Researchers at Princeton University have created a 3D-printed bionic ear that can even hear radio frequencies.

The prototype is made of a mix of cellular material, silicone and electronics. Researchers printed the ear with a 3D printer they purchased for $1,000.

"As a proof of concept, we generated a bionic ear via 3D printing of a cell-seeded hydrogel matrix in the precise anatomic geometry of a human ear, along with an intertwined conducting polymer consisting of infused silver nanoparticles," the team said in its abstract.

A 3-D printer works by layering materials on top of each other in thin layers, forming a physical version of a computer model.  To create the ear, scientists put in a hydrogel substance with cartilage cells from a calf, a coiled nano-particle for the receiver and silicone to keep the electronics stable. After the object was printed, they dipped it in a solution to encourage the calf cartilage cells to grow into a human ear shape. This embedded the electronics into the cartilage and silicone.

Currently, the ear can only hear two radio frequencies. However, researchers hope to get it working just like a normal human ear. If they are able to, the receiver could be attached to the head via nerve endings in the ear canal similar to what most hearing aids do.

"In general, there are mechanical and thermal challenges with interfacing electronic materials with biological materials. 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," said Michael McAlpine, an assistant professor of mechanical and aerospace engineering at Princeton and the lead researcher on the project, in a press release.

Researchers hope the bionic ear is just the cusp of what can be done with 3D printing technology. They say they will seek to create other bionic organs through similar processes in the future.