US Patent # 5,955,659
Link to USPTO
Gupta, et. al. (MIT)
A fluid property sensor includes a substrate having a first electrode
thereon, and a flexible member adjacent the substrate and the first
electrode wherein the flexible member includes a second electrode. A
signal generator generates a predetermined electrical signal across
the first and second electrodes so that an electrostatic force is
generated between the first and second electrodes and so that said
flexible member deflects a predetermined distance. A measuring circuit
measures an interval of time between the generation of the predetermined
electrical signal and the deflection of the flexible member to the
predetermined distance and determines a property of a fluid adjacent
the flexible member based on the interval of time. For example, the sensor
can be used to determine a viscosity of the fluid. Alternately, the fluid
can be a compressible gas, and the sensor can be used to determine a
pressure of the gas. Related methods are also discussed.
US Patent # 6,542,829
Link to USPTO
Gupta (Coventor, Inc.)
Accurate characterization of microelectromechanical systems (MEMS) geometry
is critical for device design and simulation, for material property
extraction, and for post-fabrication trimming. According to the present
embodiment, a method for characterizing parameters describing MEMS
structures resulting from the fabrication process or process variations
is presented. According to the prefered embodiment, experimentally obtained
natural frequencies are compared with numerical simulations to identify
unknown values of structural parameters or parameter variations. Further,
the prefered embodiment teaches how electrostatically-driven laterally
resonant comb-drive MEMS test structures with prescribed changes in spring
width are used to characterize systematic variations in process offsets
and sidewall angles. The disclosed technique is both in-situ and non-destructive.
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