Biohybrid robots work by combining biological components such as muscle, plant materials, and even non-biological materials. We are pretty good at making the non-biological parts work, but we have always had problems keeping the organic ingredients alive. This is why machines driven by biological muscles are always rather small and simple, only a few centimeters long, and usually use only a single actuating joint.
“The weak contraction forces of lab-grown muscles, the risk of necrosis of thick muscle tissue, and the challenge of integrating artificial structures into biological actuators made it difficult to expand the expansion of biohybrid robots.” Takeuchi led a research team that created human-like hands in a full-size 18cm biohebrid with all five fingers driven by human muscles grown in the lab.
Keep your muscles alive
Of all obstacles to prevent the construction of large-scale biohybrid robots, necrosis is perhaps the most difficult to overcome. Build muscle in the lab usually means a liquid medium that supplies nutrients and oxygen to muscle cells seeded in Petri dishes. These cultured muscles are small and ideally flat, making nutrients and oxygen from the medium easily reaching any cell in the growing culture.
When you try to make your muscles thicker and therefore stronger, cells buried deep in their thick structures are necrotic as they are cut off from nutrients and oxygen. In organisms, this problem is solved by vascular networks. However, building a vascular network in the muscles grown in the laboratory is something we can’t do very well. Therefore, Takeuchi and his team had to avoid the necrosis issue. Their solution was sushi rolled.
The team began by growing thin, flat muscle fibers arranged side by side in Petri dishes. This allowed all cells to access nutrients and oxygen, making the muscles robust and healthy. Once all the fibers were grown, Takeuchi and his colleagues rolled them into tubes called mumta (multiple muscle tissue actuators), as if they were preparing sushi rolls. “Mumuta was created by incubating thin muscle sheets and rolling them into cylindrical bundles to optimize contractility while maintaining oxygen diffusion,” Takeuchi explains.
