Color-changing adhesives and hair dyes that react to ultraviolet light may help people understand when they are at risk of sunburn in the future.
Alex mariakakis from the University of Washington in the United States submitted research made in close contact with a Microsoft team to develop printable stickers with special features. Stickers able to change color, from purple to light pink during the hours of the day.
What do the color differences of this type of adhesive indicate? Nothing more than cumulative exposure to UV light.
To each his own
The patches are suitable for people with different skin tones, who have different minimum UV exposure thresholds for sunburn, he says Mariakakis. There are three versions, each corresponding approximately to the minimum amount of UVI hours capable of causing sunburn in people of different skin tones. UVI time is the reference unit of solar exposure.
For example, people with very pale skin can burn themselves after an exposure time of between 2,22 and 3,33 hours UVI.
After learning how to interpret the reference colors, 35 participants were able to check the risk of sunburn for three different skin tones with 73% accuracy by taking a look at the patch.
How are the patches made?
Smart patches to monitor sunburn they are made with an ink sensitive to UV rays. They can be printed with a regular inkjet printer.
The ink consists of a photoacid generator, a compound that produces acid when exposed to UV light, as well as a dye sensitive to the skin's pH.
“If you are exposed to more UV rays, the patch generates more acid and the dye changes color.” The collaborator says so Bichlien Nguyen at Microsoft Research in Seattle.
Chameleon hair
The team also has formulated a hair dye a base of pigments that change color in the presence of UV light. The hair of those who use it can go, for example, from light to pink.
In one project the team tested a special monochrome design. The tint increases color saturation as UV intensity increases. The team used a layered design that included three dyes, each with different saturations that moved from the top of a person's head to the ends of their hair.
“If you go out and it's a cloudy day, only the top part of your hair changes color,” she says Mariakakis.
Currently hair dye only changes color irreversibly. This is why it is able to indicate the UV intensity only at a given moment rather than the cumulative exposure to UV rays for a day, which the patch does.
Furthermore, the hair dye currently only works on lighter colored hair.
Greater refinement will produce a future of “beach types” with multicolored tattoos and colorful hair.
