Strain-enhanced stretchable molecular ferroelectric acoustic fibers

Molecular ferroelectrics-hybrid organic-inorganic architectures that exhibit piezoelectric coefficients comparable to classic oxide ceramics while offering rich compositional and structural tunability-have emerged as promising materials for human-interfaced high-frequency acoustic sensing. Nevertheless, the inherent brittleness and relatively high modulus hinder their practical deployment on dynamically deformable interfaces. Here, we report stretchable molecular ferroelectric acoustic fibers fabricated by incorporating molecular ferroelectric trimethylchloromethyl ammonium trichlorocadmium (TMCM-CdCl₃) crystals into flexible thermoplastic polyurethane (TPU) via electrospinning. Intermolecular interactions between TMCM-CdCl₃ and TPU, along with the interlocked layered architecture between electrodes and fibers, endow the fiber acoustic sensor with high stretchability (tensile strain >100%), high force sensing sensitivity (4.36 V/kPa), and wide-frequency acoustic sensing (30-5000 Hz). Crucially, a strain-induced sensitivity enhancement effect is proposed and verified, where the acoustic sensitivity of the sensor increases from 15.03 mV/dB to 30.16 mV/dB under strain. Furthermore, we demonstrate that the acoustic fiber can maintain a high speech recognition accuracy (97.05%) even for mixed speech data obtained using the acoustic fiber in original and 20% tensile strain states. This work establishes a route for acoustic sensing at dynamic deformable interface and advances human-interfaced acoustic applications such as robotic interaction, biomedical engineering, and virtual reality.