Acquiring a superpower usually requires a bite from a radioactive insect, an uncomfortable dose of cosmic radiation, or the discovery of extraterrestrial parentage, but scientist Michael McAlpine hopes to make the process as simple as purchasing aspirin at the pharmacy. So far, he's invented a "tattoo" for teeth that can detect cavities—not exactly the stuff of Hollywood blockbusters—although his latest project, a 3-D printed bionic ear that enables superhuman hearing, could be.

McAlpine earned his Ph.D. in chemistry at Harvard and now is an assistant professor of mechanical and aerospace engineering at Princeton, where he leads a nine-person research group. "I was corrupted to being more of an engineer than a scientist," says McAlpine. "I like to do stuff that's a little more applied."

His first papers in 2003 focused on putting silicon nanowires on flexible substrates. It was an astonishing technical achievement for his time, but unfortunately it came at a point when iPods could only be controlled through a click wheel and Mark Zuckerberg was getting ready for his senior prom. Despite its scientific importance, the market wasn't ready and McAlpine started looking for other research topics, when he asked, "Instead of trying to put nanowires on plastic substrates, why not put them on the body?"

An early example of McAlpine's flexible electronics. Photo: Princeton University

>"I was corrupted to being more of an engineer than a scientist," says McAlpine.

His latest project, a synthetic ear made with a 3-D bioprinter, is a realization of that vision. The complex biomechanical structure was fabricated by depositing live cells and conductive silver in layers. It started as an exploration of material properties, but commercial applications started to appear rapidly. He discovered that cochlear implants, a leading treatment for those with some hearing impairment, are made by hand in a slow and laborious process with costs to match.

But McAlpine's vision is much bigger than simply automating a manual process—he wants to create superhumans. "Repairing lost hearing is an incredibly noble goal," says McAlpine, "but what we made was a coil it receives electromagnetic signals and formed a direct connection with your brain." A phone-brain interface sounds uncanny, but according to McAlpine it's just optimizing the existing process. Tiny hairs in our ears interpret audio signals and transform them into electrical signals that can be decoded by the brain. McAlpine's innovation cuts out the acoustical middle man and pumps the electronic signal right into your medula and brings us one step closer to a world where we can learn kung fu by plugging into a computer.

"We evolved in a world where we needed to hear lions," he says. "But today it makes sense for one of our senses to talk directly to our brain, electrically." It would also give us the ability to hear outside of our normal 20-20,000hz spectrum, giving us the ability to hear what bats or dolphins hear.

Why the ear? "The ear was a great proof of concept for combining the biological and electrical," says McAlpine. "It's one of the simpler organs with no vasculature, it's pure cartilage." McAlpine sees this successful experiment as the first of many upgradeable body parts. "What I'm most excited about is using these 3-D printers, interwoven with advances in material science, and adding biology to them—not just taking the ear to the next level."

Despite his desire to create more superheros than Stan Lee, McAlpine isn't inspired by sci-fi, citing origami and music as bigger influences. "I have to be honest, I was never ever one of those people that watched Star Trek or Star Wars," he says. "I was a musician, I went to the same high school as John Mayer and we'd play at the same venue. He was much better." John Mayer might have sung about your body being a wonderland, but McAlpine is making it a reality.

A decade ago, McAlpine was developing electronics that could function on flexible substrates, but no one saw a commercial application. Today, rumors of smart watches featuring advanced circuits won't stop. Now, he's betting the next big wave of consumer electronics will bring us even closer to our smartphones and tablets. "It will just be considered normal that you have electronics embedded in your body," he says. "You won't think its weird that a door will just open up as you walk towards it. We will become cyborgs and it will be seen as just a normal thing."