Researchers from the University of Illinois have produced a new generation of muscle-powered biological robots, or “bio-bots,” that can be stimulated to walk using electrical impulses. These robots not only represent a significant advancement in the field of soft biorobotics, but they may also eventually have uses in a variety of applications including drug screening and delivery systems. The study has been published in PNAS.
The marriage of soft robotics with living biological components, such as cells and tissues, permits the development of machines that are able to sense and respond to a variety of controlled environmental stimuli. “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,” said lead researcher Rashid Bashir in a news-release.
In order to produce these centimeter-scale robots that are capable of locomotion, the team combined 3D printing with tissue engineering. Bashir’s group first demonstrated the capabilities of this technology with a biorobot produced using living heart cells from rats. As the cells contracted, the robot would move, or walk, along a surface in fluid. Unfortunately, however, these robots were limited in their usefulness given the fact that the cells were constantly beating, so they couldn’t switch the robot off.
In search of greater locomotion control, the researchers turned to skeletal muscle cells. “Skeletal muscle cells are very attractive because you can pace them using external signals,” said Bashir. “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.”
The researchers started off by using the native configuration of the musculoskeletal system as a rough blueprint for their designs. They first used 3D printing to generate a backbone of strong yet supple hydrogel and then attached a strip of engineered mammalian skeletal muscle via posts which behaved like tendons. Using electrical stimulation they were then able to trigger the cells in the muscle to contract, resulting in locomotion. By adjusting the frequency of the pulses, the team was able to manipulate the speed of movement.
“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,” said co-first author Caroline Cvetkovic. “It’s exciting to think that this system could eventually evolve into a generation of biological machines that could aid in drug delivery, surgical robots, ‘smart implants’, or mobile environmental analyzers, among countless other applications.”
The next stage involves building on this foundational work in order to achieve better control of locomotion. For example, if they could incorporate neurons into the bio-bot then they may be able to guide the machine using light or chemicals. According to Bashir, the ultimate goal is to be able to use these machines as autonomous sensors. “We want it to sense a specific chemical and move towards it, then release agents to neutralize the toxin, for example,” he added.
—[*Also see](http://www.pnas.org/content/early/2014/06/26/1401577111) [Learn more here](http://news.illinois.edu/news/14/0630biobots2_RashidBashir.html)