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Optical Tweezers. Team : Maryam Badakhshi , Shannon O’Keefe, Laura Poloni , Hasmita Singh. Overview. 1) Introduction 2) Background & Applications 3) Apparatus 4) Laser Safety. 1. Introduction. Experiment Context. Optical Tweezers are a brand new experiment - PowerPoint PPT Presentation
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Optical TweezersTeam:
Maryam Badakhshi,Shannon O’Keefe,
Laura Poloni,Hasmita Singh
Overview1) Introduction2) Background & Applications3) Apparatus4) Laser Safety
1. Introduction
Experiment ContextOptical Tweezers are a brand new
experimentNot currently part of Advanced Physics Labs Purpose of presentation:
TA/Instructor to deliver a brief presentation to students Apparatus Applications Hazards Safety procedures
Students can make an informed decision regarding choosing an experiment
Relevant CoursesTheory behind Experiment:
Energy Equipartition theory Relates to courses in both Engineering and
Arts and Science:Phy293 EngineeringPHY256H1 Arts and Science
This lab is designed for the Advanced Physics Labs:PHY424/426/428/429 (A&S) and
PHY327/427/428/429 (Engineering)
Experiment Learning ObjectivesStudents will have the opportunity to :
Work on interesting and challenging experiments
Deepen their understanding of the underlying Physics
Further develop laboratory, analysis and communication skills
Gain familiarity with the Optical Trapping apparatus and its various applications
2. Background & Applications
Optical Tweezers
Public image by RockyRoccon 2007
• Highly focused laser beam is used to physically hold and move microscopic dielectric objects
• Can manipulate objects with noncontact and direct trapping
• Advanced Physics Laboratory for the Optical Tweezers apparatus involves the determination of optical trap stiffness of silica beads through various methods
Manipulation of Nanodevices
(Tong et. al., Nano Letters, 2010)
• Alignment and rotation of a silver nanowire
(Nam et. al., IJPEM, 2009)
• Four spheres trapped and rotated by linearly scanning with laser light
(Gross et. al., Methods in Enzymology, 2010)
Isolation and Visualization of DNA
Trapping of two beads
“Catching” a Single DNA Molecule
Force-Extension analysis of the trapped DNA
Staining with Fluorescent Dye
Protein-coated DNA region
Fluctuations in DNA molecule
(Gross et. al., Methods in Enzymology, 2010)
3. Apparatus
Main Components Very
Dangerous!Safe!
4. Laser Safety
Optical Trap Laser Characteristics980 nm Infrared range330mW maximum powerCollimated beamClass 3B laser
Laser Classification
Class 3B Laser
Safety Interlocks
Class 1 working environment
• Hazardous under direct and specular reflection, but not diffuse reflection• Direct exposure to beam is an eye hazard• Maximum power 500mW
• Considered incapable of causing injury
Hazards
Diffuse reflectionsInvisible
Most dangerous procedure, contact your TA/Instructor
Eye injuries without laser safety glasses
Stray Beams
Beam Alignment
Biological Effects
Biological EffectsCornea
Focussing elementLens
Fine focusVitreous HumorRetina
Image is projected from the cornea and lensConnection to brain through optic nerve
FoveaSharp vision
Biological EffectsLaser Light 400-1400nm
Focussed beam on retinaAmplification of light by human eye: 10,000Extremely large irradiance Dependent on exposure time
Retinal Hazard Region
Thermal Effects
• Overheating• Retina burns• Scars / blind spots in the field of vision• Invisible light: damage may only be detected post-injury• Severe damage may require surgery or transplant•Depending on location of the burn, could permanently lose:• Central vision• Peripheral vision
Laser Hazards Control
• Remove wristwatches or reflective jewellery
• Close and lock the room door
• Place “Laser Work in Progress” warning sign on door
• In case of an emergency, contact your TA/Instructor or UofT Campus Police 416-978-2222
• Return the laser controller key when completed
• Turn off laser when changing samples
• Wear laser safety glasses AT ALL TIMES
- Wavelength and Optical Density
• If someone unexpectedly enters, turn laser off
Questions?
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