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 of 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 but 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 of which corresponds approximately to the minimum amount of UVI hours capable of causing sunburn in people with different skin tones. The 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, by glancing at the patch, the risk of sunburn for three different skin tones with an accuracy of 73%.
How are the patches made?
Smart patches to monitor sunburn are made with a UV sensitive ink. They can be printed with a normal inkjet printer.
The ink consists of a photoacid generator, a compound that produces acid when exposed to UV light, as well as a skin pH sensitive dye.
"If you are more exposed to UV rays, the patch generates more acid and the dye changes color." The collaborator says so Bichlien Nguyen at Microsoft Research in Seattle.
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 monochromatic design. Hue 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 tips of the hair.
“If you go out and it's a cloudy day, only change the color of the top of your hair,” she says Mariakakis.
Currently hair dye changes color only irreversibly. This is why it is able to indicate the UV intensity only at a given time rather than the cumulative UV exposure for one day, which the patch does.
Furthermore, the hair dye currently only works on lighter colored hair.
Further refinement will produce a future of "beach guys" with multicolored tattoos and multicolored hair.