Electrowetting-assisted direct ink writing for low-viscosity liquids

Abstract

In conventional direct ink writing (DIW) process, low-viscosity liquids are usually nonprintable, which greatly limits the choices of inks and the potential applications of DIW. To address this challenge, the present work reports a novel electric-field-assisted method to enable DIW of low-viscosity liquids. An external electric field is applied between the dispensing nozzle and the substrate, to vertically pull the printed filament for decreasing the internal pressure along the printing direction. Our proposed method overcomes the common capillary instability characteristic of continuous extrusion of low-viscosity materials. Compared with conventional approaches, the electric-field-assisted DIW process significantly widens the available range of process parameters, increases the throughput by over 150%, and improves the printing accuracy by more than four-fold. These findings indicate an innovative approach for the fabrication of next-generation functional devices using low-viscosity liquids, which used to be difficult or even impossible to print.