Effective Cell and Particle Sorting and Separation in Screen-Printed Continuous-Flow Microfluidic Devices with 3D Sidewall Electrodes

In recent years, microfluidic dielectrophoresis (DEP) devices, as one of the most promising tools for cell and particle sorting and separation, are facing the bottleneck in the development of practical products due to the high-cost yet low-yield device manufacturing via traditional microelectromechanical systems (MEMS) and the challenge of maintaining the cell viability during DEP treatment. In this paper, we demonstrate a facile, low-cost, and high-throughput method of constructing continuous-flow microfluidic DEP devices via screen-printing technology. The new device configuration and operation strategy not only facilitate cell and particle sorting and separation using 3D electrodes as sidewalls of microchannel but also improve cell viability by reducing the exposure time of cells to high electrical-field gradients. Furthermore, we propose and validate a semiempirical formula with which to simplify the complicated calculation and plotting of DEP spectra. As a consequence, the optimal DEP parameters and crossover frequencies can be obtained directly using our devices instead of typical electrorotation method. To evaluate the performance of a screen-printed continuous flow microfluidic DEP device, a suspension containing polystyrene (PS) microspheres and erythrocytes is used as the biosample. Our results show that a high sorting efficiency (ca. 93%) with a high cell viability (hemolysis ratio of <4.8%) can be achieved, indicating the excellent performance and promising application of such devices for cell and particle sorting and separation

Influence of Viscosity and Magnetoviscous Effect on the Performance of a Magnetic Fluid Seal in a Water Environment

<p>The magnetic fluid seal is one of the most successful applications of magnetic fluids. The theory of magnetic fluid seals in liquid environments has not been developed. This work mainly presents an experimental study of the influence of viscosity and magnetoviscous effects on the performance of a magnetic fluid seal in a water environment. Three engine oil–based magnetic fluids of different viscosities and similar saturation magnetization values were prepared and a multistage magnetic seal structure was designed. The magnetoviscous effect of the magnetic fluids under different working conditions was measured with an advanced rotational rheometer. An experimental platform and a multistage magnetic seal structure were designed for the critical pressure value and durability tests. The experimental results show that the viscosity of a magnetic fluid is a decisive factor in its sealing performance under a water environment and a discussion is presented that can explain the experimental results qualitatively.</p

Methods for investigating crash risk: Comparing case–control with responsibility analysis

<p><b>Objective:</b> There are 2 primary methods for establishing relative risk: <i>case–control studies</i>, in which crash and matched control data are collected separately, and <i>responsibility analysis</i>, which exploits a single existing crash database by using nonresponsible drivers as an “induced exposure” control group (which is less expensive and therefore more feasible for examining the large number of substances that can impact driving behavior). Though both approaches are scientifically sound and methodologically valid, each approach has its own inherent obstacles to overcome. In this article, we examine in detail how different criteria for the development of control cases influence the accuracy of crash risk estimates for drivers with positive blood alcohol concentrations (BACs).</p> <p><b>Methods:</b> We applied responsibility analysis to crash-involved drivers in a recent crash case–control study, thereby providing 2 sets of control cases: Those from responsibility analysis and those from the case control study.</p> <p><b>Results:</b> Case–control and responsibility analysis crash risk curves did not differ significantly, indicating that both systems generate valid estimates of the relative crash risk of drivers on the road.</p> <p><b>Conclusions:</b> The results suggest that when researchers are faced with finance or time constraints that make case–control studies infeasible, responsibility analysis should be considered a viable alternate methodological approach.</p

Additional file 1: of What are patients’ expectations of orthodontic treatment: a systematic review

Search Strategy. (PDF 45 kb

Additional file 2: Table S1. of What are patients’ expectations of orthodontic treatment: a systematic review

Study quality and main findings summary [7, 8, 12, 20–27, 29, 30, 33]. (PDF 121 kb

Kinetic Modeling of the Transesterification Reaction of Dimethyl Carbonate and Phenol in the Reactive Distillation Reactor

The kinetic behavior of preparing diphenyl carbonate by the transesterification of dimethyl carbonate with phenol in a reactive distillation reactor has been explored experimentally and theoretically. The transesterification reaction was described to conform a pseudo-second-order kinetics, and a semi-empirical kinetic model has been derived to explain the kinetic behavior. The model parameters were fitted to experimental data by an improved genetic algorithm. The proposed model was determined to be useful in simulating the rate constant and the mole fraction of components, which agreed well with the experimental data for different operating temperatures and catalyst concentrations

Additional file 3: Table S2. of What are patients’ expectations of orthodontic treatment: a systematic review

Parameters of measurement and scale evaluations [7, 8, 12, 20–31, 33]. (PDF 149 kb

Structure–Property Relationship of Low-Dimensional Layered GaSe_<i>x</i>Te_1–<i>x</i> Alloys

We report the growth of layered GaSe_<i>x</i>Te_1–<i>x</i> mesostructures across the whole composition range. For compositions up to <i>x</i> = 0.32 (the Te-rich region), mesocrystals form predominantly in the monoclinic structure, similar to naturally occurring GaTe. However, the hexagonal crystal structure, similar to naturally occurring GaSe, begins growing at the <i>x</i> = 0.28 composition and grows almost exclusively in the range of <i>x</i> = 0.32 to pure GaSe, establishing a region of composition where both monoclinic and hexagonal crystals exist. While the optical bandgap of the monoclinic phase increases linearly from 1.65 to 1.77 eV with increasing Se content, the incorporation of Te in the hexagonal phase reduces the optical gap from 2.01 (pure GaSe) to 1.38 eV (<i>x</i> = 0.28). Specifically, a bandgap difference of ∼0.35 eV between monoclinic and hexagonal crystals is observed in the composition range where both crystal structures can be grown. These observations are in good agreement with direct-gap trends calculated by density functional theory, which show a linear dependence on composition for the direct gap of the monoclinic phase and a considerable bowing of the direct gap of the hexagonal phase for Te-rich compositions. Our results show that layered semiconductor alloys are remarkably versatile systems in which electronic properties can be controlled by not only thickness but also structural phase and composition

Synthesis of MoS₂ and MoSe₂ Films with Vertically Aligned Layers

Layered materials consist of molecular layers stacked together by weak interlayer interactions. They often crystallize to form atomically smooth thin films, nanotubes, and platelet or fullerene-like nanoparticles due to the anisotropic bonding. Structures that predominately expose edges of the layers exhibit high surface energy and are often considered unstable. In this communication, we present a synthesis process to grow MoS₂ and MoSe₂ thin films with vertically aligned layers, thereby maximally exposing the edges on the film surface. Such edge-terminated films are metastable structures of MoS₂ and MoSe₂, which may find applications in diverse catalytic reactions. We have confirmed their catalytic activity in a hydrogen evolution reaction (HER), in which the exchange current density correlates directly with the density of the exposed edge sites

Static Electricity Powered Copper Oxide Nanowire Microbicidal Electroporation for Water Disinfection

Safe water scarcity occurs mostly in developing regions that also suffer from energy shortages and infrastructure deficiencies. Low-cost and energy-efficient water disinfection methods have the potential to make great impacts on people in these regions. At the present time, most water disinfection methods being promoted to households in developing countries are aqueous chemical-reaction-based or filtration-based. Incorporating nanomaterials into these existing disinfection methods could improve the performance; however, the high cost of material synthesis and recovery as well as fouling and slow treatment speed is still limiting their application. Here, we demonstrate a novel flow device that enables fast water disinfection using one-dimensional copper oxide nanowire (CuONW) assisted electroporation powered by static electricity. Electroporation relies on a strong electric field to break down microorganism membranes and only consumes a very small amount of energy. Static electricity as the power source can be generated by an individual person’s motion in a facile and low-cost manner, which ensures its application anywhere in the world. The CuONWs used were synthesized through a scalable one-step air oxidation of low-cost copper mesh. With a single filtration, we achieved complete disinfection of bacteria and viruses in both raw tap and lake water with a high flow rate of 3000 L/(h·m²), equivalent to only 1 s of contact time. Copper leaching from the nanowire mesh was minimal