Things your phone probably reminds you of: Your mother's birthday. Your kid's doctor appointment. That thing Beyoncé said on Twitter.
Now, thanks to scientists at Northwestern University's Center on Bio-Integrated Electronics, your phone can also tell you exactly how much sunlight your body has absorbed that day, based on what you're wearing, what the weather is and where you are located on the globe.
This useful info comes courtesy of a tiny sensor developed by researchers John A. Rogers and Dr. Steve Xu that can stick to your skin or clip to your hat. "It's smaller than a dime, thinner than a credit card," Xu said, "and you can stick it or clip it anywhere, which allows people to customize it."
His favorite application is using it as nail art. (Scientists love the fingernail as a vehicle for a wearable device, he said, because it's stable and durable.)
The sensor is so small, Xu said, "I often forget I'm wearing it." Yet, the device packs a lot of power and data-gathering ability: It can accurately measure UVA and UVB radiation, as well as light exposure, runs on solar power without a battery and never needs recharging.
Getting rid of the need to charge not only makes it easier to use, Xu said, "it allows the device to be even smaller, and cheaper to make." It's also virtually indestructible — students dropped it into boiling water and simulated running it through a washing machine but were not able to break it.
The accompanying phone app allows users to enter information about sunscreen applied, clothing and activities (such as whether you're in the water.) "It's really a platform technology," Xu said, "that can measure light extremely accurately in a novel way."
That's important, he said, because sun exposure is the No. 1 contributor to skin cancer.