In recent years, biomedical engineers have started to learn how to grow replacement body parts from living cells.
Now, Princeton University engineers have pushed the concept further, with a project that evokes the old Bionic Woman TV show.
They created an ear, shaped like a human's, with an antenna woven into the cartilage, which would let the user tune in to radio stations or even a cellphone.
The ear was created with a 3-D printer - an increasingly common device that fashions objects by squirting out layer upon layer of material.
The project was not grafted onto anyone and was more a proof of concept than anything else, said research director Michael McAlpine, an assistant professor of mechanical and aerospace engineering. After all, it is unlikely that someone with a functioning ear would want to replace it just to have electronic capability.
"It seems kind of a little crazy," McAlpine said.
Still, a similar ear, minus the electronics, could be used by plastic surgeons on patients who need reconstructive surgery. And the bionic version gives a hint of what might be possible if we think of the human body as just a starting point, McAlpine said.
Previously, his lab has developed electronic "tattoos" that can be printed on teeth or skin to detect certain bacteria or biomarkers for cancer. He also envisions implanting patients with piezoelectric materials - substances that can convert mechanical to electrical energy. So, for example, you might have a pacemaker that was partly powered by the rise and fall of your diaphragm muscle.
McAlpine and colleagues described their ear this month in the journal Nano Letters. The lead author was Ph.D. student Manu S. Mannoor. Other authors were from Johns Hopkins University and a high school: the Peddie School in Hightstown, N.J.
Ziwen "Jacky" Jiang, a native of Hangzhou, China, is in 11th grade at the private school, which has a special program enabling students to work in university labs. Jiang started working with the Princeton team last summer, designing the ear using computer-aided design software. "He's a very talented kid," McAlpine said.
The ear was printed with a combination of materials. The antenna was made from silicone and silver nanoparticles. The fleshy part of the ear was printed with a mixture of starch molecules and calf cells called chondrocytes. (An ear for an actual person would use cells taken from the patient.)
The cells were kept alive in a growth medium for several weeks. The starchy molecules were just a temporary scaffold. They dissolved and were replaced by collagen and other proteins secreted by the calf cells, giving the tissue a composition similar to animal cartilage.
Though the ear was not attached to a person, the team proved that the antenna worked - testing it with a recording of Beethoven's Für Elise. McAlpine said the electrodes could theoretically be attached to a patient's nerve cells, much like a cochlear implant.
"You and your wife could be sitting next to each other on a couch watching TV, but picking up different signals," McAlpine said.