Biohybrid components: Muscle tissue lets robot legs walk

Japanese researchers have connected muscle tissue grown in the laboratory to artificial legs, stimulated them to move and controlled them. Using electrical impulses, the team led by Shoji Takeuchi from the University of Tokyo made the miniature limbs walk around in a water tank, as reported in a publication in the journal "Matter" on 26 January 2024. The experiments provide clues as to how biological and technical components can be combined to construct more compact and efficient "biohybrid" robots.

First, the scientists grew skeletal muscle cells in a petri dish. They then attached the muscle strands to two flexible silicone legs several centimetres long. When they subjected this construction to targeted electric shocks, the tissue contracted and the pair of legs took tiny steps forwards. The pictures and videos of the experiments are more cute than spectacular - far more impressive images of technically advanced humanoid machines are circulating on the internet. Such high-performance robots can already walk and master other complex movement sequences. But they are nowhere near as versatile as humans. In particular, they do not contain any biological components that can work in a more energy- and space-saving way than mechanical ones. Combining the two could therefore bring decisive progress in the long term, even if the first attempts still look clumsy.

Takeuchi's research group is regarded as one of the leaders in the field of biohybrid robotics and has been making headlines for some time with various systems of this kind, for example back in 2010 with frog cell odour sensors and in 2013 with artificial organs. In June 2022, a publication on cultivated self-healing skin that encased a robotic finger also attracted attention. This evoked associations with the "Terminator" film series with its killer robot made of "living tissue over a metallic endoskeleton".

Biohybrid legs take small steps

The images of the new development from the laboratory in Tokyo, however, show how far away such ideas are from reality. In order for the toy-like legs to twitch, the thin muscle strands have to be electrically stimulated manually for each step. Such an impulse comes from a power cable every five seconds, so that the limbs barely cover more than five millimetres in a minute. They take just as long to make a 90-degree turn. They are suspended in a water tank, as the muscles are dependent on constant rinsing. For thicker and stronger tissue that also functions in the air, an integrated circulatory system would have to bring nutrients into the cells. According to a press release, Takeuchi's team is planning to integrate electrodes into the robot for faster and more targeted stimulation and is also working on the nutrient supply. For the time being, however, research into cybernetic organisms is only making slow, incremental progress.

Spectrum of Science

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