Feasibility of a warp-knitted shape memory alloy rehabilitation glove

Abstract

Shape memory alloys (SMAs) have an innate property that allows them to return to a memorized form when stimulated. They have been recently designed as flexible fabrics for use in wearable assistive devices. This study aimed to develop a rehabilitation assistive glove with good wearability for a hemiplegic patient using a knitted SMA with a high-unidirectional contractile response. We fabricated warp-knitted SMA actuators, which had higher contractile responses than those of weft-knitted SMA. The use of a knitting loom allowed these actuators to fit all the fingers of a patient. We developed a full-fabric glove, placed the SMA wires on the finger regions to form a tendon-driven structure, and attached knitted SMA actuators to the dorsal and palmar sides of the hand to assist flexion and extension. The joint range of motion after glove actuation increased by 11.620% and 141.710% in flexion and extension, respectively. The range of motion improved more with glove rehabilitation than with thermal stimulation or no actuation. The grip force also increased by 52.400% after rehabilitation exercises. The safety of the heat generated during actuation was confirmed, and its applicability as a thermal stimulus was validated (based on increased skin temperature). These outcomes suggest the practical potential of warp-knitted SMAs in fully fabricated wearable assistive devices.