Biomagnetic Field Generation

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Biomagnetic Field Generation

• Project 10
• Brett Duncan Tanvi Patel
• ECE 445 Senior Design
• December 1, 2005
• http//www.comsol.com/showroom/gallery/15.php

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Introduction

• Biomagnetics the study of applied magnetic
  fields on living tissue.
• Design and implement a biological research device
  which allows for the application of magnetic
  fields to cell culture chambers

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Relevance

• Allow for the application of magnetic field to
  cell cultures (normal, cancer cells) to determine
  the magnetic field effects on cell growth,
  differentiation and repair.
• Magnetic fields are being used along with
  iron-containing antibodies as an alternative to
  Flow Cytometry for cell sorting and
  identification.

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Objectives

• The overall goal is to create a reliable and
  accurate device which can provide a uniform
  magnetic field throughout a specified volume over
  a culture dish.
• Also, to characterize this field in a way that
  will be useful for studies of cell cultures
  placed inside the magnetic field.

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Features

• Magnetic Field range between 1 and 100 Gauss with
  a resolution of one Gauss.
• User friendly display showing current field
  strength.
• Quick and easy ability to dial in desired
  magnetic field.
• Adaptable to different sized cell culture
  containers.

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Biomagnetic Research Device
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Device Overview
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Device Overview

• Agilent 25 Watt Power Supply
• - Provide 5 Volt for PIC and LCD
• Xantrex 1000 Watt Power Supply
• - Provide 14 Volt and 0 7.2 Amps to Buck
  Converter and Magnetic Chamber

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Buck Converter

• Allows for tunable current supplied to Magnetic
  Chamber for control over magnetic field strength

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Buck Converter
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TL598 Wiring Diagram
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Magnetic Field Chamber

• Generates magnetic field for application to a
  variety of cell culture containers

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Magnetic Field Chamber Schematic
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PIC Microcontroller/LCD

• PIC Microcontroller
• - Receives reference voltage as an input and
  uses a stored calibration equation to calculate
  magnetic field in chamber
• LCD Display
• - Displays calculated magnetic field from PIC
  for the user

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PIC Microcontroller/LCD
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Power Supply Noise Testing

• Vmax 14.438 V
• Vmin 13.578 V
• Max Ripple
• 850 mV

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Noise Effects on Device Performance
Top Left Agilent Power Supply Top Right
Xantrex Power Supply Bottom Left Xantrex Power
Supply after noise reduction
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Device Testing

• Determination of maximum field strength and an
  optimum usable range for the device
• Set device at 100 duty cycle and increased
  supply voltage while monitoring magnetic field
  strength and state of components

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Field Strength and Resolution Testing

• Maximum field strength of 177 Gauss
• Determined a usable range of 0 to 100 Gauss with
  a resolution of one Gauss

Voltage V Current A Mag Field Gauss
10 5.2 72
11 5.7 79
12 6.2 86
14 7.2 100
16 8.1 113
17 8.6 120
18 9.1 127
20 10.0 141
21 10.5 147
22 11.0 154
23 11.4 160
24 11.7 164
25 12.2 170
26 12.6 177
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Magnetic Field Strength vs. Current Measurement

• Vary the duty cycle of the Buck Converter to
  determine field strength vs. current
• Compare results versus theoretical calculation

N
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Magnetic Field Strength vs. Current Measurement
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Calibration Curve

• Varying the duty cycle corresponds with
• A change in Magnetic Field Strength
• A change in current through the sensing resistor
• This results in a change in voltage across the
  resistor
• Therefore a voltage across the sensing resistor
  can be related to a field strength
• A calibration curve was established using these 2
  parameters

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Magnetic Field Characterization

• An x,y,z,coordinate system was defined
• 10 x 16 cm stage area
• 4 cm above and below stage
• Measurements of Magnetic field strength were
  taken throughout the stage area in two cm
  intervals

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Magnetic Field Characterization Plots
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Successes

• Usable range of 0-100 Gauss Magnetic Field with 1
  Gauss resolution
• Uniform Magnetic Field of 30 cm3
• Magnetic Field Strength Displayed within 1.8
  accuracy of exterior magnetometer

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Challenges

• Linear Amplifier circuit unable to handle large
  power dissipation
• Power dissipation considerations with components,
  heatsinks, and wiring
• Limitations due to high currents
• Magnetic Chamber Construction
• Mathematical limitations with PIC

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Recommendations

• Current Design
• Use of a PIC with advanced math functions
• Less noisy power supply
• Use of Custom printed circuit boards

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Recommendations

• To achieve 1000 Gauss field
• Power Dissipation Considerations
• Minimize MOSFET RDS(on)
• Minimize Diode Vf
• Larger heatsinks, cooling fans
• Magnetic Chamber Design
• Switch to magnetic wire
• Increase wire size
• Cooling for coils

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Summary

• We successfully created a variable magnetic
  chamber for biological research
• Applicability determined by research demands for
• Cancer research
• Normal cell healing and growth
• Cell sorting and identification

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Credits

• Professor Ray Fish
• Professor Jonathan Kimball

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Questions?