Transcript (3DFM): Laser Tracking and Force Application

3D Force Microscope (3DFM): Laser Tracking and Force Application
CISMM: Computer Integrated Systems for Microscopy and Manipulation
Overview
System Optics
General
The latest version of the
3DFM, built on a Nikon
Eclipse 2000-E
microscope, allows users
to apply up to 10nN of
force while laser tracking
beads with 10nm, 1msec
resolution. Force
application via a
hexapole system should
provide unlimited
directional control of
magnetic beads inside
samples (compare to
tetrahedral data below).
Laser Tracking
Left: X-tracking
signal obtained by
x translation of a
1um polystyrene
bead through the
laser
Halogen Filter In Nikon Holder on top
QPD Fluorescence Block
Tracking Upper Dichroic
Power Meter
Right: Y-tracking
signal obtained by
y translation of a
1um polystyrene
bead through the
laser
Left: Z-tracking
signal obtained by
z translation of a
1um polystyrene
bead through the
laser
Additional Linear Filter Housing
Sample
Tracking Turning Mirror
Video Cam
Halogen 650<l<750nm?
Tracking Laser 830nm
Emission 550<l<604nm
Excitation l<580nm
Tracking Lower Dichroic
Roper CCD Cam
Fluor Dichroic
Tracking Laser Assembly
CCD Tracking Block
Hg Arc
Top Magnetic Pole Plate
Probe Bead
cell
220 m
Glass or
permeable
membrane
10 m
30 m
FeNi
Glass
100 m
1.2 NA water immersion objective
Short focal length
demands thin pole
plates.
System designed to
meet demands. Six
poles are used to
generate a hexapole
system, with a laser
used for particle tracking.
A view of the system
with six poles in place
atop six coils (top coil
drive ring is missing).
The current magnet
system. In this
image, the system
is open, waiting for
a sample to be
inserted.
In this image, the
system has been
closed and is ready
to be energized.
Force Generation
1. Tetrahedral Geometry
Force
Calculation
Method
Right: Tetrahedral
magnet system used in
first generation 3DFM
1. Laser/Video
track moving
bead.
2. Plug bead
velocity into
Stokes law
2. Hexapole Geometry
Material
Manufacturer
Fabrication Technique
Thickness
Permeability
Saturation
Magnetic
Shield
Corporation
Laser Cut
100 microns
30,000
8,000 Gauss
2. Medium
Permeability Foil
MuShield
Laser Cut
250 microns
12,000
15,000 Gauss
3. Low
Permeabiltiy Foil
MuShield
Laser Cut
175 microns
300
19,000-21,000 Gauss
4. Permalloy (10%
Fe, 90% Ni).
Electorplated
Material
In house
Electroplated
30 microns
1. Co-Netic AA
Perfection
Annealed
Electro Plated Poles
Left: Simulated data shows all vectors for which we
expect to be able to pull beads using the tetrahedral
geometry.
Center and Right: Actual data obtained by energizing
the magnets with random drive currents.
Left: Maximum forces
generated by 4 pole
system. For these tests
the pole was pushed
inside the sample
chamber to decrease
distance between the
pole tip and bead
Stokes law
F = 6 πaηv,
F is the force
a = bead radius
η = fluid viscosity
v = particle velocity
The equation holds
at low velocities
which are free
from turbulence
(called the
Stokes region).
Laser Machined Poles
http://cs.unc.edu/Research/nano/cismm/3d/index.html
Collaborators: Dr. William Davis, Dr. Ric Boucher
Project Lead:
Dr. Richard Superfine
Investigators: Jay Fisher, Ben Wilde, Kalpit Desai, Leandra Vicci, Jing Hao
5 December, 2003