Superhydrophobic coatings with high repellency to daily consumed liquid foods based on food grade waxes

The applications of superhydrophobic coatings in daily life are receiving increasing attention. Here, we report a general approach for preparing superhydrophobic coatings with high repellency to daily consumed liquid foods based on food grade waxes. The coatings are prepared by spray-coating the homogeneous wax suspensions in ethanol followed by annealing at 40 °C. The wax suspensions are formed by the heating dissolution-cooling precipitation-ultrasonication process thanks to the unique solubility of the waxes in ethanol. Ultrasonication of the wax suspension is helpful to improve superhydrophobicity by reducing the size of the wax microplatelets. Annealing at 40 °C could enhance mechanical stability of the coatings. The coatings are superhydrophobic with a water contact angle of 158.2° and a sliding angle of 7.3°. The coatings are resistant to intense water jetting and immersion in corrosive aqueous solutions. In addition, the coatings show excellent anti-adhesive properties for various liquid foods including cola, honey, milk and yoghourt. Moreover, the coatings are applicable onto different substrates (e.g., glass slide, PET plate and polyethylene plate) and could be prepared using different waxes (e.g., paraffin wax, beeswax and microcrystalline wax). We believe that the wax superhydrophobic coatings could find applications in various fields such as anti-adhesion of liquid foods, fruit preservation and anti-bioadhesion, etc.