Abstract:
For many years, the detection of explosives and illegal drugs has been a major challenge which aligns with the speeding process of globalization. In particular, the illicit drug market is in continuous growth, as indicated by the 2.4 million drug seizures made by law enforcement. Therefore, the demand for alarm technologies that can be effectively used for developing illicit drug and explosives detection sensors becomes even more urgent.
Under this point of view, electronic nose (e-nose) technologies meet all the above requirements, combining the data obtained by a sensor array selected for target application with computational intelligence to make an efficient chemical detection system. Of the various e-noses developed, the ones based on surface acoustic wave (SAW) devices are among the most sensitive. In addition, SAW vapor sensors are fast, highly sensitive and reversible. Their fabrication methods are compatible with standard integrated circuit technology, which makes them suitable for volume production and, hence, for cost reduction.
Nowadays, however, e-noses based on SAW vapor sensors are used only for some very specific applications like detection of explosives and warfare agents. One of the main reasons for lack of a commercial development of SAW e-noses could be related to the available deposition techniques for the sensitive layers. In fact, SAW sensors require a uniform (i.e. continuous, uniform in thickness and hole-free) active layer along the wave propagation path in order to prevent high attenuation and degradation of the Q-factor. In this work, we will show that we can use different nanocomposites, i.e. polymers (for example poly[3-(6-carboxyhexyl)thiophe-2,5-diyl]) : graphene, as active materials. These could be printed solvent free by the laser (no clogging of nozzles or creating of special inks) and show sensitivities below 100 Hz/ppm for dimethyl methylphosphonate (a simulant for sarin gas), dichloromethane and ethyl acetate.
The SAW e-nose system is based on an array configuration composed of six SAW resonators coated with five different polymers, plus an uncoated SAW device used as reference. In particular, laser-induced forward transfer was applied for the coating of SAW sensors with different nanocomposite layers. The nanocomposites as active materials detect different chemical interaction affinities of the vapors in a manner in which pattern recognition methods succeed in discrimination between target vapor classes and interferents.
References:[1] M. Benetti, D. Cannata, E. Verona, A. Palla-Papavlu, V. Dinca, T. Lippert, M. Dinescu, F. Di Pietrantonio, Highly selective surface acoustic wave e-nose implemented by laser direct writing, Sensors and Actuators B: Chemical (2019)
[2] A. Palla Papavlu, T. Mattle, U. Lehmann, A. Hintennach, A. Griesel, A. Wokaun, T. Lippert, Scientific Reports 6, 25144 (2016)
[3] A. Palla Papavlu, M. Filipescu, S. Vizireanu, L. Vogt, S. Antohe, M. Dinescu, A. Wokaun, T. Lippert, Applied Surface Science 374, 312-317 (2016)
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