Study on the wettability of microsphere-containing emulsion on different wood surfaces

Applying microsphere-containing emulsion onto wood surfaces can enable microspheres to self-assemble into photonic crystal structures, generating structural colors that serve to decorate the wood surfaces. Wettability of the wood surface to emulsions significantly influences the construction of structural color layers. The wettability is further modulated by the inherent species-specific characteristics of the wood. To elucidate the differences in wettability of emulsions on wood surfaces, this study selected seven wood types, analyzed the changes in the contact angles of emulsions on their surfaces in different directions. It was found that the initial contact angle in parallel-fiber direction of wood was generally smaller than that in perpendicular-fiber direction, indicated that the parallel-fiber direction was more easily wetted by the emulsion. After the emulsion was dripped onto the wood surface and an initial contact angle was formed, it would rapidly spread and gradually penetrate into the wood. The properties of the main transport cells directly affected the change in contact angle. The emulsion transmission ability of hardwood was better than that of softwood, but this was not an advantage for assembling structural color layers. It was found that the change pattern conformed to the characteristics of an exponential function through non-linear fitting analysis.