This illustration shows a 3D printed heart ventricle engineered with fiber-infused ink. Credit: Harvard SEAS By Kat J. McAlpine / SEAS Communications Over the last decade, advances in 3D printing have unlocked new possibilities for bioengineers to build heart tissues and structures. Their goals include creating better in vitro platforms for discovering new therapeutics for heart disease, the leading cause of death in the United States, responsible for about one in every five deaths nationally, and using 3D-printed cardiac tissues to evaluate which treatments might work best in individual patients. A more distant aim is to fabricate implantable tissues that can heal or replace faulty or diseased structures inside a patient's heart. In a paper published in Nature Materials, researchers from Harvard John A. Paulson School of Engineering and Applied Sciences (SEAS) and the Wyss Institute for Biologically Inspired Engineering at Harvard University report the development of a new hydrog