Screen-Printed Flexible Strain Sensors with Ag Nanowires for Intelligent and Tamper-Evident Packaging Applications

The printed electronic technology, a simple, low-cost, and high-throughput method, exhibits great potential applications in various fields, particularly in intelligent and tamper-evident packaging. In this study, an all-printed flexible sensor is prepared for sensing tamper-evident packaging by screen printing the water-based silver nanowires (Ag NWs) conductive ink onto a polyethylene terephthalate substrate. This bendable sensor shows a corresponding variation relationship between the resistance of the Ag NWs layer and bending angles. In addition, it presents a stable resistance sensitivity at the bending angles of 45°, 90°, and 135°. The mechanisms of different printed structures on the sensitivity of the sensor have been discussed. The results show that the straight-line sensor with a linewidth of 2.0 mm has the best sensitive performance (the gauge factors at bending angles of 45°, 90°, and 135° are 37.1, 39.3, and 39, respectively). Moreover, the sensor exhibits a long-term mechanical cyclic stability (no apparent decay after 1000 bending cycles) and excellent adhesion performance (no distinct increase in resistance after 20 times). Because of the excellent sensing performance, the Ag NWs-based flexible sensor can accurately detect the opening status of the packaging, showing promising potential for practical tamper-evident applications.