It sounds like something dreamt up by a science fiction writer, but scientists have created a walking ‘bio-bot’ made from rat heart cells and hydrogels, using a 3-D printer.

The biological machines are 7 millimetres long, and resemble a miniature springboard with one long, thin leg that is supported by a stouter supporting leg. The thin leg is covered in rat heart cells which, when they beat, cause the long leg to pulse, propelling the bio-bot forward.

The research was conducted by scientists at the University of Illinois, and published in the journal Scientific Reports.

A biological machine is any sort of biological material, such as animal cells, that is engineered to produce a highly specific function. Bio-bots such as this one have many potential applications in security, environment, and health applications, such as organ mimics for drug testing.

”The idea is that, by being able to design with biological structures, we can harness the power of cells and nature to address challenges facing society,” said Rashid Bashir, a professor of engineering at the University of Illinois who led the team.

”As engineers, we’ve always built things with hard materials, materials that are very predictable. Yet there are a lot of applications where nature solves a problem in such an elegant way. Can we replicate some of that if we can understand how to put things together with cells?”

The rat heart muscles cells were seeded onto the cantilever hydrogel – the thin leg. Their spontaneous contraction over several days provided the power that moved the bot forward. Hydrogels are a network of polymer chains that are very flexible like natural tissue, and are often used as scaffolds in tissue engineering.

By using a 3-D printer, the team was able to rapidly adjust and experiment with the design of the bot, for maximum speed. It also allowed them to make manufacture the biological machines with greater precision.

The team are hoping that the bio-bots could be used for drug screening or chemical analysis as their motion can indicate how the cells are responding to the environment.

”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,” says Bashir.

“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.”

To see a video of the bio-bots in action click here.