Ming Xiao

A humidity-assisted strategy is reported for fabricating self-standing photonic membranes assembled from presynthesized imine-linked COF particles.

Structurally colored materials that change color upon mechanical stimuli have broad potential in stress sensors, wearable devices, and artificial skin. Such materials are conventionally prepared through the self-assembly of colloidal nanoparticles or block copolymers, a process that often involves time-consuming synthesis and purification as well as color inhomogeneity. To enable a simple and scalable route to mechanochromic materials, we employ holographic photopolymerization to fabricate monolithic, structurally colored elastomers. High reflectance and elasticity are achieved by adjusting the matrix formulation, the concentrations of recording monomers and acrylate cross-linker, the film thickness, and the exposure dose. The resulting materials exhibit a relative reflectance above 90% and a reversible mechanochromic shift of approximately 70 nm under 20% tensile strain. This work offers a practical approach to developing mechanically responsive photonic materials for sensing and anticounterfeiting applications.

Structural colouration arises from the interaction of light with nanoscale structures and offers sustainable alternatives to pigment-based colours. However, current structural colour patterning methods rely on multi-step lithographic processes or multiple ink formulations, limiting scalability and spatial resolution. Inspired by melanosome self-assembly in bird feathers, we develop a one-step, mask-free strategy to generate high-resolution structural colour patterns via tunable nanoparticle segregation. During photocuring, silica nanoparticles dispersed in acrylic resin migrate toward oxygen-permeable substrates, forming a nanoparticle-enriched disordered layer. Such segregation is driven by interfacial oxygen inhibition and kinetically governed by the photocuring rate. Using grayscale digital light processing printing, we programmably control the local segregation thickness to create high-resolution structural colour patterns for visual display and information encryption. The segregation structure also affects mid-infrared reflectivity, allowing for infrared camouflage. This scalable approach establishes a mechanistically guided route to multifunctional photonic materials.

Dynamic switching between daytime radiative cooling (DRC) and solar heating (SH), adapting to varying environmental conditions, offers an energy-saving and sustainable solution for all-seasonal thermal regulation of buildings and other outdoor facilities. However, many existing SH/DRC switchers can only alternate between high transmission and high reflection in the solar spectrum, hindering the effective harvesting of solar energy. Herein, by integrating the reversible metal electrodeposition technology and optical metamaterial absorber for the first time, we develop a novel device enabling in situ and active switching between SH/DRC states with a large modulation contrast of ΔA_sol = 0.82, whose superior performance is further validated by outdoor temperature measurements and building level energy-saving simulations. Our work not only opens new opportunities for thermal regulation devices and materials with higher environmental adaptability but also highlights the promising role of RMED in realizing highly efficient dynamic photonic devices.

Two-dimensional (2D) scattering spectroscopy is a powerful, noninvasive approach for characterizing structural order in colloidal assemblies, yet conventional techniques like small-angle X-ray/neutron scattering face inherent limitations in resolving microscale architecture and require costly, nonportable infrastructure. While visible-light scattering offers a cost-effective alternative for benchtop analysis, its utility is constrained because of multiple scattering in dense media and a limited spatial sampling range. To overcome these challenges, we here develop a compact 2D light-scattering system that integrates polarization filtering to selectively detect single-scattering signals and employs multi-angle illumination to extend accessible scattering angles for probing submicron scales. Based on the single-scattering model, we can extract the structure factor from different isotropic colloidal assemblies with either hard-sphere or electrostatic interactions. By coupling the scattering patterns with molecular dynamics simulations, we can further obtain the particle positions in three dimensions. In addition, this system can be used to resolve anisotropic deformations in elastic colloidal films. This cost-effective, lab-scalable platform offers a robust tool for probing structure-function relationships in colloidal and soft matter systems.

Precisely controlling structural colours in polymeric materials remains a major challenge, with current approaches often relying on trial-and-error synthesis. Here, we develop a colour design model, enabling inverse design of structural colours in bottlebrush block copolymers (BBCPs). The model can quantitatively link BBCP molecular structures to macroscopic colours through the integration of a strong segregation self-consistent field theory model with a multilayer optical framework. We first validate its predictive capability by synthesising and assembling BBCPs with varied chain architectures to produce a full colour spectrum, and then demonstrate its generalisability to other BBCP chemistries. In addition, we observe reversible, nonlinear thermochromism in systems combining a crystalisable block with a soft, low–glass transition temperature segment, while similar BBCPs lacking this pairing show no such response. Our work establishes a predictive platform for designing structurally coloured, thermoresponsive polymeric materials and advances the rational engineering of photonic soft matter.

Disordered structures with short-range correlation exhibit unique photonic or thermal properties, often arising from the self-assembly of monodisperse microspheres. Colloidal clusters, aggregates of a defined number of microspheres, have anisotropic shapes and offer a unique approach to tailor the short-range correlation compared to traditional isotropic microspheres. However, this potential remains largely unexplored. To this end, we have prepared triangular and tetrahedral colloidal clusters and coassemble them with polystyrene microspheres into both monolayers and thick films (∼10 μm) over 5 mm × 5 mm areas. Through combining scanning electron microscopy images and laser scattering measurements, we show that increasing cluster concentration from 0% to 40% increases disorder in both thin and thick films. Beyond 40%, the short-range order in thin films plateaus, while it increases with triangular clusters but decreases with tetrahedral clusters in thick films. The distinct roles of triangular and tetrahedral clusters offer new insights into design of correlated disordered materials for novel applications.

We report an abnormally thermochromic composite whose discoloration time can extend for 6–8 hours. By revealing its color changing mechanism, we demonstrate that this composite can be used in smart windows and information coding.

Electrochromic (EC) materials can dynamically manipulate transport of light and thermal radiation under the electric field, which are promising for applications such as smart windows and energy-saving display devices. The color switching mechanism in EC materials is mainly based on optical absorption, resulting in excessive solar thermal load when used outdoors. Although daytime radiative cooling (DRC) provides a possible solution for energy-efficient heat dissipation for these outdoor devices, it often leads to a white appearance incompatible with EC color displays. To address this challenge, we develop novel display devices that can simultaneously realize color switching and DRC, enabled by reconfigurable, high-quality optical nanocavities based on reversible metal electrodeposition. These devices can not only achieve sub-ambient cooling of 2.6 ~ 5.3 ℃ under direct sunlight but also exhibit multiplexed adaptive displays with diverse colors, high stability, and long cycle life. Based on worldwide building-level energy simulations, we show this novel display can potentially save electrical energy consumption of 0.8–23.1 kWh/m² compared to conventional LED displays, providing a new paradigm of passively cooled dynamic color display.