Highly Conductive/Capacitive Three-dimensional Mesh Structures Based on Crystalline PEDOT:PSS Microfibers for Bioelectronic Interfaces

<br/>Despite the non-conventional applications beyond thin film devices, there exist very few methods for constructing 3-dimensional structures based on conjugated polymers without sacrificing their intrinsic electrical/electrochemical properties. Herein, we report on a scalable method for fabricating highly conductive/capacitive 3-D architectures using pure poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) microstructures without additives. First, crystalline PEDOT:PSS microfibers were fabricated via a conventional wet-spinning process and cut into smaller segments by homogenization in water. These highly-conductive/capacitive building blocks were self-fused to form monolithic mesh structures reversibly or irreversibly by inducing water swelling, chain entanglement, and crystallization in a controlled manner. The resultant porous mesh structures showed good mechanical flexibility and excellent electrical/electrochemical characteristics which could be modulated by controlling the loading of constituent microfiber segments. Finally, we demonstrated the fabrication of free-standing 3-D microfiber mesh structures with arbitrary shapes and their application to bioelectrical signal recording on live tissues without adhesives.