Combining lab-grown muscle tissue with a series of flexible mechanical joints has led to the development of an artificial hand that can grip and make gestures. The breakthrough shows the way forward for a new kind of robotics with a range of potential applications.
While we've seen plenty of soft robots at New Atlas and a truly inspiring range of mechanical prosthetics, we've yet to see too many inventions that quite literally combine human tissue with machines. That's likely because the world of biohybrid science is still in its very early stages. Sure, there was an artificial fish powered by human heart cells and a robot that used a locust's ear to hear, but in terms of the practical use of the technology, the field has remained somewhat empty.
Now though, researchers at the University of Tokyo and Waseda University in Japan have shown a breakthrough demonstrating the real promise of the technology.
To create their biohybrid hand, they first grew a series of muscle fibers in the lab. Because, on their own, the tissues wouldn't be strong enough to function well without tearing, the researchers bundled them together in what they've termed multiple tissue actuators or MuMuTAs. These tissues were then attached to a 3D-printed plastic hand having moveable joints and measuring about 18 cm (7 in) long.
"Our key achievement was developing the MuMuTAs," said Shoji Takeuchi from the University of Tokyo. Takeuchi is the co-author of a study describing the creation that has been published in the journal, Science Robotics. "These are thin strands of muscle tissue grown in a culture medium and then rolled up into a bundle like a sushi roll to make each tendon. Creating the MuMuTAs enabled us to overcome our biggest challenge, which was to ensure enough contractile force and length in the muscles to drive the hand’s large structure."
Once the MuMuTAs were connected to the artificial hand, the researchers stimulated them using electrical currents. In this way, they were successfully able to get the hand to form a scissor gesture and to grasp and manipulate the tip of a pipette.
Perhaps most fascinating of all, the team found that, just like a human hand, the biohybrid model got "tired" after being used, with the force of the tissue declining with time.
"While not entirely surprising, it was interesting that the contractile force of the tissues decreased and showed signs of fatigue after 10 minutes of electrical stimulation, yet recovered within just one hour of rest," said Takeuchi. "Observing such a recovery response, similar to that of living tissues, in engineered muscle tissues was a remarkable and fascinating outcome."
Takeuchi and his team admit that their hand is really more just a proof of concept than a useable device and that it has a ways to go before its functionality increases, For example, during the study, the entire hand was floated in a liquid in order to allow the joints to move with as little friction as possible. The suspension also allowed the segments of the hand to float back to a neutral position after being flexed by the lab-grown tendons, although the team says adding elastic or more MuMuTAs oriented in the opposite direction could overcome that issue.
Still, the researchers say that by bundling tissue together, their invention overcomes a significant hurdle in the scalability of biohybrids. Previously such devices couldn't get much bigger than a centimeter or so (about a half inch), so an 18 cm-long hand is quite a leap forward.
"A major goal of biohybrid robotics is to mimic biological systems, which necessitates scaling up their size," said Takeuchi. "Our development of the MuMuTAs is an important milestone for achieving this. The field of biohybrid robotics is still in its infancy, with many foundational challenges to overcome. Once these basic hurdles are addressed, this technology could be used in advanced prosthetics, and could also serve as a tool for understanding how muscle tissues function in biological systems, to test surgical procedures or drugs targeting muscle tissues."
Source: University of Tokyo
