The 3D printing boom has been changing the medical field in recent years. Engineers have discovered ways to print viable organ tissue and mini organs that have the potential to impact drug and surgical testing as well as save lives.

One group of engineers took organ printing a step further and set out to merge electronics and biology by printing a fully operational ear.


The 3D-printed bionic ear capable of recieving radio signals. (Image credit: Frank Wojciechowski)

Researchers at the Princeton University School of Engineering used a 3D printer to create a functional ear that can actually “hear” radio frequencies.  Not only does their printed ear actually work, but it works so much better than a normal human ear that the team calls it a bionic ear.

In the past, research groups have attempted to combine electronics and biology by using a 2D sheet of electronics and a surface of the tissue.

“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, assistant professor of mechanical and aerospace engineering at Princeton and lead researcher of the team.

Last year, McAlpine made some progress involving the use of small-scale medical sensors and antennae when he developed "teeth tattoos” composed of biological sensors and antennae affixed to the surface of a tooth.
McAlpine and his team (which even included a high-school student that mastered CAD designs of bionic ears) were interested in not only replicating an organ, but using embedded electronics to extend the organ’s ability to surpass a human’s.

How it works

Typically, manufacturing tissue involves scattering cells, like those found in ear cartilage, onto a polymer material called a hydrogel. The problem with this method is that it’s difficult to replicate three-dimensional biological structures, so the team decided to use a 3D printer to create the organ.

This is the first time researchers have presented 3D printing as an effective strategy to interweave tissue with electronics.

By using a 3D printer, the team was able to combine antenna electronics with a human ear. They used an ordinary 3D printer to combine hydrogel and calf cells with silver nanoparticles that form an antenna. Then, the calf cells later turned into cartilage.

When the team was done, they had a cartilage structure that included a coiled antenna and two wires that wound around a cochlea and could connect to electrodes. (The cochlea is the part of the ear that senses sound.)

The future of bionic organs

The current ear can receive radio waves, but McAlpine plans to incorporate other materials such as pressure-sensitive electronic sensors to allow the ear to pick up acoustic sounds as well.

Although more work and testing needs to be done before the technology can be used on a patient, one day, the ear could be used to restore and enhance human hearing like an electrical hearing aid.

Replicating tissues and organs with a 3D printer and integrating electronics was a big step. Now, truly bionic organs are closer to becoming a reality. One team member, Manu Manoor, even predicts integrating sensors into a variety of biological tissues so that the stress on a patient’s knee meniscus could be monitored.