Uniform Droplet Size Research Articles

Surfactant–cosurfactant interactions and process parameters involved in the formulation of stable and small droplet-sized benznidazole-loaded soybean O/W emulsions

The ability of different surfactant mixtures (SM) (polysorbate 80/sorbitan monooleate, 5 to 10% w/w) with cosurfactants (CO) (benzyl alcohol, ethanol, and 2-methylpyrrolidone) to produce stable benznidazole (BNZ) loaded soybean oil (SO, 10 to 30% w/w) in water (O/tW) emulsions was well assessed. Statistical tests were performed to select the best procedure parameters (temperature, shake conditions, and order inversion phases), using a phase inversion technique (PIT). Phase behavior was assessed by the pseudo-ternary phase diagram at the best HLB (9.0). Physicochemical stability was assessed at different storage conditions (4°C, 25°C, and 45°C, with thermal stress of 24h at each temperature, 30days). Rheological measurements demonstrated that all SO emulsions exhibited pseudoplastic flow-type (n~0.5) liquid-like behavior (k~0.19) with the absence of storage modulus (G′) and a predominance of loss modulus (G″) even for the most concentrated emulsion (30% w/w SO), and confirmed stability regarding flocculation. The droplet size remained between 42 and 61nm (PDI inferior to 0.3). However, benzyl alcohol contributed to an increase in droplet size, while 2-methylpyrrolidone led to the smallest droplet size. BNZ showed a weak interaction with the oil phase, but stable SO in water emulsions was produced with small and uniform droplet size containing a soluble drug fraction about four times greater than its aqueous solubility.

Three-Dimensional Imaging System for Analyses of Dynamic Droplet Impaction and Deposit Formation on Leaves

<abstract><title><italic>Abstract. </italic></title> A system was developed to assess the dynamic processes of droplet impact, rebound, and retention on leaf surfaces with three-dimensional (3-D) images. The system components consisted of a uniform-size droplet generator, two high-speed digital video cameras, a constant-speed track, a leaf holder, and light sources. The droplet generator produced uniform droplets of 100 to 800 μm diameter. The video cameras captured droplet impact images from two different angle views for 3-D droplet impaction analyses. The camera speed used to capture images was up to 50,000 frames per second, with image resolution up to 1280 × 800 pixels. The constant-speed track was used to mount and drive the droplet generator at constant speeds ranging from 1.6 to 10 km h^-1. The leaf holder supported leaves at various orientations and distances from the droplet generator. Waxy and hairy leaves and water solutions amended with a non-ionic surfactant were used to verify the system functions. Five motion processes of droplets after they impacted on waxy and hairy leaf surfaces were observed: complete retention, split retention, slide retention, splash, and rebound. The droplet motion and deposition process before and after impact were quantitatively analyzed with a 3-D image program. In conclusion, the imaging system was able to precisely observe and quantitatively analyze droplet impaction and deposit formation on waxy or hairy leaves when droplet diameter, droplet discharge speed, droplet discharge height, nozzle travel speed, leaf surface orientation, and spray formulation were variables.

Differential scanning calorimetry analysis of W/O emulsions prepared by miniature scale magnetic agitation and microfluidics

AbstractUnderstanding and modelling the mechanism of destabilisation of complex and opaque water‐in‐oil emulsions is very challenging. The purpose of our current study is to develop experiments to restrict the number of destabilisation mechanisms that take place in order to better understand their role in the evolution of model emulsions. We focused particularly on the effects of droplet size increase and of droplet sedimentation, which can be observed when the emulsion ages. The evolution of the water in oil emulsion was characterised by following the displacement of the water freezing transition with time by Differential Scanning Calorimetry. We present the results obtained on two different systems: first on emulsions prepared in a miniature cell with an integrated magnetic stirrer designed for experiments on ground and under microgravity conditions (FASES program). In addition, the first results obtained with a microfluidic device, in order to generate dispersed water droplets of uniform size and determine the most probable freezing temperature of the water droplets as a function of their size, are displayed.

POTENTIAL APPLICATION OF ROSELLE EXTRACT IN FUNCTIONAL FOOD EMULSIONS [Aplikasi Ekstrak Rosela sebagai Pengemulsi pada Sistem Emulsi Pangan Fungsional

This research was undertaken to investigate the effect of Roselle (Hibiscus sabdariffa. L) extract on the physical properties and stability of extra virgin olive oil emulsions. Four different emulsions were prepared with methanolic Roselle extract (0.01 and 0.02%) and 0.02% BHT (commercial antioxidant) as well as without the extract/ antioxidant (control). The physical properties were studied in terms of pH, droplet size distribution, microstructure, viscosity and stability towards phase separation and lipid oxidation (under accelerated oxidation at 60°C for 10 days). The emulsions with Roselle extract was found to exhibit lower polydispersity and more uniform droplet size as compared to control and BHT emulsions. The highest viscosity was observed for the emulsion with 0.02%. The BHT emulsion was the most unstable towards phase separation after 15 days of storage at 5°C. A protective effect of Roselle extract against lipid oxidation in the emulsions was clearly observed at 0, 2, 8 and 10 days of accelerated storage (at 60°C) with considerably low total oxidation values (5.4 to 13). All emulsions showed insignificant deterioration with peroxide value &lt; 20 meq/kg after oxidation period. This study provided important preliminary data on possibility of applying Roselle extract (which is known to content a significant amount of bioactive compounds) in producing functional food emulsions with acceptable properties and stability. Keywords: antioxidants, emulsion, roselle extract, stability, properties

Fabrication and characteristics of Li4SiO4 pebbles by a novel capillary-based microfluidic wet process

The synthesis of Li 4 SiO 4 pebbles used as tritium breeder by a microfluidic technology was studied for the first time. C 2 H 3 O 2 Li·2H 2 O powder and SiO 2 –sol were used as the raw materials with the Li and Si molar ratio of 4. Highly uniform size droplets were formed easily in a capillary-based microfluidic device . The droplets were then converted into gel pebbles. After reaction at 750 °C for 4 h, the designated Li 4 SiO 4 pebbles were obtained. The size of as-prepared Li 4 SiO 4 pebbles can be controlled precisely in the size range from tens of micrometer to a millimeter. The obtained Li 4 SiO 4 micrometer-pebbles possess a narrow size distribution (CV = 3.9%) and favorable shape with good sphericity (1.05). The density is 82% T.D. Phase analysis, thermal analysis, morphological observation and sintering behavior of the pebbles were carried out systematically. The XRD patterns revealed that Li 4 SiO 4 were successfully obtained and the pebble’s microstructure was studied by electron beam lithography machine.

Design, Fabrication, and Characterization of Linear Multiplexed Electrospray Atomizers Micro-Machined from Metal and Polymers

Multiplexed electrospray is a promising aerosol generation technique to produce high throughput quasi-monodisperse droplets in the nanometer and micron size range. Here we report the design, fabrication, analysis, and performance of a linear electrospray (LINES) system. The fabrication of the nozzle array is based on a precision computer numerical control (CNC) micromachining platform with 1-micron resolution. This rapid prototyping approach offers the flexibility of creating devices from a wide range of materials including metals and polymers with packing densities on par with silicon microfabrication at 20 sources/cm for LINES devices and 460 sources/cm2 for the two-dimensional array. The LINES device uses a slot extractor design to simplify alignment and enhance operation robustness. We also used dummy nozzles (posts without fluidic channels) to offset edge effect on electric field and improved droplet size uniformity. We derived the approximate spray expansion model from charge conservation and Gauss’...

Alginate–lanthanide microspheres for MRI-guided embolotherapy

In cancer therapy, a promising treatment option to accomplish a high tumor-to-normal-tissue ratio is endovascular intervention with microsized particles, such as embolotherapy. In this study, alginate microspheres (ams) were prepared with the JetCutter technique, which is based on cutting a sodium alginate solution jet stream into small droplets of uniform size which are then cross-linked with different lanthanides or iron-III, resulting in microspheres of a predefined size which can be visualized by magnetic resonance imaging (MRI). The microspheres were investigated for their size and morphology (light microscopy and scanning electron microscopy analysis), cation content and MRI properties. The lanthanide-ams formulations, with a uniform size of 250μm and a cation content between 0.72–0.94%, showed promising results for MR imaging. This was further demonstrated for Ho3+-cross-linked alginate microspheres (Ho3+-ams), the most potent microsphere formulation with respect to MR visualization, allowing single sphere detection and detailed microsphere distribution examination. Intravascular infusion of Ho3+-ams by catherization of ex vivo rabbit and porcine liver tissue and assessment of the procedure with MRI clearly showed accumulation and subsequently embolization of the targeted vessels, allowing accurate monitoring of the microsphere biodistribution throughout the tissue. Therefore, the different alginate–lanthanide microsphere formulations developed in this study show great potential for utilization as image-guided embolotherapy agents.

Improved resin performance in MDF through development of blowline blending process

This paper discusses the development of a design approach for the blowline in a medium density fibreboard plant to optimise resin performance. Mass and energy flows in the refiner determine the flow in the blowline and it is necessary to determine these if the blowline is to be optimised to minimise the resin required. Once the flow in the blowline is established then the blowline sizes can be selected. These depend on the length of the blowline that is largely determined by the location of the refiner and the dryer and the number and location of bends. The other significant factor that determines the resin requirement is the initial size of the droplets sprayed into the blowline. A steam atomised nozzle has proved to be effective in the limited space and conditions in the blowline, providing a uniform droplet size over a wide flow range. The design of this nozzle has been developed to provide a further improvement in performance. Optimisation of both the blowline velocities and the resin injection nozzles is necessary to achieve the best resin result.

Rapid Generation of Multiplexed Cell Cocultures Using Acoustic Droplet Ejection Followed by Aqueous Two-Phase Exclusion Patterning

The development of tools for patterning cocultures of cells is a fundamental interest among cell biologists and tissue engineers. Although a variety of systems exist for micropatterning cells, the methods used to generate cell micropatterns are often cumbersome and difficult to adapt for tissue engineering purposes. This study combines acoustic droplet ejection and aqueous two-phase system exclusion patterning to introduce a method for patterning cocultures of cells in multiplexed arrays. This new method uses focused acoustic radiation pressure to eject discrete droplets of uniform size from the surface of a dextran solution containing cells. The size of droplets is controlled by adjusting ultrasound parameters, such as pulse, duration, and amplitude. The ejected dextran droplets are captured on a cell culture substrate that is manipulated by a computer-controlled 3D positioning system according to predesigned patterns. Polyethylene glycol solution containing an additional cell type is then added to the culture dish to produce a two-phase system capable of depositing different types of cells around the initial pattern of cells. We demonstrate that our method can produce patterns of islands or lines with two or more cell types. Further, we demonstrate that patterns can be multiplexed for studies involving combinations of multiple cell types. This method offers a tool to transfer cell-containing samples in a contact-free, nozzle-less manner, avoiding sample cross-contamination. It can be used to pattern cell cocultures without complicated fabrication of culture substrates. These capabilities were used to examine the response of cancer cells to the presence of a ligand (CXCL12) secreted from surrounding cocultured cells.

Trapping and collection of uniform size droplets for nanoparticle synthesis

This paper presents a simple and fast method for droplet trapping and collection and demonstrates nanoparticle synthesis inside these trapped droplets. Since droplet trapping is size-dependent, droplets having various sizes caused by unstable inlet flows can be eliminated. Moreover, the new droplet substitutes the previous one, so we can keep the up-to-date contents of droplets at all times. All trapped droplets can be simply collected at the outlet. We had demonstrated the synthesis of iron oxide nanoparticles inside droplets and collection of them from the device. Due to its simplicity and high efficiency for selective trapping and collection, this method can become one of the key essentials in droplet-based microfluidic assays.

Laccase mediated conjugation of sugar beet pectin and the effect on emulsion stability

Laccase catalyzes intermolecular cross-links between ferulic acid of sugar beet pectin (SBP). Conjugation of SBP by laccase was confirmed by increased molecular weight, monitored by size exclusion chromatography, combined with multi-angle laser light scattering (SEC–MALLS), by reduced ferulic acid concentration detected at UV 325 nm, as well as by increased particle size. In addition, cross-linked SBP developed a more compact, branched structure as verified by a smaller root mean square (RMS) when molecular weight increased. Emulsions prepared with conjugated SBP had significantly smaller d4,3 diameter and uniform droplet size, with more negative ζ-potential than non-treated SBP, during 30 days storage at 37 °C. The d4,3 diameter was 5.3 μm and 3.8 μm for SBP and conjugated SBP, respectively. Covalently conjugated SBP has increased functionality and improved emulsion stability, most likely attributable to development of thick layer at the oil interface.

Stirred cell membrane emulsification for multiple emulsions containing unrefined pumpkin seed oil with uniform droplet size

Stirred cell membrane emulsification was used to create double water-in-oil-in-water emulsions at the dispersed phase flux of up to 3200 L m −2 h −1. The oil phase was unrefined pumpkin seed oil or sunflower oil containing 30% by volume of internal water phase and the external water phase was 2% Tween 20 (polyoxyethylene sorbitan monolaurate) or 2% Pluronic F-68 (polyoxyethylene-polyoxypropylen copolymer). Using microengineered nickel membranes with pore sizes between 15 and 40 μm, median drop sizes of double emulsion droplets were in the range between 100 and 430 μm, depending mainly on the shear at the membrane surface and dispersed phase injection rate. In most cases the drops were very uniform, with span (i.e. 90% drop size minus 10% drop size divided by median size) values of around 0.5. This data is similar to what was obtained previously for simple O/W emulsions of the same materials. Hence, the internal water phase, and internal surfactant, 5% PGPR (polyglycerol polyricinoleate), did not adversely influence the emulsification process. A marker material, copper sulfate, was added to the internal water phase and the release of copper was monitored with respect to time. For both lipid systems, at the larger droplet size, there was a significant period of no copper release, followed by almost linear release with time. This initial period was absent when the drop size was close to 100 μm. The initial entrapment efficiency of the copper, in all experiments, was higher than 94%.

Precision Manufacture of Phase-Change Perfluorocarbon Droplets Using Microfluidics

Liquid perfluorocarbon droplets have been of interest in the medical acoustics community for use as acoustically activated particles for tissue occlusion, imaging and therapeutics. To date, methods to produce liquid perfluorocarbon droplets typically result in a polydisperse size distribution. Because the threshold of acoustic activation is a function of diameter, there would be benefit from a monodisperse population to preserve uniformity in acoustic activation parameters. Through use of a microfluidic device with flow-focusing technology, the production of droplets of perfluoropentane with a uniform size distribution is demonstrated. Stability studies indicate that these droplets are stable in storage for at least two weeks. Acoustic studies illustrate the thresholds of vaporization as a function of droplet diameter, and a logarithmic relationship is observed between acoustic pressure and vaporization threshold within the size ranges studied. Droplets of uniform size have very little variability in acoustic vaporization threshold. Results indicate that microfluidic technology can enable greater manufacturing control of phase-change perfluorocarbons for acoustic droplet vaporization applications.

Uniform-sized silicone oil microemulsions: Preparation, investigation of stability and deposition on hair surface

Emulsions are commonly used in foods, pharmaceuticals and home-personal-care products. For emulsion based products, it is highly desirable to control the droplet size distribution to improve storage stability, appearance and in-use property. We report preparation of uniform-sized silicone oil microemulsions with different droplets diameters (1.4–40.0 μm) using SPG membrane emulsification technique. These microemulsions were then added into model shampoos and conditioners to investigate the effects of size, uniformity, and storage stability on silicone oil deposition on hair surface. We observed much improved storage stability of uniform-sized microemulsions when the droplets diameter was ⩽22.7 μm. The uniform-sized microemulsion of 40.0 μm was less stable but still more stable than non-uniform sized microemulsions prepared by conventional homogenizer. The results clearly indicated that uniform-sized droplets enhanced the deposition of silicone oil on hair and deposition increased with decreasing droplet size. Hair switches washed with small uniform-sized droplets had lower values of coefficient of friction compared with those washed with larger uniform and non-uniform droplets. Moreover the addition of alginate thickener in the shampoos and conditioners further enhanced the deposition of silicone oil on hair. The good correlation between silicone oil droplets stability, deposition on hair and resultant friction of hair support that droplet size and uniformity are important factors for controlling the stability and deposition property of emulsion based products such as shampoo and conditioner.

Generation of uniform-size droplets by multistep hydrodynamic droplet division in microfluidic circuits

A microfluidic system is presented to generate multiple daughter droplets from a mother droplet, by the multistep hydrodynamic division of the mother droplet at multiple branch points in a microchannel. A microchannel network designed based on the resistive circuit model enables us to control the distribution ratio of the flow rate, which dominates the division ratios of the mother droplets. We successfully generated up to 15 daughter droplets from a mother droplet with a variation in diameter of less than 2%. In addition, we examined factors affecting the division ratio, including the average fluid velocity, interfacial tension, fluid viscosity, and the distribution ratio of volumetric flow rates at a branch point. Additionally, we actively controlled the volume of the mother droplets and examined its influence on the size of the daughter droplets, demonstrating that the size of the daughter droplets was not significantly influenced by the volume of the mother droplet when the distribution ratio was properly controlled. The presented system for controlling droplet division would be available as an innovative means for preparing monodisperse emulsions from polydisperse emulsions, as well as a technique for making a microfluidic dispenser for digital microfluidics to analyze the droplet compositions.

Generation of droplets with different concentrations using gradient-microfluidic droplet generator

This study successfully uses the micro-mixers and flow-focusing devices, which are integrated into a gradient-microfluidic droplet generator, to generate the different sizes of the droplets with different concentrations simultaneously and applies these microcapsules for drug release. The sizes of these four types of droplet with different concentrations are uniformity with a coefficient of variation less than 5% and can be precisely controlled by adjusting the water phase flow rate and oil phase flow rate. Moreover, Ca-alginate microcapsules with different concentrations of the bovine serum albumin are used for uniform size drug release, and the Ca-alginate microcapsule size is from 60 to 105 μm in diameter. This developed microfluidic chip has the advantages of actively controlling the droplet diameter, simultaneously generating uniform-sized droplets with different concentrations, and having a simple process and a high throughput. This preparation approach for Ca-alginate microcapsules of four different concentrations will provide many potential applications for drug delivery and pharmaceutical area.

Fabrication of poly(methyl methacrylate) micro-droplets using a complex electric field on a rolling collector

Electrospraying was used to fabricate micro-sized droplets of various polymers using strong electric fields. For the mass production of poly (methylmethacrylate) droplets and more uniform-sized droplets than the normal electrospray process, an AC electric field was applied to the rolling collector in a normal electrospray process to provide an additional external force. The droplets were placed in an additional dispersion on the rolling collector due to the AC field conditions, resulting in the formation of smaller and more uniform-sized droplets.

Compact multiplexing of monodisperse electrosprays

Widespread application of the cone-jet electrospray has been hampered by the low flow rate at which the spray is dispersed, despite the unique ability of this device to disperse quasi-monodispersed particles over a phenomenal size range. Compact multiplexing, that is, with a high number of sources per unit area, is indispensable for dramatically increasing the throughput and reducing the cost per electrospray source. We demonstrate the successful operation of multiplexed electrospray systems with an unprecedented packing density of up to 11,547 sources/cm 2. The devices were fabricated and operated by implementing three criteria: (a) the extractor electrode configuration should be used to localize the electric field; (b) the viscous pressure drop acting on the liquid should dominate with respect to the electrostatic pulling force by the electric field; and (c) the electric field “driving” the droplets between the extractor electrode and the collector should be sufficiently intense to avoid reversal of the droplet motion near the extractor (satellite trapping). All devices showed excellent droplet size uniformity across the entire spray region, which indicates effective decoupling of the electrospray sources even for closely packed nozzles. The experimental results show that these design criteria provide effective and reliable guidelines for the successful design and operation of multiplexed devices from first principles, that is, based only on knowledge of the suitability of a liquid for electrospray dispersion and of the critical liquid properties such as surface tension, viscosity and electric conductivity. As a result, the design of these devices for a given application is achievable without costly trial-and-error microfabrication trials. This development opens the door for applications requiring flows from multiplexing 10 6–10 7 individual electrospray sources from industry-standard 12-in silicon wafers.

208 円管から流出する液体の均一液滴流形成特性(流体工学II)

208 円管から流出する液体の均一液滴流形成特性(流体工学II)

Some Aids to Histological Recognition of Hyaline Droplet Nephropathy in Ninety-Day Toxicity Studies

Although it has long been known that young male rats of conventional strains have a well-developed contingent of hyaline droplets in the P2 segment of proximal tubule representing secondary lysosomes (Logothetopoulos and Weinbren 1955; Maunsbach 1966), it seems not to have been generally recognized that the droplets assume a specific pattern in control males (at least in threeto five-month-old males) that is disrupted after treatment with chemicals inducing α2u-g nephropathy. The difference between this control male rat pattern and the renal response to an α2u-g-binding chemical is best determined using a protein stain such as Mallory Heidenhain (MH) or fluorescence microscopy. Chromotropeaniline-blue (CAB) stain has been recommended as well for detecting hyaline droplets (de Rijk et al. 2003). Young adult male rats normally have cytoplasmic droplets in PCT cells distributed in irregular tracts running from the deep cortex into the outer cortex (Figure 1a). This distribution probably traces the course of the P2 segments of proximal tubule (Goldsworthy et al. 1988). There is a distinct pattern in the distribution of the droplets within tubule cells. Some epithelial lining cells have a dense intracytoplasmic accumulation of droplets of uniform size, particularly filling the apical region. Other tubules have cells with a sparser, random scatter of intracellular droplets of various sizes, but the droplets are usually small (Figure 1b). In each case, the droplets have distinctly rounded outlines, and a crystal-like angular profile is seen only rarely. The cells densely crowded with droplets appear to bulge into the tubule lumen (Figure 1c), and are referred to here as “droplet-congested” (D-C) tubule cells for convenience. D-C tubule cells are scattered through the irregular tracts of droplets in the cortex but are particularly noticeable in the deep cortex. It appears that Uwagawa et al. (1992) referred to these D-C tubule cells as an “eosinophilic body type” of hyaline droplet, but most important, they showed that these cells (along with the scattered intracytoplasmic droplets in adjoining PCTs) were densely positive for anti-α2u-g immunohistochemical staining, confirming the droplets as lysosome related. INTRODUCTION