Pressure Sensitivity of a Thermal Shear Stress Sensor

This paper reports on the pressure sensitivity testing of MEMS thermal shear stress sensors. The MEMS sensor is a micromachined, vacuum-cavity insulated, thermal shear stress sensor for underwater applications. This paper is focused on the combined experimental and numerical study carried out to examine the effects of changing environmental pressure on the MEMS-based shear stress sensors. Four different sensors were tested experimentally and numerically. The silicon nitride diaphragms for each sensor are 4-μm thick. The length of each diaphragm is 210-μm while the widths are 210-μm, 150-μm, 100-μm, and 75-μm respectively. It is found that reducing the surface area size and increasing the thickness of the sensor diaphragms are effective in minimizing the pressure sensitivity.

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Numerical study of a dynamic resonant wall shear stress sensor with spectral element method

Journal of Fluids and Structures ◽

10.1016/j.jfluidstructs.2013.03.016 ◽

2013 ◽

Vol 40 ◽

pp. 356-365

Author(s):

Xu Zhang

Keyword(s):

Shear Stress ◽

Wall Shear Stress ◽

Spectral Element Method ◽

Numerical Study ◽

Spectral Element ◽

Stress Sensor ◽

Shear Stress Sensor ◽

Wall Shear ◽

Element Method

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A Novel Method for Determining Pressure Sensitivity of Underwater Shear-Stress Sensor Skins

Microelectromechanical Systems ◽

10.1115/imece2005-82123 ◽

2005 ◽

Author(s):

Jason Clendenin ◽

Yong Xu ◽

Steve Tung

Keyword(s):

Shear Stress ◽

Intrinsic Stress ◽

Gauge Factor ◽

Pressure Sensitivity ◽

Sensing Element ◽

Stress Sensor ◽

Sensing Applications ◽

Shear Stress Sensor ◽

Novel Method ◽

Stress Sensing

This paper reports the development of a novel method for determining the pressure sensitivity of two types of surface micromachined underwater shear stress sensor skins for micro shear stress sensing applications. The two types of sensors consisted of a thin-diaphragm sensor and a thick-diaphragm sensor. The focus is on the use of a combination of metrology and numerical simulation to theoretically determine the pressure sensitivity of the sensors and compare to experimental data. Using this combination, the nitride diaphragm deflection, the intrinsic stress of the diaphragm, and the piezoresistive gauge factor of the polysilicon sensing element were successfully determined. For the thin-diaphragm sensor, the tensile intrinsic stress and gauge factor were determined to be 28 MPa and 4, respectively. For the thick diaphragm sensor, the average tensile intrinsic stress and gauge factor were 48 MPa and 12, respectively. Using these numbers, the pressure sensitivity of the shear stress sensors was successfully modeled and verified against experimental results.

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