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
Slide 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)
Slide 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
Slide 7
2. Background & Applications
Slide 8
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
Slide 9
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
Slide 10
(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)
Slide 11
3. Apparatus
Slide 12
Main Components Very Dangerous! Safe!
Slide 13
Main Components
Slide 14
4. Laser Safety
Slide 15
Optical Trap Laser Characteristics 980 nm Infrared range 330mW
maximum power Collimated beam Class 3B laser Optical Trapping Kit,
Thorlabs. 2009.
Slide 16
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
Slide 17
Hazards Diffuse reflections Invisible Most dangerous procedure,
contact your TA/Instructor Eye injuries without laser safety
glasses Stray Beams Beam Alignment Biological Effects
Slide 18
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 SurferSam Online.
Slide 19
Biological Effects Laser Light 400-1400nm Focussed beam on
retina Amplification of light by human eye: 10,000 Extremely 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.
Slide 20
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.