A feasibility study of flexinol as the primary actuator in a prosthetic hand

The majority of electrically powered prosthetic hands are based on a simple design that limits motion to one degree of freedom. Designs of multiarticulated prosthetic hands have had limited success due to their complexity and number of mechanical components. Thin wires of a material called flexinol^TM contract ∼5% in length when heated and return to their original length upon cooling. This suggests that flexinol^TM may serve as a microactuator in powered prosthetic hands, while reducing the number of mechanical components. This research aimed to quantify the performance characteristics (grip width, pinch force and flexion-extension cycle time) of flexinol^TM-based prosthetic fingers. Model fingers were built and their performance was compared to that of a conventional motor-driven VASI hand (grip width=53mm; maximum pinch force=15.5N; cycle time=3 s). The flexinol^TM model finger performance was comparable to that of the VASI hand (grip width=66mm; maximum pinch force=27N; cycle time=4.5 s).