Interfacial engineering with functionalized lignin nanoparticles enables stable, conductive aqueous carbon nanotube inks for flexible sensors

Printable aqueous carbon nanotube (CNT) inks are promising for scalable, flexible, and wearable electronics, yet it remains challenging to simultaneously achieve high electrical performance, long-term dispersion stability, and reliable processability in water. A one-pot ternary deep eutectic solvent (TDES) pretreatment enables lignin depolymerization and functionalization with ammonium phytate/sulfate groups, followed by spontaneous self-assembly into P/N/S-containing lignin nanoparticles (PLNPs). The resulting PLNPs exhibit tunable particle sizes (from 24 nm to 100 nm) and high negative surface charge (up to −62.6 mV). PLNPs adsorb uniformly onto CNT surfaces without forming large aggregates. Molecular dynamics (MD) simulations reveal an “anchor-and-disperse” interfacial mechanism, in which PLNPs anchor on CNT surfaces with heteroatom-enabled noncovalent interactions, while surface charge and hydration provide electrosteric and steric stabilization that suppresses reaggregation. The PLNPs/CNT inks show pronounced shear-thinning and rapid thixotropic recovery, making them suitable for screen printing of conductive patterns on paper. The inks exhibit excellent colloidal stability (>100 days) and achieve conductivities up to 34.9 S·cm−1 without additional synthetic additives. Furthermore, cotton textiles can be dip-coated to fabricate wearable piezoresistive sensors capable of monitoring diverse human motions. This work provides a renewable, waterborne CNT ink platform for sustainable printed and wearable textile electronics.