The emulsification device is a silicon array of microfabricated, asymmetric throughholes with a slit and a circular channel an asymmetric straightthrough mc. In this paper, we use emulsions with monodisperse droplets, static calculation of the dependence of the stress on the strain obtained by a crystallization fractionation process 1, to at a. Introduction plaque formation on teeth, slime on contact lenses, and slippery sink drains are all everyday examples of thin, sur. Unfortunately, fundamental research on emulsions is not easy because model systems e. Multiple emulsions, in which dispersed drops contain smaller drops inside, are useful in a large number of commercial applications, including chemical synthesis and drug delivery.
Fieldinduced control of ferrofluid emulsion rheology and droplet. Preparation of uniformsized multiple emulsions and micronano. Although double emulsions are potentially of commercial value, traditional fabrication by means of two emulsification steps leads to very illcontrolled structuring. Pdf monodisperse double emulsions generated from a. Liquid crystalferrofluid emulsions soft matter rsc. Styrene monomer was replenished by micronsized styrene monomer droplets. Liquid crystalferrofluid emulsions soft matter rsc publishing. Ferrofluids have found their way into a variety of applications, such as sealing, damping and blood separation 2. Many efforts are made to produce uniform microparticles with custom sizes, shapes and morphologies using traditional methods, such as precipitation.
Thermal conductivity of emulsion with anisotropic microstructure. An applied magnetic field induces a magnetic dipole moment in each droplet, therefore, the ferrofluid becomes magnetized. Droplets can precisely monitor and control entire material fabrication processes and are superior to conventional bulk techniques. Generation and manipulation of monodispersed ferrofluid. In some cases the chaining effect is associated with a strong modification of the optical properties of the ferrofluid emulsion. Liquid crystalferrofluid emulsions ingo dierking, susumu yoshida, thomas kelly and william pitcher despite the development of the brilliant flatpanel tvs and computer screens that we all use on a daily basis, liquid crystals are far from being exhausted as a topic of research. Ferrofluid emulsions are colloidal suspensions of micronsized droplets, filled with a ferrofluid, in an immiscible neutral fiquid. Microbubbles, containing a gas core of soluble and insoluble gas components.
Weitz, school of engineering and applied sciences and department of physics, harvard university, cambridge, massachusetts 028, united states abstract. By applying an homogeneous field, droplet chains are observed. When the dipoledipole interaction energy exceeds the thermal energy, a phase transition occurs as the fluid of randomly dispersed droplets changes to a solid of nearly equally sized and spaced columns. Highly monodisperse ow emulsions with cv below 5 wt% were produced at tween 20 concentrations 19.
The microscale size of droplets results in rapid heat and mass. The structure of multiple emulsion systems is in this case defined as the number of bubbles. Wilking, shinhyun kim, ho cheung shum, and david a. Application of smallangle neutron scattering to the study of forces between magnetically chained monodisperse ferrofluid emulsion droplets february 2014 journal of applied crystallography 471. The ability to create uniform subnanoliter compartments using microfluidic control has enabled new approaches for analysis of single cells and molecules. Inair microfluidics enables rapid fabrication of emulsions. Weitz1,2 double emulsions are highly structured fluids consisting of emulsion drops that contain smaller droplets inside.
Weitz, journalscience, year2005, volume308, pages537 541. Initially we focused on tpm emulsions merely as a source for monodisperse inorganic cores to seed a surfactantfree pmma polymerization. Pdf preparation and characterization of highly stable. Droplet microfluidics for the production of microparticles and.
The magnetic emulsions were stabilized using different types of surfactants including ap, triton x 405 and sds. Jun 15, 2012 in this study, two different magnetic emulsions were used, low and high octane content magnetic emulsions. The authors report a realtime study of the evolution of the structure of confined ferrofluid emulsions during the liquidsolid phase transition. Mesoscopic monodisperse ferromagnetic colloids enable. Recently, manipulation of ferrofluids in a magnetic micropump and a magnetic fluid linear pump were demonstrated, but actuation was achieved. The structure evolution of the emulsion after rapidly. Pdf a generic singlestep synthesis of monodisperse core. The xray radiation source was a ceramic xray diffraction cu anode tube type kfl c 2k of 2. We can vary the cobalt ferrite loading in the polystyrene spheres by varying the concentration of cobalt ferrite nanoparticles in the emulsion polymerization reaction. These particles, obtained from a conventional ferrofluid, first form a monodisperse emulsion with a silane coupling agent, after which they are directly incorporated in pmma latex synthesized by standard emulsion polymerization. They are colloidal liquids made of nanoscale ferromagnetic, or ferrimagnetic, particles suspended in a carrier fluid usually an organic solvent or water. Each of the monodisperse ow emulsion had a sharp, monomodal droplet size distribution fig. May 18, 2009 sora hwang, changhyung choi and changsoo lee, regioselective surface modification of pdms microfluidic device for the generation of monodisperse double emulsions, macromolecular research, 10. Monodisperse emulsion drop microenvironments for bacterial bio.
Ferrofluid droplets have been widely used in a number of cuttingedge applications in microfluidics, biomedicine, and microrheology. Structure formation and chain dynamics in a dilute, monodisperse ferrofluid emulsion under the influence of an external magnetic field have been studied using dynamic light scattering. Fieldinduced structures in ferrofluid emulsions nasaads. Interaction of ferrofluid emulsions with a magnetic field is considered. Monodisperse emulsion drop microenvironments for bacterial.
Their basic structure consists of a dispersion of one phase into another one, in which the dispersed phase possesses a typical length scale ranging from a fewmolecular sizes up to several microns. Pdf generation and manipulation of monodispersed ferrofluid. Synthesis and characterization of monodisperse magnetite. To initiate the gelation, 200 l of silicic acid 1 m and 80 l of the biomimetic catalyst solution 67 mm were added to 200 l of a monodisperse hexadecaneinwater emulsion. The structure evolution of the emulsion after rapidly applying a. The structure formation and dynamics of a dilute, monodisperse ferrofluid emulsion under the influence of an external magnetic field have been investigated using static and dynamic light scattering techniques. Pdf application of smallangle neutron scattering to the.
The monodisperse ferrofluid emulsions show interesting behavior under an external magnetic field. Microfluidic liposome generation from monodisperse droplet. In ferrofluids, particles are usually smaller than the domain size, resulting. However, the method lacks an in situ determination of droplet size and, therefore, requires a combination of separately acquired. Morphology control of magnetic latex particles prepared from. A monodisperse oilinwater ferrofluid emulsion is used. Hence, the effective magnetic permeability of the ferrofluid emulsion starts decreasing.
Micromachines free fulltext droplet microfluidics for. Microfluidic liposome generation from monodisperse. Furthermore, inair microfluidics uniquely enables modulebased produc. For the first time, monodisperse nanobubbles nbs of a high throughput are generated directly via a microfluidic device. Preparation and properties of monodisperse latex spheres with. We have produced monodisperse emulsions consisting of ferrofluid droplets. Liquid crystal ferrofluid emulsions show potential as magnetic field sensors, by being able to determine the runtime of monodisperse ferrofluid droplets in a liquid crystal, as they could be generated via microfluidic devices. This is a unique advantage of studying ferrofluid emulsion properties in. This reaction occurs within minutes under benign conditions neutral ph and ambient temperature in contrast to conventional solgel routes 5. Double emulsions are highly structured fluids consisting of emulsion drops that contain smaller droplets inside. Monodisperse drops templated by 3dstructured microparticles. To generate the monodisperse double emulsions, we employ a microfluidic flowfocusing configuration along with a tjunction configuration as described in refs. The magnetic moment of the novel magnetic spheres is due to an inner core of magnetite particles. An applied magnetic field induces a magnetic dipole moment in each droplet.
Chain formation is found to be a diffusionlimited process that is well described by the smoluchowski theory of irreversible aggregation. In many cases, theories on emulsion stability are not exact and semiempirical approaches are used. Unfortunately, fundamental research into emulsions is not straightforward, as model systems e. The asymmetric throughholes of a uniform size stably yielded monodisperse emulsions with average droplet diameters of 35. Emulsion droplets with size of dec 16, 2004 monodisperse double emulsions generated from a microcapillary device a. Rheological and shearing conditions for the preparation of.
Ferrofluid is a liquid that is attracted to the poles of a magnet. In addition, four different initiators, including aibn, v50, acpa and kps were examined. Monodisperse emulsions can be obtained by shearing a crude. The fieldinduced structure in a monodisperse ferrofluid emulsion is studied. Download pdf ferrotec ferrofluid innovating ferrofluid. But the theory was developed only for a monodisperse system of. Application of smallangle neutron scattering to the study. In the absence of an external magnetic field, the oilinwater magnetic emulsions behaves like a classical oilinwater emulsion.
Dynamics of dipole chains in a ferrofluid emulsion. Microfluidic generation of tunable monodisperse double. Novel asymmetric throughhole array microfabricated on a. Drops deformation and magnetic permeability of a ferrofluid emulsion. Monodisperse microparticles and nanoparticles with uniform sizes and morphologies are used in biopharmaceuticals 1,2, drug delivery applications 3,4, electrooptic devices 5,6 and catalysis 7,8,9 because of their unique properties. Synthesis and characterization of monodisperse magnetite hollow microspheres. Quite recently, a new synthesis method for very monodisperse magnetite dispersions. Monodisperse gasfilled microparticles from reactions in double emulsions wynter j. Morphology control of magnetic latex particles prepared. Large ferromagnetic particles can be ripped out of the homogeneous colloidal mixture. Emulsions from the chip were collected offchip in a vial and used as templates around which silica gel was formed in the biomimetic reaction. Scattering from the latex shell dominates over light absorption by the magnetic cores such that visible bragg reflections of the magnetic crystals. Highly magnetizable superparamagnetic colloidal aggregates with narrowed size distribution from ferrofluid emulsion.
The synthesis is based on reacting ironii and ironiii ions in an aqueous ammonia solution to form magnetite, fe 3 o 4, as shown in eq 1. Generally, ferrofluids are not conductive, so that they can not be directly determined by closing an electronic switch. D d decreases with increasing c but d d decreases with increasing volume. We have proposed a novel microchannel mc structure for formulating monodisperse emulsions. Besides ferrofluids, the study of monodisperse magnetic emulsions is an. In the absence of an external magnetic field, the oilinwater magnetic. Monodisperse wow double emulsions stabilized by a diblock polymer of peg5000bpla5000 are prepared in glass microcapillary devices,16 as shown schematically in figure 1. Droplet production is controlled by regulating the channel geometry and flow rates of each fluid. Ageneric singlestep synthesis of monodisperse coreshell. Phase transitions in a ferrofluid at magneticfieldinduced. Microfluidic generation of monodisperse nanobubbles by. Each magnetic particle is thoroughly coated with a surfactant to inhibit clumping. From singlecore nanoparticles in ferrofluids to multicore.
Monodisperse fe 3 o 4 npspst nanoparticles were prepared through the socalled activated swelling method of emulsion polymerization 23 where the smaller ferrofluid droplets are polymerization loci. Using a microcapillary device, we fabricated double emulsions that contained a single internal droplet in a core. In the absence of an external magnetic field, the oilinwater magnetic emulsion. Liquid crystal ferrofluid emulsions show potential as magnetic field sensors, by being able to determine the runtime of monodisperse ferrofluid. Application of smallangle neutron scattering to the study of. The d av and cv of the produced emulsions are shown in fig. Generation and manipulation of monodispersed ferrofluid emulsions. Preparation and properties of monodisperse latex spheres.
Pdf the paper is concerned with a theoretical explanation of the. Preparation and characterization of monodisperse magnetic poly. Droplet microfluidics technology is recently a highly interesting platform in material fabrication. Efh series ferrofluid page 1 of 7 safety data sheet.
Therefore, the addition of an osmotic agent that cannot interdiffuse between two droplets, and the use of an appropriate hydrophobic surfactant, could both be essential for preparation of stable and monodisperse waterin oil emulsions, with droplet sizes ranging from 50 to 500 nm, well known as inverse miniemulsions landfester, 2000. Here, we show that three dimensionalstructured microparticles with sculpted surface chemistries template uniformly. The structure evolution of the emulsion after rapidly applying a magnetic field is probed by the static light scattering. In fact, in many cases, the theoretical bases of emulsion stability are not exact and consequently semiempirical approaches are used. Acros are mixed to a water based ferrofluid 7 ml of a 2. Emulsion droplets with size of monodisperse magnetite hollow microspheres. However, specialized instruments or expertise has been required, slowing the adoption of these cuttingedge applications. These systems are particularly suitable for studying the chaining effect of these magnetic droplets and ultimately some properties related to these reversible structures. For many of these applications, it is critical to have control over the size and structure of multiple emulsion systems.
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