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Proceedings Paper

A new method for calibrating the nonlinear range of a single-beam optical trap (Presentation Recording)
Author(s): Jamianne C. Wilcox; Benjamin J. Lopez; Otger Campas; Megan T. Valentine
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Paper Abstract

Optical traps allow for the precise application and measurement of pico-Newton forces in a wide variety of situations, and are particularly well suited for biophysical measurements of motor proteins and cells. Nearly all experiments exploit the linear regime of the optical trap, where force and displacement are related by a simple spring constant that does not depend on the trapped object’s position. This typically limits the useful force range to < 100 pN for high-NA objective lenses and reasonable laser powers. Several biological studies require larger forces, which are not accessible in the linear regime of the trap. The best means to extend the maximum force is to make use of the entire nonlinear range; however, current techniques for calibrating the full nonlinear regime are limited. Here we report a new method for calibrating the nonlinear trap region that uses the fluctuations in the position of a trapped object when it is displaced from the center of a single gradient optical trap by controlled flow. From the position fluctuations, we measure the local trap stiffness, in both the linear and non-linear regimes. This approach requires only knowledge of the system temperature, and is especially useful for measurements involving trapped objects of unknown size, or objects in a fluid of unknown viscosity.

Paper Details

Date Published: 5 October 2015
PDF: 1 pages
Proc. SPIE 9548, Optical Trapping and Optical Micromanipulation XII, 95480Y (5 October 2015); doi: 10.1117/12.2190397
Show Author Affiliations
Jamianne C. Wilcox, Univ. of California, Santa Barbara (United States)
Benjamin J. Lopez, Univ. of California, Santa Barbara (United States)
Otger Campas, Univ. of California, Santa Barbara (United States)
Megan T. Valentine, Univ. of California, Santa Barbara (United States)


Published in SPIE Proceedings Vol. 9548:
Optical Trapping and Optical Micromanipulation XII
Kishan Dholakia; Gabriel C. Spalding, Editor(s)

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