Back in 1961, William S. Burroughs published his novel The Soft Machine. The title referred to the human body and the work was principally concerned with a pair of accounts describing Burroughs' drug abuse and subsequent treatment to check it through the use of apomorphine.
At the time, The Soft Machine was viewed as the speculative and feverish ramblings of an inventive, if literary, drug addict. One chapter of the book, "The Mayan Caper," is a narrative which sees a secret agent change bodies or control the metamorphosis of his own flesh through the use of what Burroughs called "undifferentiated tissue."
Now engineers at the University of Illinois at Urbana-Champaign have created their own Soft Machine and it's a realization of an idea both strange and challenging. The work involves a group of "bio-bots" capable of walking via living muscle cells controlled with electrical pulses.
Rashid Bashir, the head of bioengineering at UI, says his team has perfected what at first seems a process torn straight from the pages of a Burroughs novel.
"Biological actuation driven by cells is a fundamental need for any kind of biological machine you want to build," Bashir said. "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."
The process begins with 3D printing hydrogels and living cells along a flexible spine. The bio-bots are then powered by a strip of skeletal muscle cells which are triggered by electric pulses to provide researchers a simple method of controlling their motion.
"Skeletal muscle cells are very attractive because you can pace them using external signals. 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," Bashir says. "It's part of a design toolbox. We want to have different options that could be used by engineers to design these things."
The 3D printed hydrogel is strong enough to give the devices the necessary structure, but flexible enough to bend like a joint in the human body. The speed of the devices is controlled by adjusting the frequency of electric pulses; higher frequency causes the muscle to contract faster.
Graduate student Caroline Cvetkovic, a co-author of the research findings, says the team chose bio-mimetic design principles as their jumping off point.
"This work represents an important first step in the development and control of biological machines that can be stimulated, trained, or programmed to do work," Cvetkovic said. "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."
The team says 3D printing is the key to an engineers ability to test shapes and designs quickly.
The research was supported by the National Science Foundation, the Massachusetts Institute of Technology, the Georgia Institute of Technology and other partner institutions.