Ultrasonic atomization based fabrication of bio-inspired micro-nano-binary particles for superhydrophobic composite coatings with lotus/petal effect

Abstract

To mimic a superhydrophobic surface as found in nature, micro-nano binary surface structures with specific chemical properties are required. This type of special binary structure was usually realized by introduction of hierarchical inorganic microparticles; however, existing preparation methods are usually complex and difficult for scalable manufacture. In order to solve this problem, a facile ultrasonic atomization-based spray drying method has been developed in the present study for producing hierarchical silica microparticles for eventual fabrication of superhydrophobic coatings with either a lotus or petal effect depending on the required application. 3-aminopropyl-triethoxysilane (APTES) was used as a modifier for enhancing the binding between the silica nanoparticles. The hierarchical silica microparticles exhibited an diameter of around 10 μm and proper nano-roughness to realize a superhydrophobic effect. The prepared hierarchical silica microparticles/epoxy coating achieved a very high water contact angle up to 161° and a sliding angle as low as 5°. Both lotus and petal effects were achieved. Mechanical properties of the composite coating have also been enhanced by virtue of the modifiers. The interactions between –NH2 groups from the APTES modifier and –OH groups from the silica led to a strong adhesive force with water molecules, while the introduction –F groups to the silica could reduce this affinity and result in a smaller sliding angle.