Minh Anh
Thi Nguyen
Class: BIOM
476
Colorado
State University
Email: minhanhnguyen@q.com
Abstract
Gold nanoparticles are a popular area of research with several
medical applications. They can be engineered to target cancerous cells in
procedures such as diagnosis and treatment, and at the same time can be
designed to absorb specific wavelengths of light. Gold nanoparticles (Au NPs)
are small particles composed of gold which have one-, two-, or three-dimensions
on the nano-scale. Gold
nanoparticles' small size allows them to infiltrate almost anywhere, a
characteristic that is perfect for cancer treatment but potentially harmful to
healthy cells. This study was designed to look at how these particles are taken
up by cancer cells. Heating of the cancer cells with a magnetic field weakens
them making them much more disposed to successful treatment with chemotherapy. Computer programs, including the HFSS and
the MAXWELL have been to plot the magnetic field and electric field strength
for a parallel capacitor plate and three different types of coils: 1) A heat
exchange solenoid coil with an open core inside the Cu coil and with a slot for
a bottle; 2) a solenoid coil with a closed core inside the Cu coil and with a
slot for a bottle; 3) a sheet solenoid coil.
The simulation results were collected at the radio frequency 13.15 MHz
and provided useful insights for understanding the process of heat transfer
between the particle and the surrounding medium. The simulation results of
magnetic field and electric field strength were plotted and compared with an
actual field strength measurement. The B-field
measurements are very similar to results B-field simulations using the HFSS
program.
Background
Electric
currents produce magnetic fields. The magnetic field has magnitude and
direction. The direction is determined by the direction that a compass will
point. The magnitude is determined by
the size and location of the electric currents that produce the magnetic field.
The simplest way to create a uniform magnetic field is to run a current through
a solenoid, which is a coil of wire designed to create
a strong magnetic field inside the coil.
For a solenoid of N turns and length L, carrying a current
I; the number of turns/length is n = N/L [1].
By wrapping the same wire many times around a cylinder, the magnetic field due
to the wires can become quite strong. The number of turns N
refers to the number of loops the solenoid has. More loops will have a stronger
magnetic field. The formula for the field inside the solenoid is
In addition, if a solenoid has many
turns, the magnetic flux density “B” within the coil is nearly uniform,
while the magnetic
field outside is close to zero; similar to that of a bar magnet [7]. The
B-field within the coil can be calculated from Ampere’s Law. More turns means larger coils, lower
self-resonance and higher copper loss. As
a result, solenoids have an enormous number of practical applications.
In medical applications, nanotechnology is among the most popular areas of research into new
detection methods that should bring cheaper, faster and less painful and
harmful diagnoses and treatments. However, for diagnostic
testing and cancer treatment, gold nanoparticles are a popular choice for
medical research. Gold nanoparticles (Au NPs) are small
particles composed of gold which have one-, two-, or three-dimensions on the
nano-scale. Gold
nanoparticles' small size allows them to infiltrate almost anywhere, a
characteristic that is perfect for cancer treatment but potentially harmful to
healthy cells. Gold nanoparticles also have physical
properties such as optical, electronic, and molecular-recognition
characteristics, as well as biocompatibility, which make them useful across a
range of applications. Gold
nanoparticles can be engineered to target cancerous cells in procedures such as
diagnosis and treatment, and at the same time can be designed to absorb
specific wavelengths of light. Gold nanoparticles were designed to help tissue
heating by the radio waves. Heating of the cancer cells with a magnetic
field weakens them making them much more disposed to successful treatment with
chemotherapy. [3, 5, 6,8]
Remarkably it appears
that gold nanoparticles heated by exposure to radiofrequency (RF) fields could
help destroy pancreatic tumors. The aim
of this study is to understand the physical processes or experimental pathways
for the observed heating characteristics of these particles at specified radio
frequencies (13.56 MHz). The study of
the physical basis of gold nanoparticle heating will involve examining the
capacitive RF heating properties of gold nanoparticles with respect to their
volume fraction and diameter. The analysis plans contained herein provide
critical insights into how the physical properties of gold nanoparticles
influence their RF thermal delivery, which will aid in the further development
of nano-scale materials for the treatment of cancer. In a biological medium, NPs may interact with
bio-molecules such as proteins, nucleic acids, lipids and even biological
metabolites due to their nano-size and large surface-to-mass ratio. Published information shows that
nanoparticles currently have been applied in diagnostics, imaging, and
therapeutics in biology and medicine [5, 6].
This report presents results for designing and simulating the E-field
and the H-field for a parallel capacitor plate and three different types of
coils: 1) a heat exchange solenoid coil with an open core inside the Cu coil
and with a slot for a bottle: 2) a solenoid coil with a closed core inside the
Cu coil and with a slot for a bottle: 3) a sheet solenoid coil. These simulation results were collected at
the radio frequency 13.15 MHz, and provided useful insights for understanding
the process of heat transfer between the particle and the surrounding medium. All simulation data will be collected to
prove that the simulations work. If the experiments and tests in the lab are
not successful, then the test data will help us investigate and understand the
root cause of the failures
Methods:
Modeling and simulating of coils
Since submitting my
proposal, I have spent most of my time designing, simulating, calculating and
plotting the E-field, H-field and B-field for three different types of coils
and one parallel capacitor plate. The first
step was to define the materials which would be used to simulate the
coils. Materials are very important in
this project, because different material will give completely different results
for E-field and H-field measurements.
The next step was to use MathCAD software to calculate the inner and
outer radius of the glass bottle or test tube, the inner and outer radius of
the coil, and the length of the coil.
This calculation must be correct; otherwise it is very difficult to
design the coil on the HFSS 15 software.
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For the solenoid coil with open core in
inside the Cu coil and with a slot for the glass bottle, I used the MATHCAD
tool to calculate all the necessary values that I needed to design the heat
transfer solenoid coil. Once I completed
all the set up environment to start the HFSS 15 program. I created a new
project and successfully drew a solenoid coil with all the values that I had
calculated previously and assigned each element with a correct material. Once
the design was completed, I ran the simulation to validate my design and fixed
the few error messages that I found during my simulation. I plotted and
calculated the E-field and the H-field of solenoid coil with open core in
inside the Cu coil, after my design passed validation. The simulation results of the E-field and the
H-field of this coil are shown in Figure 1 through figure 4.
-
I repeated the same process described
above to complete the simulation for the solenoid coil with a close core inside
the Cu coil and with a slot for a glass bottle. The simulation results of the E-field and
the H-field values of this coil are shown in Figures 5 through 6.
-
I applied the same procedure to complete
the simulation for the sheet coil with a slot for a glass bottle inside the
coil and a parallel capacitor plate.
The simulation results of the E-field and the B-field of the sheet coil
are shown in Figures 7 through 9. The
simulation results of the E-field and the B-field of the parallel capacitor
plate are shown in Figures 10 through 11.
Measuring of coils
We used a magnetic
field probe to measure the magnitude and direction of the heat transfer
solenoid coil’s magnetic field within the lab; we kept the probes away from
other magnetic sources like magnets, the computer monitor, and speakers.
Holding the probe and rotating it horizontally and vertically will change the
reading as it changes its alignment with the B-field. The results of the B-field analysis that
we got from the measurements are very similar to the results of B-field
measurements that I got from the simulation using the HFSS program.
It was important to
work closely with Dr. George Collins and Chris Collins on this project, because
I do not know the all materials and geometries which are used to create coils, nor
other factors such as the capacitor plates and bottles, and the temperature of the
water which flows through the coil.
Also, I had no previous experience in measuring electric fields and
magnetic fields (E-field and B-field) from heat exchange coils
Results:
Figure 1: Plotting and calculating result of E-field for the heat
exchange solenoid coil (a solenoid coil with an open core inside the Cu coil
and with a slot for a bottle) using the HFSS program.
Figure 2: Plotting and calculating result of H-field inside
the glass bottle or inside of the solenoid coil with an open core inside the Cu
coil using the HFSS program.
Figure 3: Plotting and calculating result of E-field outside
the glass bottle or outside of the solenoid coil with an open core inside the
Cu coil using the HFSS program.
Figure 4: Plotting and calculating result of H-field outside
the glass bottle or outside of the solenoid coil with an open core inside the
Cu coil using the HFSS program.
Figure 5: Plotting and calculating result of E-field inside
the glass bottle or inside of the solenoid coil with a closed core inside the
Cu coil using the HFSS program.
Figure 6: Plotting and calculating result of H-field inside
the glass bottle or inside of the solenoid coil with a closed core inside the
Cu coil using the HFSS program.
Figure 7: Plotting and calculating result of B-field inside
the glass bottle or inside of the sheet coil with length 15 cm using the
MAXWELL program.
Figure 8: Plotting and calculating result of B-field inside
the glass bottle or inside of the sheet coil with length 45 cm using the
MAXWELL program.
Figure 9: Plotting and calculating result of E-field inside
the glass bottle or inside of the sheet coil with length 45 cm using the
MAXWELL program.
Figure 10: Plotting and calculating result of E-field of the
air parallel capacitor plate using the HFSS program
Figure 11: Plotting and calculating result of B-field of the
air parallel capacitor plate using the HFSS program
Discussion:
A magnetic
field is produced by applying a current and high radio frequency in a copper
wire wound to form solenoids; coils of several closely-space loops were
simulated and studied in this research.
The magnetic field simulation results of solenoid coils are correct;
when there is no current, there is no magnetic field because there is no current
to carry a number of free positive charges through ten rings. When there is a current, charges will spin in
a counterclockwise direction. Once the
charges on the ring start to accelerate, a magnetic field develops in the space
between the rings. The magnetic field created by each turn of the
solenoid adds up cumulatively, giving a stronger magnetic field inside the
solenoid than outside it (as shown in
figures 2, 4 and 6), because the current in each circular turn of the
solenoid flows in the same direction. The strength of magnetic field created by a current carrying solenoid
is: 1) directly proportional to the number of turns in the solenoid: 2)
directly proportional to the strength of current in the solenoid; and 3)
dependent on the nature of "core material" used in making the
solenoid.
According to the Faraday’s law of induction,
as the magnetic flux through exclusively 10 rings grows, there is an electric
field created by the time-changing magnetic field. The electric field flows in an opposite to
the direction of the currents which are trying to spin the rings. If there is charge, then work must be
occurring to spin the charges. This is the source of the energy which develops
in the magnetic field between the rings.
There is air in the coil, magnetic
field can be calculated by using this formula B = μ0H, where
μ0 is the permeability of free space. In my simulation, the
permeability of free space value is 1 H/m.
The integral is equal to zero because no current passes through the plate. The magnetic fields are created by the current and time varying electric fields, therefore the magnetic fields of the parallel capacitor is also zero. As shown in figure 11, the results of model for the B-field of the parallel plate capacitor that I got from the simulation using the HFSS program are very similar to the B-field values that I got from the Ampere’s Law calculation. As the capacitor charges, an electric field develops between the two plates; this charge can be calculated by using the formula,
where Ɛ is the relative dielectric constant. In my simulation Ɛ is replaced with Ɛ0 because it represents air or vacuum.
Figure 14 shows some of the coil configurations that were made in our
lab. All the coils are hands -twisted and made from copper wire materials. All
length dimensions are in mms and they have are identically measurements and
structures, which were used in the simulations, via the HFSS and MAXWELL
programs.
Conclusions
Computer programs are designed in HFSS and MAXWELL to plot the magnetic
field and electric field strength for different types of coils and a parallel
capacitor plate. The calculated results of magnetic field and electric field
strengths are plotted and compared with actual measurements. The results of the B-field analyses that we
got from the measurements are very similar to the B-field values that I got
from the simulation using the HFSS program. The magnetic field and Electric
field of solenoid coils are important in many scientific applications and other
particle accelerators. Problems & Solutions
Time Constraints
Time was an issue in getting all the
different tasks completed in this project, especially since the total time
given for completing the class 476A (2 credits course) is 77 hours. The minimum amount of time required just
for running a simulation and debugging error messages for three coils and one
parallel capacitor plate would be more than 50 hours.
Project software
In order to complete
my tasks on schedule, I have to resolve five major issues:
-
The
first issue that I encountered on February18, 2014 was unable to draw a helix
model in 3D using the HFSS program. To
resolve this problem, I contacted the ENS helpdesk to explain a problem and get
help in resolving the issue of being unable to draw a helix model in 3D using
the HFSS program. I submitted a help
ticket so that the ENS team can fix the problem. The total time that I spent to resolve this
issue is 2 hours.
-
The
second issue that I encountered lab time.
The simulation to calculate the E-field and the H-field have required
more than 8 hours to complete, but there is no computer which is dedicated for
this simulation. I have to kill my
simulations every time a computer is needed for other engineering lab classes.
This problem had waste so many hours of my time.
-
The
third issue occurred because CSU did not update the HFSS software and HFSS
license in all the engineering lab rooms.
I got this error message “"U:\Documents\Ansoft is not a valid
directory because it is a read only" when I tried to open the program or
any of the project files. I tried and was unable to resolve the error
message. I contacted the ENS help desk
office to explain the error messages that I received during spring break
weekend (3/23/2014). I submitted a
ticket to request help so that ENS‘s team could investigate the problem. This
problem caused 3 hours of my time to resolve.
-
The fourth
issue was disk space as shown in figure 12. On March 24, 2014, I spent 2 hours
to work with ENS’s team to resolve another error message that I received during
my simulation. This time, the error
message occurred due to a disk space issue.
To resolve this problem temporarily, I had to delete all the files in
the U-drive and I did not save my all simulation results for E-field and
H-field models. 1GB is the total amount of disk space in the U-drive which the
school provided to each engineering student.
-
The last
issue was B-field option is not available in the HFSS software (Figure 13). To
resolve this issue, I contacted the ENS help desk office to explain the problem
and show them that the B-field option is not available in the HFSS software. I
submitted a ticket to request help so ENS’s team can investigate the problem.
The problem is solved; B-field values can calculated and plotted by using the
MAXWELL program
Figure 12: The error message which occurred due to a disk space issue
Figure
13: Evidence which shows that the B-field option is not available in the
HFSS software
Future works:
There are many ways to measure steady magnetic
fields. The common method uses a Hall
Effect probe to sense the magnetic field, which is not experiment or perform in
this study. The Hall Effect is ideal as
a magnetic sensor because of the linearity between Hall voltage and magnetic
field at the side of the probe.
MATLAB is another program which can be used to
simulate the B-field, H-field and E-field.
This program is not used to calculate and plot B-field, H-field and
E-field in this research; therefore, it is a good suggestion for future
work. The simulation results from the
MATLAB can be compared with the results of the B-field analyses that we got from the actual
measurements and the simulation using the HFSS program.
Researchers will not see the full and complete picture if they can only
analyze their particles using one frequency value 13.15 MHz, a very common
frequency range capability for induction heaters. Using a wider range of
frequencies allows coils and particles respond at different frequencies and
field strengths. Therefore, different
ranges of frequency could be measure and simulate using the HFSS in the future.
A small coil may pose some
problems. The magnetic field will vary, as for all coils, in the radial and
axial directions. A larger coil has a larger region of homogenous field
strength than a smaller diameter coil. Insulating the sample from the coil in a
small coil may be difficult. A large coil provides space to insert sample
insulation (expanded polystyrene etc.) to insulate the sample from the
surroundings (coil and air). Eliminating the polystyrene insulation could
introduce heating in the sample from the coil or the surrounding environment [8,
9]. Therefore, different
size of the coil could be measure and simulate using the HFSS in the future.
Applications:
Magnetic and electric fields have been used in
a variety of clinical applications which include brain mapping, and treatment
of chronic pain. These
field gradients are generated by coils of wire, usually placed on cylindrical
surfaces, although as will see other geometries can be active [9, 8]. Engineers and designers continue to find new
ways to utilize physics to perform outstanding research and development that
breaks new ground in their fields.
For example, 1) Magnetic Resonance Imaging
(MRI) is
used for imaging the inside of the human body and is based on the use of
well-defined and controlled magnetic fields: A strong uniform static main
field, capable of polarizing the samples. Both the solenoids and the Radio
Frequency coils are used in MRI. Solenoids are used to create a magnetic field
with strength between 0.2 -1.5T, and when MRI uses a magnetic field stronger
than that range, the image will have a higher resolution. Radio Frequency coils are used for
transmitting energy and receiving signals [9, 10, 11]. 2) Cardiac
pacemakers for the treatment of conduction and arrhythmia disorders of the
heart. Magnetic and electric fields stimulator makes currents in the tissue to
achieve magnetic stimulators consume high power and cause significant heat
dissipation in the coil [9].
References
1. Lina,
A. Fadhil J.. "The Magnetic Field Study of a Finite Solenoid." Circuits
and Systems (): 316-322. Print.
2. "Designing
a helical-coil heat exchanger." . N.p., n.d. Web. .
<http://www.gandipsbio.com/Articles/Papers/3_Helical_Coil_Heat%20Exgr_1982.pdf>.
3. Haq,
Am Mujibul. "Use of Gold Nanoparticles in Diagnostics, Surgery and
Medicine: A Review." Bangladesh Journal of Medical Biochemistry: n.
pag. Print.
4. Ansoft
HFSS Fundamentals-Maxwell3D
5. Jacobson,
Joseph M.. "Remote electronic control of DNA hybridization through inductive
coupling to an attached metal nanocrystal antenna." Nature:
152-155. Print.
6. Ackerson,
Christopher J.. "Superatom Paramagnetism Enables Gold Nanocluster Heating
in Applied Radiofrequency Fields." ACS Nano: 2610-2616. Print.
7. "."
. N.p., n.d. Web. 14 May 2014.
<http://personal.tcu.edu/zerda/manual/lab12.pdf>.
8. Ivkov,
Robert. "Method to reduce non-specific tissue heating of small animals in
solenoid coils." International Journal of Hyperthermia: 106-120.
Print.
9. Gale,
John T.. "Microscopic magnetic stimulation of neural tissue." Nature
Communications : 921. Print.
10. "."
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11. Zapolskis,
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Print.
Appendix
Figure 14: Various hand wound coils or inductors fabricated in the Lab
