Optical Tweezers

Optical Tweezers

Resources

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

Our own setup

• Slide Setup
  • Slide Set-Up
• Microscope Slide Mount
  • Slide Mount Apparatus
• Stokes' Setup
  • Spring 2013 Method (ramped) [3]
  • Summer 2014 Method (sinusoidal) [4]
    • Stoke's Force Calibration Video (sinusoidal)[5]

  Using NI Vision Assistant

  • [6] Image Acquisition/Saving Images
  • [7] 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
    • 4.6 mW Beam [8]

  Calculating Trap Forces Using Stokes' Drag Force

  • [9] 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

    
  • 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

  [10]