Light sensor to help warn of sunburn

Tiny fingertip sensor that can be attached to clothing with the ability to change color to signal the time of safe exposure to the sun.

Too much sun exposure has many harmful effects, and over the years, scientists have come up with some interesting technological solutions that warn users when to seek shade. The team of experts at Northeastern University (USA) added a new solution stemming from an accidental discovery related to how ink changes color, New Atlas on February 25 reported. The study was published in the journal ACS Sensors.

The UV sensor consists of 5 layers of plastic and a sheet of light-sensitive paper. (Photo: Alyssa Stone/Northeastern University)

Initially, the team of experts at Northeastern University studied how sea creatures with tentacles like squid can easily blend in with their surroundings. In the study, they identified a range of pigments, chemical reactions and mechanisms that facilitate this method of camouflage, one of which is remarkable.

Named xanthomatin, this small molecule gives the ink its clear color. The team of scientists demonstrated that it was possible to manipulate xanthomatin to achieve color change. They continue to work on how to apply it to clothing or other consumer products.

When xanthomatin was placed on a laboratory table under bright light to test its stability in everyday environments, the scientists were disappointed to find that it could not help but change color. "When we see it change color under the light, we get really upset," said Leila Deravi, an associate professor of chemistry and biochemistry at Northeastern University.

However, some members of Deravi's team have studied microfluidics from paper and wondered about using the molecule's newly discovered light sensitivity as the basis for a type of sensor. new ultraviolet (UV). So they built a tiny fingertip device that could be attached to a shirt or swimwear. The device consists of 5 thin plastic layers and a round sheet of color treated paper and then dried.

The device also incorporates a "push button" that releases the solution from the small reservoir on the rim. The solution passes through the opaque channels in the resin layer and wets the paper plate. This activates the device and results in the wet paper reacting to UV radiation, turning yellow/orange to red with more exposure to UV light.

The team of experts tested the device and found it to work well in many situations. They adjusted it to how much UV people might be exposed to in different situations, even covering it with sunscreen and making it change color much more slowly.

"I think you're always going to be surprised by how long safe sun exposure is. It really depends on the weather and can be as short as a few minutes," said study author Dan Wilson.

In addition to monitoring sun exposure, the new device could also be used in situations where UV radiation needs to be measured, for example when disinfecting surfaces, the team of scientists say.