optical tweezers-the force of light-17sl
DESCRIPTION
optical tweezers, the force of lightTRANSCRIPT
OPTICAL TWEEZERS: THE
FORCE OF LIGHT
Introduction
General description
Working
Vedio of traping particle
Diagrams of instrument
Application
INTRODUCTIONOptical tweezers:
Light can exert forces on small
dielectric objects1, A tightly focused
beam of light can trap micron-sized
objects, such as latex beads. This
“optical trapping” principle has found
many applications in chemistry, physics
and biology. It has found its most
prominent use in biophysics, because it
allows the manipulation (like with a
tweezers) of single biomolecules. For
example, “optical tweezers” have been
used to measure the elasticity
OPTICAL TWEEZERS ?An optical tweezer is a scientific instrument thatuses a focused laser beam to provide an attractiveor repulsive force, depending on the index mismatch(typically on the order of piconewtons) to physicallyhold and move microscopic dielectric objects. Opticaltweezers have been particularly successful instudying a variety of biological systems in recentyears.Dielectric objects are attracted to the center of thebeam, slightly above the beam waist, as describedin the text. The force applied on the object dependslinearly on its displacement from the trap center
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Trapping a particle with light
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Optical Tweezersrolf
WORKING OF TWEEZER
YouTube - Protein crystal in optical tweezers.flv
The Nd:YAG laser (1064 nm wavelength) is themost common laser choice because biological specimensare most transparent to laser wavelengthsaround 1000 nm. This assures as low an absorptioncoefficient as possible, minimizing damage tothe specimen, sometimes referred to as opticution.Perhaps the most important consideration in opticaltweezer design is the choice of the objective.
WORKING
Basic Components
Objective LensL2 L3L1
f1 + f2 f3 16 cm
Image created from Physlet at http://webphysics.davidson.edu/Course_Material/Py230L/optics/lenses.htm Physlet by Dr. Wolfgang Christian and Mike Lee
Laser
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Schematic diagramLaser
Beam expander
White Light Source
Cell
CCDCCD
Tip
ObjectiveColor Filter
Laser line mirror
Laser line mirror
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Dual beam tweezer design
Kinesin motor motion
RAY OPTICS RADIATION PATTERN•A laser beam is expanded and collimated. This collimated beam is directed through a microscope objective into a flow cell. Spheres with a higher index of refraction than the medium in the cell (water) will be trapped at the focus of the beam.
YouTube - real-life Tetris under a microscope.flv
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APPLICATIONSWe will calibrate the strength of an optical
trap (Optical Tweezer)
Optical Tweezers may be used to measure very small forces (femtoNewton, 10-15N)
Applications include Biophysics
THANk YOU FOR YOUR ATTENTION