The screen on the largest version of the Apple Watch will probably measure somewhere around 1.6 inches. The Moto360, likewise, gives us 1.5 inches to swipe, tap and zoom on its rounded screen. This is just big enough for our fingers to clumsily navigate around apps, but just small enough to make it a pain in the ass to do so. It’s clear that smartwatches have a problem: They want to do it all, but don’t have enough real estate to make it a truly pleasant experience.

Apple solved for this with a digital crown that allows users to click and zoom into content. Google is betting simple buttons and a stackable UI will do the trick. But what we really need is a bigger screen, a larger watch that would allow us the richness of interaction we’re looking for. You might think a bigger screen would undermine the very existence of a smartwatch, but researchers from Carnegie Mellon disagree. You just have to get a little creative.

“How you make a watch bigger without actually making it bigger?” asks Gierad Laput, a PhD student at Carnegie Mellon in the Future Interfaces Group. His answer? Turn your arm into an extension of the watch. In a recently-published paper, Laput and his team explore projecting interactive buttons onto skin as a way to extend a smartwatch’s display.

To build the “Skin Buttons,” the team embedded a watch with four laser diodes. These laser diodes are covered with a static piece of film that projects fixed icons onto the skin. Using infrared proximity sensors, the watch is able to tell when the user touches an icon; that information is communicated to the watch and the device reacts as though you touched the screen directly.

Laput and his team developed a few straightforward uses for the buttons, which you can see in the video. For example, you can open an email or music application by tapping an icon on your wrist. You can navigate through apps, using the skin buttons as arrows to scroll up down and over. Another use shows the buttons as an extension of tiny on-screen labels, which Laput says will alleviate space constraints, leaving more room for the actual application.

We first wrote about the Future Interfaces Group earlier this year when it showed off its prototype for a watch that allowed users to twist, pan and click to enable new features (sound familiar, Apple?). That was all about beefing up the input experience to get more out of the touchscreen. Skin Buttons is an extension of that idea, but it’s less about exploring new ways to tell your watch something than it is about exploring how your watch might tell you something. All of this gets more interesting when you think about Skin Buttons as a stepping stone for improving outputs for things like notifications or even a projection of the screen itself.

Planning for a Post-Screen World

Chris Harrison, an assistant professor at Carnegie Mellon and head of the Future Interfaces Group, says it’s only a matter of time before components are small enough and cheap enough that we can use LCDs to create dynamic buttons that change form and color. From there, it’s a matter of improving image fidelity so the projected image is cleaner and easier to see. Once we get to that point, it’s reasonable to question how important screens will be at all. “Maybe in 15 or 20 years you’ll have a device that’s as powerful as a smartphone but has no screen at all,” says Harrison. “Instead it’s like a little box of matches that you plunk down on the table in front of you and now all of a sudden that table it interactive. Or a watch that’s screen-less. You could just snap your fingers and you whole arm becomes interactive.”

We’re still a long way from that day. And for now, Skin Buttons is just a rough prototype. “We’re at generation zero,” says Harrison. But it seems that people are primed for this type of interaction, if only because it’s really not so different than what we’re already used to. “If you put a button on your skin, you expect people to be like, “What the, this is totally insane!” Harrison says. “But actually people don’t generally react like that. People think it’s cool but they get over the coolness really fast and just start using it.”