Conducting polymer nanoparticles with intrinsic aqueous dispersibility for conductive hydrogels

Conductive hydrogels are promising materials with mixed ionic-electronic conduction to interface living tissue (ionic signal transmission) with medical devices (electronic signal transmission). Beyond signal transduction, the hydrogel form factor also uniquely bridges the wet and soft biological environment with the dry and hard environment of electronics. The synthesis of such hydrogels for bioelectronics requires scalable, biocompatible fillers with high electronic conductivity and compatibility with common aqueous hydrogel formulations/resins. Despite significant advances in the processing of carbon nanomaterials (graphene, graphene oxide, carbon nanotubes), fillers that satisfy all these requirements are lacking. Herein, intrinsically dispersible acid-crystalized PEDOT:PSS nanoparticles (ncrys-PEDOT_X) are reported which are processed through a facile and scalable non-solvent induced phase separation (NIPS) method from commercial PEDOT:PSS without complex instrumentation. The particles feature conductivities of up to 410 S cm^-1, and when compared to other common conductive fillers, display remarkable dispersibility, enabling homogeneous incorporation at relatively high loadings within diverse aqueous biomaterial solutions without additives or surfactants. The aqueous dispersibility of the ncrys-PEDOT_X particles also allows simple incorporation into resins designed for microstereolithography without sonication or surfactant optimization; complex biomedical structures with fine features (< 150 μm) were printed with up to 10% loading of conductive particles. The ncrys-PEDOT_X particles overcome the challenges of traditional conductive fillers, providing a scalable, biocompatible, plug-and-play platform for soft organic bioelectronic materials.