Pulsed electrohydrodynamic printing of conductive silver patterns on demand

Pulsed electrohydrodynamic printing (EHDP) is used to fabricate conductive silver patterns with micrometer resolution. The silver ink pendant experiences swelling, pulsation, and ejection under an applied pulse voltage of 20 Hz. The droplet deposition frequency is equal to the applied voltage frequency so that the EHDP can deposit silver ink on demand. A low applied voltage favors uniform and non-scattering silver patterns while a high applied voltage results in ink scattering. Discrete droplets with 45-55 mu m in diameter and continuous tracks with 60 mu m in width are generated by using a 110-mu m-cailber nozzle. The feature size of deposited patterns is about half of the nozzle caliber, and a finer resolution can be achieved with the introduction of smaller nozzle calibers. Furthermore, the appropriate curing condition is investigated for sufficient combustion of ink solvent. The minimum resistivity of 3.3 mu Omega cm is demonstrated for a continuous track cured at 200 degrees C for 10 min. Eventually, several passive electrical components, such as coated resistors, interdigitated capacitors (6 pF), and spiral inductors (0.6 mu H), are successfully fabricated.