Biohybrid Robots combine biological components such as muscles, plant materials, and even fungi, with non-biological material. We’re pretty good at making non-biological components work, but we’ve had a hard time keeping organic parts alive. This is why machines powered by biological muscles are small and simple, usually only a few centimeters in length and with a single actuating joints.

Professor Shoji Takeuchi of the Tokyo University in Japan says, “Scaling biohybrid robotics has been challenging due to the weak contractile forces of lab-grown muscle, the risk of necrosis of thick muscle tissues, as well as the challenge of integrating artificial structures with biological actuators.” Takeuchi led the research team that created a full-size 18 centimeter biohybrid hand with five fingers powered by lab-grown muscles.

Keep the muscles alive

Necrosis is probably the biggest roadblock that prevents us from building large biohybrid robotic systems. In order to grow muscles in the lab, a liquid medium is used to supply nutrients and air to muscle cells that are seeded onto petri dishes or gel scaffoldings. These cultured muscles are small, flat and ideally shaped. This allows nutrients and oxygen to reach all cells in the growing culture.

When we try and make muscles thicker, and therefore more powerful cells buried deeper within those thicker structures, are cut off from oxygen and nutrients, so they die. The vascular system in living organisms solves this problem. We are still not very good at building artificial vascular network in lab-grown muscle. Takeuchi’s team had to figure out a way around the problem of necrosis. Their solution was sushi-rolling.

The team began by growing thin, flat fibers of muscle arranged side-by-side on a petri plate. The cells were able to access nutrients and oxygen. This resulted in robust, healthy muscles. Takeuchi, his colleagues and the fibers they had grown were then rolled into tubes called MuMuTAs. (multiple tissue actuators), just like preparing sushi. Takeuchi explains that “MuMuTAs are created by culturing muscle sheets and rolling into cylindrical bundles in order to optimize contractility, while maintaining oxygen diffusion.”