Drawing inspiration from human gait, a team of Japanese scientists has designed a two-legged biohybrid robot by combining muscle tissue with artificial materials.
‘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 Shoji Takeuchi of the University of Tokyo. ‘Using muscle as actuators allows us to build a compact robot and achieve efficient, silent movements with a soft touch.’
The research team’s two-legged robot, an innovative bipedal design, builds on the legacy of biohybrid robots that take advantage of living muscles. Muscle tissue has been used to drive biohybrid robots to crawl and swim straight forward and make turns – but not sharp ones. Yet, being able to pivot and make sharp turns is an essential feature for robots to avoid obstacles.
To build a nimbler robot with fine and delicate movements, the researchers designed a biohybrid robot that mimics human gait and operates in water. The robot has a foam buoy top and weighted legs to help it stand straight underwater.
The robot’s skeleton is mainly made from silicone rubber, which can bend and flex to conform to muscle movements. The researchers then attached strips of lab-grown skeletal muscle tissue to the silicone rubber and each leg.
When the researchers zapped the tissue with electricity, the muscle contracted, lifting the leg up. The heel of the leg then landed forward when the electricity dissipated.
By alternating the electric stimulation between the left and right leg every five seconds, the biohybrid robot successfully ‘walked’ at the speed of 5.4 millimetres per minute. To make it turn, the researchers repeatedly zapped the right leg every five seconds while the left leg served as an anchor. After 62 seconds, the robot made a 90° left turn.
‘Currently, we are manually moving 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 expect to increase the speed more efficiently.’
The team also plans to give the robot joints and thicker muscle tissue to enable more sophisticated and powerful movements. But according to Takeuchi, before upgrading the robot with more biological components the team will have to integrate a nutrient supply system to sustain the living tissues and devise structures that will allow the robot to operate in the air.
‘A cheer broke out during our regular lab meeting when we saw the robot successfully walk on the video,’ said Takeuchi. ‘Though they might seem like small steps, they are, in fact, giant leaps forward for the biohybrid robots.’
The research has been published in Matter.