A device able to electrokinetically concentrate cationic samples has many potential medical and industrial applications, but until now has remained undeveloped due to the lack of a commercial ...anion‐permselective material leading to a prohibitively complex fabrication procedure. Herein, a novel multiscale‐porous anion exchange membrane (MP‐AEM) that enables the convenient and scalable electrokinetic concentration of cationic species is proposed. A mechanically enhanced multiscale‐porous structure with a solid framework is realized by adopting polyester resin as an additive to overcome the intrinsic limitations of the AEM material. The scalable MP‐AEM‐embedded electrokinetic concentrator is devised based on the peculiar properties of the MP‐AEM that for allow both ion and fluid transport. With the MP‐AEM, the concentrator is fabricated in a highly streamlined manner consisting only of a simple insertion and assembly. The concentration performance of the MP‐AEM‐embedded electrokinetic concentrator is demonstrated with a positively charged fluorescent dye and a fluorescein‐labeled protein, and the results show enrichment factors of 250 and 500, respectively. The MP‐AEM makes cationic electrokinetic concentration more accessible and scalable, thereby enabling further progress in a wide range of fields.
A multiscale‐porous anion exchange membrane (MP‐AEM) is developed as an easily accessible anion‐permselective material for the electrokinetic concentration of cationic species. The MP‐AEM's highly streamlined fabrication process enables convenient cation‐selective electrokinetic concentrator assembly, and its demonstrated scalability shows great potential for use in a variety of high‐throughput applications.
Recently, consumer applications have dramatically created the demand for low-cost and compact gyroscopes. Therefore, on the basis of microelectromechanical systems (MEMS) technology, many gyroscopes ...have been developed and successfully commercialized. A MEMS gyroscope consists of a MEMS device and an electrical circuit for self-oscillation and angular-rate detection. Since the MEMS device and circuit are interactively related, the entire system should be analyzed together to design or test the gyroscope. In this study, a MEMS vibratory gyroscope is analyzed based on the system dynamic modeling; thus, it can be mathematically expressed and integrated into a circuit simulator. A behavioral simulation of the entire system was conducted to prove the self-oscillation and angular-rate detection and to determine the circuit parameters to be optimized. From the simulation, the operating characteristic according to the vacuum pressure and scale factor was obtained, which indicated similar trends compared with those of the experimental results. The simulation method presented in this paper can be generalized to a wide range of MEMS devices.
A portable seawater desalination system would be highly desirable to solve water challenges in rural areas and disaster situations. While many reverse osmosis-based portable desalination systems are ...already available commercially, they are not adequate for providing reliable drinking water in remote locations due to the requirement of high-pressure pumping and repeated maintenance. We demonstrate a field-deployable desalination system with multistage electromembrane processes, composed of two-stage ion concentration polarization and one-stage electrodialysis, to convert brackish water and seawater to drinkable water. A data-driven predictive model is used to optimize the multistage configuration, and the model predictions show good agreement with the experimental results. The portable system desalinates brackish water and seawater (2.5–45 g/L) into drinkable water (defined by WHO guideline), with the energy consumptions of 0.4–4 (brackish water) and 15.6–26.6 W h/L (seawater), respectively. In addition, the process can also reduce suspended solids by at least a factor of 10 from the source water, resulting in crystal clear water (<1 NTU) even from the source water with turbidity higher than 30 NTU (i.e., cloudy seawater by the tide). We built a fully integrated prototype (controller, pumps, and battery) packaged into a portable unit (42 × 33.5 × 19 cm3, 9.25 kg, and 0.33 L/h production rate) controlled by a smartphone, tested for battery-powered field operation. The demonstrated portable desalination system is unprecedented in size, efficiency, and operational flexibility. Therefore, it could address unique water challenges in remote, resource-limited regions of the world.
There is an increasing need for the desalination of high concentration brine (>TDS 35,000 ppm) efficiently and economically, either for the treatment of produced water from shale gas/oil development, ...or minimizing the environmental impact of brine from existing desalination plants. Yet, reverse osmosis (RO), which is the most widely used for desalination currently, is not practical for brine desalination. This paper demonstrates technical and economic feasibility of ICP (Ion Concentration Polarization) electrical desalination for the high saline water treatment, by adopting multi-stage operation with better energy efficiency. Optimized multi-staging configurations, dependent on the brine salinity values, can be designed based on experimental and numerical analysis. Such an optimization aims at achieving not just the energy efficiency but also (membrane) area efficiency, lowering the true cost of brine treatment. ICP electrical desalination is shown here to treat brine salinity up to 100,000 ppm of Total Dissolved Solids (TDS) with flexible salt rejection rate up to 70% which is promising in a various application treating brine waste. We also demonstrate that ICP desalination has advantage of removing both salts and diverse suspended solids simultaneously, and less susceptibility to membrane fouling/scaling, which is a significant challenge in the membrane processes.
Many industries have a significant but largely unmet need for efficient and high-flux emulsion separation, particularly for nanoemulsions. Conventional separation membranes rely on size-based ...separation mainly utilizing a sieving mechanism plus a wetting phenomenon, resulting in a dramatic trade-off between separation efficiency and separation flux. Herein we address this challenge by adapting electrokinetics to membrane-based separation, using a charge-based mechanism capable of separating even nanoemulsions with a demonstrated separation efficiency of >99% and ultrahigh flux up to 40 000 L/H·m2. Our device arrests nano-oil droplets, allowing them to coalesce into larger droplets which are then able to be filtered by coarser membranes. This hybrid technology makes electrokinetic-assisted filtration scalable and commercially viable and allows for a better understanding of the multiphysics underlying dynamic separation.
Two different lots of cation-exchange membranes (CMX-SB-1 and -2) were compared in terms of physico-chemical and electrochemical properties. Further, electrodialysis with both membrane lots was ...carried out under pulsed electric field (PEF) on model solution containing Ca2+ and Mg2+ ions. It was found that CMX-SB-1 was more scaled with prevalence of Ca compounds on both membrane sides. CMX-SB-2 contained less scaling with prevalence of Ca compounds on diluate side and Mg compounds on concentrate side. The different behavior of membranes was hypothesized to be due to the differences in their intrinsic structure and surface properties. The CMX-SB-2 has higher concentration of fixed charges and water content, which cause larger size of inner channels and easier transport of Mg2+; the structural organization of CMX-SB-1 with presumably narrower nanochannels leads to the slower Mg2+ migration and their low quantity on CMX-SB-1 concentrate side. Additionally, the surface hydrophobicity and heterogeneity of CMX-SB-2 is higher than that of CMX-SB-1 what allow easier water slip on CMX-SB-2 surface facilitating electroconvection. Thus, more scaled CMX-SB-1 membrane with less developed electroconvection yielded lower values of demineralization (59.0% and 57.2% for 2s/0.5s and 2s/0.67s PEF respectively) than the less scaled CMX-SB-2 with better developed electroconvection (77.3% and 75.2% respectively).
•Membrane nanostructure influences scaling composition and structure.•Membrane surface properties have a major role on electroconvection development.•Electroconvective vortices affect the scaling quantity and ED performance.•Pulse lapse duration impacts development of electroconvective vortices.•Pause lapse duration impacts development of inertial vortices.
Recently, tremendous engineering applications utilizing new physics of nanoscale electrokinetics have been reported and their basic fundamentals are actively researched. In this work, we first report ...a simple and economic but reliable nanochannel fabrication technique, leading to a heterogeneously charged triangular nanochannel. The nanochannel utilized the elasticity of PDMS when it bonded with a micrometer-scale structure on a substrate. Second, we successfully demonstrated novel ionic transportations by tweaking the micrometer structures: (1) the transition of nonlinear ionic conductance depending on the nanochannel properties and (2) the ionic field-effect transistor. Nanochannel conductance has two distinguishable nonlinear regimes called the “surface-charge-governed” and the “geometry-governed” regime and its only individual overlooks were frequently reported. However, the transition between two regimes by adjusting nanochannel properties has not been reported due to the difficulty of functional nanochannel fabrication. In addition, a gate voltage was comfortably applied to the triangular nanochannel so that the field-effect ion transportation was reliably achieved. Therefore, presenting triangular nanochannels have critical advantages over its heterogeneous and tunable surface properties and thus, could be an effective means as an active fundamental to control and manipulate the ion-electromigration through a nanofluidic system.
Nanofabrication technologies have been a strong advocator for new scientific fundamentals that have never been described by traditional theory, and have played a seed role in ground-breaking ...nano-engineering applications. In this study, we fabricated ultra-high-aspect (∼10(6) with O(100) nm nanochannel opening and O(100) mm length) orthogonal nanochannel array using only polymeric materials. Vertically aligned nanochannel arrays in parallel can be stacked to form a dense nano-structure. Due to the flexibility and stretchability of the material, one can tune the size and shape of the nanochannel using elongation and even roll the stack array to form a radial-uniformly distributed nanochannel array. The roll can be cut at discretionary lengths for incorporation with a micro/nanofluidic device. As examples, we demonstrated ion concentration polarization with the device for Ohmic-limiting/overlimiting current-voltage characteristics and preconcentrated charged species. The density of the nanochannel array was lower than conventional nanoporous membranes, such as anodic aluminum oxide membranes (AAO). However, accurate controllability over the nanochannel array dimensions enabled multiplexed one microstructure-on-one nanostructure interfacing for valuable biological/biomedical microelectromechanical system (BioMEMS) platforms, such as nano-electroporation.
In recent years, there has been an increase in the number of phishing attacks targeting people in the fields of defense, security, and diplomacy around the world. In particular, hacking attack group ...Kimsuky has been conducting phishing attacks to collect key information from public institutions since 2013. The main feature of the attack techniques used by the Kimsuky attack group are to conceal malicious code in phishing e-mails disguised as normal e-mails to spread a document file that is vulnerable to security, such as a Hangul file, or to induce interest through a social engineering attack technique to collect account information. This study classified the types of phishing e-mail attacks into spoofed e-mails, e-mail body vulnerability use, and attached file spoofing, and detailed analyses of their attack methods, such as commonality and characteristic analyses, were performed to analyze the profile of this phishing e-mail attack group. Based on the results, the purpose of the attacking group was determined to be intelligence gathering because it focused on phishing attacks targeting Korean diplomatic and defense public institutions and related foreign institutions. Finally, a countermeasure that can be used by mail service providers and mail users to respond to phishing e-mails is suggested.
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