Miniature Fiber Optic Pressure Sensor for Catheter
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Solution Overview
Problem
Current Fabry-Perot pressure sensors for catheter tip applications are prone to moisture drift due to adhesive swelling and are sensitive to temperature changes, which affects their accuracy and stability, especially in medical environments where they are exposed to humidity and varying temperatures.
Innovation Solution
A miniature fiber optic pressure sensor design with a reduced adhesive requirement for bonding the optical fiber to the Fabry-Perot chip, using techniques like excimer laser drilling and silicon-on-insulator wafers to minimize moisture-induced drift and incorporating thermal compensation layers to mitigate temperature sensitivity, along with protective coatings to prevent etching in water-based solutions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If adhesive is used to bond the optical fiber to the Fabry-Perot chip, then the fiber is securely attached, but moisture-induced adhesive swelling causes sensor drift
Solution Approach 1:
The patent removes the adhesive bonding step entirely by using a mechanical retention structure. The optical fiber is held in place by a recessed cavity with a retaining ring that physically secures the fiber through friction and geometric constraint, eliminating the need for adhesive and thus preventing moisture-induced swelling and drift.
Solution Approach 2:
The patent introduces a retaining ring as an intermediary component between the optical fiber and the Fabry-Perot chip. This retaining ring serves as a mechanical mediator that provides secure attachment through friction and geometric retention, replacing the chemical bonding function of adhesive with a physical retention mechanism that is immune to moisture.
2Volume of moving object
If the catheter size is reduced for less invasive procedures, then patient comfort and safety improve, but the pressure sensor must be made smaller which limits available components
Solution Approach 1:
The patent combines multiple functions into the Fabry-Perot chip itself: the pressure sensing diaphragm, the Fabry-Perot cavity formation, and the optical fiber retention structure are all integrated into a single miniaturized chip. This consolidation eliminates the need for separate mounting components and reduces overall sensor size while maintaining functionality.
Solution Approach 2:
The patent employs a nested structure where the optical fiber is inserted into a recessed cavity within the chip, and the retaining ring is positioned within the same cavity structure. This nested arrangement maximizes space utilization and minimizes the overall footprint of the sensor assembly, enabling catheter miniaturization.
3Measurement precision
If electrical pressure sensors are used at the catheter tip, then accurate pressure measurement is achieved, but they are sensitive to electromagnetic noise in MRI and electrosurgery environments
Solution Approach 1:
The patent replaces the electrical sensing mechanism with an optical sensing system. The Fabry-Perot cavity uses light interference patterns to measure pressure-induced diaphragm displacement, substituting electrical signals with optical signals that are immune to electromagnetic interference from MRI and electrosurgery equipment.
4Measurement precision
If electrical pressure sensors are used, then pressure measurement capability is provided, but they suffer from sensitivity to moisture drift due to conductivity changes in surrounding media
Solution Approach 1:
The patent replaces the electrical measurement mechanism with an optical measurement system. The Fabry-Perot cavity uses light wavelength shifts caused by pressure-induced diaphragm movement to determine pressure, substituting electrical conductivity measurements with optical interference measurements that are unaffected by moisture or changes in the electrical properties of surrounding biological media.
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 provides a robust, low-cost pressure sensor with high fidelity measurements that is less sensitive to moisture and temperature fluctuations, ensuring reliable performance in medical applications and reducing the risk of sensor drift and thermal shifts.
Implementation Method 1
Fabry-Perot based pressure sensors are then considered as those having the best potential to suit the needs for catheter tip pressure measurement
Implementation Method 2
Some initial design such as the one described by Matsumoto et al., 'The development of a fibre optic catheter tip pressure transducer', Journal of Medical Engineering & Technology, Vol. 2, no. 5 (1978) were based on the variation of the light intensity induced by various mechanism
Implementation Method 3
the miniature fiber optic sensor comprises a Fabry-Perot chip bonded to an optical fiber
Implementation Method 4
using techniques like excimer laser drilling
Data Source
AI summary
The invention provides a miniature robust fiber optic pressure sensor. The miniature fiber optic sensor comprises a Fabry-Perot chip bonded to an optical fiber. The invention provides a new sensor design that reduces the amount of adhesive required to bond the optical fiber to the Fabry-Perot sensor such that the sensor is less sensitive to moisture. The invention also provides manufacturing methods of the sensor comprising a method based on etching and a method based on using an excimer laser. The invention also provides a chip design that renders the chip less sensitive to thermal changes. The invention also provides a chip design in which a sensor diaphragm has a well-defined thickness. The invention also provides a chip design that protects the chip from etching.