Optical properties of water absorbing textiles for camouflage

Background matching is an essential form of camouflage, adopted by humans especially within military applications in terms of signature reduction. Recent sensor developments have created a need for novel camouflage effective in shortwave infrared (SWIR). The absorption of electromagnetic radiation in SWIR is heavily influenced by water. In a forest environment, the water content in plants is of considerable importance. Therefore, it can be inferred that fabrics with higher moisture levels would exhibit reduced detectability in SWIR wavelengths when compared to their dry counterparts. In this study, the optical properties of different fabrics, both in their dry and hydrated state, was evaluated with SWIR imaging and UV-VIS-NIR spectroscopy and compared to foliage. Two methods of hydration were used, water and nanocellulose. In addition, an assessment of the evaporation of water from the hydrated fabrics samples was carried out. Two fabrics were surface treated with hydrophobic compounds in order to modify the evaporation. The treatments included water-repelling agents and silica nanoparticles (SNPs). The hydrophobic surface modifications did not appear to prolong the evaporation of water from the studied fabrics. Hydrating the fabrics appears to transform the electro-optical signature to closely resemble foliage.