Superelastic compliant mechanisms for needlescopic surgical wrists

The paper discusses the design process of a micro robotic wrist with two rotational and one translational degrees of freedom for needle laparoscopic surgery with 2.5 mm instrument diameter. At such size a few systems have been proposed with small workspace and limited degree of freedom. These functional limitations can be overcome by introducing parallel compliant mechanisms designed for fabrication with MEMS techniques. Use of micro electro discharge machining (mu-EDM) and superelastic alloy can further improve the functional figures. The paper addresses the case of wrist developed for LIGA fabrication with Ni and introduces the case of fabrication with mu-EDM using superelastic NiTi alloy. The wrist is a part of a modular needle laparoscopic instrument comprising a needle tube with actuation wires and rods inside, an end-effector platform to which the surgery tool is connected and a separate actuation unit.