Microrobot swarms use spinning flows to move massive objects

15:20

By: Dakir Madiha

Microrobot swarms use spinning flows to move massive objects

Swarms of magnetic microrobots can now rotate and transport objects tens of thousands of times heavier than a single robot by stirring surrounding liquid instead of pushing directly on their targets. Each microrobot is a tiny disk roughly 300 micrometers across that spins under a controlled magnetic field, creating circulating fluid flows that act like invisible gears around nearby structures. By tuning how fast the disks spin, how many are active, and how they are arranged, researchers can precisely adjust the intensity and direction of the fluidic torque they generate. In laboratory tests, these collectives produced torques up to about 3.6 × 10⁻⁹ newton-meters, enough to rotate objects more than 45,000 times the mass of a single robot without any physical contact.

In a series of demonstrations, the microrobot swarms drove individual gears, powered gear trains, and turned complex three-dimensional structures floating on a small pool of liquid. When the robots were placed beneath a heavy 3D object at the liquid interface, the combined fluid flow was sufficient to set the entire structure spinning, despite the huge size and weight difference between the robots and the load. The same mechanism enabled the swarm to assemble and disassemble ring-shaped structures, as well as to reorganize multiple objects at once through carefully choreographed flow fields. Researchers describe this strategy as fluidic torque-enabled manipulation, arguing that it offers a programmable, scalable alternative to traditional micromanipulation methods that rely on direct contact or mechanical tools.

The microrobot collectives also displayed striking emergent behavior, changing their own shape and motion depending on how fast they were driven. At higher spin frequencies, the robots tended to spread out and wrap around an object, forming a rotating ring that efficiently transferred torque through the fluid. At lower speeds, they clustered together and crawled along edges, with the surrounding flow reshaping the swarm as it moved. In dense configurations, the swarms could alternately expel or absorb nearby particles, acting as a kind of programmable fluid engine that switches between pushing objects away and drawing them inward by simply changing the rotation speed. The team sees these behaviors as evidence that fluidic torque can serve as a unifying mechanism for both object manipulation and collective self-organization at the microscale.

Scientists involved in the work say the approach could transform how delicate components are handled in microscale manufacturing and biomedical settings. Because the robots do not need to touch what they move, the risk of damaging fragile parts or sensitive biological samples is reduced, and multiple objects can be actuated simultaneously within the same fluid environment. Potential applications include assembling tiny devices, transporting cells or tissue samples, and performing targeted interventions inside liquid-filled spaces such as microfluidic chips or even the human body. While the current experiments occur at a fluid–air interface, the underlying hydrodynamic interactions should translate to fully submerged or liquid–liquid environments, with viscosity mainly affecting how the behavior scales. The researchers argue that as control strategies improve, swarming microrobots powered by fluidic torque could evolve into versatile tools for complex, high-precision tasks in science, medicine, and industry.