Abstract: An apparatus includes an actuator body having an elongated shape with two end-caps on opposite ends, the actuator body defining a cavity within the actuator body, a first material extending between the two end-caps forming a first portion of a wall of the cavity; and a second material extending between the two end-caps, forming a second portion of the wall of the cavity, wherein the two materials have different mechanical responses to longitudinal and radial loading.

Abstract: A robotic orthosis device for assisting users to rotate their wrist with a pair of fabric-based helical actuators and a sleeve or rigid interfaces configured to attach to a user's forearm. Each of the helical actuators includes a cylinder and a pneumatic bladder configured to inflate the cylinder. Each cylinder includes an anisotropic sheet material and a base sheet material running the length of the cylinder. The anisotropic sheet material comprises elastomeric strands that enable the material to stretch in a direction parallel to the orientation of the elastomeric strands, but different than the longitudinal axis of the cylinder. The base sheet material, which is affixed to the anisotropic sheet material, is strain-limiting along the longitudinal axis. When the bladder is pressurized, the expansion of the bladder causes the cylinder to stretch and twist, thus generating a helical force on the user' wrist relative to the elbow.