Direct Writing and Characterization of Three-Dimensional Conducting Polymer PEDOT Arrays

Abstract

Direct writing is an effective and versatile technique for three-dimensional (3D) fabrication of conducting polymer (CP) structures. It is precisely localized and highly controllable, thus providing great opportunities for incorporating CPs into microelectronic array devices. Herein we demonstrate 3D writing and characterization of poly(3,4-ethylenedioxythiophene)-polystyrenesulfonate (PEDOT:PSS) pillars in an array format, by using an in-house-constructed variant of scanning ion conductance microscopy (SICM). CP pillars with different aspect ratios were successfully fabricated by optimizing the writing parameters: pulling speed, pulling time, concentration of the polymer solution, and the micropipette tip diameter. Especially, super high aspect ratio pillars of around 7 μm in diameter and 5000 μm in height were fabricated, indicating a good capability of this direct writing technique. Additions of an organic solvent and a cross-linking agent contribute to a significantly enhanced water stability of the pillars, critical if the arrays were to be used in biologically relevant applications. Surface morphologies and structural analysis of CP pillars were characterized by scanning electron microscopy and Raman spectroscopy, respectively. Electrochemical properties of the individual pillars of different heights were examined by cyclic voltammetry using a double-barrel micropipette as an electrochemical cell. Exceptional mechanical properties of the pillars, such as high flexibility and robustness, were observed when bent by applying a force. The 3D pillar arrays are expected to provide versatile substrates for functionalized and integrated biological sensing and electrically addressable array devices.

Human Neural Tissues from Neural Stem Cells Using Conductive Biogel and Printed Polymer Microelectrode Arrays for 3D Electrical Stimulation

“…Direct‐Write Printing of CP Pillars : Direct‐write printing of CP pillars was performed as previously reported by us, with the difference that the ‘pillars' were printed here on individually addressable electrodes (Figure a–c; and Figures S1 and S2d, Supporting Information). Briefly, a solution of 500 µL PEDOT:PSS (1.3 wt% dispersed in water), 175 µL DMSO and 10 µL crosslinking agent GOPS was used as the “ink” and ultrasonicated for 10 min every time before “writing” to evenly disperse the polymer.…”

“…Electrochemical Characterization of Printed CP Pillars : Electrochemical properties of CP pillars were compared with electropolymerized CP films and bare gold microelectrodes . The electrodes were characterized for CSC C using CV, CIL using VTM, and impedance using EIS.…”

“…Further to our previous reports of the biogels' properties, we have now electrochemically characterized the gel to confirm electrical conductivity so as to be favorable for in situ cell stimulation. ES of cell‐laden gels is achieved using a high‐resolution direct‐write printed array of 3D penetrating CP pillar electrodes for stable and biocompatible cell coupling ( Figure ; and Figures S1 and S2, Supporting Information) . The 3D multielectrode configuration provides a larger surface area to augment coupling with the developing electrogenic tissue.…”

“…The 3D multielectrode configuration provides a larger surface area to augment coupling with the developing electrogenic tissue. We have previously described various properties of the CP pillars including surface morphology, as well as chemical, structural, and mechanical properties, however, to the best of our knowledge, our account is the first example of 3D ES of human stem cells in vitro to form 3D human tissues, and more specifically functional neural tissues. We submit that the platform is scaleable and versatile, envisioning it being amenable in vitro and in vivo to neural and non‐neural cell and tissue types for stimulation and monitoring applications, with in vivo use bolstered by mechanical robustness and flexibility of the pillars to withstand multi‐axial mechanical stresses exerted on the pillars.…”

3D printing of conjugated polymers

“…Recent work carried out under the direction of Jadranka Travas‐Sejdic at the University of Auckland described the formation of PEDOT:PSS micropillar arrays using an electrochemical DIW technique . This work builds upon an earlier report by the group demonstrating a similar technique for the deposition of polypyrrole (PPY) .…”