Beijing University of Chemical Technology, Professor Wei Jie team: \”never fade,\” the near-infrared light in response to real-time structural color flexible screen

Stimulus response photonic crystal to change the photonic crystal lattice spacing incentives such as temperature, electric field, magnetic field the pH, solvent, and drugs can be lower then change the external fields structural color. In various stimuli, the non-contact driving mode, especially in the near-infrared light, has a strong penetrating characteristics and the heat adjustable and controllable during irradiation, having a remote drive, and immunotherapy precision medical fields potential applications. However, a large area of ​​rapid preparation of a photonic crystal device is a real-time response to address key issues photonic crystals in practical application. School of Materials Science and Engineering, Beijing University of Chemical Technology Professor Wei Jie team advances have been achieved (Sens. Actuators, B series responsive photonic crystals in terms of assembly, 2018 , 273:… 1705-1712; Part.Part Syst Charact 2019, 1900238; Nanotechnology, 2019, 30 (50): 505706; Dyes and Pigments, 2018, 148:. 108-117; Macromol Rapid Commun.2018, 39 (20): 1800134.) based on these preliminary studies, recently the team by changing the acrylate aqueous coating film hydrophilic, monodisperse poly (styrene – methyl methacrylate – acrylic acid) latex particles in a uniform roll thermochromic acrylate film (FIG. 1a), and self-assembled to form a short-range ordered structure of the photonic crystal opal (FIG. 1b, c), using a ring-opening structure of melanin -2 latex particles before and after reaction with color thermochromic film (FIG. 1d, e), and a near-infrared light controllable photonic crystal film, and a photonic crystal tag successfully constructed bendable NIR response and photonic crystal multicolor display in real time a flexible material.

Figure 1. Wen Minguang sub-crystal thin film preparation process (a), a short-range ordered structure of the photonic crystal opal micro- and nanostructures (b, c), formula before and after heating of melanin -2 ( d), infrared spectra (e).

Such a thermal type photonic crystal film due to the layer containing the latex particles a large number of carboxyl groups, and water temperatureSensitive membrane can efficiently bind (FIG. 2). By changing the content of the aqueous precursor film temperature sensitive water, to further enhance the bonding force between the photonic crystal layer with temperature sensitive film, the durability of the composite film. Temperature-sensitive modifying the photonic crystal film can be bent at any angle, and exhibit excellent flexibility (for 10,000 fold test, almost no change in the structural color film and cracks).

Figure 2. The bonding mechanism at the interface Wen Minguang photonic crystal film (a), change in contact angle (b, c) a hydrophilic film before and after improvement.

temperature-sensitive film at room temperature to a dark gray, the photonic crystal film absorb excess ambient light scatter, effectively increase the relative strength of the photonic bandgap (FIG. 3A); when the temperature is above the critical temperature, the temperature a gray-black-sensitive membrane rapidly becomes translucent milky white latex particles with the same color of the body, since the refractive index close to both the rapid increase in the transparency of the film (FIG. 3b, c), color undergone significant structure on a macroscopic changes, hidden fields can be used to display information.

Figure 3. Wen Minguang photonic crystal film discoloration mechanism (a), the film before and after discoloration physical map (b), the transparency of the film (c) before and after heating.

On the heat-sensitive photonic crystal film and the binary-coded label containing binding (FIG. 4), the sub-label Wen Minguang crystal film with the binary-coded composite is bonded to the bottle and is bent bottle, successfully constructed bendable photonic crystal tag near-infrared light in response to the , through the photonic bandgap intensity regions designated irradiating near-infrared light is significantly decreased, the macroscopic performance of the transparency of the photonic crystal film is increased, from the photonic crystal reflection state to a transparent state, the display pattern information of binary code, information reading reversible; sustainable region after irradiation at room temperature for about 10s, was returned to the photonic crystal reflective state.

Figure 4. bendable photonic crystal tag information reading mechanism in response to NIR (a), before and after the photonic crystal color label physical map (b), for recording information (c) on the surface .

Wen Minguang use of photonic crystal film further excellent flexibility successfully constructed bendable NIR photons in response multicolorA flexible real-time display crystal material . 980 nm by the irradiation point of near-infrared light, the intensity of the irradiation area of ​​the photonic bandgap changed obviously, the difference with the naked eye can be distinguished form non-irradiated region, to achieve a Real-time information is written with a non-contact type erasing [123 ], and exhibit high flexibility and durability, the optical performance of the device before and after bending good stability (FIG. 5).

北京化工大学魏杰教授团队:“永不褪色”的实时近红外光响应结构色柔性屏幕 Figure 5. multicolor Wen Minguang sub-crystal thin film preparation process (a, b), near-infrared non-contact information recording and erasure (c, d) in the photonic crystal film.
In summary, this study presents the temperature-sensitive film and the color of monodisperse latex particles from a large area quickly assembled by roll coating method, a method of preparing the crystal structure of the composite film Danguang Zi short range order protein forms. The design principle is simple, flexible film significantly improved, photonic crystals for real-time information is written in non-contact with respect enlightening erased, the security design. The paper was published in

\”ACS Applied Materials & Interfaces\” , entitled \”Controllable Structural Colored Screen forReal-time Display via Near-Infrared Light\”, is the first author of the paper Beijing University of Chemical Technology doctoral student Huang Chao , Professor Wei Jie for the corresponding author. This work was supported by the National Natural Science Foundation of China (51873009,51573012) and Beijing Natural Science Foundation (2192042) funding. Document link: https: //