A research collaboration between the University of Tokyo and Waseda University has yielded an exciting innovation: a biohybrid hand that can not only manipulate objects but also mimic the iconic scissor gesture from the game “rock, paper, scissors.” This dynamic hand is crafted from slender strands of muscle tissue cultivated in labs, carefully coiled into shapes resembling sushi rolls.
The innovation, termed multiple muscle tissue actuators (MuMuTAs), marks a notable advance toward the development of larger biohybrid limbs.
While its current applications are limited to the lab, MuMuTAs show great potential for improving future biohybrid prosthetics, aiding muscle tissue drug testing, and expanding the capabilities of biohybrid robotics in emulating living beings.
Advancements in Prosthetic Realism
The seemingly simple act of making a scissor gesture highlights a significant leap in the realism of prosthetic devices.
The hand itself is built on a 3D-printed plastic framework, with finger tendons made from actual human muscle tissue.
Unlike earlier biohybrid models, which typically measured about a centimeter and exhibited basic movements, this new hand stands out at 18 centimeters and features multi-jointed fingers.
These fingers can operate independently or work together to interact with various objects.
At the core of this breakthrough are MuMuTAs.
These thin strands of muscle tissue grow in a specialized culture medium and are bundled together to form a powerful tendon capable of overcoming the limitations previously faced in constructing larger hand designs.
A major challenge in growing dense muscle tissue is preventing necrosis, a condition that causes the center of the muscle to lack nutrients, leading to tissue deterioration.
By combining multiple slender strands into cohesive bundles, the researchers succeeded in developing tendons with the necessary strength to facilitate movement.
Challenges and Innovations
Activation of the MuMuTAs occurs through electrical stimulation delivered by waterproof cables.
To showcase the hand’s capabilities, the researchers demonstrated its ability to form the scissor gesture and even grip and maneuver a pipette tip.
This versatility underlines the hand’s potential to replicate a range of actions, thanks to the independent control of each finger.
However, utilizing real muscle tissue introduces its own set of challenges.
The team noted that after ten minutes of electrical stimulation, the muscles exhibited a decrease in contractile force and signs of fatigue, though they recovered after an hour of resting.
This fatigue pattern mimics that of living tissue, providing critical insights into engineered muscle systems.
Understanding this fatigue and recovery cycle is essential for optimizing bio-hybrid robotics and prosthetic applications.
Moreover, studying these responses can help refine neuromuscular electrical stimulation benefits by improving muscle endurance and performance over time.
Future research aims to enhance tissue durability and efficiency, ensuring longer-lasting functionality in bioengineered systems.
Presently, to achieve smooth finger movements, the hand must remain submerged in liquid, allowing the muscle connections the freedom to float.
The research team is hopeful that continued advancements will lead to a fully articulated version of the hand.
Future Directions
As it stands, one limitation is that the fingers cannot return to a straight position manually; they passively float back to rest.
Introducing elastic materials to help snap the fingers back into place, or adding MuMuTAs on the back of the fingers to create opposite contractions, could enhance movement control.
The researchers emphasize that a key goal in biohybrid robotics is to accurately replicate biological systems, which necessitates scaling up efforts.
The development of MuMuTAs represents an essential milestone in this journey.
Although the field of biohybrid robotics is still in its infancy and grappling with foundational challenges, surmounting these hurdles could lead to significant progress in prosthetic technologies and improve our understanding of muscle function in biological systems.
This includes potential applications for experimental surgical techniques or pharmaceuticals targeting muscle tissue.
Source: ScienceDaily