Hydrophilic, conductive and flexible piezoresistive PEDOT:PSS 3D sensors with tunable microarchitecture and crosslinked using a PEGylated crosslinker

Abstract

Poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) is an emerging biomaterial that – due to its stability and conductivity - has been adopted for diverse biomedical technologies, such as biosensors, coatings for electrodes, and substrates for tissue engineering. Currently, some researchers are focusing on the processing of this biomaterial into three-dimensional (3D) scaffolds, either in the form of fibrous structures, porous sponge-like constructs or hydrogels. However, due to its instability in aqueous environments, challenges occur when applying manufacturing techniques to PEDOT:PSS. Moreover, the standardised use of covalent crosslinking via glycidoxypropyltrimethoxysilane (GOPS) negatively impacts the conductive properties of the material. In this work, poly(ethylene glycol) diglycidyl ether (PEGDE) – which was previously demonstrated to stabilise PEDOT:PSS films - has been used as crosslinking reagent to generate 3D electroconductive porous biomaterial sensors via lyophilization. Both isotropic and anisotropic porous scaffolds were obtained, and although macroscopically similar to GOPS-crosslinked samples, these constructs exhibited unique mechanical electrical features. PEGDE crosslinking of 3D PEDOT:PSS sponges enhanced material hydrophilicity, softness, and electrical conductivity. Finally, biphasic electroactive sponges were manufactured via the inclusion of an elastomeric matrix into these constructs to prolong their longevity and achieve varying degrees of bulk stiffness. These were evaluated as piezoresistive sensors and demonstrated a high strain gauge factor with potential for biometric sensing and biomonitoring.