Miniature "Bio-Bots" Made Of Hydrogel And Heart Cells 2012

They're soft, biocompatible, about 7 millimetres long – and, incredibly, able to walk by themselves. Miniature "bio-bots" developed at the University of Illinois are an important step forward in synthetic biology.

Miniature "Bio-Bots" Made Of Hydrogel And Heart Cells 2012

Designing non-electronic biological machines has been a riddle that scientists have struggled to solve for many years. Now, walking bio-bots have been demonstrated by a team at Illinois who have engineered functional machines using only hydrogel, heart cells and a 3-D printer.

With a customised design, the bio-bots could be used for specific applications in medicine, energy or the environment. The research team, led by Professor 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. “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?”

As shown in the video below, the key to the bio-bots' locomotion is their asymmetry. Resembling a tiny springboard, each bot has one long, thin leg resting on a stout supporting leg. The thin leg is covered with rat cardiac cells. When these heart cells beat, the long leg pulses, propelling the bio-bot forward.

The team used a 3-D printing method common in rapid prototyping to make the main body of the 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 will allow them to build and test other configurations with an eye toward potential applications.

For example, Bashir envisions the bio-bots being used for drug screening or chemical analysis, since the bots' 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-bots could be used as sensors.

"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 neutralise it," said 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."

Next, the team will work to enhance control and function – such as integrating neurons to direct motion, or cells that respond to light. They are also working on creating robots of different shapes, 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 also 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."

"I think we are just beginning to scratch the surface in this regard," said Vincent Chan, first author of the paper, which appears in Nature. "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."