Multisensor arrays

Albert K., Walt D. R., Information coding in artificial olfaction multisensor arrays, Anal. Chem. 2003 4161-7. 

Monolithic sensor systems, however, offer advantages such as low power consumption or reduced packaging efforts. Integration of an on-chip serial interface reduces the number of bonding wires, especially in the case of an integrated multisensor array. Taking into account the mass-production facilities with estabhshed microelectronic and microtechnological processes, commercialization of monoHthic... 

The feasibility and limitations of using multisensor array systems in food and aroma applications will be discussed with an application intended to discriminate hop varieties [149] byway of example... 

The performance of common multisensor arrays is ultimately determined by the properties of their constituent parts. Key parameters such as number, type and specificity of the sensors determine whether a specific instrument is suitable for a given application. The selection of an appropriate set of chemical sensors is of utmost importance if electronic nose classifications are to be utilised to solve an analytical problem. As this requires time and effort, the applicability of solid-state sensor technology is often limited. The time saved compared with classic analytical methods is questionable, since analysis times of electronic nose systems are generally influenced more by the sampling method utilised than the sensor response time [185]. 

There are problems with this approach since enzymes isolated from natural sources such as the electric organ of electric eels often display low sensitivity and selectivity to the wide range of potential pesticide targets [21]. A possible solution to this is the development of a multisensor array where a variety of genetically modified acetylcholinesterases are immobilised on an array of electrochemical sensors and the responses from these are then processed via a neural network. 

Redox enzymes are the active component in many electrochemical enzyme electrode biosensor devices.1821 The integration of two different redox enzymes with an electrode support, in which one of the biocatalysts is photoswitchable between ON and OFF states, can establish a composite multisensor array. The biomaterial interface that includes the photoswitchable enzyme in the OFF state electrochemi-cally transduces the sensing event of the substrate corresponding to the nonphoto-switchable enzyme. Photochemical activation of the light-active enzyme leads to the full electrochemical response, corresponding to the analysis of the substrates of the two enzymes. As a result, the processing of the signals transduced by the composite biomaterial interface in the presence of the two substrates permits the assay of the... 

Photoswitchable redox-enzymes 1. Amperometric transduction of optical information - biocomputers 2. Amplification of weak optical signals -photonic amplifiers 3. Multisensor arrays — biosensor and bioelectronics 4. Photoelectrochemical systems Enzyme immobilized on electronic transducer... 

Keywords. Artificial nose, Chemical multisensor array, Artificial neural network, Bioprocess... 

Dramatic improvements have occurred in the technological development of multisensor arrays. High... 

Recent advances in the technology of multisensor arrays and neural computing have made the development of the electronic nose of great interest to the food industry for discrimination between odors (26). Provided the instrument has been calibrated properly, the technique is rapid, nondestructive, and objective. Shen et al. (27) found the electronic nose was capable of measuring changes in volatile compounds associated with lipid oxidation in canola, com, and soybean oils stored under accelerated conditions and Aparicio et al. (28) found the electronic nose could be calibrated to detect rancidity levels in good quahty ohve oil spiked with rancid olive oil. 

Carey W P, Beebe K R, Sanchez E, Geladi P and Kowaski B R 1986 Chemometric analysis of multisensor arrays Sensors Actuators 9 223-34 Booksh K S and Kowalski B R 1994 Theory of analytical chemistry Anal. Chem. 66 782A-91A... 

M. Penza, G. Cassano, Recognition of adulteration of Italian wines by thin-film multisensor array and artificial neural networks. Anal. Chimica Acta 509, 159-177 (2004)... 

Perhaps the area of analysis in which electrochemistry has had the biggest impact on society is in biosensors, notably the glucose biosensor [48], Although Volume 9 is concerned with bioelectrochemistry, it is important that this area of electroanalytical chemistry is represented appropriately in Volume 3. Consequently, Schuhmann and Bonsen provide an overview of the physical principles and appKcations of biosensors in Chapter 2.11. A comprehensive overview is given of amperometric, potentiometric, conducti-metric and impedimetric formats for biosensors, and the relative merits of each are fully assessed. Potential new directions are highlighted, particularly connected to miniaturization and multisensor array detection strategies. 

Miniaturization is intensively studied in present biosensor research [218] aiming at the development of total microelectro-chemical systems for local detection, multisensor arrays, implantable or portable devices. Not only the relevance of the items but also the electrochemical properties of microelectrodes that often make them superior to macroelectrodes allows miniaturization to become a necessity [219] see also Chapter 2.5 in this volume. 

In some situations it may be appropriate to use single-species biocatalysts where the response profile is known to match the expected analyte composition of the sample or environment to be monitored. In other situations it may be desirable to have as broad a response as possible in order to allow the detection of both the expected and unexpected. In these latter cases, a number of different microbial species may be used either in multisensor arrays or as a mixed microbial population incorporated into the sensor. 

The reduction of noise can also be achieved with SAW devices by using a reference oscillator. This procedure should be more effective with these devices, because both sensing and reference oscillators can be placed on the same substrate (e.g. side by side). The two oscillators will then see virtually identical conditions, and compensation for signal drift will be more effective. It should also be possible to construct multisensor arrays by placing many SAW device patterns on a single substrate, since these patterns become small at high frequencies. 

Albert KJ, Walt DR, Gill DS, Pearce TC (2002) Automatic decoding of sensor types within randomly ordered, high-density optical sensor arrays. Anal Bioanal Chem 373 792-802 Albert KJ, Walt DR (2003) Information coding in artificial olfaction multisensor arrays. Anal Chem 75 4161-4167... 

There are a lot of other, partly niche applications where glass electrodes according to the national and international standards are not perfectly suited. Planar technologies open up oppoitunities for new multisensor arrays including pH electrodes. Depending on the special application, besides glass membrane electrodes, also other types of pH electrodes play a role as separate probe and as well as a part of multisensor systems. 

Gardner JW (1991) Detection of vapours and odours from a multisensor array using pattern recognition principal component tmd cluster antilysis. Sens Actuators 4 109-115... 

For testing the chemical fiinction the chip can be clip-mounted in a fiow-through cell (fig2) The cell body made of Plexiglas is mechanically pressed against the chip surface sealed by an 0-ring The cell volume is about 1 pi Several cells can be stacked together to get a multisensor array... 

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