Scientists design two-legged robot powered by muscle tissue

Compared to robots, human bodies are flexible, capable of fine movements, and can efficiently convert energy into movement. Inspired by human gait, Japanese researchers have designed a two-legged biohybrid robot by combining muscle tissue and artificial materials. Published on January 26 in the journal Matterthis method allows the robot to walk and rotate.

“Research on biohybrid robots, which are a fusion of biology and mechanics, is recently attracting attention as a new field of robotics with biological functions,” explains corresponding author Shoji Takeuchi of the University from Tokyo, Japan. “Using muscles as actuators allows us to build a compact robot and achieve efficient, quiet movements with a gentle touch.”

The research team’s two-legged robot, an innovative bipedal design, builds on the legacy of biohybrid robots that take advantage of muscles. The muscle tissue caused the biohybrid robots to crawl, swim straight and take turns, but not sharp ones. Still, being able to pivot and make sharp turns is an essential feature for robots to avoid obstacles.

To build a more agile robot with fine, delicate movements, researchers designed a biohybrid robot that mimics human gait and operates in water. The robot has a foam buoy and weighted legs to help it stand upright underwater. The robot’s skeleton is primarily made of silicone rubber that can bend and flex to accommodate muscle movements. The researchers then attached strips of lab-grown skeletal muscle tissue to the silicone rubber and to each leg.

When the researchers hit the muscle tissue with electricity, the muscle contracted, lifting the leg. The heel of the leg then landed forward as the electricity dissipated. By alternating electrical stimulation between the left and right leg every five seconds, the biohybrid robot successfully “walked” at a speed of 5.4 mm/min (0.002 mph).

To turn, the researchers repeatedly zapped the right leg every five seconds while the left leg served as an anchor. The robot made a 90-degree left turn in 62 seconds. The results showed that the muscle-driven bipedal robot can walk, stop, and perform precise rotational movements.

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

The team also plans to give the bipedal robot thicker joints and muscle tissue to enable more sophisticated and powerful movements. But before upgrading the robot with more biological components, Takeuchi says the team will need to integrate a nutrient delivery system to support living tissue and device structures that allow the robot to operate in the air.

“Cheers erupted during our regular lab meeting when we saw the robot successfully walking on the video,” says Takeuchi. “Even though they seem like small steps, they are actually giant leaps for biohybrid robots.”