Flexible UV Exposure Sensor Based on UV Responsive Polymer

One critical challenge facing society is balancing the positive and negative effects of UV exposure. While UV exposure contributes to Vitamin D production, in excess, UV exposure is linked to skin cancer. Therefore, methods to monitor UV exposure and help society achieve this delicate balance have been the focus of numerous research efforts. Here, we leverage advances in functional materials to create a wearable ultraviolet light sensor. The flexible, lightweight trilayer sensor, which is composed of a UV responsive polymer layer sandwiched between two transparent protective layers made from FDA-approved polymers, changes color from transparent to yellow upon UV exposure. Notably, the entire trilayer system is less than 250 μm thick, allowing it to maintain mechanical flexibility. The UV responsive material leverages the photocleavable ortho -nitrobenzyl (ONB) moiety. Because a singular ONB cleaving group is centrally located along the polymer backbone, the colorimetric response is very controlled. Using an AM1.5 solar simulator, the sensor’s linear working range is demonstrated to cover the medically relevant range of 15 min to 1 h. Additionally, we determine the sensor’s robustness to potential environmental and mechanical stress as well as long-term storage. After mechanical bending and water immersion, the performance is unchanged. Storage in ambient conditions also does not degrade the behavior. When combined with sunscreen, the sensor’s response is predictably decreased due to the attenuation of the UV light. This flexible colorimetric sensor based on a smart polymer system can greatly aid society in achieving a balance in sufficient UV exposure.