Integrated silicon-based sensors

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... 

A third application for pTAS is in the biomedical field. Gumbrecht et al. [46, 47] developed a monolithically integrated, ISFET-based sensor system for (bedside) monitoring of blood pH, p02 and pC02 in patients. Here the successful introduction on the market mainly depends on the price of the system, for which reason a CMOS-compatible design of the silicon part is needed. Evidently, such a development is only possible in the case of a high volume market. 

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. 

Micro flow control devices open new possibilities for the miniaturization of conventional chemical and biochemical analysis systems. The micro total analysis system (pTAS) including microfabricated detectors (e.g. silicon based chemical sensors, optical sensors), micro flow control devices and control/detec-tion circuits is a practical micro electro mechanical system (MEMS). pTAS realize very small necessary sample volume, fast response and the reduction of reagents which is very useful in chemical and medical analysis. Two approaches of monolithic and hybrid integration of these devices have been studied. Monolithic and hybrid types of flow injection analysis (FIA) systems were already demonstrated [4, 5]. The combination of the partly integrated components and discrete components is useful in many cases [6]. To fabricate such systems, bonding and assembling methods play very important roles [7]. 

Lilhe JJ, Thomas MA, Denis KA, Jokerst NM, Henderson C, Ralph SE (2004) Modal pattern analysis and experimentatal investigation of multimode interferometric sensing a path to fully integrated silicon-CMOS-based chem./bio sensors. Proc Lasers and Electro-Optics Society Annual Meeting -LEOS, pp 352-353... 

Figure 1 illustrates the operational principle of hydrogel-based sensors. Pressure sensor chips with a flexible thin silicon bending plate and with an integrated piezoresistive Wheatstone bridge inside this plate have been employed as... 

In principle, the choice of materials used to develop both the electrodes and the insulator of an OFET-based sensor should be basically the same as for OFETs developed for other applications. Similarly, the design of the device should follow the same rules. However, there are some unique aspects that are intrinsic to sensors and deserve special attention. For instance, the sensing area of the device this is the area where the external stimulus (chemical or physical) must be applied to the device without affecting its integrity and/or robustness. The first example of an ISOFET reported in the literature [13] was fabricated on silicon and the only organic component of it was the semiconductor employed as the active layer. In order to develop this structure, it is necessary to etch the highly doped silicon from the back side of the device... 

The principle discussed above has been used to develop an electronically adjustable miao chemostat valve allowing feedback control to keep constant concentration of certain species in solution. " The chemostat consists of silicon-based upper and bottom plates as well as a circuit card for the elertric connection to the PC-controlled power supply. The upper plate carries a platinum temperature sensor and contains a hydrogel chamber ((600 x 600 x SSOjpm ), which is covered by a perforated membrane. The bottom plate has similar con-stmction with an integrated platinrrm heating element (Figure 36(a)). ... 

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