MEMS Pressure Sensor Array for Aeroacoustic Analysis of the Turbulent Boundary Layer

The second stage of the design, fabrication, and characterization of a surface micro-machined, front-vented, 64 channel (8×8), capacitively sensed pressure sensor array is de-scribed. The array was fabricated using the MEMSCAP PolyMUMPs R © process, a three layer polysilicon surface micromachining process with an additional fabrication step using Parylene-C. An acoustic lumped element model was used to model an individual micro-phone and then applied to the array as a whole. The computational results for the design, including mechanical components, environmental loading, fluid damping, and other acous-tic elements are detailed. Theory predicts single element sensitivity of 0.65 mV/Pa at the gain stage output in the 400-40,000 Hz band. A laser Doppler velocimetry (LDV) system has been used to map the spatial motion of the elements in response to electrostatic excita-tion. A strong resonance appears at 430 kHz for electrostatic excitation, in agreement with mathematical models. Static stiffness measured electrostatically using an interferometer is 0.1 nm/V2, similar to the expected stiffness. Preliminary acoustic sensitivity studies show single element acoustic sensitivity of 0.6 mV/Pa from 200 to 20 kHz. A more in depth analysis of acoustic sensitivity is ongoing as well as element-to-element variability