Optical modeling of cellulose nanofibril self-assembled thin film with iridescence

Nanostructure-induced structural coloration and bio-invisibility are important for camouflaging as it displays color and can be tuned and imparted in a more environmentally friendly manner. However, even though many new camouflage fabrics and technologies are invented, there is a lack of numerical electromagnetic and optical approaches to analyze the phenomenon of light scattering of camouflaging materials from nanostructures. In this study, we built and presented a successful simulation of physical coloration caused by multilayer membrane interference. We created this model based on surfactant-like cellulose nanofibrils (CNFs) that tightly stacked into photon-active microstructure and surface topology for light reflection, thus affecting the film gloss. Incident light coming at a defined wavelength or angle was studied. The effects of film height, high microstructure, and curvature on the optical properties of ITO/PET substrates were investigated. These showed the coloration is highly dependent on the nanostructure’s characteristics. This study provides a general prediction model to deal with optical multilayer systems where interference plays a vital role in optical camouflaging, etc.