A thin film device which turns an appropriate shade of pink to alert wearers of sunburn has been developed by University of Strathclyde researchers.
The work could be worn as a wrist band to warn wearers they risk receiving a potentially harmful dose of ultraviolet rays.
A chemical reaction in the indicator is triggered by UV rays, releasing an acid into a dye, and causing it to change colour, reports the journal Chemical Communications.
Professor of chemistry, Andrew Mills, who led the team, describes this combination of a UV-driven reaction with an acid-sensitive dye as "intelligent ink".
"People think of chemical reactions as happening in test tubes. But here you have a reaction in a very thin layer of ink film that produces a colour change," The BBC quoted him, as saying.
Professor Mills said that the highlight of the device is - it can be adjusted to give an instant signal at the point when sun exposure is about to cause damage.
Professor Mills has made a prototype of the film, combining a dye that gradually changes colour from yellow to blue, and a central strip of dye that turns pink.
"This delayed reaction is the novel feature," Professor Mills explained. As soon as the indicator turns pink, he says "you should get out of the sun because if you stay you'll burn".