Wenzel-to-Cassie transition of bio-inspired multiscale surfaces via the multilayer deposition of a carnauba wax-ethanol emulsion

Used for decades, perfluorinated compounds face global concerns due to their impact on human health and the environment, making it necessary to find an alternative. In this article, a facile procedure for the manufacturing of a carnauba-wax based superhydrophobic surface is introduced, without resorting to the use of any polluting additive. Inspired by the lotus effect, this method consists in the recrystallization of carnauba wax (CW) on stainless steel. As part of a biomimetic approach, the latter essentially requires the use of CW and ethanol. This low-cost production method produces a fully biodegradable coating. The obtained coating displays a multiscale surface with reentrant features, allowing air to be entrapped below the water droplet. Through the variation of the number of layers of CW deposited by spray-coating, the effect of the density of CW clusters on the contact angle hysteresis is highlighted, echoing the pioneering experiment of Dettre and Johnson. • Carnauba wax-based superhydrophobic coatings were successfully manufactured. • A stable carnauba wax–ethanol emulsion was synthesized without using any additive. • Incubating the coatings at 75 °C for 30 min generated multiscale surface topography. • Adding layers leads to a Wenzel-to-Cassie transition and a lotus effect. • Pressure-based model shows that inter-cluster spacing is critical for transition.