This project will demonstrate the effectiveness of a new micromachining process that can be used to create three-dimensional micro-mechanical, micro-optical and micro-fluidic devices in a wide variety of materials. Current micromilling techniques using high-speed spindles are plagued by spindle and tool runout that limit the feature size and tolerance. The concept is to replace the high-speed spindle with a piezoelectric driven tool holder that can move the diamond tool tip in a planar motion at frequencies up to 5000 Hz - the equivalent of 300,000 rpm. The two linear actuators are driven out of phase to create a tool path that can be changed from linear to elliptical to circular by varying the amplitude, frequency and phase of the excitation voltages. The goal is to significantly improve the capability of the mechanical machining by pushing the minimum feature size from 25 um to 1 um and the feature tolerance from 2 um to less than 200 nm while producing optical quality surface finish in a variety of materials.
Microelectromechanical systems (MEMS) offer designers the ability to create miniature mechanical oscillators, optical network components and biological labs on a chip, but the high cost and long lead time needed to create such devices using commercial semiconductor fabrication facilities has been an impediment to their widespread acceptance. Semiconductor techniques are designed for high-volume circuits using standard CMOS processing while many MEMS devices are needed in lower volumes, have more complex structures (such as moving three-dimensional micromirrors arrays) and require materials other than silicon. Past MEMS machining research has emphasized high-speed spindles while the effort introduces a new technique that avoids the runout issues inherent with a rotating spindle allowing smaller, more accurate features to be created. The resulting chip geometry leads to reduced machining forces and reduced tool/workpiece contact time creating longer tool life and extending the range of workpiece materials (plastics, metals and ceramics) when compared to normal diamond turning. The experiments are designed to study the material flow at small depths of cut, to define the limits of the process and to identify the optimum cutting conditions for different workpiece materials. Fabrication of prototype devices will demonstrate the integration of mechanical, optical and fluidic structures in 3D.
