Spontaneous Droplet Research Articles

エマルションの最前線 マイクロチャネル乳化技術の開発

Microchannel (MC) arrays with various shapes and sizes were micro-fabricated using a single-crystal silicon substrate. An emulsion is prepared by simply forcing dispersed phase fluid into continuous phase fluid through the MC. Real-time optical observations of the emulsification process can be realized with a microscope video system. The grooved type MC and module were used to characterize MC emulsification, and straight-through MC and module were developed for higher productivity. O/W-emulsions can be obtained due to its hydrophilic surface property after MC oxidation. Hydrophobic MC modified by silanization can be also applicable to W/O-emulsions. Both monodisperse O/W-and W/O-emulsions with average droplets sizes ranging 3-90 p m and coefficients of variations lower than 10% have been successfully obtained. Emulsification was significantly affected by MC sizes and structures. Analysis by high-speed camera revealed that the structure of terrace is so important for instability at the outlet, and spontaneous droplet formation caused by interfacial tension. An oblong straight-through MC was highly applicable to emulsification. MC emulsification was also applied to productions of solid-lipid and polymeric microsheres, and microcapsules, showing high availability. The MC emulsification technology has great potential for food, pharmaceutical and chemical industries.

Characterization of Spontaneous Transformation-Based Droplet Formation during Microchannel Emulsification

Recently, we proposed a microchannel (MC) emulsification technique, which is a novel method for making a monodispersed emulsion from a microfabricated channel array. The droplet formation mechanism for MC emulsification is a unique one, in which the distorted dispersed phase is spontaneously transformed into spherical droplets by interfacial tension. The objective of this study was to characterize the flow in MC emulsification. We investigated the emulsification behavior at different flow velocities of the dispersed phase using MCs with different sizes and analogous shapes and found a critical flow velocity over which the character of flow changed drastically. The formed droplet diameters were almost constant below the critical velocity, and monodispersed emulsions were formed. The droplet diameters increased drastically above the critical velocity, and polydispersed emulsions were formed. The critical velocities were independent of MC size. Analysis using a dimensionless number revealed that the critical...

Droplet motion induced by diffusion of soluble surfactant to the external medium : Experiment

Experimental examinations were performed for the motion of liquid droplets suspended under the condition of neutral buoyancy (Plateau technique) in the second liquid in the presence of surfactant transfer from droplets to the surrounding liquid or surfactant transfer to the droplet from the external medium. It was shown that, at a certain initial surfactant concentration, spontaneous droplet motion arises, which has the oscillation character. When the initial concentration exceeds a certain critical value, almost steady-state translational droplet motion occurs in addition to oscillation displacements. In the case of surfactant transfer from the surrounding liquid to the droplet, only oscillation displacements of a droplet with larger amplitude take place.

Non-equilibrium dynamics in 3d spin glasses

The random spin structure of a quenched spin glass experiences a continuous re-structuring in the low-temperature spin glass phase; the spin glass ages. Some recent experimental studies of relaxation and temperature dependence of the low-frequency AC-susceptibility and DC-magnetisation have given essential new information on which are the governing physical parameters for the spontaneous re-construction of the spin configuration. These results are briefly reviewed and put into the context of a phenomenological real space picture of the spin glass phase. This picture includes: domains of spin glass ordered regions that use spontaneous droplet excitations as the only mechanism for their growth at constant temperature, chaos with temperature and overlap on short length scales between the equilibrium states at two different temperatures.

Direct observation of spontaneous emulsification and associated interfacial phenomena at the slag–steel interface

Interfacial tension decreases drastically when an intense chemical reaction occurs at a steelslag interface. This phenomenon results in spontaneous droplet spreading during the initial period of re...

Novel techniques for iol/water separation

In this work two novel methods of separation of oil/water dispersions are proposed. In both methods wetting plays an essential role. It has been found that during the flow of a dispersion through thin microporous hydrophobic membranes with pore size similar to drop size, a spontaneous droplet enlargement takes place. This was manifested by very fast gravitational phase separation after one passage of the dispersion through the membrane. The fraction of separated oil was independent of initial oil concentration and also independent in a broad range from the flow rates. As an alternative to the gravitational separators, the enlarged droplets can be removed using hollow fiber modules. The dispersion is led through the lumen of the hollow fibers, the oil phase permeates through the porous membrane. A simplified mechanism is proposed to explain the influence of residence time and flow rate on the efficiency of the hollow fiber separation.

D-Limonene Induced Hyaline Droplet Nephropathy in α2u-Globulin Transgenic Mice

d-Limonene Induced Hyaline Droplet Nephropathy in α2u-Globulin Transgenic Mice. Lehmian-McKeeman, L. D., and Caudill, D. (1994). Fundam. Appl. Toxicol. 23, 562-568. d-Limonene is a hyaline droplet inducing agent and produces nephrotoxicity in male rats when the 1,2 epoxide metabolite binds to α2u-globulin. Mice, which do not synthesize α2u-globulin, are resistant to hyaline droplet nephropathy. In this study, the ability of d -limonene to cause hyaline droplet nephropathy in a transgenic mouse engineered to express α2u-globulin was evaluated. The C57BL/6 derived mice excreted 0.4 ± 0.1 mg α2u-globulin/day, or approximately 16 mg α2u-globulin/kg body wt. This represents about 30% or the amount excreted by adult male rats (11.9 ± 1.1 mg/day or approximately 48 mg/kg). Transgenic mice excreted less mouse urinary protein (9.3 ± 1.2 mg/day) than normal mice (15.1± 1.6 mg/day). Unlike normal male rats, untreated transgenic mice did not show significant spontaneous hyaline droplet formation. Liver microsomes from naive transgenic mice oxidized d -limonene to the cis- and trans-isomers of the 1,2-epoxide, and following oral treatment with [ 14C] d-limonene reversible binding of d-limonene equivalents to renal cytosolic proteins was observed. Furthermore, with d -limonene treatment, hyaline droplets were observed in the transgenic mouse kidneys. These droplets, however, were much smaller in size than those seen in d-limonene-treated male rats. The accumulation of α2u-globulin in the kidneys of transgenic mice and normal male rats before and after d-limonene treatment was analyzed by Western blotting. These results indicated that α2u-globulin was present in the kidneys of the control transgenic mice, despite the lack of spontaneous hyaline droplet formation. After d-limonene treatment, approximately a threefold increase in α2u-globulin in the transgenic mouse kidney was observed, a response similar in magnitude to that seen in d-limonene-treated male rats. These results indicate that expression of α2u-globulin in a species that does not normally develop hyaline droplet nephropathy is necessary and sufficient to render that species sensitive to this renal toxicity.

Characterization of spontaneous and decalin-induced hyaline droplets in kidneys of adult male rats

Studies were conducted to gain additional information about the spontaneous and decalin-exacerbated formation of hyaline droplets within the cytoplasm of proximal convoluted tubule (PCT) epithelial cells of the adult male rat. Renal cortical tissue protein patterns determined through two-dimensional gel electrophoresis revealed four species of a low-molecular-weight protein (18,000–20,000 daltons). Treatment groups differed only with respect to this protein, the relative concentrations of which paralleled the numbers of hyaline droplets in mature treated and untreated male rats. The increase in the numbers of hyaline droplets and protein accumulation were dose related. Neither this protein nor hyaline droplets were detected in the renal cortical tissues of untreated or decalin-exposed adult female or immature male control rats. However this protein, and hyaline droplet formation, could be induced in the kidneys of adult, ovariectomized female rats by repeated testosterone injections. This protein was then demonstrated to be immunologically identical to alpha 2u-globulin, a protein synthesized by hepatic parenchymal cells. Alpha 2u-globulin protein has also been shown to be the major urinary component responsible for the proteinuria routinely observed in normal control adult male rats. PCT epithelial cell reabsorption and lysosomal accumulation of alpha 2u-globulin, reflected morphologically as hyaline droplets, occurs spontaneously only in the mature male rat. Decalin, a model compound, exacerbates this accumulation as a specific integral step in the pathogenesis of the nephropathy induced in male rats by volatile hydrocarbons. Hence, since men and women lack this specific PCT cell peculiarity, they would not be expected to respond to decalin exposure in a manner similar to the male rat.

Spontaneous droplet nucleation in clean, saturated moist air at atmospheric pressure

Steaming (droplet formation) above the surface of liquid water that is being heated can first be observed at about 50 degrees C under normal atmospheric conditions. The droplets have been presumed by previous observers to form on condensation nuclei that are always present due to impurities in atmospheric air. But simple experiments, reported here, show that droplet nucleation apparently can occur spontaneously with warming, beginning at about 50 degrees C, even in purified saturated air at atmosphere pressure that is free of nuclei other than water clusters. The observations suggest new ideas about structure in water vapour. A critical cluster size of about 45 can explain observations over a wide range of temperatures and water vapour partial pressures.