Monodisperse non-Newtonian micro-droplet generation in a co-flow device (original) (raw)
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Flow rate effect on droplet control in a co-flowing microfluidic device
Flow rate effect on droplet formation in a co-flowing microfluidic device is investigated numerically. Transition conditions are discovered that the droplet size is either approximately independent of or strongly dependent on the flow rate ratio. This phenomenon is explained by the relation between strain rate and droplet diameter. Regions of four drop patterns are demarcated and conditions that give poly-disperse drops are described, which is helpful to assure the accuracy and efficiency in droplet production. Keywords Microdroplet Á Monodisperse Á Flow rate effect Á Droplet patterns Á Co-flowing system
Numerical Simulation of Droplet Breakup, Splitting and Sorting in a Microfluidic Device
Droplet generation, splitting and sorting are investigated numerically in the framework of a VOF technique for interface tracking and a finite-volume numerical method using the commercial code FLUENT. Droplets of water-in-oil are produced by a flow focusing technique relying on the use of a microchannell equipped with an obstacle to split the droplets. The influence of several parameters potentially affecting this process is investigated parametrically towards the end of identifying "optimal" conditions for droplet breakup. Such parameters include surface tension, the capillary number and the main channel width. We show that the capillary number plays a crucial role in determining droplet properties and the efficiency of the related generation process. An obstacle configuration can be effectively used to split a droplet, with the droplets being naturally sorted at the end of the main channel. Larger values of the capillary number generally lead to an increase in the droplet frequency and a decrease in its typical size.
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A microfluidic device designed to generate monodispersed picoliter to femtoliter sized droplet emulsions at controlled rates is presented. This PDMS microfabricated device utilizes the geometry of the channel junctions in addition to the flow rates to control the droplet sizes. An expanding nozzle is used to control the breakup location of the droplet generation process. The droplet breakup occurs at
Lab on a Chip, 2004
Passive microfluidic channel geometries for control of droplet fission, fusion and sorting are designed, fabricated, and tested. In droplet fission, the inlet width of the bifurcating junction is used to control the range of breakable droplet sizes and the relative resistances of the daughter channels were used to control the volume of the daughter droplets. Droplet fission is shown to produce concentration differences in the daughter droplets generated from a primary drop with an incompletely mixed chemical gradient, and for droplets in each of the bifurcated channels, droplets were found to be monodispersed with a less than 2% variation in size. Droplet fusion is demonstrated using a flow rectifying design that can fuse multiple droplets of same or different sizes generated at various frequencies. Droplet sorting is achieved using a bifurcating flow design that allows droplets to be separated base on their sizes by controlling the widths of the daughter channels. Using this sorting design, submicron satellite droplets are separated from the larger droplets. † Lab on a Chip special issue: The Science and Application of Droplets in Microfluidic Devices.
Microfluidic Droplet Manipulations and Their Applications
Droplet microfluidics" enables the manipulation of discrete fluid packets in the form of microdroplets that provide numerous benefits for conducting biological and chemical assays. Among these benefits are a large reduction in the volume of reagent required for assays, the size of sample required, and the size of the equipment itself. Such technology also enhances the speed of biological and chemical assays by reducing the volumes over which processes such as heating, diffusion, and convective mixing occur. Once the droplets are generated, carefully designed droplet operations allow for the multiplexing of a large number of droplets to enable large-scale complex biological and chemical assays. In this chapter, four major unit operations in droplets are discussed: droplet fusion, droplet fission, mixing in droplets, and droplet sorting. Combined, these operations allow for much complexity in executing chemical reactions and biological assays at the microscale. A broad overview of potential applications for such technology is provided throughout. While much research effort has been focused on the development of these individual devices, far fewer attempts to integrate these components have been undertaken. A review of many microfluidic unit operation devices is provided here, along with the advantages and disadvantages of each approach for various applications.