Living Muscles Integrated into Robotic Skeleton

Everyone who saw Terminator 2 remembers the famous scene where Arnold Schwarzenegger’s android character pulls back the skin and muscle on his hand to reveal the machine beneath. That fusion of living tissue and robotics is one step closer to being a reality thanks to the work of engineers at the University of Tokyo’s Institute of Industrial Science.

A significant obstacle to the successful integration of living muscle into machines has been the force those muscles can exert and how quickly they start to atrophy. The researchers may have overcome these problems by developing a new method that incorporates muscle tissues into a biohybrid skeleton as antagonistic pairs—mimicking the way muscles in our own bodies work. The result: remarkable robot movement and continued muscle function for over a week.

The team first constructed a robot skeleton on which to install the pair of muscles. The skeleton had a rotatable joint, anchors to attach the muscles to and electrodes to induce muscle activity through small electrical charges—the same way physiotherapists stimulate muscle recovery in a patient after knee surgery.

Instead of using existing muscles that had already formed in a living body, the researchers built them from scratch. They used hydrogel sheets containing cells called myoblasts, which are the precursor cells that form muscle tissue. The sheets contained holes to attach them to the robot skeleton anchors, and stripes to encourage the muscle fibers to align to the way our own muscles align.

The team tested the robots in different scenarios, including tasks such as picking up and placing a ring, and having two robots work together to pick up a square frame. The robots proved they could perform these tasks well with activation of the muscles to flex a “finger” by around 90 degrees.

“Our findings show that, using this antagonistic arrangement of muscles, these robots can mimic the actions of a human finger,” said lead author Yuya Morimoto. “If we can combine more of these muscles into a single device, we should be able to reproduce the complex muscular interplay that allow hands, arms and other parts of the body to function.”

The team’s findings were published in Science Robotics.

While the lifelike cyborgs of science fiction movies are still a long way off, this development marks an important development in the synthesis of muscle and machine.