Design and fabrication of a shape memory alloy actuated exoskeletal microarm

This paper reports the design and fabrication process and control system of an exoskeletal microarm. The research of the microarm is part of a new concept of endoscopes designed for endoscopic submucosal dissection (ESD) operation. This novel ESD endoscope has two suction grippers to hold the lesion skin, and a cautery knife to cut. The grippers and cautery knife are actuated by shape memory alloy (SMA). SMA is known for its high work output unit volume and its high power/mass ratio. Plus, its exoskeletal link mechanism enables to calculate the position of its end tip, necessary for the control of the grippers and the knife. The microarm is composed of polydimethylsiloxane (PDMS) using soft lithography technique. The microarm is coated with hardening epoxy polymer, leaving only the joint part of the microarm uncoated. The microarm´s bending angle is controlled by PID control system where SMA´s electrical resistance change is used as a feedback parameter. The fabricated exoskeletal microarm successfully bent in a joint, and its angle was able to control under the PID control system.