Sensors Structure

Fig. 6.22. Folate-FRET sensor structure and its application to measure disulfide bond reduction in endosomes. The molecule contains the folate moiety which is recognized by the folate receptor situated at the plasma membrane. This recognition leads to endocytosis and after some time to cleavage of the probe. 

Wolfbeis O.S., Reisfeld R., Oehme I., Sol-gels and chemical sensors, Structure and Bonding 1996 85 51-98. 

The RI sensitivity, SKr, of the above sensor structure is given in Fig. 6.7. Whereas the sensitivity for the first-order mode increases monotonically with the increased wall thickness, the sensitivity for the second and third order modes oscillates significantly. In particular,, S Rr becomes nearly zero at certain regions that... 

A more detailed description of the working principle of the multichannel YI is given for a four-channel device (N = A). The distances between the channels have been chosen such that di2 k d23 i=- d34 / di3 =/= d24 / dl4. There are six possible different channel pairs corresponding to six different distances of dx2 = 60 pm, d23 = 80 pm, d34 = 100 pm, d13 = 140 pm, d24 = 180 pm, and d14 = 240 pm. These distances match the realized YI sensor structure described in Sect. 10.3. The final interference pattern will thus be a superposition of six two-channel interference patterns. The calculated interference pattern for the four-channel YI is shown in Fig. 10.6a. The amplitude spectrum (lower graph) and the phase spectrum (upper graph) of the Fourier-transformed interference pattern are presented in Fig. 10.6b. 

While this book surveys a diversified range of photonic sensor structures, it is certainly impossible in one book volume to provide full coverage of all such structures known to science. Thus plasmonic photonic structures, photonic crystal fibers, and nanoparticles will be covered by other upcoming books in this Springer Series Integrated Analytical Systems. ... 

Nickel AML, Seker E, Ziemer BP, Ellis AB. Imprinted poly (acrylic acid) films on cadmium selenide. A composite sensor structure that couples selective amine binding with semiconductor substrate photoluminescence. Chem Mater 2001 13 1391-1397. 

A phenomenological model based on fundamental representations of the sensor structure and intrinsic processes has been proposed to explain the mechanism of signal formation [30, 31]. 

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. 

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... 

For a sensor with good electrodes (high Jg), the response time is determined by the characteristics of the diffusion barrier and the sensor structure. For the sensor of Fig.6b, for example, a simple rate equation analysis for Pv, the oxygen pressure inside v, predicts that for a cylindrical aperture... 

Non-Diffusion-Limited Sensor Structures. In this section, we will discuss a number of devices which do not require for their operation the existence of a barrier to the diffusion of oxygen. 

Sensing chemical species is a much more difficult task than the measurement of mechanical variables such as pressure, temperature, and flow, because in addition to requirements of accuracy, stability, and sensitivity, there is the requirement of specificity. In the search for chemically-specific interactions that an serve as the basis for a chemical sensor, investigators should be aware of a variety of possible sensor structures and transduction principles. This paper adresses one such structure, the charge-flow transistor, and its associated transductive principle, measurement of electrical surface impedance. The basic device and measurement are explained, and are then illustrated with data from moisture sensors based on thin films of hydrated aluminum oxide. Application of the technique to other sensing problems is discussed. 

A chemical species in the environment of a C-I-S capacitor sensor structure can interact with the device and thereby modify its double layer in the same four ways it can interact with the double layer of a C-S or C-I-S diode sensor. These four mechanisms need to... 

The first question to ask when comparing various diode and capacitor sensor structures is how do their sensitivities compare. This question is answered for several hydrogen sensing structures in Table V. 

Table V. Comparison of the Barrier Height or Flatband Voltage Change for Different Sensor Structures...

Modification of the sensor structure. The above amperometric sensor has a rather complicated construction, because the sample gas (H2 + air) is separated from the reference air. So, we tried to simplify the sensor structure as shown in Figure 9. As proton conductor we used a thin antimonic acid membrane (mixed with Teflon powder) of 0.2 mm thickness. This membrane is thin and porous enough to allow a part of the sample gas to permeate. On the other hand, the counter Pt electrode was covered with Teflon and Epoxy resin in order to avoid a direct contact with the sample gas. 

Figure 1.1 Multilayer sensor structure showing control of oxygen, glucose, and electroactive interferences.

The multilayer sensor structure consists of cermet and polymer based layers sequentially deposited on a 96% alumina ceramic substrate using a thick film screen printing process. The cermet layers are of ceramic-metal composition which require firing at a temperature of 850°C and the polymer layers are cured at temperatures below 100°C. Layout of this multilayer sensor structure is shown in Figure 1. 

Hamano et al. (1982) have fabricated an a-Si H photodiode array linear image sensor. The sensor structure is shown in Fig. 5. The sensor is constructed by first forming individual electrodes on a glass or a ceramic substrate. Then l-/mi-thick undoped a-Si H is produced at 230°C by glow-discharge decomposition of silane and finally 1500-A-thick ITO common electrode, which also acts as an antireflection coating, is deposited by dc sputtering. 

Microfabrication has emerged from microelectronics manufacturing and is using its proven processes and process sequences. Additionally, specific methods have been developed to fabricate mechanical, electrical, optical, or sensor structures, which are characteristics of microfabrication. In order to stay within the scope of this book, only top-down methods, that is, the manufacture of smaller structures with higher functionality from larger structures by the use of subtractive methods, will be discussed. Bottom-up methods, which create larger structures by ordered arrangement of small units (molecules, nanoparticles), are still in their infancy and mainly employed for biosensors. 

FIGURE 14.7 The roughness of the EPI-poly layer can be planarized by using CMP. After removal of the sacrificial oxide layer by vapor phase etching, the sensor structures are released. 

The CMP task is a so-called blind polish process that is, the process has to be terminated at a given thickness. In our case, it is assumed that the EPI-poly thickness is repeatable from wafer to wafer. The polishing time is determined with control wafers and preset. Every wafer of a production batch is measured after CMP. If the thickness results run out of spec, the polishing time has to be adjusted for the following wafer (closed-loop control). By combining uniformity profiles of EPI-poly deposition and poly-Si CMP, sensor structures with a final thickness of 11.0 pm and an absolute thickness distribution of 80nm (Icr) are obtainable. The optimized CMP process itself shows a nonuniformity of <2% on 150-mm wafers. 

M. Mosbach, H. Zimmermann, T. Laurell, J. Nilsson, E. Csoregi and W. Schuhmann, Picodroplet-deposition of enzymes on functionalized self-assembled monolayers as a basis for miniaturized multi-sensor structures. Biosens. Bioelectron., 16 (2001) 827-837. 

The present focus is on the gas-liquid flow riser. The model used is a complex nonlinear infinite-dimensional system accounting for momentum, mass and energy balances [3], and the measurements available include temperature and pressure at different locations along the riser. Since the problem being tackled is of distributed parameter nature, location where such measurements are taken, along with its type, is crucial for estimator performance. Moving horizon estimation (MHE) is well suited as it facilitates the sensor structure selection (both in a dynamic and static sense). MHE is proven to outperform... 

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