Printed Flexible Temperature Sensor with NFC Interface

Integration of sensors with antennas is becoming popular for compact high-performance wireless sensing systems. In this direction, here we present a silver electrodes and Poly(3,4-ethylenedioxythiophene:polystyrene (PEDOT:PSS) based printed temperature sensor on a flexible PVC substrate. The temperature sensor was characterised using a digital multimeter for a temperature range from 25°C to 90□C. The sensor showed a 70% change in resistance for the tested temperature range. Further, the sensing part was integrated with a Near Field Communication (NFC) tag with the data obtained semi-quantitatively by means of the intensity of an Light Emittign Diode (LED) connected with the antenna system. In this case, the antenna works as an energy harvester to power an LED indicator connected in series to the resistive temperature sensor. The intensity of the LED, which varies with the increase of temperature, was measured using a lux-meter mobile application. The intensity at 70□C was 42 lux whereas it decreased down to 14 lux at room temperature ( 25□C). The presented system showed potential use as a smart label in applications requiring temperature monitoring.