Optical TweezersTeam:

Maryam Badakhshi,Shannon O’Keefe,

Laura Poloni,Hasmita Singh

Overview1) Introduction2) Background & Applications3) Apparatus4) Laser Safety

1. Introduction

Experiment Context --PresentationNo presentation component available in the

Advanced Physics Labs coursesThis presentation component is meant to be

introduced to the students by the professor or TA of the course, in advance to the experiment

Experiment Context --StudentsMain purpose:

Give general information about the experiment and apparatus

Applications for the apparatusStudents may use this presentation to choose

their experimentAlso to acquaint students with laboratory

concepts, the equipment, and the safety procedure

Relevant CoursesThis experiment is based on knowledge of

Energy Equipartition theory that may be related to back ground courses in both Engineering and Arts and Sciences :Phy293 EngineeringPHY256H1  Arts and Science

This lab may also be used in the following courses: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

This presentation introduces the Optical Trapping apparatus and the many interesting applications of it

2. Background & Applications

Manipulation of Nanowires

(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

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• Invisible light: damage may only be detected post-injury• Severe damage may require surgery or transplant• Scars / blind spots in the field of vision• Depending on location of the burn, could permanently lose:• Central vision• Peripheral vision

Laser Hazards Control

• Wear laser safety glasses AT ALL TIMES

- Wavelength and Optical Density

• Remove wristwatches or reflective jewellery

• Close and lock the room door

• Place “Laser Work in Progress” warning sign on door

• If someone unexpectedly enters, turn laser off

• 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

Questions?