Printed Micro-Sensors for Simultaneous Temperature and Humidity Detection

In this paper, temperature and humidity sensors with dimensions less than 1 × 1 mm
²
are printed together on a flexible polyimide substrate to create a miniaturized sensing circuit. The humidity changes (RH 35%-95%) are detected by capacitance change of the printed Nafion thin film, while the temperature variation (15°C-80°C) can be detected by the resistance change of the printed NiO thin films. The two micro sensors are printed over a flexible substrate to create an RC circuit for simultaneous detection of temperature and humidity. An equivalent circuit model is also developed to describe the performance of the combined sensing device in a wide range of relative humidity and temperature range. This printed sensing device shows great sensitivity and response times and can be applied in environmental monitoring applications.