The world’s smallest sensor, battery-free device has been developed by Northwestern Medicine and Northwestern’s McCormick School of Engineering scientists to measure exposure to light across multiple wavelengths, from the ultra violet (UV), to visible and even infrared parts of the solar spectrum. It can record up to three separate wavelengths of light at one time.
The device’s underlying physics and extensions of the platform to a broad array of clinical applications are reported in a study to be published Dec. 5 in Science Translational Medicine. These foundational concepts form the basis of
consumer devices launched in November to alert consumers to their UVA exposure, enabling them to take action to protect their skin from sun damage.
The device was designed by a team of researchers in the group of John Rogers, the Louis Simpson and Kimberly Querrey Professor of Materials Science and Engineering, Biomedical Engineering in the McCormick School of Engineering and a professor of neurological surgery at Northwestern University Feinberg School of Medicine.
It’s also rugged, waterproof and doesn’t need a battery. “There are no switches or interfaces to wear out, and it is completely sealed in a thin layer of transparent plastic,” Rogers said. “It interacts wirelessly with your phone. We think it will last forever.”
How the tiny sensor works
Light passes through a window in the sensor and strikes a millimeter-scale semiconductor photodetector. This device produces a minute electrical current with a magnitude proportional to the intensity of the light. This current passes to an electronic component called a capacitor where the associated charge is captured and stored. A communication chip embedded in the sensor reads the voltage across this capacitor and passes the result digitally and wirelessly to the user’s smartphone. At the same time, it discharges the capacitor, thereby resetting the device.
Multiple detectors and capacitors allow measurements of UVB and UVA exposure separately. The device communicates with the users’ phone to access weather and global UV index information (the amount of light coming through the clouds). By combining this information, the user can infer how much time they have been in the direct sun and out of shade. The user’s phone can then send an alert if they have been in the sun too long and need to duck into the shade.
Credit: The Verge
Commercially collaboration with L’Oreal
The increasing, ubiquitous need for better protection from UV radiation is why there is a consumer version of the sensor, called "My Skin Track UV," that was developed with cosmetics giant L'Oreal.
It launched in November at the Apple store. You can stick it on your kid, or yourself, and get a phone alert that will warn you before soaking up the sun on your winter break vacation crosses the line into sunburn territory.