Claims Analysis
Total Claims: 9
Claim 1
Independent Claim
121 words
A wall shear stress sensor comprising: a plate having micron dimensions; a plurality of piezoresistive supporting arms coupled to the plate and a substrate for suspending the plate from the substrate in a plane having a subject surface over which fluid flows, each arm having a longitudinal axis, the fluid having a flow component parallel to the longitudinal axis of each arm, the arm being strained in response to fluid flow over the subject surface displacing the plate and providing an indication of deflection of the plate along the longitudinal axes of the arms; and readout means coupled to the plate and arms to receive the indication of deflection of the plate and to therefrom provide measurements of detected shear stress.
Claim 2
Dependent Claim
121 words
A wall shear stress sensor comprising: a plate having micron dimensions; a plurality of piezoresistive supporting arms coupled to the plate and a substrate for suspending the plate from the substrate in a plane having a subject surface over which fluid flows, each arm having a longitudinal axis, the fluid having a flow component parallel to the longitudinal axis of each arm, the arm being strained in response to fluid flow over the subject surface displacing the plate and providing an indication of deflection of the plate along the longitudinal axes of the arms; and readout means coupled to the plate and arms to receive the indication of deflection of the plate and to therefrom provide measurements of detected shear stress.
Claim 3
Dependent Claim
58 words
A wall shear stress sensor as claimed in claim 1 wherein the piezoresistive supporting arms are substantially insensitive to displacement of the plate along axes transverse to the longitudinal axes of the arms, such that the readout means provides measurements of shear stress substantially independent of forces acting along axes perpendicular to the longitudinal axes of the arms.
Claim 4
Dependent Claim
21 words
A wall shear stress sensor as claimed in claim 1 wherein the piezoresistive supporting arms are formed of single crystal silicon.
Claim 5
Dependent Claim
37 words
A wall shear stress sensor as claimed in claim 1 wherein the piezoresistive supporting arms are dielectrically isolated from the substrate such that the arms provide indications of plate deflection in temperatures up to about 300° C.
Claim 6
Dependent Claim
128 words
A wall shear stress sensor as claimed in claim 1 wherein the plate and arms are fabricated by the process of: etching a cavity into a front surface of a first silicon wafer; bonding a front side of a second silicon wafer to the front surface of the first silicon wafer, such that a portion of a front side of the second silicon wafer faces the cavity etched into the first silicon wafer; thinning the second wafer from a backside opposite the front side to form a working layer suspended across the cavity in the first silicon wafer; and patterning and etching the plate and arms in the working layer in a manner such that the arms suspend the plate over the cavity in the first silicon wafer.
Claim 7
Dependent Claim
35 words
A wall shear stress sensor as claimed in claim 5 further comprising the process steps of: forming electrical contacts to the arms; and covering the arms with a passivation layer to dielectrically isolate the arms.
Claim 8
Dependent Claim
42 words
A wall shear stress sensor as claimed in claim 6 wherein the step of forming electrical contacts to the arms includes contacting the arms through a back surface of the first silicon wafer opposite the front surface of the first silicon wafer.
Claim 9
Dependent Claim
31 words
A wall shear stress sensor as claimed in claim 1 wherein the readout means includes electrical interconnects coupled to the plate and piezoresistive supporting arms in an electrical bridge circuit configuration.