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Each ‘microrobot’ is shaped like a spatula but with dimensions measuring just microns, or millionths of a meter. They are almost 100 times smaller than any previous robotic designs of their kind and weigh even less
Bruce Donald, a Duke professor of computer science and biochemistry said "It's marvellous to be able to do assembly and control at this fine a resolution with such very, very tiny things”,
Propelling themselves across such surfaces in an inchworm-like fashion impelled by a "scratch-drive" motion actuator, the microrobots advance in steps only 10 to 20 billionths of a meter each, but repeated as often as 20,000 times a second.
The microrobots can be so small because they are not encumbered by leash-like tethers attached to an external control system. Built with microchip fabrication techniques, they are each designed to respond differently to the same single "global control signal" as voltages charge and discharge on their working parts.
This global control is akin to ways proteins in cells respond to chemical signals, said Donald, who also uses computer algorithms to study processes in biochemistry and biology.
In their new reports, the team shows that five of the microrobots can be made to advance, turn and circle together in pre-planned ways when each is built with slightly different dimensions and stiffness.
Following a choreography mapped out with the aid of mathematics, the microdevices ultimately assemble into group micro-huddles that could set the stage for something more elaborate.
"Initially, we wanted to build something like a car that could drive around at the microscopic scale," Donald said. "Now what we've been able to do is create the first microscopic traffic jam."
He said it took him and various colleagues from 1997 to 2002 to create a microrobot that can operate without a tether, three more years to make the devices steer under global control, and another three to independently manoeuvre more than one at a time.
"The hard thing was designing how multiple microrobots can all work independently, even while they receive the same power and control," he said.