Fabrication of hybrid structural colors by multi-frequency vibration-assisted fly-cutting

Structural colors generated by periodic micro-nano structures through diffraction and interference exhibit promising application prospects in displays, anti-counterfeiting, and functional coatings. However, traditional periodic structures based on wavelength-selective diffraction make it difficult to directly produce composite colors such as white and magenta. In this study, a multi-frequency vibration-assisted fly-cutting technique is proposed for the fabrication of hybrid structural color surfaces containing multi-frequency components in a single cutting pass. By superimposing three high-frequency vibration signals in the time domain, the vibration trajectory is replicated onto the workpiece surface, creating a surface composed of nested single-frequency gratings corresponding to the red, green, and blue primary colors. Using rigorous coupled-wave analysis (RCWA) combined with the scattering matrix method and validated by finite-difference time-domain (FDTD) simulations, the influence of grating height on the diffraction efficiency of each primary color is systematically investigated. Based on the simulation results, the mixing ratio of the three chromatic components is controlled by adjusting the amplitude of each vibration component, enabling synthesis of target hues (including white, magenta, and so on) via additive color mixing. The machining throughput reaches 0.16 mm²/s, and the experimental color gamut covers nearly the entire sRGB space. Experimental results demonstrate that the proposed method offers significant advantages in expanding the structural color gamut and enhancing color reproduction performance, providing a technical route and theoretical foundation for the high-efficiency fabrication of hybrid structural color surfaces.