Muscle Machines

Robots are getting more intelligent and more useful seemingly by the day. But despite the best efforts of engineers, the capabilities of these robots pale in comparison to the adaptability and efficiency of biological organisms. From the self-healing abilities of our tissues to the intricate neural networks governing our movements, the human body operates seamlessly in a complex dance of biological processes that have not been replicated in artificial systems.

While today’s robots excel in specific tasks within controlled environments, they often struggle to adapt to unforeseen changes or navigate dynamic surroundings with the finesse of a living being. Biological organisms, on the other hand, possess an innate ability to learn and respond to diverse challenges. Furthermore, the energy efficiency of biological organisms has inspired researchers, who are striving to emulate it. But despite the progress in batteries and other technologies, robots still struggle to match the sustained endurance and energy efficiency of living organisms.

The fact of the matter is that the human-like robots of science fiction appear that they will remain fiction for a long time to come. A group of researchers at the University of Tokyo has been hard at work to make them a reality a bit sooner, however. Recognizing that artificial systems are not fully up to snuff yet, they have taken the approach of blending both biological and artificial systems to create controllable robots. It is their hope that this path will ultimately lead to the development of robots with human-like capabilities and energy efficiency.

This is not an entirely new idea — in the past researchers have incorporated biological muscle tissue into robotic systems to serve as actuators. But the movements produced in robots by these past efforts have been somewhat crude, being limited to forward movement or wide turns. Toward the goal of building a more human-like biohybrid, the team has constructed a bipedal, walking robot that is capable of fine and delicate movements.

The initial prototype seems somewhat primitive, but the principles employed could have important ramifications for the development of future systems. The robot utilizes thin strips of lab-grown skeletal muscle tissue to move the legs. The entire robot must remain submerged in water at all times, otherwise this tissue would dry out and lose its ability to move. The legs are made of flexible silicone rubber with 3D-printed feet, and are weighted down to keep them from floating to the surface of the water. The top of the robot consists of a foam buoy that keeps it upright.

In order for the robot to walk, a pair of hand-held gold electrodes must be manually used to deliver a shock to the strips of muscle tissue. By alternately stimulating the muscles attached to each leg, it was demonstrated that the robot could walk forward with a human-like gait. To make turns, even tight turns that have eluded past researchers, a single leg can be stimulated multiple times in succession. The walking speed is not very impressive at 0.002 miles per hour, but it is comparable to other biohybrids.

From its reliance on an aqueous environment to its diminutive size and awkward, external control mechanism, this robot will not be of any use outside of a research lab as it stands today. But the team is currently working on building an updated robot that is made with thicker muscles and a system to supply them with nutrients to keep them healthy on dry land. They are also exploring methods to enable remote control of the robot, and to allow for even finer movements. Should these enhancements materialize, interest in this technology could extend beyond academia.