arXiv:2611.13300v1 Announce Type: new Abstract: This work presents the first demonstration of a submicrometer-thick thickness-field-excited (TFE) lithium niobate (LN) flexural-mode piezoelectric micromachined ultrasonic transducer (PMUT). A 670-nm-thick bilayer periodically poled piezoelectric film (P3F) 128Y LN is used to demonstrate a suspended membrane with an area of 0.25 mm$^{2}$, achieving a low resonance frequency of 33.4 kHz for airborne transduction. Its electrical measurements reveal an extracted effective electromechanical coupling efficiency ($k_{\mathrm{eff}}^{2}$) of 3% and a moderate static capacitance $C_0$ of 17 pF. Meanwhile, mechanical measurements using a laser Doppler vibrometer (LDV) yield a high quasi-static peak out-of-plane displacement ($\xi_{\mathrm{static}}$) of 145 nm/V and a high corresponding open-circuit sensitivity ($S_{\mathrm{OC}}$) of 1.4 mV/Pa in the audio band. The fabricated device is compared with state-of-the-art (SoA) airborne piezoelectric transducers with sub-100-kHz resonance frequencies, underscoring the potential of the TFE P3F LN transducer platform by simultaneously demonstrating strong actuation capability while featuring high sensitivity.