Major Areas of Opportunity - Implications of Emerging Micro-and Nanotechnologies - page 70

package, most IMUs do not have GPS capability. Micro GPS units, possibly
drawing upon e911 cell phone technologies and MEMS, might play a part in
bringing this capability into IMUs.
Magnetic Field Sensors. Low earth orbit (LEO) spacecraft typically use flux-gate
magnetometers to measure local magnetic field strength and direction for control
of orientation. Flux-gate, magnetoresistive, and Hall-effect sensors are all suit-
able for developing microengineered magnetometers. Honeywell has a three-axis
magnetic sensor hybrid based on magnetoresistive transducers, 117 Nonvolatile
Electronics, Inc., manufactures application-specific magnetic sensors based on
the giant magnetoresistive (GMR) effect, 118 and another magnetometer concept
is being developed at Johns Hopkins University 119 using the Lorentz force to
measure vector magnetic fields.
Sensors for Chemical and Biological Agents
Chemical and biological sensors are of great importance, particularly in light
of recent events. The Army, with much greater concentrations of troops than the
Air Force, has taken a leading role in developing sensors for chemical and bio-
logical detection. Only a brief overview is presented here. A recent NRC report
covered this topic in much more detail. 120
Numerous approaches are being developed to detect chemical and biological
attack on personnel, with nanoscience rapidly being recognized as a major con-
tributor. Miniaturization of electronics and the concomitant ability to measure the
behavior and properties of nanometer-size bits of matter introduce remarkable
advances in sensing and detection. Microfabricated sensors provide a sensitive
measure of nanometer (e.g., molecular) interactions with a high degree of speci-
ficity. These sensors are able to detect minute traces of chemical and biological
agents as well as explosive vapors. Fabrication of sensor arrays and devices by
the usual parallel processing methods, similar to chip fabrication, will mean
inexpensive sensors for a wide variety of substances. MEMS production methods
further expand the horizon of new devices used for these purposes. Such point
sensors will be effective for environmental monitoring, security (buildings, trans-
portation platforms, and points of embarkation), and battlefield protection. The
impact of research in this area on mine detection could also be significant. This
aspect of nanotechnology will probably lead to marketable products in the near
future. 121
The sensitivity of these sensors is due to the nature of the instrumentation
developed to observe small changes at nanometer dimensions. Tools such as
scanning local probes (tunneling microscopy and many related techniques) are
just one of the many tools that may be used for sensing the presence of a specific
molecular species. The fabrication of tools able to measure minuscule changes in
mass, along with changes in optical, electric, and magnetic properties at nanom-