Electrohydrodynamics and Rheology: Direct Ink Writing of Highly Conducting PEDOT:PSS-Based Polymer Blends*

Poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) (PEDOT:PSS) is a conducting polymer that holds great promise for electronic applications. This study proposes effective methods for enhancing the electrical conductivity and, simultaneously, the printability of inks containing PEDOT:PSS. Direct Ink Writing (DIW) imposes strict requirements on the rheological properties of the printed inks, thus limiting the choice of qualifying materials. To improve the printing processability, countless materials have been added to pristine PEDOT:PSS in the past, but do so at the expense of the electrical conductivity. The present work develops PEDOT:PSS-based polymer blends capable of enhancing the electrical conductivities while concurrently meeting the demanding requirements of extrusion-based additive manufacturing. In addition to an increased electrical conductivity from polymer doping, it is demonstrated that a post-processing humidity treatment further increases the electrical conductivity. Moreover, the electrostatically-assisted direct ink writing (eDIW), a novel extrusion-based additive manufacturing technique introduced here, revealed that it is capable of creating electrically conductive 2D and 3D circuits at an increased printing speed and at a higher resolution.