Partial or total upper extremity impairment affects the quality of life of a vast number of people due to stroke,
neuromuscular disease, or trauma. Many researchers have presented hand orthosis to address the needs of rehabilitation
or assistance on upper extremity function. Most of the devices available commercially and in literature are powered by
conventional actuators such as DC motors, servomotors or pneumatic actuators. Some prototypes are developed based on
shape memory alloy (SMA) and dielectric elastomers (DE). This study presents a customizable, 3D printed, a
lightweight exoskeleton (iGrab) based on recently reported Twisted and Coiled Polymer (TCP) muscles, which are
lightweight, provide high power to weight ratio and large stroke. We used silver coated nylon 6, 6 threads to make the
TCP muscles, which can be easily actuated electrothermally. We reviewed briefly hand orthosis created with various
actuation technologies and present our design of tendon-driven exoskeleton with the muscles confined in the forearm
area. A single muscle is used to facilitate the motion of all three joints namely DIP (Distal interphalangeal), PIP
(Proximal Interphalangeal) and MCP (Metacarpophalangeal) using passive tendons though circular rings. The grasping
capabilities, along with TCP muscle properties utilized in the design such as life cycle, actuation under load and power
inputs are discussed.
|