1. Project Identity:

Design of Magnetic Field Concentrators

Week 5 (Feb. 7 ~ Feb. 13, 2010) Report

Due Sunday February 14th

Group D: Mohammedjuned Desai, Areio Hashemi, Koji Hirota, Michael Wong

2. Work Completed

In the sixth week of our senior design we were able to complete several parts that will get us closer to the actual fabrication of the magnets. From last week we were able to learn that mu metal would provide us with better gradients than iron for the core. With this information we came up with a few designs to test using the FEMM software. We were also able to order materials that are essential for the fabrication as well as researching companies for the fabrication as well.

Beginning to run trials on the different angels and shapes of the magnets was an essential part prior tot the fabrication process. From the trials we do know that mu metal gave us a stronger gradient however we still had to find the optimal shape. Along with the shape we also needed to determine how each shape would act with a second metal of the same shape. However, we also had to test the angle at which each magnet was oriented towards one another as well as the distance they are from one another.

By using FEMM we were able to manipulate the parameters of the magnet to have a mu metal core with angled tips. We then used IGOR to plot and compare the magnets by the gradients and also the derivative of the gradient with respect to distance. When using FEMM to run the magnets we would select a point in which we thought would be best for collecting data. From that point we would draw a line down away from the magnet. By having FEMM calculate the different gradients at each distance we were able to numerically see the changes in the values. It is these values that we use to compare the strengths. The basis of where the starting point and ending point of the line has to deal with the parameters of which we would like to have our magnetic tweezers to work at. Ideally the range is 1mm to 5 mm, which is based on the depth of the well that is holding the molecule of interest.

By running FEMM and having IGOR plot the data point of Tesla vs. Distance and the derivative of Tesla with respect to distance vs. Distance we ran the following experimental comparisons:

1.  Comparison of metal properties: A single flat iron core magnet compared to a single flat mu metal core magnet

2.  Comparison of single mu metal core magnets with altering shapes: A flat shaped magnet was compared to an elevated flat shaped magnet an also a angled tip of 60°.

3.  Comparison of flat shaped mu metal magnets: A single magent was compared to double magnets that were also flat shaped. In this case there were two scenarios of the double magnets; one with 1mm distance between the two and one with 3mm.

4.  Comparison of flat shaped mu metal magnets with angeled position: A flat single magnet was compared to double magnets that had towards one another differntyly. The first was the double of flat magnets angeled towards each other at 90° with a distance of 2mm and the second was the same but the two magnets were angled at 180° and a distance of 3mm.

Note: The size of the magnetics are all the exact same with the following parameters:

Coil thickness: 0.25 inches

Core Diameter: 0.25 inches

Magnet Length: 1.5 inches

From the four experiments that were carried out we were able to have detailed plot that would show us the difference in the magnetic pair.

This graph being shown is the comparison of the flat shaped mu metal magnets with a single magnet and double magnets (Experiment 3). This graph is showing the strength of the field, measured in Tesla, and how with distance it changes. The axis length is showing how far from the original point the recording of the gradient is taking place.

From the other experiments we were able to conclude from the graphs that the flat shaped magnets had the strongest gradients. In the graph above, since we do plan on using multiple magnets for the actual device, we can conclude that having the magnets as close as possible to one another would give use the best gradient.

Dr. Vullev has already ordered a mu metal rod that measures in 0.25 inches in diameter and 25 inches in length from an online company called http://www.mumetal.com. Also in doing so we were also able to find a company that does coiling for magnets (http://coilwinder.com/prod01.htm) in a local city. As of now we are waiting on the materials to arrive so that we can begin fabrication.

Thus far we are still on track to accomplish our goal, this is evident from our timeline.

1st Quarter / Goal / Completed
Week 1 / Determine goal and objectives for the project / Yes
Week 2 / Finalize the proposal / Yes
Week 3 / Learn how to use FEMM, building models, producing results etc. / Yes
Week 4 / Begin running magnet models / Yes
Week 5 / Begin discussing and analyzing results / Yes
Week 6 / Complete all the software models and analyzing the results / Yes
Week 7 / Start ordering/gathering parts to begin fabrication / Yes
Week 8 / Begin fabrication
Week 9 / Attach the part to the microscope
Week 10 / Have prototype/design already built
2nd Quarter
Week 1 / Read up and familiarize ourselves with protocol on the calibration of the magnetic tweezers
Week 2 / Being calibration
Week 3 / Proper Placement of Mirrors/Objectives
Week 4 / Finding Linear Region of the gradient field
Week 5 / Focusing Camera for Viewing Bead Movement
Week 6 / Calculating Velocity of Beads from Measured Distance and Time and use Stokes Equation to fine the Force Exerted on the
Week 7 / Begin experimentation
Week 8 / Take data from sample
Week 9 / Compare data with published results
Week 10 / Finalization of the product and calibration

3. Future Work

In the future we will begin the fabrication of the magnet. This includes the actual cutting of the mu metal rod down to the right size and thickness for the tweezers. As far as the coiling process goes we must get into contact with the local company to determine the best coiling for our objective.

4. Project Review

During this past week we did not encounter any setbacks. We were able to determine on a better suited material for the core and began to use that as our basis. The only process that may take some time is having the company access our magnet and determine a optimal coiling process.