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Intelligent sensing arrays for (bio)chemical analysis

№5 Department of Physics and Optoelectronics technical bases   
B.A. Snopok

Although numerous types of sensors are becoming well established in industry, agriculture, medicine and many other areas, the development of new sensing techniques and elements proceeds at an unprecedented rate. The economic and social importance of sensor applications in the modern society is determined by the need to monitor complex mixtures in different environments.

To obtain information about the multicomponent chemical media (MCM, i.e. foodstuffs, drugs, perfumes, etc.), traditional techniques (specific sensor sets) try to provide the highest selectivity toward a given analyte when detecting the useful signal against a background produced by attendant contaminants. At the same time, by analogy with the olfactory system, the MCM can be described not by a sum of their individual components but by some abstract representation – a chemical image (CI) - a virtual fingerprint with a set of intrinsic parameters for a given MCM. The instrumental systems based on arrays of low-selective/cross-reactive sensors that are used to form a CI of gaseous MCMs with further classification and identification using the pattern recognition techniques has been named “the Electronic Nose” (e-Nose). In order to realize this approach, it is anticipated to use arrays of sensors for mapping the MCM variety in the chemical space onto the m-dimensional response space (m is the number of sensors). The concept of using sensor arrays for chemical analysis offer advantages over individual sensors concerning sensitivity to a wider range of analytes, improved selectivity and the capability for recognition of both single and complex analytes.

The central unit of the e-nose prototype includes the USB powered single board based on special microprocessor (8 bit RISC microcontroller ATMEGA128 (ATMEL)) and high performance programmable logic solutions for realization the multichannel frequency counter (up to 303 MHz range). The system is able to work with quartz crystal microbalance (QCM) transducers with the main frequency up to 32 MHz. The stability of the instrument shown on right picture.QCM based oriented configuration operate with up to eleven QCM sensors in fully automatic regime (“measurement”/”cleaning”) with samples of different nature (liquids, powders, etc.). In simplest mode without coordination the electromagnetic valves as well as temperature stabilization system, the systems require only USB connection without additional power supplier. So, one can be used as element of portable personal gas monitor. The “Nose Analyser” software package control full measurement procedures, data processing, database formation of  chemical images as well as on-line identification.

More information regarding general approach and application examples please find in:

Snopok, B.A., Kruglenko, I.V. (2005):  Nonexponential relaxations in sensor arrays: forecasting strategy for electronic nose performance. Sensors and Actuators B: Chemical  106 (№1), 101-113.

Filippov, A.P., Strizhak, P.E., Serebry, T.G., Tripolsky, A.I., Snopok, B.A., Khavrus, V.O., Ivashchenko, T.S. (2005): New Materials of Coatings for Discrimination of Hydrocarbons by Multisensor System Combined with Gas Chromatograph. Theoretical and Experimental Chemistry 41 (6), 371-376.

Kruglenko, I.V., Snopok, B.A., Shirshov, Yu.M., Rowell, F. J. (2004): Multisensor systems for gas analysis: optimization of the array for the classification of the pharmaceutical products. Semiconductor Physics, Quantum Electronics and Optoelectronics 7(N2), 207-216.

Snopok, B.A.,  Kruglenko, I.V. (2002): Multisensor systems for chemical analysis: state-of-the-art in electronic nose technology and new trends in machine olfaction. Thin Solid Films 418, 21-41.

Kruglenko, I.V., Snopok, B.A., Shirshov, Yu.M., Venger, E.F. (2000): Digital aroma technology for chemical sensing: temporal chemical images of complex mixtures. Semiconductor Physics, Quantum Electronics and Optoelectronics 3 (N4), 529-541.