Industrial membranes comprised of a thin selective layer (<100 nm) requires a gutter layer (<100 nm) between the selective layer and the porous support to achieve high permeance for gas separation. The gutter layer materials must be carefully chosen to enhance overall membrane performance, i.e., high permeance and high selectivity. However, the experimental determination of the optimum gutter layer properties is very challenging. Herein we address this need using a three dimensional (3D) computational model to systematically determine the effects of the gutter layer thickness and permeability on membrane performance. A key finding is that the introduction of a gutter layer between the selective layer and porous support can enhance the overall permeance of the penetrant by up to an order of magnitude, but this gain is accompanied by an undesired decrease in selectivity. The analysis also shows for the first time that a maximum increase in permeance with negligible decrease in selectivity is realized when the thickness of the gutter layer is 1-2 times the pore radius. The modeling approach provides clear and practical guidelines for designing ultrathin multilayer composite membranes to achieve high permeance and selectivity for low-cost and energy-efficient molecular separations.

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Gas permeation through ultrathin film composite (uTFC) membranes can be restricted by the pore size and porosity of the porous supports, resulting in a reduction in permeance. Although this geometric restriction has been demonstrated using empirical and computational models, a systematic experimental validation of the models is still lacking. This study addresses the gap by preparing a series of uTFC membranes comprising glassy perfluoropolymers (such as Teflon AF1600 and Hyflon AD80) as selective layers on top of a commercial poly­(ether sulfone) (PES) microporous support and investigating the effects of the surface morphology and selective layer thickness on the gas permeance. The geometric restriction resulting from the porous support becomes more severe as the selective layer becomes thinner. For example, the PES support decreased the gas permeance of a 100-nm-thick Hyflon AD80 film by as much as 42%. The experimental data agreed well with the modeling results, which convincingly confirms that porous supports with high porosity and small pores are needed to prepare high-flux uTFC membranes. This study also provides a nonintrusive method for determining the pore size and porosity of support surfaces, despite their great nonuniformity.

Graphene oxide (GO) nanosheets stacked in parallel with subnanometer channels can exhibit an excellent size-sieving ability for membrane-based gas separation. However, gas molecules have to diffuse through the tortuous nanochannels, leading to low permeability. Herein we demonstrate two versatile approaches to modify the GO (before membrane fabrication by vacuum-filtration) to collectively increase gas permeability, etching using hydrogen peroxide to generate in-plane nanopores and acidifying using hydrochloric acid. For example, a membrane prepared at a pH of 5.0 using the 4-h-etched GO (HGO-4h) shows He permeability of 5.3 Barrer and He/CH 4 selectivity of 800, which are 5 times and 1.5 times those of the GO membranes, respectively. Decreasing the pH from 5.0 to 2.0 for HGO-4h enhances He permeability to 57 Barrer and He/CH 4 selectivity to 1,800. The HGO-4h prepared at the pH of 2.0 exhibits separation properties of H 2 / CO 2 , H 2 /N 2 , He/N 2 , and He/CH 4 surpassing their corresponding upper bounds.

Polymers containing CO2‐philic groups are of great interest for CO2/light gas separation membranes because the affinity toward CO2 can effectively increase CO2 solubility and thus permeability. In this study, polysulfones (PSUs) modified with different degrees of benzyldimethylamine (DMA), benzyltrimethylammonium fluoride (TMAF), and benzyltrimethylammonium iodide (TMAI) were synthesized using sequential post‐functionalization reactions and investigated for CO2/N2 and CO2/CH4 separation. The physical properties of these polymers were studied, including density, fractional free volume, and glass transition temperature. In contrast to the conventional wisdom that tertiary amines exhibit an affinity toward CO2, this study convincingly shows that the DMA substituent has a minimal impact on CO2 solubility and CO2/light gas solubility selectivity in PSUs under dry condition. On the other hand, incorporating TMAF and TMAI in PSU significantly increases CO2 solubility. Particularly, introducing TMAI with a molar ratio of 1.07 relative to PSU repeating units increases CO2/CH4 solubility from 4.4 to 5.2, CO2/CH4 permeability selectivity from 21 to 45, and CO2/N2 permeability selectivity from 24 to 33 at 35 °C, while the CO2 permeability decreases from 5.6 to 1.7 Barrers. The effect of these functional groups in PSUs on gas diffusivity and diffusivity selectivity can be satisfactorily described by the free volume model. © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2018, 56, 1239–1250

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Two kinds of BMA (Blind Mate A) connector for RFID (Radio Frequency Identification) system, which works at 5.8GHz, is investigated in this paper. The BMA connectors are modeled and simulated in HFSS (High Frequency Structure Simulator). By analyzing the simulation results, three specific steps are adopted to optimize and improve the performance of the RF (Radio Frequency) circuit which is used in the RFID reader antenna port in this paper. At the same time, it chooses a type of BMA RF connector for RFID reader for the actual circuit design. Based on the analysis and optimization of the radio frequency circuit at the antenna port, the first prototype is fabricated and tested in 5.8GHz. The testing result shows that the reflection coefficient is less than -17dB and the VSWR (Voltage Standing Wave Ratio) is less than 1.3, which has a good correspondence with the simulation result in HFSS.

By using first principle calculations, a simple model of salinity sensor based on graphene electrode is constructed and its electron transport property is systematically investigated. It is found that all saltwater clusters at different salinity exhibit an obvious increase of the current while the saltwater to be detected is passing through the device. Moreover, only changing one Na atom acted as the conductive medium, and the electron transport behaviors could be clearly distinguished among the saltwater by negative differential resistance phenomenon, which demonstrates that the graphene-based salinity sensor could be capable of distinguishing saltwater at different salinity efficiently and accurately. This study provides a new path for the creation of the novel salinity sensor by graphene and other 2D material electrode.