Watch This Robot Made From Silicon and Lab-Grown Muscle Walk Across Its Tank

Compared to humans, a robot’s movements can be clanky and imprecise. That’s because instead of relying on muscles, which exert very fine control and action tiny movements, most robots have to find a way to make precise movements using only motors and rigid components.

To build more nimble robots, scientists are beginning to explore the development of so-called “biohybrid robots”, which combine artificial materials with muscle tissues to move around.

In a new paper published in the journal Matter, researchers from the University of Tokyo report the development of a new biohybrid robot that can walk on two legs like a human. Their robot, which walks underwater through a culture medium, can also pivot on one “leg” and make tighter turning circles than other types of biohybrid robots.

Building a biohybrid robot

Many different biohybrid robots have been developed. Most of these move by either utilizing cultured muscle tissues to propel themselves along through water in a swimming motion or by “crawling” along solid ground.

“Research on biohybrid robots, which are a fusion of biology and mechanics, is recently attracting attention as a new field of robotics featuring biological function,” said study author Professor Shoji Takeuchi of the University of Tokyo, Japan. “Using muscle as actuators allows us to build a compact robot and achieve efficient, silent movements with a soft touch.”

While these existing robots are very efficient, silent and mobile, they aren’t particularly nimble. They can make turns, but not sharp ones like a human can.

The new biohybrid robot developed by Takeuchi’s team is bi-pedal and mimics the human walking gait. It is built to operate underwater, with a foam buoy “torso” and weighted legs that help it to stand upright when submerged in a culture medium. The robot’s skeleton is made from flexible silicone rubber, featuring anchor points where strips of lab-grown skeletal muscle tissue can be attached.

New biohybrid robot makes very fine turning motions

To make their robot walk, electrodes are brought into contact with the lab-grown muscle tissue on each leg in turn, giving them a quick jolt of electricity. This causes the muscle to contract, lifting its corresponding leg up from the base of the vessel. When the muscle relaxes again, the movement of the weight attached to the lifted leg causes the robot to lean forward slightly and land with that leg slightly ahead of its previous position. Repeating this with the other leg creates a human-like walking gait.

By alternating the electric shocks between the right and left leg every five seconds, the researchers were successfully able to walk the robot at a speed of 5.4 millimeters per minute.

“A cheer broke out during our regular lab meeting when we saw the robot successfully walk on the video,” Takeuchi recalled. “Though they might seem like small steps, they are, in fact, giant leaps forward for the biohybrid robots.”

The muscle tissue can drive the two-legged biohybrid robot to walk forward upon electricity stimulation. Credit: Matter/Kinjo et al.

By repeatedly zapping the right leg with electricity while leaving the left leg untouched, the researchers were also able to force their robot to pivot around its left foot as an anchor point. Following the same routine of providing an electric shock every 5 seconds, the robot was able to complete a 90-degree turn in just over a minute.

This might seem slow, but the researchers are confident that their biohybrid robot design is  capable of far higher speeds

“Currently, we are manually moving a pair of electrodes to apply an electric field individually to the legs, which takes time,” explained Takeuchi. “In the future, by integrating the electrodes into the robot, we expect to increase the speed more efficiently.”

There are a few other limitations that the researchers note in their paper that they are also looking to address. For instance, the cultural skeletal muscle tissue that they use to drive the robot loses its power when dried out, meaning that the current design can only work inside a wet culture medium. Integrating a nutrient system to sustain the living tissues or encasing them fully in some kind of collagen structure or lab-grown skin could help to combat this and make the robot more versatile, they suggest.

Once these operational issues can be worked out, the team plans to upgrade their robot design with additional joints and thicker muscle tissues that could make it even more sophisticated and powerful.

Reference: Kinjo R, Morimoto Y, Jo B, Takeuchi S. Biohybrid bipedal robot powered by skeletal muscle tissue. Matter. doi: 10.1016/j.matt.2023.12.035

This article is a rework of a press release issued by Cell Press. Material has been edited for length and content.