Optical Tweezers

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Optical Tweezers

Background

Scattering Basics (from Michigan Tech)


Resources

  • Summer 2014 Powerpoint[1]
  • [2] Directions on how to use a QPD in an optical tweezer setup.
  • [3] Here are some slide prepping instructions from Berkeley.

Our own setup

  • Slide Setup
  • Microscope Slide Mount
  • Stokes' Setup
    • Spring 2013 Method (ramped) [4]
    • Summer 2014 Method (sinusoidal) [5]
      • Stoke's Force Calibration Video (sinusoidal)[6]

    Using NI Vision Assistant

    • [7] Image Acquisition/Saving Images
    • [8] How to track the microspheres in NI Vision Assistant using pattern matching.
      • We actually tried both using pattern matching and brute force point and click methods. Neither worked very well, so we recommend using the QPD to get position measurements

    Our calculations using Brownian Motion

    • 2.56 micrometer spheres
      • Spring 2014- 4.6 mW Beam [9]
      • Summer 2014- 637nm and 980nm lasers [10]

    Calculating Trap Forces Using Stokes' Drag Force

    • [11] iPython Calculations
    • Beam Power (mW) Escape Velocity (microns/second) Trap Force (pN)
      5.5 20.57 0.44
      8.5 33.49 0.72
      11.7 40.00 0.86
      15.3 62.60 1.34
      19.0 84.71 1.82
      23.0 110.77 2.38
      Trap force graph stokes 1.png
    • A simple calculation would say that I need a 10 billion watt laser to achieve a 1 Newton trapping force. We should totally do that. The spheres would be so incredibly trapped.

    Trapping Video

    [12]

    Performing Biological Measurements