Multifunctional E‐Tattoos Based on Electrospun PVBVA Fibers Coated with Ti ₃ C ₂ T <i> _x </i> MXene for Energy Harvesting, Energy Storage, and Biometric Sensing

Multifunctional electronic tattoos (e-tattoos) integrating energy harvesting, charge storage, and biosignal monitoring are critical for advancing wearable electronics. Most current technologies specialize in one or two functions, lacking a unified, skin-compatible solution. A novel e-tattoo is reported using electrospun poly(vinyl butyral-co-vinyl alcohol-co-vinyl acetate) (PVBVA) fibers coated with titanium carbide (Ti₃C₂T_x) MXene. A single electrode triboelectric nanogenerator (TENG) was fabricated via a layer-by-layer method using a PVBVA/Ti₃C₂T_x/PVBVA (PMxP) sandwich structure, and achieved an open-circuit voltage of 250 V, short-circuit current of 2.9 µA, and power density of 250 mW m^- ² (25 µW cm^- ²) under a 2 MΩ load, enabling triboelectric energy harvesting from human motion. A parallel-plate capacitor using PVBVA/Ti₃C₂T_x electrodes and a PVBVA dielectric exhibited 14 pF capacitance at 10 kHz and 5 V, suitable for low-power touch-sensitive applications. Additionally, PMx-based e-tattoos captured real-time electrocadiogram (ECG) and electromyography (EMG) signals with high skin conformability and minimal signal degradation. The device maintains mechanical flexibility, biocompatibility, and adhesion over extended wear. This scalable, non-invasive platform demonstrates robust multifunctionality and durability, offering a promising route toward integrated, self-powered wearable systems for health monitoring, human-machine interfaces, and energy autonomy. The PMxP architecture represents a significant step toward all-in-one e-tattoos that meet the demands of next-generation electronics.