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Drop coalescence dynamics and protein interactions at the air-water interface
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School of Electrical Engineering |
Master's thesis
Electronic archive copy is available via Aalto Thesis Database.
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en
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62
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The dynamic behavior of liquid interfaces in air, in particular drop coalescence, is fundamental concept to many natural phenomena and important for a range of industrial applications, from rainfall formation in the atmosphere, to emulsion stability in food, pharmaceuticals, cosmetics and more. This report provides a comprehensive study of the fundamental process underlying droplet coalescence, emphasizing the behaviour of surface active proteins particularly Hydrophobin class II (HFB) proteins namely HFB I and HFB II at the air-water interfaces. By also measuring surface tension reduction as a function of dynamic protein adsorption using pendant drop method and studying the liquid bridge as the droplet merge, we are able to provide direct evidence that Hydrophobin surface adsorption is responsible for reducing the surface tension at air-water interfaces and creating a viscoelastic film. The protein film fundamentally transforms the dynamics of coalescence through a distinct transition from rapid bridge growth due to inertia in pure water, to a damping process controlled by the film. We have shown that these dynamics follow different power-law scaling, depend on both protein concentration and duration of the protein adsorption in water and film formation at the interface. This information is crucial for improved understanding of protein stabilized interface, as well as for meaningful design of stable emulsion systems and many other applications.
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Supervisor
Backholm, MatildaThesis advisor
Laurila, TomiMalik, Lokesh