Highly Robust Cellulose Ionotronic Fibers Via Biomimetic Liquid‐Crystalline Spinning for Energy Harvesting and Humidity Sensing

ABSTRACT The rapid advancement of ionotronics has positioned ionic conductive materials as increasingly pivotal elements in the evolution of flexible wearable sensors. However, developing ionotronic fibers with sufficient mechanical robustness and ionic conductivity remains a formidable challenge. This issue primarily arises from the intrinsic predicament in formulating spinning dopes with concurrent high polymer content, high ion concentration, and desirable low spinning viscosity. Inspired by the liquid‐crystalline spinning of natural silk, herein, we fabricated cellulose ionotronic fibers (CIFs) from a nematic cellulose liquid‐crystalline dope. Leveraging the self‐alignment of cellulose chains, the nematic spinning dope exhibits suitable viscosity for stable extrusion even at high polymer concentrations. The resultant CIFs display remarkable mechanical strength (14.6 MPa), toughness (19.74 MJ·m −3 ), extensibility (308.9%), and excellent ionic conductivity (2.38 S·m −1 ). Furthermore, CIFs exhibit prominent stability and superior sensitivity in both triboelectric energy harvesting and humidity response, rendering them highly promising for human motion sensing and respiratory monitoring. In summary, this work offers critical perspectives into the construction of high‐performance and environmentally sustainable flexible ionotronic devices, laying a foundation for the sustainable manufacturing of flexible electronics.