I remember the days when "cyborg" was a science fiction term and was unlikely to turn up in a serious science paper. Happily, the old folk who attempt to stand between the seas of scientific and popular discussion are failing, and I am proud to present the cyborg ear.

That's right—researchers from Princeton and Johns Hopkins have come together to grow an ear. The hearing, however, is done with electronics, making this the ultimate in human-machine chimera. On the whole, though, it looks kinda gross.

So how do you go about making a fleshy electronic ear? Well, the first step is to get a 3D CAD model of an ear (they got theirs from thingiverse). The researchers then modified the model to include a radio frequency antenna and cochlea-shaped electrodes. The whole ear was then printed using a 3D printer. You can even watch a clip of the printing process.

By itself, that's an entirely artificial ear. But the skeletal 3D structure was seeded with cartilage cells, which, like teenagers, grow like crazy when fed. Ten weeks later, a fully formed ear—I'm using my own very special definition of "fully formed" as you will see later—emerges from the vat, ready to take on the world.

Of course, an ear has to fulfill certain functions. An ear without strength ends up the shape of a cauliflower. The researchers showed that the grown ears were stronger than the printed scaffolding, which tells us that the cartilage is actually forming properly rather than just agglomerating in a mess of cells. Even better, the cells remained alive and viable, which is important: a dead and rotting ear probably only has niche appeal.

The cool thing about cyborgs is that they have abilities beyond that of the native human—similarly, this ear can do things mine can't. For a start, the researchers printed an antenna in the ear that has significant sensitivity to microwaves. This is actually a very impressive achievement, because the entire electronic circuit was printed using polymer gels (the conductive parts were silicone doped with silver nanoparticles), which generally don't cope well with radio frequency currents.

In principle, with a bit of extra electronics, the cochlea implant would allow a human to hear radio, TV, Wi-Fi, microwave ovens, airport radar systems, and various other electromagnetic signals (much like a satellite finder). This sounds kind of cool on one level, but you would really want to be able to turn it off. Imagine trying to go to sleep to the sound of your Wi-Fi arguing with the neighbor's about who gets channel one.

The important thing, though, is that an ear can... hear stuff. This ear, as printed, has no circuitry to convert audio signals into electromagnetic signals, so in that respect it's a failure. But by simply connecting a loop antenna to the stereo port on a computer, the researchers get an audio-frequency electromagnetic signal. Simply put, they needed to implant a microphone, but that can't be printed, so they kept it separate.

They then compared the left and right audio signals of a piece of music as received by two cyborg ears. You can listen to the music here. And yes, that clip is the audio of the electromagnetic signal transmitted by the ear. Of course, we don't know how sensitive the ear is at that frequency range. Given that there are so many other things left to do, however, it isn't worth worrying about at this point.

This is quite a cool technology demonstration. But eww. Why eww? The ear has no skin. Imagine skinning your ear, removing all the blood vessels and nerve cells (and indeed all the tissue except cartilage), and you have the cyborg ear. It's not a pretty sight. You might think that all that's required is some skin, but you would be wrong. The cyborg ears were grown in vats containing all the nutrients required to keep the cells viable. If they had grown a layer of skin on the ear, the inner cells would no longer have access to food and would have died.

To stick the ear on the side of someone's head requires that the body can supply it with nutrients. That means blood vessels. Once the blood vessels are in place, skin will be doable. That only leaves nerves, provided you don't want to accidentally tear your ear off on a cupboard door or something.

Nano Letters, 2013, DOI: 10.1021/nl4007744