Robots small enough for microscale tasks are too small to carry computers, so Cornell engineers have turned to collective physics instead. In Science Advances, a team co-led by Kirstin Petersen of Cornell's Department of Electrical and Computer Engineering and Metin Sitti of the Max Planck Institute for Intelligent Systems describes swarms of spinning microrobots that manipulate their surroundings through the fluid flows they generate, no physical contact required.
Each robot is a 3D-printed polymer disc about 300 micrometres across, coated with a thin ferromagnetic layer. Floating on a small pool of water and exposed to oscillating orthogonal magnetic fields, every disc spins on its axis, and together the swarm, from ten robots up to a thousand, produces fluid-driven torque. Adding more robots strengthens the flows. The researchers demonstrated swarms rotating concentric rings, driving gears, grippers and rack-and-pinion mechanisms, and absorbing and expelling dozens of passive objects.
The experiments, paired with simulations led by Gaurav Gardi, also revealed a surprise: around comparatively large rotating objects a few millimetres long, the robots clustered to one side and crawled around the perimeter at certain frequencies, an emergent state that could support controlled transport at small scales. Because the approach manipulates objects gently through flow rather than contact, the researchers see promise in biomedical procedures and in driving millimetre-scale machines without building integrated devices.