“Electrostatic robots have an advantage in that their power is supplied through an electrode array that the microrobots sit on,” says Gorman. “It can be very compact. Therefore, electrostatic microrobots can be embedded inside other things [like computer chips]. For magnetic robots, you have to supply electromagnetic field, and that requires a larger set-up.” Others have worked on electrostatic microrobots, he adds, but this work is the furthest along.
“His research is very advanced in terms of controlling multiple microrobots,” says Zoltan Nagy, a roboticist at ETH Zürich who works with groups of magnetically controlled robots called Magmites.
“Most of the work to date has been on controlling a single robot that can move around in a pre-defined area on a substrate,” adds Gorman. “However, many of the applications of interest will require control of lots of robots, like a colony of ants.”
So far, Paprotny has been able to control up to four robots on a single surface at once, and the robots can move several thousand times their body length per second, as detailed in a paper that is currently submitted for review. His next plan is to adapt the setup for a liquid environment so that the microrobots can assemble components of biological tissue into patterns that mimic nature.
“We’re trying to come up with ways of self-assembling tissue units,” says Ali Khademhosseini, an associate professor at Brigham and Women’s Hospital at Harvard Medical School and a specialist in tissue engineering who is collaborating with Paprotny. “In the body, tissues are made in a hierarchical way—units repeat themselves over and over to generate larger tissue structures.” Muscle tissue, for example, is made from small fibers, while liver tissue has a repeating hexagonal shape.
Khademhosseini has encased cells in jelly-like hydrogels and assembled them (using methods that include liquid-air interactions and surface tensions) into different regions to mimic biological tissues. But he thinks the self-assembling microrobots will allow more control in creating the tissues.
“We can try to combine cells and materials in microfabrication systems to come up with structures and assemble them in particular ways using the techniques Igor has developed,” says Khademhosseini.
He envisions fabricating the gels and cells on top of teams of robots working in parallel to construct different parts of a tissue. “We could use the robots to do assembly,” he says. “The cells, once they’re assembled, come off from the robots, letting cells rearrange further to make things that are indistinguishable from natural tissue.” Initially, he hopes to create small patches of heart tissues, and then things like heart muscles and valves, and assemble them all together in a heart. “That’s where things are heading,” he says. “But right now the challenge is we’re still not very good at making each of these individual components.”