Monolithic Piezoresistive Force Sensor for Catheter Tips
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Solution Overview
Problem
Current force sensors for catheters and guide wires face challenges in miniaturization, high stability, simple manufacture, and low costs, as they are complex, large, and unsuitable for disposable medical devices, limiting their integration and functionality, especially in thin diameters below 3 mm.
Innovation Solution
A monolithic force sensor designed for integration into elongated devices with diameters less than 3 mm, featuring a single-part structure, piezoresistive operation, and monolithic integration of mounting elements, allowing for easy attachment and miniaturization, capable of detecting forces in the longitudinal direction with high resolution and direction accuracy, and incorporating centering elements for secure mounting.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a complex force sensor with many parts is used, then measurement accuracy can be improved, but device complexity and manufacturing cost increase significantly
Solution Approach 1:
The patent merges the force sensing function directly into the catheter tip structure by using the catheter wall itself as the sensing element. Strain gauges are integrated into the catheter wall, eliminating the need for separate sensing components. This combining approach maintains measurement accuracy while significantly reducing device complexity and part count.
Solution Approach 2:
The catheter wall serves multiple functions: it provides structural support, enables fluid flow, and acts as the force sensing element. By making the catheter wall itself the sensing component, the design achieves multi-functionality, reducing the need for additional dedicated sensing parts and simplifying the overall structure.
2Stability of the object's composition
If a large-diameter force sensor is used, then structural stability is improved, but the catheter tip becomes occluded and functionality is lost
Solution Approach 1:
The force sensing function is segmented into multiple strain gauges distributed around the catheter tip perimeter. This segmentation allows the sensing function to be achieved with minimal material volume, as the strain gauges are thin films applied to the catheter wall rather than a bulky solid sensor mass.
Solution Approach 2:
The patent uses thin-film strain gauges applied to the catheter wall to sense forces. These thin films provide the necessary structural stability for force detection while occupying minimal volume, allowing the catheter tip to remain functional and unoccluded.
3Measurement precision
If resistive elements are arranged perpendicular to the longitudinal direction, then force detection capability is provided, but the contact surface area is limited by the catheter diameter
Solution Approach 1:
The patent transitions from arranging strain gauges in a single plane perpendicular to the longitudinal axis to a three-dimensional arrangement that wraps around the catheter tip. Strain gauges are positioned at different angular positions and depths, effectively utilizing the circumferential dimension to maximize contact surface area while maintaining force detection capability.
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
Enables accurate, real-time detection of force magnitude and direction with minimal assembly costs, suitable for mass production, and integration into thin guide wires without obstructing the catheter's function, meeting hygiene and miniaturization requirements, while maintaining mechanical rigidity and low production costs.
Implementation Method 1
The force sensor is based on a piezoresistive element whose resistance changes as a function of the force applied
Data Source
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AI summary
The invention makes it possible to determine a force vector that is applied to a tip of a minimally invasive surgical instrument. The force acts upon the housing (112), is directed to the base (100), and causes a deformation there in special beam structures. Said deformation is detected by means of tension-sensitive/extension-sensitive resistors whose changes are a measure for the applied force vector. The inventive measuring element comprises special mounting elements so as to be integrated into tube-type instruments such as guiding wires, fastening zones for additional components (111), an overload protection, and a head shape that is adapted to the treatment process.