Miniaturized Variable Stiffness Gripper Locally Actuated by Magnetic Fields

In minimally invasive surgery, grippers are essential for tissue manipulation. However, in commercial tendon-driven systems, challenges remain, including tendon fatigue and bulkiness. Promising alternatives are magnetically actuated systems, offering contactless steering but limited forces. To overcome this, a miniaturized, locally actuated magnetic gripper with variable stiffness is presented. The gripper employs thin planar coils (75 mu m) and a radially magnetized plunger, enabling local actuation and enhanced orientation control. The variable stiffness compliant mechanism made from shape-memory polymer facilitates different gripping strategies. In its rigid state, pulsed pulling forces of 340 mN and continuous forces of 90 mN are achieved, exceeding the gripper weight by factors of 70 and 18, respectively. The soft state, with a fast response time of 20 ms, enables soft gripping of various targets, including moving ones and rat tissue samples. Demonstrating the applicability, contactless steering and target retrieval within a stomach phantom is showcased. This study introduces promising improvements to magnetically actuated grippers for surgical procedures, addressing key challenges in current designs. A magnetic gripper, locally actuated by planar coils, is proposed. The temperature-dependent stiffness of the employed compliant structure allows for different gripping strategies. In the rigid state, pulling forces up to 70 times its weight are achieved. In the soft state, moving targets are soft-gripped. Demonstrating the applicability, contactless steering and target retrieval within a stomach phantom is showcased.image (c) 2024 WILEY-VCH GmbH