New ultra-wetting film – liquid separation can be achieved, and the expression signals functional

Super wetting film interface due to their unique chemical interaction with the control liquid and become a hot topic. Wetting conventional single super-wetting film can not satisfy the complex requirements of practical application. Therefore, the researchers focused on the smart responsive super wetting film, it can easily respond to an external stimulus, such as temperature, power, humidity, gas, pH and light. Responsive research in recent years, super-wetting film aspect wettability successfully transition from one state to another state. However, such duality wetting transition suffered a \”black and white\” dilemma, thus severely limiting their functional diversity. Therefore, an urgent need for an integrated super-wetting material, it can break the \”black and white\” changes, and has multiple functions can be flexibly applied. 新型超润湿膜-可实现液体分离和信号表达功能 Recently, the Tsinghua University Professor Feng Linfu, Professor dangerous rock team known journal \”German Ohka\” having introduced the SiO2 / octadecylamine (ODA) in response to a patterned coating of the ultra-multifunctional Run The wet film. The coated portion of the film is displayed at different pH values ​​superhydrophobic properties (pH = 7) / ultra-hydrophilic (pH 13) shift portions remain uncoated ultra-hydrophilic, so that the film has change the wettability properties of the anisotropic / isotropic. The film may be used both as a response to osmotic membrane, it may be used as a signal expressed, capable of better separation efficiency (> 99.90%) and flux (~ 60 L / m2 · h) separation and permeate liquid, and real-time variable expression signals. By a coating method of the SiO2 / ODA coating film having an adjustable patterned prepared. To control the use of the precursor film pattern templates of different shapes. Hydrogen-step self-assembly strategy, utilizing hydrophobic fumed SiO2 and SiO2 synthesized ODA / ODA coating. SiO2 which provides ultra-low specific surface energy (SSE) to the coating hydrophobic, while the ODA rich amino group, the coating having a pH-responsive. The pH at 13, a high electron density of hydroxyl ions in combination with an amino group by hydrogen, the coating having a super-hydrophilicity. 7 pH =, amino electrically neutral, less polar, having a superhydrophobic coating.

新型超润湿膜-可实现液体分离和信号表达功能
Figure 1. Response of manufacturing and film. In template based on various shapes, film coating method were prepared. Hydrogen-step self-assembly of the coating was prepared. Since the produced film having an active amino group and an adjustable pattern, it exhibits anisotropy/ Isotropic transition wetting properties, thereby achieving functional diversity.

the uncoated portions of the film in air exhibits a water contact angle ~ 0 ° (the WCA), presented> 140 ° in four different organic liquid (toluene, n-hexane, ethyl acetate and diesel) underwater oil contact angle (OCA), indicating its super-hydrophilic / oleophobic properties underwater. Due to the low SiO2 and ODA brought SSE, superhydrophobic coating exhibits 0 ° OCA and 147 ° WCA in air. OCA and the WCA underwater oil were 18 ° and 163 °. When the pH is increased to 11 from 13, WCA sharp decline, from about 122.9 ° to 13.0 °, hydroxyl ions described hydrophilic than the hydrophobic region is an alkyl chain contribution contribution. When the pH from 3 to 1, also showed a similar decline from 134.3 ° down to 15.4 °, which determines the distribution of the critical point to another, wherein the proton contribution exceeds the contribution of the alkyl chain. Different wetting and bond coat uncoated portion may be achieved in response to a pH of between induced anisotropy and isotropy wettability, laid the foundation for the functional diversity.

新型超润湿膜-可实现液体分离和信号表达功能
Figure 2. Morphology and wetting behavior of the film. a) FESEM image uncoated portion; FESEM image b) coating portion; c) pH of the film produced in response characteristic; D) derived from a coating \”love THU\” pattern; E) uncoated portion WCA and underwater OCA; F WCA under WCA) coating portion, OCA, OCA and underwater oil; G) coated portions of water at different pH value of the contact angle. h) -k) the transition between isotropic and anisotropic Induced pH. SHL, super-hydrophilic. SHB, superhydrophobic.

pH = 7, the anisotropic film can be used as a non-permselective membrane. When pH 13, isotropic film can be used as a selective separation process water mixture. N-hexane containing a mixture of water, ethyl acetate, toluene and diesel, the separation efficiency of the membrane can be achieved 99.95% or more, and the filtrate containing oil lower than 200ppm. For toluene / water mixture was treated 10 times, still more than 99.90% efficiency, and the filtrate containing oil lower than 250ppm. Better reusability film, which may be the result of hydrogen bonding between the nylon substrate and ODA. Low SSELiquid permeation flux of ~ 60L / m2 · h, per ml of liquid permeable membranes require ~ 50s. High water permeation flux SSE significantly higher (~ 110L / m2 · h), corresponding to per ml of water permeability 30s. This is because some of the membrane pores are clogged SiO2 / ODA, thus reducing the effective pore radius, which could further affect the permeation flux. Permeable membrane also showed good performance is repeated, after 20 alternating flux remained almost unchanged.

新型超润湿膜-可实现液体分离和信号表达功能
Figure 3. The response permeable film obtained by the anisotropic / isotropic phase transition. a) When the pH 13, can be used as a selective membrane separation membrane; b) the separation efficiency of the oil content and a filtrate; c) a water separator reusability; d) pH = 7 when, as a non-permselective membrane may film; E) of the liquid flow through different membranes; F) reusability liquid penetration.

anisotropy / isotropy film also gives a good signal characteristic expression. After the conductive liquid membrane treatment, not wet the coated portion remains uncoated portion remains moist. The wet film portion connected to the power supply. When the coating portion is connected to the current is zero, it is connected to the uncoated part of the current of 0.01 A. LED \”1\” and \”0\” represent conductive and nonconductive. After the treatment liquid non-conductive, current is always kept at 0. Thus, expression of preliminarily verified signal properties of the film, may be used for real-time detection of conductive / non-conductive liquid. When the wire is moved between the coated portion and the uncoated portion, the current is switched between 0 and 0.01 A. Abstract model obtained based on the sector, the liquid film successfully processed signal represented as a binary sequence. The film is capable of expressing a binary sequence of \”1\” and \”0\” signal, indicating that the film has a high expression efficiency. Since the 2n n-bit binary sequence comprises different forms, this expression can greatly improve the efficiency of expression.

新型超润湿膜-可实现液体分离和信号表达功能
Figure 4. Expression of the signal anisotropic / isotropic transition obtained. a) the case of post-processing analog preprocessing conductive liquid; b) -c) and the LED current values ​​reflected signal; d) -f) binary sequence having a 90 ° fan-shaped pattern of the film is indicated; g) -h) binary expression other examples of film sequences; pH i) -k) LED array in response to the reflected signal changes.

Preparation of the policy in response to first-type patterned filmThe permeation and separation characteristics combined to achieve super-wetting film is expressed by the signal, it provides a new way to explore and adjustable multi-applications in a limited space wetting material over the working environment. The full text link: https: //onlinelibrary.wiley.com/doi/10.1002/anie.202005030

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