Pre-collapsed cMUT Cell Annular Design for Linear Coupling
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Solution Overview
Problem
Conventional capacitive micro-machined ultrasound transducers (cMUT) operate in an uncollapsed mode, leading to non-linear behavior and bias voltage-dependent coupling, which limits their performance and efficiency in transducing ultrasound waves.
Innovation Solution
A pre-collapsed cMUT cell design featuring an annular-shaped collapsed region increases the high-coupling area by moving the active transduction zone away from the center, effectively doubling the transduction zone without reducing its width, thereby enhancing transduction efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional uncollapsed cMUT cell is used, then the device structure is simple, but the coupling is bias voltage-dependent and non-linear
Solution Approach 1:
The membrane is divided into distinct functional regions: a collapsed annular region providing high coupling and a non-collapsed outer region maintaining structural support. This segmentation allows the device to achieve linear, bias-voltage-independent coupling in the active region while maintaining overall structural integrity.
Solution Approach 2:
Different regions of the membrane are given different structural properties - the inner annular region is collapsed to substrate contact for optimal coupling, while the outer region remains non-collapsed for mechanical support. This local differentiation resolves the contradiction by optimizing each region for its specific function.
2Area of stationary object
If the membrane is collapsed to the substrate, then the coupling area increases, but the transduction zone width may be reduced
Solution Approach 1:
The collapsed region is configured as an annular ring rather than a central circular region, effectively utilizing the radial dimension to maximize coupling area while preserving adequate transduction zone width in the circumferential direction. This dimensional approach allows both parameters to be optimized simultaneously.
Solution Approach 2:
The annular collapsed region creates a curved geometric configuration that maximizes the coupling area while maintaining sufficient width for the transduction zone. The curved annular shape allows the membrane to achieve optimal contact with the substrate across a larger area without compromising the dimensional integrity of the active transduction region.
3Reliability
If a pre-collapsed cMUT cell is used, then the coupling is bias voltage-independent and linear, but the manufacturing process becomes more complex
Solution Approach 1:
The membrane is pre-collapsed to the substrate during the manufacturing process to establish the desired annular collapsed region before final device assembly. This preliminary action ensures that the linear, bias-voltage-independent coupling characteristic is built into the device structure, eliminating the need for complex post-manufacturing adjustments.
Solution Approach 2:
The manufacturing process utilizes controlled parameter changes (such as bias voltage application during fabrication) to achieve the pre-collapsed state. By adjusting electrical, mechanical, or thermal parameters during manufacturing, the membrane is transformed into the desired annular collapsed configuration, enabling linear operation without excessive manufacturing complexity.
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 annular-shaped collapsed region increases the effective coupling of the transducer cell, improving its performance by creating two transduction zones instead of one, resulting in enhanced transduction efficiency and increased coupling area.
Implementation Method 1
The mechanism by which this receiving or transmitting of waves occurs is called electromechanical coupling, or briefly, 'coupling.'
Implementation Method 2
Conversely, an electrical signal applied to the electrodes causes the membrane to move or vibrate and thereby transmitting ultrasound waves.
Implementation Method 3
the variation in the capacitance between the electrodes can be detected. Thereby the ultrasound waves are transformed into a corresponding electrical signal.
Data Source
AI summary
The present invention relates to a pre-collapsed capacitive micro-machined transducer cell (10) comprising a substrate (12) comprising a first electrode (16), a membrane (14) comprising a second electrode (18), wherein the cell has an outer region (22) where the membrane (14) is mounted to the substrate (12) and an inner region (20) inside or surrounded by the outer region (22), wherein the membrane (14) is collapsed to the substrate (12) in a first collapsed annular-shaped region (24) located within the inner region (20).