An Implantable Flexo‐Ferroelectric Sensor Enabled by a Bioresorbable Nanocrystal‐Nanofiber Heterostructure for Monitoring Internal Soft Tissue Strains

ABSTRACT Implantable sensors are crucial for real‐time monitoring of internal soft tissue biomechanics, yet existing systems rarely combine high sensitivity, flexibility, and biodegradability. Here, we present an implantable sensor by engineering a flexo‐ferroelectric nanocomposite, where ferroelectric β‐glycine nanocrystals are in situ‐grown and stabilized along poly( L ‐lactic acid) (PLLA) nanofibers via an electric field‐assisted nanoconfinement strategy. This approach first uncovers flexoelectricity in PLLA nanofibers and template‐freely stabilizes pure β‐glycine nanocrystals without brittle polymer matrices. These components form a structurally coupled, self‐assembled interface, creating a co‐active charge generation network that integrates flexoelectric and ferroelectric effects new mechanism not previously demonstrated. Our sensor achieves unprecedented electromechanical performance, including piezoelectric coefficient of 246 pC/N, sensitivity of 205 mV/kPa, detection range of 3.5‐110 kPa, and tissue‐matched compliance. The integrated performance surpasses all reported bioresorbable sensors and commercial polyvinylidene fluoride‐based devices. Functionally, it demonstrates layer‐specific compatibility across soft tissues, capturing strain from surface to deep regions with minimal signal disruption. In vivo validation in rodent and rabbit models enables continuous cardiovascular monitoring and, notably, discriminates between metabolic and mechanical modes of acute heart failure. This work establishes a universal sensing platform for high‐fidelity soft tissue strain mapping, with broad implications for personalized mechano‐diagnostics across multiscale physiological systems.