Contract Number – NNX11CG91P | SBIR Phase 1 | Principal Investigator – Ben Griffin | Project Start Date – 2/18/2011
Interdisciplinary Consulting Corporation proposes a sensor that offers the unique capability to make non-intrusive, direct, simultaneous mean and fluctuating shear stress measurement for subsonic and transonic test applications. Currently a standard for shear stress measurement tool does not exist.A precise silicon micromachined, differential capacitive, instrumentation grade sensor will facilitate skin friction measurement with high bandwidth, high resolution, and minimal sensitivity to pressure. The proposed sensor possesses through wafer vias for backside electrical contacts to enable non-intrusive measurements in turbulent boundary layers. A robust and compact package with miniature interface electronics enables flush sensor mounting conformal with surfaces. The sensor development effort transitions a proof-of-concept device by adding design components to have reduced pressure sensitivity to result in a commercially viable product. Circuit topology development for biasing and signal conditioning provides the ability to make simultaneous mean and dynamic shear stress measurement. The sensor performance will exceed its predecessors and set the standard for quantitative skin friction measurements. The simplicity of sensor design and an equally simple and proven fabrication technique allows for low cost, high performance sensors.The sensor holds promise to transform current flow control techniques and enable efficient aerodynamic designs. Existing shear stress estimation techniques rely on known correlation to a measured quantity. Direct measurement eliminates the need for a known correlation in an unknown flow. Capacitive transduction has been successful for a highly sensitive device with a large dynamic range and low noise floor, which is the current state of the art. The proposed sensor may therefore be improved beyond the state of the art to serve as a measurement standard for all types of skin friction measurement techniques.