Project Summary As one of the most vital organs, the heart functions as a potent biological pump that actively delivers/recycles the blood towards/from all other organs through the vascular system. It has always been a focus in healing an injured or diseased heart through tissue engineering and regenerative medicine. With many years of endeavors, the field of cardiac tissue engineering has seen tremendous progress in fabricating functional cardiac tissues that to a great extent recapitulate the biology of the heart, but challenges remain. The alignment of cardiomyocytes and their organization into bundles characterized by spontaneous and synchronous contraction complicate the development of biologically relevant cardiac tissues. Maturation and contraction of the cardiomyocytes poses another major obstacle. The overall goal of this proposed project is to develop an optoelectronically active bioink that will enable effective maturation and on-demand pacing of the bioprinted cardiac tissues through untethered and remote photo-illumination, in order to address the unmet urgent needs in bioprinting cardiac tissues with embedded, remote stimulation/pacing functions. The bioink will allow for electrical conversion of photoenergy through integration of μ-solar cells in the form of ultra-thin pellets for in situ photo induced electrical stimulation, where the pellets will also be designed to be biodegradable to match the rate of tissue maturation.