Wearable Light Sensors Based on Unique Features of a Natural Biochrome

Overexposure to complete solar radiation (combined ultraviolet, visible, and infrared) is correlated with several harmful biological consequences including hyperpigmentation, skin cancer, eye damage, and immune suppression. With limited effective therapeutic options available for these conditions, significant efforts have been directed toward promoting preventative habits. Recently, wearable solar radiometers have emerged as practical tools for managing personal exposure to sunlight. However, designing simple and inexpensive sensors that can measure energy across multiple spectral regions without incorporating electronic components remains challenging, largely due to inherent spectral limitations of photoresponsive indicators. In this work, we report the design, fabrication, and characterization of wearable radiation sensors that leverage an unexpected feature of a natural biochrome, xanthommatin-its innate sensitivity to both ultraviolet and visible through near-infrared radiation. We found that xanthommatin-based sensors undergo a visible shift from yellow to red in the presence of complete sunlight. This color change is driven by intrinsic photoreduction of the molecule, which we investigated using computational modeling and supplemented by radiation-driven formation of complementary reducing agents. These sensors are responsive to dermatologically relevant doses of erythemally weighted radiation, as well as cumulative doses of high-energy ultraviolet radiation used for germicidal sterilization. We incorporated these miniature sensors into pressure-activated microfluidic systems to illustrate on-demand activation of a wearable and mountable form factor. When taken together, our findings encompass an important advancement toward accessible, quantitative measurements of UVC and complete solar radiation for a variety of use cases.