We experimentally study the viscous fingering instability in a fluid-fluid phase separated colloid-polymer mixture by means of laser scanning confocal microscopy and microfluidics. We focus on three aspects of the instability. (i) The interface between the two demixed phases has an ultralow surface tension, such that we can address the role of thermal interface fluctuations. (ii) We image the interface in three dimensions allowing us to study the interplay between interface curvature and flow. (iii) The displacing fluid wets all walls completely, in contrast to traditional viscous fingering experiments, in which the displaced fluid wets the walls. We also perform lattice Boltzmann simulations, which help to interpret the experimental observations.
Understanding fluid dynamics under extreme confinement, where device and intrinsic fluid length scales become comparable, is essential to successfully develop the coming generations of fluidic devices. Here we report measurements of advancing fluid fronts in such a regime, which we dub superconfinement. We find that the strong coupling between contact-line friction and geometric confinement gives rise to a new stability regime where the maximum speed for a stable moving front exhibits a distinctive response to changes in the bounding geometry. Unstable fronts develop into drop-emitting jets controlled by thermal fluctuations. Numerical simulations reveal that the dynamics in superconfined systems is dominated by interfacial forces. Henceforth, we present a theory that quantifies our experiments in terms of the relevant interfacial length scale, which in our system is the intrinsic contact-line slip length. Our findings show that length-scale overlap can be used as a new fluid-control mechanism in strongly confined systems.
More than half of the reported new discovered/invented drugs are ones with poor solubility, absorption or both. These are the crucial issues that can affect the bioavailability of the drugs. Therefore, improving solubility of poor-soluble drugs is absolutely important. One of the methods to solubilize them in biological fluids is using surfactants. Surfactants are an amphiphilic organic compound containing hydrophilic and lipophilic parts that allow it to reduce the surface tension between two opposite polar phases. Several popular methods used to determine critical micelle concentration which includes surface tension, conductivity and UV-vis spectroscopy. These surfactants plays number of roles in antibacterial compound synthesis include size reduction agent, stabilizer, solubilizer and drug-carrier. This review will also critically discuss on the roles of surfactants in antibacterial compound synthesis/production and its effect on the antibacterial activity of the drugs.
Interest and demand for bacterial pigments is growing due to rising awareness of toxicity of synthetic dyes. This study evaluated on the production of flexirubin-type pigment from Chryseobacterium artocarpi CECT 8497 using liquid pineapple waste in 5-L bioreactor and its application as environmental-friendly ink. Liquid pineapple waste supported bacterial growth and pigment production for C. artocarpi CECT 8497. The ink was successfully formulated with polyvinyl butyral and polyvinyl pyrrolidone giving a smooth texture. The functional groups of formulated ink identified using FTIR were OH, C-C and C-H. Flexirubin ink was stable during the entire storage period of 30 days at temperatures, ranging from 25 to 70°C, pH 1.0 to 11.0 and in the presence and absence of light. This is the first report on ink formulation of flexirubin-type pigment from C. artocarpi CECT 8497 and its potential application on plastic materials.
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