Transcript Senior Design Final Powerpoint
Team D Mohammed Zuned Desai Areio Barzan Hashemi Koji Hirota Michael James Wong
Magnetic Tweezers
Exerts magnetic forces to determine mechanical properties of molecules, proteins, chemical bonds Advantages The magnet configurations are relatively easy to assemble Magnetic forces are orthogonal to biological interactions Offer the prospect for massively parallel single-molecule measurements Figure 1: Illustration of Magnetic Tweezers, adapted from http://www.nature.com/nature/journal/v421/n6921/images/n ature01405-f2.0.jpg
How do Magnetic Tweezers Work?
Magnet(s) Light Source PDMS Wells Containing Sample 10x Objective Lens Stage layer modified with protein force Mirror Figure 2: Diagram of setup of magnetic tweezers CCD Camera layer modified with ligands Figure 3: Animation of how magnetic tweezers work
How Magnetic Tweezers Work?
What do these forces depend on?
F M
m
B
The force on the paramagnetic beads depend on the F M Force Calculations: F d F g
Magnetic Field Gradient
Magnet • What do we mean by magnetic field gradient ?
• • Want to achieve a high gradient For the same distance we want a constant change in gradient Figure 4: Diagram demonstrating the definition of homogeneous gradient 0.2 mm 0.2 mm 0.2 mm Sample attached to paramagnetic beads B = 800G B = 700G B = 620G B = 560G
Objectives
Main goal is to focus on attaining forces with the Magnetic Tweezers for single-molecule measurements (e.g. 5 – 100 pN): Design producing the highest gradient Achieving force higher than 1.5pN (previous group) Calibrating the selected design Figure 5 and 6: Setup of last years senior design group taken at different angles.
High Magnetic Gradient
To maximize the magnetic gradient Build the stronger magnet(s) with materials Geometry shape and position Using FEMM (Finite Element Method Magnetics) Figure 8: Double Magnet FEMM Design Figure 9: Single Magnet FEMM Design
Single Magnet Design
Using FEMM simulation program Choose the materials Design the core including length, diameter and shape Outcome CORE Steel 127mm (5 in.) core length 6.35mm (0.25 in.) core diameter Flat Shape COIL 30 Gauge Copper wire 2500 coil turns 91.44mm (3.6 in.) coil length 15.49mm (0.61 in.) coil diameter Figure 11: Picture of the magnet (coil and core)
•
Double Magnets Design
From the literature research and FEMM simulation, this design of double magnets should exert higher magnetic gradient Figure 10: Drawing of final double magnet design
Magnetic Tweezers Setup
Single Magnet Double magnets Up to 5.9 pN Up to 3.5 pN Inverse relationship of strength of magnetic field over distance Figure 12: Close up picture of single magnet design Figure 13: Close up picture of double magnet design
Measuring Magnetic Gradient by Gaussmeter
Measure magnetic gradient over distance Graphs to be linear Magnetic gradient is decreasing at a constant rate Compare magnetic gradient within working distance (2mm) Single Magnet: 148.43 G/mm Double Magnet: 120.56 G/mm Figure 14 and 15: Comparison of the gradient results for the single magnet and double magnet
Calibration Process: Setup
Light Source Magnet 1mm Capillary Tube With Paramagnetic Beads Light Source Stage 10x Objective Lens Magnets 1mm Capillary Tube With Paramagnetic Beads Stage 10x Objective Lens CCD Camera Figure 16: Calibration setup for the single magnet CCD Camera Figure 17: Calibration setup for the double magnet
Actual Setup
Adjustable Stage Magnet(s) CCD Camera 10x Objective Lens Sample Stage with Capillary Tube LED Light Source Power Supply Figure 7: Picture of the setup of our final design
Calibration Process 1) Zero apparatus
Have the tip of the magnet close to the capillary tube 2)Inject beads into the capillary tube 3)Turn on the power source 4) Note time it takes for the bead to travel 0.5mm
Light Source Magnet 1mm Capillary Tube With Paramagnetic Beads Stage 10x Objective Lens CCD Camera
Calibrating Magnetic Tweezers
F d F M F g
Force calculations using Stoke’s drag equation:
F
Calibrate:
m
B
Distance between the core of the electromagnet and paramagnetic beads
F d
6
r
F M
Gravitational Force ~ 0.3 pN
F d
F g
force
Example:
Time it takes bead to move vertically 0.5mm = 9.4s
Velocity of bead (v) = 0.054 mm/s Fluid’s viscosity (u)= 3.63 mPa s (40% Glycerol Solution) Radius of bead (r) = 1.5 um Net Force (F m ) = 5.91 pN 15 Figure 18: Animation of forces acting on the bead
Sample Calibration Video
1mm 0.75mm
0.5mm
0.25mm
0mm Video 1 : Sample video of beads moving for the calibration process
Calibration Results
3V Results
Single Magnet Calibration
Force at 1mm: 1.02pN
Force at 2mm: 0.98pN
Double Magnet Calibration
Force at 1mm: 0.76pN
Force at 2mm: 0.73pN
6V Results
Single Magnet Calibration
Force at 1mm: 2.23pN
Force at 2mm: 1.85pN
Double Magnet Calibration
Force at 1mm: 1.44pN
Force at 2mm: 1.20pN
Figure 19 and 20: Caparison of the forces the single and double magnet could achieve using 3V and 6V
Calibration Results
12V Results
Single Magnet Calibration
Force at 1mm: 5.91pN
Force at 2mm: 4.84pN
Double Magnet Calibration
Force at 1mm: 3.52pN
Force at 2mm: 3.18pN
Figure 21: Caparison of the forces the single and double magnet could achieve using 12V We are mainly concerned about the 12V measurements The results show that the single magnet can achieve higher forces than the double magnet
Conclusion
We accomplished our objectives:
1) We were able to design and build a pair of magnetic tweezers that can achieve over 1.5pN
Single magnet magnetic tweezers can achieve 3.94times more force than old design Double magnet magnetic tweezers can achieve 2.35times more force than old design 2) Successfully able to calibrate both magnetic setups
Future Work
F
m
B
m = magnetic moment in a superparamagnetic bead B = magnetic field in Tesla
B
K
0
nI
I = amperes n = turns per meter K = permeability 0 = magnetic constant Permeability of steel = 100 Permeability of Mu Metal = 20,000
Future Work
Mu Metal Nickel-iron alloy Permeability Ability to support magnetism 200 times than that of steel Heat treatment Reduces amount of oxygen in metal Gains back permeability that was lost
Future Work
Heat Conduction Thermoelectric Cooling Peltier Cells Liquid Cooling System Water Blocks
Future Work
Stage Holds PDMS wells and tube Repeatable parameters Detachable Fitted to optics table or microscope if needed
Acknowledgments
Dr. Valentine Vullev Dr. Sharad Gupta Dr. Hyle Park Dr. Jerome Schultz Gokul Upadhyayula Hong Xu
References
1) 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.
2) Danilowicz, Claudia, Greefield, Derek and Prentiss, Mara. “Dissociation of Ligand Receptor Complexes Using Magnetic Tweezers.” Analytical Chemistry Vol. 77, No. 10. 15 May. 2005.
3) 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.
5) Startracks Medical, “Serves Business, Education, Government and Medical Facilities Worldside.” American Solution. Startracks.org, Inc. Copyright 2003.