Today, robots can be powered by all kinds of energy sources, from solar cells to chemical fuels to rechargeable batteries. What’s next? A generation of machines powered biologically, using muscle cells that expand and contract just as they do in the human anatomy.
These “bio-bots,” less than one centimetre long, can be precisely controlled because their muscle cells move in reaction to an electric field. The bio-bots walk faster or slower in correlation with the rate of the electric pulses signalled by engineers.
Each bio-bot is comprised of a flexible 3D printed hydrogel base, living muscle cells and two posts that serve as legs. Like the muscle-tendon-bone system in the natural world, the hydrogel structures the bio-bot as a backbone, the cells provide the muscular support and the posts act as tendons.
While biological machines have certainly been engineered before, this new group is the most efficient to date. Bio-bots were first made to walk using heart cells from rats, but because of the heart’s autonomous beating, scientists were unable to control the expansion and contraction that powered the movement.
The research team at the University of Illinois at Urbana-Champaign discovered that skeletal muscle cells provide a better alternative, as they allow the engineers to power the bots on and off and control speed by varying the electric current.
Rashid Balir, leader of the bio-bot study, explained further: “Skeletal muscles cells are very attractive because you can pace them using external signals. For example, you would use skeletal muscle when designing a device that you wanted to start functioning when it senses a chemical or when it received a certain signal.
“To us, it’s part of a design toolbox. We want to have different options that could be used by engineers to design these things.”
So far, muscle power seems to be a promising technology with a wide range of potential medical and environmental uses.
“It’s exciting to think that this system could eventually evolve into a generation of biological machines that could aid in drug delivery, surgical robotics, ‘smart’ implants, or mobile environmental analyzers, among countless other applications,” said Caroline Cvetkovic, co-first author of the study’s publication.
To make these applications a reality, engineers will continue to hone their control over the bio-bots, implementing neurons within their structures to enable steering capabilities.
Since 3D printing allows for the speedy production of differently shaped hydrogels, the researchers can easily experiment with various models.
Soon, they hope to create a hydrogel backbone that can change directions as a result of different kinds of signals, further expanding the functionality of these “living” machines.