Generation of Chemical Concentration Gradients in Mobile Droplet Arrays via Fragmentation of Long Immiscible Diluting Plugs

We report a one-step passive microfluidic technique to generate arrays of moving droplets containing variation of chemical concentration between individual drops. We find that a concentration gradient can be established in a long diluting plug by on-chip dilution and extraction of samples via orthogonal coalescence of the plug with a static array of sample drops. The diluting plug containing the gradient is subsequently fragmented by a droplet generator. We show that the technique is flexible, as the dilution range can be tuned by a variety of control parameters including the carrier fluid flow rate, volume of diluting plugs, and stationary drops. We also find that the concentration gradients have a fine resolution and are reproducible to within 2% relative standard deviation. As one demonstrative application, we show the suitability of the technique for generating a dose-response curve for an enzyme inhibition assay. Because of the ability to inject multiple plugs, our technique has the potential for unlimited as well as sequential dilution of a series of substrates. Thus, our method could be valuable as a high-throughput and high-resolution screening tool for assays that require interrogation of the response of one or more target species to numerous distinct chemical concentrations

Generation of Chemical Concentration Gradients in Mobile Droplet Arrays via Fragmentation of Long Immiscible Diluting Plugs

We report a one-step passive microfluidic technique to generate arrays of moving droplets containing variation of chemical concentration between individual drops. We find that a concentration gradient can be established in a long diluting plug by on-chip dilution and extraction of samples via orthogonal coalescence of the plug with a static array of sample drops. The diluting plug containing the gradient is subsequently fragmented by a droplet generator. We show that the technique is flexible, as the dilution range can be tuned by a variety of control parameters including the carrier fluid flow rate, volume of diluting plugs, and stationary drops. We also find that the concentration gradients have a fine resolution and are reproducible to within 2% relative standard deviation. As one demonstrative application, we show the suitability of the technique for generating a dose-response curve for an enzyme inhibition assay. Because of the ability to inject multiple plugs, our technique has the potential for unlimited as well as sequential dilution of a series of substrates. Thus, our method could be valuable as a high-throughput and high-resolution screening tool for assays that require interrogation of the response of one or more target species to numerous distinct chemical concentrations

Microfluidic Production of Spherical and Nonspherical Fat Particles by Thermal Quenching of Crystallizable Oils

We report the microfluidic production of spherical and nonspherical fat particles from crystallizable oils. The method is based on microfluidic generation of oil droplets at a cross-junction followed by thermal solidification downstream in a microcapillary. We vary the drop production conditions and the device temperature and demonstrate that the size, shape, and crystallinity can be controlled. By measuring thermal gradients in the microcapillary, we show that crystalline fat particles are best produced when the device temperature is below the onset temperature of bulk fat crystallization. To produce monodisperse nonspherical fat particles, we find that the carrier fluid flow rate needs to be sufficiently high to provide strong hydrodynamic forces to transport the confined rod-like particles. We identify the scaling relationship between geometric confinement and particle elasticity necessary to maintain the nonspherical shape. Thus, our study provides guidelines for the production of spherical and nonspherical fat particles that can be potentially used for controlling microstructure, rheology, and drug encapsulation in foods, cosmetics, and pharmaceutical creams that employ crystallizable oils

Generation of Chemical Concentration Gradients in Mobile Droplet Arrays via Fragmentation of Long Immiscible Diluting Plugs

We report a one-step passive microfluidic technique to generate arrays of moving droplets containing variation of chemical concentration between individual drops. We find that a concentration gradient can be established in a long diluting plug by on-chip dilution and extraction of samples via orthogonal coalescence of the plug with a static array of sample drops. The diluting plug containing the gradient is subsequently fragmented by a droplet generator. We show that the technique is flexible, as the dilution range can be tuned by a variety of control parameters including the carrier fluid flow rate, volume of diluting plugs, and stationary drops. We also find that the concentration gradients have a fine resolution and are reproducible to within 2% relative standard deviation. As one demonstrative application, we show the suitability of the technique for generating a dose-response curve for an enzyme inhibition assay. Because of the ability to inject multiple plugs, our technique has the potential for unlimited as well as sequential dilution of a series of substrates. Thus, our method could be valuable as a high-throughput and high-resolution screening tool for assays that require interrogation of the response of one or more target species to numerous distinct chemical concentrations

Generation of Chemical Concentration Gradients in Mobile Droplet Arrays via Fragmentation of Long Immiscible Diluting Plugs

We report a one-step passive microfluidic technique to generate arrays of moving droplets containing variation of chemical concentration between individual drops. We find that a concentration gradient can be established in a long diluting plug by on-chip dilution and extraction of samples via orthogonal coalescence of the plug with a static array of sample drops. The diluting plug containing the gradient is subsequently fragmented by a droplet generator. We show that the technique is flexible, as the dilution range can be tuned by a variety of control parameters including the carrier fluid flow rate, volume of diluting plugs, and stationary drops. We also find that the concentration gradients have a fine resolution and are reproducible to within 2% relative standard deviation. As one demonstrative application, we show the suitability of the technique for generating a dose-response curve for an enzyme inhibition assay. Because of the ability to inject multiple plugs, our technique has the potential for unlimited as well as sequential dilution of a series of substrates. Thus, our method could be valuable as a high-throughput and high-resolution screening tool for assays that require interrogation of the response of one or more target species to numerous distinct chemical concentrations

Microfluidic Production of Spherical and Nonspherical Fat Particles by Thermal Quenching of Crystallizable Oils

We report the microfluidic production of spherical and nonspherical fat particles from crystallizable oils. The method is based on microfluidic generation of oil droplets at a cross-junction followed by thermal solidification downstream in a microcapillary. We vary the drop production conditions and the device temperature and demonstrate that the size, shape, and crystallinity can be controlled. By measuring thermal gradients in the microcapillary, we show that crystalline fat particles are best produced when the device temperature is below the onset temperature of bulk fat crystallization. To produce monodisperse nonspherical fat particles, we find that the carrier fluid flow rate needs to be sufficiently high to provide strong hydrodynamic forces to transport the confined rod-like particles. We identify the scaling relationship between geometric confinement and particle elasticity necessary to maintain the nonspherical shape. Thus, our study provides guidelines for the production of spherical and nonspherical fat particles that can be potentially used for controlling microstructure, rheology, and drug encapsulation in foods, cosmetics, and pharmaceutical creams that employ crystallizable oils

Microfluidic Production of Spherical and Nonspherical Fat Particles by Thermal Quenching of Crystallizable Oils

We report the microfluidic production of spherical and nonspherical fat particles from crystallizable oils. The method is based on microfluidic generation of oil droplets at a cross-junction followed by thermal solidification downstream in a microcapillary. We vary the drop production conditions and the device temperature and demonstrate that the size, shape, and crystallinity can be controlled. By measuring thermal gradients in the microcapillary, we show that crystalline fat particles are best produced when the device temperature is below the onset temperature of bulk fat crystallization. To produce monodisperse nonspherical fat particles, we find that the carrier fluid flow rate needs to be sufficiently high to provide strong hydrodynamic forces to transport the confined rod-like particles. We identify the scaling relationship between geometric confinement and particle elasticity necessary to maintain the nonspherical shape. Thus, our study provides guidelines for the production of spherical and nonspherical fat particles that can be potentially used for controlling microstructure, rheology, and drug encapsulation in foods, cosmetics, and pharmaceutical creams that employ crystallizable oils

Generation of Chemical Concentration Gradients in Mobile Droplet Arrays via Fragmentation of Long Immiscible Diluting Plugs

We report a one-step passive microfluidic technique to generate arrays of moving droplets containing variation of chemical concentration between individual drops. We find that a concentration gradient can be established in a long diluting plug by on-chip dilution and extraction of samples via orthogonal coalescence of the plug with a static array of sample drops. The diluting plug containing the gradient is subsequently fragmented by a droplet generator. We show that the technique is flexible, as the dilution range can be tuned by a variety of control parameters including the carrier fluid flow rate, volume of diluting plugs, and stationary drops. We also find that the concentration gradients have a fine resolution and are reproducible to within 2% relative standard deviation. As one demonstrative application, we show the suitability of the technique for generating a dose-response curve for an enzyme inhibition assay. Because of the ability to inject multiple plugs, our technique has the potential for unlimited as well as sequential dilution of a series of substrates. Thus, our method could be valuable as a high-throughput and high-resolution screening tool for assays that require interrogation of the response of one or more target species to numerous distinct chemical concentrations

Microfluidic Production of Spherical and Nonspherical Fat Particles by Thermal Quenching of Crystallizable Oils

We report the microfluidic production of spherical and nonspherical fat particles from crystallizable oils. The method is based on microfluidic generation of oil droplets at a cross-junction followed by thermal solidification downstream in a microcapillary. We vary the drop production conditions and the device temperature and demonstrate that the size, shape, and crystallinity can be controlled. By measuring thermal gradients in the microcapillary, we show that crystalline fat particles are best produced when the device temperature is below the onset temperature of bulk fat crystallization. To produce monodisperse nonspherical fat particles, we find that the carrier fluid flow rate needs to be sufficiently high to provide strong hydrodynamic forces to transport the confined rod-like particles. We identify the scaling relationship between geometric confinement and particle elasticity necessary to maintain the nonspherical shape. Thus, our study provides guidelines for the production of spherical and nonspherical fat particles that can be potentially used for controlling microstructure, rheology, and drug encapsulation in foods, cosmetics, and pharmaceutical creams that employ crystallizable oils

Body posture of <i>C. elegans</i> with two distinct piecewise-curvature modes.

<p>(A) The experimental image of the worm. (B) The skeleton data (open circles) and the harmonic-curvature fit for the tail segment (solid line). The extension of the fit that does not follow the head segment is shown by dashed line, and the point where the piecewise-curvature mode changes is indicated by a filled circle. (C) The best fit of the two-mode harmonic-curvature representation (8) (solid line). Since the line is obtained by integrating second-order differential equations (6), it is continuous and has a continuous slope. The insets in (B) and (C) show the local fit error (17) along the skeleton of the nematode. For the single-curvature-mode fit (B) the error rapidly increases after the point indicated by the filled circle, whereas for the continuous two-mode fit (C), the local error is below 1% along the whole body.</p