Degradable Superhydrophobic Coatings Using the Solid–Liquid Transition of a Multilayer Structure near Body Temperature

Human- and eco-friendly edible superhydrophobic coatings are orally ingestible and serve as transient protection for drug delivery systems and edible electronic devices. However, they melt far above body temperature, which limits their degradability within the body. In this study, we developed a superhydrophobic coating made of food materials whose wettability changes at approximately body temperature. This coating has a three-layer structure consisting of a beeswax hydrophobic layer, a solidified oil layer with a melting point near body temperature, and a beeswax superhydrophobic layer. Although beeswax does not melt under 60 °C and maintains its structure in the body, the use of intermediate oils leads to the coating losing its superhydrophobicity as the oil layer changes from solid to liquid near body temperature. By designing the liquid–solid transition of the multilayer structure, we provide criteria for changing the wettability even at temperatures at which superhydrophobicity would not normally be lost.