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Switchable surface-active colloid particles are critical to the preparation of switchable Pickering emulsions, which are widely involved in multitudinous fundamental and practical fields, such as biomedical, food products, and spinning cosmetics. The stability of switchable surface-active particles relies on the full understanding of interaction forces between individual colloid particles quantitatively. In this work, a dual-laser optical tweezers instrument was applied to measure the interaction forces between silica particles coated with a common cationic surfactant (cetyltrimethylammonium bromide, CTAB) in water, and all of the measured forces can be well fitted with the theoretical model derived from the Derjaguin–Landau–Verwey–Overbeek (DLVO) theory. It was revealed that the minimum surface distance to engender the interaction forces between silica particles was closer progressively with the increase of CTAB concentrations, suggesting that the introduction of CTAB molecules in the solution thinned the electric double layer. In addition, the minimum surface distance between surface-inactive silica particles further decreased compared to surface-active states, although the ζ-potential has returned to the initial value of bare silica in pure water when the molecular ratio of 1:1 anionic surfactant (sodium dodecyl sulfate, SDS) was added into the solution to switch the surface-active silica particles to surface-inactive states. Our results provide a considerate methodology for quantifying the interaction forces and investigating the switchable behaviors of CTAB molecules from the adsorption to desorption at the particle–water interfaces, which provide vital foresights into the stabilization mechanism of switchable surface-active colloid particles and the further development of switchable Pickering emulsions.

Passive daytime radiative cooling (PDRC) is an energy-saving technology without an additional energy supply or environmental pollution. At present, most PDRC coatings for buildings are only aiming at high solar reflectivity (RS) and high mid-infrared emissivity (EMIR) while ignoring practicalities such as adhesion strength, scalability, and durability. In this work, modified calcined kaolin/(ethylene trifluorochloroethylene copolymer-polydimethylsiloxane) (MK/(FEVE–PDMS)) coating with super practicability is prepared by using MK as a filler, FEVE as an adhesive, and PDMS as a hydrophobic modifier. The RSand EMIRof the coating are 92.5 and 94.6%, respectively. The MK/(FEVE–PDMS) coating exhibits superhydrophobicity, with an advancing contact angle (ACA) of 160.2° and a hysteresis contact angle of 7.3°. At an average solar irradiance of 742.78 W m–2, the coating achieved a temperature drop of 13.12 °C (shielded with PE film) and 3.09 °C (without shielding), respectively, relative to the environment. The coating adheres firmly to the substrate with an adhesion strength of class 2. The superhydrophobicity of the coating provides excellent durability and ease of repair, which can resist UV aging and mechanical damage. The durable superhydrophobicity gives the coating long-term stability in PDRC performance. Additionally, the cheap raw materials and the preparation process, consistent with the production of existing paints, show excellent scalability. Moreover, the energy consumption simulation results show that the energy saving ratio of the coating is more than 10% in the densely populated Yangtze River Delta and Pearl River Delta. The durable self-cleaning radiative coating developed in this work has potential application prospects in areas where the demand for cooling in summer is large and the demand for heating in winter is small.

Superhydrophobic surfaces were unexpectedly constructed by immersing a variety of substrates (aluminum sheet, melamine sponge, cotton fabric, and wood) into an aqueous solution containing tea polyphenols and metal ions (Fe2+, Ag+, Ce3+) and the potential applications in corrosion resistance for superhydrophobic aluminum, water absorption resistance for superhydrophobic wood, oil/water separation for superhydrophobic sponge and self-cleaning for superhydrophobic fabric were investigated.Superhydrophobic surfaces were unexpectedly constructed by immersing substrates into an aqueous solution containing tea polyphenols (TP) and metal ions. Metal ions were chelated with TP to generate rough surface structures and reduced to metal particles, which were active to anchor the carbon contamination from the atmosphere. Superhydrophobicity was unexpectedly achieved by the joint effect of surface roughness and surface carbon contamination.

In the present study, a simple and cost-effective method for the preparation of a superhydrophobic calcium aluminate cement (SCAC) with superstable mechanical stability is reported. Room-temperature vulcanized silicone rubber (RTV) is used as an internal hydrophobic additive in concrete. The as-prepared cement surface and all cross-sections exhibit superhydrophobicity. The mechanical stability of the superhydrophobic-cement sample was evaluated by multiple severe mechanical damages. The SCAC sample exhibits super mechanical stability against sandpaper abrasion under high pressure, long-time impinging with sand, repeated knife scratches, and electric-cutter cutting. Amazingly, the cement sample was ground into powder, which was also superhydrophobic. In addition, the SCAC sample shows improved corrosion resistance for rebar against Cl–in comparison with the superhydrophilic-cement sample. Moreover, the application of superhydrophobic cement can be extended to oil–water separation using SCAC powder combined with an adhesive.

Traditional oil/water separation materials were prepared with partial or all nonrenewable raw materials, which would not only increase resource consumption but also cause new environmental pollution after being abandoned. In this work, a superhydrophobic and superoleophilic oil/water separation all-natural material was prepared using a simple and fast emulsion immersing method. The raw materials used including natural sponges and natural vegetable waxes, all of which are renewable. The as-prepared all-natural material can not only absorb various oils from water with high oil absorption capacity, fast oil absorption rate, and good recyclability but also achieve reuse of the absorbed oil by squeezing. In addition, the as-prepared all-natural material exhibits strong stability against cyclic compression, excellent resistance to corrosive aqueous solutions contacting, and organic solvents immersing. Furthermore, the surface wax coating can be easily recycled. This work provides a new method to prepare oil/water separation materials by using all-natural and renewable raw materials.

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In the present work, a polytetrafluoroethylene/polydimethylsiloxane (PTFE/PDMS) composite coating was fabricated using a simple brushing method. The PTFE/PDMS coating has both superhydrophobic self-cleaning property and radiation cooling function. The contact angle (CA) for water of the composite coating is 159.3°, and the sliding angle (SA) for water is 6.3°. Furthermore, the solar reflectivity of the coating in the wavelength range of 200–2500 nm is close to 92%, and the infrared emissivity in the 8–13 μm middle-infrared band is about 0.93. When the maximum daytime temperature in summer is 39 °C, the PTFE/PDMS coating could achieve an average radiation cooling temperature of 4.73 °C under direct sunlight from 10:00 a.m. to 16:00 p.m. Under the same conditions, covering the PTFE/PDMS coating on the electric vehicle seat cushion could realize the temperature drop of the seat cushion by 19.41 °C. After continuous washing and corrosion of 50,000 mL of simulated acid rain, 10 cycles of ultraviolet (UV) aging experiments, or 25 cycles of sandpaper abrasion, the superhydrophobicity and radiation cooling function of the PTFE/PDMS coating remained unchanged. In particular, the PTFE/PDMS coating lost the radiative cooling ability after the surface is contaminated. However, with the help of natural rainfall, its radiation cooling coating could recover rapidly. Therefore, the PTFE/PDMS coating developed in this work makes the radiative cooling coating more practical.

We present a facile one-step method to fabricate superhydrophobic Ag surface by electrodeposition without using any low surface energy reagent. The water contact angle of the prepared surface is 167.1° and the sliding angle is only 0.5° after heat treatment. It is demonstrated by the field emission scanning electron microscopy (FESEM), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) analyses that the dendrites of rough micro-nanostructure combined with the spontaneously adsorbed hydrocarbon make the surface exhibit superhydrophobicity. However, the superhydrophobic Ag surface becomes superhydrophilic when the surface is irradiated by UV light for several hours. It recovers superhydrophobicity after further heat treatment and can successfully implement the reversible wettability transition between superhydrophobicity and superhydrophilicity for several cycles. 本文采用简单的电沉积法制备出无需低表面能试剂修饰的超疏水银表面. 镀银表面经过热处理后与水滴的接触角达到167.1°而滚动角仅为0.5°. 通过FESEM, XRD以及XPS分析表明, 制备的微米/纳米级粗糙结构的银表面吸附了空气中的碳氢化合物导致表面具有超疏水性. 当用紫外光照射表面几个小时后, 表面会从超疏水性转变为超亲水性. 然而, 热处理后表面又恢复超疏水性能. 重复紫外光照射和热处理过程, 镀银表面可以实现超疏水和超亲水之间的多次转换.

This paper focused on the sessile droplet freezing and ice adhesion on aluminum with different wettability (hydrophilic, common hydrophobic, and superhydrophobic surfaces, coded as HIS, CHS, SHS, respectively) over a surface temperature range of −9°C to −19°C. It was found that SHS could retard the sessile droplet freezing and lower the ice adhesion probably due to the interfacial air pockets (IAPs) on water/SHS interface. However, as surface temperature decreasing, some IAPs were squeezed out and such freezing retarding and adhesion lowering effect for SHS was reduced greatly. For a surface temperature of −19°C, ice adhesion on SHS was even greater than that on CHS. To discover the reason for the squeezing out of IAPs, forces applied to the suspended water on IAPs were analyzed and it was found that the stability of IAPs was associated with surface micro-structures and surface temperature. These findings might be helpful to designing of SHS with good anti-icing properties.

We develop a simple strategy for the collection of oil spill using a miniature device. The device was enfolded from a sheet of copper mesh with surface superhydrophobicity and superoleophilicity. The copper mesh was fabricated through a simple thermal oxidation and surface modification process. The miniature device adsorbed various oils from the surface of oil–water mixture in its pores while repelling water completely. After the pores were full of oil, only oil could infiltrate into the device through the pores automatically and was finally concentrated into the device, showing its oil–water separating ability. Importantly, the concentrated oil in the device could be taken away by a dropper or pumped out, thus achieving the collection of oil for reuse. Additionally, after the concentrated oil was taken away, the device could be used in the next oil–water separating cycle without apparent decrease of its separation ability. Therefore, the findings in this work may offer a new strategy for the collection and reuse of various kinds of oils and other organic compounds from water surfaces.

A simple and universal one-step process bas been developed to render light alloys (including AZ91D Mg alloy, 5083 Al alloy, and TC4 Ti alloy) superhydrophobic by immersing the substrates in a solution containing low-surface-energy molecules of 1H,1H,2H,2H-perfluorooctyltrichlorosilane (PFOTS, 20 μL), ethanol (10 mL), and H2O (10 mL for Al and Mg alloy)/H2O2(15%, 10 mL for Ti alloy). Field-emission scanning electron microscopy, X-ray photoelectron spectroscopy, and water contact angle measurements have been performed to characterize the morphological features, chemical composition, and wettability of the surfaces, respectively. The results indicate that the treated light alloys are rough-structured and covered by PFOTS molecules; consequently, the surfaces show static contact angles higher than 150° and sliding angles lower than 10°. This research reveals that it is feasible to fabricate superhydrophobic surfaces (SHS) easily and effectively without involving the traditional two-step processes. Moreover, this one-step process may find potential application in the field of industrial preparation of SHS because of its simplicity and universality.

We report a convenient route to fabricate superoleophobic surfaces (abridged as SOS) on copper substrate by combining a two-step surface texturing process (first, the substrate is immersed in an aqueous solution of HNO3and cetyltrimethyl ammonium bromide, and then in an aqueous solution of NaOH and (NH4)2S2O8) and succeeding surface fluorination with 1H,1H,2H,2H-perfluorodecanethiol (PFDT) or 1-decanethiol. The surface morphologies and compositions were characterized by field emission scanning electron microscopy and X-ray diffraction, respectively. The results showed that spherical micro-pits (SMP) with diameter of 50–100 μm were formed in the first step of surface texturing; in the second step, Cu(OH)2or/and CuO with structures of nanorods/microflowers/microballs were formed thereon. The surface wettability was further assessed by optical contact angle meter by using water (surface tension of 72.1 mN m–1at 20°C), rapeseed oil (35.7 mN m–1at 20°C), and hexadecane (25.7 mN m–1at 20°C) as probe liquids. The results showed that, as the surface tension decreasing, stricter choosing of surface structures and surface chemistry are required to obtain SOS. Specifically, for hexadecane, which records the lowest surface tension, the ideal surface structures are a combination of densely distributed SMP and nanorods, and the surface chemistry should be tuned by grafted with low-surface-energy molecules of PFDT. Moreover, the stability of the so-fabricated sample was tested and the results showed that, under the testing conditions, superhydrophobicity and superoleophobicity may be deteriorated after wear/humidity resistance test. Such deterioration may be due to the loss of outermost PFDT layer or/and the destruction of the above-mentioned ideal surface structures. For UV and oxidation resistance, the sample remained stable for a period of 10 days.

After hydrothermally treated in H2O (for Mg alloy and Al alloy) or H2O2(for Ti alloy), microstructured oxide or hydroxide layers were formed on light alloy substrates, which further served as the active layers to boost the self-assembling of 1H,1H,2H,2H-perfluorooctyltriethoxysilane (PFOTES) and finally endowed the substrates with unique wettability, that is, superhydrophobicity. For convenience, the so-fabricated superhyrdophobic surfaces (SHS) were abridged as HT-SHS. For comparison, SHS coded as CE-SHS were also prepared based on chemical etching in acid and succedent surface passivation with PFOTES. To reveal the corrosion protection of these SHS, potentiodynamic polarization measurements in NaCl solution (3.5 wt %) were performed. Moreover, to reflect the long-term stability of these SHS, SHS samples were immersed into NaCl solution and the surface wettability was monitored. Experimental results indicated that HT-SHS was much more stable and effective in corrosion protection as compared with CE-SHS. The enhancement was most likely due to the hydrothermally generated oxide layer by the following tow aspects: on one hand, oxide layer itself can lower the corrosion due to its barrier effect; on the other hand, stronger interfacial bonding is expected between oxide layer and PFOTES molecules.

Tunable water adhesion with high static contact angle (SCA) on titanium oxide surfaces was achieved by a two-step process: first, titanium oxide surfaces with different structures were obtained by immersion the titanium alloy substrates into H2O–H2O2–HF solution at 140 °C for different time of 30, 60, and 120 min; then, low-surface-energy molecules of 1H, 1H, 2H, 2H-perfluorooctyltrichlorosilane (PFOTS) were deposited thereon. SCA for all so-fabricated samples were higher than 150° and sliding angle (SA) for different immersion time of 30 min, 60 min, and 120 min is 180o, 31±2o, and 8±1o, respectively. To analyze the correlation between the surface structures and the dynamic wetting behaviors, we adopted, three contact modes (i.e., Wenzel, Cassie impregnating, and Cassie modes). The analyses showed that the surface adhesion was influenced greatly by water/solid interfacial interaction and could be artificially tuned between Wenzel state with high adhesion to Cassie state with low adhesion through the design of appropriate microstructures.

CaCu3Ti4O12–polyethersulfone CCTO–PES composites with various CCTO volume fractions up to 0.5 were prepared. Relatively high dielectric constant   32.7 and low loss tan δ  0.063 of the composites with CCTO volume fraction at 0.5 were observed. Various theoretical models were employed to predict the dielectric constant of these composites, the dielectric constant obtained via EMT model were in close agreement with the experimental data. The dielectric constant of CCTO–PES composites showed weak frequency dependence at the measuring frequency range, and the loss tangent apparently decrease with increase in frequency. Both the dielectric constant and loss tangent showed weak temperature dependence at low temperature range from 20 to 60 °C, however, they increased dramatically with a further increase in temperature above 60 °C.

Polydopamine (PDA) bearing surface catechol groups on a silicon wafer was used to induce the deposition of thin TiO2films from aqueous solution. Different deposition conditions, such as the concentration and pH of precursor solution as well as the deposition temperature, were adopted. It was found that the growth rate and crystalline phase can be controlled by these deposition parameters; moreover, the crystal growth and adhesion strength to the substrate of TiO2film can be promoted by PDA layer.