Mechanically robust PEDOT:PSS hydrogel via mild liquid metal crosslinking

Abstract

Poly(3,4-ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS) hydrogels are promising for bioelectronic applications but are constrained by the lack of mild processing strategies and limited mechanical robustness. In this work, we report a crosslinking strategy for PEDOT:PSS hydrogels based on eutectic gallium–indium (EGaIn). In aqueous environments, Ga releases Ga³⁺ ions that interact with PSS chains, modifying the electrostatic interactions between the PEDOT chain and the PSS chain to form ionic crosslinks within the polymer network. The resulting Ga-crosslinked PEDOT:PSS hydrogels exhibit a storage modulus (G′) of up to 2500 Pa. Microscopic characterization reveals a transition from a porous structure to a more compact, flake-like morphology, which contributes to the improved mechanical stability. Ga crosslinking leads to a reduction in electrical conductivity, reflecting the altered polymer interactions associated with ionic crosslink formation. The combination of mechanical enhancement and preserved ionic–electronic mixed conduction suggests that these hydrogels hold promise for organic electrochemical transistor (OECT) applications, where reduced initial conductivity can be advantageous for device operation.