Design of Magnetic Field Concentrators

By: Mohammed Zuned DesaiKoji Hirota

Michael WongAreio Hashemi

Background

• Magnetic tweezers is a research tool for studying molecular and cellular mechanics

• Commonly used to study force regulated processes in biological systems

• Good resolution through a CCD (charged couple device) camera• Exert no thermal or physical damage

• Functionality:• Ability to measure forces on a particle using a magnetic field

gradient.

• Simplicity:• Simple models consist of a pair of magnets that are placed on top

of the sample holder on an inverted microscope

Over all Purpose

• Design a magnetic tweezers device that is capable of obtaining force measurements up to at least 100 pN

• The tweezers should be designed in a way in that the sample will be able to be imaged using a bright-field transmission microscopy.

Clients

• Universities, Research Institutes, Biotech Companies, Laboratories

• Reason• Device itself must be calibrated before its used, which

implies the person must have some knowledge of the field

• If the customer were to buy all of the components it would be far too expensive for their budget i.e. cameras and microscope

Objectives

• Using FEMM (Finite Element Methods Magnetics) to predict the geometry and alignment of the magnets that will produce the largest possible magnetic field gradient.

• Machine and assemble the designs of four or six magnets that produce the largest field gradients using the FEMM results

• Calibrate the electromagnet assemblies, using procedures previously developed

Methods

Determine the Best Core Size

Determine the Best Coil Size

Determine the Best Shape the Magnet Tip

Determine the Best Alignment of two

Magnets

Determining the Best Design of the

Apparatus

Fabrication of the Apparatus

Calibration of the Apparatus

Using FEMM General Design Proper Placement of Mirrors/Objectives

Order Necessary Parts

Designing and Attaching the Magnet

Tip

Setup Microscope and Bright-Field Transmission

Design and Setup of the Magnets

Setup of Camera and Computer

Finding Linear Region of the Magnetic Fields

Focusing Camera for Viewing Bead

Movement

Calculating Velocity of Beads from

Measured Distance and Time and use Stokes Equation to

fine the Force Exerted on the Beads

Setup Design

Ibrahim UCR Bien June 2009

Design Innovations

1) Angle 2) Arc 3) Cocave Angle

4) Flat

Objective: Obtain design that will produce the largest magnetic field gradient

Sample Results

Objective: Generate fine magnetic field lines

Sample Results

Objective: Look for shape that provides the largest change in magnetic field

Magnet Design

1) Potential Problem2) Experimentations

BudgetComponent Price (US) In Stock

Electromagnetic Magnets $20-$50 each Yes

Magnet Power Supply $200 Yes

Aluminum plate $50-$200 No

Steel Rods (0.5inch diameter)

$50-$100 each No

CCD Camera $1,000-$10,000 Yes

Microscope $30,000-$40,000 Yes

Super paramagnetic beads $100-$500 Yes

Potential Problems

• Machining the conical tip • Fabrications of tip

• Too small, might crack• How glue will affect results• Working with a feasible distance• Angular positioning of magnets• Magnet coil turns• Shipping time of magnets• Calibrations• Budget

Conclusion

• Design magnetic tweezers that can exert as much force as possible, preferable at least 100pN

• Using FEMM to determine the best theoretical model d• Fabricate based on that model• Calibrate to maximize the force output from the instrument

• Remarks:• What makes our project unique from the other designs that are

currently used is that we will be designing it in such a way that it will be compatible for the sample to be imaged using bright field transmission microscopy

• Being able to apply large forces

Can We Do It?

• We believe that we can achieve anything that we set our minds to achieve.

- Anonymous

Questions?

References

• Neuman, Keri C, and Nagy, Attila. “Single-molecule force spectroscopy: optical tweezers, magnetic tweezers and atomic force microscopy.” Nature Publishing Group Vol. 5, NO. 6. June 2008.

• Danilowicz, Claudia, Greefield, Derek and Prentiss, Mara. “Dissociation of Ligand-Receptor Complexes Using Magnetic Tweezers.” Analytical Chemistry Vol. 77, No. 10. 15 May. 2005.

• Humphries; David E., Hong; Seok-Cheol, Cozzarelli; Linda A., Pollard; Martin J., Cozzarelli; Nicholas R. “Hybrid magnet devices fro molecule manipulation and small scale high gradient-field applications”. United States Patent and Trademark Office, An Agency of The United States Department of Commerce. <http://patft.uspto.gov>. January 6, 2009.

• Ibrahim, George; Lu, Jyann-Tyng; Peterson, Katie; Vu, Andrew; Gupta, Dr. Sharad; Vullev, Dr. Valentine. “Magnetic Tweezers for Measuring Forces.” University of California Riverside. Bioengineering Senior Design June 2009.

• Startracks Medical, “Serves Business, Education, Government and Medical Facilities Worldside.” American Solution. Startracks.org, Inc. Copyright 2003. <http://images.google.com/imgres?imgurl=http://www.startracksmedical.com/supplies/invertedmicroscope.jpg&imgrefurl=http://www.startracksmedical.com/supplies.html&usg=__butCY2zWJa7nAkwkjiPxX_mFy0=&h=450&w=450&sz=24&hl=en&start=2&um=1&tbnid=XH6gnQuJLS7bRM:&tbnh=127&tbnw=127&prev=/images%3Fq%3Dinverted%2Bmicroscope%26hl%3Den%26sa%3DN%26um%3D1>