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Optical Tweezers

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

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Optical Tweezers

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  1. Optical Tweezers Team: MaryamBadakhshi, Shannon O’Keefe, Laura Poloni, Hasmita Singh

  2. Overview • 1) Introduction • 2) Background & Applications • 3) Apparatus • 4) Laser Safety

  3. 1. Introduction

  4. Experiment Context • Optical Tweezers are a brand new experiment • Not 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

  5. Relevant Courses • Theory behind Experiment: • Energy Equipartition theory • Relates to courses in both Engineering and Arts and Science: • Phy293  Engineering • PHY256H1  Arts and Science • This lab is designed for the Advanced Physics Labs: • PHY424/426/428/429 (A&S) and PHY327/427/428/429 (Engineering)

  6. Experiment Learning Objectives • Students 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

  7. 2. Background & Applications

  8. Optical Tweezers • 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 Public image by RockyRoccon 2007

  9. Manipulation of Nanodevices • Four spheres trapped and rotated by linearly scanning with laser light (Tong et. al., Nano Letters, 2010) (Nam et. al., IJPEM, 2009) • Alignment and rotation of a silver nanowire

  10. Isolation and Visualization of DNA Staining with Fluorescent Dye Force-Extension analysis of the trapped DNA “Catching” a Single DNA Molecule Trapping of two beads (Gross et. al., Methods in Enzymology, 2010) (Gross et. al., Methods in Enzymology, 2010) Protein-coated DNA region Fluctuations in DNA molecule

  11. 3. Apparatus

  12. MainComponents Safe! Very Dangerous!

  13. MainComponents

  14. 4. Laser Safety

  15. Optical Trap Laser Characteristics • 980 nm  Infrared range • 330mW maximum power • Collimated beam • Class 3B laser Optical Trapping Kit, Thorlabs. 2009.

  16. Laser Classification • Considered incapable of causing injury • Hazardous under direct and specular reflection, but not diffuse reflection • Direct exposure to beam is an eye hazard • Maximum power 500mW

  17. Hazards • Diffuse reflections • Invisible • Most dangerous procedure, contact your TA/Instructor • Eye injuries without laser safety glasses Stray Beams Beam Alignment Biological Effects

  18. Biological Effects • Cornea • Focussing element • Lens • Fine focus • Vitreous Humor • Retina • Image is projected from the cornea and lens • Connection to brain through optic nerve • Fovea • Sharp vision Vitreous Humor Schematic of the eye by SurferSamOnline.

  19. Biological Effects Retinal Hazard Region • Laser Light 400-1400nm • Focussed beam on retina • Amplification of light by human eye: 10,000 • Extremely large irradiance • Dependent on exposure time 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.

  20. Laser Hazards Control • Place “Laser Work in Progress” warning sign on door • Close and lock the room door • Remove wristwatches or reflective jewellery • Wear laser safety glasses AT ALL TIMES • - Wavelength and Optical Density • If someone unexpectedly enters, turn laser off Thorlabs. 2010. Laser Safety Industries. 2010. • Turn off laser when changing samples • Return the laser controller key when completed • In case of an emergency, contact your TA/Instructor or UofT Campus Police 416-978-2222

  21. Questions?

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