University of Illinois (UI) researchers have developed minuscule soft robot machines, dubbed “the swimmer,” that are made of artificial and biological components that swim around when exposed to light. It’s a promising development as it brings researchers in mechanical engineering one step closer to creating autonomous biobots. Their study has been published in the Proceedings in the National Academy of Sciences.
An artist’s rendering of the minuscule 1mm-wide soft robot that’s capable of swimming around when exposed to light. (Image Credit: Michael Vincent)
Back in 2014, both mechanical science and engineering professor Taher Saif and bioengineering professor Rashid Bashir at the University of Illinois collaborated together to develop the first biohybrid swimming and walking biobots powered by cardiac tissue derived from rats.
"Our first swimmer study successfully demonstrated that the bots, modeled after sperm cells, could in fact swim," Saif said. "That generation of singled-tailed bots utilized cardiac tissue that beats on its own, but they could not sense the environment or make any decisions."
Engineers modeled different body shapes to find out which shape swims better. In their new studies, researchers eventually developed tiny robots with two flagellar tails, measuring only 1mm in width, which is powered by skeletal muscles stimulated by motor neurons. When the neurons, which have optogenetic properties, become exposed to light, they will become triggered to actuate the muscles.
Overall, the swimmer is only 3.2mm in size from head to tail, but when comparing it to uni-cellular organisms, the biohybrid is actually gigantic. The robotic device is quite slow too, but to make it swim around quickly, it will be shrunk down in size.
"We applied an optogenetic neuron cell culture, derived from mouse stem cells, adjacent to the muscle tissue," Saif said. "The neurons advanced towards the muscle and formed neuromuscular junctions, and the swimmer assembled on its own."
Once they confirmed there was compatibility with the neuromuscular tissue and their biobot skeletons, the team worked on enhancing the robotic device’s abilities.
"The ability to drive muscle activity with neurons paves the way for further integration of neural units within biohybrid systems," Saif said. "Given our understanding of neural control in animals, it may be possible to move forward with biohybrid neuromuscular design by using a hierarchical organization of neural networks."
While tests were being carried out, the team realized their development isn’t just a machine, but it’s similar to a living creature. After about 20 seconds of swimming around, it started to experience fatigue, which is also another limit the team needs to overcome. Due to the lack of oxygen or glucose in the cells, the machine tired out quickly and became inoperable. However, after the robot rested for just a minute, it made a full recovery and began functioning again.
Saif and his team hope the advance in technology and biobots lead to the development of multicellular engineered living systems that’s smarter and capable of responding to different environmental cues in bioengineering, medicine, and self-healing materials. The team is also aware that no two biohybrid devices that perform the same function will ever be the same.
"Just like twins are not truly identical, two machines designed to perform the same function will not be the same," Saif said. "One may move faster or heal from damage differently from the other—a unique attribute of living machines."
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