Native-Framework Retention: Loofah-Based Hydrogels Self-Reinforced by the Native Framework for Piezoresistive Sensing

Natural biomass materials have attracted widespread attention for constructing green, high-performance flexible sensors owing to their renewability, low cost, and biodegradability. Among them, loofah-despite its low cost and intrinsic three-dimensional architecture-has remained comparatively underexplored. Here, we propose a fabrication strategy that fully exploits loofah by using it as a structural scaffold while leveraging its residual powder for synergistic reinforcement. The loofah sponge is delignified with sodium chlorite (NaClO2) and subsequently functionalized with carboxylated multiwalled carbon nanotubes (A-MWCNTs) to yield a conductive loofah scaffold (LS). The remaining loofah powder is blended with poly(vinyl alcohol) (PVA) to prepare a conductive hydrogel (LH), and freeze–thaw cycling is then applied to assemble a composite elastomer, denoted LS@LH. Owing to its rigid-flexible-coupled architecture, LS@LH combines excellent mechanical strength with pronounced piezoresistive responsiveness. Experimentally, the LS@LH composite achieves a compressive strength of 353 kPa, a sensitivity of 1.47 kPa–1, and a response time of 0.5 s, while exhibiting good recoverability and stability over 1400 rapid loading–unloading cycles. This work provides a pathway for high-value utilization of agricultural waste and lays the foundation for the development of low-cost, sustainable flexible electronic devices.