Cable-Less, Magnetically Driven Forceps for Minimally Invasive Surgery

In this letter, a novel end-effector for surgical applications is presented that uses magnetic actuation in lieu of a more traditional cable-driven tool with the goal of providing high dexterity in hard-to-reach locations by decoupling the tool actuation from the rest of the surgical system. The gripper and wrist device consists of several magnets connected with compliant Nitinol joints that allow two rotational degrees of freedom and one gripping degree of freedom. As an end-effector for an existing surgical robot arm, this device could augment existing minimally invasive surgical robots by allowing high distal dexterity in surgical sites with narrow and restricted access. A static deflection model of the device is used to design an open-loop controller. The current prototype is capable of exerting pushing/pulling forces of 9 mN and gripping forces of 6 mN when magnetic flux densities of 20 mT are applied by a laboratory-scale electromagnetic coil system. These forces could be greatly amplified in a clinical-scale system to make brain tissue resection feasible. Under open-loop control, the wrist of the device can maneuver from +pi/4 to -pi/4 rad in less than 1 s with a maximum error of 0.12 rad.