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toys, automotive safety and control, and industrial control. However, in order to realize the advantages
of integrated sensors, a number of technical barriers must be overcome. Two important barriers are (1)
high R&D costs of integrated sensors and (2) reliable and robust packaging of sensors.
The development of microintegrated sensors involves high development costs and long time-to-
market. The surface micromachined accelerometer developed by analog devices costs tens of millions of
dollars and took more than 5 years to produce. Why do integrated sensors cost so much to build? Sensors
are developed using a group-up approach. The development cycle of a sensor begins at the level of physical
principles. The cost of sensor development includes expertise for material selection, design generation,
prototype process development, and characterization.
Such a development cost and speed is not tolerable in applications where only a small amount of
custom sensors is required. Standard sensing modules, low-cost, flexible foundry fabrication processes,
and advanced computer simulation and prototyping tools are required to advance the state-of-the-art
of microintegrated sensors.
Future sensors will involve more non-silicon materials. For example, polymer materials can be used
to reduce the costs while high-temperature materials maybe used for high-temperature sensing applica-
tions (e.g., monitoring of conditions in engines).
Conclusions

A brief historical overview of the development of microfabrication technology and microintegrated
sensors is presented. Common sensing principles, including capacitive, piezoresistive, and piezoelectric
sensing, are discussed. Four important case studies of sensors are undertaken. For each type of sensor
applications—pressure sensors, acceleration sensors, tactile sensors, and flow sensors—the sensor archi-
tectures and fabrication processes are reviewed. Interested readers may find more in-depth information
in the references provided in this section.

References

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4. Siewell, G.L., Boucher, W.R., and McClelland, P.H., “The ThinkJet orifice plate: a part with many
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9. WWW site http://mems.isi.edu.
10 Yun, W., Howe, R.T., and Gray, P.R., “Surface micromachined, digitally force-balanced accelerometer
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11. Jiang, F., Tai, Y.C., Ho, C.M., Karan, R., and Garstenauer, M., “Theoretical and experimental studies
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12. Ebefors, T., Kalvesten, E., and Stemme, G., “Three dimensional silicon triple-hot-wire anomometer
based on polyimide joints,” Proceedings of the 11th International Workshop on MEMS, pp. 93–98,
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