A Wearable Colorimetric Dosimeter to Monitor Sunlight Exposure

Abstract

The personal ultraviolet (UV) dosimeter is a useful measurement tool to prevent UV induced dermal damages; however, conventional digital dosimeters are either bulky or require external power sources. Here, a wearable, colorimetric UV film dosimeter that provides color transition, from purple to transparent, is reported to indicate the UV dose. The film dosimeter is made of a purple photodegradable dye ((2Z,6Z)‐2,6‐bis(2‐(2,6‐diphenyl‐4H‐thiopyran‐4‐ylidene)ethylidene)cyclohexanone or DTEC) blended in low density polyethylene film. The DTEC film discolored 3.3 times more under the exposure of UV light (302 nm) than visible light (543 nm), and a UV bandpass filter is developed to increase this selectivity to UV light. The DTEC film completely discolors to transparency in 2 h under an AM 1.5 solar simulator, suggesting the potential as an indicator for individuals with types I–VI skin to predict interventions to avoid sunburn. Finally, the DTEC film is integrated with the UV bandpass filter on a wristband to function as a wearable dosimeter for low cost and convenient monitoring of sunlight exposure.

Recent Advances and a Roadmap to Wearable UV Sensor Technologies

“…d) A wearable low‐density polyethylene‐based colorimetric dosimeter employing a degradable purple dye to monitor sunlight exposure. Reproduced with permission 37. Copyright 2018, Wiley‐VCH.…”

“…To this end, a semiconductor‐free wearable colorimetric dosimeter that contained a blend of a purple photodegradable dye ((2Z,6Z)‐2,6‐bis(2‐(2,6‐diphenyl‐4H‐thiopyran‐4‐ylidene)ethylidene)cyclohexanone (DTEC)) into an LDPE film, was reported (Figure 8d). 37 Upon UV exposure, the dye gradually photodegraded from purple to colorless, and the eventuated color could be compared with a calibrated reference bar provided on the sensor to indicate the exposed UV dose. By altering the DTEC/LDPE weight ratios, the color density of the film could also be adjusted, and this ability was claimed to have the potential for customizing the sensor for different skin phototypes.…”

“…This process transforms the material from one photostate to another that has a different absorption spectrum, thus leading to a color change that can be potentially captured by the naked eye. The simplicity of the reaction output allows colorimetric detection mechanism to be integrated with a variety of flexible substrates including paper,13,34 polydimethylsiloxane (PDMS),35 polyethylene naphthalate (PEN),36 low‐density polyethylene (LDPE),37 and silicon films38 offering an intrinsic advantage for a direct and simple means to detect UV radiation. Wearable photochromic UV sensors based on such flexible substrates have begun to attract significant research interest.…”

Recent Progress in Nanomaterial Enabled Chemical Sensors for Wearable Environmental Monitoring Applications

“…[67] Polymeric substrates are the most conventional substrates utilized to fabricate the WCESs due to their flexibility, stretchability, low cost as well as roll to roll producibility. Several polymer films are used in recent WCESs including polyethylene terephthalate (PET), [23,[68][69][70][71][72][73][74][75][76][77][78][79] polyimide (PI), [80][81][82][83][84][85][86] polyurethane (PU), [22,87,88] polyethylene (PE), [89] and acrylate. [90] The choice in polymeric substrates is directly associated with the application-specific constraints in terms of mechanical, electrical, chemical, and thermal requirements.…”

UV‐Sensitive Wearable Devices for Colorimetric Monitoring of UV Exposure

“…However, these dosimeters do not provide any information about the radiation limit during exposure. Recently, chemical UV dye compositions have been proposed to form color upon UV exposure . These substances usually consist of a colorless precursor and a UV‐sensitive trigger.…”