Wristband that tells you when you’ve had enough sun

With 100,000 cases of skin cancer resulting from overexposure to ultraviolet light in Britain every year, the dangers of too much sun are well known. Dr David Hazafy, a scientist at Queen’s University Belfast, believes there is another problem: those afraid of getting skin cancer do not venture outside and deprive themselves of the vitamin D their body needs, reports The Guardian.

His solution is a simple and cheap piece of plastic which can be tied around the wrist and contains an ink which disappears when the user has been exposed to the recommended daily dose of sun for their skin tone.

“It is for people who care about the potential dangers but still want to have some fun – mothers, parents for their children or for themselves, older people, people who want to know when it is still safe,” Hazafy says.

The wristband can also be used with sunscreens to mimic the reaction of the skin to sunlight, allowing parents to see how long their children should stay outside during the day, says Hazafy, who works at the school of chemistry and chemical engineering at Queen’s.

“The sunshine gets the negative press. People are quite scared of getting skin cancer so they don’t go out at all. They cover themselves and then there is a problem with vitamin D deficiencies. You need a little bit of sunshine to create vitamin D. If you don’t go out at all because you think the sun is dangerous, you don’t get it” he says.

While sunshine is mostly made up of UV A rays, UV B rays are responsible for 80% of skin cancer cases, and this is what the technology focuses on.

The ink on the plastic wristband is made up of dye and a photocatalyst, a substance which harvests energy from sunlight to cause chemical reactions. When the photocatalyst absorbs UV light, the energy drives a change in the dye: so as the sunlight is absorbed, the colour slowly disappears. When it disappears completely, the maximum amount of UV B light for the day has been absorbed and the wearer knows that they should withdraw from the sun.

If sunscreen is added to the plastic, it will again mimic how sunscreen acts when it is added to the skin, prolonging the amount of time that the user can be exposed.

As different skin types can take varying amounts of sun, the ink can be altered so that it changes at different rates,says Hazafy. When the product comes to market, there will likely be three different formulations for varying skin types which will allow most people use the bands, he says.

Dermatologists “calculate the times, how much UV light you can take without getting sunburnt and that is what the colour change tells you”, he says.

Behind the company set up to commercialise the product, SunCatalyst Laboratories, is Hazafy and Prof Andrew Mills, also from the school of chemistry and chemical engineering at Queen’s University.

What the final product will look like has not yet been decided. As the dye is not destroyed when it is exposed to sunlight, it can ‘recharge’ or return to its original form overnight. This could result in the technology either being on a permanent band, such as those used by charities, or on a piece of biodegradable plastic which could then be thrown away, says Hazafy. It can be waterproofed by sandwiching the plastic with another plastic, he says.

The product itself is “very inexpensive” to make and could retail for between £5 and £10 for a package of disposal bands which would last for a two week holiday or be sold with sunscreen, he says. It will also be possible to print with the ink so that messages can come up on the wristband when the maximum exposure is met, says Hazafy, who aims to have it on the shelves for summer 2016. The NHS says that there are over 100,000 new cases of non-melanoma skin cancer – cancers in the upper layer of the skin which are caused by overexposure to UV light – in the UK every year.