High-Resolution Optical Displays Based on Electromechanically Reconfigurable Open-Loop Nano-Kirigami Structures (Invited)

Optical micro-display technology serves as a core support for information transmission and security encryption, playing a crucial role in fields such as optical anti-counterfeiting, multi-channel information processing, and secure information transmission. Current optical micro-display schemes mostly rely on traditional optical modulation devices or fixed-configuration micro-nano structures, which are limited by large device volume, poor on-chip integration compatibility, and low display resolution. Additionally, existing metasurface-based information encryption studies are mostly confined to passive regulation, leaving significant room for improvement in dynamic controllability and display resolution. To address these challenges, there is an urgent need to develop new research strategies that can simultaneously achieve high-resolution display and on-chip integration compatibility. This study aims to propose a high-resolution optical information display scheme based on electromechanically reconfigurable open-loop nano-kirigami structures, breaking through the limitations of existing technologies and providing a new path for the development of related fields. First, three types of open-loop nano-kirigami structures (square, circular, and hybrid) are designed. The square structure is constructed by rotating a square by 45°, the circular structure is formed by adjusting the opening angle of a standard circle, and the hybrid structure is a “horseshoe” shape combining half of the square and circular structures. The structural parameters are set as follows: unit period of 1.45 μm, gold film thickness of 60 nm, gap width of 70 nm, side length D of 0.8 μm, opening length l of 0.16 μm, central square hole side length d of 0.15 μm, and the arc length s corresponding to a 30° opening angle. Subsequently, numerical simulations of the electrical and optical properties of the designed structures are performed using the COMSOL Multiphysics finite element software. The electrostatic and solid mechanics modules are coupled to simulate the electromechanical deformation and displacement relationship of the structures, and the optical modulation contrast under different voltages is calculated based on the reflection rate changes before and after voltage application. For experimental fabrication, a multi-step process is adopted: electron beam evaporation is used to deposit a 5 nm chromium adhesion layer and a 60 nm gold film on a commercial SiO2/Si substrate; electron beam lithography (EBL) is employed for large-area patterning after spin-coating polymethyl methacrylate (PMMA) photoresist; ion beam etching (IBE) is used to etch the gold film under the photoresist mask; reactive ion etching (RIE) is applied to remove residual PMMA; and isotropic wet etching with dilute hydrofluoric acid (volume ratio V(HF)∶V(H2O)=1∶4) is performed to remove the underlying SiO2 and form suspended structural arrays. The morphology of the fabricated structures is characterized by scanning electron microscopy (SEM). Finally, an in-house opto-electromechanical integrated testing system is built for performance verification. The system consists of an optical module (halogen light source, optical fiber transmission, reflector), an electrical module (source meter for applying direct current voltage), and an optical capture module (spectrometer and charge coupled device (CCD) dynamic capture device). The reflection spectra and optical modulation contrast of the structures under different voltages (0-36 V) are tested in the 500-1000 nm wavelength range, and dynamic reversible encryption and display tests of high-resolution patterns are carried out under bright-field and dark-field conditions. Simulation results show that with the increase of voltage in the range of 20-50 V, the deformation displacement of the three structures gradually increases, and the square structure exhibits the largest deformation displacement (191 nm at 39 V) under the same voltage (Fig. 1(c)). For optical properties, the modulation contrast increases with voltage, and two key patterns are observed: the larger the opening degree of the same structure, the lower the optical modulation degree; among the three structures, the square structure achieves the maximum optical modulation contrast under the same voltage (Figs. 1(d)-(f)). These results indicate that the square structure has superior electromechanical and optical regulation performance. SEM characterization confirms the successful fabrication of large-area, high-precision, and uniform open-loop nano-kirigami structure arrays (Figs. 2(d)-(g)), with clear structural morphology and consistent dimensions matching the design parameters, laying a solid foundation for subsequent tests. Opto-electromechanical reconfiguration tests show that the square structure has a higher reflectivity in the planar state (Fig. 3(b)). As the applied voltage increases to 36 V, the modulation contrast at short wavelengths exceeds 30%, and the average reflection modulation contrast approaches 20% (Figs. 3(c)-(d)), demonstrating a significant correlation between optical response and electromechanical reconfiguration degree. For high-resolution optical information encryption and display, the square structure arrays with opening lengths L1=l (soft stiffness, low-voltage response) and L1=4l (hard stiffness, voltage-insensitive) are arranged to form the “BIT” pattern and background, respectively. Dynamic capture results show that under voltage switching between 0 V and 32 V, the pattern achieves dynamically reversible hiding and manifestation under both bright-field and dark-field conditions (Figs. 4(b)-(c)), with the 1.45 μm period pixel unit ensuring high-resolution display performance, as verified by the supplementary videos. In summary, we theoretically designed and experimentally realized high-resolution optical information encryption and display based on electromechanically reconfigurable open-loop nano-kirigami structures. Through comparative analysis of three open-loop configurations, the square structure is identified as optimal for its superior electromechanical and optical properties. The fabricated arrays, with a period of only 1.45 μm, achieve electrically controlled and dynamically reversible switching under both bright-field and dark-field conditions, exhibiting an average optical modulation contrast approaching 20% at 36 V. This work successfully downscales the minimum pixel unit from 2.2 μm to 1.45 μm, increasing the information carrying density by more than two times. This strategy, which integrates nano-kirigami manufacturing with on-chip opto-electromechanical actuation, overcomes the resolution limitations of existing technologies. It opens new avenues for high-density optical encryption, multi-channel information processing, and micro-/nano-manipulation. Future efforts will focus on optimizing real-time programmable capabilities to further expand the practical application scenarios of nano-kirigami information displays.