Development Of Novel Electronic Nose Systems Based On Bulk Acoustic Wave Resonators

Gas detection is an important research direction in the field of instrument science.The effective measurement and real-time monitoring of gas components play an important role in applications such as environment,national security,health and medicine.In general,gas detection systems consist of sensor technology,signal processing technology,signal transmission technology and control technology.However,there are still challenges remaining in the development of gas sensors such as the rapid analysis of complex components as well as the realization of a portable analysis system.Nowadays,the traditional spectroscopic and chromatographic techniques are gradually replaced by the novel electronic nose systems based on sensor arrays.However,there are still some issues in electronic noses such as bulky size,single sensing mode and poor sensitivity.For the engineering issues listed above,we have developed a series of electronic nose systems based on film bulk acoustic resonators(FBAR)fabricated by micro electro mechanical system(MEMS)technology.The analysis of simple or complex gas components were achieved with these systems by conducting chemical modifications and mathematical algorithms.The main topics of this thesis are listed as follows:1.An electronic nose system based on FBARs modified with self-assembled monolayers was proposed.Multiple chemical functionalization was achieved by vapor phase deposition of silylating reagents on nine FBAR sensors.Three adsorption affinities and kinetics parameters of five volatile organic compounds(VOCs)interactions with these functional sensors were modelled to provide a multiple concentration-independent fingerprint library,offering a more direct and accurate method for VOCs discriminations.2.A dual-mode electronic nose system was proposed.The system,which comprises a silicon nanoribbon field effect transistor(Si-NR FET)and a FBAR,was successfully applied for the detection of two Freon vapors.The properties of the vapors were found to be quite similar except for polarity.Experimental results show that qualitative discrimination can be realized by the Si-NR FET due to its polaritysensitivity,while the quantitative concentration detection of Freons can be realized by the FBAR through gravimetric measurement.Moreover,Freon mixtures are analysed based on the complementary characteristics of the two types of sensors.Our results suggest that the proposed dual-mode electronic nose provides a more accurate method compared with conventional approaches.3.An electronic nose system based on virtual sensor array was proposed.By employing a single FBAR sensor capable of producing multiple responses to VOCs at different input powers,the electronic nose can simulate the response spectrum of gas sensor with arrays.Based on algorithms,individual VOC identification and VOCs mixtures classification were successfully realized.Such an electronic nose can significantly reduce the device damage probability and improve the usage of the system.4.A portable gas chromatography consists of FBAR gas sensors and gas chromatography technology was proposed.The system mainly comprises a gas transmission system,a sensing circuit,a pre-concentration module,a chromatographic column module,a FBAR sensing module and a temperature control module.Experimental results show that the system can effectively separate and detect alkane mixtures,leading to the expected analysis performance.