Piezo-Coupling Effects in Smart Polymers: Toward Ultrasensitive Sensing and Biomedical Applications.

The integration of piezoelectricity with other physical effects-such as pyroelectric, triboelectric, and photovoltaic effects-has enabled the development of multifunctional, self-powered sensors with enhanced sensitivity and application versatility. Central to this advancement is the use of stimuli-responsive smart polymers, which offer mechanical flexibility, biocompatibility, and tuneable properties essential for wearable and implantable biomedical applications. By harnessing piezo-coupling effects in stimuli-responsive polymers, these systems overcome the current limitations of monofunctional rigid sensors, offering reduced structural complexity while improving sensitivity and energy efficiency. This review outlines the fundamental principles of these piezo-coupling effects, highlights key stimuli-responsive polymeric materials with fabrication strategies, and discusses recent progress in device architectures tailored for ultrasensitive sensing and biomedical applications. Finally, it addresses current challenges and future directions for scalable, ultrasensitive, and multifunctional polymer-based sensing platforms.