Cantilever MEMS Transducer for Low-Voltage Strain Detection

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Solution Overview

Problem

Conventional silicon resonators in MEMS transducers often require high input signals to achieve sufficient motion, resulting in unsatisfactory output signal quality and quantity due to mechanical fastening at both ends, which limits the amplification of mechanical strain at measurement locations.

Innovation Solution

The use of a cantilever beam with a leverage effect, combined with compressible or stretchable piezo-resistive elements, concentrates mechanical strain at measurement locations, allowing for improved output signal quality and high signal-to-noise ratio even with low excitation voltages, by amplifying the excitation force through adjustable mechanical dimensions and leveraging the piezo-resistive effect.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Stability of the object's composition

If conventional silicon resonators are mechanically fastened at both ends, then structural stability is improved, but mechanical strain amplification at measurement locations is limited

Engineering Contradiction:

Improvestructural stabilityVSAvoidmechanical strain amplification

Core Design Contradiction:

Stability of the object's compositionVSMeasurement precision

Solution Approach 1:

The patent transitions from a symmetric resonator structure (fastened at both ends) to an asymmetric cantilever beam structure (fastened at one end only). This asymmetry allows the free end to experience amplified mechanical strain during oscillation, enabling better measurement precision while maintaining structural stability through the fixed base.

Inventive Principle:

Principle #4Asymmetry

Solution Approach 2:

The patent introduces a lever arm dimension extending from the fixed end to the measurement location on the cantilever beam. This dimensional extension amplifies the mechanical strain at the measurement point relative to the excitation point, resolving the contradiction between structural stability and measurement precision.

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

2Speed

If high input signals are applied to conventional resonators, then sufficient motion is achieved, but output signal quality and quantity deteriorate due to limited strain amplification

Engineering Contradiction:

Improveresonator motion amplitudeVSAvoidoutput signal quality

Core Design Contradiction:

SpeedVSMeasurement precision

Solution Approach 1:

The cantilever beam structure is pre-configured with optimized dimensions and material properties to inherently amplify mechanical strain before measurement. This preliminary design ensures that even low input signals produce sufficient motion with high strain amplification at the measurement location, improving output signal quality without requiring high input signals.

Inventive Principle:

Principle #10Preliminary action

3Ease of operation

If piezo-resistive elements are used for detection, then electrical signal detection is enabled, but signal-to-noise ratio decreases without strain concentration

Engineering Contradiction:

Improveelectrical signal detection capabilityVSAvoidsignal-to-noise ratio

Core Design Contradiction:

Ease of operationVSMeasurement precision

Solution Approach 1:

The patent concentrates piezo-resistive detection elements at specific locations on the cantilever beam where mechanical strain is naturally amplified during oscillation. This local concentration of strain-sensing capability maximizes the electrical signal output from the piezo-resistive elements, improving the signal-to-noise ratio while maintaining ease of electrical signal detection.

Inventive Principle:

Principle #3Local quality

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

This configuration enhances the output signal quality and signal-to-noise ratio by concentrating mechanical strain at measurement locations, enabling effective detection of electrical signals with reduced input voltages and providing redundancy with multiple piezo-resistive elements.

Implementation Method 1

a measurement location at which a piezo-resistive element is adapted for detecting mechanical strain

Methodology Applied

Scientific EffectPiezo-resistive effect: Piezoresistive Effect

Implementation Method 2

an excitation unit adapted for exciting a motion of the cantilever beam in response to the application of an electric excitation signal impacting the cantilever beam in a contactless manner

Methodology Applied

Scientific EffectElectromechanical transduction:

Data Source

PatentUS8686714B2Electromechanical transducer and a method of providing an electromechanical transducer

Publication Date: 2014.04.01 NXP BV

AI summary

The invention relates to an electromechanical transducer (100). The electromechanical transducer (100) comprises a cantilever beam (101) and an excitation unit (102) that is adapted for exciting a motion of the cantilever beam (101). A detection unit (103) is adapted for detecting an electrical signal (iout) in response to the excited motion of the cantilever beam (101).