Achieving Superhydrophobic Surfaces via Air-Assisted Electrospray

Effects of Carbon Templates in Tetraethyl Orthosilicate-Derived Superhydrophobic Coatings

Superhydrophobic coatings have garnered significant research interest due to their potential applications in areas such as ant-icing and windows. This study focuses on the development of superhydrophobic coatings using air-assisted electrospray and the effect of different carbon additives as templates in the coating. Carbon templates, with their unique topological varieties, offer a cost-effective alternative to other patterning technologies such as photolithography. By introducing dispersed carbon black, carbon nanotubes, and graphene additives in TEOS solution, silica is given the ability of localized secondary growth on or around the carbon surfaces as well as the building structure to provide adequate roughness on the substrate surface. The templated silica formations provide a thin coating with nano-scale roughness for heightened water resistance. As compared with the template-free coating that has small silica particles, a surface roughness of 135 nm, and a water contact angle (WCA) of 101.6° (non-superhydrophobic), the carbon templating effect allowed for increased silica particle size, a surface roughness as high as 845 nm, a WCA above 160°, and the ability to maintain superhydrophobicity over 30 abrasion cycles. The morphological characteristics that resulted from the templating effect correlate directly with heightened performance of the coatings. Herein, the carbon additives have been found to serve as cheap and effective templates for silica formation in thin TEOS-derived superhydrophobic coatings.

Bioinspired Under-Liquid Dual Superlyophobic Surface for On-Demand Oil/Water Separation

Porous membranes with under-liquid dual superlyophobic properties, which are difficult to achieve because of a thermodynamic contradiction, have attracted considerable interest in the field of switchable oil/water separation. Herein, a bioinspired mesh membrane with alternating hydrophilic and hydrophobic chemical patterns on its surface that endows it with superamphiphilic and under-liquid dual superlyophobic properties is fabricated by a simple liquidus modification process. The as-prepared membrane possesses a combination of under-oil superhydrophobic and under-water superoleophobic characteristics in the absence of external stimuli. Moreover, it can effectively perform the on-demand separation of various oil/water systems, including immiscible oil/water mixtures and oil/water emulsions owing to its under-liquid dual superlyophobic properties.

Eco-Friendly Fabrication of Transparent Superhydrophobic Coating with Excellent Mechanical Robustness, Chemical Stability, and Long-Term Outdoor Durability

Surfaces that possess both superhydrophobicity and high transparency at the same time recently have attracted extensive attention in outdoor applications. However, fabrication and application of transparent superhydrophobic coating usually face following challenges: the micro-nano hierarchical structure required for superhydrophobicity usually leads to a decrease in the light transmittance due to its light trapping effect; fluorine-containing materials used in the preparation of superhydrophobic surfaces are potentially harmful to humans and the environment; and the superhydrophobic surface is easily destroyed by external factors. In this work, a transparent superhydrophobic coating was fabricated via an inexpensive and eco-friendly two-step method, that is, dipping glass substrate into the polydimethylsiloxane/SiO₂ suspension followed by calcination treatment. The prepared coating showed superhydrophobicity with a water contact angle of 164° and a sliding angle less than 1.0°. In the visible light region with the wavelength range of 300-900 nm, the maximal transmittance of the superhydrophobic coating was ∼91.4%, which is higher than that of the untreated glass substrate (∼90.9%). Moreover, the coating can maintain superhydrophobicity and high transmittance after sandpaper abrasion, water flow impact, immersion in strong acid/alkaline solution, UV irradiation, and long-term outdoor exposure. We believing that the coating has huge potential value in outdoor applications.