Toward Nanometer-Scale Sensing Systems: Natural and Artificial Noses as Models for Ultra-Small, Ultra-Dense
Sensing Systems
June 2005
Brigitte Rolfe, The MITRE Corporation
ABSTRACT
The development of highly sensitive, selective, reliable, and compact sensing systems to detect toxic
chemical and biological agents is of great importance to national security. This paper examines the best such
naturally occurring sensing system, the sense of smell or "olfaction," as well as artificial sensing systems built to
emulate the nose. The goal is to combine lessons learned from natural and artificial olfaction with opportunities
presented by advances in nanotechnology, in order to further the development of nose-like sensing systems
integrated on the nanometer scale. The olfactory processes are reviewed here in some detail. Dense arrays of
olfactory neurons, acting as ultra-small, non-specific sensors, use molecular recognition to perform highly
parallel molecular sensing. The sensory signals so generated are identified by the brain using a spatio-temporal
coding scheme. In this way the olfactory system recognizes, with great accuracy and sensitivity, a broad range
of chemical stimuli. The principles of olfaction have been applied to developing artificial noses that are
composed of arrays of cross-reactive gas sensors of various types. Artificial noses based upon conductivitychange
devices, mass-change devices, and fluorescent optical fibers are reviewed here. The smallest artificial
noses at this time are devices that incorporate micron-scale sensing elements and are comparable in size to a
credit card. To more closely approximate the capabilities and compact size of the natural nose, it will be
necessary to shrink the individual sensor size even farther, integrating nanometer-scale sensors into systems.
Individual nanometer-scale devices, such as carbon nanotubes and nanowires, already have been demonstrated to
function as gas sensors, and their applicability to nose-like sensing is discussed. At this point in time, however,
no complete, nose-like nanometer-scale sensing system has been developed. This paper concludes by presenting
for consideration a proposal for an electronic nose composed of nanowire sensors.
Additional Search Keywords
N/A
|
