Most of the time we print in 3D to produce a prototype for tissue engineering, so this isn’t actually used in the body, but is used as a model to show us how it would work. We are now moving towards using the printers to print parts of the body out of polymers and then applying the patients’ own stem cells to the part so that it essentially becomes alive. We use the patients own cells so that their body recognises it, and doesnt reject it.
Once we have cracked how to print off hearts, livers, kidneys etc that all function correctly, then the waiting list for a transplant would be weeks (the time is takes to grow the patients cells), not months/years like it is now!
Hope this answers your question..if you want to know anything else, just let me know 🙂