Flexible Dual-Mechanism Pressure Sensor Based on Ag Nanowire Electrodes for Nondestructive Grading and Quality Monitoring of Fruits

To extend the application range of flexible pressure sensors and to be widely used as an economical and convenient way, researchers have made efforts toward high sensitivity, wide detection range, and low power consumption. However, most sensors can only work based on a single mechanism, thus limiting the sensing range and applicability. In view of this, we developed a dual-mechanism pressure sensor (DMPS) based on Ag nanowire/PDMS electrodes and ZnO nanoparticle-based force-sensitive membranes, which has a sandwich structure and complete flexibility under the effect of chemical bonding. It can simultaneously sense high-frequency dynamic pressure as well as static load by integrating piezoelectric and piezocapacitive effects, thereby complementing the inability of conventional piezoelectric-type sensors to continuously detect static pressure. The prepared flexible DMPS containing 20 wt % ZnO nanofiller has a pressure frequency-independent electrical output of about 2 V under 20 N force conditions and also has a long-term stability of more than 5000 pressure cycles. Moreover, it exhibits good linearity, repeatability, and stability in the 0–100 kPa detection range in the piezocapacitive mode. On the basis of multimechanism and modularity, the flexible DMPS was demonstrated for fruit quality monitoring, including avocado ripeness grading, tactile sensory gloves, and moisture loss assessment, indicating its promising applications in intelligent agricultural machines and wearable sensing systems.