Development and characterization of high-performance gas sensors


© Fraunhofer EMFT
Environmental gas chamber enables to characterize sensors and devices

The demand for sensitive, stable and long-lasting gas sensors is growing constantly – but the sensors currently available on the market do not generally meet all three of these requirements to an equal extent. Fraunhofer EMFT scientists are working on optimized solutions for chemical gas sensors, e.g. for CO2. One goal is to gain a better understanding of sensor properties so as to be able to select the most suitable sensors for specific applications. In addition, the team is working to develop novel gas sensors that go beyond the current state of the art. The aim is to transfer the new insights to the market more quickly through close collaboration with two industry partners.

Researchers have a number of focus areas in their R&D activities: one approach is to synthesize novel materials – so-called hybrid organic-inorganic nano-materials – which exhibit high sensitivity towards specific gases such as CO2. In order to be able to subject commercial and internally developed sensors to comprehensive testing, the team has also set up a gas measuring station at Fraunhofer EMFT. This set-up allows sensors to be characterized under the influence of various gases (CO, CO2, H2S, acetone, ethanol, SO2, NOx). In the climate gas chamber it is possible to reproduce air humidity levels of between 5% and 90% and temperatures of 0°C to 100°C; furthermore, mixtures of up to three gases can be selected. The researchers use impedance spectroscopy to measure the electrical properties of the sensors in situ at various humidity levels.

Furthermore, the research team has developed a miniaturized evaluation kit as a useful addition to the gas measuring system. This approximately palm-sized device allows precise measurement of sensor response and recovery times. A conventional gas measuring system is not suited for this purpose since a complete gas exchange in the test chamber generally takes several minutes. The set-up consists of a PEEK cover which is screwed to a circuit board with a sealing ring. Three sensor sockets are positioned on the circuit board in order to achieve a gas exchange time and a measuring interval of approx. 350 ms.