| Semiconductors & ICs

A Wearable UV Sensor — At Your Fingertips

Creators of a new, M&M-sized wearable device aim to bring UV detection to users’ fingertips – or more precisely, fingernails.

Cosmetics company L'Oréal, in partnership with Northwestern University engineers, developed UV Sense, an 8 mm-sized sensor that can be placed onto clothing, jewelry, and the hand.

The miniaturized wireless platform measures exposure to the sun’s ultraviolet light – a radiation that can cause freckling, sunburn, and dermatological disorders. UV Sense sends warnings of too-much-sun to a wearer’s phone.

The product’s inventors hope that the monitoring technology will lead users to adopt safer behavior patterns, such as seeking shade, and help to prevent skin cancers like melanoma.

How Does UV Sense Work?

UV Sense is, essentially, an ultraviolet LED operating in reverse. Instead of emitting light, however, the LED takes in UV photons, which create a small amount of current that is then captured on a capacitor.

The UV Sense platform shown on a wearer’s thumbnail (Credit: L'Oréal)

After performing an analog-to-digital conversion of the capacitor’s voltage, a Near Field Communication (NFC)-integrated circuit chip wirelessly transmits the data back to the phone, where the voltage is converted quantitatively to a UV-exposure dose measurement.

Simply put: Just before you hit the beach, you mount the bead-sized device on your fingernail. Then, at any point during the day, you swipe the sensor with your phone. The contact activates near-field communications and sends data about your sun exposure to your device.

“In that way you never have to worry about whether a battery is charged up or not, because there is no battery,” said lead researcher John Rogers, a Louis Simpson and Kimberly Querrey Professor of Materials Science and Engineering, Biomedical Engineering, and Neurological Surgery in Northwestern's McCormick School of Engineering. “There are no moving parts. It’s a purely wireless interface with your phone.”

Unlike existing monitors that offer instantaneous measurements, Rogers says the UV Sense technology provides a more valuable, cumulative determination of the total accumulated exposure to ultraviolet rays – an important factor that determines if you’ll get sunburned or not.

“We’re [measuring] continuously, so we don’t have any gaps or errors that could emerge from time-dependent variations in the UV exposure, due to shadows, or moving in and out of a car, for example,” Rogers told Tech Briefs.

A Natural Partnership

With a large market position in sunscreen, L'Oréal had a motivation in developing a technology that places quantitative UV-exposure measurements at their customers’ fingertips.

For years, Northwestern University has developed advanced semiconductor devices that integrate with other parts of the body – even the skin, the brain, or the heart – as an interface.

“We came up with a scheme for doing an accumulation-mode, battery-free dosimetry measurement, and there was a very nice alignment and convergence of interesting capabilities,” said Rogers.

Based on Northwestern University’s development work, L'Oréal put funding in place that allowed the researchers to build the device design. Two years later, the UV Sense technology appeared at last week’s 2018 Consumer Electronics Showcase in Las Vegas, Nevada.

Finding a Place for UV Sensing

Although the waterproof sensor fits on a variety of locations – even a shirt button or sunglasses, for example – the fingernail offers a unique mounting spot. The nail provides a hard, stable platform with no nerve endings or sweat, according to the Northwestern University professor.

“Because the growth rate of the nail is so low, you can actually mount these devices for months at a time,” said Rogers.

Are customers willing to place this kind of sensor on their fingernail? The Northwestern team recognizes the importance of creating an appealing design for customers.

“If you can measure UV accurately but nobody wants to adopt it, then you have a useless technology,” said Rogers.

The UV Sense platform has a graphics overlay on one side, designed for aesthetic appeal, which Rogers considers an important feature for any technology that interfaces with the body.

In collaboration with researchers at the school’s Feinberg School of Medicine, Rogers’ group has received a roughly $2 million grant from the National Institutes of Health to deploy the fingernail UV sensors in human clinical studies. The tests will measure sun exposure in subjects who are at risk for melanoma.

In addition to testing deployment and refining the software interface, the NIH program will also examine the human factors that influence adoption rates.

With a convenient mounting location, cumulative exposure measurement, and helpful warnings, L'Oréal and its Northwestern collaborators aim to protect wearers from the overexposure that leads to cancers like melanoma and other dermatological disorders induced by heavy exposure to the Sun.

“The hope is the user would adopt safer behavior patterns, in terms of exposure,” said Rogers.

UV Sense, as it exists currently, will launch this year, beginning with distribution of the devices to L'Oréal’s global network of dermatologists. A large-scale, consumer-oriented launch will follow in 2019.

What do you think? Would you wear a Fingernail UV Sensor? Share your comments below.