Optical Tweezers

at

The National Institute of Standards and Technology and

Davidson College

Research performed by:

Rachel Patton McCord

Background: Optical Tweezers Physics • Balancing Forces:

• Scattering Force- “Radiation Pressure”• Gradient Force- Restoring force analogy to spring

Figure from: Svoboda and Block, 1994.

Physics, cont.• Tight focus = largest gradient force

• obtained with microscope objective

Images from: http://www.olympusmicro.com/primer/java/nuaperture/index.html

Basic Components

Objective LensL2 L3L1

f1 + f2 f3 16 cm

Image created from Physlet at http://webphysics.davidson.edu/Course_Material/Py230L/optics/lenses.htm Physlet by Dr. Wolfgang Christian and Mike Lee

Laser

NIST Alignment

• Gained experience with alignment by working on a two-laser trap setup.

Results

Single Trap

Both Traps Together

NIST Optical Tweezers Applications

• Liposomes• Stretching/Nanotubes• Microreaction Vesicles

• Single Mitochondria Isolation and Sorting• Available for PCR and genetic analysis

• Antigen/Antibody Binding• Quantum Dots in Polymersomes• Fluorescence Resonance Energy Transfer and

single molecule imaging

Davidson Setup

Results• Trapping microspheres in 3D

• 10 mW minimum power from laser (about 2 mW at the slide)

• Trapping single celled chlamydomonas

Image from: http://www.ucmp.berkeley.edu/greenalgae/chlorophyceae.html

Future Plans

• Force calibration• Measuring the swimming force of

chlamydomonas• Flagellar mutantsFurther in the future:• Physics Applications

• Stretching- elasticity, determining shear moduli

• Biology Applications• More chlamy- phototaxis• Virus adhesion

Acknowledgments• Dr. Kris Helmerson, Jeff Wells, Lara Crigger, Rani Kishore, Joe

Reiner at NIST

• Dr. John Yukich and Dr. Karen Bernd