MXene-enhanced multifunctional hydrogel for ultrasensitive strain sensing and self-powered triboelectric energy harvesting

High conductivity, mechanical flexibility, and operational stability must all be balanced in the electrode materials used in flexible triboelectric nanogenerators (TENGs). However, traditional hydrogel electrodes struggle to meet these diverse performance requirements. This study designed a conductive hydrogel (SPPM) based on an SA/P(HEA-co-AA) semi-interpenetrating network, incorporating PVA@MXene and LiCl. This hydrogel exhibited excellent mechanical properties (a high tensile strength of 546 kPa with an elongation at break of 300 %), good self-healing ability, cycling stability (withstanding 1000 cycles at 30 % strain), and a high conductivity of up to 6.91 mS/cm. The introduction of MXene promoted the rapid formation of the hydrogel network without heating, achieving rapid gelation in just 5 min. This hydrogel-based strain sensor demonstrated remarkable sensitivity (GF = 2.22, 0–50 % strain) to tiny strains (as low as 0.01 % with a significant resistance variation of ΔR/R₀ = 0.0257 %) and a fast response/recovery time (83/75 ms). Additionally, the single-electrode TENG (SPPM-TENG) constructed using SPPM hydrogel as the electrode demonstrates outstanding electrical output performance, generating a V_OC of 138 V, I_SC of 0.42 μA, Q_SC of 33 nC, and peak power density of 4.56 mW/m², capable of successfully driving low-power electronic devices. It can also function as a self-powered strain sensor to monitor human movement. The hydrogel reported in this study can be used for high-performance, multifunctional flexible strain sensors and TENG energy output, providing new ideas for the development of motion detection, energy harvesting, and self-powered flexible sensing systems.