Reliable Grasping of Three-Dimensional Untethered Mobile Magnetic Microgripper for Autonomous Pick-and-Place

Manipulation of micrometer to millimeter-scale objects is central to biotechnological and medical applications involving small-scale robotic devices. Mobile untethered microgrippers have been developed, which use magnetic fields for motion and activation of grasping. This letter extends the capabilities of such microgrippers by presenting the first example of reliable and autonomous three-dimensional (3-D) micrograsping and cargo delivery of amicrogripper using simple control strategies. This endeavor will allow microgrippers to reliably grasp and transfer microobjects, such as cells, with minimal user input, which is ideal for cooperative tasks performed by multiple microgrippers in future work. The proposed controller autonomously manipulates a 3-D magnetic microgripper for pick-and-place tasks in the 3-D space. By regulating the remotely applied force on the microgripper, the 3-D position and velocity of the microgripper are controlled, and the microgripper grasping, i.e., opening and closing, is determined by the magnetic field strength. In experiments, the microgripper successfully grasps cargoes with cubic, irregular, triangular, and beam shapes using at most 5, 8, 20, and 24 attempts, respectively. The microgripper shown here demonstrates fast grasping due to their complete magnetic actuation method. Moreover, a preliminary cell viability test suggests that the microgripper has no adverse effects on living cells. This study proves the proposed microgripper and controller to be agile and reliable tools for biomedical tasks.