Biomimetic Hydrogels with Oxidative Cross-Linking for Ionically Conductive Interfaces in Long-Term Wearable...

Biomimetic hydrogels with great mechanical properties that provide stable and low-impedance interfaces are essential for long-term wearable bioelectronics. In this study, we developed dopamine-grafted carboxymethyl cellulose (CMCDA) hydrogel and oxidative cross-linking form (CMCDA'). Using multidimensional (1D/2D) NMR techniques, we provide detailed structural elucidation of dopamine-grafted polysaccharides, offering new insights into amide formation, Schiff base/Michael addition structures, and partially oxidized polydopamine segments. The cross-linked CMCDA' hydrogels are mechanically robust, highly hydrophilic, and strongly adhesive on various substrates, enabling conformal skin contact. After electrolyte exchange with saturated NaCl, CMCDA' becomes ionically conductive (5-10 S m^-1) and maintains stable impedance under continuous hydration. Integrated as a wearable electrode interface, CMCDA' supports reliable electrocardiogram acquisition for one week, outperforming the commercial conductive gel at curved body sites. These results highlight oxidative-cross-linked, cellulose-derived hydrogels as sustainable ionically conductive interfaces for long-term wearable bioelectronics.