posted on 2023-02-17, 16:48authored byBoris Louis, Chih-Hao Huang, Rafael Camacho, Ivan G. Scheblykin, Teruki Sugiyama, Tetsuhiro Kudo, Marc Melendez, Rafael Delgado-Buscalioni, Hiroshi Masuhara, Johan Hofkens, Roger Bresoli-Obach
Mapping of the spatial and temporal motion of particles
inside
an optical field is critical for understanding and further improvement
of the 3D spatio-temporal control over their optical trapping dynamics.
However, it is not trivial to capture the 3D motion, and most imaging
systems only capture a 2D projection of the 3D motion, in which the
information about the axial movement is not directly available. In
this work, we resolve the 3D incorporation trajectories of 200 nm
fluorescent polystyrene particles in an optical trapping site under
different optical experimental conditions using a recently developed
widefield multiplane microscope (imaging volume of 50 × 50 ×
4 μm3). The particles are gathered at the focus following
some preferential 3D channels that show a shallow cone distribution.
We demonstrate that the radial and the axial flow speed components
depend on the axial distance from the focus, which is directly related
to the scattering/gradient optical forces. While particle velocities
and trajectories are mainly determined by the trapping laser profile,
they cannot be completely explained without considering collective
effects resulting from hydrodynamic forces.