Improvement of a flexible multimode pressure-strain sensor (FMPSS) for blueberry firmness tactile sensing and tamper-evident packaging

Advanced sensors have gained widespread use in determining fruit freshness characterization indicators, with researchers striving for high sensitivity, a broad detection range, and cost-effectiveness. In this study, we present a flexible multimode pressure-strain sensor (FMPSS) that employs Au electrodes and PEDOT/PSS films for tactile sensing of blueberry firmness and tamper-evident packaging. The FMPSS was fabricated using an ion sputtering technique, incorporating serpentine-shaped Au electrodes and PDMS encapsulation for the force-sensitive films. Our prepared FMPSS demonstrates exceptional linearity and repeatability across a detection range of 0-1200 kPa. Furthermore, it exhibits rapid response/recovery times, long-term cycling stability, and notable sensitivity to subtle deformations. Multiple applications of the FMPSS in fruit quality control were demonstrated, employing a multi-mechanism and modular approach. The pressure mode of the sensor enables instant and rapid assessment of blueberry firmness, achieving an average sensing accuracy of 88.75% when combined with the ANN model. Additionally, the strain mode accurately detects the unsealed state of the blueberry package, highlighting its potential for tamper-evident applications. The flexibility and convenience of the FMPSS make it suitable for assessing the firmness of various fruits and integrating it with fruit packaging and robotic systems. This versa-tility positions the FMPSS as a promising tool with diverse applications in fruit quality control.