CMUT Membrane Cavity Structure for Sensitive Intravascular Sensing
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Solution Overview
Problem
The fabrication of capacitive micromachined ultrasonic transducers (CMUTs) for medical devices faces challenges in performance, yield, and reliability, particularly due to issues with bonding and pressure distribution during the manufacturing process, which affect the integration of sensors and data acquisition efficiency.
Innovation Solution
A CMUT design and fabrication method involving a silicon-on-insulator (SOI) wafer bonded to a CMOS wafer with peripheral walls defining a cavity, where the membrane is bonded only to these walls while leaving posts and interior walls unbonded, allowing for a larger active area and reduced manufacturing defects through controlled pressure distribution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If the membrane is bonded to all walls and posts in the cavity, then the structural stability is improved, but the active sensing area is reduced and manufacturing defects increase
Solution Approach 1:
The cavity structure is segmented into peripheral walls and interior posts/walls. The membrane is selectively bonded only to the peripheral walls, while the interior posts and walls remain unbonded to preserve the active sensing area. This segmentation allows the structure to maintain stability through peripheral support while maximizing the functional membrane area in the center.
Solution Approach 2:
Different regions of the cavity structure are assigned different bonding properties. The peripheral walls have bonding surfaces for membrane attachment, while the interior posts and walls are designed without bonding surfaces. This local differentiation optimizes both structural stability at the boundaries and active sensing area in the interior region.
2Measurement precision
If the membrane area is increased to improve sensitivity, then the sensing performance is improved, but the pressure distribution during fabrication becomes uncontrolled and reliability decreases
Solution Approach 1:
The support structure is segmented into peripheral walls that provide controlled bonding points and interior posts that maintain pressure distribution. This segmentation allows the large membrane area needed for sensitivity while controlling the pressure distribution through multiple discrete support points during fabrication.
Solution Approach 2:
The interior posts and walls act as intermediaries between the large membrane area and the substrate. They provide distributed support points that control pressure distribution during fabrication, enabling the use of larger membrane areas for improved sensitivity without compromising fabrication reliability.
3Area of moving object
If smaller posts and interior walls are used to maximize active area, then the membrane area is increased, but the manufacturing precision requirements increase
Solution Approach 1:
Instead of making the peripheral walls very thin to maximize area, the invention inverts the approach by making the peripheral walls sufficiently wide to provide stable bonding, while minimizing the interior posts and walls. This inversion allows reliable manufacturing of the bonding regions while still achieving maximum active area.
Solution Approach 2:
Different regions have different dimensional characteristics optimized for their function. The peripheral walls have larger dimensions for stable bonding and manufacturing, while the interior posts and walls have smaller dimensions to maximize active area. This local quality differentiation balances manufacturing precision requirements with active area maximization.
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 approach enhances the sensitivity and performance of CMUTs by maintaining a larger membrane area for sensing, reduces manufacturing defects, and enables efficient data acquisition in medical devices like guidewires and catheters.
Implementation Method 1
A silicon-on-insulator (SOI) wafer with a highly doped silicon layer on top may be bonded to the one or more peripheral walls
Implementation Method 2
Capacitive Micromachined Ultrasonic Transducers (CMUTs) that are a relatively new technology within the field of transducers. In many applications CMUTs can be used to generate ultrasonic waves and/or receive ultrasonic waves
Implementation Method 3
A silicon-on-insulator (SOI) wafer with a highly doped silicon layer on top may be bonded to the one or more peripheral walls
Data Source
AI summary
Capacitive Micromachined Ultrasonic Transducer (CMUT) device, methods of manufacture, and systems and methods of use. The CMUTs have a substrate, peripheral walls defining a boundary of a cavity, and a membrane bonded to the peripheral walls. Protruding from the substrate are posts that are enclosed by the peripheral walls. The posts contact, but are not bonded to, the membrane, forming a cavity that resonates with certain acoustic frequencies. The CMUTs are placed into a vascular system of a patient in a stent, a catheter, or other small device. The CMUTs are responsive to acoustic frequencies emitted from a device outside the body, thereby acting as sensors for various characteristics of the environment around the CMUT inside the body.