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UBC Theses and Dissertations

Liquid motion induced by electrostatic deformation of fluidic interfaces Aggarwal, Januk Swarup


This thesis introduces a novel method for deforming fluidic interfaces while minimizing the friction and hysteresis typically associated with conventional electrowetting systems. The technique uses thin solid surfaces that are patterned so that the contact angle of a liquid drop placed on the surface depends on location. With an appropriate pattern, the contact line between the fluid interface and the solid surface is immobilized to a degree which in turn constrains the drop shape in useful ways. With suitable surfaces and liquids, the position of the contact line is stable for a range of drop shapes. The drop can be deformed by applying an inhomogeneous electric field to the fluid interface. Since the contact lines are stable, movement of the liquid in the drop is induced while no contact lines are formed or moved, thus minimizing friction and eliminating hysteresis. This technique is examined in the context of two different example applications; one is a potential reflective information display and the other is a fluidic pump for enhanced surface heat transfer. With the reflective display, the deformation moves a coloured liquid drop through a thin, reflective solid substrate. The apparent reflectivity is modulated by changing the amount of coloured liquid that is between the reflective solid and the viewer. In the fluidic pump, the induced flow is along the surface of a solid substrate, in order to transfer heat along the surface at a rate that substantially exceeds that of an equivalent copper plate. Initial prototypes for the two applications were designed, tested and compared to simple models. These results demonstrate the basic feasibility of such systems and suggest that further research in this area is warranted.

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