Flexible Strain Sensor with NFC Tag for Food Packaging

In this work we present a polymer-based flexible strain sensor integrated with an NFC tag to detect strain by means of a visual LED indicator. The sensor was fabricated using conductive polymer poly (3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS) as an active material inside a flexible and transparent polymer Polydimethylsiloxane (PDMS) microchannel. The strain sensor changes its resistance at different bending conditions, showing up to three order increase in resistance for $\sim 100$ bending. A custom-developed passive NFC tag with an LED connected in series to the strain sensor is powered from an NFC reader to detect strain in a semi-quantitative way. The light intensity of the LED indicator is modulated according to the strain level, showing maximum brightness $(\sim 67$ lux) for relaxed or no strain condition, and being almost OFF $(\sim 8$ lux) for the maximum strain condition. The potential application of the NFC-based strain sensor system in food package for spoilage detection is also presented.