Dip Coating of Water‐Resistant PEDOT:PSS Films Based on Physical Crosslinking

Abstract

Water‐resistant poly(3,4‐ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) films are valuable in biomedical applications; however, they typically require crosslinkers to stabilize the films, which can introduce undesired aggregation or phase separation reactions. Herein, a dipping‐based process to prepare PEDOT:PSS films on nonplanar surfaces without crosslinker is developed. Sequential soaking of a dip‐coated PEDOT:PSS film in ethanol and water imparts water resistance to the film. Microscopic and spectroscopic techniques are used to monitor the process and confirm that the ethanol soaking elutes the excess PSS from the film bulk, which stabilizes the film prior to the water‐soaking process. The obtained films act as conductors and semiconductors on curved surfaces, including 3D‐printed objects. A film deposited on a curved surface is successfully applied as the channel layer in a neuromorphic organic electrochemical transistor. This approach can enable integrated bioelectronic and neuromorphic applications that can be readily deployed for facile prototyping.

Materials aspects of PEDOT:PSS for neuromorphic organic electrochemical transistors

“…Nevertheless, the resulting material was bulk. We recently reported a methodology for forming physically crosslinked PEDOT:PSS films on both flat and non-flat substrates [38]. Sequential soaking of a dip-coated PEDOT:PSS film in ethanol and water resulted in water resistance.…”

“…For instance, some biomolecular sensing devices are based on the perturbation of ion injection in the presence of target molecules [30][31][32]. As mentioned below, neuromorphic applications also control ion diffusion via ion trapping or ion diffusivity tuning [33][34][35][36][37][38]. The ion dynamics in PEDOTbased systems can be tuned by a dopant (typically poly(styrenesulfonate) (PSS) or p-toluenesulfonic acid (Tos)) or third-party materials including crosslinkers, surfactants, and other additives.…”