Self-sensing piezoelectric Bi₂WO₆ electrode for in-situ monitoring interfacial acoustic cavitation

To tackle the critical challenge of in-situ monitoring for acoustic cavitation intensity at the liquid-solid interface in sonochemical reactions, a self-sensing electrode based on piezoelectric nanosheet arrays was developed. Utilizing Bi₂WO₆ (BWO) as a model piezoelectric material, the self-sensing detection electrode (BWO SSDE) incorporates a sandwiched layered structure: a functional BWO nanosheet/FTO substrate layer, filled with a flexible insulating elastomer for efficient mechanical-to-electrical conversion while preventing electron leakage, capped by a thin Ag film electrode to collect electrical signals. High-resolution sound pressure spectrograms were acquired during ultrasonication through advanced signal processing and calibration algorithms. This enabled systematic analysis of sound pressure level (SPL) variation characteristics at fundamental and harmonic frequencies across diverse ultrasonic conditions. Validation confirmed that the third-harmonic frequency SPL (SPL_60 kHz) stably quantifies interfacial acoustic cavitation intensity, achieving a detection sensitivity of 0.2 dB/μm. This system was further extended to monitor sonochemical induced self-assembly reactions of organic molecules, in-situ tracking the dynamic correlation between the evolution of polyphenol aggregation (PAs) structures and interfacial SPL under ultrasonication. The proposed piezoelectric-based acoustic self-sensing system not only provides a new method for precise and real-time monitoring of acoustic cavitation intensity at liquid-solid interface but also establishes a new paradigm for constructing sensing devices using diverse piezoelectric materials.