A Self-Folding Pneumatic Piston for Mechanically Robust Origami Robots

This letter presents a self-folding piston-style actuator for flat-foldable robots. Despite the variety of soft and planar actuators used in origami robots, extensional actuators are uncommon because they must resist buckling and bending loads, while soft and planar machines are inherently flexible. To address this, we developed a flat-foldable frame consisting of a piston and barrel that transforms into an operational state when driven by internal pressure. The barrel contains a pneumatic pouch and constrains the pouch to extend along a single axis for extensional actuation. We characterize the speed and blocked force of this actuator and compare it to a comparable unconstrained pouch in the actuation of a self-folding robotic arm. Our results indicate that the self-folding piston can operate much faster than the unconstrained pouch and resist off-axis loads.