When a colloidal suspension droplet evaporates from a solid surface, it leaves a characteristic deposit in the contact region. These deposits are common and important for many applications in printing, coating, or washing. By using superamphiphobic surfaces as a substrate, the contact area can be reduced so that evaporation is almost radially symmetric. While drying, the droplets maintain a nearly perfect spherical shape. Here, we exploit this phenomenon to fabricate supraparticles from bidisperse colloidal aqueous suspensions. The supraparticles have a core-shell morphology. The outer region is predominantly occupied by small colloids forming a close-packed, crystalline structure. Towards the center, the number of large colloids increases and they are packed amorphously. The extent of this stratification decreases with decreasing the evaporation rate. Complementary simulations indicate that evaporation leads to a local increase in density, which in turn exerts stronger inward forces on the larger colloids. Comparison between experiments and simulations suggest that hydrodynamic interactions between the suspended colloids reduce the extent of stratification. Our findings are relevant for the fabrication of supraparticles for applications in the fields of chromatography, catalysis, drug delivery, photonics, and a better understanding of spray drying.

Supraparticles consisting of nano- or microparticles have potential applications as e.g., photonic crystals, drug carriers, or heterogeneous catalysts. To avoid the use of solvent or processing liquid one can make supraparticles by evaporating droplets of aqueous suspensions from super-liquid-repellent surfaces. Herein, a method to adjust the porosity of supraparticles is described; a high porosity is desired, e.g., in catalysis. To prepare highly porous TiO2 supraparticles, polymer nanoparticles are co-dispersed in the suspension. Supraparticles are formed through evaporation of aqueous suspension droplets on superamphiphobic surfaces followed by calcination of the sacrificial polymer particles. The increase of porosity of up to 92%, resulted in enhanced photocatalytic activity while maintaining sufficient mechanical stability.

Superhydrophobic surfaces have already been applied in anti‐fouling, water‐oil separation, liquid transportation, etc. Surfaces can be defined as superhydrophobic surfaces once they can support a water droplet with its spherical shape maintained and accompanied by an apparent contact angle larger than 150° and a rolling‐off angle below 10°. Such water repellent property is achieved by the synergetic action of hierarchical structures and the low‐surface energy of the substances constructing the surface. Structures with high aspect ratio always perform good superhydrophobicity. However, they are usually with poor mechanical stability. Since durability is one of the essential factors for practical use, exploiting robust superhydrophobic surfaces has attracted tremendous interest. During the past decade, great effort has been made in developing self‐healing superhydrophobic surfaces to improve the potential practice and broaden the application fields. An overview of the recent development of self‐healing superhydrophobic surfaces is provided in this review. The focus here is particularly on the fabrication process based on specific healing mechanisms and possible applications. Finally, an outlook on future fabrication techniques for durable superhydrophobic surfaces is presented.

This paper presents a facile method to fabricate bioinspired polyethylene terephthalate (PET) nanocone arrays via colloidal lithography. The aspect ratio (AR) of the nanocones can be finely modulated ranging from 1 to 6 by regulating the etching time. The samples with the AR value of 6 can present underwater superoleophobicity with the underwater oil contact angle (OCA) of 171.8°. The as-prepared PET nanocone arrays perform anti-bioadhesion behavior, which inhibits the formation of the actin cytoskeleton when it used as the substrate for cell culture. Moreover, the oil wettability is temperature controlled after modifying the PET nanocone arrays with PNIPAAm film, and the oil wettability of the functionalized nanocone arrays can be transformed from the superoleophobic state with OCA about 151° to the oleophilic state with OCA about 25° reversibly. Due to the high-throughput, parallel fabrication and cost-efficiency of this method, it will be favourable for researchers to introduce oleophobic properties to various substrate and device surfaces. Due to the superoleophobicity and simple functionalizing properties, the PET nanocone arrays are very promising surfaces for anti-adhesion, self-cleaning and have potential applications in material, medical, and biological fields.