The World’s Smallest Wearable Is Basically High-Tech Nail Art. It’s Ingenious.

L’Oreal’s UV sensor is a new way to track your time in the sun.

L'Oreal UV Sense
L’Oreal’s UV Sense. L’Oreal

As a fair-skinned person who spends a lot of time outdoors, I’m concerned about sun exposure. Yes, I dose up on sunscreen like it’s a religion, and yes, I try to stay covered or in the shade as much as possible. But still, the freckles keep accumulating, and with them, I worry, the chance for skin cancer.

I could assuage—or confirm—my fears by doing a better job of monitoring my time in the sun’s rays. There are wearable devices for tracking your UV exposure. Netatmo’s June wristband was one of the first, with a wraparound leather band and a UV sensor hidden inside a jewellike centerpiece. Netatmo aimed to make UV monitoring another valued metric to capture in the Fitbit era, but while its wearable was attractive, it was one more gadget people needed to wear and worry about. While it scored positive reviews, it’s unclear how popular it ever became.

Two years later, in 2016, beauty brand L’Oreal entered the space with another solution: a stretchable UV-sensing skin patch developed by the company’s technology incubator. The My UV Patch was an experiment in giving beauty consumers access to their sun-exposure data. A heart-shaped design on the patch changed colors depending on your sun exposure, which could then be analyzed via photograph in its accompanying app. L’Oreal distributed more than 1 million of the patches to consumers for free and was surprised by the level of engagement and effectiveness of the project: 34 percent of users reported wearing sunscreen more often, and 37 percent tried to stay in the shade more frequently.

Now, L’Oreal has a new wearable device for people like me—people concerned with their long-term sun-exposure risks, people at risk for melanoma, and people who want to know if they should be wearing more sunscreen or reapplying more often. But calling it a device is a bit of a stretch. The UV Sense is a circular, nail-sized sticker that’s little more than a UV sensor and an antenna. Unlike most other wearables, it’s completely batteryless; the sensor is powered by near-field communications and only transmits data when you place your phone near the sensor. Developed in partnership with Northwestern University, UV Sense now boasts the title of world’s smallest wearable.

Guive Balooch, the global vice president of L’Oréal’s technology incubator, said that the company wanted to make sure the sensor was comfortable for longtime wear. My UV Patch, L’Oreal’s first tech-centric UV-sensing product, was a disposable: You wore it for up to three days, then threw it away. The UV Sense, by contrast, lasts as long as any other wearable on the market. And besides just being small, it’s notable for its unique form factor. Its tiny size—about as thick as a credit card and lighter than a Tic Tac—makes it ideal as a stick-on nail applique. “We knew that nail art was booming,” Balooch said. “We thought that could be really interesting.” However, it’s not exclusively a nail sticker—it can just as easily be positioned on a pair of sunglasses or on another accessory you typically wear outdoors, such as a watch. On a nail, the sensor lasts for two weeks, then it needs to be readhered. (“The reason is more for the nail than the sensor,” Balooch said. “The nail is a living part of your body. UV gel or nail art normally lasts about two weeks.”)

Making nail art “smart” is an ingenious way to give folks who might not otherwise want a wearable access to the valuable data it can provide. However, it does have some drawbacks. UV Sense’s accompanying app doesn’t appear to give real-time notifications when it’s time to reapply sunscreen—to do that, it would need a more persistent Bluetooth or Wi-Fi connection with your phone, and that would require a battery.

Still, UV Sense provides valuable data in an extremely unobtrusive package. While sensor-based notifications may be a no-go, the app can still offer advice and notifications based on information about your habits and lifestyle as well as information about the day’s temperature and pollen forecasts. And you can always check in on your latest UV exposure stats by bringing your phone and the sensor in close proximity and checking the app. The goal of the sensor is to be a call to action, to help wearers be more aware of the time they spend in the sun, minimize it if necessary, and protect their skin in the meantime. UV Sense is launching as a limited pilot this year and will go on sale worldwide next year for a yet-to-be-determined, sub-$50 price tag.