By Liz Ahlberg
A new generation of miniature biological robots is flexing its muscle.
Engineers at the University of Illinois at Urbana-Champaign demonstrated a class of walking “bio-bots” powered by muscle cells and controlled with electrical pulses, giving researchers unprecedented command over their function. The group published its work in the online early edition of Proceedings of the National Academy of Science.
“Biological actuation driven by cells is a fundamental need for any kind of biological machine you want to build,” said study leader Rashid Bashir, Abel Bliss Professor and head of bioengineering at the U. of I. “We’re trying to integrate these principles of engineering with biology in a way that can be used to design and develop biological machines and systems for environmental and medical applications. Biology is tremendously powerful, and if we can somehow learn to harness its advantages for useful applications, it could bring about a lot of great things.”
Bashir’s group has been a pioneer in designing and building bio-bots, less than a centimeter in size, made of flexible 3-D printed hydrogels and living cells. Previously, the group demonstrated bio-bots that “walk” on their own, powered by beating heart cells from rats. However, heart cells constantly contract, denying researchers control over the bot’s motion. This makes it difficult to use heart cells to engineer a bio-bot that can be turned on and off, sped up or slowed down.
The new bio-bots are powered by a strip of skeletal muscle cells that can be triggered by an electric pulse. This gives the researchers a simple way to control the bio-bots and opens the possibilities for other forward design principles, so engineers can customize bio-bots for specific applications.
“Skeletal muscles cells are very attractive because you can pace them using external signals,” Bashir said. “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.”
The design is inspired by the muscle-tendon-bone complex found in nature. There is a backbone of 3-D printed hydrogel, strong enough to give the bio-bot structure but flexible enough to bend like a joint. Two posts serve to anchor a strip of muscle to the backbone, like tendons attach muscle to bone, but the posts also act as feet for the bio-bot.