Optical Tweezers Team: MaryamBadakhshi, Shannon O’Keefe, Laura Poloni, Hasmita Singh
Overview • 1) Background & Applications • 2) Apparatus • 3) Laser Safety
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
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
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
MainComponents Safe! Very Dangerous!
Optical Trap Laser Characteristics • 980 nm Infrared range • 330mW maximum power • Collimated beam • Class 3B laser Optical Trapping Kit, Thorlabs. 2009.
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
Hazards • Diffuse reflections • Invisible • Most dangerous procedure, contact your TA/Instructor • Eye injuries without laser safety glasses Stray Beams Beam Alignment Biological Effects
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 SurferSam Online.
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.
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