Cometh the cyborg: improved integration of living muscles into robots has arrived

According to a new study published in the Journal of Science Robotics, researchers at The University of Tokyo Institute of Industrial Science have developed a solution to grafting human tissue to robotic musculoskeletal frames.

Within the field of biohybrid robotics—which involves the use of living tissue within robots, rather than just metal and plastic—one significant problem researchers face is the amount of force these newly develop muscles can exert over time before they start to shrink and lose their function.

The team first needed to create a robot skeleton, which they did, complete with a rotatable joint, anchors where the muscles could attach and electrodes to provide the stimulus to induce muscle contraction. From there it was a multi-step process, one of the highlights of the project, starting with individual cells acting as a precursor to the muscle itself, evolving into muscle-cell-filled sheets, and then to fully functioning skeletal muscle tissues.

Rather than extract and use a muscle that had fully formed in the body, the above process allowed them to build muscles from scratch using hydrogel sheets containing muscle precursor cells called myoblasts. From there holes attached these sheets to the robot skeleton anchors, and stripes to encourage the muscle fibres to form in an aligned manner were added on.

“Once we had built the muscles, we successfully used them as antagonistic pairs in the robot, with one contracting and the other expanding, just like in the body,” study corresponding author Shoji Takeuchi says. “The fact that they were exerting opposing forces on each other stopped them shrinking and deteriorating, like in previous studies.”

The team also tested the robots in different applications, including having one pick up and place a ring, and having two robots work in unison to pick up a square frame. The results showed that the robots could perform these tasks well, with activation of the muscles leading to flexing of a finger-like protuberance at the end of the robot by around 90°.

“Our findings show that, using this antagonistic arrangement of muscles, these robots can mimic the actions of a human finger,” lead author Yuya Morimoto says. “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.”

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