Smart Windows Self-Illuminate on Rainy Days

Smart windows that automatically change colors depending on the intensity of sunlight are gaining attention as they can reduce energy bills by blocking the sun's visible rays during summer. But what about windows that change colors depending on the humidity outside during the monsoon season or on hot days of summer? Recently, a Korean research team has developed the source technology for smart windows that change colors according to the amount of moisture, without needing electricity. The team successfully developed a variable color filter using a metal-hydrogel-metal resonator structure using chitosan-based hydrogel and combined it with solar cells to make a self-powering humidity sensor.