Drop-on-demand electrohydrodynamic printing of nematic liquid crystals

Abstract

Electrohydrodynamic (EHD) printing of nematic liquid crystals (LCs) is demonstrated. Miniscule LC droplets, as small as 1 micron, are generated with the EHD printing system and deposited with high precision onto a glass substrate. Herein, we show how the voltage waveform and pulse frequency applied to the print nozzle influences the dynamics of the deposition process and the final landed footprint diameter of the printed spherical-cap-shaped LC droplets at the glass substrater. To complement results from high-speed shadowgraphy imaging, simulations are employed to model the jetting process and the formation of the Taylor cone. Using EHD printing, results for two different printing modes, cone jetting and microdripping, are shown. The benefits and drawbacks of each mode are highlighted, and the paper is concluded with the demonstration of a printed alphanumeric pattern that showcases the capability of EHD printing to deposit very small volumes of nematic LC in order to form well-defined spatial patterns.