A robot hand powered by lab-grown muscles is challenging you to a game of Rock, Paper, Scissors – do you accept? Here’s hoping you choose rock, because a new remarkable biohybrid has just perfected the scissors sign thanks to multiple muscle tissue actuators (MuMuTAs) that are bringing us closer to larger biohybrid limbs (and in case the above scenario actually happens, you might like to know there’s a way to win Rock, Paper, Scissors).

The hand is huge by biohybrid robotics’ standards, measuring 18 centimeters (7 inches) in length while most other devices have been closer to 1 centimeter (0.4 inches). It’s made up of an articulated plastic base created with a 3D printer. This is able to move thanks to tendon-like structures made of human muscle tissue, which its creators liken to sushi rolls.

“Our key achievement was developing the MuMuTAs,” explained study co-author Professor Shoji Takeuchi from the University of Tokyo in a statement. “These are thin strands of muscle tissue grown in a culture medium and then rolled up into a bundle like a sushi roll to make each tendon. Creating the MuMuTAs enabled us to overcome our biggest challenge, which was to ensure enough contractile force and length in the muscles to drive the hand’s large structure.”

Making the scissor sign like this marks a big step up in the capabilities of biohybrid robots compared to previous devices. It brings us closer to creating prostheses that can mimic human movement realistically and appear more lifelike. The biohybrid robot arm has yet to be deployed outside of a lab environment, but its unique MuMuTA design marks a new direction in biohybrid prosthetics.

Beyond replacing lost limbs with something more functional, it’s possible that the future of biohybrid technology could lead to improved drug testing on muscle tissue, and perhaps even bring us closer to creating entire biohybrid robotic lifeforms.

“A major goal of biohybrid robotics is to mimic biological systems, which necessitates scaling up their size,” said Takeuchi. “Our development of the MuMuTAs is an important milestone for achieving this.”

“The field of biohybrid robotics is still in its infancy, with many foundational challenges to overcome. Once these basic hurdles are addressed, this technology could be used in advanced prosthetics, and could also serve as a tool for understanding how muscle tissues function in biological systems, to test surgical procedures or drugs targeting muscle tissues.” 

The study is published in (and on the cover of) the journal Science Robotics.