AeroMEMS wall hot-wire anemometer on polyimide foil for measurement of high frequency fluctuations

Abstract

Design, simulation, manufacturing, calibration, and basic characterization of a MEMS wall hot-wire anemometer is presented. A highly sensitive nickel thin film resistor spanning a reactive ion etched cavity in a polyimide foil is employed. This sensor is the first in literature to feature both a thermally insulating cavity and a flexible base material. The polyimide base material allows adopting of the sensor to aerodynamic surfaces, e.g. airfoils and turbine blades. A mismatch of curvature of aerodynamic surface and silicon sensor surface, as observed with previously presented MEMS hot-wire anemometers, is avoided. The combination of polyimide's low thermal conductivity and a cavity featuring FEM-optimized dimensions accounts for a very low power consumption (<30 mW). Fluctuations in wall shear stress up to 80 kHz can be resolved in constant-temperature mode. An average sensitivity of 0.44 V/(N/m2) is achieved in a wall shear stress range from 0 to 0.25 N/m2