Integrated pre-concentrator gas sensor microsystem for ppb level benzene detection

Abstract An integrated microsystem for (indoor) air quality monitoring applications is presented. By combining a gas pre-concentrator based on metal-organic frameworks (MOFs) and a metal oxide semiconductor gas sensor, a device for detecting ppb levels of volatile organic compounds was designed, integrated and tested with benzene as a target gas. Two metal organic frameworks have been characterized for their suitability as gas pre-concentration materials for benzene and toluene using inverse gas chromatography and mass spectrometry measurements in order to obtain breakthrough values for gas adsorption. Both MOFs showed a higher pre-concentration effect compared to Tenax ® TA, a state-of-the-art commercial adsorbent material. By depositing a MOF material on a micro hotplate integrated in a package together with a gas sensor, an integrated gas sensor microsystem was realized. This system has been characterized in FEM simulations concerning its gas pre-concentration capabilities and behavior. Test measurements were performed using benzene at concentrations of 10–1000 ppb. Both the simulations and the measurements show the suitability of the system design for the task. Significantly increased gas concentrations have been observed during thermal desorption from the pre-concentrator after gas adsorption at a low temperature.