Enhanced printed temperature sensors on flexible substrate

• The integration of the carbon black and a metallic oxide in a whetstone bridge enhanced of the sensitivity.
• The use of a PEN substrate gives a flexible and a conformal structure.
• The annealing of the sensitive inks at 130°C gives a good and stable electrical characteristics.
• Treating the ATO with an oxygen plasma enhanced its TCR and then the sensitivity of the temperature sensor.
• The passivation of the temperature devices by using a fluoropolymer prevents from the humidity.

In this paper we present the development of enhanced printed temperature sensors on large area flexible substrates. The process flow is a fully screen printed technology that uses exclusively solution-processed materials. These Screen printed temperature sensors are based on resistive pastes integrated in a Wheatstone bridge circuit. Substrate is a commercial Poly Ethylene Naphtalate (PEN) with a thickness of 125 µm. Functional temperature sensors are demonstrated and characterized with good electrical properties, showing a good sensitivity of 0.06 V/°C at Vin=4.8 V. This sensitivity is enhanced by the annealing and the O2 plasma treatment. Based on this temperature sensor, we have developed a demonstrator for human body temperature detection.

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