Sunbathe in moderation

A paper bracelet will tell you when it's time to stop sunbathing

Georgy Golovanov, Hi-tech+

A simple paper bracelet with the image of a smiling or frowning face printed with photosensitive ink will warn the wearer when it's time to finish sunbathing.

Ultraviolet radiation has both beneficial and negative effects on our health. Too much — and you may get sunburn, wrinkles, eye damage and even skin cancer. Too little — and we are in danger of vitamin D deficiency.

Unfortunately, a person cannot independently assess the intensity of ultraviolet radiation. Unlike infrared, it does not feel like heat. To do this, there is an ultraviolet index calculated by the Australian Radiation Protection Agency ARPANSA, but it does not allow you to understand how long you should stay in the sun to get the right dose of vitamin D, and when it's time to go into the shade so as not to earn skin cancer, writes Conversation.

Experts from the Royal Melbourne University of Technology have proposed a simple and inexpensive way: paper bracelets with sensors printed on them that change color depending on the level of ultraviolet radiation.

Inks for them are made with the addition of polyoxometalate molecules, which are able to reproduce colors of different tonality and intensity under the influence of different amounts of ultraviolet light.

The bracelet is equipped with four paper circles with initially invisible emoticons. At first, while the owner receives a safe dose of ultraviolet light, a smile gradually appears on the first mug. Then the second one appears, not so joyful anymore. The third recommends going into the shade, and the fourth — sad — says that it is dangerous to continue sunbathing further.

This technology can be used not only for people, but also in agriculture, to control the shelf life of products affected by ultraviolet radiation. 

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