Electro-hydrodynamic micro prism with applications to automultiscopic displays

by Nathan Wolfe

Institution: University of British Columbia
Department: Mechanical Engineering
Degree: Master of Applied Science - MASc
Year: 2015
Record ID: 2059733
Full text PDF: http://hdl.handle.net/2429/52874


The recent trend in display technology is to provide the viewer with an artificial three- dimensional (3D) experience using lenses or aides, however the number of viewers and resolution of the display is limited. To remedy these problems, an array of prisms can be placed over the display redirecting the projected light at specific angles in a time-multiplexed fashion and at full resolution. The difficulty in this approach is that the angle of the prism needs to be adjustable with accurate and fast control. This thesis presents the theory, development, and analysis of a novel adjustable prism coined an electro-hydrodynamic micro prism (EHMP). An EHMP consists of an elongated conducive water droplet with pinned contact lines using hydrophobic surface patterning. By applying a voltage between the droplet and an offset electrode above it, the shape of the droplet is deformed into a triangular prism where the angle of the prism is dictated by the strength of the applied voltage. A numerical model of an EHMP was developed using finite element analysis and smoothed particle hydrodynamics to model the electro-hydrodynamics of the system. The numerical model was qualitatively verified using the collapsing square and oscillating droplet tests, and then used to predict an operating voltage range of 400 – 550 V for a 200 μm droplet, and that the leading edge of the electrode dictates the final deformation of the drop. To fabricate a prototype EHMP, a microcontact printing technique was developed to pattern polytetrafluoroethylene nanoparticles onto an indium tin oxide coated glass slide creating the hydrophobic patterning. A prototype 1 mm diameter prototype EHMP was fabricated and tested in the 1.5 – 2 kV range. It was found that there was minimal droplet deformation before failure due to electrospray formation. Though not useful for 3D displays, the results from these large-scale experiments experimentally validate the numerical model. Model simulations showed ideal EHMP deformations can occur under the right conditions, however its performance under current conditions is limited due to dielectric breakdown failure and a fill factor of only 0.66 thus proving not to be a practical solution to automultiscopic displays.