These pictures show the flexible body of the robot, made from skeletal muscle tissue and a clear flexible silicone substrate, attached to the weighted 3D printed legs and feet. Credit: 2024, Kinjo et al., Matter
Key points:
- A new two-legged biohybrid robot is capable of walking and pivoting underwater.
- The key to the new robot is the combination of an artificial skeleton and biological muscle.
- The researchers foresee creating iterations that can walk on land by using thicker muscles with their own nutrient supplies.
Combining an artificial skeleton with biological muscle, researchers at the University of Tokyo have created a two-legged biohybrid robot that is capable of walking and pivoting underwater—overcoming previous limitations.
Typical biohybrid robots can move in straight lines or perform large turns, but struggle to carry out finer movements in smaller spaces. This makes them unusable in areas with many obstacles, such as in search and rescue operations.
However, this new robot can pivot on one foot, enabling it to turn within a small circle. At present, it can only work underwater as the lab-grown muscle dries out quickly when exposed to air, losing effectiveness. However, the researchers foresee creating iterations that can walk on land by using thicker muscles with their own nutrient supplies and possibly covering them in artificial skin.
According to their study, published in Matter, the researchers began by growing skeletal muscle in molds 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 handheld gold electrodes to deliver a charge. This caused the muscle tissue to contract and the robot to “walk” when the legs were stimulated one after the other. By stimulating each leg at 5-second intervals, the team was able to move the robot at a speed of 5.4 millimeters per minute—comparable to that of other biohybrid robots.
The team is now working on how to create a smoother-moving robot that can walk on land by developing methods to stimulate the muscles remotely and creating thicker muscles with a nutrient supply to sustain them.