Silicone-based sensors

FIGURE 6-21 A silicon-based sensor array for monitoring various blood electrolytes, gases, and metabolites. (Courtesy of i-STAT Co.)... 

Silicon-based sensors can be classified as physical, chemical or biological, depending on the parameter to be measured. 

As just pointed out, the development of integrated silicon based sensors structures is far and away the most advanced aspect of microfabricated chemical sensor research and development. It is now possible to visualize complex analytical chemistries being performed... 

P. Gavazzo, S. Paddeu, M. Sartore and C. Nicolini, Study of the relationship between extracellular acidification and cell viability by a silicon-based sensor, Sens. Actuators B Chem., 19(1-3) (1994) 368-372. 

The cost pressure on all automotive components is high. As a result, low-cost, high-volume manufacturing processes are a necessary prerequisite for successfully introducing a sensor into vehicles. This is the reason why certain technologies, such as silicon-based sensors and microsystems, have been particularly successful recently (see Section 2.3). 

Fig. 2.1 Market evolution of automotive sensors. Silicon-based sensors are capturing an increasing fraction of the sensor market (adapted from 5])...

Quality. Semiconductor processing techniques enable integration and thus a reduction in the numbers of elements and interconnections, resulting in improved quality. Furthermore, proven batch processes for quality assurance and testing of silicon-based sensors have been adopted from processes for integrated circuits. 

In addition to the thin films discussed above, several additional materials are used in silicon-based sensors for automotive applications. These include metals as well as other, more exotic, materials. 

Silicone-based sensors, which are based on the principle of spreading resistance analysis of semiconductors. 

Baratto C, Comini E, Fagba G, Sberveglieri G, Di Francia G, De Filippo F, La Ferrara V, Quercia L, Lancellotti L (2000) Gas detection with a porous silicon based sensor. Sens Actuator B 65 257-259... 

However, at the same time silicon is a chemically active material and, due to oxidation and interaction with surrounding atmosphere, especially at higher tanperatures, has unstable surface properties. The operation temperature of silicon-based devices is also limited due to the small band gap of silicon. This means that silicon-based devices have strong limitations for operation at high tanperatures and in corrosive atmospheres. Unfortunately, conventional gas sensors mainly operate in such conditions. As a result, silicon-based sensors are absent from the gas sensor market. 

J M Libby and G W Wada, Detection of Neisseria Meningitidis and Yersinia Pestis with a Novel Silicon Based Sensor, J Clin Micro, 27 (1989) 1456-1459... 

Since the 1980s, silicon-based sensors and microelectromechanical devices (MEMS) have been used ex vivo for tasks such as pressure sensing, blood chemistry analysis, flow cytometry and electrophoresis [6]. The term BioMEMS was subsequently coined to describe the wide array of tools developed using silicon as a platform. Extremely sophisticated systems are now available, such as functionalized microcantilevers for molecule adsorption, recognition and quantification, as... 

In spite of the prominence of molecular oxygen luminescence sensing due to its manifold applications, several other chemical species may also be monitored with silicone-based sensors using a pluraHty of indicator-based and label-free mechanisms. A representative account of these chemical optosensors is outHned here to allow the reader to realize how versatile sihcones are for manufacturing such devices, including those for non-gaseous species. 

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