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Emission modes in electro co-flow
Josefa Guerrero and Alberto Fernandez-Nieves
We use glass-based microfluidic devices to study the emission regimes in electro co-flow. In contrast to classical electrospray, in electro-coflow a liquid is ejected through a nozzle into another co-flowing liquid. As a result, additional parameters provide control over the emission; these include the viscosity and flow rate of the outer co-flowing liquid. Below you can see a sketch of the experimental setup [1].
In electro-coflow, depending on the inner and outer flow rates as well as the applied voltage, we can observe different emission modes: electro-dripping, microdripping, spindle, cone-jet and whipping modes, among others. Some of then have been described in a liquid – air interface, and others are specific to electro co-flow. One of the goals of this project is to find the phase diagram respect all the variables that control our system: voltage, inner and outer flow rates and the viscosity of both liquids. These diagrams will help us to understand why we see certain modes in a well defined experimental window and no in others, and have control over the type and size of the emission.
The present of a viscous co-flowing liquid changes the geometric properties of the modes. For example, the 3D whipping structure, that has a helicoidal shape when the outer medium is viscous,
becomes chaotic when the experiments are performed in air or in low viscous media [2]. We have seen that the presence of the outer medium is crucial to get a wider parametric window where the
whipping is steady.
These two new variables also result in the observation of new modes that have not been reported before, like the 2D whipping you can see below.
The droplet and microfibers generated using electro co-flow can be used in filtration, protective clothing, biomedical applications, pesticides, and composites materials, just to name a few.
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Soft Condensed Matter Laboratory, School of Physics, Georgia Institute of Technology
770 State Street NW, Atlanta, GA, 30332-0430, USA
Phone: 404-385-3667 Fax: 404-894-9958
alberto.fernandez [at] physics.gatech.edu