Fabrication of polymersomes with controllable morphologies through dewetting w/o/w double emulsion droplets

In this work, monodisperse giant polymersomes are fabricated by dewetting of water-in-oil-in-water double emulsion droplets which are assembled by amphiphilic block copolymer molecules in a microfluidic device. The dewetting process can be tuned by solvation between solvent and amphiphilic block copolymer to get polymersomes with controllable morphology. Good solvent(chloroform and toluene) hinders dewetting process of double emulsion droplets and gets acornlike polymersomes or patched polymersomes. On the other hand, poor solvent(hexane) accelerates the dewetting process and achieves complete separation of inner water phase from oil phase to form complete bilayer polymersomes. In addition, twin polymersomes with bilayer membrane structure are formed by this facile method. The formation mechanism for different polymersomes is discussed in detail.     

Numerical simulation of double emulsion formation in cross-junctional flow-focusing microfluidic device using Lattice Boltzmann method

This paper presents an analysis of double emulsion formation through a cross junctional flow-focusing microchannel which uses an improved color gradient lattice Boltzmann method. The model with the potential to simulate a ternary system of immiscible fluids was employed. Two double emulsion formation regimes, one-step and two-step, were simulated. The effect of the inner flow rate, as well as inner and outer flow viscosity was investigated on double emulsion formation. The inner flow rate had a significant influence on the inner liquid jet detachment point in the two-step process. However, the viscosity of the inner and outer fluid considerably affected the double jet detachment point in the one-step formation. The shell thickness of a double emulsion can be adjusted by altering the inner flow rate.     

Single-molecule emulsion PCR in microfluidic droplets

The application of microfluidic droplet PCR for single-molecule amplification and analysis has recently been extensively studied. Microfluidic droplet technology has the advantages of compartmentalizing reactions into discrete volumes, performing highly parallel reactions in monodisperse droplets, reducing cross-contamination between droplets, eliminating PCR bias and nonspecific amplification, as well as enabling fast amplification with rapid thermocycling. Here, we have reviewed the important technical breakthroughs of microfluidic droplet PCR in the past five years and their applications to single-molecule amplification and analysis, such as high-throughput screening, next generation DNA sequencing, and quantitative detection of rare mutations. Although the utilization of microfluidic droplet single-molecule PCR is still in the early stages, its great potential has already been demonstrated and will provide novel solutions to today's biomedical engineering challenges in single-molecule amplification and analysis.     

T cell chemotaxis in a simple microfluidic device

This paper describes the use of a simple microfluidic device for studying T cell chemotaxis. The microfluidic device is fabricated in poly(dimethylsiloxane) (PDMS) using soft-lithography and consists of a "Y" type fluidic channel. Solutions are infused into the device by syringe pumps and generate a concentration gradient in the channel by diffusion. We show that the experimentally measured gradient profiles agree nicely with theoretical predictions and the gradient is stable in the observation region for cell migration. Using this device, we demonstrate robust chemotaxis of human T cells in response to single and competing gradients of chemokine CCL19 and CXCL12. Because of the simplicity of the device, it can flexibly control gradient generation in space and time, and would allow generation of multiple gradient conditions in a single chip for highly parallel chemotaxis experimentation. Visualization of T cell chemotaxis has previously been limited to studies in 3D matrices or under agarose assays, which do not allow precise control or variation in conditions. Acknowledging the importance of lymphocyte homing in the adaptive immune response, the ability to study T cell chemotaxis in microfluidic devices offers a new approach for investigating lymphocyte migration and chemotaxis in vitro.     

Interfacial organic synthesis in a simple droplet-based microfluidic system

A spherical liquid-liquid interface can be obtained by dispersing one liquid phase into another to form droplets, which will facilitate the two-phase reactions between the immiscible participating fluids. The phase transfer catalysts assembled at the droplet "wall" catalyze the reactions between the aqueous and organic phases. The study illustrates an interfacial synthetic approach which is ideal for the biphasic reaction by taking advantage of the droplet-based microdevice. The improved reaction efficiency can be attributed to the high surface-to-volume ratio and internal flow circulation in the droplets.     

Model-controlled hydrodynamic focusing to generate multiple overlapping gradients of surface-immobilized proteins in microfluidic devices

Historically, it has been difficult to generate accurate and reproducible protein gradients for studies of interactions between cells and extracellular matrix. Here we demonstrate a method for rapid patterning of protein gradients using computer-driven hydrodynamic focusing in a simple microfluidic device. In contrast to published work, we are moving the complexity of gradient creation from the microfluidic hardware to dynamic computer control. Using our method, switching from one gradient profile to another requires only a few hours to devise a new control file, not days or weeks to design and build a new microfluidic device. Fitting existing protein deposition models to our data, we can extract key parameters needed for controlling protein deposition. Several protein deposition models were evaluated under microfluidic flow conditions. A mathematical model for our deposition method allows us to determine the parameters for a protein adsorption model and then predict the final shape of the surface density gradient. Simple and non-monotonic single and multi-protein gradient profiles were designed and deposited using the same device.     

Breakup of double emulsion droplets in a tapered nozzle

When double emulsion droplets flow through a tapered nozzle, the droplets may break up and cause the core to be released. We model the system on the basis of the capillary instability and show that a droplet will not break up when the tilt angle of the nozzle is larger than 9°. For smaller tilt angles, whether the droplet breaks up also depends on the diameter ratio of the core of the droplet to the orifice of the nozzle. We verified this mechanism by experiments. The ideas are useful for the design of nozzles not only to break droplets for controlled release but also to prevent the droplet from rupturing in applications requiring the reinjection of an emulsion.     

A microfluidic glucose biofuel cell to generate micropower from enzymes at ambient temperature

A Y-shaped microfluidic channel is applied for the first time to the construction of a glucose/O₂ biofuel cell, based on both laminar flow and biological enzyme strategies. During operation, the fuel and oxidant streams flow parallel at gold electrode surfaces without convective mixing. At the anode, the glucose oxidation is performed by the enzyme glucose oxidase whereas at the cathode, the oxygen is reduced by the enzyme laccase, in the presence of specific redox mediators. Such cell design protects the anode from an interfering parasite reaction of O₂ at the anode and offers the advantage of using different streams of oxidant and fuel for optimal performance of the enzymes. Electrochemical characterizations of the device show the influence of the flow rate on the output potential and current density. The maximum power density delivered by the assembled biofuel cell reached 110 μW cm^?2 at 0.3 V with 10 mM glucose at 23 °C. The microfluidic approach reported here demonstrates the feasibility of advanced microfabrication techniques to build an efficient microfluidic glucose/O₂ biofuel cell device.     

Analysis of chemoresistance in lung cancer with a simple microfluidic device

Microchip-based systems have been developed rapidly due to their desirable advantages over conventional platforms. Higher level system integration and complex microdevices are emerging to satisfy the demand for high-throughput and large-scale applications. However, most of the devices need to be fabricated with complicated microvalves and micropumps, which, to some extent, limit the use of the novel technique. In this study, a simple microdevice was developed to perform chemotherapy resistance analysis in lung cancer cell line SPCA1. This device includes a PDMS chip for which a simple external small clip served as a microvalve to control the fluid flow so that the parallel control experiment could be carried out simultaneously, and a syringe pump, which supplied the cells with fresh medium mimicking the microenvironment in vivo. Cell culture, detection of drug resistance related protein P-glycoprotein (P-gp) and glutathione S-transferase-π (GST-π) and cell viability after VP-16 treatment on experimental (pretreated with corresponding inhibitors) and control groups were achieved. The results demonstrated that the cells could grow and spread well for at least 3 days. The expression of P-gp and GST-π was obviously downregulated by corresponding inhibitors. The percentage of apoptotic cells for P-gp inhibition group increased 2.9-fold compared with that of control group (23.7 ± 2.6 versus 8.1 ± 3.0%, p<0.05), while for GST-π inhibition, there was no obvious distinction between the experimental and control group. The simple microdevice is capable of integrating parallel operations involving cell culture and functional analysis, offering an easy and flexible platform for a stable long-term cell culture and comparison research.     

Attempts to generate a homocycloheptatrienylidene

Attempts to generate homocyclooctatetraene by dehydrohalogenation of 8-chlorobicyclo [5.1.0] octadiene led to cyclooctatetraene, styrene and heptafulvene.     

The double addition reaction of alkoxymethyl nucleophiles to esters to generate novel polyoxygenated species

The development of a double addition reaction of alkoxylmethyl nucleophiles to a variety of functionalized aryl and alkyl esters to give polyoxygenated products is reported. Key features include broad electrophile substrate scope and good yields. Structurally diverse nucleophiles were investigated and were found to successfully undergo diaddition. This development now allows facile access to this novel class of polyoxygenated molecules.     

Controllable gas/liquid/liquid double emulsions in a dual-coaxial microfluidic device

This article presents a simple and novel approach to prepare monodispersed gas-in-oil-in-water (G/O/W) and gas-in-water-in-oil (G/W/O) double-emulsions in the same dual-coaxial microfluidic device. The effects of three phase flow rates on the sizes of microbubbles and droplets and the number of the encapsulated microbubbles were systematically studied. We successfully synthesized two different types of gas/liquid/liquid (G/L/L) double emulsions with different inner structures in the same geometry by adjusting the flow rates sequentially. Mathematical models were developed to predict the size and structures of the double emulsions. This simple approach gives a new idea for preparing hollow and porous microspheres with microbubbles as the direct core/pores templates.     

High throughput production of single core double emulsions in a parallelized microfluidic device

Double emulsions are useful templates for microcapsules and complex particles, but no method yet exists for making double emulsions with both high uniformity and high throughput. We present a parallel numbering-up design for microfluidic double emulsion devices, which combines the excellent control of microfluidics with throughput suitable for mass production. We demonstrate the design with devices incorporating up to 15 dropmaker units in a two-dimensional or three-dimensional array, producing single-core double emulsion drops at rates over 1 kg day(-1) and with diameter variation less than 6%. This design provides a route to integrating hundreds of dropmakers or more in a single chip, facilitating industrial-scale production rates of many tons per year.     

A simple and effective technique to locate quasi-degeneracy in a symmetric double well potential

Perturbation theory based model can be used to locate the quasi-degeneracy in an arbitrary double well potential. This method, extensively explain the effect of the coupling term on pair of states called quasi-degenerate. This model helps us to calculate the energy of the pair of quasi-degenerate states using appreciably small basis. Dispersion equation corresponding to the split energy levels are presented in a very explicit form. Numerical calculation shows that the proposed method can give extremely accurate results for symmetric double-well potentials.     

Polymerization of electric field-centered double emulsion droplets to create polyacrylate shells

Porous and hollow particles are widely used in pharmaceuticals, as solid phases for chromatography, as catalyst supports, in bioanalytical assays and medical diagnostics, and in many other applications. By controlling size, shape, and chemistry, it is possible to tune the physical and chemical properties of the particles. In some applications of millimeter-scale hollow shells, such as in high energy density physics, controlling the shell thickness uniformity (concentricity) and roundness (sphericity) becomes particularly important. In this work, we demonstrate the feasibility of using electric field-driven droplet centering to form highly spherical and concentric polymerizable double emulsion (DE) droplets that can be subsequently photopolymerized into polymer shells. Specifically, when placed under the influence of an ～6 × 10(4) V(rms)/m field at 20 MHz, DE droplets, consisting of silicone oil as the inner droplet and tripropylene glycol diacrylate with a photoinitiator in N,N-dimethylacetamide as the outer droplet, suspended in ambient silicone oil, were found to undergo electric field-driven centering into droplets with ≥98% sphericity and ～98% concentricity. The centered DE droplets were photopolymerized in the presence of the electric field. The high degrees of sphericity and concentricity were maintained in the polymerized particles. The poly(propylene glycol diacrylate) capsules are just within the sphericity requirements needed for inertial confinement fusion experiments. They were slightly outside the concentricity requirement. These results suggest that electric field-driven centering and polymerization of double emulsions could be very useful for synthesizing hollow polymer particles for applications in high energy density physics experiments and other applications of concentric polymer shells.     

Single versus double insertion in a simple intermolecular carbene reaction

The carbene reaction ¹CH₂ + C₂H₆ was studied with the semiempirical method SINDO 1. The pertinent transition states and products were obtained by geometry optimization on a CI surface. We find the insertion reaction forming C₃H₈ greatly favored compared to the double insertion leading to CH₄ + C₂H₄. The result is qualitatively the same for the reaction of the two possible intermediate radicals CH₃ and C₂H₅. The geometries and energies of all transition states are presented.     

Destabilization of a dual emulsion to form a Janus emulsion

A vegetable oil (VO) was added to an emulsion of silicone oil in water (SO/W) with mixing limited to once turning the test tube upside down. Initially, the VO was dispersed into virtually centimeter-sized drops and the emulsion contained effectively no Janus drops, while after 1 h of agitation at a low level to prevent creaming, drops of 50–100-μm size of the two oils were observed: in addition to an insignificant number of Janus drops. The topology of the latter showed them to emanate from flocculated individual drops of the two oils, but with no discernible effect by the interfacial tension equilibrium on the drop topology. Continued gentle mixing gave increasing fraction of Janus drops of increased size with a topology gradually approaching the one expected from the interfacial equilibrium at the contact line. The spontaneous formation of Janus drops indicated a reduction of the interfacial free energy in the process and the interfacial energy difference between separate and Janus drops was calculated for an appropriate range of interfacial tensions and for all oil fractions. The calculations enabled a distinction of the decrease due to interfacial area changes from the reduction of interfacial tensions per se, with the latter only a minor fraction. Figure

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