A paper-thin idea for a sunburn sensor

Scientists have developed an inexpensive, disposable, and biodegradable sensor for sun exposure that’s as thin as a sheet of paper—because it is a sheet of paper, according to a report published online in ACS Sensors, a journal of the American Chemical Society.

Despite public health warnings against sun tanning and the dangers of UV overexposure, sunburn is still the main cause of skin cancer, the most common type of cancer. To add insult to injury, a 2016 survey by the American Academy of Dermatology found that less than one third of respondents understood the difference in protection between an SPF 30 sunscreen and an SPF 15 sunscreen.

In light of these warnings and misunderstandings, the scientists behind this investigation reasoned that many sun worshippers, outdoor workers, and others could benefit from an affordable, readily available, and simple-to-use UV sensor.

However, most currently available UV monitors integrate the sensing material into smartphones or other high-technology wearable devices. Although single-use sunburn sensors made of thin film have come onto the market recently, some of these use substances that are potentially harmful to humans or the environment. Others are only good for specific skin tones.

To improve on these devices, scientists at the University of New South Wales in Sydney, Australia, set out to create a disposable sunburn sensor that would be inexpensive, composed entirely of benign materials already approved for human use, and easily calibrated to take into account different skin tones and SPFs of sunscreens applied on the skin.

To do so, they took advantage of the photocatalytic properties of titanium dioxide. On sheet of paper, they combined titanium dioxide and brilliant blue food dye into a single layer, along with polyvinylpyrrolidone (PVP) as a binder to form a film.

When the titanium dioxide is exposed to UV radiation, it discolors the food dye in a progression that they calibrated to match UV exposure time for different skin types. For example, when the color changes for your skin type, it’s time to apply more sunscreen or get out of the sun.

The researchers have not yet announced when their paper sunburn sensor will come to market, or if further refinement of the sensor is still required.