Multifunctional Luffa Sponge Hydrogel with High Mechanical Strength, Fatigue Resistance, and Ionic Conductivity for Monitoring Human Vital Signs

Abstract

Biomass-based multifunctional hydrogels with high mechanical strength, fatigue resistance, and electrical conductivity are promising materials for the fabrication of flexible electronic devices. However, achieving mutually exclusive properties simultaneously remains challenging. Herein, a novel luffa sponge (LS) composite multi-functional hydrogel (WLSHG) is prepared. The LS is dignified to create a flexible 3D skeleton, which is then polymerized with polyacrylamide in situ using a tannic acid–ferric ions reoxidation system. Benefiting from the strong physical support of the LS skeleton and multiple interactions between molecules in the system, synergistically enhanced the mechanical properties of the hydrogel. The compressive strength and modulus of the WLSHG increased by 557% and 2000%, respectively, compared with the pristine hydrogels. And the honeycomb-like microchannels in the LS bundle facilitated efficient ion transport, resulting in an ionic conductivity of 0.124 S m⁻¹ for WLSHG. The WLSHG-based flexible strain sensor exhibited excellent sensitivity (2.03 kPa⁻¹) and stability (>1000 cycles) over a wide pressure range. By integrating this sensor into an array and using Internet of Things and machine learning technologies, its ability is successfully demonstrated to accurately recognize human sitting position and gait patterns. This study presents a promising approach for fabricating high-performance biomass-based hydrogels for flexible electronic devices.