Japanese scientists develop Terminator-like hand with lab-grown tissue

By Dean Murray

A Terminator-like hand that uses lab-grown muscle tissue and robotics to move has been developed.

Researchers say the creepy innovation is a major development towards building larger biohybrid limbs, like Arnold Schwarzenegger's sci-fi character had.

The hand, which can move objects and do a scissor gesture, has been built by a team at the University of Tokyo and Waseda University in Japan.

The researchers used thin strings of lab-grown muscle tissue bundled into "sushi-like rolls" to give the fingers enough strength to contract.

The multiple muscle tissue actuators (MuMuTAs), created by the researchers, are currently limited to the lab environment but have the potential to advance future biohybrid prosthetics, aid drug testing on muscle tissue and broaden the potential of biohybrid robotics to mimic real-life forms.

The University of Tokyo said: "'Rock, paper, scissors' is a classic schoolyard game or quick-fire way to make decisions for the indecisive. But choose paper and you are going to lose to this robot hand, which has mastered the art of the scissor gesture.

"And while it might seem like a simple motion, in the realm of biohybrids and prosthetic limbs, this is a leap forward towards new levels of realism and usability."

The hand is made of a 3D-printed plastic base, with tendons of human muscle tissue that move the fingers. Until now, biohybrid devices have typically been on a much smaller scale - about 1 centimeter long - or limited to simpler or single-joint movements.

By contrast, the biohybrid hand is 18cm in length and has multiple fingers, which can be moved individually to make gestures or in combination to manipulate objects.

“Our key achievement was developing the MuMuTAs. 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,” explained Professor Shoji Takeuchi from the University of Tokyo. “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.”

The MuMuTAs are stimulated using electrical currents, delivered through waterproof cables. To test the abilities of the hand, the team manipulated the fingers to form a scissor gesture by contracting the little finger, ring finger and thumb. They also used their fingers to grasp and move the tip of a pipette. This demonstrated the hand’s ability to mimic a range of actions, as the multijointed fingers can be flexed either separately or at the same time, an impressive feat.

Using real muscle tissue does however come with some downsides, say researchers, with signs of muscle exhaustion documented, akin to a human going to the gym.

“While not entirely surprising, it was interesting that the contractile force of the tissues decreased and showed signs of fatigue after 10 minutes of electrical stimulation, yet recovered within just one hour of rest. Observing such a recovery response, similar to that of living tissues, in engineered muscle tissues was a remarkable and fascinating outcome,” said Professor Takeuchi.

Currently, the hand must be suspended in liquid so that the “anchors,” or ties, which connect the muscles to the hand can float without friction, allowing the fingers to move smoothly. However, the team believes that with further development, it will be possible to build a free-moving hand.