Temperature-sensitive ionic hydrogels for dual electric and thermal responsive smart window

Buildings account for approximately 40 % of global energy consumption, with more than half of that attributed to heat loss through windows. Electrochromic smart windows can effectively regulate indoor sunlight and minimize energy consumption under an external electric field. However, single-response mode significantly limits their adaptability in varying environments. Here, we develop a dual electric/thermal-responsive smart window (DRSW) by integrating a conductive deep eutectic mixture (DEM) into a temperature-sensitive poly(N-isopropylacrylamide) hydrogel, which serves as electrolyte in the device. Leveraging the introduced hydrophilic functional groups from the DEM, the yielded hydrogels showcase remarkable luminous/solar transmittance modulation (88.25 % and 71.53 %). Moreover, the interaction between components retain the transportable ions within the hydrogel, which promise the excellent ionic conductivity (>2.34 × 10 −3  S cm −1 ) both before and after phase transition. Drawing upon these unique properties, the integrated DRSW achieves four distinct reversible optical states with notable energy-saving characteristics, which can be passively triggered by ambient temperature, actively induced by an external potential, or stimulated by both. Our findings provide valuable insights for the development of next-generation energy-efficient smart windows, capable of effectively managing incident sunlight, enhancing privacy, and improving aesthetic appeal.