Three-Electrode CMUT Cell for Miniaturized Ultrasound Catheters
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Solution Overview
Problem
Capacitive micromachined ultrasonic transducer (CMUT) arrays face challenges in miniaturization and performance due to the large dimensions and parasitic effects of discrete high-voltage components used in bias-T filters, which limit their application in ultrasound catheters and affect imaging capabilities.
Innovation Solution
The integration of a third electrode within the CMUT cell, capacitively coupled to the other electrodes through a dielectric layer, allows for an integrated RC filter and efficient high-voltage supply, reducing the need for external discrete components and minimizing the impact of parasitic effects, while using a high-k dielectric layer to maintain stability and prevent leakage currents.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If discrete high-voltage components are used in bias-T filters for CMUT arrays, then high-voltage supply is achieved, but device size increases and parasitic effects occur
Solution Approach 1:
The patent merges the bias-T filter components with the CMUT cell structure by integrating the high-voltage coupling capacitor and high-impedance resistor directly into the transducer element. This consolidation eliminates the need for separate discrete components, thereby reducing overall device size while maintaining high-voltage supply functionality and stability.
Solution Approach 2:
The CMUT cell structure is designed to serve multiple functions: it acts as both the ultrasonic transducer element and the housing for the bias-T filter components. The cell floor and surrounding structures are utilized to provide electrical isolation and component mounting, allowing the same structure to fulfill both transducer and filter housing roles.
2Reliability
If discrete high-voltage components are used in bias-T filters, then high-voltage supply is achieved, but parasitic effects limit performance
Solution Approach 1:
By integrating the bias-T filter components directly into the CMUT cell, the patent minimizes the length of interconnect traces and reduces the number of discrete component connections. This consolidation significantly reduces parasitic inductance and resistance that would otherwise be introduced by separate components and their interconnections, thereby improving signal integrity and transducer performance.
3Reliability
If discrete high-voltage components are used, then high-voltage coupling is achieved, but miniaturization benefits are eliminated
Solution Approach 1:
The patent integrates the high-voltage coupling capacitor and high-impedance resistor directly into the CMUT cell structure, eliminating the need for separate discrete components. This merging approach maintains effective high-voltage coupling while achieving miniaturization, as the filter components share the same physical space as the transducer elements rather than requiring additional external components.
4Reliability
If discrete high-voltage components are used, then bias-T filtering is achieved, but implementation in ultrasound catheters becomes difficult
Solution Approach 1:
By consolidating the bias-T filter components within the CMUT cell structure itself, the patent creates a highly integrated transducer element that is suitable for miniaturized applications such as ultrasound catheters. This integration eliminates the need for bulky external filter components, making the overall device more compact and easier to implement in constrained catheter-based applications.
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 solution enables a more compact and efficient high-voltage supply for CMUT arrays, improving miniaturization and reducing the risk of breakdown, thereby enhancing the performance and safety of ultrasound imaging systems, particularly in applications where 3D imaging is not feasible.
Implementation Method 1
The third electrode B is embedded into the cell floor 130 and is capacitively coupled to the first electrode S1 and to the second electrode S2 through a dielectric layer 131
Implementation Method 2
insulated on its cavity-facing surface with an additional insulating layer 132
Implementation Method 3
using a high-k dielectric layer to maintain stability and prevent leakage currents
Implementation Method 4
For transmission the capacitive charge applied to the electrodes is modulated to vibrate/ move the diaphragm (membrane) of the device and thereby transmit a sound wave
Implementation Method 5
The reflected sound wave causes vibrations of the membrane, modulating the capacitance between two electrodes of the CMUT transducer, thereby generating an electric signal
Data Source
Figure 1
Figure 2~3(c)
Figure 4(a)~4(b)
AI summary
A capacitive micromachined ultrasonic transducer (CMUT) cell comprising three electrodes: a first electrode coupled to a cell membrane; a second electrode embedded into a cell floor opposing the first electrode and separated therefrom by a gas or vacuum cavity; and a third electrode opposing the second electrode on the cavity side, wherein a dielectric layer is sandwiched between the second electrode and the third electrode to create a capacitive relation between the second electrode and the third electrode. The three electrode CMUT cell provides an ultrasound transducer with two actively driven (controlled) electrodes.