Screen-Attachable Visual Hydrogel Indicator for In-House Monitoring of Blue Light from Electronic Products

With the widespread use of personal electronic devices, excessive blue light exposure that causes retinal cell damage and skin hyperpigmentation has attracted increasing attention. However, an effective indicator for real-time in-house monitoring of blue light is still lacking. In this study, we developed a screen-attachable visual hydrogel indicator for facile in-house monitoring of blue light. The indicator is fabricated by encapsulating both a blue light-responsive photosensitizer (fluorescein) and 3,3′,5,5′-tetramethylbenzidine (TMB) within an agarose hydrogel. Upon exposure to blue light, the photosensitizer generates reactive oxygen species (ROS), which oxidize colorless TMB to blue oxTMB. The proximity of fluorescein and TMB within the hydrogel nanopores significantly facilitates the oxidation reaction. Hence, using a hydrogel as the reaction carrier not only makes the indicator screen-attachable but also greatly enhances its sensitivity. The color change of TMB is good linearly with the blue light doses in the range of 0.15–1.2 J/cm2 with a detection limit about 0.082 J/cm2, much lower than the threshold (0.75 J/cm2) for oxidative eye stress. Green and red light from the electronic products caused no interference for the monitoring of blue light. It was successfully applied for monitoring the cumulative dose of blue light emitted from the three types of electronic products (i.e., laptops, tablets, and light-emitting diode (LED) lamps) by simply attaching the indicator on the screen or on the desk. This hydrogel indicator, with the merits of screen-attach ability, facile use, and high sensitivity, is quite appealing for in-house monitoring of blue light from electronic products.