Molecular Imaging and Photonics, Department of Chemistry, KU Leuven, Celestijnenlaan 200F, Leuven 3001, Belgium.
Center for Cellular Imaging, Core Facilities, the Sahlgrenska Academy, University of Gothenburg, Medicinaregatan 5A-7A, Box 413, Gothenburg 40530, Sweden.
ACS Nano. 2023 Feb 28;17(4):3797-3808. doi: 10.1021/acsnano.2c11753. Epub 2023 Feb 17.
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 μm). 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.
对光学场中粒子的空间和时间运动进行映射对于理解和进一步改进对其光捕获动力学的三维时空控制至关重要。然而，捕获三维运动并不简单，大多数成像系统只能捕获三维运动的二维投影，其中关于轴向运动的信息无法直接获得。在这项工作中，我们使用最近开发的宽场多平面显微镜（成像体积为 50×50×4μm），在不同的光学实验条件下，解析了 200nm 荧光聚苯乙烯粒子在光捕获点处的三维整合轨迹。粒子在焦点处聚集，遵循一些具有浅锥形分布的优先三维通道。我们证明了径向和轴向流速分量取决于与焦点的轴向距离，这与散射/梯度光力直接相关。虽然粒子速度和轨迹主要取决于捕获激光的轮廓，但如果不考虑由流体动力产生的集体效应，它们就无法完全解释。
