Freestanding PZT Films for Integrated Wearable Sensing and Intelligent Acoustic Recognition

Flexible, self-powered sensors are pivotal for next-generation human-machine interfaces. However, substrate-induced clamping fundamentally restricts their electromechanical performance by suppressing longitudinal deformation, thereby reducing signal sensitivity. Here, we report a high-performance freestanding PbZr_0.52Ti_0.48O₃ (PZT) thin film based on a layered Mica/Pt/LaNiO₃ heterostructure. The complete release of substrate constraints unlocks markedly enhanced properties, including a 1.4-fold increase in remanent polarization (P_r = 54 vs. 40 µC cm^{- 2}), a 2.2-fold enhancement in the effective converse piezoelectric coefficient (d₃₃ = 390 pm V^-1 vs. 174 pm V^-1), and an approximate 1.5-fold improvement in dielectric permittivity. Consequently, the device exhibits rapid electromechanical transduction with an ultrashort pulse duration of 500 µs, alongside high output voltage and power. Integrated onto the human body, the sensor delivers sensitive, repeatable responses to various biomechanical motions. Beyond tactile sensing, the device enables high-fidelity acoustic detection and intelligent signal analysis. By implementing harmonic evaluation and principal component analysis, the system achieves reliable discrimination among musical instruments with distinctive spectral fingerprints. Collectively, this work establishes the freestanding PZT film as a multifunctional platform integrating energy harvesting and intelligent acoustic recognition, offering new pathways for self-powered biointegrated electronics.