Imparting High Conductivity to 3D Printed PEDOT:PSS

Complex 3D geometry and high conductivityhave generallybeen mutuallyexclusive characteristics for conducting polymers. For instance, poly-(3,4-ethylenedioxythiophene):poly-(styrenesulfonate)(PEDOT:PSS), a benchmark conducting polymer, typically exhibits conductivity1 to 2 orders of magnitude lower in 3D-printed forms compared to 2D-processedthin films, due to its sensitivity to processing conditions. Here,we investigate the main causes of this reduced conductivity, whichare found to be (1) the ink formulation strategy and (2) the stronglateral phase separation of the printed filaments. Processing approachesthat overcome these factors have produced significant conductivityenhancement to 1200 S/cm, higher than the typical 2D-processed PEDOT:PSS.Our study also unveils a set of guiding principles for optimizingthe conductivity of direct ink writing (DIW)-printed PEDOT:PSS, includingprinting orientation, print bed temperature, and nozzle diameter.With the combination of high conductivity and 3D geometric freedom,potential applications such as omnidirectionally deformable LED deviceswith strain-independent electrical behavior and bespoke electronicsthat replicate the shape of human body parts have been demonstrated.