Specifications MEMS sensors

According to the typical work flow for developing MEMS sensors (Fig. 4.1.4), design of the angular-rate sensor system starts from the required specifications, with system-level design, and comprises the steps described in this section. 

A wide variety of solid-state sensors based on hydrogen-specific palladium, metal oxide semiconductor (MOS), CB, electrochemical, and surface acoustic wave (SAW) technology are used in the industry for several years. Microelectromechanical systems (MEMS), and nanotechnology-based devices for the measurement of hydrogen are the recent developments. These developments are mainly driven by the demands of the fuel cell industry. Solid-state approaches are gaining rapid popularity within the industry due to their low cost, low maintenance, replacements, and flexibility of multiple installations with minimal labor. 

Membranes fabricated using the MEMS technology are finding an increasing number of applications in sensors, actuators, and other sophisticated electronic device. However, the new area of application of MEMS is creating new materials demands that traditional silicon cannot fulfill [43]. Polymeric materials, also in this case, are the optimal solution for many applications. Microfabrication of polymeric films with specific transport properties, or micromembranes, already exists, and much work is in progress [44-50]. 

This section describes a methodical procedure that allows reliability issues to be approached efficiently. MEMS reveal specific reliability aspects, which differ considerably from the reliability issues of integrated circuits and macroscopic devices. A classification of typical MEMS-failure modes is given, as well as an overview of lifetime distribution models. The extraction of reliability parameters is a Tack of failures situation using accelerated aging and suitable models. In a case study, the implementation of the methodology is illustrated with a real-fife example of dynamic mechanical stress on a thin membrane in a hot-film mass-airflow sensor. 

Compact chemical sensors can be broadly classified as being based on electronic or optical readout mechanisms [28]. The electronic sensor types would include resistive, capacitive, surface acoustic wave (SAW), electrochemical, and mass (e.g., quartz crystal microbalance (QCM) and microelectromechanical systems (MEMSs)). Chemical specificity of most sensors relies critically on the materials designed either as part of the sensor readout itself (e.g., semiconducting metal oxides, nanoparticle films, or polymers in resistive sensors) or on a chemically sensitive coating (e.g., polymers used in MEMS, QCM, and SAW sensors). This review will focus on the mechanism of sensing in conductivity based chemical sensors that contain a semiconducting thin film of a phthalocyanine or metal phthalocyanine sensing layer. 

Polymer adhesives have found their place in numerous electronics applications. Major uses include eommercial/consumer products computers and military, space, automotive, medical, and wireless communications. Some adhesives may be used aeross several applications while others have been formulated to meet applieation-specific requirements. For example, reworkability is not a consideration for high-production, low-cost consumer products such as cell phones or calculators, but is important for high-value, high-density printed-wiring boards (PWBs) used in military and spaee electronics. Further, thermal stability at high temperatures is required for near-engine electronics in automobiles, aircraft, and for deep-well sensors, but not for office computers. The major applications for polymer adhesives are to attach and electrically insulate or to electrically connect components, devices, connectors, cables, and heat sinks to printed-circuit boards or to thin- or thick-film hybrid microcircuits. In addition, over the last several decades, new uses for adhesives have emerged for optoelectronic (OE) assemblies, microelectromechanical systems (MEMS), and flat-panel displays. 

Shear stress measurement plays an important role for characterization and control of both macro-and microscale flows. There are various existing techniques suitable for either steady state or instantaneous nature of the flow. The rapid development of MEMS manufacturing technology has immensely contributed to improvement in spatial and temporal resolution of shear stress sensors. Therefore, turbulent flow control has become feasible for many practical apphcations. However, the cahbration and implementation issues of shear stress measurements are not completely estabhshed. Therefore, the implementation procedure for shear stress measurement is problem specific and requires complete understanding of the measurement principle. The existing shear stress measurement technologies have not been implemented over a wide range of microscale flow problems. Therefore, future research should concentrate on critical issues relevant to shear stress measurement in various microflow applications. This wfll contribute towards development of matured shear stress measurement techniques. 

In the remainder of this chapter, we will discuss how the unique properties and functions of conjugated polymers can be incorporated into various types of microsystems, starting with sensors. The limitations of current MEMS materials are discussed in the context of specific examples. A more speculative discussion of the possible use of conjugated polymers in entirely new microsystems is considered at the end of the chapter. 

This evaluation section has investigated the benefits of using the built-in features of a recent inertial sensor for one specific, yet typical, sensor node. Measurements included [7] timing information on the SPl communication between sensor and micro controller, [5] the code size required to implement them, [8] detection precision and recall values, and [9] the overall current draw of the entire prototype sensor node. The results gathered in this evaluation can be summarized in two parts. For the off-loading of the buffering and sampling to the MEMS chip, the conclusions of this case study are that it leads to ... 

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