Recent Advances and a Roadmap to Wearable UV Sensor Technologies

Abstract

The tremendous impact of UV radiation on every individual has resulted in massive interest in development of new sensor technologies to effectively monitor the solar exposure. However, there is no comprehensive review that critically discusses the advances made in the field of wearable UV sensor technologies and to position them as next‐generation mass‐deployable wearable devices. Herein, this gap is addressed by first classifying UV detection technologies into photoelectric and photochromic systems and summarizing their unique strengths and drawbacks. This is followed by a discussion on the integration of novel materials and design concepts with these technologies to develop wearable UV sensors. Then, the commercially available wearable UV sensors are examined thoroughly together with their limitations. Toward the end, a highly critical future outlook is provided, wherein the role of technological and regulatory interventions in assisting the development and integration of wearable UV sensors in the day‐to‐day activities is discussed. More importantly, the purpose of this review is not only to provide an in‐depth understanding of the underlying UV detection mechanism, design principles, and wearable technologies but also to act as a roadmap for those interested in the development and regulation of commercially deployable wearable UV sensors.

Spiropyran‐Functionalized Polymer–Carbon Nanotube Hybrids for Dynamic Optical Memory Devices and UV Sensors

“…Optical memory devices that can reversibly change their conductance state depending on exposure to light of a certain wavelength are of great interest for data storage, [1] radiation dosimeters, [2] and even as photogated components of neuromorphic circuits. [3] Ideally, these memory elements should be as graphene, [14] mono-and few-layer transition metal dichalcogenides (e.g., WSe 2 or MoS 2 ), [15] and single-walled carbon nanotubes [9b,16] are interesting materials for photoactive devices [17] due to their high charge carrier mobilities, inherent flexibility, and their large surface area, which can be modified and functionalized with a substantial impact on their properties.…”

“…Optical memory devices that can reversibly change their conductance state depending on exposure to light of a certain wavelength are of great interest for data storage, [ 1 ] radiation dosimeters, [ 2 ] and even as photogated components of neuromorphic circuits. [ 3 ] Ideally, these memory elements should be easily processable (e.g., from solution and on flexible substrates), operate at low voltages, have long retention times, allow for a large number of distinguishable conductance states to be programmed, and should be easily readable and erasable in a controlled manner.…”

“…One desirable application of such optical memory elements is wearable UV dosimeters that can track the total exposure to harmful ultraviolet radiation. [ 2,10 ] Practical devices of this kind require mechanical flexibility and low operating voltages. Ideally, these sensors should be blind to visible light and resettable, i.e., reusable.…”

Fast-Response Colorimetric UVC Sensor Made of a Ga2O3 Photocatalyst with a Hole Scavenger

“…As the UVC light is widely used, it is important to monitor UVC irradiation increases for safety and exposure management because exposure to UVC light negatively affects DNA in the skin and eyes, leading to genetic damage and mutations [ 6 , 7 , 8 ]. It should also be noted that the UVC radiation effect on humans is cumulative; thereby it is also important to monitor the cumulative radiation dose [ 9 ]. All these necessitate the need for a UVC sensor that is capable of the quantification of accumulated UVC doses with fast responsivity.…”

“…Recently, colorimetric UVC sensors made of gallium oxide (Ga 2 O 3 ) with an energy bandgap of about 4.9 eV have drawn increasing attention due to their low cost, simplicity, and ability to easily quantify an accumulated dose [ 9 , 10 , 11 , 12 , 13 ]. Although TiO 2 (3.2 eV) and ZnO (3.4 eV) could be considered for photoelectrochemical reactions under UVC radiation, Ga 2 O 3 (4.9 eV) showed a much better UVC sensitivity compared to TiO 2 and ZnO [ 13 ].…”