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Performance of white organic light-emitting diode for
portable optical biosensor
Briliant Adhi Prabowo1,7, Ying-Feng Chang2,3, Li-Chen Su2,
Hsin-Chih Lai4,#, Nan-Fu Chiu5, and Kou-Chen Liu1,6,*
1Department of Electronic Engineering, Chang Gung University, Taoyuan 33002, Taiwan
2Graduate Institute of Electro-Optical Engineering, Chang Gung University, Taoyuan 33302, Taiwan
3Molecular Medicine Research Center, Chang Gung University, Taoyuan 33302, Taiwan
4Department of Medical Biotechnology and Laboratory Science, College of Medicine, Chang Gung University, and
Department of Laboratory Medicine, Chang Gung Memorial Hospital, Taoyuan 33302, Taiwan
5Institute of Electro-Optical Science and Technology, National Taiwan Normal University, Taipei 10610, Taiwan
6Center for Biomedical Engineering, Chang Gung University, Taoyuan 33302, Taiwan
7Research Center for Informatics, Indonesian Institute of Sciences, Bandung 40135, Indonesia
Corresponding Authors:
Tel: 886-3-2118800 # 3152. Fax: 886-3-2118507. E-mail:#[email protected];
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Abstract
A white organic light-emitting diode (OLED) with enhanced sensitivity has been
demonstrated as a novel light source in a portable surface plasmon resonance (SPR) optical
biosensor. A disposable broad-spectral OLED was employed on the leg side of isosceles
trapezoid prism for a fixed angle of incident light. Bimetallic Au/Ag composition layers
were used as sensing layers and their composition evaluated such that the wavelength
resonance occurred at the peak of the light spectrum. The SPR signal detection applied
differential intensities at two reference wavelengths. We show that the integration of a
white-spectral OLED on an SPR sensor improved the sensor’s sensitivity by ~19.29%
compared to an SPR sensor system using a green OLED as a bimetallic Ag/Au sensing
layer. The limit of detection (LOD) of 2.4 × 10-6 refractive index units (RIU) has been
established in the range of refractive index samples (∆n) around 3.6 × 10-3 RIU. This
optical sensor demonstrated the capability of real-time monitoring, self-assembled
monolayer (SAM) activation, antibody immobilization, and biomolecular interaction
detection of immunoglobulin G (IgG) protein with a detection limit around 40.3 pg/mL.
Keywords: White light, OLED, portable, surface plasmon resonance, biosensor.
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1. Introduction
The development of solid-state lighting leads to broader applications; it has been
used as a replacement for light bulbs for indoor lighting, in display technology, and in
various biomedical applications. The development of blue light emitting diodes (LEDs)
based on III-V compound materials[1,2] enabled the development of low-power and
white-spectral solid-state lighting[3,4]. Owing to this milestone in the production of
energy-saving light sources, the founders of blue LED technology have been awarded the
Nobel Prize in physics for 2014. The excellence and widespread adoption of solid-state
lighting, such as LEDs, are because of the associated factors such as low cost, low power,
versatility, robustness, direct modulation, and small dimension properties [5,6]. Organic
LEDS (OLEDs) have also been noted to possess numerous advantages owing to their
remarkable heat dissipation throughout the operation, extensive color contrast, and stability
for lengthy operations[7]. Moreover, solid-state lighting for biomedical devices and related
applications have more advantages over conventional lighting (halogen or Xe lamps), such
as, low cost, disposability, portability, smaller size, and sensitivity[8–10].
Optical sensors for molecular detection have been studied for many years. One of
the acknowledged optical sensor technologies for biomolecular detection is surface
plasmon resonance (SPR) that utilizes surface plasmons (SPs). It occurs at the interfaces of
noble metal films and dielectric media, coupled with transverse magnetic (TM) light
through a high refractive index (RI) prism[11–14]. SPR sensors have emerged as notable
optical biosensors offering numerous possibilities. They allow for label-free assays and
sensitive, high specificity, rapid, and real-time monitoring for various applications in
chemical, biological, food science, environmental, and drug discovery fields[13,15,16].
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In SPR technology, the light spectra characteristics play an important role in
sensor performance and configuration. For instance, monochromatic light is suitable for
configuring an SPR sensor using angular interrogation while polychromatic light can be
applied for SPR sensing with wavelength interrogation[13]. Angular interrogation has been
reported to achieve the best performance compared to intensity and wavelength
interrogation[17]. Nevertheless, the design implementation of the angular detection
method requires a single-mode light source and a high-resolution motor stepper to couple
light in various angles of incidence. Particularly, moving mechanical parts, such as a
rotation motor or a scanning detector, are drawbacks for optical platform fabrication and
for the synchronization system of scanning light sources and detectors in portable
applications. Another SPR sensor configuration applied a camera cathode display (CCD)
array as the photodetector to account for various reflected light angles. However, a bulky
lens is required for the incident single-mode light to couple the sensing area under various
incident angles. Consequently, the angular and wavelength interrogation methods in SPR
sensing offer different advantages and disadvantages depending on the user needs,
simplicity of apparatus design, and application purpose.
SPR sensor light sources based on broad-spectral solid-state lighting have been
presented in several reports[14,18–23]. Early SPR sensor configurations utilizing white LED
reached a detection limit of 1.98 × 10-4 RI units (RIU)[18] and ~1.65 × 10-3 RIU[14] with the
inclusion of a Kretschmann prism coupler and an optical fiber guide apparatus, respectively.
Polychromatic LED light implemented in an SPR-sensor-based grating configuration achieved a
resolution of 3 × 10-7 RIU[24]. It was reported that a red-green-blue (RGB) light source from an
OLED was integrated to obtain a broad-spectral SPR sensor application and established a limit of
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detection (LOD) of 6 × 10-4 RIU[22]. A non-portable SPR sensor based on a white-spectral source
has measured the SPR signal change corresponding to an SPR excitation with a fixed angle of
incidence[25]. Compared to laser-based detection schemes, white-spectral-based SPR offer
optimum sensitivity and reach a wider dynamic range without sacrificing the detection
resolution[25].
Here, we propose a novel white-spectral OLED for a portable SPR sensor based on the
Kretschmann prism configuration. White OLEDs have several benefits for portable biosensors,
such as high power efficiency, high performance, durability, manufacturability, low-cost
fabrication[26,27], and disposability. A detection limit around 2.6 × 10-7 RIU in the range of RI
(∆n) around 3.6 × 10-3 RIU has been achieved in this study. Moreover, by utilizing a bimetallic
Au/Ag sensing layer, real-time monitoring of self-assembled monolayer (SAM) activation and
biomolecular interaction is demonstrated with a detection limit around 40.3 pg/mL.
2. Methods
2.1 Simulation setup
Parameters to be considered for SPR sensor development include wavelength of
the light source, incident angle of the light, sensing layer composition, and nonlinear
refractive indices of the metal[28], substrate, prism[4,5], and medium[31]. Theoretically,
the propagation constant of the SP wave (kSP) can be expressed by [15],
)()(
)()(2
)()(
)()(
dm
dm
dm
dmSP
ε+ε
εε
λε+ε
εε
c=k
. (1)
While the wavevector of the incident light can be described as,
θnλ
θnc
=k PPx sin )(2π
sin )(
, (2)
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where εm and εd are the dielectric constants of the metal and the analyte medium,
respectively; np is the RI of the prism; and λ and θ are the wavelength and the incident angle
of light, respectively. The SPR occurs when kx=kSP. The parameter and design
considerations of the SPR sensor are more complicated in the case of polychromatic light
owing to several parameters in Eqs. (1) and (2) being wavelength dependent.
In this article, the optimization and parameter tuning for SPR sensor development
based on a Kretschmann coupler was simulated using the Essential Macleod v.9.8.432
(Thin Film Center Inc., USA). The refractive indices of water and gold were obtained from
the Hale and Querry model[31] and the Johnson and Christy model[28], respectively,
instead of the default values provided in the simulation tool. Sucrose water dilution
refractive indices were used from an open data table.
2.2. Metal sensing layer fabrication
An Au/Ag bimetallic composition was used for the experiments. The BK7
substrates were prepared in an immersion first in acetone solution, then in isopropyl
alcohol solution, and finally in distilled water (DI) water, each under oscillation in an
ultrasonic bath for 15 min. Subsequently, the BK7 substrate was cleaned by N2 gas and
heated to 120 °C for 3 min to remove water from the substrate surface. A thin metal film of
chromium, gold, and silver was then deposited on the substrate under high vacuum
pressure (< 1 × 10-6 Torr) and low deposition rates (< 1 nm/s) at room temperature (~ 27 °C)
by thermal evaporation. A 3-nm chromium interlayer was deposited over the BK7 substrate
as an adhesion material prior to the metal film deposition. The sensing bimetallic 40 nm
and 10 nm of Ag and Au were successively deposited such that the Au film covered the Ag
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film, protecting it from oxidation.
2.3 Integration system and methodology
The configuration of the portable SPR sensor is shown in Fig. 1(a). A BK7
trapezoidal prism (n = 1.515) with an angle θ = 75° corresponding to the incident angle of
the white light was used. White OLEDs (e-Ray Optoelectronics Tech. Co., Ltd., Taiwan)
were employed to emit broad-wavelength light with peaks at 510 nm and 580 nm (Fig.
1(b)). Next, the OLED substrates were coated with an optically clear adhesive (OCA) film
(3M, USA) after which a brightness enhancement film (BEF) (Efun Tech. Corp., Taiwan)
was attached to the OLED substrate. A reflective polarizer film, dual BEF (DBEF)
(VikuitiTM 3M DBEF-D400, USA), was attached to the BEF. The integrated light source
was then attached to the prism with an index-matching oil having an RI of 1.515 (Nikon,
Japan). A polydimethylsiloxane (PDMS) flow cell was placed above the metal sensing
films. A collimator was placed on the angle side of the prism opposite the side with the
light source to collect the reflected light and limit the optimum incidence angle light;
thereafter a fiber optic waveguide transmitted the light to a spectrometer (STS-VIS-NIR,
Ocean Optics, USA). Finally, the SPR data was stored in a computer for analysis. The
preference of STS spectrometer is due to the miniaturized size; however, the SNR
performance in every pixel is very large ~1500:1, which is suitable for this study.
The SPR signal was analyzed using the sum of differential reflected light
intensities 20 nm below and above the SPR signal wavelength dip position. The sum of
differential intensities A and B determines the SPR signal A + B that is used to improve the
signal-to-noise ratio (SNR)[23,32].
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2.4 Biochemical materials and preparation
A SAM of 11-mercaptoundecanoic acid (11-MUA) and 3-mercapto-1-propanol (3-MOH)
was obtained from Sigma-Aldrich (St. Louis, MO, USA). An immobilization buffer (10
mM sodium acetate, pH 5.0) and an amine coupling kit containing N-hydroxysuccinimide
(NHS), 1-ethyl-3-(3-dimethylaminopropyl)-carbodiimide hydrochloride (EDC), and a
blocking reagent 1.0 M ethanolamine-HCl of pH 8.5 (ETH) were purchased from GE
Healthcare Bio-Sciences AB (Uppsala, Sweden). The capture antibody and the target
sample using a goat anti-mouse IgG and a mouse IgG were obtained from Sigma-Aldrich.
A phosphate buffer saline (PBS) tablet was also obtained from Sigma-Aldrich. Before the
biomolecular interaction experiments, the gold metal sensing layer was immersed in a
SAM, consisting of 1 mM of 11-MUA and 9 mM of 3-MOH (mixing ratio 1:1), for 20 h at
room temperature.
3. Result and discussion
The OLED white-spectra have unique characteristics compared to white-spectra
obtained from other solid-state lighting, such as light-emitting diodes (LEDs). OLED
white-spectra such as the one represented in Fig. 1(b), show optimum spectral range
intensities between wavelengths 550 nm and 600 nm, where the resonance of SPs using a
bimetallic composition and optical configuration occur. In this study, the wavelength
resonance is at a 580-nm wavelength. The white OLED has higher intensity in the visible
range spectra compared to the UV range commonly occurring in white LED spectra[4]. In
theory, the UV wavelength range is hard to couple to SPR-based noble metal film (Au or
Ag) at all angles of incidence of light. The ratio of SP eigen frequency (ω) to the plasma
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frequency (ωP) propagating along a metal/medium interface shows saturation around:
med
P =
1
1/ (3)
where εmed is the dielectric constant medium[33]. Therefore, very short
wavelength (or high frequency) light cannot couple to the SP. In our Au/Ag metal sensing
configuration using water as the medium, an incident p-polarized light with wavelength
higher than 500 nm is required to couple resonance wave to the SP.
3.1 Simulation and parameters optimization
In the simulation, the Au/Ag bimetallic layer reached the optimum reflectivity dip
at a thickness of 40 nm of Ag covered by 10 nm of Au, as shown in Fig. 2(a). The metal
structure produced the deepest SPR absorption at an optimum peak for a light source of
wavelength around 580 nm that is also the wavelength peak of the white-spectral OLED
used in this study. An SPR design using a green OLED [23] has also been presented as a
reference for non-optimum intensity coupling to the SP wave in the resonance wavelength.
The optimum metal sensing structure was utilized for further simulations of SPR
parameters and experimental measurements.
3.2 Simulation and measurement results
The reflectivity of p-polarized light utilizing air (n = 1) and water (n = 1.33) as
simulated using the bimetallic sensing layer are plotted in Fig. 2(b) and (c), respectively.
The figures show that, using air as a medium, light absorption due to the resonance of SPs
does not occur at every incident angle. This is because of the low dielectric constant of air;
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therefore, the propagation constant value of SPs (Eq. 1) is not in the resonance condition
with the wave vector of the incident light through the BK7 prism (Eq. 2). In Fig. 2(c), using
water as the dielectric medium, the simulated SPR reflectivity-dip profile can be obtained
at an incident angle between 68° and 77°. In this experimental study, the peak of the
incident light at 580 nm corresponded to the 75° incidence angle that was also the leg side
angle of the prism. Based on the simulation result in Fig. 2(c), the sensor design is
potentially improved using less incident angle (~73°) and higher wavelength light source
(~600 nm); however, in this study the peak wavelength is 580 nm is the main parameter to
be concerned to obtain optimum condition. This result indicates that using the metal
sensing configuration described above, a wavelength of incident light higher than 500 nm
is required to couple SPs in a water medium. This limitation is due to the saturation value
of (ω/ωP) as described in Eq. 3.
Figure 3 (a) shows the measurement results of the SPR reflectivity-dip profiles of
pure water and sucrose aqueous solution with refractive indices of 1.333 and 1.337,
respectively. The resonance coupling of SPs in visible light is stronger at higher
wavelengths, and the reflectivity profile shift is slightly larger at wavelengths larger than
the initial reflectivity dip (Fig. 3(a)). To accommodate this asymmetrical reflectivity profile,
the SPR signal calculation method A+B[23,34] was utilized; i.e., wavelengths of ~20 nm
on both sides of the reflectivity dip contribute to the calculated SPR signal to improve the
SNR. In this measurement, the reflectivity dip occurred at a wavelength of ~580 nm.
Therefore, differential signals A and B are calculated at 560-nm and 600-m wavelengths,
respectively. Using this methodology, we take and advantages from low cost and
miniaturized spectrometer device (STS series, Ocean Optics) which has highest SNR
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specification instead of the spectrometer device with high resolution of detector which is
commonly required higher cost. Using this methodology, the measured signal will be very
sensitive to the reflectivity magnitude in the selected wavelength.
The asymmetry in the reflectivity-dip profile, which is the amount of SPR
coupling, is higher at longer wavelengths above the reflectivity dip compared to short
wavelengths below. This can be explained using the Johnson and Rioux model for the
dielectric constant of bimetallic Au/Ag [28,35], where the real part of the dielectric
constant of bimetallic Au/Ag increases drastically around visible range (Fig. 3 (b)).
However, based on Hale and Querry model for dielectric constant water [31], the real
partial value of dielectric constant quite constant as the wavelength increases around the
visible light spectrum (Fig. 3 (b)). This real part of the dielectric constant of bimetallic and
the medium is the primary factor responsible for evanescent light penetration phenomena δ
at the material layer, given by:
Yk
1 (4)
where,
)()(
)(2π2
,
dm
Yε+ε
ε
λ=k
dm (5)
where δ is the evanescent wave penetration depth and εm,d is the dielectric constant
of the metal or the dielectric medium. It implies that the δ of light is stronger at wavelengths
larger than the reflectivity dip compared to shorter wavelengths. Furthermore, as the
wavenumber increases the evanescent wave penetration inside the medium layers increase
(Fig 3 (b)). In other word, the higher wavelength is more sensitive to response the behavior
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of medium alteration.
The series measurements of SPR sensor sensitivity using different refractive
indices of water are plotted in Fig. 3(c). The white-spectral OLED shows a better slope
compared to the green OLED in an SPR sensor using Au/Ag bimetallic layers. The linearity
in the trends are 99.46% and 98.49% for SPR setups using white and green OLEDs,
respectively. The sensitivity improved from 4073 RIU-1 to 4859 RIU-1 (~19.29%).
Considering noise background of about 0.004, the detection limit of the white OLED SPR
sensor was calculated as ~2.4 × 10-6 RIU in the range of ∆n ~3.6 × 10-3 RIU.
Performance and the state of the art of the SPR sensor using a white OLED in this
article are presented in Table 1 in comparison with previous reports for
references[18,22,24,32,36].
Resolution and LOD are good performance metrics of an SPR sensor. Resolution
is a function of the properties of the optical noise of the SPR response, given by R =
σ/(δY/δn); where (δY/δn) is the sensor sensitivity[37]. The detection limit is a function of
thrice the optical noise blank measurement of the SPR response (3σ0); LOD =
3σ0/(δY/δn)[38]. Consequently, this performance corresponds to a resolution of 8 × 10-7
RIU. These results are comparable to other groups’ reports, indicating that a white OLED is
a promising candidate for optical sensor light sources, particularly for a portable SPR
sensor configuration using this approach.
3.3 Biomolecular interaction results
The SAM surface chemistry was performed for 20 h of immersion prior to the
biomolecular interaction monitoring. The molecular chain of carbon was orderly
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functionalized on the gold surface. 9 mM of 3-MOH was utilized to account for 11-MUA
having a longer chain. The gold surface was observed by atomic force microscopy (AFM),
shown in Fig. 4(a), in the absence and presence of SAM surface chemistry for 20 h. The
SAM enhanced the surface modification, such as the thickness and roughness of the gold
surface. Subsequently, the metal sensing was assembled on the prism, prior to the SPR
signal monitoring of surface activation and antibody immobilization, as depicted in Fig.
4(b). A solution of NHS-EDC mixture was streamed for 17 min to activate the surface
functionalization, with the SPR signal increasing dramatically, followed by an acetate
buffer wash. Later, an antibody of IgG protein was immobilized for 30 min, with the flow
rate around 100 µL/min. The immobilization process was monitored by a gradual
increment in the SPR signal until saturation, followed by an acetate buffer wash to remove
excess antibodies that may not have been immobilized on the SAM (shown by the slight
decrease in the SPR signal). Next, a PBS buffer was streamed to the flow chamber prior to
an ETH blocking process for 15 min. ETH was applied to block the SAM area that may not
have been immobilized well by the antibody; this step was applied to guarantee target
sample interaction on the antibody instead of an unspecific binding signal. Then, a PBS
buffer wash was performed for 5 min prior to the sample measurement in a series
concentration. Figure 4(c) shows the mechanism of surface activation, antibody
immobilization, and target sample interaction.
Measurement of series concentrations of IgG proteins interacting on an antibody is
plotted in Fig. 5. A correlation coefficient (R2) of 99.7% in the response trend line is
obtained. The lowest SPR signal equal to 3σ may be calculated, and the value fitted to the
trend line to estimate the minimum concentration value as the LOD. Accordingly, the LOD
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of the SPR biosensor was calculated as 40.3 pg/mL of the target sample.
4. Conclusion
A compact and portable SPR biosensor for a bimetallic Au/Ag sensing layer using
a white-spectral OLED has been presented that enhanced sensitivity by up to 19.29%
compared to an SPR sensor utilizing a green OLED. Furthermore, surface chemistry
modification of a gold surface and the immobilization of an antibody have been
demonstrated as the real-time monitoring capabilities of the sensor. Finally, the developed
SPR sensor detected the biomolecular interaction of an IgG protein target in different
concentrations and achieved an LOD of ~ 40.3 pg/mL.
Acknowledgement
This research was supported and funded by the Taiwan NSC 10-0232-5B18-2006 and
NRPB 10-0IDP-1008-2.
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Table and table captions
Table 1. Performance of the SPR sensor in this study compared to that in previous reports,
particularly with respect to solid-state light source preference and portability of the apparatus.
No. Configuration Interrogation method Light
source
Sensing layer Performance Ref
1 Kretschmann Incident angle LED array Au monolayer n/a [39]
2 Kretschmann Wavelength White LED Au monolayer LOD : 1.98×10−4 RIU [18]
3 Localized SPR Two λ references White LED Au NP n/a [19]
4 Kretschmann Wavelength LED Teflon-Au Res: 5×10−4 RIU [21]
5 Waveguide Incident angle LED Au monolayer n/a [20]
6 Localized SPR Intensity LED Au NP LOD : 5.6 ng/ml IgG [40]
7 Kretschmann Wavelength OLED Au monolayer LOD 6×10-4 RIU [22]
8 Localized SPR Intensity LED Au NP Res : 10−4 RIU [41]
9 Localized SPR Intensity White LED Au NP LOD : 0.05 µg/mL IgG [42]
10 Gratings SPR Incident angle LED Au Grating Res: 3 ×10-7 RIU [24]
11 Waveguide Wavelength White LED Au monolayer LOD 1.65×10−3 RIU [14]
12 Localized SPR Intensity LED Nanohole array LOD 6×10−4 RIU [43]
13 Waveguide Intensity White LED Au NP LOD 9×10−6 RIU [34]
14 Kretschmann Two λ references White OLED Au LOD 7.8 × 10−6 RIU Initial work [23]
15 Kretschmann Two λ references White OLED Au/Ag LOD 3.2 × 10−6 RIU Prev. work [23]
16 Kretschmann Two λ references White OLED Au/Ag LOD 2.4 × 10−6 RIU This work
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Figures and Captions
(a)
(b)
Fig. 1. (a) Schematic of the integrated portable surface plasmon resonance (SPR) sensor
system (not to scale) using a white organic light-emitting diode (OLED) optically enhanced
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by the brightness enhancement film (BEF) and dual BEF (DBEF) microstructures. (b) The
incident light spectrum from a white OLED with peaks of wavelength of 510 nm and 580
nm, respectively. Visible range wavelengths are shown on the x-axes for a vivid illustration
while the inset depicts the white OLED used in this study.
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(a)
(b)
19
(c)
Fig. 2. Reflectivity-dip profile simulation of the film optimization using water as a medium.
(a) Ag-layer optimization for bimetallic sensing composition covered with 10 nm of Au.
Surface plasmon resonance (SPR) reflectivity profiles of the Au/Ag sensing film at several
incident angles and wavelengths using, (b) air and (c) water as the medium of
measurement.
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(a)
(b)
21
(c)
Fig. 3. (a) Reflectivity-dip profile of the portable surface plasmon resonance (SPR) sensor
utilizing a bimetallic Au/Ag sensing layer. (b) Real part ε (left axis) of water and bimetallic
Au/Ag and its correlation to analytical calculation of evanescent wave penetration depth δ
into materials (right axis) along wavelength numbers. Au/Ag ε is got from Rioux model
[35]. (c) Variation of the SPR sensor sensitivity with the refractive index. Simulation
results and experimental data for a green organic light-emitting diode (OLED) are shown
for comparison.
22
(a)
(b)
Fig. 4
23
Fig. 4. (a) Atomic force microscopy (AFM) measurements of the self-assembled
monolayer (SAM) enhancement in the gold surface deposited over the Ag layer. (b)
Real-time monitoring of the chemical treatment and captured antibody immobilization
process on the gold cover layer modified by a surface chemistry activation process. (c)
Mechanism of the chemical surface treatment and biomolecular interaction with the gold
layer surface.
24
Fig. 5. Surface plasmon resonance (SPR) signal response on the bimetallic sensing layer as
the quantity of the target sample of IgG protein is increased.
25
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Authors Biography
Briliant Adhi Prabowo is pursuing a Doctorate degree in the Department of Electronics
Engineering at Chang Gung University, Taiwan. Currently, he is researching topics related
to organic electro-optical devices and biosensors.
Ying-Feng Chang received his Ph.D. from the Institute of Biophotonics, National Yang
Ming University, Taipei, Taiwan in 2011. His research focuses on the establishment of an
ultra-sensitive biosensor based on metal-enhanced fluorescence and SPR.
Li-Chen Su received her Ph.D. from National Central University, Taiwan. She is a
postdoctoral fellow in the Biophotonics group, Chang Gung University. Her research
interests are related to optical biosensors and photonic devices.
Hsin-Chih Lai is a professor and director of Department of Medical Biotechnology and
Laboratory Science in Chang Gung University, Taoyuan, Taiwan. His expertise is in the
areas of infection, inflammation, and molecular immunology.
Nan-Fu Chiu is an assistant professor at the Institute of Electro-Optical Science and
Technology, National Taiwan Normal University, Taiwan. His current research is related
to the optoelectronic devices and biosensor related fields.
Kou-Chen Liu is a professor and department head of Electronics at Chang Gung
University, Taoyuan, Taiwan. His expertise is in the areas of optoelectronics and organic
electro-optical devices.