Optical Measurement of Microscopic Forces and Torques

Nieminen, T. A., Heckenberg, N. R. and Rubinsztein-Dunlop, H. (2000). Optical Measurement of Microscopic Forces and Torques. In: Videen, G., Fu, Q. and Chylek, P., Fifth International Conference on Light Scattering by Nonspherical Particles: theory, measurements, applications. Light Scattering by Nonspherical Particles: Halifax Contributions: 5th Conference on Electromagnetic and Light Scattering by Nonspherical Particles: Theory, Measurements, and Applications, Halifax, Canada, (308-311). 28 August - 1 September.

Document type: Conference Paper
Sub-type: Fully Published Paper
Collection: School of Physical Sciences Publications
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Author Nieminen, T. A.
Heckenberg, N. R.
Rubinsztein-Dunlop, H.
Title of paper Optical Measurement of Microscopic Forces and Torques
Conference Paper Type Fully Published Paper
Conference name Light Scattering by Nonspherical Particles: Halifax Contributions: 5th Conference on Electromagnetic and Light Scattering by Nonspherical Particles: Theory, Measurements, and Applications
Conference location Halifax, Canada
Conference dates 28 August - 1 September
Proceedings title Fifth International Conference on Light Scattering by Nonspherical Particles: theory, measurements, applications
Editor Videen, G.
Fu, Q.
Chylek, P.
Place published Maryland, USA
Publisher Army Research Laboratory
Publication date 2000
ISBN 0 9702316 0 1
Start page 308
End page 311
Total pages 4
Collection year 2000
Language eng
Abstract/Summary Many spectacular successes have resulted from the use of laser trapped particles as force-sensing probes. For example, the forces applied to a DNA molecule as an RNA copy is made have been measured, as well as the physical properties of DNA. Optically trapped particles can be used to probe small forces and weak interactions which cannot be readily measured in any other way due to extreme sensitivity to ambient conditions. A number of groups have made measurements of trapping forces, with differing levels of sensitivity and accuracy. However, a serious and fundamental problem common to virtually all measurements of this type is the lack of reliable absolute measurement. Viscous drag forces are generally used for calibration, which immediately presents the problem of changes in viscosity resulting from heating by the trapping beam. Since the optical trapping forces are due to the transfer of momentum from the beam to the particle, it is in principle possible to measure the applied force and torque by measuring the momentum of the scattered light. Direct optical determination of the force and torque gives an absolute measurement, immediately eliminating difficulties with calibration. The theory of direct optical measurement of forces and torques acting on laser trapped non-spherical and birefringent probe particles is presented.
Subjects 240400 Optical Physics
240402 Quantum Optics and Lasers
Keyword optical tweezers
micromanipulation
optical torque
Q-Index Code E1
Q-Index Status Provisional Code
Institutional Status Unknown
 
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Created: Fri, 12 Mar 2004, 10:00:00 EST by Timo Nieminen on behalf of School of Mathematics & Physics  -  Detailed History