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Proceedings Paper

Measurements of particle-wall interaction forces using simultaneous position and force detection (Conference Presentation)
Author(s): Anatolii V. Kashchuk; Ann A. M. Bui; Alexander B. Stilgoe; David M. Carberry; Timo A. Nieminen; Halina Rubinsztein-Dunlop

Paper Abstract

Particle–wall interactions are important in biology, micromachining, coagulation studies, and many other areas of science. As a contactless tool, optical tweezers are ideal for measuring these kind of interactions. Here we will present a new method for calculating the non-optical forces acting on a trapped particle using simultaneous position and force detection. Analysis of the particle's Brownian motion when trapped gives a measure of all the forces experienced by the particle. In contrast, measuring only the light's momentum change directly gives the solely optical force. This is achieved measuring the changes in the scattered light. The difference between the forces recorded by the two techniques reveals the external forces acting on the trapped particle. Therefore, by trapping the particle close to a wall, one can study the particle-wall interaction force in details. The simulation were done using the optical tweezer toolbox [1] to find the optical force acting on a particle. The net force was calculated from a Brownian motion’s statistics of a trapped particle in the presence of the exponential external force. By using the proposed method, we were able to successfully reconstruct the external force. The experiment was done on a trapped spherical PMMA particle (d=2.2um) close to the 3D-printed wall. For the particle-wall distance ~0.7um the non-optical force is ~100fN . The experiment and simulation results confirm the efficiency of the proposed method for an external force measurements. [1] Nieminen et al., J. Opt. A 9, S196-S203 (2007).

Paper Details

Date Published: 10 November 2016
PDF: 1 pages
Proc. SPIE 9922, Optical Trapping and Optical Micromanipulation XIII, 99221C (10 November 2016); doi: 10.1117/12.2236419
Show Author Affiliations
Anatolii V. Kashchuk, The Univ. of Queensland (Australia)
Ann A. M. Bui, The Univ. of Queensland (Australia)
Alexander B. Stilgoe, The Univ. of Queensland (Australia)
David M. Carberry, The Univ. of Queensland (Australia)
Timo A. Nieminen, The Univ. of Queensland (Australia)
Halina Rubinsztein-Dunlop, The Univ. of Queensland (Australia)

Published in SPIE Proceedings Vol. 9922:
Optical Trapping and Optical Micromanipulation XIII
Kishan Dholakia; Gabriel C. Spalding, Editor(s)

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