Observations During Vortex Machining Process Development

Vortex machining is a newly developed process that utilizes vortices generated by oscillating a micrometer sized fiber in colloidal abrasive slurry to remove material in highly localized regions [1]. Typical material removal footprints produced by our current machining process have micrometer sized lateral dimensions and nanometer depths with volumetric removal rates near 20 μm³ per hour. The carbon fiber attached to the tuning fork oscillator is approximately 7 μm in diameter and 4 mm in length. Resonant frequencies of the probe (fiber and tuning fork) are in the order of 30 kHz and oscillate with amplitudes of the fiber tip up to 50 μm. For these initial tests a silicon substrate has been machined using 0.05 μm alumina colloidal slurry and the resulting footprints were measured by a scanning white light interferometer. This paper provides details of the developed machining process, observations from initial test results, process metrology, and a short discussion of future process challenges.