Highly hydrophobic surfaces with rose petal-effect based on nanocellulose films coated by nanostructured CuI layers

Inexpensive biodegradable and biocompatible materials, which enable a combination of high hydrophobicity with good adhesion of water droplets, as on rose petals, are in demand for modern microfluidic systems. To obtain surfaces with rose petal-effect we used nanocellulose as bio-based non-toxic material with nanoscale structure. Two types of lightweight flexible nanocellulose films were investigated, differing in raw material and manufacturing method, NC m from Miscanthus x giganteus and NC p from Phragmites australis . They were coated with semiconductor cuprous iodide (CuI) films using Successive Ionic Layer Adsorption and Reaction method, thereby creating hierarchical structures. The deposition of CuI films increased roughness of the NC p and NC m surfaces and ensured high hydrophobicity of the obtained CuI/NC p and CuI/NC m film samples due to chemical modification of nanocellulose. These samples have water contact angles 143°, and large wetting hysteresis above 80°. The water droplets sticking on them testify to the Cassie-impregnating state. On the inclined surfaces of the CuI/NC p and CuI/NC m film samples water droplets do not roll down even if tilt angles reach 90°. So, in this study, we report a facile process for making green, renewable, and biodegradable material with surface functionalities that are relevant for lab-on-a-chip microfluidic devices. Graphic abstract