PMUT Slotted Membrane Reduces Stress Sensitivity
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Piezoelectric micromachined ultrasonic transducers (pMUTs) face challenges in achieving stable resonance modes with low stress sensitivity, as existing designs are sensitive to residual stress and fabrication variations, leading to phase and amplitude errors in ultrasound signals.
Innovation Solution
A pMUT design featuring a clamped membrane partially released into mechanically coupled tapered cantilevers, with adjustable resonance frequency through varying the number of slices and connecting rings, reducing stress sensitivity and enhancing acoustic performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If the membrane is fully clamped at its boundary, then the structural integrity is maintained, but the resonance frequency becomes very sensitive to in-plane residual stress
Solution Approach 1:
The membrane is divided into multiple identical tapered cantilevers that are mechanically coupled together. This segmentation reduces the sensitivity to residual stress while maintaining structural integrity through the coupling mechanism. The cantilevers are sliced from the membrane and connected by concentric rings, allowing stress relief while preserving overall stability.
Solution Approach 2:
The design transitions from a static fully-clamped membrane to a dynamic partially-released structure with tapered cantilevers. This dynamic configuration allows the membrane to better accommodate stress variations while maintaining controlled resonance behavior through the mechanical coupling of cantilevers.
2Manufacturing precision
If the membrane is released into individually-defined cantilevers, then the stress sensitivity is reduced, but small dimension variations cause different resonance frequencies resulting in phase and amplitude errors
Solution Approach 1:
Multiple tapered cantilevers are mechanically coupled together using concentric rings to function as a unified resonating structure. This merging ensures that all cantilevers resonate at the same frequency despite small dimension variations, preventing phase and amplitude errors while maintaining reduced stress sensitivity.
Solution Approach 2:
The cantilevers are arranged in a radial pattern around a central axis, creating a rotationally symmetric structure. This dimensional arrangement ensures that all cantilevers experience equivalent mechanical conditions and resonate at the same frequency, eliminating phase and amplitude inconsistencies.
3Adaptability or versatility
If the membrane dimensions are changed to adjust resonance frequency, then the frequency can be tuned, but the basic design parameters must be altered
Solution Approach 1:
The resonance frequency is adjusted by changing the number of cantilever slices and the number of connecting rings, rather than altering the basic membrane dimensions. This parameter change approach allows frequency tuning while maintaining the same fundamental membrane size and shape, reducing design complexity.
Solution Approach 2:
By dividing the membrane into a variable number of cantilever slices, the resonance frequency can be precisely controlled. The segmentation allows independent adjustment of frequency characteristics without changing the overall membrane dimensions, providing adaptability while maintaining design simplicity.
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 design achieves reduced stress sensitivity, increased acoustic sensitivity, and adjustable resonance frequency without altering membrane dimensions, resulting in improved displacement and acoustic output.
Implementation Method 1
Piezoelectric micromachined ultrasonic transducers (pMUTs) are MUTs that use a piezoelectric layer for electro-mechanical transduction
Implementation Method 2
A typical pMUT is a multilayer membrane structure that is excited into flexural vibration using piezoelectric actuation. Sound is emitted from the tube when the membrane vibrates
Implementation Method 3
the tube may be designed as an acoustic resonator to improve acoustic performance of the pMUT
Data Source
Figure 1~2
Figure 3~4
Figure 5(a)~5(b)
AI summary
A piezoelectric micromachined ultrasonic transducer (PMUT) device includes a substrate having an opening therethrough and a membrane attached to the substrate over the opening. A portion of the membrane that overlies the opening is divided into a plurality of cantilevers that are mechanically coupled so that the cantilevers resonate at a common frequency.