Controlled generation of submicron emulsion droplets via highly stable tip-streaming mode in microfluidic devices

Abstract

Submicron emulsions could be produced via the tip-streaming process in a flow-focusing microfluidic device. In this article, the stability of the liquid cone and thread for tip-streaming mode could be significantly improved by employing a three-dimensional flow-focusing device, in which the hydraulic resistance was adjusted by modulating the channel heights in the flow focusing area, orifice, downstream and dispersed phase inlet channel. The pressure range for tip-streaming mode was enlarged significantly compared with two-dimensional flow-focusing devices. Therefore, monodisperse emulsions were produced under this tip-streaming mode for as long as 48 hours. Furthermore, we could control the size of emulsion drops by changing the pressure ratio in three-dimensional flow-focusing devices while the liquid cone was easily retracted during the adjustment of pressure ratio in two-dimensional flow-focusing devices. Furthermore, using the uniform submicron emulsion droplets as confining templates, polyethylene glycol (PEG) particles were produced with a narrow size distribution at the sub-micrometre scale. In addition, magnetic nanoparticles were added to the emulsion for magnetic PEG particles, which can respond to magnetic field and would be biocompatible.

Local interfacial stability near a zero vorticity point

“…This arrangement, referred to as flow focusing, has recently become the object of intense research in view of its importance for many microfluidic applications; see e.g. Basaran (2002), Anna, Bontoux & Stone (2003), Barrero & Loscertales (2007), Marín, Campo-Cortés & Gordillo (2009), Jeong et al (2012).…”

Controllable microfluidic strategies for fabricating microparticles using emulsions as templates

“…Generally, the size ranges, monodispersity, and throughput of the resultant microparticles depend on those of the emulsion templates (Jeong et al, 2012;Nisisako & Torii, 2008;Steinbacher et al, 2012). Because of the excellent droplet manipulation of microfluidics and the transparency of the microchannel materials, flexible synthesis strategies such as solidifications based on solvent evaporation and temperature-cooling (Sun, Shum, Holtze, & Weitz, 2010), and polymerizations triggered by UV-irradiation and chemicals Liu et al, 2011), can be applied to achieve fabrication of particles using emulsions as templates.…”

“…Because the units produce one droplet at a time, accurate control over the droplet size and size distribution can be achieved. Typically, microfluidic techniques can produce monodisperse emulsion droplets with sizes ranging from millimeter - (Steinbacher et al, 2012) to micrometer - (Shah, Shum et al, 2008) or even submicrometer-scale (Jeong et al, 2012), with a coefficient of variation (CV) for droplet size of less than 5%. The physical properties of different fluids, geometries of the microfluidic device, and processing conditions are all important factors for controlling droplet formation.…”

Three-Dimensional Electro-Sonic Flow Focusing Ionization Microfluidic Chip for Mass Spectrometry

“…Alternatively, the three-dimensional (3D) microfluidic FF chip, in which the dispersed phase was suspended in the continuous phase without contacting the micro-channel wall, can guarantee the formation of extensional flow. This 3D microfluidic FF chip is suitable for applications with low viscosity ratios, such as generating submicron emulsion droplets and cell counting [49,60,61] and high viscosity ratios. Although the 3D microfluidic FF chip was recently implemented by Trebbin et al [62] at a high viscosity ratio to produce liquid jets and droplets, we conceived and designed a similar 3D microfluidic FF chip independently and differently.…”