Materials and Device Designs for an Epidermal UV Colorimetric Dosimeter with Near Field Communication Capabilities

Ultraviolet (UV) solar radiation is a leading cause of skin disease. Quantitative, continuous knowledge of exposure levels can enhance awareness and lead to improved health outcomes. Devices that offer this type of measurement capability in formats that can seamlessly integrate with the skin are therefore of interest. This paper introduces materials, device designs, and data acquisition methods for a skin-like, or "epidermal," system that combines colorimetric and electronic function for precise dosimetry in the UV-A and UV-B regions of the spectrum, and for determination of instantaneous UV exposure levels and skin temperature. The colorimetric chemistry uses (4-phenoxyphenyl) diphenylsulfonium triflate (PPDPS-TF) with crystal violet lactone (CVL) and Congo red for UV-A and UV-B operation, respectively, when integrated with suitable optical filters. Coatings of poly(ethylene-vinylacetate) (PEVA) protect the functional materials from sunscreen and other contamination. Quantitative information follows from automated L*a*b* color space analysis of digital images of the devices to provide accurate measurements when calibrated against standard nonwearable sensors. Techniques of screen printing and lamination allow aesthetic designs and integration with epidermal near field communication platforms, respectively. The result is a set of attractive technologies for managing UV exposure at a personal level and on targeted regions of the body.