Intravascular Pressure Sensor Chips with DRIE Stress-Resistant Structures
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Solution Overview
Problem
Existing intravascular pressure sensors fabricated using mechanical saws are prone to damage and stress, leading to performance degradation and premature failure due to external forces, and are limited to rectangular outlines, complicating their integration into flexible guidewires.
Innovation Solution
Employ deep reactive-ion etching (DRIE) combined with photolithography to create non-rectangular sensor chips with internal cutouts and cantilevered structures, allowing for precise, stress-resistant designs suitable for guidewires, enabling compact mounting and improved wire connections.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If mechanical saws are used to fabricate pressure sensors, then manufacturing is fast and efficient, but the sensors are prone to damage and stress leading to performance degradation
Solution Approach 1:
The patent replaces the mechanical sawing process with a chemical etching process (DRIE - Deep Reactive Ion Etching) to fabricate the sensor chip. This substitution eliminates the mechanical contact and associated stress that causes sensor damage, while maintaining manufacturing efficiency through batch processing capability.
Solution Approach 2:
The patent changes the fabrication method from mechanical cutting to chemical etching, fundamentally altering the manufacturing parameter from mechanical force to chemical reaction. This parameter change enables precise control of the etching depth and pattern while avoiding mechanical stress on the sensor elements.
2Length of moving object
If wafer is thinned to less than 100 micrometers for guidewire mounting, then the device can be mounted within coronary guidewire, but the thin wafer is difficult to handle and subject to breakage
Solution Approach 1:
The patent performs the wafer thinning operation before the sensor fabrication and assembly steps, while the wafer is still supported by the full-thickness substrate. This preliminary action allows the wafer to be thinned to the required thickness without subsequent handling risks, as the thin section is created first and then protected during later processing steps.
Solution Approach 2:
The patent maintains the full-thickness wafer as a supporting structure during the thinning and fabrication processes, providing mechanical strength and protection to the emerging thin sensor section. This cushioning effect prevents breakage during handling while the thin profile is being created.
3Productivity
If diamond saw dicing is used to cut the wafer into sensor chips, then the process is fast and efficient, but only simple rectangular device outlines can be produced
Solution Approach 1:
The patent replaces the mechanical diamond saw dicing process with chemical etching (DRIE) to define the sensor chip outlines. This substitution enables complex, non-rectangular shapes to be created with high precision, as the chemical etching can follow photolithographically defined patterns of any geometry without the geometric constraints of mechanical cutting tools.
4Measurement precision
If pressure sensor is mounted in guidewire, then pressure measurement is achieved, but external stress from bending or thermal expansion produces undesirable pressure artifacts
Solution Approach 1:
The patent segments the sensor chip into a thin sensing section that is mechanically isolated from the guidewire structure. This segmentation is achieved by thinning the wafer to create a suspended or cantilevered sensor section that does not directly contact the guidewire, thereby preventing stress transmission from guidewire bending or thermal expansion to the pressure sensing elements.
Solution Approach 2:
The patent introduces an intermediary structure (the thinned wafer section or mounting architecture) that decouples the pressure sensor from the guidewire body. This intermediary acts as a mechanical buffer that allows the sensor to measure pressure without being subjected to the external stresses experienced by the guidewire during catheterization procedures.
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
DRIE processing enhances sensor durability and integration into guidewires by reducing stress-induced artifacts, facilitating compact and efficient pressure sensing with improved manufacturing yield and reduced vulnerability to damage.
Implementation Method 1
Deep reactive-ion etching (DRIE) is a highly anisotropic etch process for creating deep, steep-sided holes and trenches in solid-state device wafers
Implementation Method 2
The cantilevered portion includes a diaphragm comprising at least one piezoresistive element for sensing pressure
Data Source
AI summary
An intravascular pressure sensor assembly is disclosed herein that is produced in part using photolithography and DRIE solid-state device production processes. Using DRIE production processes facilitates a number of features that could not be readily incorporated in sensor chips fabricated using mechanical saws. In accordance with a first feature, sensor chips are created with non-rectangular outlines. The sensor chip includes a widened portion that substantially abuts an inner wall of a sensor housing, and a cantilevered portion that is relatively narrow in relation to the widened portion. The non-rectangular outline of the sensor chip is formed using photolithography in combination with DRIE processing. In accordance with another feature, the sensor chip is positioned width-wise in the housing, thereby reducing a required length for the housing. In accordance with yet another feature, the sensor chip comprises one or more cutouts for receiving signal wires for connection to signal lead lines on the sensor chip. The outline of the sensor chip and the cutouts are formed using photolithography in combination with DRIE processing.