Smart Tattoos of Intradermally Implanted Photochromic Nanosensors for Personal UV Sensing and Dosimetry

Abstract Monitoring personal ultraviolet (UV) exposure facilitates risk mitigation against UV‐induced skin aging and skin cancer, the most common malignancy in North America, Europe, and Australia. UV radiometers convey real‐time information on local UV irradiance, while UV dosimeters count accumulated UV exposure over time. These devices can help users manage exposure levels in order to reach a healthy daily dose of UV light required for vitamin D production without exceeding erythemal limits that would increase skin cancer risk. However, personal UV detectors still suffer from several limitations. Wearable electronic UV sensors are relatively bulky, heavy, and expensive, while the more commonly used on‐skin disposable colorimetric UV sensors suffer from short service life, skin discomfort, and high accumulated costs when used daily as recommended. Intradermal colorimetric UV nanosensors can overcome these limitations, offering long‐term, comfortable, and inexpensive naked‐eye colorimetric indication of intradermal UV irradiance. Now, a new generation of UV‐sensing intradermal pigments with an improved design offers better tunability, stability, and biocompatibility. These UV‐photochromic nanosensors may be operated as UV dosimeters or simple sunscreen efficacy monitors, depending on the formulation, and can remain functional and re‐usable in the dermis for years.