Design of a micro robotic wrist for needle laparoscopic surgery

This paper addresses the design of a microwrist for needle laparoscopic surgery (needlescopy) using microelectromechanical system technology and an original three degree of freedom, 3D architecture. Advancement in needlescopy drives the development of multi-DOF microtools 1-2 mm in diameter with 3D mobility but standard available fabrication techniques are for 2.5D structures. Thus paper discusses the development steps and design solutions for the realization of the 3D wrist with available technology. A compliant mechanism is used, which is derived from a reference parallel kinematics mechanism architecture with three legs. A singular configuration of increased instantaneous mobility is exploited to achieve the desired 3D mobility. Alternative leg architectures are investigated to obtain satisfactory performance. The legs are fabricated as monolithic compliant structures and assembled to wrist base and end-effector. The definition of the leg geometry revealed a complex task. The steps to obtain the final design satisfying task requirements are detailed.