Polymerizable Deep Eutectic Solvents‐Enabled High‐Lignin‐Density Networks for Ambient Multi‐Scale Fabrication of Multifunctional and Extreme Environment Adaptable Soft Devices

Skin-like soft electronics exploiting gels containing biomass-derived components raise increasing research attention, in which multifunctional lignin has been extensively explored. Nevertheless, elevating the lignin loading usually sacrifices the performance, limiting their application potentials. Herein, we develop a unique polymerizable deep eutectic solvent (PDES) consisting of a quaternary ammonium monomer and lactic acid to incorporate with high-density lignosulfonate (LS) of > 20 wt.% and address the performance trade-offs. The lignin-induced self-catalytic polymerization associated with electrostatic assembly enables room temperature gelation within < 5 min and ambient-air micropatterning. Remarkably, the anionic LS and polycationic matrix affording multiple non-covalent interactions drastically enhance the mechanical strength to > 1 MPa and versatile adhesion up to > 500 kPa, meanwhile allowing self-healing, photothermal, and antibacterial capabilities. Such LS-PDES eutectogels also permit ion conduction (> 3 mS cm^-1) and superior environmental adaptivity over -80°C to 100°C. Thus, employing the in situ polymerization between electrodes, rapid prototyping of bend-/impact-resistant flexible supercapacitors is demonstrated to power wearable sensors. More importantly, it facilitates the production of miniaturized soft organic electrochemical transistor (OECT) arrays, whose performance can be well maintained under deformed and extreme temperature conditions. This high-lignin-density eutectogel platform paves a straightforward route towards printed soft ionotronics, bioelectronic interfaces, and brain-inspired computing.