Usually refractories are divided into three categories acidic, basic and neutral. Although in many cases it is difficult to make sharp distinction.
Many micro electro mechanical systems (MEMS) devices are now on the market. They are available for use as components in diverse systems with many applications. Some MEMS devices are used primarily for their planned employment.
Systems of micromirrors for transmitting and displaying information are examples. Other MEMS components are finding opportunistic applications in the hands of creative system engineers. Pressure sensors and accelerometers are prime examples.
Many micro electro-mechanical systems (MEMS) devices are now on the market. They are available for use as components in diverse systems with many applications. Some MEMS devices are used primarily for their planned employment.
Systems of micro mirrors for transmitting and displaying information are examples. Other MEMS components are finding opportunistic applications in the hands of creative system engineers. Pressure sensors and accelerometers are prime examples.
MEMS are already important devices in several major industries. Both the variety of available mechanical micro-devices and their applications will grow rapidly in the foreseeable future.
The reliability of MEMS is considered from the viewpoint of their performance in actual applications. The applications of micro machined static MEMS, micro-mechanical MEMS sensors and actuators, and functional MEMS systems are also surveyed. Examples of MEMS use in the transportation, communication, analytical, and medical industries are provided.
Micro electro mechanical systems are devices that have static or moveable components with some dimensions on the scale of a micrometer to nanometer. For comparison, a human hair is about 80 micrometers in diameter. MEMS combine microelectronics and micromechanics and sometimes micro-optics and micro magnetics. A decade ago, hundreds of MEMS components were prototyped and dozens were commercially available.
Many people then viewed the technology as the classical‘‘solution looking for a problem to solve.’’ The situation changed markedly during the 1990s when the market for MEMS took off in a manner reminiscent of the sales growth of integrated circuits in the 1960s. At present, roughly 100 million MEMS components are being sold annually. Patents on MEMS are being granted at the global rate of about one per workday or 200 annually. While MEMS devices will not be used as commonly as integrated circuits, they will be found in a great diversity of products and installations. Just as most people in technological societies own products with integrated circuits and microlasers, pervasive ownership and use of
MEMS are clearly in prospect. It is estimated that there are 1.6 MEMS devices per person in the United States. Micro-mechanical devices will both improve the performance of existing systems and enable entirely new applications.
Dozens of companies make and sell MEMS. Now that MEMS devices are available in a greater variety and in large numbers, it is possible for the applications engineer to incorporate them in many different products. Most products are the systems for which particular MEMS were designed, but others are targets of opportunity. That is, the MEMS components are simply devices that are available for incorporation into whatever systems can use them.
It is striking that the compilations vary so widely in their absolute value and in their rate of growth. The variance in values is due to differences in what is included in the study: for example, are micromachined ink jet print heads counted as MEMS or not? Some studies also include products enabled by the availability of MEMS devices. However, all the studies indicate that the production of MEMS is already a multibillion dollar industry that doubles every 2 to 4 years. The associated growth rates of 17 to 35% are noteworthy.
Applications of MEMS
The first micro mechanical device made by modern manufacturing techniques was demonstrated in the mid-1960s. Significant commercial production of MEMS started in the 1980s, and some of the uses are
- Pressure sensors for automotive
- Medical applications.
- Air bag triggers in cars.
- Volume production of microfluidic devices
Latest Innovations in MEMS
Optical MEMS for displays are the latest inventions of this system and came to market a few years ago, and micromirrors for switching signals in fiber networks are poised to enter the volume production stage. MEMS switches for control of radio-frequency signals and microwave signals is the next predictable market for MEMS devices. Devices for dense data storage and many new medical applications are also in prospect.
The integration of microelectronics and micromechanics is a historic advance in the technology of small-scale systems an is very challenging for designers and producers of MEMS.
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