APL: L14-11037R
Supplementary materials
Complex Permittivity Characterization of Serum with an Air-Bridge
Enhanced Capacitor for Quantifiable Detection of Glucose
Rajendra Dhakal1, a), Cong. Wang1, Eun-Seong Kim1 and Nam-Young Kim1, b)
1
RFIC Centre, Department of Electronic Engineering, Kwangwoon University, Seoul 139-
701, South Korea
FIG. S1. Schematic of the RF detection technique by vector network analyzer (Agilent 8510C).
1
FIG. S2. Regression analysis of the real sample of serum for different experiment time. The generated
result for the experiment time interval of 40 sec shows a maximum shift. The response quality degrades
as the experiment times increased to 160 sec.
FIG. S3. Equivalent circuit model of the fabricated IPD glucose sensor.
2
(a)
(b)
FIG. S4. Measurement results showing (a) the [Real {εr (ω)}] and [Imag{εr (ω)}] part of complex
permittivity variation with different glucose concentration level. (b) The magnitude of εr (ω) obtained by
the numerical formulation.
3
(a)
(b)
FIG. S5. The measurement illustration of D-glucose solution for (a) the microwave transmission
coefficient with different concentration of glucose level (n = 10). The bare resonance frequency at 7.37
GHz, 7.35 ± 0.20% GHz at 25 mg/dl, 7.27 ± 0.21% GHz at 50 mg/dl, 7.21 ± 0.21% GHz at 75 mg/dl,
7.15 ± 0.14% GHz at 100 mg/dl, 7.08 ± 0.21% GHz at 125 mg/dl, 7.01 ± 0.21% GHz at 150 mg/dl,
6.93 ± 0.14% GHz at 175 mg/dl, 6.85 ± 0.23% GHz at 200 mg/dl, 6.78 ± 0.22% GHz at 225 mg/dl, 6.71
± 0.15% at 250 mg/dl. (b) The regression analysis with standard error bar for n = 10 at various
concentration of the D-glucose level. The standard sample of deionized water glucose solution possesses
slightly different characteristic features to the real sample of serum. Because of this inconsistency
4
between the standard and real sample, we obtained a slightly different calibration equation for the real
sample of serum and D-glucose solution, but the nature of the calibration curve and shift in the
resonance frequency coincide with the real sample. We used the standard sample of D-glucose to model
and monitor the trend of resonance characteristics for a relative shift in the resonance frequency for
different glucose concentrations in order to verify the finding obtained from the real sample of the
serum. The obtained measurement results for the D-glucose solution validate the proposed concept of
glucose level detection with excellent detection capability having a minimum detection limit as small as
10.22 mg/dl.
FIG. S6. Scattering plot of the serum sample for 30 different experiment process with different glucose
concentration. The observed data show no overlapping of the resonance frequency among the different
concentrations for different sets of the experiment. The reproducibility of the biosensor was
characterized by measuring the resonance frequency before and after the use of serum. We performed
three different sets of experiments for each concentration of serum to observe the resonance frequency
for each-iteration loop of the experiment. A total of 30 different experiments for a sample of the serum
was tested and represented by the scatter plot. No device response deterioration was observed over this
long iteration of the measurement process. As a result, the relative standard deviation (RSD) of less than
1% was observed for each concentration of serum samples. This observation validates that the proposed
device can reproduce the same experiment result for particular concentrations over different iteration of
the experiments. The bare resonance frequency from each set of experiments after rinsing was obtained
at 7.37 GHz, which confirms the stability and reusability of the system.
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Table S1
The performance of the different measurement parameters for the serum sample having the base glucose
concentration of 65 mg/dl.
a
S.N
Human serum
b
e
Con.
Resonance frequency (GHz)
RSD
st
nd
rd
c
d
(mg/dl) 1 Test
(%)
2 Test
3 Test
Mean
Mean ± RSD ( fav)
1
245
6.82
6.83
6.84
6.83
6.83 ± 0.14%
0.14
2
225
6.88
6.9
6.87
6.88
6.88 ± 0.22%
0.22
3
205
6.94
6.95
6.93
6.94
6.94 ± 0.14%
0.14
4
185
7
7.01
7.02
7.01
7.01 ± 0.14%
0.14
5
165
7.07
7.09
7.07
7.07
7.07 ± 0.16%
0.16
6
145
7.12
7.11
7.13
7.12
7.12 ± 0.14%
0.14
7
125
7.18
7.16
7.17
7.17
7.17 ± 0.14%
0.14
8
105
7.23
7.22
7.24
7.23
7.23 ± 0.13%
0.13
9
85
7.28
7.26
7.28
7.27
7.27 ± 0.15%
0.15
10
65
7.33
7.32
7.31
7.32
7.32 ± 0.13%
0.13
11 Bare Test
7.37
7.37
7.37
7.37
7.37 ± 0%
0
a
S.N denotes serial number.
b
Con. denotes the glucose concentration.
c
Mean denotes the average of the three experiments.
d
fav denotes final average resonance frequency.
e
RSD denotes the relative standard deviation.
Table S2
The performance of the different measurement parameters for the D-glucose sample having the base
glucose concentration of 25 mg/dl.
a
S.N
D-glucose
b
e
Con.
Resonance frequency (GHz)
RSD
st
nd
rd
c
d
(mg/dl) 1 Test
(%)
2 Test
3 Test
Mean Mean ± RSD ( fav)
1
250
6.71
6.73
6.72
6.72
6.72 ± 0.15%
0.15
2
225
6.78
6.8
6.77
6.78
6.78 ± 0.22%
0.22
3
200
6.85
6.87
6.84
6.85
6.85 ± 0.23%
0.23
4
175
6.93
6.92
6.91
6.92
6.92 ± 0.14%
0.14
5
150
7.01
7.03
7
7.01
7.01 ± 0.21%
0.21
6
125
7.08
7.09
7.06
7.07
7.07 ± 0.21%
0.21
7
100
7.15
7.14
7.16
7.15
7.15 ± 0.14%
0.14
8
75
7.21
7.2
7.23
7.21
7.21 ± 0.21%
0.21
9
50
7.27
7.25
7.28
7.26
7.26 ± 0.21%
0.21
10
25
7.35
7.33
7.32
7.33
7.33 ± 0.20%
0.20
11 Bare Test
7.37
7.37
7.37
7.37
7.37 ± 0%
0
a
S.N denotes serial number.
b
Con. denotes the glucose concentration.
c
Mean denotes the average of the three experiments.
d
fav denotes final average resonance frequency.
e
RSD denotes the relative standard deviation.
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Table S3
Comparative performance of the proposed IPD glucose sensor with previously reported articles.
Literature
28
Proposed method
Forster resonance
energy transfer (FRET)
29
Impedance
spectroscopy
30
Magnetic acoustic
resonance sensor
(MARS)
This work IPD based RF
resonator on GaAs
substrate by
characterization of
complex permittivity
Advantages
Reversibility
Implanted sensor
Disadvantages
LOD (mg/dl)
Long assay time
25
(15 min), high LOD
Complex process,
12.02
high LOD
Invasive, high LOD
36.36
Short assay time,
highly sensitive
reusability, mediator
free detection
High production
cost and low
running cost via
reusability
Sensitive
9.69
Table S4
Demonstrating the effect of fructose in the glucose concentration for the blood serum samples.
#
Sample
Glucose
Glucose concentration
Added
Glucose concentration
concentration
determines, before the
fructose determines, after the addition
(mg/dl)
addition of fructose with RSD (mg/dl)
of fructose with RSD
(mg/dl)
(mg/mL)
±RSD%
±RSD%
1
105
104.66 ± 0.40
20
104.53 ± 0.48
2
145
147.16 ± 0.85
20
147.33 ± 0.85
3
205
204.33 ± 0.39
20
204.4 ± 0.70
#
Each sample was measured three times.
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