Ghosh Souvik, Abraham Eldho, Smalyukh Ivan I
Department of Physics, University of Colorado, Boulder, Colorado 80309, United States.
International Institute for Sustainability with Knotted Chiral Meta Matter (WPI-SKCM2), Hiroshima University, Boulder, Higashihiroshima 739-8526, Japan.
ACS Nano. 2023 Oct 24;17(20):19767-19778. doi: 10.1021/acsnano.3c03693. Epub 2023 Sep 19.
Being key components of the building envelope, glazing products with tunable optical properties are in great demand because of their potential for boosting energy efficiency and privacy features while enabling the main function of allowing natural light indoors. However, windows and skylights with electric switching of haze and transparency are rare and often require high voltages or electric currents, as well as not fully meet the stringent technical requirements for glazing applications. Here, by introducing a predesigned gel material we describe an approach dubbed "Haze-Switch" that involves low-voltage tuning of the haze coefficient in a broad range of 2-90% while maintaining high visible-range optical transmittance. The approach is based on a nanocellulose fiber gel network infiltrated by a nematic liquid crystal, which can be switched between polydomain and monodomain spatial patterns of optical axis via a dielectric coupling between the nematic domains and the applied external electric field. By utilizing a nanocellulose network of nanofibers ∼10 nm in diameter we achieve <10 V dielectric switching and <2% haze in the clear state, as needed for applications in window products. We characterize physical properties relevant to window and smart glass technologies, like the color rendering index, haze coefficient, and switching times, demonstrating that our material and envisaged products can meet the stringent requirements of the glass industry, including applications such as privacy windows, skylights, sunroofs, and daylighting.
作为建筑围护结构的关键组成部分，具有可调光学性能的玻璃产品需求量很大，因为它们在提高能源效率和隐私功能方面具有潜力，同时还能实现室内引入自然光的主要功能。然而，具有电切换雾度和透明度功能的窗户和天窗很少见，而且通常需要高电压或电流，并且不能完全满足玻璃应用的严格技术要求。在此，通过引入一种预先设计的凝胶材料，我们描述了一种名为“雾度切换”的方法，该方法涉及在2%至90%的宽范围内对雾度系数进行低电压调谐，同时保持高可见光范围的光学透过率。该方法基于由向列型液晶渗透的纳米纤维素纤维凝胶网络，通过向列域与施加的外部电场之间的介电耦合，可以在光轴的多畴和单畴空间模式之间切换。通过使用直径约10 nm的纳米纤维纳米纤维素网络，我们实现了低于10 V的介电切换和在透明状态下低于2%的雾度，这是窗户产品应用所需要的。我们对与窗户和智能玻璃技术相关的物理特性进行了表征，如显色指数、雾度系数和切换时间，证明我们的材料和设想的产品能够满足玻璃行业的严格要求，包括隐私窗户、天窗、天窗和采光等应用。
