Zhaozhu Zhang

Robust and Durable Superhydrophobic Cotton Fabrics for Oil/Water Separation

By introducing the incorporation of polyaniline and fluorinated alkyl silane to the cotton fabric via a facile vapor phase deposition process, the fabric surface possessed superhydrophobicity with the water contact angle of 156° and superoleophilicity with the oil contact angle of 0°. The as-prepared fabric can be applied as effective materials for the separation of water and oil mixture with separation efficiency as high as 97.8%. Compared with other materials for oil/water separation, the reported process was simple, time-saving, and repeatable for at least 30 times. Moreover, the obtained fabric kept stable superhydrophobicity and high separation efficiency under extreme environment conditions of high temperature, high humidity, strong acidic or alkaline solutions, and mechanical forces. Therefore, this reported fabric has the advantages of scalable fabrication, high separation efficiency, stable recyclability, and excellent durability, exhibiting the strong potential for industrial production.

Superhydrophilic–superoleophobic coatings

A novel superhydrophilic and superoleophobic nanocomposite coating is fabricated by spray casting nanoparticle–polymer suspensions on various substrates. Water droplets can spread over the coating completely; meanwhile, oil droplets can roll off the coating at low tilt angles without any penetration. Besides overcoming oil-fouling problems for the hydrophilic coating, the superhydrophilic–superoleophobic coating applied to the stainless steel mesh can be used for the separation of oil and water.

Robust superhydrophobic surfaces with mechanical durability and easy repairability

Development of superhydrophobic self-cleaning materials is hindered by their susceptibility to mechanical abrasion. Here, to solve the problem caused by mechanical damage, we prepared a superhydrophobic metal/polymer composite surface possessing both mechanical durability and easy repairability. The mechanical durability of the resulting superhydrophobic surface was evaluated by the abrasion test. The result demonstrated that the rough surface textures were retained and the surface still exhibited superhydrophobicity after mechanical abrasion. Moreover, the non-wetting property can be restored by an easy regeneration process when loss of superhydrophobicity occurs. Amazingly, the created metal/polymer surface can be used as a finger touchable self-cleaning surface.

Facile fabrication of a superamphiphobic surface on the copper substrate.

A simple solution-immersion technique was developed for the fabrication of a superamphiphobic surface on the copper sheet. Hierarchical structure composed of nanorod arrays and microflowers was formed on the copper surface by an alkali assistant oxidation process; after fluorination, the surface became super-repellent toward water and several organic liquids possessing much lower surface tension than that of water, such as hexadecane. Such superamphiphobicity is attributed to the synergistic effect of their special surface chemicals and microscopic structures, which allows for the formation of a composite interface with all probing liquids tested. We also discuss the effects of surface chemical constituent and geometrical structure on hydrophobicity and oleophobicity; such information allows us to engineer surfaces with specific oleophobic behavior. Additionally, the stability of the composite interface on the created superamphiphobic surface is studied by the compression and immersion test.

A simple approach to fabricate superoleophobic coatings

We describe a simple method to synthesize copper perfluorooctanoate and fabricate superoleophobic coatings by spraying a copper perfluorooctanoate suspension onto substrates. The re-entrant morphology and high perfluorinated carbon content provide the needed texture and low surface energy to enable the formation of a composite solid–liquid–air interface with low surface tension liquids. Liquid repellency of the fabricated coating is demonstrated by visible experiment results and contact angle measurements. The robustness of the superoleophobicity is investigated by a compression experiment, which shows that the composite interface can maintain its stability against a pressure difference across the interface. The superoleophobic coating can be applied to various surfaces without limitations of size and shape. More importantly, the coatings are easily repaired after being mechanically damaged because of their simple fabrication method.

Reversible superhydrophobicity to superhydrophilicity switching of a carbon nanotube film via alternation of UV irradiation and dark storage.

We describe a simple method of fabricating a superhydrophobic carbon nanotube (CNT) film without any chemical modification. A remarkable surface wettability transition between superhydrophobicity and superhydrophilicity can be easily observed by the alternation of UV irradiation and dark storage. The adsorption and desorption of surface water molecules on the CNT surfaces account for their tunable surface wettability, which is disclosed by X-ray photoelectron spectroscopy analysis. We also perform a series of comparison experiments to confirm the explanation of its distinctive surface wettability. This switchable wettability on the CNT film could have potential applications in areas requiring multifunctional CNT-based films.

Facile fabrication of a superhydrophobic fabric with mechanical stability and easy-repairability

The poor mechanical stability of superhydrophobic fabrics severely hindered their use in practical applications. Herein, to address this problem, we fabricated a superhydrophobic fabric with both mechanical stability and easy-repairability by a simple method. The mechanical durability of the obtained superhydrophobic fabric was evaluated by finger touching and abrasion with sandpaper. The results show that rough surface textures of the fabric were retained, and the fabric surface still exhibited superhydrophobicity after tests. More importantly, when the fabric lost its superhydrophobicity after a long-time abrasion, it can be easily rendered with superhydrophobicity once more by a regeneration process.

Rapid formation of superhydrophobic surfaces with fast response wettability transition.

We have developed a facile and time-saving method to prepare superhydrophobic surfaces on copper sheets. Various surface textures composed of Cu(OH)2 nanorod arrays and CuO microflowers/Cu(OH)2 nanorod arrays hierarchical structure were prepared by a simple solution-immersion process. After chemical modification with stearic acid, the wettability of the as-prepared surfaces was changed from superhydrophilicity to superhydrophobicity. The shortest processing time for fabricating a superhydrophobic surface was 1.5 min. Interestingly, the rapid wettability transition between superhydrophobicity and superhydrophilicity can be realized on the prepared surfaces with ease by the alternation of air-plasma treatment and stearic acid coating. It took just 2 min to complete the whole wettability transition. Additionally, the regeneration of the superhydrophobic surface is also considered regarding its application.

A novel superhydrophobic bulk material

To solve the mechanical damage and oil fouling problems, a novel superhydrophobic bulk material was fabricated by a simple approach. The superhydrophobic property of the resulting bulk material was retained after 20 abrasion cycles and even after cutting deep into it. The bulk material can thermally regenerate its superhydrophobicity for repeated use when fouled by oil. Exploiting this materials superhydrophobicity and thermal stability, the strongly oleophilic bulk material is demonstrated as a reusable oil sorbent scaffold in water.

Superoleophobic textured aluminum surfaces

With the aim of creating superoleophobic surfaces on engineering materials and understanding the influences of surface structures on the oleophobicity, we develop a convenient route to achieve superoleophobic surfaces on aluminum substrates using simple etching and surface fluorination. The liquid repellency of the textured surface is demonstrated by visible experimental results and contact angle measurements. Etching conditions, such as the etching time and etching procedure, play critical roles in establishing the oleophobicity. The micrometre-scale structures are essential for achieving the composite interface with low surface tension liquids, and the nanoscale structures formed in the treatment with boiling water lead to a decrease of contact angle hysteresis, bringing about an enhancement of superoleophobicity.