Precise calibration of optical tweezers using the interference pattern in the backscattered signal and application to the microrheology of blood clots (Conference Presentation)

Nathalie Westbrook; Flavie Gillant; Julien Moreau; Karen Perronet; Maximilian U. Richly; Antigoni Alexandrou; Laura Wolff; Jean-Marc Allain

doi:10.1117/12.2530645

9 September 2019 Precise calibration of optical tweezers using the interference pattern in the backscattered signal and application to the microrheology of blood clots (Conference Presentation)

Nathalie Westbrook, Flavie Gillant, Julien Moreau, Karen Perronet, Maximilian U. Richly, Antigoni Alexandrou, Laura Wolff, Jean-Marc Allain

Author Affiliations +

Proceedings Volume 11083, Optical Trapping and Optical Micromanipulation XVI; 110830H (2019) https://doi.org/10.1117/12.2530645
Event: SPIE Nanoscience + Engineering, 2019, San Diego, California, United States

Abstract

When trapping a dielectric bead with optical tweezers, light backscattered by the bead interferes in the back focal plane of the objective with light reflected by the microscope cover slip. This well contrasted interference pattern can be used to calibrate precisely the relative position of the bead with respect to the center of the trapping laser, as well as the stiffness of the trap. We compared four calibration methods previously implemented in forward detection, namely step response, Bayesian inference, power spectrum analysis and equipartition. We showed that they agree for different heights and trapping powers. Effect of acoustic noise on all methods was observed, and the step response method was shown to be the least sensitive. In addition to giving better access to the sample, this backscattered interference pattern provides precise location of the bead with respect to the laser, both laterally and axially, even when the bead is not trapped by the laser. We apply this to microrheology of blood clots, where the focused laser exerts a force on a bead confined by the fibrins of the clot but does not actually trap it .

Conference Presentation

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Nathalie Westbrook, Flavie Gillant, Julien Moreau, Karen Perronet, Maximilian U. Richly, Antigoni Alexandrou, Laura Wolff, and Jean-Marc Allain "Precise calibration of optical tweezers using the interference pattern in the backscattered signal and application to the microrheology of blood clots (Conference Presentation)", Proc. SPIE 11083, Optical Trapping and Optical Micromanipulation XVI, 110830H (9 September 2019); https://doi.org/10.1117/12.2530645

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KEYWORDS

Calibration

Blood

Optical tweezers

Precision calibration

Optical calibration

Acoustics

Bayesian inference

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