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The Strathprints institutional repository is a digital archive of University of Strathclyde research outputs.

Strathprints serves world leading Open Access research by the University of Strathclyde, including research by the Strathclyde Institute of Pharmacy and Biomedical Sciences (SIPBS), where research centres such as the Industrial Biotechnology Innovation Centre (IBioIC), the Cancer Research UK Formulation Unit, SeaBioTech and the Centre for Biophotonics are based.

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The transverse trapping force of an optical trap: factors affecting its measurement

Wright, Amanda J. and Wood, Tiffany A. and Dickinson, Mark R. and Gleeson, Helen F. and Mullin, Tom (2003) The transverse trapping force of an optical trap: factors affecting its measurement. Journal of Modern Optics, 50 (10). pp. 1521-1532. ISSN 0950-0340

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Abstract

We report new observations that question the validity of using the escape method to deduce optical trapping forces in optical tweezers. The results were obtained by measuring the minimum beam power required to trap a particle subject to fluid flow, created by movement of the sample stage. The power was found to increase by approximately 50% over the range of amplitudes of movement used. This suggests that the measured trapping force is not solely dependent upon the velocity of the fluid past the trapped particle, as commonly assumed. These effects were observed at all fluid velocities and accelerations employed. We consider various causes for the observed effects but an explanation remains an outstanding challenge.