupling between vaporization and elastic deformation. Beyond the Leidenfrost Effect, this phenomenon unearths the broader concept of coupling activiation to deformation in soft materials and promises to impact fields ranging from granular physics and active matter to microfluidics and metamaterials.