In a lab dish, hESCs can be placed in a solution that contains the biological cues that tell the cells to develop into specific tissue types, a process called differentiation, writes Tanya Lewis at LiveScience. The process starts with the cells forming what are called "embryoid bodies." Cell printers offer a means of producing embryoid bodies of a defined size and shape.

In this case, the cells were printed onto a dish containing many small wells. The dish was then flipped over so the droplets hung from them, allowing the stem cells to form clumps inside each well. The printer then laid down the cells in precisely sized droplets and in a certain pattern that is optimal for differentiation, leading to great success, Lewis explains:

Source: Dr. Will Shu / Biofabrication. 3D printed human embryonic stem cells

Tests revealed that more than 95 percent of the cells were still alive 24 hours after being printed, suggesting they had not been killed by the printing process. More than 89 percent of the cells were still alive three days later, and also tested positive for a marker of their pluripotency — their potential to develop into different cell types.

Biomedical engineer Utkan Demirci, of Harvard University Medical School and Brigham and Women's Hospital, has done pioneering work in printing cells, and thinks the new study is taking it in an exciting direction. "This technology could be really good for high-throughput drug testing," Demirci told LiveScience. One can build mini-tissues from the bottom up, using a repeatable, reliable method, he said. Building whole organs is the long-term goal, Demirci said, though he cautioned that it "may be quite far from where we are today."

The new printing method could be used to make 3D human tissues for testing new drugs, growing organs and also printing cells directly inside the body, asserts Lewis.

The study was recently published in the journal Biofabrication.