Shape memory alloys actuated upper limb devices: A review

Recently, significant efforts have been made to develop prostheses, soft rehabilitation, and assistive devices that enhance the quality of life of limb amputees and the activities of daily living (ADL) of stroke patients. Therefore, this present study provides a general overview of the current prosthetic, assistive, and rehabilitative devices with a focus on actuators that provide actuation via shape-memory alloys (SMA). Shape-memory alloy (SMA)-based actuators are the subject of considerable research as they possess high force-to-weight ratio, quiet operation, muscular mobility, bio-compatibility, and accessible design options, all of which can potentially be used to develop inventive actuating systems. Several studies have examined the use of SMA-actuated devices in the medical and engineering industry. They have also, more recently, been used to develop soft robotic systems. This present review primarily focuses on the characterization, number, type of actuator, degrees of freedom (DOF), weight, cooling technique, control strategies, and applications as well as the advantages and disadvantages of plate, spring, and wire-based SMA actuators. Composite-based upper limb SMA actuators were also reviewed and compared in terms of the matrix, reinforcing materials, SMA configuration actuator dimensions, and manufacturing method as well as their advantages and disadvantages. The findings indicate that, in the last few years, more studies have examined developing novel intelligent materials with which to improve hand flexibility. Therefore, SMA materials have a promising future in the development of intelligent designs for hand-robots. They may also be used to improve control robustness as well as the accuracy of hand functions for ADL and effective rehabilitation.