Poly Methacrylic Acid Sodium Salt (PMANa)/Polyurethane (PU) Latex-Polyelectrolyte Colloid Systems Enabling One-Pot Fabrication of Nonperiodic Structured Mechanoresponsive Smart Windows

Bio-inspired Mechanically Responsive Smart Windows for Visible and Near-Infrared Multiwavelength Spectral Modulation

Mechanochromic light control technology that can dynamically regulate solar irradiation is recognized as one of the leading candidates for energy-saving windows. However, the lack of spectrally selective modulation ability still hinders its application for different scenarios or individual needs. Here, inspired by the generation of structure color and color change of living organisms, a simple layer-by-layer assembly approach toward large-area fabricating mechanically responsive film for visible and near-infrared multiwavelength spectral modulation smart windows is reported here. The assembled SiO2 nanoparticles and W18O49 nanowires enable the film with an optical modulation rate of up to 42.4% at the wavelength of 550 nm and 18.4% for the near-infrared region, separately, and the typical composite film under 50% stretching shows ≈41.6% modulation rate at the wavelength of 550 nm with NIR modulation rate less than 2.7%. More importantly, the introduction of the multilayer assembly structure not only optimizes the film's optical modulation but also enables the film with high stability during 100 000 stretching cycles. A cooling effect of 21.3 and 6.9 °C for the blackbody and air inside a model house in the real environmental application is achieved. This approach provides theoretical and technical support for the new mechanochromic energy-saving windows.

Nano-enabled smart and functional materials toward human well-being and sustainable developments

Fabrication and operation on increasingly smaller dimensions have been highly integrated with the development of smart and functional materials, which are key to many technological innovations to meet economic and societal needs. Along with researchers worldwide, the Waterloo Institute for Nanotechnology (WIN) has long realized the synergetic interplays between nanotechnology and functional materials and designated 'Smart & Functional Materials' as one of its four major research themes. Thus far, WIN researchers have utilized the properties of smart polymers, nanoparticles, and nanocomposites to develop active materials, membranes, films, adhesives, coatings, and devices with novel and improved properties and capabilities. In this review article, we aim to highlight some of the recent developments on the subject, including our own research and key research literature, in the context of the UN Sustainability development goals.

Smart thermally responsive perovskite materials: Thermo-chromic application and density function theory calculation

With the continuous improvement of human's requirements for temperature control suitable for living, the energy consumption of electrical appliances such as air conditioners has become a major challenge in traditional architectural design. Generally, most of the solar energy passes through the glass to enter and exit the building, but the traditional glass can hardly control the light and heat energy, causing the indoor temperature to change dramatically with the environment. Therefore, it is more urgent to develop green and efficient smart windows. Perovskite is a temperature-adaptive material, which has the ability of phase transition and can adjust its band gap for thermochromic applications. In this work, we study the perovskite-based thermochromic smart window. As a new application of perovskite, a number of experiments have been carried out. However, there is still a lack of theoretical analysis on phase transition mechanisms and crystal structure prediction. Density functional theory (DFT) calculation is the most useful tool in optoelectronics, especially for perovskite crystal. Here, we extracted typical cases from published literature for analysis and comparison and summarized the crystal structure, electronic structure stability, interface engineering, and thermal characteristics employing DFT calculation We believe this work will pave the way for DFT application for the study of thermochromic perovskite.

Nature-inspired robust hydrochromic film for dual anticounterfeiting

Nature-inspired materials have been actively developed for anticounterfeiting applications. Among a variety of stimuli-responsive anticounterfeiting strategies, hydrochromic materials exhibit reversible color change in response to moisture or water and have the advantage of being easy to authenticate. However, the security level of current hydrochromic anticounterfeiting materials is not sufficient for practical applications since they only exhibit a single anticounterfeiting function, where the information switches between visible and invisible. To improve the security level and efficiency of hydrochromic anticounterfeiting materials, here we developed a robust dual hydrochromic material via the self-assembly of polyurethane (PU)-polyelectrolytes colloids with which the desired information can not only switch between visible and invisible but also transform from one pattern to another within 3 s without the need of any external instruments. The bio-inspiration, material design and demonstrated hydrochromic properties might have profound implications for using colloidal complexes to make advanced anticounterfeiting materials.

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Micro-structures are formed by self-assembly of polyurethane-polyelectrolyte colloids

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Information changes from one pattern to another within 3 s when exposed to water

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The hydrochromic films are mechanically robust in both dry and wet state