A U-shaped robotic gripper with displacement and deformation controlled by programmable magnetic fields

Magnetic soft robots are widely employed in micromanipulation applications because of their inherent biocompatibility, untethered actuation capabilities, and controllability. This study presents the fabrication and application of a U-shaped robotic gripper (U-SRG) and experimentally verifies the control performance of a magnetic control system for two-dimensional (2D) rotation, translational motion, deformation, and microsphere grasping. The magnetic component of the U-SRG was fabricated by doping polydimethylsiloxane with neodymium-iron-boron (NdFeB) powder, followed by molding via post-treatment with Ecoflex-30 elastic silicone. The magnetic field generated by the electromagnetic coils of a magnetic control system can be conveniently, quickly, and precisely regulated using computers. Moreover, a uniform magnetic field could be precisely steered within a 2D plane, and the deformation magnitude of the U-SRG could be tuned by adjusting the intensity of the uniform magnetic field. The planar motion of the U-SRG was controlled by a synthetic magnetic field, and its speed was adjusted according to the magnitude of the magnetic field gradient. The magnitude and direction of the magnetic field required for each segment of the U-SRG path can be preset using computer software, enabling the U-SRG to precisely grasp and release the microspheres. To improve the micro-object grasping efficiency of the U-SRG, a crab-inspired gripper, denoted as U-SRGs, was developed by optimizing the design of the U-SRG. The bioinspired design does not directly replicate the external morphology of crab claws; instead, it draws inspiration from the functional differentiation of paired crab chelae, which can cooperate while exhibiting different grasping roles. This biological principle was translated into an asymmetric magnetic design strategy for the U-SRGs. By asymmetrically doping the left and right fingers of the U-SRGs with NdFeB powder, the gripper achieved differentiated clamping deformation under a uniform magnetic field. Owing to this capability, U-SRGs can realize size-based screening, manipulation, and targeted delivery of micro-objects.