Ultra-High-Speed Electric-Field-Assisted Direct Ink Writing of Poly(3,4-ethylenedioxythiophene):Polystyrene Sulfonate - Poly(ethylene oxide) Ink on Flexible Substrates

Abstract

The electric-field-assisted direct ink writing (eDIW) process is a promising manufacturing technique for printing high-resolution conducting patterns at high-speed. In this work, the conducting polymer poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) (PEDOT:PSS) is modified with high-molecular-weight (2,000 kDa) nonconducting polyethylene oxide (PEO) additive at 52 wt% solid ratio. The viscoelasticity of the inks is tuned by varying polymer concentration from 0.5% to 3% in water which results in inks with distinct rheological properties, establishing a printing window and identifying optimal formulations. That enables stable eDIW printing on a highly unstable and flexible plastic substrate, at substrate speeds between 5 and 30 m/s. The effect of the electric field on the printing process is explored experimentally by comparing deposit geometry at 0 and 4 kV, revealing the field's consistent role in facilitating filament deposition and reducing trace thickness during printing. This work also explores the feasibility of attaining extremely high printing speeds on flexible substrates and clarifies the fundamental mechanisms that limit or define the achievable printing speed. In addition, it is demonstrated that eDIW steady-state printing is possible at exceptionally high substrate speeds of up to 30 m/s with enhanced resolution resulting in dried PEDOT:PSS-PEO traces as narrow as one-thirtieth of the nozzle diameter.