Origami-Inspired Soft Twisting Actuator

Overview

Rotation along the actuator axis is one of the primary degrees of freedom in robots, yet very few soft twisting actuators can reach a full turn. This work integrates the Kresling origami pattern into a silicone shell to create origami-inspired soft pneumatic actuators (OSPAs): under vacuum or inflation, each module folds or unfolds, and the free end rotates and translates simultaneously. Combining clockwise and counterclockwise modules in series produces distinct output motions — pure rotation with stroke, or pure linear motion.

An analytical model shows that a module's maximum rotation angle depends only on its crease ratio b/a, guiding parametric optimization. The silicone shells are fabricated by spin and slush casting with intentionally thickened creases, making them far more robust than paper-made counterparts.

Key results

• Maximum rotation of 435°, with a rotation ratio (rotation angle / aspect ratio) of about 136° — roughly twice the largest value previously reported for soft torsional actuators.
• Survived 160% stretching, a 2 kg load, and hammer impacts that collapsed paper-made counterparts; no performance decay after 1000 actuation cycles.
• Maximum torque of 24 N·mm with torsional rigidity up to 212.7 N·mm²/°.
• Demonstrated in three robots: a rotatable soft gripper that grips and lifts simultaneously, a versatile deployable robot arm that tracked a swimming robotic fish with a rotating camera and performed suction pick-and-place, and a soft snake robot that steers through pipe forks by twisting its head. The gripper built on these actuators has its own project page.