Confined graphitization of cellulose polymorphs enables high-performance piezoresistive electronics

Cellulose, a renewable biopolymer, holds significant promise for sustainable electronics and sensing technologies, however, its intrinsic insulating nature hinders broader application. In this study, we present a regioselective, acid-induced confined graphitization strategy to convert four cellulose polymorphs (I–IV) into intrinsically conductive nanocellulose (CNCene) with high graphitization degrees, excellent electrical conductivity, outstanding thermal stability (up to 445.3 °C), and diverse nanostructured morphologies. Among them, CNCene-III was creatively utilized as a multifunctional nanofiller and incorporated into a cellulose matrix to construct a flexible piezoresistive device. Unlike conventional conductive fillers that often compromise flexibility, CNCene-III remarkably enhanced both the tensile strength (from 35.9 MPa to 82.1 MPa) and the elongation at break (from 7.7 % to 23.1 %) of the resulting cellulose composite film (CCF), owing to strong interfacial interactions. The CCF exhibited an ultrafast response time of 90 ms and a 23 % resistance change under low pressure, demonstrating high sensitivity and rapid signal feedback. This enabled real-time pressure sensing capability, as validated by reliable Morse code signal transmission. Compared with traditional cellulose-based conductive composites incorporating CNTs or graphene derivatives, this strategy offers a scalable, pyrolysis-free platform for engineering conductive nanocellulose with integrated mechanical reinforcement, electrical conductivity, and functional responsiveness.