Color-changing smart material sensor to alert user to get out of sun

According to the American Cancer Society approximately 5.4 million basal and squamous cell skin cancers are diagnosed each year. Yet, the sun does contribute to the production of Vitamin D, which is necessary for bone health, and perhaps even useful in preventing some cancers. So how does one know how much sun exposure is enough? Now researchers have developed a color-changing wearable that can notify users of their total exposure, allowing them to achieve a balance. A user wears the 0.5″ by 0.5″ millimeter sized flexible patch and is notified of total UV exposure by the change in color. When the sensor turns orange, the user has reached the World Health Organization recommended daily dose of Vitamin D. (Mehr in: Cancer News — ScienceDaily)