Inkjet printing of liquid crystals and polymer composites for novel thin-film optical elements

Thesis

This thesis investigates the drop-on-demand inkjet printing of liquid crystal (LC) inks, from drop formation and deposition, through to substrate selection. Inkjet printing is a particularly attractive fabrication method as it is a precise, scalable and highly cost-effective additive manufacturing process. These benefits, along with the ability to deposit pico-liter volumes of particulate suspensions, viscous and complex fluids, have led to inkjet printing being considered as an attractive alternative fabrication technique in a range of established fields such as the display, pharmaceutical and bioengineering industries. However, the unique considerations of using liquid crystalline inks, such as their anisotropic properties and alignment criteria is barely touched in the literature. This thesis describes the design and build of an inkjet printing system capable of depositing a range of different functional inks such as LCs and polymer solutions. Drop generation of a nematic LC in a piezoelectric printhead and the role of different printing substrates on the final droplet configuration is considered in detail. This knowledge is used to fabricate novel, variable-focus microlens arrays that can be deposited as pre-programmable arrays on to a variety of different substrates. The unique properties of inkjet printing are then leveraged to describe two new methods of producing patterned, single layer polymer dispersed LC films. A prototype switchable, patterned polymer-dispersed LC film, produced by inkjet printing, is demonstrated. This work shows the feasibility of inkjet printing LC and polymer formulations and has important technological implications in the manufacturing of small and large area, polymer dispersed LC films for a variety of applications.

Authors: Parry, E

• Type of award: DPhil
• Level of award: Doctoral
• Awarding institution: University of Oxford
• Language: English
• Keywords: printed displays; microlenses; Inkjet printing; fabrication of optical thin film elements; 3D printing; smart windows; additive manufacturing; liquid crystals
• Subjects: Liquid crystal devices; Ink-jet printing