Packaging takes on special importance for chemical-sensing applications, as does the need for fundamental studies of flow in small channels and of liquid-solid interface effects. These areas still present challenges, but the barriers are surmountable. Indeed, much work is under way to bring the promise of MEMS to fruition in this area.
In some instances, MEMS have made the transition from research to commercial products, some with very large markets. Until now, however, MEMS have remained mostly in the first phase of product realization, which offers an improvement over what is already on the market. For example, the MEMS accelerometer does not enable the implementation of air-bag safety systems; rather MEMS accelerometers offer cheaper systems and better performance. MEMS technology is now poised to enter a second phase of product realization, which is marked by the creation of entirely new markets. As a fully integrated system, a MEMS can provide products that know where they are, what is occurring around them, and how to affect a particular outcome.
Future MEMS applications will not only allow information gathering and communication at a distance, but they will also sense and control environments remotely at low cost. With this combination of capabilities, MEMS will play a key role in large sectors of the economy, including health care, transportation, defense, space, construction, manufacturing, architecture, and communication systems. A few potential examples of the opportunities for MEMS are described below.
MEMS can improve the performance and reliability of all vehicles, especially automobiles and airplanes. Sensors and accelerometers could potentially be used in the automotive industry, for example, for active suspension systems, engine and emissions control, vibration control, and noise cancellation (see Figure 1-8). In the aerospace industry, MEMS sensors could be used for detecting flow-instability, avoiding stalls, and monitoring structural integrity, as well as for controlling engines and emissions and canceling vibration and noise.
In addition to using MEMS to reduce the high costs associated with diagnostic testing, researchers are investigating using MEMS to sense the condition of the body and actuate implanted reservoirs to release controlled doses of medicines (Figure 1-9). Portable MEMS-based analytical instruments are under development that will enable communication and control with remote locations and permit the exchange of information with remotely located experts.
With microactuated read-write heads and instrumented microminiature head housings, researchers predict a tenfold increase in recorded information density in MEMS-engineered microdisk drives. Disk-drive systems with the storage capacity of the current 3.5 inch systems would shrink to approximately the size of a U.S. quarter dollar. MEMS could also make a major impact on the radio-frequency field through the development of integrated switches, high-Q filters, and other integrated components.
MEMS could substantially improve the performance, safety, and reliability of weapons systems without compromising their shape or weight. The small size of MEMS makes the inclusion of redundant systems feasible, as well as the implementation of fault-tolerant architectures that are modular, rugged, programmable, conventionally interfaced, and relatively insensitive to shock, vibration, and temperature variations. MEMS could also make sophisticated new functions in weapons feasible, such as systems that understand and communicate their condition, enabling the early detection of incipient failure. Other potential functions for MEMS include the detection of tampering.
The continued evolution of MEMS technology reflects the ongoing ability of scientists and engineers to shrink electronic devices while simultaneously increasing their performance. These advances have had remarkable effects on both technology and society at large. For example, commercial successes that have evolved from MEMS technology include the greater than $1 billion ink-jet printer cartridge market, as well as the smaller but still very sizable markets for products using MEMS for pressure sensors and accelerometers. Evidence of continued development of MEMS technology is apparent in their emerging use in high-resolution displays and chemical sensor arrays. These examples, however, demonstrate the first phase of product realization. Longer range opportunities for MEMS application in the second phase of product realization include applications in the transportation, health care, information technology, and defense industries. The descriptions in this chapter illustrate a limited number of areas in which substantial MEMS activity was already under way. A broader, frequently updated picture of the MEMS field can found on World Wide Web sites that focus on MEMS (see Appendix A).