Multi-functional smart bulk hydrogel panels with strong near-infrared shielding and active local control

Thermochromic hydrogel is a versatile smart material that can be used in various applications. In this paper, we present a new concept of smart windows to passively regulate light transmittance and reduce energy consumption while functioning as an information display. By incorporating passive solar regulation and active local control, this window is devised through the multilayer assembly of tailored poly(N-isopropylacrylamide) (PNIPAM) hydrogels and surface-modified photonic crystal films. The modified surface tension of solvent tunes the scattering center size of the hydrogel, and the addition of the photothermal films (PT films) imparts a high near-infrared (NIR) shielding and light-to-heat conversion, which is needed for low-latitude smart window application. Together with high writing speed, clarity, and repeatability for local writing. This new smart hydrogel engineering can have broad applications, allowing more functionalities in designing building façades.