Today's 3-D printers are great for building plastic stuff, things like toys and musical instruments and even shoes. Some can also print metal objects, like car parts and jewelry and, well, guns. But Jennifer Lewis helped create a new kind of printer, one that can print electronics, such as, ultimately, hearing aids and other wearables. And soon, you'll be able to buy one of these printers from her new company, Voxel8.

Set to make its debut this week at the Consumer Electronics Show in Las Vegas, the Voxel8 printer is the result of several years of work by Lewis and other researchers at Harvard University. It can't print something as complex as a smartphone, but it can print the body of a quadcopter drone—though you'll still need to attach a separate motor and blades—and perhaps more importantly, later models will print hearing aids that fit your particular ear. The hope is that many companies will use it to produce a whole new wave of personalized wearables.

Yes, companies can print custom hearing aids using today, but someone still has to solder the electronics into the plastic moldings. The Voxel8 printer could make this process much faster and cheaper—and it could produce a whole new wave of other wearable electronics that can be personalized in similar ways.

A Material World

Voxel8's goal is to advance 3-D printing beyond the realm of plastic. Lewis argues the industry's focus on plastic has limited the growth of this rather intriguing technology. Yes, recent improvements in mechanical engineering have produced better and cheaper printers, and the software evolved to a point where novice designers can more easily build stuff. But the range of items that can 3-D printed is still limited.

"It's like you can print anything you want, as long as it's made of plastic," she says. "But if you want to take 3-D printing to the next level, we have to have the material sets to do that."

Lewis and her team are steeped in the ways of materials science—a cross-disciplinary field that applies chemistry, physics, engineering and other disciplines to create new materials, ranging from new types of concrete to fibers for clothing to electronics components. And that's what sets Voxel8 apart.

Conductive Ink

Mechanically, the company's printer isn't that different from a MakerBot or one of the dozens of other 3-D printers now on the market. The real breakthrough is the conductive ink the printer uses to print electronic circuits. The ink has a toothpaste-like consistency and unlike something like solder, it can be pushed through a nozzle at room temperature.

Once applied, the ink dries in a few minutes, and it doesn't require post-processing. From the get-go, circuits printed with the ink are ready to use. And you can readily embed these circuits in other objects. The new printer combines traditional 3-D plastic printing techniques with the ability to draw circuits in objects as they're printed.

At Harvard, Lewis and her team have also created inks that can print lithium-ion batteries. And they've developed a process for printing human tissues that could eventually help construct or repair human organs. No, you can't print a kidney with the new Voxel8 printer, but the plan is to commercialize such technology in the future.

Correction 11:00 AM EST: An earlier version of this story stated that the Voxel8 printer could already print custom wearables such as hearing aids. The current version being demoed at CES doesn't have this functionality yet, but it's planned for the future.