Vortex Machining

The goal of this research is to obtain an understanding of a new, nanometer level, surface removal process that utilizes locally induced vortices of polishing slurry. These vortices are produced by a micrometer scale oscillating fiber immersed in the fluid near to the surface to be machined, the vortices being stationary relative to the probe. Probes of varied diameters (7 µm to 400 µm), oscillating at high frequencies (over 100 Hz to 10’s of kHz) will produce localized vortices of varying size and magnitude resulting in Material Removal (MR) footprints with lateral dimensions of less than a millimeter. The size of the process footprint will be controlled by the amplitude and frequency of the driving oscillations and the orientation of the probe with respect to the workpiece. The subaperture processes involved primarily find application in the optics community where they are most commonly used for selective material removal in localized regions for form correction. However, it is possible that this process can be extended for surface machining in holes, trenches and other complex geometries thereby expanding to machining of micrometer scale components for MEMS amd meso-scale assemblies. The MR function describes how the removed material varies with tooling radius or coordinates. Deriving this function is critical in fully understanding the MR process. The goal of this current research project is to identify and quantify critical process parameters and their impact on the MR footprint and surface quality through a combined experimental and theoretical approach. This will be achieved by 1) using an analytical model to predict vortex patterns and velocities associated with different fiber sizes and drive frequencies, 2) experimentally determine the correlations between vortex dynamics and shapes and the resulting MR footprints, 3) further investigate the impact of other boundary conditions on the MR function, and 4) investigate the significance of the abrasive slurry chemistry on materials such as silicon and silica.