The tissues of the heart are mechanically tough and electrically conductive, and they keep a strong, rhythmic beat—properties that are tough to mimic in the lab. But a new hybrid material that combines cell-friendly gel, strong, conductive carbon nanotubes, and living cardiac cells mimics natural heart tissue more successfully than previous attempts. Eventually the new material could be useful in both medical and robotic applications.

The bionic tissues, made by Ali Khademhosseini, a professor at the Harvard-MIT Division of Health Sciences and Technology in Cambridge, Massachusetts, could serve as muscles for biological machines—moving, programmable living tissues that take synthetic biology beyond single cells.