Sensor Used in E-nose - The Electronic Nose Artificial Olfaction Technology - page 172

with integrated front-end electronics. Hence, new low temperature fabrication
technologies like printed electronics or system on foil electronics are deeply
investigated for the development of new materials and manufacturing processes
compatible with flexible polymeric substrates [ 22 ].
Advances in the fabrication of metal and metal nanoparticles have deferred
nanostructured materials with unique properties, which can be potentially applied
to the E-nose sensor. Remarkable physical and chemical properties of metal and
semiconductor nanoparticles also provide them as promising materials in the fields
vary from optoelectronics sensor to medicine sensor.
Zampetti et al. [ 23 ] show the design, fabrication, and test of a fully flexible
sensorial system (SS), composed of three dissimilar sensor units (SU), integrated
on an ultrathin polyimide substrate (PI) of 8 mm thick. Each SU consists of a
capacitive sensor connected to a ring oscillator (RO) used as readout circuit. In
each unit, they utilized a different chemical interactive material (CIM) as dielectric
polymer: poly(tetrafluoroethene) (PTFE), poly(methyl 2-methylpropenoate)
(PMMA) and benzocyclobutene(BCB). These materials can be easily handled
since they are commonly used in microelectronic process as passivation layer or
photo-resist. These characteristics make possible a large scale production.
Similarly Kinkeldei et al. [ 24 ] works with the chemiresistors type E-nose sensor
and demonstrated a method to integrate an E-nose system into a textile band to
fabricate a smart textile. The demonstrated sensor system consists of four different
polymer composite gas sensors on a flexible polymer foil. With this E-nose inside
a textile, it could differentiate between the exposures of four solvents using the
solubility parameter concept.
Giménez et al. [ 25 ] introduce PAMPA III E-nose, which is an equipment
operating with a measurement system based on a set of 12 semi-conductive
Metallic Oxide Gas Sensors. Thin film Micro-Electro-Mechanical Systems
(MEMS) type sensors are built by evaporation deposition of thin semiconductors
(SnO 2 , ZnO, or WO 3 , among others) films, which must be heated locally in a
temperature range from 300 to 450 C to detect the different gaseous species.
Metallic oxide semiconductors are usually doped with different elements (Al, In,
Pd, Au, Sb, etc.) to increase sensor selectivity.
Development of chemical sensors (electrochemical biosensors) consisting of
CP nanocomposite materials produced by the electropolymerization of CPs on to
specialized nanoparticle electrodes.
ST&D developed the microplasma-based E-nose (MPEN) which is an inno-
vative approach within the area of gas sensing devices and provides a very flexible
device,

which can detect almost any chemical without prior knowledge or

calibration.
Spinelli et al. [ 26 ] evaluated the use of a near infrared (NIR) instrument in
combination with an E-nose system for the early detection of fire blight (disease) in
pears. The E-nose system detected the disease prior to symptom development by
the distinctive olfactory signature of volatiles released as early as 6 days after
infection.