Stretchable Unsymmetrical Piezoelectric BiO2‐x Deposited‐Hydrogel as Multimodal Triboelectric Nanogenerators for Biomechanical Motion Harvesting

Abstract Enhancing the output performance of triboelectric nanogenerators (TENGs) is essential for increasing their application in smart devices. Oxygen‐vacancy‐rich BiO 2‐x nanosheets (BiO 2‐x NSs) are advanced‐engineered nanomaterials with excellent piezoelectric properties. Herein, a stretchable unsymmetrical BiO 2‐x NSs deposited‐hydrogel made of polyacrylamide (PAM) as a multimodal TENG is rationally fabricated, and the performance of TENG can be tailored by controlling the BiO 2‐x NSs deposition amount and spatial distribution. The alteration of resistance caused by the Poisson effect of PAM/BiO 2‐x composite hydrogel (H‐BiO 2‐x ) can be used as a piezoresistive sensor, and the piezoelectricity of BiO 2‐x NSs can effectively enhance the density of transfer charge, thus improving the output performance of the H‐BiO 2‐x ‐based TENG. In addition, the chemical cross–linking between the BiO 2‐x NSs and the PAM polymer chain allows the hydrogel electrode to have a higher tensile capacity (867%). Used for biomechanical motion signal detection, the sensors made of H‐BiO 2‐x have high sensitivity (gauge factor = 6.93) and can discriminate a range of forces (0.1–5.0 N) at low frequencies (0.5–2.0 Hz). Finally, the prepared TENG can collect biological energy and convert it into electricity. Consequently, the improved TENG shows a good application prospect as multimodal biomechanical sensors by combining piezoresistive, piezoelectric, and triboelectric effects.