Microrobots that can grasp and transport objects four times their own weight

New Scientist : In a study published in Nature Materials, two physicists at Argonne National Laboratory, Alexey Snezhko and Igor Aronson, describe the creation of tiny robots, just half a millimeter wide, from microparticles suspended between two layers of immiscible fluids. When they apply a magnetic field perpendicular to the liquid surface, the particles self-assemble into star shapes, or asters. Applying a second magnetic field parallel to the surface causes the asters to swim. By changing the magnetic field, the researchers can remotely control the asters’ motion. “We can make them open their jaws and close them,” said Snezhko in a press release . “This gives us the opportunity to use these creatures as mini-robots performing useful tasks. You can move them around and pick up and drop objects.” The asters have several advantages over other micromanipulators: They can handle items more delicately than their mechanical counterparts, and they are self-repairing—if particles are lost, the remaining particles simply reshuffle themselves.