An ear, unsurprisingly, is difficult to make from scratch. Ear cartilage is uniquely flexible and strong and has been impossible for scientists to reproduce with synthetic prostheses.
If a child is born without one, doctors typically carve a replacement ear out of rib cartilage, but it lacks the wonderfully firm yet springy qualities of the original ear. And it often doesn't look so good.
So why not print one?
Print-out ears may be one step closer to reality, now that scientists are figuring out how to tweak 3-D printers to craft customized ear cartilage out of living cells. Though the printable ear hasn't been used in humans, the goal is to make these ears reliable enough to be used for children born with deformed ears, and adults who lose them from injuries.
"The ear is really remarkable from a mechanical perspective," says Lawrence Bonassar, an associate professor of biomedical engineering at Cornell University who has been working with a group to develop a better replacement ear.
To make the ear, Bonassar and his colleagues scanned the ears of his twin daughters, who were 5 at the time. They used a 3-D printer to build a plastic mold based on the scan. Those printers, similar to a home inkjet, lately have also been adapted to build chocolate, guns, and even kidneys.
They then injected a soup of collagen, living cartilage cells, and culture medium. The soup congeals "like Jell-O," Bonassar tells Shots. "All this happens quickly. You inject the mold, and in 15 minutes you have an ear ready to go."
Well, not exactly. What they have is an ear-shaped chunk of cells that would have to be tucked under the skin on the side of the head by a plastic surgeon before it could become an ear.
To test whether their ear-mold would become living, useful ear cartilage, the researchers implanted samples under the skin on the back of laboratory rats. In three months, cartilage cells took over the collagen, making for a solid-yet-flexible chunk of cartilage that retained its precise shape and size. The results were published online in the journal PLoS One.
This insta-ear would have to be tested in larger animals before it's used in humans, Bonassar says. "We're still identifying what the perfect cell source is for these implants," he says. Candidates include human ear cartilage or stem cells from a person's bone marrow or fat.
Growing ears and other body parts this way has been the focus of speculation and experimentation for years, and not just by Bonassar's lab. Use in humans has always been "years away." Is that still true?
"Years away? I think we are," Bonassar says. "But not too many. With any luck, five years, not 10 or 20."