A facile method for the fabrication of colloidal photonic crystal coatings with tunable structural color on a wood surface was presented. The photonic crystal coatings were formed from monodisperse latex spheres composed of poly(styrene-methyl methacrylate-acrylic acid) (P(St-MMA-AA)). The latex spheres with a hard PSt core and elastomeric P(MMA-AA) shell were prepared using the emulsion polymerization method. The sessile drop method, a rapid single-step self-assembly method through simple evaporation of emulsion, was used to form three-dimensional colloidal crystals. Coatings with brilliant colors and uniform Bragg’s diffraction covering the entire visible region were fabricated by controlling the sphere size. This simple method provided new insight into the development of wood color embellishment.

Six kinds of polystyrene (PSt)-based colloidal microspheres were synthesized by adding acrylic acid (AA), methyl methacrylate (MMA), and butyl acrylate (BA) as comonomers in styrene emulsion polymerization. The structurally colored coatings on a wood surface were self-assembled by thermally assisted gravity deposition of these microspheres. Chemical compositions and structures of microspheres and morphological characteristics of microspheres and structural color coatings, as well as optical properties of coatings and their generated structural colors, were studied. Pure PSt microspheres had a smooth surface and uniform structure, while microspheres of copolymers had core–shell morphologies and a rough surface. Only poly(styrene-acrylic acid) (P(St-AA)) microspheres had good monodispersity and the resulting coating had a well-ordered photonic crystal structure. However, other kinds of microspheres could form short ranges of ordered amorphous photonic crystal structures and they displayed structural colors. Both the reflectivity of coatings to visible light and structural colors varied with microsphere size and self-assembly temperature.

When utilizing microspheres to construct structural color layers on wood surfaces, the cellular structure of wood can influence the self-assembly of microspheres and the resulting structural color layers. To investigate this influence, seven types of wood were selected in this study, and structural color layers were constructed on their surfaces. A comparative analysis was conducted on the color production and macro and micro morphologies of the structural color layers on different wood surfaces, along with an examination of the types and causes of surface defects. The study found that when a microsphere-containing emulsion was applied to a wood surface, the emulsion tended to flow along the vessels of hardwood and the tracheids of softwood. Overflow or seepage of the emulsion could lead to a reduction in the number of microspheres per unit area, resulting in uneven thickness and uneven color generation of the structural color layers. Although the structural color layers on different wood exhibited the same color, there were variations in their tones, appearance, and morphology. Defects such as minor bumps and pits were present on the structural color layers. Bump defects might originate from microsphere encapsulation of fiber bundles or the displacement of air within vessel lumens by emulsion, while pits were mainly caused by the inflow of emulsion into the vessel lumens. This study clarified the influence of wood surface cells, particularly vessels and tracheids, on the construction and color production of structural color layers, providing support for the controllable modification of wood surfaces using structural colors.

In this study, the brush method was used to construct structural color layers on the surface of European beech wood, which has wide rays. The purpose was to expand the research on the structural color modification of wood surfaces and to promote its industrial application. By comparing the structural color layers constructed through brushing on beech wood and glass surfaces, the construction speed on the wood surface was significantly faster than that on the glass surface, which was mainly attributed to the porous structure and hydrophilicity of the wood, which made the solvents to be absorbed quickly, greatly improving construction efficiency. At the same time, the wide-ray regions of the European beech wood showed distinct and excellent structural color modification effects. This specific effect was not only reflected in faster construction speeds than other regions, but also in a complete and full-color block. Moreover, by changing the particle size, raw material, and structure of the microspheres, and by brushing several times, the special construction phenomenon and decorative effect still existed. By characterizing the surface morphology and roughness of beech wood, it was found that the surface of the wide rays was flatter than other anatomical structural regions, which was more conducive to the self-assembly of microspheres and the formation of a structural color layer. The results of this study will help to advance the development of technologies such as structural color-selective modification of wood surfaces.

Polystyrene (PSt) microspheres were used to construct rainbow-like, seven-colored structural color coatings on wood surfaces by analyzing how the amount of emulsifier SDBS and emulsion polymerization temperature affected the particle size and monodispersity of the microspheres. The influence of both the amount of self-assembled emulsion coating used and the temperature on the reflected spectrum and the color of the coatings was investigated. It was found that the most monodisperse PSt microspheres were obtained when using 175 mg SDBS and a reaction temperature of 70 °C. By adjusting these two factors, we regulated the particle size of the PSt microspheres. When PSt microspheres were self-assembled on a wood surface to form a structural color coating, the best optical effect was obtained with 40.8 × 10⁻³ mL/cm² emulsion amount and 50 °C ambient temperature. Finally, by changing the SDBS amount and reaction temperature, microspheres with different particle sizes and good monodispersity were prepared. The structural color was used to form patterned decorations on the wood surface, providing a technical basis for forming other structural color coatings on wood surfaces.

For a comprehensive understanding of the surface roughness of wood substrates after grinding and its influence on the construction of surface structural color layers (SCLs) and the effect of color production, four typical diffuse-porous wood species were investigated by grinding with abrasive belts of different grits. The results indicated that an abrasive belt of suitable grit was required to form the flattest surface for different wood species. Notably, 400-grit abrasive belts can be used for quaking aspen (QA) and yellow poplar (YP) wood, while 320-grit abrasive belts can be used for kang duan (KD) and hard maple (HM) wood for the grinding process. When the grit of the belt was 80–240, the surface roughness of the wood was high, and the gully contour was mainly determined by the machining marks created by the grits during the cutting process. When the SCLs were constructed on these wood samples, the grooves formed by grit grinding caused the emulsion to overflow on the surface of the wood, thus preventing the formation of well-ordered SCLs with excellent color production. In contrast, when the grit of the abrasive belts was increased to the range of 320–800, the main factors affecting the roughness of the wood surface led to the anatomical structural features. Vessels, in particular, not only affected the surface roughness of the wood but also served as a major path for emulsion flow. The number, diameter, and patency of vessels per unit area were the main factors affecting the SCL’s construction and decoration effect on wood surfaces. This study clarifies that the roughness of the wood surface after the grinding process is jointly influenced by the grit of the abrasive belt and the wood’s anatomical structure. Roughness is an essential factor that affects the modification effect of the SCLs on the surface of wood.