Photochromic color change—where a product changes color due to UV exposure—isn’t just a novelty as seen in products like color changing t-shirts or cosmetics. A growing number of companies are harnessing the power of photochromic color change to create UV sensor products designed to warn users of excess sun exposure. One such product is UV wristbands; after putting these wristbands on, you apply sunscreen to both yourself and the band. As UV exposure increases with prolonged time in the sun, the wristband turns from a light, nearly translucent color to a deep purple, indicating that you should apply more sunscreen. When the band turns cream color, it acts as a warning to the user to get out of the sun entirely.
At a time when 3.3 million people suffer from some form of skin cancer each year, often related to sun exposure, these innovative UV sensor products offer consumers a new way to protecting their health and wellbeing.1 However, the company’s ability to guarantee correctness of UV indication is critical and the efficacy of these products hinges on thorough testing by manufacturers to ensure that color change is noticeable, easily interpreted, and correctly timed. One of the key ways manufacturers can evaluate the efficacy of their products is by integrating spectrophotometric color measurement within their production process, allowing for deeper insight into color behavior.
Color Changing UV Sensors Protect Users
Some photochromic color changing products, like t-shirts, stickers and even cosmetics, change based on any sun exposure, but don’t offer the consumer a warning of excess sun exposure. While such accessories are undoubtedly fun, they should not be confused with products designed to warn users about dangerous levels of UV exposure.
Any photochromic product designed to be an accurate UV sensor can be used as a warning system, telling the user when to apply more sunscreen or cover up. While some products are being developed to function without sunscreen, most currently work in conjunction with the user’s sunscreen to provide an early warning to apply more product or go inside. 2 To work effectively, these products must be capable of multiple transitions, moving from the original color to the warning color to the final shade based on precise analysis of UV levels. The transition must also be reversible, allowing the product to return to the original color upon sunscreen reapplication. Additionally, they must not be impacted by things like moisture or pH balance, as this could compromise readings, and they must be non-porous to prevent malfunction due to prior sunscreen application.
For many, UV sensors are eye-opening. While it is generally understood that prolonged exposure to the sun on hot, sunny days can be dangerous, many don’t realize that they can passively suffer from sun exposure when they’re not expecting it. This is true even when sunburn may not appear to be an issue, as 80% of the sun’s UV rays are capable of passing through the clouds on an overcast day, contributing to skin damage.3 This is why products that warn a user of excess sun exposure can be game-changing—but only if they’re appropriately sensitive and accurate. By using spectrophotometers, the makers of these products are better able to create effective transitions to warn the wearer when they’ve been in the sun too long.
Using Non-Contact Spectrophotometers for Multi-Stage Color Measurement
The primary goal in the creation of UV sensor products is to make them sensitive enough to monitor UV rays, but not so sensitive that they give false positives of overexposure, and to use color to communicate UV data. Spectrophotometers play a pivotal role in this process, as they are designed to measure color with the highest level of accuracy. This is imperative, as companies who produce these products need to be able to effectively time how much time and how much UV exposure is required to reach a certain color. For example, in the described UV wristband, the spectrophotometer can be used to correlate color change to UV exposure by continuously monitoring the color of the wristband while separately monitoring the UV exposure with a separate sensor.
The testing for color accuracy in UV sensing products should be performed in multiple stages to observe color behavior at critical points of product use, including:
- In its original form, before the application of sunscreen: By testing prior to sunscreen application, the manufacturer can establish the appropriate base color.
- After the application of sunscreen: The color should be tested again after the application of sunscreen and through various levels of UV exposure. In doing so, the manufacturer can ensure that it reacts appropriately to the UV exposure, producing the expected colors correctly.
- After reapplication of sunscreen: After reapplication, color data can be gathered to ensure that the product returns to its original color, already established in step one, resetting the UV sensor.
Choosing the right spectrophotometer is essential to this task. Due to the application of sunscreen, a non-contact spectrophotometer is necessary for accurate color measurement as well as to avoid messy and time-consuming clean ups and potential damage to the spectrophotometer’s sensor. Due to the surface area required for accurate measurement, several wristbands can be stacked together for this measurement process. By using a non-contact instrument, these innovative products can be tested rapidly, safely, and effectively, streamlining the quality control process and ultimately protecting consumer health.
HunterLab has been a leader in color measurement technologies for over 60 years. Today, we offer a complete range of portable, benchtop, and on-line spectrophotometers designed to meet the diverse and exacting needs of our customers. Combined with our sophisticated software packages, HunterLab spectrophotometers give you the highest level of insight into color behavior, helping to ensure that every product you release into the marketplace looks and acts the way you and your customers expect. Contact us to learn more about our renowned instruments and how they can help in the creation of color changing products.
- “Key Statistics for Basal and Squamous Cell Skin Cancers”, https://www.cancer.org/cancer/basal-and-squamous-cell-skin-cancer/about/key-statistics.html ↩
- “Too Much Sun? Color-Changing Sensor Alerts User To Overexposure”, October 4, 2016. https://www.medicaldaily.com/too-much-sun-color-changing-sensor-alerts-user-overexposure-399918 ↩
- “Six Common Sun Myths, Exposed”, July 11, 2012. https://www.cnn.com/2012/07/10/living/guide-to-sun-safety/index.html ↩