Typical biohybrid robots can move in straight lines or perform large turns but struggle to carry out finer movements in smaller spaces, which makes them unsuitable for use in areas with several obstacles.
Developed by a team from the Graduate School of Information Science and Technology at the University of Tokyo, the new robot can pivot on one foot, enabling it to turn within a small circle. Currently, it can only work underwater as the lab-grown muscle dries out when exposed to air. The researchers believe it will be possible to create future iterations that can walk on land by using thicker muscles with their own nutrient supplies and possibly cover them in artificial skin. Their findings are detailed in Matter.
In a statement, Professor Shoji Takeuchi, a specialist in biohybrid systems, said: “By incorporating living tissues as part of a robot, we can make use of the superior functions of living organisms. In our latest research, we combined lab-grown skeletal muscle tissue with flexible artificial legs and 3D-printed feet. Using the muscle tissue to move the legs allowed us to create a small robot with efficient, silent movements and a soft touch.”
The researchers began by growing skeletal muscle in moulds to create strips. The muscle tissue loses its ability to move when it becomes too dry, so the robot was designed to be suspended in water. The team made a lightweight skeleton from a floating styrene board, a flexible silicone-based body, acrylic resin legs with brass wire weights, and 3D-printed feet. Two strips of muscle tissue were attached from the body to the feet of the robot, completing the legs.
Each leg was stimulated using hand-held gold electrodes to deliver a charge, which caused the muscle tissue to contract and the robot to “walk”. By stimulating each leg at five-second intervals, they were able to move the robot at a speed of 5.4mm per minute, which is said to be comparable to other biohybrid robots.
“Initially, we weren't at all sure that achieving bipedal walking was possible, so it was truly surprising when we succeeded,” said Takeuchi. “Our biohybrid robot managed to perform forward and turning movements with a bipedal walk by effectively balancing four key forces: the muscle contractile force, the restorative force of the flexible body, the gravity acting on the weight, and the buoyancy of the float.”
The team is now considering how to create a smoother-moving robot that can walk on land by developing methods to stimulate the muscles remotely.
Takeuchi said: “We're working on designing robots with joints and additional muscle tissues to enable more sophisticated walking capabilities. Our findings offer valuable insights for the advancement of soft flexible robots powered by muscle tissue and have the potential to contribute to a deeper understanding of biological locomotion mechanisms, further enabling us to mimic the intricacies of human walking in robots.”
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