In April, biologists at the University of Missouri-Columbia printed a 3mm square sheet of chicken heart cells that was just under 0.5mm thick. The team found that four days after the printing, the cells were beating in time with each other.

"It's just amazing. The system self-organises itself into a single structure which beats in synchrony," Gabor Forgacs, the professor leading the research, told the Columbia Daily Tribune.

The breakthrough, revealed as the team received a 2.8m ($5m) grant for the research, follows similar research at Manchester University.

A team there has joined up with Xaar in an attempt to print three dimensional organ tissue, which could be used for skin grafts and organ transplants.