Optically controlled hydrodynamic micro-manipulation

The ability to precisely manipulate micro- and nano-scale objects has been a major driver in the progression of nanotechnologies. In this proceedings we describe a form of micro-manipulation in which the position of a target object can be controlled via locally generated fluid flow, created by the motion of nearby optically trapped objects. The ability to do this relies on a simple principle: when an object is moved through a fluid, it displaces the surrounding fluid in a predictable manner, resulting in controllable hydrodynamic forces exerted on adjacent objects. Therefore, by moving optically trapped actuators using feedback in response to a target object's current position, the flow-field at the target can be dynamically controlled. Here we investigate the performance of such a system using stochastic Brownian dynamics simulations, which are based on numerical integration of the Langevin equation describing the evolution of the system, using the Rotne-Praga approximation to capture hydrodynamic interactions. We show that optically controlled hydrodynamic micro-manipulation has the potential to hold target objects in place, move them along prescribed trajectories, and damp their Brownian motion, using the indirect forces of the surrounding water alone.