Gravitational instabilities in binary granular materials

Significance Flow of granular materials, such as sand and catalytic particles, is critical to a wide range of natural phenomena and industrial processes. However, the physics underlying granular flows is poorly understood. We report the discovery of gravitational instabilities in binary granular materials driven by a gas channeling mechanism unseen in fluids. A Rayleigh–Taylor instability analog is observed despite a lack of surface tension between grains, while a droplet branching phenomenon demonstrates a deviation from fluid motion due to solidification of particles. These discoveries shed light on granular dynamics and can potentially explain geological formations and enable process technologies.