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MSE Seminar Series: Arthur La Porta
Friday, October 23, 2009
1:00 p.m.
Room 2108, Chemical and Nuclear Engineering Bldg.
For More Information:
Joanne Kagel

Angular Trapping of Micro-Particles: Rotating and Applying Torque to Biological Molecules with Optical Tweezers

Presented by Arthur La Porta
Assistant Professor, Department of Physics
University of Maryland

Although scientists and engineers have recently come to appreciate the possibility of making a nano-scale machines, nature contains a great variety of single molecule machines that use chemical energy to do work or process information. A great deal has been learned about such machines using optical tweezers, as well as other technologies. I will describe the Optical Torque Wrench, a new kind of optical tweezers that can trap particles at a specific angular orientation and measure the torque acting on the particle. Using this technique we are able to rotate particles composed of anisotropic materials by varying the polarization state of the trapping beam, and we are able to determine the angular deviation and torque acting on the particles by detecting amount of angular momentum transferred to the trapping beam. The detection scheme is able to measure torques of a few pN-nm. Experiments using this system require application of force and measurement of displacement along the axial direction. I will also describe preliminary results for a new method for enhancing the accuracy of measurements of axial position.

This Event is For: Graduate • Faculty • Post-Docs

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