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UBC Theses and Dissertations

Electrolytic capacitive display Radel, Jason


This thesis describes the novel use of an electrolytic capacitor to controllably modulate the optical properties of a surface. The electrically-controlled modulation is achieved using electrodes comprised of carbon nanofoam, a new allotrope of carbon that has an extremely high surface to volume ratio, resulting in a very high capacitance per unit volume which enables the material to attract a significant amount of electrostatic charge, an amount that is much greater than would be the case if the electrodes were not so highly porous. In the display described here, a diffusely reflective porous material, positioned above an interdigital array formed by two carbon nanofoam electrodes, was immersed in an electrolyte solution in which light-absorbing dye ions had been dissolved. When an electrical potential was applied across the electrodes, the capacitor charged and the dye ions were drawn into the pores of the electrodes and therefore drawn out of the bulk solution and porous material, causing the material to become reflective rather than colored. When the applied voltage was removed, the dye ions were able to diffuse out of the nanofoam and redistribute throughout the bulk solution and into the material, causing it to return to its original colored appearance. This effect was shown to be reproducible over many cycles and various experiments were conducted to develop a better understanding of the interaction of the dye ions with the carbon nanofoam electrodes and to understand how these interactions affect the time-course of the response. Potential applications of this technology include low power, high-contrast reflective image display devices, particularly in applications where the visual appearance of ink on paper is required. These so-called “electronic paper” displays are becoming more common in devices such as e-book readers, but the displays that are currently used in these devices are limited in terms of brightness and switching speed. The results of this research indicate that this approach using high capacitance porous electrodes may have application in high contrast reflective display devices.

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