The cardiac cells of rats have been used to propel biological machines that could one day be employed in drug screening or chemical analysis.

The so-called ‘bio-bots’ developed at Illinois University are said to represent an advance in synthetic biology and demonstrate the team’s ability to forward-engineer functional machines using only hydrogel, heart cells and a 3D printer.

The team claims that, with an altered design, the bio-bots could be customised for specific applications in medicine, energy or the environment. The research team, led by Prof Rashid Bashir, published its results in the journal Scientific Reports.

‘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 Bashir, an Abel Bliss professor of engineering at Illinois. ‘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?’

Resembling a tiny springboard, each bio-bot has one long, thin leg resting on a supporting leg. The thin leg is covered with rat cardiac cells. When the heart cells beat, the long leg pulses, propelling the bio-bot forward.

The team uses a 3D printing method common in rapid prototyping to make the main body of the bio-bot from hydrogel — a soft, gelatin-like polymer.

This approach allowed the researchers to explore various conformations and adjust their design for maximum speed. The ease of quickly altering design also will allow them to build and test other configurations for further potential applications.

Bashir envisions the bio-bot being used for drug screening or chemical analysis, since its motion can indicate how the cells are responding to the environment. By integrating cells that respond to certain stimuli, such as chemical gradients, the bio-bot could be used as sensors.

‘Our goal is to see if we can get this thing to move towards chemical gradients, so we could eventually design something that can look for a specific toxin and then try to neutralise it,’ he said. ’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.’

Next, the team will work to enhance control and function, such as integrating neurons to direct motion or cells that respond to light. The researchers are also working on creating robots of different shapes and with different numbers of legs and robots that could climb slopes or steps.

‘The idea here is that you can do it by forward engineering,’ said Bashir, who is the director of the Micro and Nanotechnology Laboratory. ‘We have the design rules to make these millimetre-scale shapes and different physical architectures, which hasn’t been done with this level of control. What we want to do now is add more functionality to it.’

Graduate student Vincent Chan, first author of the paper, said: ‘I think we are just beginning to scratch the surface in this regard. That is what’s so exciting about this technology — to be able to exploit some of nature’s unique capabilities and utilise it for other beneficial purposes or functions.’