Super-Black Material Created by Plasma Etching Wood

Abstract

A super-black wood with low reflectivity in the UV/Vis range is created by plasma modifying basswood surfaces. Here the super-black wood is characterized, the process used to make it is described and its possible practical uses are discussed. Wood samples are exposed to oxygen glow-discharge plasma. Transverse surfaces exposed to high-energy plasma have a deep-black velvety appearance. The reflectance of these surfaces is measured and compared with those of commercial super-black materials. The reflectivity of samples over a narrower wavelength range is measured with a spectrophotometer and converted into lightness values. The microstructure and surface chemistry of super-black wood are examined using SEM/X-ray micro-CT and FTIR spectroscopy, respectively. Transverse basswood samples modified with high-energy plasma have reflectivity averaging 0.68% (300–700 nm). The super-black color of plasma-modified wood is retained when it is coated with gold/vanadium alloy indicating structural coloration. Plasma creates a low density, lignin-enriched surface with deep pits, columns and tangled fibrils; features also found in synthetic super-black materials. In conclusion, this method of creating a super-black material by plasma-modification of basswood does not require a lithography pre-step, generates no liquid waste and, as is demonstrated here, can be used to prototype luxury consumer products.