As a dense suspension of piezoelectric nanoparticles shear thickens due to a transition from frictionless (gray) to frictional (red) particle–particle interactions, friction-induced piezoelectricity ...

If you mix cornstarch and water in the right proportions, you get “oobleck”: something that seems not-quite-liquid but also not-quite-solid. Oobleck flows and settles like a liquid when untouched, but ...