Abstract
We propose a new approach to calculate the sensitivity factor of the detector in optical tweezers. In this work, we used a charge-coupled device (CCD) camera and a quadrant photodiode (QPD) for the extraction of the various positions occupied by the trapped object (in this case, silica beads of different diameters). Image-J software and the Boltzmann statistical method were then used to estimate the sensitivity of the detector. Silica beads of diameter 0.8 µm, 2 µm, a system of 2 µm bead stuck to 4.5 µm one and another system of 2 µm beads stuck to 2 µm one, were studied. This work contributes significantly to making better calibration of the detector without taking into account the geometry of the object imprisoned in the optical trap. We further developed an approach to calculate the interaction force between two microbeads. This approach does not require any knowledge of solvent viscosity and works for all types of samples.
Highlights
Manipulation of biological specimens using microscopic light is a subject of increasing interest
For Colloidal Studies, Crocker and Grier [6] described a set of image processing algorithms for extracting quantitative data from digitized video microscope images of colloidal suspensions
The optical trapping mechanism is based on the momentum exchange between the trapped particle and the trapping beam using a scattering process
Summary
Manipulation of biological specimens using microscopic light is a subject of increasing interest. In all applications of the laser trapping technique, it is important to have knowledge about the optical force used in trapping the particle.
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