Capacitive Strain Sensor for Balloon Catheters
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Solution Overview
Problem
Existing strain sensors are limited in measuring larger strains in flexible materials with low hysteresis and high accuracy, particularly in balloon catheters, due to their complexity and rigidity, which affects the precision of balloon diameter measurement during medical procedures.
Innovation Solution
A capacitive strain sensor design featuring two flat, electrically conductive conductor elements that are laterally displaceable, connected via spring elements, allowing for precise measurement of extensions and compressions by changing overlap, thereby enhancing sensitivity and linearity without significantly influencing the mechanical properties of the measured material.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional strain gauges or capacitive sensors are used to measure balloon diameter, then measurement precision is improved, but device complexity and installation space requirements increase
Solution Approach 1:
The patent combines the sensing function and structural support function into a single integrated element. The spring element serves both as the sensing element that detects diameter changes through capacitance variation and as the structural support for the conductor elements, eliminating the need for separate sensing components and reducing overall device complexity
Solution Approach 2:
The spring element performs multiple functions simultaneously: it acts as a mechanical spring for structural support, as a sensing element that translates diameter changes into conductor element displacement, and as a mounting structure for the conductor elements. This multi-functionality reduces the number of components needed in the sensor system
2Measurement precision
If sensing elements are made significantly thinner than the structure to be measured, then measurement precision is improved, but manufacturing difficulty and cost increase
Solution Approach 1:
The patent employs thin film conductor elements deposited on flexible substrate materials that can conform to the balloon surface. These thin film structures provide the necessary sensitivity for precise measurement while maintaining manufacturability through standard thin film deposition techniques and flexible material processing
Solution Approach 2:
The sensor utilizes composite structures combining conductive materials with flexible substrate materials. This composite approach allows the sensing element to be both thin enough for high precision measurement and structurally sound enough for practical manufacturing and application on medical devices
3Adaptability or versatility
If the sensor must withstand multiaxial strain of up to 30%, then adaptability to balloon expansion is improved, but measurement repeatability deteriorates due to viscoelastic properties
Solution Approach 1:
The patent employs a dynamic spring element design that can reversibly deform under multiaxial strain conditions. The spring element's elastic properties allow it to accommodate balloon expansion up to 30% while maintaining a consistent mechanical response that enables repeatable measurements across multiple expansion and deflation cycles
Solution Approach 2:
The sensor system is designed to accommodate changes in mechanical parameters during balloon expansion. The spring element's stiffness and geometric configuration are optimized to maintain linear capacitance-strain relationships even when subjected to varying multiaxial strain conditions, ensuring measurement repeatability across the full range of balloon diameters
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 sensor achieves good reproducibility for larger extensions, up to two-digit percentage ranges, with enhanced sensitivity and linearity, allowing for precise measurement of balloon diameter changes during medical procedures without affecting the mechanical properties of the catheter.
Implementation Method 1
the two conductor elements, proceeding from a first condition, being displaceable into a second condition, wherein an overlap formed by the two conductor elements in the first condition is larger or smaller than in the second condition
Data Source
AI summary
A strain sensor for capacitive strain measurement has a flat and electrically conductive first conductor element and a flat and electrically conductive second conductor element. The two conductor elements oppose one another and are laterally displaceable relative to one another, so that the two conductor elements, proceeding from a first condition, may be displaced relative to one another into a second condition. An overlap between the two conductor elements is different in the first condition from the second condition. First and second springs attach the conductor elements to first and second attaching regions of the strain sensor. The first attaching region is disposed at a first reference point of a body to be measured, and/or the second attaching region is disposed at a second reference point of the body to be measured.