How to Print a Beating Heart

Sitting in a culture dish, a layer of chicken heart cells beats in synchrony. But this muscle layer was not sliced from an intact heart, nor even grown laboriously in the lab. Instead, it was printed, using a technology that could be the future of tissue engineering. Droplets of bio-ink — clumps of living cells a few hundred micrometres in diameter — flow together and fuse when squirted close to each other. They can be made to form layers, rings and tubes — which could serve as blood vessels — depending on how they are deposited. Bioprinting could develop into a fast and cheap way to engineer a variety of tissue types