Influence of nano composites on reliability and mechanical properties of moisture sensors

There is a large demand on micro-electro-mechanical systems (MEMS) and sensors for the monitoring of physical and chemical processes in various application areas, i.e. in the field of medicine, security, sport and automotive engineering as well as logistics. Here, the measurement system can act as simple signal transmitter during the determination of critical conditions or is used for precise acquisition of physical values like temperature, pressure or relative humidity. Today most of the moisture sensors are based on ceramic dielectrics as part of the capacitor assembly. While using this material some disadvantages and limitations arise for these measurement systems as well as time and cost consuming manufacturing procedures. Sensor sizes are limited to ceramics sensitive and brittle mechanical properties and the use of flexible substrates is almost impossible. Due to these disadvantages arises a need for competitive integrated sensor systems as well as large area sensors, i.e. for monitoring of relative humidity in air conditions. The application of functional polymer based nanocomposites can meet these demands. New manufacturing technologies and favorable characteristics of the nanocomposites allow nearly any size of sensor geometry (square centimeter range) which can be fabricated cost efficient and in large quantities. Unlike silicone technologies, composites are producible under ambient conditions and on flexible substrates. Prototypes of a capacitive moisture sensor have been fabricated and verified according to their functionality and quality during a cooperation of the ChemnitzerWerkstoffmechanik GmbH and the Fraunhofer ENAS.