Using a 3D printer, researchers at the University of Illinois have developed synthetic "bio-bots" about seven millimeters long that are powered by embedded cardiac cells that give them the ability to "walk" on their own. The researchers say they are just scratching the surface of what is possible, with their work potentially leading to millimeter-scale medical or environmental sensors that that can seek out and neutralize harmful toxins.

The bio-bots, which are made primarily out of a flexible hydrogel, move using a long leg that acts like a flagellum. The leg is coated with heart cells from the common rat so that when the cells beat, they cause the leg to swing, thrusting the robot forward. For now, the bio-bot is only able to move forward at a fairly constant rate, but the team hopes they'll be able to control the robot's movements by adding neurons, or cells that react to light. Cells that respond to specific chemicals could also give the bio-bots sensor-like qualities.

“Our goal is to see if we can get this thing to move toward chemical gradients, so we could eventually design something that can look for a specific toxin and then try to neutralize it,” said Rashid Bashir, a professor of engineering and director of the Micro and Nanotechnology Laboratory. “Now you can think about a sensor that’s moving and constantly sampling and doing something useful, in medicine and the environment. The applications could be many, depending on what cell types we use and where we want to go with it.”

The researchers say rapid-prototyping their designs on a 3D printer was instrumental in engineering faster bio-bots, and they're already looking to shapes with multiple legs, which could help the bots climb. However, there is still much more work to be done.

“We have the design rules to make these millimeter-scale shapes and different physical architectures, which hasn’t been done with this level of control," said Bashir. "What we want to do now is add more functionality to it.”

The team's work appears in the journal Scientific Reports and you can see the bio-bot in action in the following video.