Multifunctional superhydrophobic surfaces

Fabrication of Dual Self-Healing Multifunctional Coating Based on Multicompartment Microcapsules

By designing and preparing multifunctional materials exhibiting self-healing ability, problems related to their durability outdoors can be solved. This study, inspired by the self-healing mechanism of natural creatures, successfully prepared a dual self-healing multifunctional coating using temperature stimuli-responsive multicompartment microcapsules. Phase change materials (PCMs) were employed to load multicompartment microcapsules that were produced through Pickering emulsion polymerization by applying hydrophobic materials encapsulated by titanium dioxide (TiO₂) nanocapsules as Pickering emulsifiers. The multifunctional coating produced using microcapsules and self-healing waterborne polyurethane (WPU) exhibited thermal insulation and antireflection properties, which was attributed to the application of PCMs and TiO₂, and it also achieved remarkable superhydrophobicity. Moreover, this coating exhibited the intrinsic and superficial dual self-healing ability, which was attributed to the release of hydrophobic materials from microcapsules and the self-healing ability of WPU. This study can be referenced to guide the fabrication of high-performance self-healing materials, and it can contribute to the long-term use of multifunctional coatings.

Regulating Droplet Wetting and Pinning Behaviors on Pathogen-Modified Hydrophobic Surfaces: Strategies and Working Mechanisms

Hydrophobic surfaces modified by pathogens in agricultural production are one of the main reasons to reduce the utilization of pesticides. Adding surfactants to pesticide solutions is a common method to improve their wetting and spreading properties. In this work, the interaction mechanism between pathogen-modified hydrophobic surfaces and mixtures of surfactants and a pesticide was studied in detail. The interaction mechanism was determined by characterizing the wetting and spreading behaviors of droplets on cucumber powdery mildew leaves at different growth stages. When surfactants were added, droplets on cucumber powdery mildew leaves were in the Wenzel wetting state, the pinning force weakened, the contact line speed accelerated, and the adhesion force increased. We explained the micellar state and aggregation behavior of surfactant molecules in a pesticide solution that was applied to the surface of cucumber powdery mildew leaves. Droplets of solutions containing nonionic surfactants easily formed semibald micelles, binding to the pathogen of powdery mildew, whereas droplets containing cationic surfactants did not do so. Because of the electrostatic interaction between cationic surfactant molecules and powdery mildew pathogens, cationic surfactant molecules did not wet the pathogens very well, so we suggest adding nonionic surfactants rather than cationic surfactants to improve the wetting and spreading of pesticide solutions on cucumber powdery mildew leaves. This study provides new insights into enhancing the wetting and deposition of droplets on pathogen-modified hydrophobic surfaces.