Sensors devices

The accept and downgrade buttons are interlocked with a sensor device, so that a block must be scanned at least once before the block can be accepted and loaded out by the operator This function will however always be overruled by the programmed safety time limit, which will automatically reject and outload the block when the allowed exposure time has elapsed. 

The resulting films are usually hard and scratch-resistant but often show considerable stress (152). Such films can be used as corrosion-resistant coatings on metals or as membranes in gas sensor devices (153,154)... 

A new chemical sensor based on surface transverse device has been developed (99) (see Sensors). It resembles a surface acoustic wave sensor with the addition of a metal grating between the tranducer and a different crystal orientation. This sensor operates at 250 mH2 and is ideally suited to measurements of surface-attached mass under fluid immersion. By immohi1i2ing atra2ine to the surface of the sensor device, the detection of atra2ine in the range of 0.06 ppb to 10 ppm was demonstrated. 

These lead-based materials (PZT, PLZT, PMN) form a class of ceramics with either important dielectric, relaxor, pie2oelectric, or electrooptic properties, and are thus used for appHcations ia actuator and sensor devices. Resistive properties of these materials ia film form mirror the conduction processes ia the bulk material. Common problems associated with their use are low dielectric breakdown, iacreased aging, and electrode iajection, decreasiag the resistivity and degrading the properties. 

Nowadays all over the world considerable attention is focused on development of chemical sensors for the detection of various organic compounds in solutions and gas phase. One of the possible sensor types for organic compounds in solutions detection is optochemotronic sensor - device of liquid-phase optoelectronics that utilize effect of electrogenerated chemiluminescence. In order to enhance selectivity and broaden the range of detected substances the modification of working electrode of optochemotronic cell with organic films is used. Composition and deposition technique of modifying films considerably influence on electrochemical and physical processes in the sensor. 

For example, Novasina S.A. (www.novasina.com), a Swiss company specializing in the manufacture of devices to measure humidity in air, has developed a new sensor based on the non-synthetic application of an ionic liquid. The new concept makes simple use of the close correlation between the water uptake of an ionic liquid and its conductivity increase. In comparison with existing sensors based on polymer membranes, the new type of ionic liquid sensor shows significantly faster response times (up to a factor of 2.5) and less sensitivity to cross contamination (with alcohols, for example). Each sensor device contains about 50 pi of ionic liquid, and the new sensor system became available as a commercial product in 2002. Figure 9-1 shows a picture of the sensor device containing the ionic liquid, and Figure 9-2 displays the whole humidity analyzer as commercialized by Novasina S.A.. 

Figure 9-1 Sensor device for measurement of relative humidity, containing an ionic liquid as...

A. Mandelis, and C. Christofides, Solid State Gas Sensor Devices, in Chemical Analysis, John Wiley Sons, New York (1993). 

Vol. 125. Physics and Chemistry of Solid State Sensor Devices. By... 

Statistical Methods in Analytical Chemistry. By Peter C. Meier and Richard Zud Laser Ionization Mass Analysis. Edited by Akos Vertes, Renaat Gijbels, and Fred Adams Physics and Chemistry of Solid State Sensor Devices. By Andreas Mandelis and Constantinos Christofides... 

Recent advances in instrumentation range from novel (laser) sources and highly compact spectrometers over waveguide technology to sensitive detectors and detector arrays. This, in combination with the progress in electronics, computer technology and chemometrics, makes it possible to realise compact, robust vibrational spectroscopic sensor devices that are capable of reliable real-world operation. A point that also has to be taken into account, at least when aiming at commercialisation, is the price. Vibrational spectroscopic systems are usually more expensive than most other transducers. Hence, it depends very much on the application whether it makes sense to implement IR or Raman sensors or if less powerful but cheaper alternatives could be used. 

In the previous section first results with promising nanophotonic sensor devices have been demonstrated. It is still some work needed before low-cost, high sensitive and complex optical sensors with a large number of optical functions will be available. For the increase in sensitivity and... 

The introduction of 2-[4-(dimethylamino)phenylazo]benzoic acid into a silica sol allows the preparation of pH-sensitive doped coatings upon glass substrates. The behavior of this system was evaluated as the function of pH changes in liquid and gas media68. Optical absorption and sensitivity against pH were monitored by Vis spectroscopy. Chemical and mechanical stability tests carried out with coatings demonstrated that they were resistant enough to be use in sensor devices for pH measurements in laboratories. 

Biomaterials are inert substances that are used in contact with living tissue, resulting in an interface between living and non-living substances [45,46], Biocompatibility of this interface is achieved by using such biomaterials for encapsulation in the construction of sensor devices. 

The interaction in an interface of device/tissue is limited by two factors. There is the corrosive environment, such as biological fluid, which contains salts and proteins among other cellular structures in which the sensor device must survive [47, 48], Second, there is the encapsulation material which may induce a toxic reaction due to poor biocompatibility and hemocompatibility [49, 50], It is crucial to use a biomaterial that can overcome both limiting factors to maintain the lifetime of the sensor device and protect the body [51, 52],... 

Some earlier developments and applications of various implantable pH sensors or measurement systems have been reported [128, 129, 130, 131]. However, reliable pH sensors for long-term implantations are still not available, and widespread clinical usage of implantable pH sensors has not been reached. Similar to other implantable sensors, the development of implantable pH microelectrodes, either fully implanted in the body or needle type sensors applied through the skin (percutaneous), has faced serious obstacles including sensor stability deterioration, corrosion, and adverse body reactions [48, 132, 133], Among them, encapsulation to prevent corrosion represents a major challenge for the implantable sensor devices [51]. Failure of encapsulation can cause corrosion damage on internal components, substrate materials, and electrical contacts [48], The dissolution of very thin pH sensitive layers will also limit the stability and lifetime of implantable micro pH sensors. 

In practice, some anticoagulation agents such as heparin or antiplatelet agents, e.g. nitric oxide (NO) are delivered to sensor sites in order to reduce the risk of thrombus formation. Nitric oxide (NO), which is a potent inhibitor of platelet adhesion and activation as well as a promoter of wound healing in tissue, has been incorporated in various polymer metrics including PVC (poly(vinyl-chloride)), PDMS (poly-dimethyl-siloxane) and PU (poly-urethanes). Those NO release polymers have been tested in animals as outer protection coatings and have shown promising effects for the analytical response characteristics of the sensor devices [137],... 

Hoefer, U. Bottner, H. Wagner, E. Kohl, C.-D. Highly Sensitive N02 Sensor Device Featuring a JFET-like Transducer Mechanism. Sensors and Actuators B 47 (1-3) (1998), p. 212-216. 

Recent developments towards modularisation of processing and device technology now allow for a cost efficient customisation of sensor devices for white goods appliances. 

We have shown that antiresonant dielectric layers can be used to design low-loss liquid-core waveguides that are suitable for implementing planar sensor device geometries. The following sections will describe in more detail how the design principles laid out here were implemented in silicon-based LC-ARROW chips and used for optical sensing and detection of a wide variety of substances. 

Fiber Optic Sensor Devices for Temperature Measurement... 

Applications. We have shown here that bulk quantity SiNW can be made in the form of thin films. These films can be used as (1) templates for making other nanostructures because of the large surface area offered by those nanowires (2) PL devices and (3) nanoelectronic and chemical sensor devices or fuel cells because the silicon oxide nanowires may be passivated before they are oxidized. We are pursuing all these options in our lab. 

In order to allow for a complete analysis of the sensor device, the feedback provided by the temperature sensor on the membrane has to be included as well. The voltage across the temperature sensor resistor can be determined as ... 

CNTs also have promising applications in the immunosensing field and many examples of such sensor devices can be found in the literature. For example, immunosensors with an electrochemiluminescence readout signal have been designed using CNTs as support of the immunorecognition systems [167]. 

The selectivity inherent to TNT detection by amplified fluorescent polymers, as described in Section 4, helps to rriinirriize false-positives in land mine detection. These sensor devices respond only to nitroaromatics and similarly small, electron-deficient analytes, which are found typically only in or close to explosives and explosive devices. Field-tests to date have demonstrated that these devices are at least as reliable as trained dogs in detecting explosives that contain nitroaromatics. There is still uncertainty concerning what chemical that dogs actually detect when searching for explosives [17]. This... 

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