1. Nano-fiber diameters as liquid concentration sensors
Radhi M. Chyad, Mohd Zubir Mat Jafri, and Kamarulazizi Ibrahim
Citation: AIP Conf. Proc. 1528, 461 (2013); doi: 10.1063/1.4803645
View online: http://dx.doi.org/10.1063/1.4803645
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2. Nano-fiber Diameters as Liquid Concentration Sensors
Radhi M. Chyad, Mohd Zubir Mat Jafri and Kamarulazizi Ibrahim
School of Physics, Universiti Sains Malaysia, 11800Penang, Malaysia
Abstract: Manufacturing technologies of nano-fiber sensors offer a number of approved properties of optical fiber
sensors utilized in various sensory applications. The nano-fiber sensor is utilized to sense the difference in the
concentration of D-glucose in double-distilled deionized water and to measure the refractive index (RI) of a sugar
solution. Our proposed method exhibited satisfactory capability based on bimolecular interactions in the biological
system. The response of the nano-fiber sensors indicates a different kind of interaction among various groups of AAs.
These results can be interpreted in terms of solute–solute and solute–solvent interactions and the structure making or
breaking ability of solutes in the given solution. This study utilized spectra photonics to measure the transmission of light
through different concentrations of sugar solution, employing cell cumber and nano-optical fibers as sensors.
Keywords: Concentration sensors, RI sensors, nano-fiber optic, fiber optic sensors, chemical sensors, biosensors
PACS: 42.81.Pa
INTRODUCTION
Documentation of the concentration index of liquids is highly significant in biological and chemical systems.
Numerous recent studies focused on advancements in fiber optic chemical sensors and biosensors [1]. Such sensors
have numerous benefits compared with other types of sensors. The benefits include small size, immunity to
electromagnetic and radio frequency interference, remote sensing, multiplicity of information from a large number
of sensors into a single fiber, and in certain cases, low cost [2]. The development of sensing devices that allow quick
and credible checking of sugar or sugar-level in solutions is very significant in food, juice, and other industrial
liquids. The low-cost, real-time, and easy-to-handle measurement system is required in the electronic tasting tongue
system for food and juice as well as other manufactured products [3]. Optical fiber concentration sensors (OFCS)
and the optical refractometer are practical, modest, and inexpensive methods to measure the refractive index and
concentration of liquids [4]. These methods are useful in comparing the taste of different fluids as well as the taste of
air and fluid, determining the volume of liquid in tanks and reservoirs, discovering fluid leaks in tanks and piping,
determining the presence of humidity and the level of water in dams, and checking the juices of industrial absorption
[5].
OFCS are preferred by a growing number of fiber optic transducers. These devices are intense devices; they
allow the total or partial internal reflection of light to the surface of the element sensor while remaining in contact
with the nearby medium. The reliable reflection factor is a function of the refractive index of the two media.
Therefore, the reflection coefficient is a measure of the refractive index and concentration of the nearby medium.
The standard is based on the power refraction of the light wave guided in the fiber cladding in the form of an
evanescent wave [4, 5]. Optical fiber nano-diameters, which have also been discussed in studies as optical
nanowires, photonic nanowires, and optical fiber nano-wires, are tapered with a sub-micrometric uniform waist
section. Optical fiber nano-diameters are mass produced from optical fibers; they maintain the original optical fiber
size at their pigtails to which they are connected by narrow change-over regions. They act as sensors by etching the
clad segment with an HF solution [6]. These results can be construed in terms of solute–solute and solute–solvent
interactions and the structure making or breaking ability of solutes in the given solution. In this study, a simple,
intensity-modulated, fiber optic sugar sensor determines the change in the refractive index and concentration of the
liquid. Afterwards, an experiment is conducted using two methods to measure the concentration of the liquid; the
first utilizes cell cavity and the other, thin optical fiber sensors and spectra photonics.
THEORY
The nano-fiber diameter is numerically evaluated to determine the propagation behavior of light with bound rays
and tunneling rays. The proposed method of evaluation utilizes the element sensor segment as well as the refractive
index and concentration index to investigate the transmission characteristics. A ray of light that travels through the
2012 National Physics Conference
AIP Conf. Proc. 1528, 461-466 (2013); doi: 10.1063/1.4803645
© 2013 AIP Publishing LLC 978-0-7354-1153-1/$30.00
461
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3. core medium via the total internal reflection is called a bound ray. The intensity of the bound ray is contained
completely in the core and can propagate indefinitely without loss of power. However, the electromagnetic field is
not abruptly reduced to zero at the interface between the core and cladding. The electromagnetic field decays
exponentially at a distance starting from the interface extending into the cladding; this extended field is called the
evanescent field [7]. The evanescent field in the etched tapered segment can directly interact with the analytic
producing absorbents that can be coupled into the fiber core to produce intense modulation. Another category of
rays is leaky rays or tunneling rays, which are partially confined to the core region and attenuate continuously,
radiating their power output at the core as they propagate along the fiber [7]. These power radiations out of the
waveguide result from a quantum–mechanical phenomenon known as the tunnel effect.
Intensity Modulation Sensors
Intensity-modulated sensors are the simplest and easiest to recognize sensors. These sensors are widely studied
in the field of fiber optics. These sensors employ modulation of the amplitude of transmission in the sensing region
of the fiber. The light transmitted through an optical fiber varies in amplitude or intensity in the presence of an
external perturbation P. If the field propagating express as:
ൌ ୭ …‘•ଶ
Ʌ (1)
where Ʌ ൌ Ⱦ and Ⱦ ൌ
ଶ஠
୏
. Here K is the propagation constant and L is the length of the fiber. The change in the
mechanical structure of the fiber, led the change in intensity due to the perturbation P is given by:
ୢ୍
ୢ୔
ൌ
ୢ୍
ୢ஘
ୢ஘
ୢ୔
ൌ ଴
ଶ
ሺ•‹ ʹȾሻሺ
ୢஒ
ୢ୔
൅ Ⱦ
ୢ୐
ୢ୔
ሻ (2)
Equation 2 shows that the change in the intensity of the perturbation is directly related to the change in the
mechanical structure of the fiber and the refractive index profile change in the fiber. An advantage of this technique
is that the intensity of the light emanating from the fiber is directly measured, which is the ultimate measurement in
any fiber optic sensor. The resolution of the emanating light is relatively good. The received optical power and
desired bandwidth are such that the intensity sensitivity of the detection is primarily limited by shot noise (owing to
the statistical nature of the rate of arrival of photons at the detector) and thermal noise. The minimum observable
increment in optical signal level is proportional to the esquire root of the arrival of photons in the time of interval.
Thus, if the modulation signal from the sensors is small, the signal-to-noise ratio is reduced. Intensity modulation-
based sensors are not absolute devices; hence, they require calibration.
EXPERIMENTAL
Sucrose is a disaccharide sugar with a molecular number of C12H22O11. It can be prepared by mixing glucose
and fructose. Glucose and fructose are monosaccharide with similar molecular formulation, C6H12O6, but different
structures. Glucose and fructose have different classifications based on hydrocarbon results. Glucose is classified as
an aldehyde, whereas fructose is classified as a ketone [8]. The spectral response of the NIR wavelength toward
different concentrations of aqueous monosaccharide solutions comes from the mixture of sugar and water. The
spectral properties produced by the organic compounds can be improved by deducting the spectrum of pure water
from the original spectra [9]. The addition of sugar to water induces a chemical phenomenon known as ‘‘structure
manufacturer,’’ which can be observed through NIR spectra at sugar concentrations above 40%. This phenomenon
is due to the effect of the increasing stability of bound water particles formed by water molecules, owing to an
increase in space between water molecules. At sugar concentrations around 40%, the sugar–sugar connection is
armored and followed by water–sugar disconnection. The source of light utilized in the setup is a stabilized white
light that produces different wavelengths. The experiment is confined to the use of silicone fiber (125/60 μm) and
utilizes nano-fibers as element sensors. The nano-fibers inject optimum power into the utilized fiber. The
spectrometer (JAZ) is connected to the second end of the fiber through an appropriate connector.
The power coming out of the fiber serves as the transmission scale with different wavelengths.
An experiment was conducted to monitor changes in the spectra of sliced pear; the changes in the spectra were
observed during a process of dehydration. The experiment clearly revealed that the sharp absorption band at
1406 nm decreased in intensity during dehydration. An absorption band at 1430 nm was detected as a shoulder when
the flesh was dehydrated to below 45% water content. NIR of 1400 nm to 1440 nm and 1900 nm to 1950 nm have
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4. frequently been applied in the quantitative analysis of water content in food, owing to the strong NIR absorption
bands of water within these ranges [10, 11].
The overall experiment setup was conducted using spectroscopic instrumentations from Ocean Optics. The setup
is illustrated in Fig. 1. The chemical (sucrose in powder form) was diluted using distilled water (reverse osmosis)
and was calibrated using PAL-3 refractometer from Atago, Co. (Tokyo, Japan) with range of measurement
concentration from 0 to 93 Brix, resolution of 0.1 Brix, and accuracy of 0.2 Brix. Brix is used as the measurement
unit to standardize the unit of measurement for the entire research since it is scientifically used in representing sugar
concentration and is a conventional analytical technique for quality monitoring in the sugar industry [10].
The response obtained in the experiment was based only on the mixture of water with sucrose (Emory
Chemicals) and glucose (Unilab Chemicals). The purpose of the experiment is to determine the direct relationship
among the optical parameters with chemical composition.
.
FIGURE 1. The set up experiments for fabricated nano fiber and measurement the sugar solution
Spectra Collection and Data Analysis
The value of transmission was measured with a Channel Jaz Spectrometer (Channel 1: 650 nm to 1100 nm),
which utilizes a Sony ILX511B linear silicon CCD array detector with sensitivity of up to 75 photons (count at
400 nm) and 41 photons (count at 600 nm). The other traditional systems utilized prior to the tests had an integration
time of 5 ms, spectra average of 30, and boxcar smoothing of 1. The light source was a tungsten halogen lamp with
spectral emission between 360 nm and 2000 nm and a color temperature of 2960 K. The y-axis of the graph is
signified in the unit of counts for intensity in the original symbol of the spectrum graph. Counts are the raw output
data produced by the analog converter transmitted to the digital converter of the spectrometer. The Spectra Suite
software converted this measurement into transmission in the unit of OD (optical density). The reference spectrum
was obtained through an empty quartz cuvette and an element fiber optic material. Spectra Suite employs an
equation to determine the concentration of a species in the solution. The software uses this equation to evaluate each
pixel on the detector and produce the absorbance and transmission spectrums. We utilized two methods of
measurement to determine the transmission ratio for the liquids with different concentrations. The first method
involves the calibration of the sample liquid measured with a quartz cuvette, and the second method utilizes nano-
fiber optics as sensors. The reference spectrum was obtained through an optical fiber element sensor material in the
second method.
RESULTS AND DISCUSSION
The experiment utilized both channels of the spectrometer, which measure wavelengths from 200 nm to
1100 nm. However, measurement through the first channel (channel 0) revealed an insignificant coefficient of
determination. The transmission peak was identified at 760 nm, but no linear relationship could be established at that
wavelength owing to the low transmission significant results at wavelengths between approximately 940 nm and
985 nm. Therefore, a detailed analysis was performed with a quartz cuvette within this range of wavelength for the
different concentrations of sugar. Figures 2 and 6 show the resultant linear regression generated between
transmission and sugar concentrations. Figure 6 shows that a high concentration of sucrose leads to minimal
transmission of a specific range of NIR wavelength. A high Brix means high concentration or percentage of sugar
content per amount of water (i.e., 40 Brix of sugar contains 40% sugar against 60% water). We believe that the low
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5. transmission of NIR in this case is caused by the high percentage of water in the sample resulting from the increase
in sugar concentration.
.
FIGURE 2. The transmission light as sugar solution concentration (C %) using cavity cell, show the peak transmission in
wavelength 980 nm as C%
Analysis of data on utilizing nano-fiber optic sensors is presented in Figs. 3, 4, 5, and 6. Figure 3 presents the
spectrum transmission of the fiber optic under etching time. The levels of transmission decreased with etching time.
Figure 4 show that the peak transmission as etching time decreased the core fiber optic. Two regions are noted: a
weak evanescent field and strong evanescent field.
.
FIGURE 3. The transmission spectrum for fiber optic through etching time “fabricated the element sensors using HF 49% with
different time of etching and using NaOH 5N to remove the HF solution
FIGURE 4. The peak transmission in fiber optic as etching time for wavelength 760.6 nm
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6. The absolute sugar concentration was determined by measuring the change in absolute intensity arising from the
evanescent field of light in the sensing region. Figure 5 shows variation in peak transmission, which decreased the
concentration of the sugar solution. The variations in the two curves are linear with different variation values.
Finally, Figure 6 shows that peak transmission increased with the concentration of the sugar solution as guiding
liquid light. The refractive index of the liquid was proportional to the concentration of the liquid surrounding the
core. The variation in output power with the refractive index of the liquid and concentration of the solution acted as
cladding for the exposed portion (i.e., the sensing region); it is the main feature of the present work. Power loss is
the difference between the power launched and power collected at the second end of the fiber. Figure 5 shows the
transmission level with sugar solution as the guiding medium for a 2 cm core exposed to sugar solution that
surrounds the thin diameter core of the fiber optic. Density, viscosity, and refractive index served as important and
effective basic data in process simulation, equipment design, solution theory, and molecular dynamics.
FIGURE 5. The transmission spectrum for nano fiber surrounded by sugar solution concentration
FIGURE 6. The transmission sugar solution concentration C% in nano fiber optic and the peak transmission of light through the
cavity cell
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7. CONCLUSIONS
The measurement of Àuid concentration in real time has been of great interest to numerous engineering and
biomedical disciplines. A ¿ber optic sensor was devised in this study to sense the variation of the refractive index of
sugar at different concentrations in distilled water. The findings are signi¿cant to the development of instruments in
a number of ¿elds of activity. The quality of the sugar solution that utilized nano-fiber optics as sensors increased.
Nano-fiber optics is easy to fabricate and entail low cost. In a single wavelength application, peak transmission was
determined to be at a wavelength of 980 nm for all the sugar solutions. This result is attributed to the transmission
band of the water constant. Further experiments should consider other associated parameters so that in the future, the
use of nano-fiber optic sensors would support the development of particular optical instruments of liquid quality.
ACKNOWLEDGMENTS
The authors would like to acknowledge the financial support from the Universiti Sains Malaysia at Grant
(1001/PFIZK/843106).
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