Generation and Stability of Charged Toroidal Droplets

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Aizenman, Aaron
Fernandez-Nieves, Alberto
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In this project, we have determined the quantitative parameters governing the transition phases of charged toroidal droplets. An instability reminiscent of the Saffman-Taylor Instability (viscous fingers) has been observed when toroidal droplets are exposed to a significantly high voltage source, but this is the only recorded development of this instability in a three-dimensional situation (Alberto Fernandez-Nieves 2016). We created a silicon oil environment of extremely high viscosity with aminopropyl terminated silicon oil (ATSO) added to lower surface tension. We utilized surfactants to minimize the surface tension between the inner and outer fluids to slow down the dynamics of the system enough to give the surface a chance to reach equipotential, thus allowing us to test the theories that currently exist in the field. In an attempt to disprove the possibility that this was the Saffman-Taylor Instability, we also attempted viscosity inversion experiments. These failed, thus giving us almost conclusive proof that this was indeed the Saffman-Taylor Instability. By proving that this is indeed the Saffman-Taylor Instability, we have also proven that this three-dimensional problem can be analyzed as a series of two-dimensional problems. This approach vastly simplifies further calculations and analysis of similar systems. A secondary focus of this project was to perfect a method of automated generation of inherently unstable shapes in viscoelastic materials. By using a novel method of 3D printing, the project attempted to increase the efficiency with which we can generate samples for testing and observation while also adding uniformity and consistency to the trials and experiments.
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