Odd droplets Fluids with odd viscosity and highly deformable interfaces

Flows with deformable interfaces are commonly controlled by applying external fields or by modifying the boundaries that interact with the fluid; however, realizing such strategies can be demanding or impractical in many settings. Here, we demonstrate that fluids with broken symmetries can self-control their mechanics. We present a continuum model of a viscous fluid with highly deformable interfaces subject to capillary stresses. Our model features odd viscosity, a parity-violating transport coefficient that emerges in chiral fluids. Using direct numerical simulations of two-dimensional two-phase flows, we focus on the impact of an odd droplet on a superhydrophobic surface. We demonstrate that odd viscosity dramatically disrupts conventional symmetric spreading by inducing asymmetric deformations and chiral flow patterns. Our analysis reveals a variety of unconventional dynamic regimes, including leftward and rightward bouncing as well as rolling, depending on the relative strength of the odd viscosity. Overall, this work presents a framework of broad interest to the control of highly deformable liquids and materials with broken symmetries, as well as to droplet dynamics, where it showcases the potential of odd viscosity as a route for controlling interfacial flows and designing functional metamaterials with tailored fluidic properties.