Fully Printed High-Density Temperature Sensor Array

Printed electronics is a rapidly expanding field benefitting from low-cost, flexible and scalable fabrication methods. This allows for new applications that were not realizable with traditional electronics. Especially the ease of use for small batch productions and tailor-made implementations accelerate this trend. In addition, when combining flexible printed electronics and traditional silicon-based electronics – so called flexible hybrid electronics - the respective advantages of both worlds can be utilized.<br/>Explicitly sensor applications have been revolutionized by printed electronics with the compatibility to flexible substrates and options for direct integration of the sensing systems on 3D structures. Making use of two fabrication methods, we developed a fully printed high-density temperature sensor array. The sensor layout is based on a passive matrix design yielding a total of 625 sensor pixels on a 12 mm by 12 mm active area. Each sensor pixel features a size of about 60 µm by 60 µm and a pitch of 500 µm to its neighboring pixels. Each pixel consists of 2 electrodes sandwiching the thermistor material. To fabricate the sensor array we used two methods, combining Aerosol-Jet printing and screen printing. Aerosol-Jet printing is used for the active sensor area depositing several layers on top of each other. Ultimately, the connection between sensor and readout electronics was established by screen printed supply lines. All silver electrodes were flash sintered to achieve high and consistent conductivity, while the thermistor material was temperature cured.<br/>A particular multiplexing unit was developed to evaluate the sensor array and to characterize its properties. To correlate the resistance values to the corresponding temperatures each pixel is calibrated. From the acquired data a fit function is calculated and assigned to each pixel. The sensor was operated in a temperature range of 0°C to 110°C showing a prediction accuracy of about +/- 1°C. Temperature cycling proofs the sensor stable to degradation and demonstrates its fast response times. Even after weeks of testing and rough handling the sensor is fully functional. The termistor material shows a nonlinear behavior with high sensitivity at low temperatures of &gt; 3.61 % / °C declining to a still satisfying value of &gt;0.48 % / °C at 90°C. Finally, the sensor was capable to resolve local heat sources and depicting them on a heat map.