Electrophoretic Inks with Structural Color

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1236086PI: DufresneElectrophoretic displays based on charged colloidal pigments consume far less energy than conventional back-lit liquid crystal displays. In fact, a well-designed electrophoretic display with a static image consumes no energy. This energy savings arises from two important factors. First, electrophoretic displays are bistable, so they consume energy only when changing the displayed image. Second, electrophoretic displays use ambient light, instead of internal light sources. Therefore, electrophoretic displays are ideal for reading, signage and architectural applications. However, the central limitation of these displays is that they only produce black and white images. In principle, color images can be created from electrophoretic displays through the use of colored filters, as in an LCD display, but such devices would be too dark for most applications. Bright electrophoretic displays would require each pixel to be able to display either red, green or blue. To achieve this, this project will create electrophoretic inks with structural color. Inspired by color-producing nanostructures in bird feathers, this work will control the color of electrophoretic inks by tuning the spacing of charged colloidal particles. The spacing will be determined by interparticle forces and external electric fields. Thus, the color of the ink containing pixel will be switchable with an applied voltage. To achieve this goal, this project will need to solve several fundamental problems in colloid science. First, the research will identify general principles and specific materials for creating charged suspensions in non-polar solvents with sufficient short-range order to produce structural colors. Second, the research will characterize the effect of external electric fields on the structure of these suspensions.