Due to variety in soft actuator technology, choosing the suitable actuator for a specific application is nontrivial. To the best of our knowledge, there are no recent studies that compared the capabilities of existing soft actuators in powering exoskeletons. Therefore we compared five soft actuator candidates that can be deployed in exoskeleton applications. The inclusion criteria were softness, acoustically noiseless operation, and demonstrated ability to lift a tensile load equal or greater than the weight of the forearm and hand of a hypothetical 95th percentile, 2-year old boy (3.38 N). Accordingly, two thermally driven actuators, coiled nylon fiber (CNF), and ethanol-based phase-change (EPC); and three electroactive polymer actuators, plasticized poly vinyl chloride (PVC) gel; a stacked dielectric elastomer (DE) actuator; and a hydraulically amplified self-healing electrostatic (HASEL) actuator, were chosen for comparison. These actuators were compared in their stress, unidirectional strain, strain-rate, power-to-mass ratio, and efficiency. The stacked DE actuator with reported force of 32 N, unidirectional strain of 18%, strain-rate of 500%/s, and efficiency of ~28%, showed the closest resemblance to mammalian skeletal muscle. Thus a commercially available stacked DE actuator was chosen as the most applicable soft actuator technology for pediatric rehabilitation robots.
Soft Robotics in Rehabilitation 2021, Pages 241-258,