Piezoelectric Heterojunction-driven Biomedical Revolution: From Construction Principles to Diagnostic and Therapeutic...

Piezoelectric heterojunctions are emerging as a transformative class of smart biomaterials, revolutionizing biomedical applications through their unique mechano-electrical coupling effects. A central challenge hindering their full potential lies in the systematic understanding and utilization of their complex interfacial enhancement mechanisms. This review aims to establish a comprehensive framework that bridges fundamental principles to clinical translation. We begin with an in-depth analysis of the core enhancement mechanisms in piezoelectric heterojunctions, focusing on the synergistic interplay between the built-in electric field and band engineering that promotes efficient charge separation. We then provide a critical discussion of the ongoing debate surrounding their catalytic mechanism, reconciling the distinctions and connections between band theory and the surface screening charge model. Furthermore, we construct a multidimensional classification system centered on material dimensionality and composition to offer systematic guidance for the rational design and performance optimization of piezoelectric heterojunctions. In terms of applications, this review offers a comprehensive survey of the cutting-edge progress of piezoelectric heterojunctions in efficient cancer therapy, tissue regeneration, antibacterial strategies, and self-powered biosensing. We emphasize that the superiority of these heterojunctions stems from their ability to overcome the bottlenecks of low efficiency and mono-functionality inherent in single-component piezoelectric materials through sophisticated interface design, while also maximizing therapeutic outcomes via multimodal synergistic strategies. Finally, we critically analyze the formidable challenges this field faces concerning biosafety, scalable fabrication, and clinical translation, and offer perspectives on its future development toward intelligent theranostic systems. This review is intended to provide solid theoretical guidance and forward-looking insights for the design of next-generation, high-performance piezoelectric biomaterials.