Nanotechnology-Enabled Sensors

66 Chapter 3: Transduction Platforms
substrate and electrode materials are chosen such that they do not interact
with any measurand during the measurements.
The effect of nanostructured sensitive layers in enhancing the performance
of capacitive and conductometric transducers will be presented in
Chaps. 6 and 7 in details.
6 mm
4 mm
Fig. 3.3 Inter-Digital Transducer (IDT). Left: Schematic; Right: SEM image.
3.3 Optical Waveguide based Transducers
Optical waveguide based transducers are among the most utilized
transducers in nanotechnology enabled sensing. Such sensors utilize interactions
of optical waves, generally in the visible, infrared, and ultraviolet
regions, with the measurand. These interactions cause the properties of the
waves to change, e.g. intensity, phase, frequency, polarization etc., and
these changes are then measured.
There are many types of optical sensors which are not based on
waveguide structures; rather they make use of optical spectroscopy for
characterization of target analytes. Such devices are concerned with the
measurement of spectrums, which may include UV-visible and infrared
wavelengths, parameters. These measurements were discussed in Chap. 2
and will be further explained in the Chaps. 5 and 6. In this section, several
optical waveguide based transducers commonly used in sensing will be
presented. These encompass different waveguides with various geometries,
and are categorized into two major types: transducers based on the propa-