High resolution electrohydrodynamic printing of conductive ink with an aligned aperture coaxial printhead

Electrohydrodynamic (EHD) printing is a promising inkjet technique to generate smaller droplet sizes due to the formation of a Taylor cone. However, the process is intricate and involves the fabrication of a printhead having a smaller nozzle diameter. Notable examples are present in the literature regarding printing through EHD but the underlying phenomenon which is responsible for generating the smaller droplet is obscure. In this work, we present a methodology which highlights the importance of nozzle shape which can govern smaller droplets even with a large head diameter. The work achieves a resolution of less than 2 μ m by fabricating the inkjet head using simple techniques and off-the-shelf inexpensive needles of nozzle diameter ranging from 500 μ m to 250 μ m. The study of various nozzle profiles resulted in a printed resolution which is 50 times smaller than the nozzle diameter. Moreover, the study also highlights the importance of the wetting area profile of the nozzle and explains the role of printhead design which facilitates fine resolution printing of conductive tracks which until now seemed to be obscure.