Researchers developed a transparent sensor that reacts to sunlight to allow real-time monitoring of UVA exposure on the skin. Credit: Jnnovation Studio
Researchers have developed a new wearable sensor that can detect ultraviolet A (UVA) rays from the Sun, helping reduce a person’s unprotected exposure to the harmful radiation.
The team behind the device’s creation has demonstrated that it can be connected to a smartphone and offer real-time warnings to people when they are at risk of sunburn.
Previous studies have shown that a person’s risk of developing melanoma increases with the number of sunburns during their lifetime. Currently, melanoma is the third most common cancer in Australia, with 1 person diagnosed every 30 minutes.
Although sunscreen can be used as a protective shield against sunburn, scientists and health professionals believe that UV monitors may also help to lower the number of melanoma cases.
“Effective UV monitoring requires the development of sensors with rapid response, long-term stability, and low power consumption,” write the authors.
The UV radiation released by the Sun can be broken down into 3 types: UVA (wavelengths between 315–400nm), UVB (280–315nm) and UVC (200–280nm).
Earth’s atmosphere entirely blocks UVC and partially filters UVB radiation, which penetrates the superficial layers of skin. UVB is mainly responsible for sunburn and DNA damage which can lead to mutations.
However, the atmosphere does not protect people from UVA which makes up 95% of the UV radiation reaching Earth’s surface. These rays can penetrate deeper into skin, causing long-term damage and increasing the risk of developing skin cancer.
Currently, UVA detectors are opaque with studies demonstrating this limits their performance and accuracy. The team, led by researchers at Soongsil University, Korea, has created a transparent sensor that can monitor UVA rays in real-time with higher accuracy readings.
They first designed a photodetector, which is a device that converts the UV radiation from the sun into an electrical signal, using a multilayer structure with indium tin oxide (ITO) as the electrode.
In contrast to previous UV photodiodes, which used opaque metal electrodes, this made their device transparent.
The full design has been published in Science Advances.
“The ITO-based photodiode not only maintains high optical transparency but also shows enhanced responsivity compared to previously reported fully transparent devices, achieving performance comparable to that of devices with metal electrodes,” write the authors.
“These stable and efficient photoresponse behaviours of the photodiode suggest promising characteristics for high-performance UVA detection applications.”
When the team tested their sensor, they found that around 75% of light in the visible range (380 to 780nm) successfully passed through the ITO-based photodiode.
“Based on these results, a wearable UV monitoring device capable of continuous operation under natural sunlight was developed, demonstrating feasibility for real-time health care applications,” they write.
The team integrated the data from their monitor with a smartphone app.
Users who wore the monitoring device were notified when the sensor detected that they had been exposed to 80% of the minimum amount of UVA exposure that would cause sunburn. This threshold is known as the ‘minimal erythemal dose’ and can vary person to person depending on skin type.
The device could one day be able to provide people with continuous daily monitoring for UVA exposure, to potentially lower the risk of developing skin cancers like melanoma.
“This health care device, integrated with a smartphone, demonstrates its potential as a practical approach to prevent risks associated with prolonged UV exposure,” write the authors.
“The developed device demonstrates a sensitive real-time response to changes in sunlight conditions. This result indicates its potential for effective use in detecting UV exposure and protecting user health in outdoor environments.”