A multi-functional VOC (volatile organic compound) sensor composed of four parallel-connected quartz crystal resonators (QCRs) configured as a cascaded resonator was developed for VOCs identification and quantification. The structure of the cascaded resonator allows the high-resolution output response signals from the four QCRs to be obtained through a single measurement. Multi-parameter responses for each QCR can be calculated to form a hybrid sensor array, combining the advantages of multisensor array (MSA) and virtual sensor array (VSA), significantly enhancing the sensor’s ability to identify both similar and diverse types of VOCs. Results show that the highest sensitivity is 16.14 Hz ppm−1, with the lowest limit of detection is 0.34 ppm, exhibiting excellent sensing performance. Classification accuracy to eight VOCs is 98.68% of the hybrid sensor array. This development is of significant importance for the realization of artificial olfaction.

The significant growth of wearable electronics is in constant search for optimizing systems with high flexibility and self-powering capacity. In this work, we utilize flexible polypropylene ferroelectret (PPFE) thin film polymer with the large transverse piezoelectric coefficient for bending curvature self-powered sensing. The electric energy comes from the geometry distortion of the built-in macro dipoles with initial surface charge distributions. Theoretical analysis based on constitutive electromechanical equations and bilayer bending mechanics provide a detailed understanding of the sensing mechanism and its applicability. Different evaluation methods are used to have a more comprehensive understanding of the electromechanical responses under different bending conditions. It has been found that the velocity and magnitude of the mechanical input influence the average voltage output, while instantaneous voltage is not dependent on the latter. The robustness of the material is also investigated, where the device shows no performance degradation by immersion into the water up to 12 hours and under 10k bending cycles. Thermal stability tests reveal degradation starting at ~ 75°C and an immediate failure of the device at ~ 150°C. Finally, an application is demonstrated by showing the potential use of the characterized system as a self-powered sensor for athletic assessment.