Smart Glucose Monitoring System using MEMS
Glucose Sensor
A MINI PROJECT REPORT
Submitted by
BLESSING BENZER.B.S (3122224004002)
M.E.VLSI DESIGN
DEPARTMENT OF ELECTRONICS AND COMMUNICATION
ENGINEERING
SSN COLLEGE OF ENGINEERING CHENNAI
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ABSTRACT
Glucose molecules are detected in blood using a MEMS sensor
and the extent of glucose present is analyzed. This design consists of a strip coated
with the opposite dehydrating agent of the glucose and an electrode which is
polarized when the battery is switched on. When a blood drop is placed on the
strip, the glucose reacts with the dehydrating agent and forms chemical
by-products and electrons, which are driven to the electrode which is polarized by
the battery power. Virtualization of the concept on Comsol Multiphysics tool is
used to establish a relation between current and glucose concentration based on the
obtained result.
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TABLE OF CONTENTS
CHAPTER NO.
TITLE
PAGE NO.
ABSTRACT
2
1
INTRODUCTION
4
2
ELECTROCHEMICAL
5
PRINCIPLE
3
WORKING OF SENSOR
6
4
MODELING CONCEPT
7
5
SIMULATION OUTPUT
8
5
RESULT AND DISCUSSION
9
6
CONCLUSION
10
7
REFERENCE
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3
1.INTRODUCTION
​
Glucose sensing is one of the most widespread and commercially
successful uses of electroanalysis. In an electrochemical glucose sensor, the
concentration of glucose in a sample is measured using amperometry; that is, the
measurement of an electric current. An applied voltage causes the oxidation of
glucose, and the current due to this oxidation is measured at the electrode. In a
well designed glucose sensor, there is a linear relationship between the glucose
concentration and the current, enabling a calibrated measurement. Typically, the
oxidation of glucose does not occur directly at the working electrode where current
is measured. Instead, the reaction is accomplished by a chemical oxidant and
accelerated by a biological enzyme such as glucose oxidase (GOx), which makes
the sensor specific to glucose and independent of the concentration of other
oxidizable species that may be present in the analyte solution. The reduced form of
the oxidant, after its reaction with glucose, can be re-oxidized directly at the
electrode. In nature, the oxidant is oxygen, but this suffers from slow kinetics and
the rate of oxidation is perturbed by the oxygen concentration dissolved from the
atmosphere into the analyte solution. Instead an inorganic oxidant with fast
electrode kinetics, such as the hexacyanoferrate (III) anion (commonly,
“ferricyanide”), is suitable for use in a glucose sensor, since the measured current
is made independent of oxygen concentration and is not limited by slow electrode
kinetics (Ref. 1). This example demonstrates a steady-state analysis of the current
drawn in a unit cell of solution above an interdigitated electrode, where the counter
electrode reacts ferricyanide to ferrocyanide. The linearity of the response of the
sensor is demonstrated for a typical range of glucose concentrations. Model
Definition The model contains a single 2D domain.
​
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2.ELECTROCHEMICAL PRINCIPLE
​
In this method we are sensing the glucose levels by using electro
analysis. In this method we design a gluco-strip with certain geometry. When a
certain voltage is provided to this strip and add an oxidizing agent to the glucose
then a certain number of electrons are released due to the oxidation of glucose.
Based on the
​
amount of electrons evolved the current obtained is measured. Now depending on
the current measurement glucose extent in the blood is predicted.
​
​
Glucose + ferri + e- ↔ products + Ferro
​
Here we use ferricyanide as an oxidizing agent to accelerate the reaction. The
voltage required for this strip is provided by the battery cell provided in the device
that is used to measure the strip. When the device is switched on and the strip is
inserted into it then the voltage from the battery is provided to the strip and
initiates the oxidization. Actually when the voltage is given then the strip part is
polarized and separated into two different electrodes one as anode and other as
cathode. This design is done in the electrochemistry module of the model builder
in COMSOL MULTIPHYSICS. When the oxidation is done all the electrons are
collected at one electrode and the other electrode is empty. Then by using
thedevice we measure the current at the electrode in amperes and analyze the
glucose concentration based on the amount of amperes of current evolved. MEMS
innovation holds the possibility to permit coordinated implantable sensors for
metabolic observing. Continuous glucose monitoring (CGM) sensors based on
affinity detection are desirable for long-term and stable glucose model
The rate of this reaction (milliMol/m3 or (mMol/L)) is given by a
Michaelis–Menten rate law as
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​
Here, the parameter Vmax is the maximum rate of the enzyme-catalyzed reaction,
depending on the quantity of enzyme available, here Km is Michaelis-Menten
coefficient. At large glucose concentration, the rate becomes independent of the
glucose concentration and solely depends on the enzyme kinetics. The current
density for this reaction is given by the electroanalytical Butler–Volmer equation
for an oxidation:
​
in which k0 is the heterogeneous rate constant of the reaction, αc is the cathodic
transfer coefficient, and η is the over potential at the working electrode.
3.WORKING OF GLUCOSE SENSOR
The glucose sensor determines the concentration of glucose in the
solution.Most glucose sensor are based on electrochemical technology, they use
electrochemical test strips to perform the measurement. A small drop of the
solution to tested is placed on a disposable test strip that the glucose sensor uses
for the glucose measurement.Glucose sensor consist of two types of electrode
Figure 1:Glucose Sensor
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Reference electrode: Held at a constant voltage with respect to the working
electrode to push the desired chemical reactions.
Counter electrode: Supplies current to the working electrode. Most of the glucose
meter designs use only two electrodes, reference electrode and working electrode.
4.MODELLING CONCEPT
The model contains a single 2D domain representing a 100 μm-wide
unit cell of solution above an interdigitated electrode (Figure 1). The real geometry
is a periodic repetition of this unit cell in the x direction. The cell and electrode are
assumed to extend sufficiently far out-of-plane of the model that the 2D
approximation is suitable. At the top of the unit cell is a bulk boundary where the
concentrations are assumed to equal those in the bulk solution of the analyte. At
the bottom of the unit cell, the y = 0 axis is divided by four points into separate
electrode and insulator boundaries. The anode (working electrode) is at the center
of the cell in the range 37.5 μm < x < 62.5 μm. The 3 | GLUCOSE SENSOR unit
cell contains half of each of the two neighboring cathodes (counter electrodes) in
the ranges x < 12.5 μm and x > 87.5 μm. Between the anode and cathode surfaces,
a solid insulating material is present.
Figure2:Modeling of Glucose Sensor
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This is the rectangular strip designed in the Comsol Multiphysics tool. This
modeling is done in the electro analysis part by selecting a rectangular strip with
certain dimension. Then provide the necessary parameters and required equations.
Later design for the cathode and anode part at the bottom of the rectangular strip.
The orange-red part indicates the electrode cloud region.And an insulation is
created between cathode and anode regions. The width of cathode ,anode and
insulation are varied for different models
5.SIMULATION OUTPUT
Figure 3:Module 100μm*1000μm dimension
Figure 4:Module 50μm*750μm dimension
Figure 5:Module 50μm*1500μm dimension
Figure 6:Module 50μm*1500μm dimension
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Figure 6:Module 160μm*1000μm *10μm dimension
6. RESULTS AND DISCUSSION
Table 1
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From the above result analysis extracted into the table Figure 3 and 4 are linear up
to 6 mMol/L only, from 6-10 mMol/L it doesn’t show the linearity. Similarly
figure 6 is linear up to 4mMol/L and later on from 4-10mMol/L it doesn’t obey
linearity. When there is no perfect linear relationship between glucose
concentration and current exactly we cannot asses the glucose extent of a person.
But in figure 5 module has the best range of current and completely linear.so
glucose concentration can be more accurately estimated from this module since it
is perfectly linear. Though figure 5 also has perfect linearity its current range is
smaller than that of figure 5 module. The more the range the more the accuracy in
prediction of the glucose
6.CONCLUSION
The enzymes responsible for the oxidation of glucose molecules are
studied and finally designed different models for the glucose-strip to respond and
determine different glucose levels and chosen the best model among them to have
a perfect linearity relationship between current in amperes and concentration of
glucose. By this we can estimate the glucose levels of a person either before or
after fasting based on the ampere reading that we get from the current reading.
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7.REFERENCE
•Shameem, S., Krishna, D. V., Kumar, K. S., & Avinash, K. (2018). Design Of
MEMS Sensor For The Detection Of Diabetes. 2018 3rd International Conference
on Inventive Computation Technologies (ICICT).
doi:10.1109/icict43934.2018.9034268
•https://ieeexplore.ieee.org/abstract/document/9034268
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