Piezoelectric [trimethylchloromethyl ammonium][CdCl3] microrods/PVC composites for high-fidelity ultrasound detection in the mid-frequency range

Abstract

Ultrasound detection and acoustic imaging technologies have broad applications in biomedical diagnostics, flexible wearable devices, and human-machine interaction. Conventional inorganic piezoelectric ceramics exhibit high acoustic impedance and large mechanical rigidity. This results in poor impedance matching not only with propagation media such as water but also with soft biological tissues, leading to significant energy reflection, scattering, and signal distortion. To address these limitations, we developed polymer/organic-inorganic hybrid metal halide composite films and devices, using TMCM-CdCl₃ MRs (TMCM = trimethylchloromethyl ammonium; MRs = microrods) as fillers and poly(vinyl chloride) (PVC) as the matrix. Strong interactions between PVC and the one-dimensional hybrid perovskite lead to a highly coupled micro-scale interface, while the polymer’s inherent flexibility and the composite’s low acoustic impedance suppress reflection and scattering, enabling high-fidelity signal transmission. Devices based on TMCM-CdCl₃ MRs/PVC demonstrate superior ultrasound detection performance compared to conventional PVDF and PZT materials. At 10 MHz, the composite films maintain a frequency-domain signal fidelity of 74.1% (corresponding to a time-domain fidelity of 91.2%), with output comparable to commercial PZT devices. Additionally, the devices exhibit excellent piezoelectric energy harvesting capability and can accurately sense various human motions. These results highlight the significant potential of metal halide/polymer piezoelectric composites for advanced ultrasound sensing and energy harvesting applications.