Substrate-Independent Electrohydrodynamic Jet Printing with Dual-Ring Electrostatic Focusing Structure

Electrohydrodynamic jet (E-Jet) printing is one of the most effective methods for fabricating micro/nanostructures due to its high-resolution, broad material adaptability, and simple process. However, printing high-resolution patterns on curved or insulated substrates still is of a great challenge because it is quite difficult to keep the electric field distribution stable between the nozzle and the substrate during the printing process. To address these issues, a dual-ring electrostatic focused electrohydrodynamic jet (DEFEJ) printing method is proposed. In this technique, a microtip with a radius of curvature (ROC) of several micrometers is placed in a conductive dual-ring structure to form the built-in electrostatic focusing and drive the Taylor cone. The high-speed jets then fall on the substrate due to their own motion inertia, eliminating the influence of the substrate curvature and its conductivity on the electric field distribution. Submicrometer droplets with an average diameter of about 0.83 mu m are obtained using a 10-mu m-ROC microtip. In addition, high-resolution microstructure patterns are also printed on substrates with different conductivity and curvature. This DEFEJ printing method not only has the same printing accuracy as conventional E-Jet printing, but also can significantly increase the adaptability of E-Jet printing to different substrates.