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A simple paper sensor with smiling faces and gathered faces drawn in UV-sensitive ink was produced by the researchers to protect us from the sun.
Scientists say that the different expressions appear in sequence as UV exposure increases, providing users with an unsophisticated method to assess when to cover themselves.
The team adds that they have produced different versions of the bracelet for different skin colors – which they feel is important since darker skin can tolerate greater UV exposure beforehand. that damage does occur and that greater exposure is needed to produce vitamin D.
In addition, the sensor can respond to the different levels of the different components of UV radiation: while UVA is supposed to cause aging of the skin and wrinkles, it is mainly UVB that cause sunburn and lead to cancer of the skin. skin.
"We are always concerned about whether we expose ourselves too much to the sun and we could have skin cancer, cataracts, aging or other skin diseases. But if we do not get enough exposure to the sun, we run the risk of having vitamin D deficiency, "said Professor Vipul Bansal, lead author of the RMIT University study in Australia.
Although Bansal noted that weather reports often contain a UV index to determine the strength of UV radiation, it does not tell people if they are at safe exposure levels and are based on clear skin parameters.
In Nature Communications, Bansal and his colleagues describe how they sought to solve the problem by creating a cheap device based on phosphomolybdic acid or PMA. This substance goes from colorless to blue in the presence of lactic acid and UV radiation.
The team then used this mixture of lactic acid and PMA as ink to draw four invisible faces on paper, and used transparent sheets of the type used for overhead projectors to create filters. This allowed the researchers to improve the intensity of the UV radiation reaching the ink so that the faces changed color as the exposure to UV radiation increased from 25% to 50%, then to 75% and finally 100%.
The team found that PMA-based ink had a darker blue color under UVB than UVA during the same period, which means that the higher the proportion of UVB in sunlight, the more the sensor will quickly indicate% UV radiation dose.
By further adjusting the number of filters for each of the four faces, the team was able to adjust the system to produce different sensors to work on six different skin tones.
Bansal said that if the devices were designed using UV light in the laboratory, they are currently being tested under outdoor conditions. The team hopes that the sensors will be on the market a year from now, which costs about 1 AUD (55 pence) per piece.
Matthew Gass, of the British Association of Dermatologists, who did not participate in the research, said the product "has the potential to be another tool to avoid excessive exposure to the sun, but to replace the real sun protection. form of sunscreen, protective clothing and use of shade ".
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