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Capillary Number - Christopher Sparages: Difference between revisions
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Droplet formation is controlled by the formation and deformation of the liquid-liquid interface between the two immiscible phases. There are many forces which acts on droplet formation, but the most prominent among them is the capillary number.<ref name="ten">Jeong, S. (2005). Evaluation of the use of capillary numbers for quantifying the removal of DNAPL trapped in a porous medium by surfactant and surfactant foam floods. Journal of Colloid and Interface Science, 282(1), 182-187. https://dx.doi.org/10.1016/j.jcis.2004.08.108</ref> The capillary number represents the ratio of viscosity to interfacial tension and with an increase in capillary number, there is a decrease in droplet diameter.<ref name="fourteen">Tice, J. D., Lyon, A. D., & Ismagilov, R. F. (2004). Effects of viscosity on droplet formation and mixing in microfluidic channels. Analytica Chimica Acta, 507(1), 73-77. https://dx.doi.org/10.1016/j.aca.2003.11.024</ref> To be more specific, spherical droplets form at low capillary values and long liquid plugs at high capillary values ([[Droplet_Microfluidics:_T-Junction_-_Lina_Wu |Droplet Microfluidics: T-Junction]]). | Droplet formation is controlled by the formation and deformation of the liquid-liquid interface between the two immiscible phases. There are many forces which acts on droplet formation, but the most prominent among them is the capillary number.<ref name="ten">Jeong, S. (2005). Evaluation of the use of capillary numbers for quantifying the removal of DNAPL trapped in a porous medium by surfactant and surfactant foam floods. Journal of Colloid and Interface Science, 282(1), 182-187. https://dx.doi.org/10.1016/j.jcis.2004.08.108</ref> The capillary number represents the ratio of viscosity to interfacial tension and with an increase in capillary number, there is a decrease in droplet diameter.<ref name="fourteen">Tice, J. D., Lyon, A. D., & Ismagilov, R. F. (2004). Effects of viscosity on droplet formation and mixing in microfluidic channels. Analytica Chimica Acta, 507(1), 73-77. https://dx.doi.org/10.1016/j.aca.2003.11.024</ref> To be more specific, spherical droplets form at low capillary values and long liquid plugs at high capillary values ([[Droplet_Microfluidics:_T-Junction_-_Lina_Wu |Droplet Microfluidics: T-Junction]]). | ||
Squeezing, dripping, and jetting are other events that occur in droplet microfluidics. In the case of squeezing mode, low capillary numbers are used to produce droplets, in doing so a pressure gradient is formed across the droplet upon being formed. They droplets travel as plugs. In the case of dripping mode, viscous shear stress and interfacial tension compete as the capillary number increases with flow rate and the droplet fluid is broken up along its pathway through the channel. The droplets travel as small drips. Lastly, by increasing the capillary number and forces farther jetting occurs, resulting in droplets traveling as either spheres or plugs ([[Droplet_Microfluidics:_T-Junction_-_Lina_Wu |Droplet Microfluidics: T-Junction]]).<ref name="eight">Ralf Seemann et al. (2012). Droplet Based Microfluidics. Reports on Progress in Physics | Squeezing, dripping, and jetting are other events that occur in droplet microfluidics. In the case of squeezing mode, low capillary numbers are used to produce droplets, in doing so a pressure gradient is formed across the droplet upon being formed. They droplets travel as plugs. In the case of dripping mode, viscous shear stress and interfacial tension compete as the capillary number increases with flow rate and the droplet fluid is broken up along its pathway through the channel. The droplets travel as small drips. Lastly, by increasing the capillary number and forces farther jetting occurs, resulting in droplets traveling as either spheres or plugs ([[Droplet_Microfluidics:_T-Junction_-_Lina_Wu |Droplet Microfluidics: T-Junction]]).<ref name="eight">Ralf Seemann et al. (2012). Droplet Based Microfluidics. Reports on Progress in Physics, 75(1), 16-60. https://dx.doi.org/10.1088/0034-4885/75/1/016601</ref> | ||
===Capillary Valving=== | ===Capillary Valving=== | ||
