Nanoscale Hot-Wire Anemometer Probes for Turbulence Measurements: From Design to Fabrication
Liu, Edmund T.
High-resolution turbulence measurements demand state-of-the-art instrumentation due to the large scale separations observed in these flows. Conventional hot-wire probes suffer from both spatial and temporal filtering due to the relatively large physical size of the wire when compared to the smallest length scales in the flow. Semiconductor fabrication equipment allows probes with extremely small wire dimensions to be produced economically, extending measurement capabilities while decreasing cost. A fabrication process flow is developed with designs based on the existing Nanoscale Thermal Anemometry Probe (NSTAP), and probes are successfully produced with both high yield and throughput. With a platinum wire 60 microns in length, 2 microns in width, and 100nm thick, these probes are found to resolve higher frequency spectra than conventional probes. To showcase the capabilities of nanofabrication, a probe with a smooth, contoured body is designed and fabricated. Probe fabrication by novel additive means is also explored. While existing fabrication methods focus on removing material from bulk silicon through etching, additive probes are built by stacking thin films on top of one another. This approach promises greater control over the final shape of the probe, as patterns are defined by photolithography, rather than etching. Two processes focusing on electroplating and SU-8 photosensitive epoxy are developed and studied.
Fluid Mechanics; Hot-wire Anemometry; Nanofabrication; Semiconductor Processing; Turbulence
Bewley, Gregory Paul
Hammer, David A.
M.S., Mechanical Engineering
Master of Science
dissertation or thesis