Mechanically robust PEDOT:PSS hydrogel <i>via</i> mild liquid metal crosslinking.

Zhou, Qian; Azapagic, Azur; Eiting, Austin; Won, Seoyeon; Boyadzhiev, Alexandra; Sant, Himanshu; Fernandes, Deisy Cristina Carvalho; Zhang, Huanan · Soft Matter · 2026

basic_science · Level V

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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 Ga<sup>3+</sup> 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 (<i>G</i>') 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.