Detectors MEMS-based

Figure 6.6 Example components available for simple photometers (A) a dual channel detector, (B) a quad, four-channel detector, (C) an example filter wheel with 8-filter channels, and (D) example MEMS-based IR...

Figure 6.8 Example of a MEMs based IR. spectral detector component dimensions and example output (120 channel output for BEX).

There is a constant move toward the improvement of instrumentation technology. This ranges from new detector and source technologies, to new ways to make IR measurements and new ways to fabricate instruments. In the area of components, there are new MEMS-based sources, which operate at low power and provide extended source lifetimes, new tunable laser devices, new tunable filter devices, both broad and narrow range, and new detector arrays. Many of these devices are currently relatively high cost. However, most are made from scalable technologies, such as semiconductor fabrication technologies, and as such if the demand increases the cost can come down. Many can follow Moore s law of... 

Traditionally, the TCD has been recognized as a universal detector, but one of limited sensitivity. Several manufacturers have invested in miniaturization of the TCD, with improvements in sensitivity, resulting in lower detection limits. For example, Varian sells a multichannel GC (CP-4900 Micro GC) incorporating a MEMS-based TCD with the unrivaled sensitivity of about one ppm. 

Fig. 13.17 Working principle of the MEMS-based FDNMR spectrometer. The sample (S) sits within an RE excitation coU (C), which modulates the NMR signal at the mechanical resonance frequency of a resonator made up of the detector magnet (D) and sihcon beam (O). The detector magnet sits within an annular magnet (R) and the entire assembly is within the pole piece of an external field magnet (M). Detector magnet motion is measured using a fiber optic interferometer (F)...

An example of one of TSA/TSL s R D funded MEMS based project is the Sandia National Laboratories (SNL) MicroHound project. This is based on the SNL Micro Chem Lab on a Chip , illustrated in Figure 1. The original prototype system from SNL was developed for high vapour pressure, chemical weapons (CW) detection, which utilized a MEMS GC separator, with miniature surface acoustic wave (SAW s) based sensors. The system included an inlet, coated pre-concentrators, detectors, and pumps. To make this useful for trace explosives detection, the addition of an alternate front-end sample collection/macro-preconcentrator and MEMS based coated-preconcentrator is necessary, along with the option to utilize or exclude the MEMS GC separator followed by detection by either, or both, SAW s and miniaturized IMS detectors. 

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]. 

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