created by: maryam badakhshi, shannon o’keefe, laura poloni, hasmita singh
TRANSCRIPT
Optical Tweezers
Created by: Maryam Badakhshi, Shannon O’Keefe, Laura Poloni, Hasmita Singh
Overview1) Background & Applications2) Apparatus3) Laser Safety
1. 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)
2. Apparatus
Main Components
Very Dangerou
s!Safe!
Main Components
3. Laser Safety
Optical Trap Laser Characteristics980 nm Infrared range330mW maximum powerCollimated beamClass 3B laser
Optical Trapping Kit, Thorlabs. 2009.
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
Vitreous Humor
Schematic of the eye by SurferSam Online.
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
Elements of Laser Safety, Gary E. Myers. 1998.
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
Thorlabs. 2010.
Laser Safety Industries. 2010.
Questions?