Design of Actuation Waveforms for Precision Control of PEDOT:PSS Droplet Formation in Inkjet Printing

Abstract

Inkjet printing offers a scalable and cost-effective approach for the maskless fabrication of high-resolution device patterns for flexible electronics. Controlling droplet size for various functional inks become a critical task to fully utilize the fabrication capability of the inkjet printing. In this work, we investigate the effect of the waveform design on controlling the droplet formation using PEDOT:PSS ink. Three waveform types: unipolar, sinusoidal, and bipolar, were examined to modulate pressure dynamics within the printing nozzle. By tuning actuation voltage and timing parameters, we successfully reduced the printed droplet diameters from 60 μm to 30.28 μm for a printing nozzle with 30 μm nozzle orifice, approaching the physical limit from the nozzle size. Through detailed parametric optimization, we identified critical time-voltage regimes for each waveform, revealing the physical principles that govern ink chamber dynamics and droplet generation. These results and findings establish a foundation towards waveform-driven resolution enhancement in inkjet printing and contribute to the broader applications of high-precision additive fabrication for next-generation electronic devices.