2022 International Conference on Radar, Antenna, Microwave, Electronics, and Telecommunications (ICRAMET) | 978-1-6654-5412-4/22/$31.00 ©2022 IEEE | DOI: 10.1109/ICRAMET56917.2022.

9991212
 2022 International Conference on Radar, Antenna, Microwave,
Electronics, and Telecommunications (ICRAMET)
Virtual Conference, 6th – 7th November, 2022
2022 International Conference on Radar, Antenna, Microwave, Electronics, and Telecommunications (ICRAMET) | 978-1-6654-5412-4/22/$31.00 ©2022 IEEE | DOI: 10.1109/ICRAMET56917.2022.9991214

Organizer

Advisory Board
Dr. Eng. Budi Prawara Head of Organization Research of Electronics and Informatics
BRIN, Indonesia

Dr. Dipl. Ing. Michael Andreas Purwoadi, Head of Research Center for Telecommunication BRIN, Indonesia
DEA

Yusuf Nur Wijayanto, Ph.D. Head of Research Center for Electronics BRIN, Indonesia

Dr. Ing. Wahyudi Hasbi, S.Si, M.Kom Chair of the IEEE Indonesia Section

Organizing Committee
Conference Chair

Dr. Yana Taryana, M.T. Research Center for Telecommunication BRIN, Indonesia

Conference Vice-Chair

Yuliar Firdaus Ph.D. Research Center for Electronics BRIN, Indonesia

Technical Program Committee

TPC Chair

Budiman Putra Asmaur Rohman, Ph.D. Research Center for Telecommunication BRIN, Indonesia

TPC Co-Chair

Ken Paramayudha, S.T., M.Phil. Research Center for Telecommunication BRIN, Indonesia

Track Chairs

Hana Arisesa S.T., M.Eng. Research Center for Telecommunication BRIN, Indonesia

Arief Budi Santiko S.T., M.T. Research Center for Telecommunication BRIN, Indonesia

Fajri Darwis S.T., M.Eng. Research Center for Telecommunication BRIN, Indonesia

Dr. Lia Aprilia Research Center for Photonics BRIN, Indonesia

Dr. Suyoto, M.T. Research Center for Telecommunication BRIN, Indonesia

 2022 International Conference on Radar, Antenna, Microwave,
Electronics, and Telecommunications (ICRAMET)
Virtual Conference, 6th – 7th November, 2022

Salita Ulitia Prini S.Kom., M.T. Research Center for Telecommunication BRIN, Indonesia

Dayat Kurniawan M.T. Research Center for Telecommunication BRIN, Indonesia

Publication

Mochamad Mardi Marta Dinata M.T. Research Center for Telecommunication BRIN, Indonesia

Arumjeni Mitayani M.T. Research Center for Telecommunication BRIN, Indonesia

Riyani Jana Yanti, S.T. Research Center for Telecommunication BRIN, Indonesia

Rizky Rahmatullah, A.Md.T. Research Center for Telecommunication BRIN, Indonesia

Secretariat
Secretary

Chaeriah Bin Ali Wael M.T. Research Center for Telecommunication BRIN, Indonesia

Treasurer

Asih Setiarini S.T., M.Sc. Research Center for Telecommunication BRIN, Indonesia

Event Programs

Nadya Larasati Kartika M.Si. Research Center for Telecommunication BRIN, Indonesia

Ardita Septiani S.T., M.Sc. Research Center for Advanced Materials BRIN, Indonesia

Facilities and Equipment

Yulia Rosidah, S.AB. Bureau for Public Communication, General Affairs, and Secretariat
BRIN, Indonesia

Prajni Duhita Parawitasari Bureau for Public Communication, General Affairs, and Secretariat
BRIN, Indonesia

Nurul Fajriyah S.Sos. Bureau for Public Communication, General Affairs, and Secretariat
BRIN, Indonesia

Promotion Section

Teguh Praludi, M.T. Research Center for Telecommunication BRIN, Indonesia

Noorfiya Umniyati, M.I.Kom. Bureau for Public Communication, General Affairs, and Secretariat
BRIN, Indonesia

IT and Documentation
 2022 International Conference on Radar, Antenna, Microwave,
Electronics, and Telecommunications (ICRAMET)
Virtual Conference, 6th – 7th November, 2022

Herry Samsi, S.T.,M.T. Center for Scientific Data and Documentation BRIN, Indonesia

Anton Surahmat S.I.Kom. Bureau for Public Communication, General Affairs, and Secretariat
BRIN, Indonesia

Siti Kurniawati Fatimah, S.Kom Center for Scientific Data and Documentation BRIN, Indonesia

Scientific Committee
1. Prof. Hiroshi Murata Mie University, Japan
2. Prof. Mustapha Yagoub University of Ottawa, Canada
3. Prof. Arezki Benfdila Mouloud Mammeri University Tizi-Ouzou, Algeria
4. Prof. Mohand Lagha Blida1 University, Aeronautical Science Laboratory, Algeria
5. Prof. Shashikant Patil ViMEET Raigad MS, India
6. Prof. Shahzad Ashraf Hohai University Changzhou, China
7. Dr. Wazir Zada Khan Jazan University, Kingdom of Saudi Arabia
8. Dr. Ali Rafiei University of Technology Sydney, Australia
9. Dr. Joni Simatupang President University, Indonesia
10. Dr. Azremi Abdullah Al-Hadi University Malaysia Perlis, Malaysia
11. Dr. Hussain Saleem University of Karachi, Pakistan
12. Dr. Mustafa Shakir Superior University, Pakistan
13. Dr. Sandhya Save University of Mumbai, India
14. Dr. S Kannadhasan Cheran College of Engineering, India
15. Dr. Amit Rathi, Manipal University Jaipur, India
16. Mr. Iwan Adhicandra University of Sydney, Australia
17. Mr. Kuncoro Wastuwibowo Telkom Indonesia, Indonesia
18. Mr. Sumer Can Diodes, Inc.
19. Mr. Udhaya Kumar Dayalan Trane Technologies, United States
20. Prof. Goib Wiranto Research Center for Telecommunication BRIN, Indonesia
21. Dr. Purwoko Adhi Dipl.Ing.,D.E.A. Research Center for Telecommunication BRIN, Indonesia
22. Dr. Yuyu Wahyu, M.T. Research Center for Telecommunication BRIN, Indonesia
23. Pamungkas Daud, M.T. Research Center for Telecommunication BRIN, Indonesia
24. Dr. Dedi, M.T. Research Center for Advanced Materials BRIN, Indonesia
25. Dr. Nasrullah Armi Research Center for Telecommunication BRIN, Indonesia
26. Dr. Novrita Idayanti Research Center for Advanced Materials BRIN, Indonesia
27. Lia Muliani M.T. Research Center for Electronics BRIN, Indonesia
28. Yusuf Nur Wijayanto, Ph.D. Research Center for Electronics BRIN, Indonesia
29. Dr. Natalita Maulani Nursam Research Center for Electronics BRIN, Indonesia
30. Dr. Erry Dwi Kurniawan Research Center for Telecommunication BRIN, Indonesia
31. Dr. Agus Subekti Research Center for Telecommunication BRIN, Indonesia
32. Mr. Ana Heryana Research Center for Data and Information Sciences BRIN,
Indonesia
 2022 International Conference on Radar, Antenna, Microwave, Electronics, and Telecommunications

Microfluidic for supporting Fiber-optic-based

Surface Plasmon Resonance sensor
2022 International Conference on Radar, Antenna, Microwave, Electronics, and Telecommunications (ICRAMET) | 978-1-6654-5412-4/22/$31.00 ©2022 IEEE | DOI: 10.1109/ICRAMET56917.2022.9991238

Asih Setiarini Lia Aprilia Wildan Panji Tresna

Research Center for Research Center for Photonics, Research Center for Photonics,
Telecommunication, National Research National Research and Innovation National Research and Innovation
and Innovation Agency, Bandung, Agency, South Tangerang, Banten Agency, South Tangerang, Banten
Indonesia 15314, Indonesia 15314, Indonesia
asih003@brin.go.id liaa003@brin.go.id wild004@brin.go.id
Dedi Riana Gandi Sugandi
Department of Physics, Maulana Malik Ibrahim Malang State Research Center for Telecommunication, National Research and
Islamic University, Malang, East Java 65144, Indonesia Innovation Agency, Bandung, Indonesia
ddediriana@gmail.com gand001@brin.go.id

Abstract—Microfluidic has been developed to be applied as strong optical field constraints, and accessible surface
sensor and sensor support because of its small size (in the modification.
micrometer range), compact structure, low analyte Combining microchannels and optical fibers in
consumption and can be integrated into a chip. The microfluidic chips is essential to fluid detection. The light
combination of microfluidic and optical systems (optical fiber) field created by an optical path and a microfluidic system
has been widely used among microfluidic-based sensors. Based promotes the interaction between light and fluid. The fiber
on its sensing principle, an optical fiber-based surface plasmon
optic sensor is sensitive to response external changes in the
resonance (SPR) sensor is very promising for detecting
microchannel. An analyte can be observed in the
bacteria, viruses, chemical molecules, etc. In this paper, we
discuss microfluidics research for supporting fiber-optic
measurement by analyzing the change in light characteristics,
sensors in detail, such as device fabrication and application of such as wavelength, phase, amplitude, intensity, polarization,
integrated microfluidic-optical fiber-based SPR sensors. frequency, etc.
Factors affecting sensitivity, such as the gold layer thickness, The typical structure of the optical fiber sensor is shown
and the effect of the sensing area were studied through in Fig. 1. Based on the sensing principle, the optical fiber-
simulation to strengthen the understanding of the sensor. based sensor consists of surface plasmon resonance fiber
(SPR) [3], tapered fiber [4], fiber grating [5], Mach–Zehnder
Keywords—microfluidic, optical fiber, surface plasmon
interferometer [6], and Fabry-Perot Cavity [7], etc. Among
resonance, gold layer thickness, sensing area
the sensor type, the SPR sensor has been extensively
developed. The basic principle employs optical phenomena,
I. INTRODUCTION such as the total internal reflection of a fiber core-metal
Microfluidic has attracted the wide attention of many layer-analyte medium. At the interface of the core-metal
researchers to be applied as sensor and sensor support in layer, a portion of light called an evanescent wave passes
chemistry, biology, biochemical, medicine, etc. due to its through the metal and decays exponentially. At the interface
many advantages, such as compact structure, compact, low between the metal layer and analyte medium, the surface
cost, and low analyte/sample. The small sample volume plasmon wave is generated by the plasmon oscillation at the
could improve the reaction rate and shorten detection time metal surface. For optical fiber-based SPR sensing,
compared to the traditional method, using microfluidic. integrated with microfluidic can protect the sensors from the
Channels in microfluidic are usually tens to hundreds of influence of the external environment, improving a stable
microns in size. We can make a difference in microchannel sensing environment for fragile optical fiber structures. Some
structures and control the small volume of fluid depending factors influencing optical fiber-based SPR sensor sensitivity
on the required functions [1]. are the thickness of gold, sensing area, the diameter of its
So far, an integrated microfluidic chip has been core, mode type, etc.
developed for detection, separation, extraction, or mixing This paper discusses the research of microfluidics for
samples. The integrated detection or sensing function has supporting fiber-optic sensors in detail, reviewing some prior
been used for many purposes among the microfluidic's works and conducting simulations to analyze some aspects,
variation functions. Sensors using microfluidic chip have such as the effect of gold layer thickness and length of the
been fabricated to measure fluid flow rate, fluorescence sensing zone. The structure of this paper will be shown as
detection, cell classification, transmittance/absorbance follows: device fabrication of optical fiber sensor and
measurement, refractive index of the sample [2], etc. microfluidic is introduced in detail in section 2. Some
The combination of microfluidic and optical systems has application of integrated microfluidic and optical fiber-based
been widely used among microfluidic-based sensors. Optical sensor is reviewed in section 3. The simulation for
fibers become an appropriate optical transmission carrier to optimizing the optical fiber-based sensor (especially SPR) is
better integrate light with the microfluidic chip and realize studied in section 4.
sensing measurement. The optical fiber comprises cladding
and a core. Light is transmitted in the fiber's core by total
reflection because of the difference in refractive index (RI)
between the cladding and the core. The advantages of optical
fiber for sensing are small size, large surface area-to-volume
ratio, corrosion resistance, biocompatible, easy integration, Fig. 1. Structure of optical fiber sensor device

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 II. DEVICE FABRICATION REVIEW

A. Techniques to make an optical fiber sensor

Generally, the optical fiber is not sensitive to the
refractive index of the surrounding because the cladding
prevents penetrating the high-order mode into the
surrounding/analyte [8]. Hence, the cladding must be
removed to make the optical fiber sensitive to the
surroundings and define the sensing area. In this section, we
discussed the technique to prepare the D-type and unclad
optical fibers applied for the SPR sensor.

1) D-type optical fiber

A D-type optical fiber is a fiber with a side polish of the
cladding. Several techniques to make D-type optical fiber
are discussed. [9] used polymethyl methacrylate (PMMA)-
based optical fiber to measure refractive index change based
on SPR. The optical fiber used mechanical polishing using Fig. 3. V groove holder to polish one side of optical fiber [11].
the abrasive paper of 5000 mesh roughness and grain size of
The reaction of HF and SiO2 generates a bubble of SiF4
2.6 μm. Then the polished optical was cleaned by pure
(1) and a solid H2SiF6 (2). The chemical reaction is
acetone with ultrasonic for 15 min and absolute ethanol for
described below [14].
5 min and dried. The fiber-based SPR sensor exhibited a
SiO2 + 4HF  SiF4 ↑ + 2H2O (1)
sensitivity up to 3328.1 nm/RIU in the refractive index
SiO2 + 6HF  H2SiF4↓ + 2H2O (2)
range of 1.334–1.388 [9].
Zainuddin et al. proposed a refractive index biosensor The etching rate of the cladding material is related to
SPR-based optical fiber [10]. The D-shaped optical fiber etching time, temperature, and HF concentration. The
was prepared using a silver nanofilm and wheel polishing reaction products (bubbles and sols) heterogeneously
method. First, a 2 cm optical fiber jacked was removed, and adhering to the fiber surface slow down the etching reaction
the fiber was fixed at the fiber clamper. Then, using a [15]. Although the fabrication method is low-cost and
sandpaper grinding wheel, the fiber thickness was reduced simple, HF is toxic to humans and the environment. So,
by varying the wheel rotation speed (Fig. 2). The sensitivity alternative fabrication methods are developed.
using the polished method was 2166 nm/RIU for distilled Dwivedi et al. used flame-burning techniques to burn the
water (n = 1.333) and 208.33 nm/RIU for alcohol (n = jacket and clad the fiber to establish a sensing zone [16].
1.345) [10]. After that, the cladding was wiped then the area was cleaned
Chen et al. manually removed one side of the jacket and with acetone. Sensitivity, signal-noise-ratio (SNR), and
clad the optical fiber placed in the V groove holder with a resolution of variations in the length of the sensing zone (10,
sharp blade [11]. In the experiment, the V groove and the 15, 20, and 25 mm) were observed. The sensitivity was
two holders were used to fix the optical fiber, as shown in obtained to 2.67-2.78 µm/RIU [16]. The drawback of this
Fig. 3. A side of the optical fiber outside was exposed by method is difficult to control the thickness of the removed
setting the angle (α) and width (W) of the V grooves. Both cladding and the sensing area.
sides of the sensor are polished sufficiently with abrasive A different technique was employed by Wang et al.,
papers with a roughness of 4 degrees. Then, it was cleaned which uses a shape blade to peel the fiber cladding. After
in acetone and distilled water 3 times. the cladding was peeled, the probe was cleaned with acetone
and deionized water three times. After that, the sensing zone
2) Unclad/etched optical fiber was coated with 50 nm gold. The method is a simple and
Unclad or etched-type optical fiber is a fiber with whole relatively easy fabrication, so it is possible to be batch
polished cladding to make the fiber sensitive to the produced and controlled with good consistency. They
surrounding sample. Usually, the optical fiber cladding, obtained a sensitivity of about 2660 nm/RIU for RI of 1.334
which is fused silica (SiO2), is removed by hydrofluoric acid - 1.359 [17].
(HF) [12-13]. Sultan and his group used a suitable blade to remove a
clad from a multimode fiber with a core diameter of 600 µm
to create an unclad sensing zone of 10 mm. After that,
acetone, methanol, and distilled water were used for
cleaning. Then, the sensing area was coated with metal (Au
Fig. 2. A fabrication process for side-polished/D-shaped optical fiber, or Ag) using DC sputtering. The sensor was tested to
reproduced from [10]. measure the concentration of glycerin in water. The
sensitivity was achieved up to 3.340 nm/RIU for Au and
2.980 nm/RIU for Ag [18].

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B. Laser-based processes for microfluidic fabrication Microstereolithography (μSLA) is a type of
This section reviews microfluidic laser fabrication stereolithography with rapid fabrication, which consists of a
methods, including two-photon polymerization, laser, a sample holder, a tank for photopolymer, and
stereolithography (SLA), and micro stereolithography precision positional control for laser moving. In the process,
(µSLA). the laser scans the sensitive polymer surface based on the
Lasers can be used to fabricate a small-volume information from each workpiece cross-section. Then, liquid
microfluidic device, including channels, holes, and complex polymer cross-links and solidifies when exposed to laser
geometry. For machining polymers, femtosecond (fs) laser light. The sample holder pushes the solid structure
and UV light provide the best precision with resolutions of downward, forming the next cross-section. The entire
several microns and less than 50 µm for fs laser and UV, structure may be produced with a successive layer. This
respectively. Mohamed and his group employed a CO2 laser technique may create complex structures, and the minimum
engraving or cutting system to achieve small (50–500 µm) feature size is restricted to the positioning controls' laser
and large (> 500 µm) aspects in a microfluidic [19]. Rogal focus and movement resolution. This technology can also
et al. fabricated a microfluidic using a fs laser and micro-
manufacture specific metal and ceramic pieces after further
milling to capture a tumor cell [20]. The CO2 laser was also
used by Li et al. to make capillary circuit components such curing and annealing operations.
as trigger and bursting valves for retention in a PDMS In the beginning, µSLA systems scanned through each
substrate for sample-reagent mixing and liquid delivery cross-section in a point-by-point method. The current
[21]. Ni et al. involved a UV laser with a wavelength of advanced systems employ projection rather than laser
355nm and a Power max of 15 W to make grooves in the scanning to harden the whole cross-section at once. A
polyvinyl chloride (PVC) layer in the fabrication of a liquid-crystal display controlled by a computer and digital
microfluidic supporting biosensor [22]. micro-mirrors are used as projection or spatial light
Another technique is two-photon photopolymerization modulators to direct laser beams for constructing features of
(2PP), which can produce ultra-small features with a each cross-section. Another system uses two laser beams
resolution of up to 100 nm. The advantages of this method with a minimum resolution of a hundred-nanometre range to
are a nonvacuum process, no need for a mask or molding for create fine focus.
fabrication, and easy operation and maintenance. Using a Compared to the two-photon photopolymerization and
focused laser, the 2PP can make polymerization reactions SLA techniques, μSLA offers a short turn-around time, so it
for the light-sensitive material. For forming 3D structures is appropriate for manufacturing. For the µSLA resin
with a resolution <100 nm, the fs laser beam (10-15 seconds) improvement, Mannel et al. developed a Perfluoro-hexyl-
is used. The ultrashort pulse initiates intensive nonlinear diacrylate-based polymer (PFHDA) for high-resolution 3D
processes with relatively low power and can avoid thermally printing microfluidic using µSLA [26] because just a few
damaging the sample. resin formulas appropriate for µSLA chemically resistant
Emons et al. improved the resolution of 2PP by adding a polymers have been demonstrated. They obtained water-in-
cross-linker to the Zr-hybrid material (standard sol-gel). oil (W/O) emulsions in a 3D-printed droplet maker with
Next, using the fs laser pulse, the resolution gained about 50 planar microchannel geometry constructed from PFHDA-
nm [23]. In the biosensor and microfluidic application, based resin, resulting in droplets with an average diameter
Mandt et al. reported that 2PP could be a possible of 271 µm ± 26 µm [26].
manufacturing technology for establishing a versatile For our project, we used SLA for microfluidic
biomimetic on-chip barrier structure using GelMOD-AEMA fabrication. The SLA machine uses a UV LED with a
or gelatine-modified methacryl-amides and methacrylates wavelength of 405 nm, and liquid UV resin (PMMA and
[24]. PLA) is used as the material. The minimum microfluidic
Next, stereolithography (SLA) is a revolution in channel is 50 nm. SLA can also be used to design
microfluidic manufacturing processes due to its capacity to microfluidic mold parts. For example, if microfluidics are
produce highly detailed structures. By laser-induced desired, use PDMS as the material. SLA is the innovation of
polymerization, it is possible to build a part layer by layer. the microfluidic fabrication technique.
In the process, the focused laser beam scans the surface of
the photosensitive liquid and induces the local III. APPLICATION
transformation to be solid, creating the shape of one layer
object. After one layer is finished, the new resin is spread on The microfluidic device can support the sensor because
of its small size (in the micrometer range), compact
top of the object's transformed part, and the next layer's
structure, low analyte consumption and can be integrated
laser-induced solidification. SLA technique uses a
into a chip. The combination of microfluidic and optical
photopolymer and UV laser beam, and SLA hardens the systems (optical fiber) has been widely used among
photopolymer as it passes through a UV laser beam focused microfluidic-based sensors. Based on its sensing principle,
on a set of coordinates. The laser traces the geometry by an optical fiber-based surface plasmon resonance (SPR)
moving from point to point. It causes the SLA to be more sensor is very promising for detecting bacteria, viruses,
accurate and better print quality among 3D printing chemical molecules, etc. In this chapter, we will summarize
techniques [25].

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and review the application of microfluidic SPR in sensing
principle and system design.

A. Microfluidic SPR for Coronavirus Detection

On March 2020, WHO announced that we have the
Covid-19 pandemic. The large number of infected leads to
extensive study of the virus in the body to reduce the virus's
spread. Quantitative real-time polymerase chain reaction
(qRT-PCR) is a method for analyzing a variety of biological
samples for COVID-19, but it is time-intensive and may be
difficult to use in remote or resource-limited settings [27].
To make SARS-CoV-2 diagnostics simpler, more
affordable, and more widely available, researchers are
strongly motivated to create trustworthy testing tools [28- Fig. 4. A structure of an LSPR-based sensing system with an optical
probe and gold nanospikes inserted in a microfluidic device,
30], SPR is an effective method for gathering label-free, in- reproduced from [33]
the-moment data on the interaction of two binding entities.
Plasmonic sensing have been created to support the
conventional SARS-CoV-2 diagnostic approaches [31-34].
Funari et al. built a microfluidic SPR biosensor to detect
the quantity of anti-SARS-CoV-2 spike protein antibodies in
diluted human plasma by relating the wavelength shift of the
localized surface plasmon resonance (LSPR) peak of gold
nanostructures in the microfluidic device following binding
contacts with the SARS-CoV-2 spike protein. A schematic
diagram of an LSPR-based sensing system with an optical
probe and gold nanospikes inserted in a microfluidic device
is shown in Fig. 4.
For the sensor's signal-to-noise ratio to be improved by Fig. 5. (a) The optical-microfluidic chip schematic design: (1) are two
antibody-antigen binding, the sensor must be validated for inlets, (2) is outlet, (3) is a spiral mixture, (4) are optical fibers and (5)
COVID-19 antibody tests and the electrode position method is the embedded LPG sensor. (b) The optical resonance of LPG
must be optimized to create gold nanostructures with a biosensor and mode coupling [36].
smaller gap and a higher aspect ratio [33]. A highly
sensitive and quick technology called opto-microfluidic IV. SIMULATION
sensing has been used to find antibodies against the SARS-
CoV-2 spike proteins in diluted human plasma. A. Simulation Method
The Finite-Difference Time-Domain (FDTD) method
B. Microfluidic SPR for Glucose Level Detection was used in this simulation. Fig. 6 shows the sensing zone
Glucose is a crucial metabolic intermediary and an structure of the simulated fiber optic-based SPR sensor. An
important medicinal analyte that serves as a marker for equivalent planar waveguide was established to substitute
several illnesses [35]. For diabetics have blood glucose over the sensing zone of the optical fiber sensor [37]. Then,
than 120 mg/dL. Early detection and prevention of diabetes Perfectly Matched Layer (PML) boundary conditions were
can decrease the probability acquiring diabetes problems. used for all edges of the simulation region to absorb the
The development of glucose meters for the early detection is unwanted light passing through the sensing zone. The
being done using the lab-on-a-chip, only need a single drop material of the core is SiO2 with a diameter dcore of 10 µm,
of sweat, an opto-microfluidic technology has made it representing a single-mode optical fiber, and the refractive
possible to detect glucose in solution [36]. index of the SiO2 refers to Malitson [38]. At the same time,
Yin et al. present a long-period grating (LPG) biosensor the permittivity of Au follows Johnson and Christy [39].
integration between glucose sensor and a small-diameter This simulation injected broadband light with a wavelength
single-mode fiber on a chip [36], hence for the measurement range of 400 – 1200 nm into the fiber optic sensing zone.
only need low-sample consumption and improved the The transmission monitor is placed at the end of the sensing
response time and detection range. The glucose zone to record the spectrum of light that has passed through
concentration as 10-9 M. for the design, on the edge of LPG, the sensing zone.
a hybrid sensing film with a negatively charged outer layer In this work, the Au film thickness tAu and length of the
of glucose oxidase (GOD) and multiple layers of sensing zone were optimized to get the best performance of
polyethylenimine and polyacrylic acid supporting film is the sensor. Meanwhile the width of the simulation region
coated for glucose sensing and signal amplification. Fig. 5 was fixed so that the analyte thickness will decrease or
shows the sensor design and the microfluidic output with increase depending on the thickness of Au film. This
different concentrations of glucose. The result showed that simulation used the refractive index data of pure water (na =
the microfluidic could detect glucose as low as 1 nM. 1.333) as the analyte.

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 Fig. 7. Variation of transmission curve with different thicknesses of Au
Fig. 6. Structure of the optical fiber SPR sensor in this simulation. film.

B. Effect of gold layer thickness

Simulations of SPR-Based optical fiber sensors with
variations of Au film thickness have been conducted to find
the optimal spectrum of the transmitted light which is
represented by the deepest transmission dip which indicates
the resonance process between incident light and surface
plasmon waves occurs very efficiently.
The graph in Fig.7 shows the simulation result. We can
see that the depth of the transmission dip and the resonant
wavelength change with gold thickness variations. It shows
that the resonant wavelength and the depth of the
transmission dip depend on the thickness of the coated Au
film. The energy of injected light, at the resonance
wavelength (the wavelength at which the minimum Fig. 8. Variation of the transmission curve of various lengths of the
sensing zone with a fixed Au film thickness of 40 nm.
normalized transmitted power), was transferred to excite
surface plasmon waves efficiently so that results in a dip in
the transmission curve. In the simulation of gold thickness V. CONCLUSION
optimization, the length of the sensing zone was fixed at 200
µm. We have discussed microfluidics research for supporting
The simulation result shows that the deepest dip is when optical fiber-based SPR sensors in detail. The study consists
the Au film thickness is 40 nm. Thus, by doing the of a literature review and simulation. The literature review
simulation, one can determine the optimum thickness discussed techniques to make an optical fiber sensor, such as
according to the dip depth of the transmission curve. The D-type and unclad optical fiber. Moreover, the microfluidic's
assumptions that cause changes in dip depth can be related to laser-based fabrication method was also discussed, as well as
the excited surface plasmon mode in the designed optical the review of the microfluidic's application for supporting
fiber model. Studies of surface plasmon modes in metal- optical fiber-based SPR sensors. In the simulation, the effects
dielectric-dielectric (DMD) waveguides that depend on metal of the gold layer thickness and the length of the sensing zone
thickness have been reviewed by several works [40-42]. were conducted by the FDTD method.
C. Effect of the length of the sensing zone
ACKNOWLEDGMENT
Meanwhile, the simulation of the length of the sensing
zone influences the depth of the transmission spectrum but This research is based on the project funding from the
does not change the resonant wavelength. The optimization Program House "Alat dan Deteksi Kesehatan" of the
of the length of the sensing zone was carried out with the National Research and Innovation Agency (BRIN).
optimal thickness of Au film (40 nm).
The first simulation was carried out at a length of 200 REFERENCES
µm, as shown by the red color curve on the graph (Fig. 8),
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