Development of multi-degree-of-freedom hand prosthesis cover with sensory recognition

Abstract

Hand prostheses by upper limb amputees are primarily dependent on visual feedback owing to the loss of sensory function in their hand. Although previous researches have been conducted on the restoration of the sensory function of amputees and on the development of electronic skin and gloves for sensory feedback, the realization to apply the research results to commercial hand prostheses is still difficult. In this study, we designed and developed a hand prosthesis cover including a sensory recognitive function which closely mimics human hand skin and, resulting into a multi-degree-of-freedom (DOF) myoelectric hand prosthesis. The proposed cover was made of flexible silicon to mimic the human hand skin, which can measure a grip force of less than 50 N using a tactile sensing module. The tactile sensing module was developed using a force-sensitive resistor sensor, and solid silicone vacuum compression molding by embedding the sensor and wires inside the cover was introduced for the fabrication process. A developed finger module for multi-DOF myoelectric hand prostheses by imitating the anatomical structure and motion mechanism of a human finger was compared the performance of the developed cover with that of a commercial cover on the developed finger module of the myoelectric hand prosthesis. The metacarpophalangeal joint range of motion of the finger module with the proposed cover with a 1.5 mm thickness was measured from 0° to 60° and the flexion angular velocity was recorded as a value of 60°/710 ms, which are similar to those of the commercial cover. From the experiments, we found that the hand gestures and grip motions seem to be similar with the proposed and commercial covers. From the experiment, we can suggest that the developed cover with sensory recognition can be directly applied to multi-DOF myoelectric hand prostheses. Also, with a fast and simple commercialized process, widely usage for amputees with the developed hand prosthesis cover will be available.