The field of biohybrid robotics is in its nascent stage. Early work to develop living tissue within robots has been wrought with challenges, such as how much force muscles created for robots can exert, as well as the amount of time before the tissue starts to shrink and loses function.
The University of Tokyo Institute of Industrial Science has overcome these problems by developing a method that progresses from individual muscle precursor cells to muscle-cell-filled sheets and finally into fully functional skeletal muscle tissue. The method creates muscles in biohybrid robots that function as antagonistic pairs, mimicking those in the body to achieve robot movement and continued muscle function for over a week.
Researchers first constructed a robot skeleton consisting of a rotatable joint, anchors where the muscles could attach and electrodes to provide the stimulus to induce muscle contraction. For the living muscle part of the robot, rather than extract and use a muscle that had fully formed in the body, the team built one from scratch. They did this using hydrogel sheets containing muscle precursor cells called myoblasts, holes to attach these sheets to the robot skeleton anchors and stripes to encourage the muscle fibers to form in an aligned manner.
"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," said Shoji Takeuchi, researcher at the University of Tokyo Institute. "The fact that they were exerting opposing forces on each other stopped them shrinking and deteriorating, like in previous studies."
The team tested the robot in different applications such as having it pick up and place a ring and having two robots work in unison to pick up a square frame. The results showed that 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 about 90 degrees.
"Our findings show that, using this antagonistic arrangement of muscles, these robots can mimic the actions of a human finger," said Yuya Morimoto, lead researcher from University of Tokyo Institute. "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."
