Numerical description of the manipulation of non-sphericalparticles by optical tweezers- A combined optical and hydrodynamic approach -

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Optical tweezers (OTs) are used as an established tool in biology and medicine. This technique allows the contact-free manipulation of micro-sized objects and single cells. Since OTs can penetrate each other without influence, multiple objects can be handled simultaneously. For this reasons, OTs have become more prevalent in micro technolgy, e.g. for the assembling of complex structured objects or as a driving force for micro-scaled motors or pumps. To enhance the usability of the method to this field, a deeper understanding of the underlying processes is necessary. Unfortunately, most theoretical studies of the interaction between the laser light and the manipulated objects are restricted to spherical or elliptical shapes. Besides, only the static case is considered.To overcome the limitations, we plan to extend in a first step the geometrical optics based model for the force calculation to arbitrary shaped objects. The next and most important step will be the simulation of the dynamical behavior. Most optical tweezers are used in a liquid environment, since the high damping, e.g. in comparison to air, ensures a stable trapping of the particle. For this reason, the hydrodynamic forces must also be taken into account. Within this project, we will provide a method for a more complete description of dynamical processes in optical tweezers with the help of a combination of geometrical optics with hydrodynamics. The results of the numerical analysis will be also verified experimentally, as well.