CMUT Array Membrane for Immersion Crosstalk Reduction
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Capacitive micromachined ultrasonic transducers (CMUTs) experience significant acoustic crosstalk due to dispersive guided modes in the fluid-solid interface, degrading performance in immersion applications such as medical imaging and high-intensity focused ultrasound (HIFU) treatments, and existing methods have not effectively reduced this crosstalk.
Innovation Solution
A CMUT array design with a membrane formed in the separation region between adjacent elements, creating a periodic arrangement that impedes the propagation of the dispersive guided mode, specifically using a vacuum gap and materials like silicon nitride or silicon oxide for the membrane, which reduces crosstalk without affecting the static behavior of the cells.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If CMUTs operate in immersion, then they can perform medical imaging and HIFU treatment functions, but acoustic crosstalk between neighboring elements degrades performance
Solution Approach 1:
The array is segmented into isolated elements by introducing separation regions between neighboring CMUT elements. These separation regions act as acoustic barriers that divide the continuous acoustic field into discrete element zones, preventing the dispersive guided mode from propagating between elements while maintaining immersion operation capability
Solution Approach 2:
Separation regions serve as intermediary structures positioned between adjacent CMUT elements. These regions mediate the acoustic interaction by providing a controlled interface that blocks the harmful dispersive guided mode propagation while allowing each element to function independently in the immersion medium
2Object-affected harmful factors
If separation regions are introduced between array elements, then crosstalk is reduced, but device complexity increases
Solution Approach 1:
The separation regions are implemented as thin film structures that can be integrated into the CMUT fabrication process. These thin film barriers provide effective acoustic isolation without adding significant structural complexity or volume to the array, maintaining manufacturability while reducing crosstalk
Solution Approach 2:
The separation regions modify the acoustic parameters at element interfaces by creating impedance mismatches that block the dispersive guided mode. By changing the physical parameters of the interface region (such as thickness, material properties, or geometry), effective crosstalk reduction is achieved without fundamentally altering the overall array architecture
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 solution effectively reduces crosstalk by approximately 10 dB, maintaining acoustic pressure and improving angular response and range resolution, while minimizing the effective element aperture and ringdown time, thus enhancing the performance of CMUT arrays in medical applications.
Implementation Method 1
The membrane reduces crosstalk between the adjacent array elements, where the crosstalk is a dispersive guided mode of an ultrasonic signal from the CMUT propagating in a fluid-solid interface of the CMUT array
Data Source
AI summary
A reduced crosstalk capacitive micromachined ultrasonic transducer (CMUT) array is provided. The CMUT array has at least two CMUT array elements deposited on a substrate, at least one CMUT cell in the array element, a separation region between adjacent CMUT array elements, and a membrane formed in the separation region. The membrane reduces crosstalk between adjacent array elements, where the crosstalk is a dispersive guided mode of an ultrasonic signal from the CMUT propagating in a fluid-solid interface of the CMUT array. Each cell has an insulation layer deposited to the substrate. A cell membrane layer is deposited to the insulation layer, where the cell membrane layer has a vacuum gap therein. The cells further have an electrode layer deposited to a portion of the membrane layer, and a passivation layer deposited to the electrode layer, the cell membrane layer and to the insulation layer.