A viologen-based UV indicator and dosimeter

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.

Electrostatic loading and photoredox-based release of molecular cargo from oligoviologen-crosslinked microparticles

Although on-demand cargo release has been demonstrated in a wide range of microparticle platforms, many existing methods lack specific loading interactions and/or undergo permanent damage to the microparticle to release...

Review of Wearable and Portable Sensors for Monitoring Personal Solar UV Exposure

Sunlight is one of the main environmental resources that keeps all the organisms alive on earth. The ultraviolet (UV) radiation from the sun is essential for vitamin D synthesis in the human body, which is crucial for bone and muscle health. In addition, sun exposure also helps to reduce the risk of some cardiovascular diseases and cancers. However, excessive UV exposure can lead to adverse effects, including some eye diseases, premature aging, sunburn and skin cancers. The solar UV irradiance itself depends on many environmental factors. In fact, the UV index reported in weather forecasts is an estimation under cloudless conditions. Personal UV exposure also depends on one's outdoor activities and habits. Furthermore, the UV intake depends on the skin sensitivity. Therefore, there is a need for research into monitoring the optimal daily UV exposure for health benefits, without developing potential health risks. To facilitate the monitoring of solar UV intensity and cumulative dose, a variety of UV sensors have been developed in the past few decades and many are commercially available. Examples of sensors being marketed are: portable UV dosimeter, wearable UV radiometer, personal UV monitor, and handheld Solarmeter®. Some of the UV sensors can be worn as personal health monitors, which promote solar exposure protection. The paper provides a comprehensive review of the wearable and portable UV sensors for monitoring personal UV exposure, including a discussion of their unique advantages and limitations. Proposals are also presented for possible future research into reliable and practical UV sensors for personal UV exposure monitoring.

Ultrasensitive, Superhigh Signal-to-Noise Ratio, Self-Powered Solar-Blind Photodetector Based on n-Ga2O3/p-CuSCN Core-Shell Microwire Heterojunction

Solar-blind photodetectors have captured intense attention due to their high significance in ultraviolet astronomy and biological detection. However, most of the solar-blind photodetectors have not shown extraordinary advantages in weak light signal detection because the forewarning of low-dose deep-ultraviolet radiation is so important for the human immune system. In this study, a high-performance solar-blind photodetector is constructed based on the n-Ga₂O₃/p-CuSCN core-shell microwire heterojunction by a simple immersion method. In comparison with the single device of the Ga₂O₃ and CuSCN, the heterojunction photodetector demonstrates an enhanced photoelectric performance with an ultralow dark current of 1.03 pA, high photo-to-dark current ratio of 4.14 × 10⁴, and high rejection ratio (R₂₅₄/R₃₆₅) of 1.15 × 10⁴ under a bias of 5 V. Excitingly, the heterostructure photodetector shows high sensitivity to the weak signal (1.5 μW/cm²) of deep ultraviolet and high-resolution detection to the subtle change of signal intensity (1.0 μW/cm²). Under the illumination with 254 nm light at 5 V, the photodetector shows a large responsivity of 13.3 mA/W, superb detectivity of 9.43 × 10¹¹ Jones, and fast response speed with a rise time of 62 ms and decay time of 35 ms. Additionally, the photodetector can work without an external power supply and has specific solar-blind spectrum selectivity as well as excellent stability even through 1 month of storage. Such prominent photodetection, profited by the novel geometric construction and the built-in electric field originating from the p-n heterojunction, meets greatly well the "5S" requirements of the photodetector for practical application.

Iron-based radiochromic systems for UV dosimetry applications

Phototherapy treatment using ultraviolet (UV) A and B light sources has long existed as a treatment option for various skin conditions. Quality control for phototherapy treatment recommended by the British Association of Dermatologists and British Photodermatology Group generally focused on instrumentation-based dosimetry measurements. The purpose of this study was to present an alternative, easily prepared dosimeter system for the measurement of UV dose and as a simple quality assurance technique for phototherapy treatments. Five different UVA-sensitive radiochromic dosimeter formulations were investigated and responded with a measurable and visible optical change both in solution and in gel form. Iron(III) reduction reaction formulations were found to be more sensitive to UVA compared to iron(II) oxidation formulations. One iron(III) reduction formulation was found to be especially promising due to its sensitivity to UVA dose, ease of production, and linear response up to a saturation point.

A wireless smart UV accumulation patch based on conductive polymer and CNT composites

A wearable, highly sensitive, and wireless UV patch was successfully fabricated to record the accumulative UV radiation in terms of resistance.

Brazilian consensus on photoprotection

Brazil is a country of continental dimensions with a large heterogeneity of climates and massive mixing of the population. Almost the entire national territory is located between the Equator and the Tropic of Capricorn, and the Earth axial tilt to the south certainly makes Brazil one of the countries of the world with greater extent of land in proximity to the sun. The Brazilian coastline, where most of its population lives, is more than 8,500 km long. Due to geographic characteristics and cultural trends, Brazilians are among the peoples with the highest annual exposure to the sun. Epidemiological data show a continuing increase in the incidence of non-melanoma and melanoma skin cancers. Photoprotection can be understood as a set of measures aimed at reducing sun exposure and at preventing the development of acute and chronic actinic damage. Due to the peculiarities of Brazilian territory and culture, it would not be advisable to replicate the concepts of photoprotection from other developed countries, places with completely different climates and populations. Thus the Brazilian Society of Dermatology has developed the Brazilian Consensus on Photoprotection, the first official document on photoprotection developed in Brazil for Brazilians, with recommendations on matters involving photoprotection.