3D Freeze‐Printing of Binder‐Free PEDOT:PSS

ABSTRACT The integration of advanced materials with new fabrication techniques is crucial for advancing bioelectronics. Poly(3,4‐ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS) is a widely used conductive polymer, but its printability remains challenging due to low viscosity in aqueous solutions. Here, we present 3D freeze‐printing to fabricate binder‐free, high‐conductivity PEDOT:PSS structures. Utilizing a temperature‐controlled plate, 3D structures can be formed by direct extrusion printing of dimethyl sulfoxide (DMSO)‐doped PEDOT:PSS solutions that are typically unprintable using conventional methods due to spreading and poor shape retention. Freeze‐printing at temperatures just below 0 °C increases PEDOT:PSS conductivity by more than 350% compared to room temperature printing. Characterizations using Raman spectroscopy, XRD, and XPS indicate the presence of freezing‐induced phase separation and polymer chain alignment, contributing to enhanced conductivity. Critically, our mild fabrication approach enables direct printing onto thermally sensitive materials, such as alginate hydrogels, achieving ∼50% reduction in interfacial impedance at 1 kHz. Unlike other methods requiring multi‐day pre‐ or post‐processing under harsh conditions, our approach enables rapid fabrication within a few hours, without the use of harsh chemicals. This work introduces a broadly applicable strategy for patterning conducting polymers with mixed conductivities on soft substrates, suitable for applications in bioelectronics, soft robotics, and wearable sensing devices.