Floating Element Shear Sensor Array
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Solution Overview
Problem
Existing MEMS floating element sensors lack sensitivity and robustness at high shear stress levels and are sensitive to pressure gradients, limiting their effectiveness in measuring shear stress in turbulent boundary layers and other applications where shear stresses exceed 4 Pa.
Innovation Solution
A micromachined floating element array sensor with a solid support, featuring a movable center shuttle, variable capacitors, surface bumps, and folded beams, calibrated to determine sensitivity to streamwise pressure gradients, providing improved sensitivity and robustness through differential capacitive sensing and a capacitance to digital converter for accurate shear stress measurement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If MEMS floating element sensors are used for shear stress measurement, then spatial and temporal resolution are improved, but sensitivity to pressure gradients and robustness at high shear levels deteriorate
Solution Approach 1:
The sensor is divided into multiple independent floating element sensors arranged in an array on a single chip. Each element can be independently addressed and measured, allowing spatial resolution while maintaining the robustness of individual elements. The array configuration enables measurement at multiple locations simultaneously.
Solution Approach 2:
Multiple copies of the floating element sensor are fabricated on a single chip using MEMS techniques. This allows replication of the sensitive measurement element while distributing the measurement function across multiple identical units, improving both resolution and reliability through redundancy.
2Adaptability or versatility
If MEMS floating element sensors operate at high shear stress levels, then measurement range is improved, but sensitivity and linearity deteriorate
Solution Approach 1:
The patent employs multiple floating element sensors with different calibration ranges within the same array. Some elements are optimized for low shear levels while others are calibrated for high shear levels, allowing the system to maintain sensitivity and linearity across the entire measurement range by selecting the appropriate element for each measurement condition.
Solution Approach 2:
The sensor array includes elements with different physical parameters (such as varying shuttle masses, spring constants, or capacitor geometries) that allow each element to respond linearly to different ranges of shear stress. This enables the system to cover a wide measurement range while maintaining measurement precision at any given shear level.
3Device complexity
If single-point shear stress measurement is used, then device simplicity is maintained, but spatial resolution deteriorates
Solution Approach 1:
The measurement system is segmented into multiple independent sensing elements arranged in an array, where each element provides shear stress measurement at a specific location. This segmentation enables spatial resolution of shear stress distributions while maintaining the simplicity of individual element design and readout electronics.
Solution Approach 2:
Multiple floating element sensors are integrated onto a single chip substrate, combining multiple measurement functions into one compact device. This merging approach provides spatially resolved measurements while maintaining a simple single-chip architecture that can be read out using conventional electronics.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The sensor array achieves high sensitivity and accuracy in measuring shear stress, correcting for pressure gradient effects, and maintaining functionality even with partial element failure, suitable for applications in aerospace, automotive, and naval industries.
Implementation Method 1
The motion may be detected using capacitance change, piezoresistance, or optical methods
Implementation Method 2
Under the influence of hydrodynamic forces, this 'floating element' experiences a lateral deflection
Implementation Method 3
a series of folded beams
Data Source
AI summary
The present disclosure relates to shear sensor arrays. In particular, the present disclosure relates to a floating element shear stress sensor array on a chip that is calibrated to high shear levels and is calibrated to determine the sensitivity to streamwise pressure gradients.