Balloon filled with ground coffee makes ideal robotic gripper

Particulate materials have a so-called jamming transition, which turns their behavior from fluid-like to solid-like when the particles can no longer slide past each other.

This phenomenon is familiar to coffee drinkers familiar with vacuum-packed coffee, which is hard as a brick until the package is unsealed.

Pretty neat (other than the part where they talk about a vacuum sucking the air out — it’s the external pressure that forces the air movement.)