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Sensor based RFID-identification system

: Wöllenstein, J.; Bauersfeld, M.-L.; Peter, C.; Oprea, A.; Weimar, U.; Schmidt, M.; Sayhan, I.; Becker, T.

AMA Fachverband für Sensorik e.V., Wunstorf:
SENSOR 2009, 14th International Conference on Sensors, Technologies, Electronics and Applications. Vol.2 : Nürnberg, Germany, 26 - 28 May 2009; Proceedings; Part of Sensor + Test Conference 2009
Wunstorf: AMA Service, 2009
ISBN: 978-3-9810993-5-5
International Conference on Sensors, Technologies, Electronics and Applications (SENSOR) <14, 2009, Nürnberg>
Sensor + Test Conference <2009, Nürnberg>
Fraunhofer IPM ()
RFID-technology; RFID and sensors; flexible sensor; humidity sensor; temperature sensor; TRACK

Daily, millions of goods are shipped around the globe. It appears as a logistical challenge to ensure, that all different goods reach their destination in acceptable condition. Many of them do not arrive in the same condition as they left the producer. Instead of perfect original goods, rusted vehicle parts, defective flat screens, spoiled medicine or overripe fruit arrive at their destination. Only in rare cases is it possible to determine clearly who is responsible and should bear the costs, because the goods generally go through many hands. So it is necessary, to have a reliable measurement technique, which offers transparency to all members of the supply chain. Therefore, a new, semi active, sensor based RFID-Identification system is presented. This RFID-platform offers a multi-chip solution with well-defined interfaces (I2C-bus) to the sensory unit. For the integration on flexible RFID-Tags novel temperature, humidity and light sensors were developed and characterised. Functional RFID-labels with integrated humidity and temperature sensors were built up for demonstration. To control the humidity of different logistic processes, a polymer based, capacitive humidity sensor on flexible substrate was developed. For this purpose, different polymers, substrates and electrode structures have been tested. The use of interdigital structures as electrodes allows an easy way of micromechanical structuring of the sensitive layer, that small sizes and economic mass production are possible. Due to the absorption of water in the polymer layer, the capacity of the sensor increas es and changes of capacity can be detected. Due to the darkness inside a logistic box, unauthorized opening or damage of the container can be detected with a light sensor. Additionally, light sensors can be used for monitoring of light sensitive goods, like food or pharmaceutical products. Under these circumstances, the light sensor offers high flexibility, efficiency and process integration. The energy diagram is shown in figure 3. The working principle can be explained as followed: Incident light activates electrons inside the dye from their initial state D to a higher D*. This state is only lasting shortly. During electrical relaxation, the electron doesnt hop back to his initial state, but to a more energetically in the TiO2. Out of the TiO2, the electron moves to the transparent electrode (ITO, Indium oxide, see TCO, transparent conductive oxide). Returning the electron over the back electrode to the dye closes the electric circuit.