Impact of cellular structure on the thickness and light reflection properties of structural color layers on diverse wood surfaces

Abstract

ABSTRACT This study employed microsphere self-assembly to fabricate structural color layers on surfaces of seven woods. The wood cell structure, thickness of structural color layers, and optical reflection characteristics were analyzed. It was found that the main reflection wavelengths of structural color layers were all located at 490–500 nm. However, differences were observed in the reflection curves, as the thickness of structural color layers affected the width of reflection peak and the background reflection intensity. The water transport cells on wood surface are vessels in hardwood and tracheids in softwood. When they have larger diameters, higher numbers, and better internal patency, they can transport the emulsion, resulting in overflow and seepage. This reduced the number of microspheres, and led to thinner structural color layers with flatter and lower reflection peaks. The theoretical thickness of structural color layers were also calculated. By comparing the theoretical thickness of the structural color layers in two different crystal forms with the measured thickness, the influence of microsphere filling in vessels/tracheids and emulsion overflow on the thickness and optical reflection characteristics of the structural color layer was verified. This provides support for the development of controllable construction for structural color layers suitable for different woods.