Our skin needs to get a certain amount of ultraviolet light to produce vitamin D, but how do we know when we have had too much sun? Wearables that change colour when exposed to UV light could tell us when we should put on sunscreen or seek shade.
Ali Yetisen at the Technical University of Munich in Germany聽and his colleagues created the wearables using liquid dyes that are sensitive to two types of UV radiation.
They used several different dyes that change colour when exposed to UVA and UVB; colour transitions included from yellow to green, and white to pink, blue or yellow.
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They incorporated the dyes into different objects such as a wristband, a patch applied to the skin and small discs incorporated into the edge of sunglasses or contact lenses. By measuring the shift in colour, the wearables give a cumulative measurement of UV exposure throughout a day.
Smartphone app
The team also created a smartphone app to be used with the wristband. A user takes an image of the wearable and the app then quantifies exposure based on the colour of the dye.聽The app allows a person to track their cumulative UV exposure over long periods of time, says Yetisen.
How much UV exposure is safe depends on an individual鈥檚 skin type. For example, because they have lower levels of the skin pigment melanin, which is protective against UV radiation, pale Caucasians have the highest UV sensitivity, able to tolerate relatively little exposure before skin damage occurs.
A user can input their skin type into the app so that their recommended UV thresholds are adjusted accordingly.
The UV-sensitive components of the wearables have to be replaced after use, because the colour change can鈥檛 be reversed, says Yetisen. Some of the UV-sensitive dyes are also toxic, so future work will focus on ensuring that wearables that contain them are safe.
Journal reference: Advanced Optical Materials,
