Computational modeling of optical manipulation of dielectric objects in complex optical fields and microfluidic flow

The response of the biological cells to optical manipulation in the bio-microfluidic devices is strongly influenced by the flow and motion inertia. There is a variety of microfluidic architectures in which both the cell-fluid interaction and the optical field are driving forces for segregation and manipulation of the cells. We developed a computational tool for analysis/optimization of these devices. The tool consists of two parts: an optical force library generator and the computational fluid dynamics solver with coupled optical force field. The optical force library can be computed for spherical and non-spherical objects of rotational symmetry and for complex optical fields. The basic idea of our method is to a) represent an incident optical field at the biological cell location as an angular spectrum of plane waves; b) compute the scattered field, being a coherent superposition of the scattered fields coming from each of the incident plane waves, with the powerful T-matrix method used to compute the amplitude matrix; c) use the incident and computed scattered fields to build a spatial map of optical forces exerted on biological cells at different locations in the optical beam coordinate system, and d) apply the library of optical forces to compute laser beam manipulation in microfluidic devices. The position and intensity of the optical field in the microfluidic device may be dynamic, thus optical forces in microfluidic device are based on the instantaneous relative location of the cell in the beam coordinate system. The cell is simulated by the macroparticle that undergoes mutual interactions with the fluid. We will present the exemplary applications of the code.