Integrated sensor arrays

Cunningham B., Weinberg M., Pepper J., Clapp C., Bousquet R., Hugh B., Kant R., Daly C., and Hauser E., Design, fabrication and vapor characterization of a microfabri-cated flexural plate resonance sensor and application to integrated sensor arrays. Sens. Actuators B, 73,112 -123, 2001. 

Figure 3. Picture of an integrated sensor array consisting of 20 FETs (of two different sizes). The transistors cover an area of 4x15 mm. The layout allows e.g. a temperature gradient and different gate materials to be applied along the array. The chip is mounted on a header which may be provided with a lid with gas inlet and outlet to obtain a miniaturized analytical system for small volumes and flows.

We suggested a more spectacular, two dimensional, development of integrated sensor arrays a few years ago to create what could be called an "olfactory camera" [6]. The olfactory camera is simply a chip with an array of field effect transistors, heaters and temperature sensors. The sensing transistors are coupled as diodes into which a constant... 

It can be concluded that gas sensors can be made very small and with small consumption of the molecules to be detected. They can, therefore, be used to analyze gas evalution from small samples and with small gas flows with both industrial and medical applications. Furthermore, the use of sensor arrays gives the possibility to construct electronic noses for more complicated situations related to identification, classification and quantification of gas mixtures or odours. The final microanalysis system for gases may perhaps consist of microfabricated gas handling, an integrated sensor array and a dedicated chip for signal treatment and pattern recognition. 

Integration of multiple functionalities - use of Microsystems can bring about a significant cost reduction compared to conventional solutions logistics and quality control can frequently be simplified when integrating several components in one system e.g. multiple sensor arrays. 

E. J. Cho and F. V. Bright, Optical sensor array and integrated light source, Anal. Chem., 2001, 73, 3289. 

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... 

Most microhotplate-based chemical sensors have been realized as multi-chip solutions with separate transducer and electronics chips. One example includes a gas sensor based on a thin metal film [16]. Another example is a hybrid sensor system comprising a tin-oxide-coated microhotplate, an alcohol sensor, a humidity sensor and a corresponding ASIC chip (Application Specific Integrated Circuit) [17]. More recent developments include an interface-circuit chip for metal oxide gas sensors and the conccept for an on-chip driving circuitry architecture of a gas sensor array [18,19]. 

S.A. Bota, A. Dieguez, J.L. Merino, R. Casanova, J. Samitier, and C. Cane. A Monolithic Interface Circuit for Gas Sensor Arrays Control and Measurement , Analog Integrated Circuits and Signal Processing 40 (2004), 175-184. 

Variations of semiconductor PL and EL intensities resulting from analyte adsorption are promising techniques for chemical sensing. When coupled with films such as MIPS, the selectivity of such structures may be improved. Integrated devices in which forward- and reverse-biased diodes are juxtaposed using microelectronics fabrication methods provide an opportunity to create completely integrated sensor structures on a single chip and to prepare arrays of such structures. 

In order to obtain the output of a sensor, we need to integrate the response over all possible wavelengths. Let E(X, x/) be the irradiance of wavelength /. falling onto an infinitesimal small patch on the sensor array located at position x/. Let S(/.) be a vector of the sensor s response function. That is, if we have three different types of sensors, one... 

Ping et al. have fabricated an integrated microsensor array on a silicon wafer for pH imaging [89]. Six different pH-sensitive colorimetric dyes (methyl violet 6B, phenolic red, alizarin complexone, 5-carboxy-fluorescein, alizarin red and methylthymol blue) were used to cover the whole pH range. The dyes were adsorbed on microbeads and placed in etched microwells on the silicon wafer. The indicator array was also used as a cation sensor chip (see Sect. 2.4). 

Figure 4.5 A planar 1.2 cm diameter oxygen-glucose sensor array. The small (125 pm) dots are the oxygen electrodes, the ribbon-like counter electrode is visible, and the Ag reference electrodes can be seen. Four of the oxygen electrodes have circular pockets of glucose oxidase integrated into the overlying membrane.

Tanghe SJ, Wise KD (1992) Iridium Oxide High-Performance Stimulating Sites for Multielectrode Probe Arrays, Center for Integrated Sensors and Circuits, Course of the University of Michigan... 

Recent developments in sensor technology allow to create different integrated and miniaturized sensor arrays. Using microsystemtechnology fluidics can be added creating whole micro-analytical devices on chip. However, there are drawbacks involving inappropriate sensor function in media and production. Using sophisticated sensor construction and microfluidics such drawbacks can be overcome. In this chapter different sensor systems and whole micro-analytical devices are presented with emphasis on their applications. 

Keywords Integrated miniaturized sensor arrays, microfluidics, biosensors, microelectronic, microsystemtechnology. 

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