Shouping Xu

Inspired by Stenocara Beetles: From Water Collection to High-Efficiency Water-in-Oil Emulsion Separation

Inspired by the water-collecting mechanism of the Stenocara beetles back structure, we prepared a superhydrophilic bumps-superhydrophobic/superoleophilic stainless steel mesh (SBS-SSM) filter via a facile and environmentally friendly method. Specifically, hydrophilic silica microparticles are assembled on the as-cleaned stainless steel mesh surface, followed by further spin-coating with a fluoropolymer/SiO2 nanoparticle solution. On the special surface of SBS-SSM, attributed to the steep surface energy gradient, the superhydrophilic bumps (hydrophilic silica microparticles) are able to capture emulsified water droplets and collect water from the emulsion even when their size is smaller than the pore size of the stainless steel mesh. The oil portion of the water-in-oil emulsion therefore permeates through pores of the superhydrophobic/superoleophilic mesh coating freely and gets purified. We demonstrated an oil recovery purity up to 99.95 wt % for surfactant-stabilized water-in-oil emulsions on the biomimetic SBS-SSM filter, which is superior to that of the traditional superhydrophobic/superoleophilic stainless steel mesh (S-SSM) filter lacking the superhydrophilic bump structure. Together with a facile and environmentally friendly coating strategy, this tool shows great application potential for water-in-oil emulsion separation and oil purification.

Droplet Motion on a Shape Gradient Surface

We demonstrate a facile method to induce water droplet motion on an wedge-shaped superhydrophobic copper surface combining with a poly(dimethylsiloxane) (PDMS) oil layer on it. The unbalanced interfacial tension from the shape gradient offers the actuating force. The superhydrophobicity critically eliminates the droplet contact line pinning and the slippery PDMS oil layer lubricates the droplet motion, which makes the droplet move easily. The maximum velocity and furthest position of droplet motion were recorded and found to be influenced by the gradient angle. The mechanism of droplet motion on the shape gradient surface is systematically discussed, and the theoretical model analysis is well matched with the experimental results.

Surface modification of light hollow polymer microspheres and its application in external wall thermal insulation coatings

Purpose – The purpose of this paper is to modify light hollow polymer microsphere (LHPM) with titanium dioxide nanoparticles (nano-TiO2) to improve its compatibility with latex and apply the obtained nano-TiO2/LHPM composite particles in external wall thermal insulation coatings. Design/methodology/approach – The nano-TiO2/LHPM composite particles were prepared via vigorous stirring. The morphology and chemical composition of the produced nano-TiO2/LHPM composite particles were characterized using scanning electron microscopy, energy dispersion spectrum, thermo-gravimetric analyzer and Fourier transform infrared. The performance of this new composite coating was evaluated by checking its stability, density, radiation reflectivity, thermal conductivity and the resulting insulation temperature difference when forming coating film. Findings – It was found that a 9:1 mass ratio of nano-TiO2/LHPM with total 10 weight per cent composite particles in the thermal insulation paint showed low density, good stabilit...

Superhydrophobic–superoleophilic stainless steel meshes by spray-coating of a POSS hybrid acrylic polymer for oil–water separation

Superhydrophobic–superoleophilic meshes with hierarchical structures were fabricated by spraying a POSS hybrid acrylic polymer on stainless steel mesh for oil–water separation in this paper. Fourier transform infrared spectroscopy, nuclear magnetic resonance (1H NMR), and thermogravimetric analyses were used to verify the chemical composition and thermostability of the POSS hybrid acrylic polymer, which was synthesized via a free radical solution polymerization. The obtained mesh was characterized by scanning electron microscopy, X-ray photoelectron spectroscopy, and optical contact angle meter to confirm the morphology, composition, and wettability of the film surface. The coated mesh, with a static water contact angle of 153° and a sliding angle of 4.5°, was applied to separate a series of oil–water mixtures, such as n-hexane, isooctane, petroleum ether, kerosene, and vegetable oil, with separation efficiency nearly 99%. In addition, the coated mesh still kept separation efficiency approximately 99% even after 25 separation cycles for n-hexane/water mixture. After 20 abrasion cycles, the water contact angle of the mesh remained 145°, and separation efficiency for n-hexane/water mixture is approximately 99%, indicating the coated mesh possessed good mechanical stability. The as-prepared mesh will be a promising material in oil–water separation, due to the simple, low-cost, and easily scalable fabrication method and the excellent separation performance in radical oil–water separation.

Polymer-infiltrated approach to produce robust and easy repairable superhydrophobic mesh for high-efficiency oil/water separation

A superhydrophobic and superoleophilic polymer-infiltrated nanoparticle film-coated stainless-steel mesh (PINF-SSM) was prepared with a novel and facile nature-inspired approach. The approach involves the use of low-cost raw materials and simple spray coating of hydrophobic silica nanoparticles onto stainless-steel mesh (SSM) surface. With acrylic resin pre-coating layer on both surfaces, it is conveniently transformed into an integrated polymer-infiltrated nanoparticle film on SSM after annealing above the resin’s glass transition temperature. The obtained PINF-SSM shows robust superhydrophobicity after multiple cycles rubbing with sandpaper, long-term UV irradiation, long-term storage, and exposure to strong acidic, alkaline, and saline solutions. The as-prepared PINF-SSM was successfully used to separate various oil/water mixtures with high-efficiency for at least 50 cycles and collect oil slick on water surface efficiently. Sequential coating thermoplastic acrylic resin and hydrophobic silica nanoparticles on the surface of SSM allow for extended storage time of the coating materials, easy resin processing with high silica content, quick repairing, and easy recovery of the superhydrophobic surface, making it suitable in various oil/water separation practices.

Synthesis and properties of the antibacterial hydrogels with enhanced mechanical strengths

A series of cationic poly(hydroxyethyl methacrylate)-g-poly(carboxybetaine methacrylate ester) (PHEMA-g-PCBMAE) hydrogels (HCGs) were synthesized by reversible addition-fragmentation chain transfer (RAFT) polymerization. The HCGs were characterized by Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and swelling behaviors. It was found that the HCG hydrogels showed enhanced mechanical strengths compared with PCBMAE hydrogel. In addition, it was observed that the cationic HCGs exhibited excellent antibacterial properties. We found that the equilibrium swelling ratios, mechanical properties, and drug release behaviors were related to the feed ratios of the gels. The tetracycline hydrochloride (TCHC) release results indicated that the drug released from HCGs could be prolonged by increasing the content of hydroxyethyl methacrylate (HEMA) in the gel networks.