Dropping Oobleck

Oobleck is a peculiar substance. Formed from a suspension of cornstarch particles in water, it can flow like a liquid at low shear rates or jam into a solid under impact. Here, researchers explore what happens to a droplet of oobleck impacting a surface. As they expected, the team found that dilute drops could spread like a normal liquid during impact (top), and denser suspensions could impact like a solid would (below). But at the right conditions, they found that cornstarch-rich droplets could show liquid-like behavior at high shear rates and transition to solid-like behavior once the shear rate slowed down. (Image and research credit: A. Mobaseri et al.; via APS)