Responsive Smart Windows Enabled by the Azobenzene Copolymer Brush with Photothermal Effect

ACS Appl. Mater. Interfaces

et al. 2021

Rewritable paper, as an environment-friendly approach of information transmission, has potential possibility to conserve energy and promote a sustainable development of our society. Recently, photonic crystals (PCs) have become a research hotspot in the development of rewritable paper. However, there are still many shortcomings that limit the further application of PC paper, such as slow response sensitivity, short-cycle lifetime, poor storage stability, and so on. Herein, we constructed an optically rewritable azobenzene inverse opals (AZOIOs) with a thin film (ca. 1 μm) plated on an inverse opal structure based on the UV/vis switchable structure color of the sample. The top thin film acts as a protective layer to avoid the large deformation of the pore structure and the bottom inverse opal structure with refractive index/pore structure change that provides reversible structure color. Large, reversible, and rapid bandgap shift (ca. 60 nm, 2 s) of AZOIOs can be repeated more than 100 times under alternating UV/vis irradiation based on isomerization of high content of the azobenzene group. On-demand long-time preservation pattern can be obtained by the appearance of azobenzene’s intrinsic color. The proof of concept for rewritable PC paper is demonstrated herein. Such inkless rewritable colorful paper paves a way for developing novel display technology.

Section: Resultsmentioning

confidence: 99%

Inkless Rewritable Photonic Crystals Paper Enabled by a Light-Driven Azobenzene Mesogen Switch

Liu

ACS Appl. Mater. Interfaces

et al. 2021

“…Alignment layers play a very important role in many LC devices. [ 27–32 ] Nowadays, the alignment layer is usually made from polyimides because of their chemical and thermal stabilities. The aligning direction with respect to the substrate of the alignment layer depends on the interaction between the alignment layer and the LC.…”

Section: Thermally Regulated Surface Anchoringmentioning

confidence: 99%

Smart Thermally Switchable Liquid Crystal Window

Jiang

Zhou

Advanced Photonics Research

et al. 2021

Global warming, due to the consumption of fossil energy, is one of the biggest challenges in recent days. Air conditioning (cooling and heating) of office and residential buildings is one of the largest energy consumptions. One way to reduce the energy consumption is to use switchable architectural windows, which can control radiant energy flow. Herein, a smart thermally switchable window with transmittance sensitive to ambient temperature is reported. This smart window is based on a liquid crystal (LC) whose orientation varies with temperature. At temperatures lower than a low threshold temperature, such as in winter, the LC orients perpendicular to the window substrate, and the window is transparent and lets sunlight pass it to warm interiors of buildings. At temperatures higher than a high threshold temperature, such as in summer, the LC orients parallel to the substrate. The window becomes absorbing and blocks sunlight, resulting in a reduction of the solar heating. When temperature varies between these two thresholds, the window has gray‐level transmittances. It does not use electricity and is very energy‐saving, and has an immense potential in applications of smart architectural and vehicle windows.

“…Then, an AC electric field is applied on the writing board, ChLC orientation transforms the planar reflective texture into focal conic texture, the incident light does not reflect, and hence the display image is erased. Nowadays, ChLC films such as smart windows can achieve both thermal and UV responses [29]. The most important challenge for the ChLC handwriting tablet is that users hope to clear part of the writing content.…”

Section: Introductionmentioning

confidence: 99%

An Electrically and Thermally Erasable Liquid Crystal Film Containing NIR Absorbent Carbon Nanotube

Miao

2022

Molecules

Carbon nanotubes (CNTs) coated by a poly(vinylpyrrolidone) (PVP) layer were doped in bistable cholesteric liquid crystal (ChLC) film to provide electric, thermal, or optical erasability controllable films. The CNT/PVP formed a compatible NIR-absorbing film that can generate heat to switch ChLC film from a planar texture to a focal conic texture. The appropriate content of CNT/PVP is provided to achieve a fast thermal response, satisfactory dispersion, and clear display brightness. The ChLC film containing CNT/PVP @ 0.8 (wt.%) saves 51% time at thermal erasing, compared to the ChLC mixture without NIR absorbent. The hybrid organic–inorganic bistable ChLC material reported here extends and offers new applications of ChLC writing tablets.