Organ harvesting from Falun Gong practitioners in China must be taken from a living donor (kidneys must be transplanted within 24–48 hours; livers within 12 hours, and hearts within 8 hours). Kirk C. Allison, Associate Director of the Program in Human Rights and Medicine at the University of Minnesota, wrote that the "short time frame of an on-demand system [as in China] requires a large pool of donors pre-typed for blood group and HLA matching," which is consistent with reports of Falun Gong prisoners having blood and tissue tested in custody. He wrote that China's short organ wait times could not be assured on a “random death” basis,
Organ printing are some organ-specific structural elements that must be addressed for successful creation of a transplantable printed organ. The transfer of nutrients and oxygen to cells throughout a printed organ is essential for its function. In very small or thin tissues of less than a millimeter in thickness, cells can receive nutrients through diffusion. However, larger organs require the transportation of nutrients to cells deeper inside the tissue, which requires that the tissue be vascularized, and thus able to receive blood for the exchange of cargo like oxygen and cell wastes. Early organ printing techniques created solid tissues that were unable