Flexible Bulk Acoustic Resonator Radio Frequency Sensor Based on PETA/Pb_1.2(Zr_0.52Ti_0.48)O₃/Polymer Films Detecting Human Respiratory Humidity

A flexible bulk acoustic resonator radio frequency (RF) sensor has been developed utilizing a PETA/Pb1.2(Zr0.52Ti0.48)O3/polymer thin film configuration tailored for detecting human respiratory humidity. Leveraging the exceptional water absorption properties of pentaerythritol tetraacrylate (PETA) and the impressive piezoelectric effect of Pb1.2(Zr0.52Ti0.48)O3, the sensor exhibits outstanding flexibility and sensitivity to humidity changes. An experimental analysis conducted under controlled humidity conditions using an RF test setup demonstrates the sensor’s high accuracy and rapid response time in detecting human respiratory humidity. Notably, the sensor displays a strong linear correlation between the resonant frequency and humidity level within the relative humidity range of 65 to 86%, with a correlation coefficient reaching 0.99. This aligns with the typical humidity range of exhaled water vapor from the human body, with a measured response time of 1.79 s. Remarkably, the sensor remains insensitive to temperature fluctuations, ensuring a consistent performance across varying environmental conditions. Moreover, its flexible design enables seamless integration into wearable devices, facilitating real-time monitoring of respiratory conditions and enhancing healthcare outcomes. This innovative sensor marks a significant advancement in RF sensing technology, holding immense promise for personalized health monitoring and healthcare applications.