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  Surface acoustic wave sensor

Project results :

The general objective of the project was development of the intelligent detector to identify the toxic gases in the range of neurotoxic gases or with general action (chemical warfare agents, industrial toxic gases).  The obtained detector is of Matrix-type with 6 surface acoustic wave sensors (SAWS), which allow detection and quantification of three toxic gases at a level of ppm concentration in air.
            The elementary surface acoustic wave sensor is of "delay line" type with a central frequency of about 70 MHz, and the interdigital transducers have a double comb structure. Piezoelectric quartz substrate was chosen having ST-X cut in order to minimize the temperature effect. . The interdigital transducers were made of gold (150 nm) deposited on a chromium buffer layer (10 nm) which allows a good adhesion on the piezoelectric substrate.
            In order to select the sensitive films with the best sensitivity and response time various polymer films were studied: polybutadiene (PBD), polyisoprene (PI), polydimethylsiloxane (PDMS), polyethylenimine (PEI) and SiO2/Si, TiN, TiO2, Co3N nanoparticles and carbon nanotubes (MWCNT) embedded in polymer.
            The sensors with polymer film PBD, PI, PDMS, PEI on four types of chemical warfare agents were tested: chloropicrin, hydrogen cyanide, lewisite and soman. Sensors sensitivity was between 0.1 to 2.7 Hz / ppm and absolute sensitivity of 1.4 to 33.4 kHz/ ppm / kHz. For chloropicrin and soman the best detection limit (LOD) was obtained with PI sensor (130.4 ppm and 51.5 ppm), while in the case of hydrogen cyanide and levizita with PEI (300 ppm and 44.9 ppm ).
            The sensors with nanocomposite film based on SiO2/Si, TiN, TiO2, Co3N nanoparticles embedded in (PEI) polymer were tested. The sensitivity is between 0.09 to 2.31 Hz / ppm and LOD has values between 39 and 1035 ppm. For chloropicrin and soman the best sensitivity and LOD was obtained with PEI-SiO2 sensor while for lewisite, with Co3N -PEI sensor.
            Sensor performances with nanocomposite film (SiO2/Si nanoparticles embedded into the polymer and MWCNT) with those of the sensor with PEI polymer film were compared. Tests were performed on volatile organic substances (ethanol, methanol and toluene). The results showed a significant improvement of  nanocomposite film sensors performances. Response time was 12 s and 10.5 s for MWCNT-PEI, respectively SiO2/Si, being 5-6 times faster comparing with PEI-film sensor. SiO2/Si-PEI sensor had the best LOD value of 15.2 ppm, 16.7 ppm and 13.8 ppm in ethanol, methanol, and toluene, respectively. The limit of detection is an order of magnitude better than the sensor with carbon nanotubes and 55 times better than the polymer film sensor.
            The project had four main research directions:
- Research concerning synthesis and characterization of nanocomposite films based sensitive materials embedded with nanoparticles and their response to various toxic chemical agents –the project has been shown that using nanocomposite materials the sensitivity and response time are substantially improved..
- Development of the algorithm and related software necessary to identify and quantify toxic gases – Software that allows identification and quantification of three toxic gas sensors using 6 sensors was developed. The software based on responsively to individual sensor on the toxic gas and depending on the nature of the material which chemically sensitive film is made.
- Development of electronic signal processing system - the electronic system for processing electrical signals from individual sensors was designed and developed. The electronic system processes simulate the input from the six sensors, and provide them to identification and quantification algorithm.
- Execution, testing and demonstrating the functionality and usability of intelligent detector - The intelligent detector consists of -sensor matrix, the electronic system and recognition algorithm was tested on real gases fight, and demonstrated its functionality and utility. It had also been studied humidity and temperature influence on the elemental response sensor. On the national level for the first time in Romania has developed such a surface acoustic wave sensor. This project was an obvious gain in developing sensors for the military, but also for the protection of the individual terrorist actions, and environmental protection.
            As a new NATO member, Romania will be able to upgrade its military equipment. Therefore a principal user is the Ministry of Defense. Also and other protection and services are directly interested: environmental agencies, police and fire departments, municipal authorities, and not least the Ministry of Environment and Water Management. The gained knowledge enables further development of other applications using sensors for a much wider range of gases, explosives, drugs, etc. but with applications in medicine (biosensors) also.
            The results of the project has been valued by 12 articles, from which  8 are ISI, 6 papers presented at conferences one of which was entitled "Best Paper Award" at the international conference CAS 2009 and a web page where the results of the project are presented.
            The project gives the opportunity of Romanian SMEs in specialized units of the Ministry of Defence of advanced products at European level. In this project, The project a company from SME category SC PRO ENGINEERING SRL was involved, a member of UTI, towards the technological transfer will be directed, leading to potential economic growth and increase turnover. S.C. PRO ENGINEERING SRL is directly interested in the production and sale of these detectors.
            Also, the project had an important social impact, being involved eight young people from which four young doctoral students with specialties in engineering, chemistry and physics.


    • C. Grigoriu, C. Viespe, D. Drăgulinescu, C. Blănaru, O. Iancu, N. Grosu , I. Cristea, B. Saucă, C. Toader, M. Mihalcea, Surface acoustic wave sensors for the detection of chemical warfare agents, Tehnica Militara, nr. 1, 2007, p. 27-31, 2007
    • C. Viespe, C. Grigoriu, C. Toader, N. Grigoriu,Detection of chemical warfare agents using surface acoustic wave sensors with different polymer coatings,IEEE CAS 2009 Proceedings, ISBN 978-1-4244-4413-7, p. 263-266, 2009
    • B. I. Ion, F. Ioana, P. Cornel, C. George, A. E. Şuşu,Delay Optimum and Area Optimal Mappingof K-LUT Based, FPGA Circuits,Control Engineering and Applied Informatics, Vol 11,No 1, ISSN 1454-8658, pp. 43-48, 2009
    • B. Ion, S. Costin, S. Adrian, C. Nicolae, Power Consideration in Mapping LUT Based FPGA Circuits, Proceedings of the 2009 IEEE 5th International Conference on Intelligent Computer Communication and Processing", ISBN: 978-1-4244-5007-7, pp.369-372, 2009
    • B. I. Ion, C. Nicolae, S. Adrian, Ş. Costin, R. Florin, Heuristic Performance Optimal and Power Conscious for K-LUT Based FPGA Technology Mapping, Proceedings of the 1st WSEAS the International Conference on Manufacturing Engineering, ISBN: 978-960-474-121-2, Transilvania University of Brasov, 2009.
    • Ioan Roman, Cornel Fratila, Eugeniu Vasile, Alexandru Petre, Maria-Laura Soare, Achievement and evaluation of some ceramic nanostructured titanium oxide-layers, Materials Science and Engineering B, ISSN: 0921-5107, Ed.Elsevier, 165, no.9, 2009, p.207÷211
    • M.Sima, E. Vasile, Mariana Sima, Electrochemically deposited thermoelectric Bi2(Se,Te)3 nanowires, Journal of Optoelectronics and Advanced Materials , Rapid Communications Vol.3, No.6, p.539-542, 2009
    • M. Cernea, L. Trupina, C. Plapcianu, R. Trusca, C. Galassi, Evolution of the surface morphology with temperature, in oxidant atmosphere, of Ba (Ti1-xSnx)O3 (x = 0.13) thin films, JOAM-RC, 3 [9] 947-950, (2009)
    • C. Viespe, C. Grigoriu, Surface acoustic wave sensors with carbon nanotubes and SiO2/Si nanoparticles based nanocomposites for VOC detection,  Sens. Actuators B:        Chem. (2010), Sens. Actuators B: Chem.,  Vol 147, pp. 43-47 (2010)
    • Bucur,  S. Serban, A. Surpateanu, N. Cupcea, C. Viespe, C. Grigoriu, C. Toader, N. Grigoriu, The development of a sensor array for the detection and recognition of chemical warfare agents, Acceptata spre publicare IEEE CAS 2010 Proceedings 
    • C. Viespe, C. Grigoriu, C. Toader, I. M. Popescu, Nanocomposites coated surface acoustic wave sensor for chemical warfare agent detections, acceptata spre publicare in Buletinul Politehnicii, seria A (2010)
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