The emerging process of 3-D printing , which uses computer-created digital models to create real-world objects , has produced everything from toys to jewelry to food . Soon , however , 3-D printers may be spitting out something far more complex , and controversial : human organs . For years now , medical researchers have been reproducing human cells in laboratories by hand to create blood vessels , urine tubes , skin tissue and other living body parts . But engineering full organs , with their complicated cell structures , is much more difficult . Enter 3-D printers , which because of their precise process can reproduce the vascular systems required to make organs viable . Scientists are already using the machines to print tiny strips of organ tissue . And while printing whole human organs for surgical transplants is still years away , the technology is rapidly developing . `` The mechanical process is n't all that complicated . The tricky part is the materials , which are biological in nature , '' said Mike Titsch , editor-in-chief of 3D Printer World , which covers the industry . `` It is n't like 3-D printing plastic or metal . Plastic does n't die if you leave it sitting on an open-air shelf at room temperature for too long . '' The idea of printing a human kidney or liver in a lab may seem incomprehensible , even creepy . But to many scientists in the field , bioprinting holds great promise . Authentic printed organs could be used for drug or vaccine testing , freeing researchers from less accurate methods such as tests on animals or on synthetic models . Then there 's the hope that 3-D printers could someday produce much-needed organs for transplants . Americans are living longer , and as we get deeper into old age our organs are failing more . Some 18 people die in the United States each day waiting in vain for transplants because of a shortage of donated organs -- a problem that Anthony Atala , director of the Wake Forest Institute for Regenerative Medicine and a pioneer in bioprinting , calls `` a major health crisis . '' An 'exciting new area of medicine ' Bioprinting works like this : Scientists harvest human cells from biopsies or stem cells , then allow them to multiply in a petri dish . The resulting mixture , a sort of biological ink , is fed into a 3-D printer , which is programmed to arrange different cell types , along with other materials , into a precise three-dimensional shape . Doctors hope that when placed in the body , these 3-D-printed cells will integrate with existing tissues . The process already is seeing some success . Last year a 2-year-old girl in Illinois , born without a trachea , received a windpipe built with her own stem cells . The U.S. government has funded a university-led `` body on a chip '' project that prints tissue samples that mimic the functions of the heart , liver , lungs and other organs . The samples are placed on a microchip and connected with a blood substitute to keep the cells alive , allowing doctors to test specific treatments and monitor their effectiveness . `` This is an exciting new area of medicine . It has the potential for being a very important breakthrough , '' said Dr. Jorge Rakela , a gastroenterologist at the Mayo Clinic in Phoenix and a member of the American Liver Foundation 's medical advisory committee . `` Three-D printing allows you to be closer to what is happening in real life , where you have multiple layers of cells , '' he said . With current 2-D models , `` if you grow more than one or two layers , the cells at the bottom suffocate from lack of oxygen . '' To accelerate the development of bioprinted organs , a Virginia foundation that supports regenerative medicine research announced in December it will award a $ 1 million prize for the first organization to print a fully functioning liver . One early contender for the prize is Organovo , a California start-up that has been a leader in bioprinting human body parts for commercial purposes . Using cells from donated tissue or stem cells , Organovo is developing what it hopes will be authentic models of human organs , primarily livers , for drug testing . The company has printed strips of human liver tissue in its labs , although they are still very small : four by four by one millimeter , or about one-fourth the size of a dime . Each strip takes about 45 minutes to print , and it takes another two days for the cells to grow and mature , said Organovo CEO Keith Murphy . The models can then survive for about 40 days . Organovo has also built models of human kidneys , bone , cartilage , muscle , blood vessels and lung tissue , he said . `` Basically what it allows you to do is build tissue the way you assemble something with Legos , '' Murphy said . `` So you can put the right cells in the right places . You ca n't just pour them into a mold . '' Ethical concerns . Not everyone is comfortable with this bold new future of lab-built body parts , however . A research director at Gartner Inc. , the information-technology research and advisory firm , believes 3-D bioprinting is advancing so quickly that it will spark a major ethical debate by 2016 . `` Three-D bioprinting facilities with the ability to print human organs and tissue will advance far faster than general understanding and acceptance of the ramifications of this technology , '' Pete Basiliere said in a recent report . `` These initiatives are well-intentioned , but raise a number of questions that remain unanswered , '' Basiliere added . `` What happens when complex 'enhanced ' organs involving nonhuman cells are made ? Who will control the ability to produce them ? Who will ensure the quality of the resulting organs ? '' Bioprinted organs are also likely to be expensive , which could put them out of reach of all but the wealthiest patients . Murphy said Organovo only uses human cells in creating tissues , and does n't see any ethical problems with what his company is doing . `` People used to worry about doing research on cadavers ... and that dissipated very quickly , '' he said . `` We do n't think there 's any controversy if you 're producing good data and helping people with health conditions . '' Most experts , including Wake Forest 's Atala , do n't think we 'll see complex 3-D-printed organs , suitable for transplants , for years if not decades . Instead , they believe the next step will be printing strips of tissue , or patches , that could be used to repair livers and other damaged organs . `` We are very eager to put pieces of tissue to work for surgical transplants , '' said Organovo 's Murphy , who hopes his company will be ready to begin clinical trials within five years . Of course , any use of 3-D-printed tissue in surgical procedures would require approval by the U.S. Food and Drug Administration . That review process could take up to a decade . By then , the notion of a surgeon putting a 3-D-printed kidney into a patient may not seem so bizarre . Then again , this swiftly evolving technology may create new moral conundrums . `` The ethical questions are bound to be the same concerns we have seen in the past . Many major medical breakthroughs have suffered moral resistance , from organ transplants to stem cells , '' said Titsch of 3D Printer World . `` Will only the rich be able to afford it ? Are we playing God ? In the end , saving lives tends to trump all objections . ''
These printers will someday be producing complex -- and controversial -- human organs . Their precise design will create vascular systems required to make organs viable . Doctor : ` ` It has the potential for being a very important breakthrough '' Researcher : This will become a major ethical issue by 2016 .