Page 78 - Microsensors, MEMS and Smart Devices - Gardner Varadhan and Awadelkarim

REFERENCES 59

polymers and the single-crystallinity in these polymers is only partial. The develop-
ment of single-crystallinity is important because of its effects on mechanical, thermal,
and optical properties. The single-crystallinity in polymers is achieved by forming long
molecules such as chains of many thousands of carbon atoms by chemical reaction. On
cooling from liquid, these molecules bend back and forth to form individual crystals.
The application of these materials is discussed in various chapters in this book (for a
review on the use of polymers for electronics and optoelectronics, see Chilton and Goosey
(1995)).
The last type of MEMS material is a composite material, which is a combination of two
or more materials from the other four categories. Most composites consist of a selected
filler or reinforcing material and a compatible resin binder to obtain the desired material
characteristics. Usually, the component materials of a composite do not dissolve in one
another and are physically identifiable by an interface between the components.
Ceramic, polymer, and composite materials are important because they are often used as
passive materials in microsensors and MEMS devices. In other words, they are used either
to provide inert substrates or to form inert structures (e.g. shuttles) in micromechanical
devices. These materials are also used as active materials in microsensors and MEMS
devices; sometimes they are referred to as smart materials (Culshaw (1996)). An example
is the use of an electroactive polymer, such as polypyrrole, to make chemoresistive sensors
in an electronic nose (Gardner and Bartlett (1999)). Further details on such smart devices
are given in Chapter 15.

REFERENCES

Chilton, J. A. and Goosey, M. T., eds. (1995). Special Polymers for Electronics and Optoelec-
tronics, Chapman and Hall, London, p. 351.
Culshaw, B. (1996). Smart Structures and Materials, Artech House, Boston, p. 209.
Gardner, J. W. and Bartlett, P. N. (1999). Electronic Noses: Principles and Applications, Oxford
University Press, Oxford, p. 245.
Moseley, P. T. and Crocker, A. J. (1996). Sensor Materials, Institute of Physics Publishing, Bristol,
p. 227.
Pierret, R. F. (1988). Semiconductor Fundamentals, Addison-Wesley, Reading, Massachusetts,
p. 146.
Tuck, B. and Christopoulos, C. (1986). Physical Electronics, Edward Arnold, London, p. 114.