Researchers create functional 3D-printed ear

Researchers at Princeton University are integrating silver nanoparticles and tissue to create functional ears using off-the-shelf 3D printing equipment.

The technique could replace the conventional medical approach of building synthetic organs through use of polymer scaffolds. That approach, which also uses plastic fibers is moving into the mainstream. Most recently a two-year-old girl received a synthetic windpipe at Children's Hospital of Illinois (Peoria, IL).

The Princeton researchers said that it is difficult to replicate complicated three-dimensional biological structures such as ears with the scaffold technique. The additive manufacturing approach used by 3D printers overcomes that problem because very complex structures are created in incremental tiny layers, usually of plastics.

"In general, there are mechanical and thermal challenges with interfacing electronic materials with biological materials," said Michael McAlpine, an assistant professor of mechanical and aerospace engineering at Princeton who led the project.

"Previously, researchers have suggested some strategies to tailor the electronics so that this merger is less awkward. That typically happens between a 2D sheet of electronics and a surface of the tissue. However, our work suggests a new approach—to build and grow the biology up with the electronics synergistically and in a 3D interwoven format."

The team previously produced a biological sensor and antenna that attaches to the surface of a tooth. The new project is their first effort to make a functional human organ.

"The design and implementation of bionic organs and devices that enhance human capabilities, known as cybernetics, has been an area of increasing scientific interest," the researchers wrote in an article published in the journal Nano Letters. "This field has the potential to generate customized replacement parts for the human body, or even create organs containing capabilities beyond what human biology ordinarily provides."

In the Princeton synthetic ear, electrical signals could be connected to a patient's nerve endings, similar to a hearing aid. Presently, the system receives radio waves, but there are plans to integrate other materials, such as electronic sensors.

Funding came from the Defense Advanced Research Projects Agency, the Air Force Office of Scientific Research, NIH, and the Grand Challenges Program at Princeton University.