The biological machines designed by researchers from University of Illinois take machines to a whole new level. These machines called bio-bots measure 7 millimeters in length and are soft, biologically compatible and have the ability to walk.

Researchers say they built these miniature bio-bots using only hydrogel, heart cells and a 3-D printer. The autonomous bio-bot is powered by the heart cells.

"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. 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?" said Rashid Bashir, from University of Illinois.

Researchers say that the bio-bots can be used in the fields of medicine and environment. In medicine, they can be used to test drugs or analyze chemicals. These bots can be integrated with certain cells that are known to respond to certain stimuli, thus creating a fusion of cell and a man-made structure that can be used as a sensor.

"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 Bashir in a statement. "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."

Since the researchers used a 3D printing method to make the body of the bio-bot using a hydrogel, they were able to modify the design to suit movement requirements. In the future, researchers will be trying out bio-bot models that can walk on slopes or climb stairs.

"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 utilize it for other beneficial purposes or functions," said Vincent Chan, graduate student and first author of the paper.

The study is published in the journal Scientific Reports.