Anthony Atala, director of Wake Forest University’s Institute for Regenerative Medicine, is developing techniques to 3D print human organs for transplant using an individual’s own cells as the “ink.” That way, the transplanted organ won’t trigger the patient’s immune system to reject it as a foreign body. From National Geographic:
(For example,) to create an ear, the printer lays down a pliable, porous scaffold made of hydrogel, a kind of polymer. The scaffold is covered with skin cells and cartilage cells, which grow and fill in the ear-shaped form. The hydrogel eventually biodegrades; after about six months the ear is composed entirely of human cells.