Rapid fabrication of porous κ-carrageenan/cellulose nanofibrils-polydopamine composite hydrogels induced by ionic interaction for flexible electronic devices

A novel κ-carrageenan composite hydrogel via incorporation of TEMPO-oxidized cellulose nanofibrils (TCNF) and polydopamine (PDA) nanoparticles, was fabricated by ionic interaction to achieve a higher mechanical and higher conductive performance. Owing to the excellent compatibility and stability of the TCNF-PDA mixture, and the strong ionic interactions between the hydrogel precursor and metal cations in the hydrogel formation, the composite hydrogel showed improved mechanical property of 73.5 kpa and a faster gel formation process of 58 s. The gel formation mechanism was comprehensively illustrated by XPS technique, a double-network with one main noncovalent interaction was created inside the hydrogels. Moreover, the inter-connected porous hydrogel structure with smaller pores improved current carrying and diffusion of electrolyte metal cations, the conductivity reached at 2.13 S/m. It could also sensitively and stably detect the external stress applied, demonstrating such hydrogel was beneficial to be applied at flexible electronic devices.