Scientists create a smart contact lens that changes colour when exposed to UV light to track sun exposure and tell you when it’s time to apply sunscreen

  • Chemists have developed colour changing dyes that can attach to wearables
  • Colour changes determine levels of ultraviolet exposure, which causes cancer 
  • The dye can be attached to lenses and wristbands or even added to tattoo inks 
  • Scientists also developed an app that analyses colour changes and offers personalised UV protection advice based on skin types of the user 

Smart contact lenses that change colour when exposed to sunlight could help beach-goers better determine when to seek shade or reapply sunscreen.

European researchers have developed minuscule labels containing dyes that change colour when exposed to two types of ultraviolet (UV) radiation from sunlight.

The UV-sensitive labels can be integrated into wearable devices, skin patches, textiles or contact lenses – and the dye could even be added to tattoo inks.

The team says the amount of sun exposure is determined by these dyes with an accuracy of 95 per cent.

A smartphone app with a camera algorithm can then perform analysis of the colour changes to closely monitor UV exposure while taking into account skin types.

Wearable devices with the attached colour-changing dye labels: a) wristband b) textile patch c) transparent skin patch d) sunglasses e) tattoo ink f) contact lens

‘Current protective methods such as sunscreens, UV‐weakening or UV‐impermeable clothing offers sufficient protection against UV‐radiation,’ the researchers write in Advanced Optical Materials.

‘However, these approaches do not provide any information about the UV‐radiation threshold that damages the epidermis.’

Exposure to sunlight for long periods can lead to health problems including sunburn, premature skin ageing, as well as skin cancer, caused by UV light.

Commercial sun screens provide adequate protection from ultraviolet radiation, but an inability to determine exposure to UV light means we can be haphazard in our approach to applying sunscreen. 

Ultraviolet rays, which are primarily responsible for skin damage, are made up of waves that are shorter than that of visible light.

UV radiation is present in sunlight, and constitutes about 10 per cent of the total electromagnetic radiation output from the sun.


UV radiation is part of the natural energy produced by the sun.

On the electromagnetic spectrum, UV light has shorter wavelengths than visible light, so your eyes can’t see UV, but your skin can feel it.

Two types of UV light are proven to contribute to the risk for skin cancer:

Ultraviolet A (UVA) has a longer wavelength, and is associated with skin ageing.

Ultraviolet B (UVB) has a shorter wavelength and is associated with skin burning.

Unprotected exposure to UVA and UVB damages the DNA in skin cells, producing genetic defects, or mutations, that can lead to skin cancer.

These rays can also cause eye damage, including cataracts and eyelid cancers. 

Tanning beds also emit UV radiation. 

Source: The Skin Cancer Foundation 

UV rays can be divided into three sub categories of slightly different wavelengths – UVA (315 to 400 nanometre wavelength), UVB (280 to 315nm) and UVC (100 to 280nm).

While UVC is completely absorbed by the Earth’s ozone layer, UVA and UVB filter through and are proven contributors to skin cancer in humans.

Therefore, the research team, led by researchers at the Technical University of Munich, focused on developing dyes that would focuses on UVA and UVB radiation doses.

They used a combination of UV‐sensitive oxidant and indicator dyes that can be attached to the wearables.

Upon exposure to UV radiation, a photosensitive agent in the dye triggers a chemical reaction that causes a colour change.

The team tested a variety of dye samples, which either went from white to blue or purple, yellow to green and yellow to pink under UV radiation.

The extent of the colour change varies depending on different intensities and duration change, providing a visual colour chart of UV exposure and duration.

These dyes were then inserted into skin patches, textiles, wristbands, contact lenses and tattoo inks and ran without any electronic components to monitor the wearer’s received UV radiation.

When the dyes are applied to contact lenses or sunglasses, the user would be able to sense a colour change in his or her visual field when a UV light exposure threshold is exceeded.

Display menus of the associated ‘UV Guardian’ app which provides personalised recommendations regarding UV protection based on skin types and uses a camera algorithm to analyse changes in the dye label from a smartphone photo

The researchers also outlined a concept for a smartphone app that provides a more in-depth evaluation of the colour change of the UV dye labels.

A camera algorithm in the app is coded to automatically perform the colour analysis and covert data into UV dose values.

The home screen of the app also includes recommended protection methods based on skin type and history of performed scans.

Skin types can also determine the user’s threshold for UV radiation damage, offering a more personalised skin protection option.  

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