Variable Stiffness Catheter via Braid Pitch Segmentation
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Solution Overview
Problem
Existing catheter shafts face challenges in achieving variable flexibility along their length, making it difficult to balance pushability, torqueability, and flexibility, especially in manufacturing processes like continuous extrusion and co-extrusion, and irradiated variable-stiffness catheters have limitations in material choice and control.
Innovation Solution
A composite laminated catheter shaft with an elongate flexible liner, a flexible jacket, and a reinforcement layer, where a segment is mechanically deformed to have reduced stiffness, allowing for continuous manufacturing and improved flexibility profiles without assembling multiple components or using irradiated materials.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a support member with woven reinforcement or coiled filament is embedded in the catheter shaft to provide rigidity, then pushability and torqueability are improved, but flexibility is reduced
Solution Approach 1:
The catheter shaft is designed with variable flexibility along its length, having a more flexible distal section and a stiffer proximal section. This is achieved by varying the braid pitch of the reinforcement layer - closer braid pitch in the proximal section for rigidity, and wider braid pitch in the distal section for flexibility. This local variation allows different segments to have different mechanical properties optimized for their specific functions.
Solution Approach 2:
The catheter shaft is divided into discrete tubular portions, each with different performance characteristics. The proximal portion has a tighter braid pitch for rigidity and pushability, while the distal portion has a wider braid pitch for flexibility and ease of navigation. This segmentation allows each section to be optimized independently for its specific operational requirements.
2Force
If the catheter shaft is made rigid to transmit longitudinal forces from proximal to distal end, then pushability is improved, but the ability to navigate bends in blood vessels is reduced
Solution Approach 1:
The catheter shaft incorporates variable flexibility along its length, with the proximal section being stiffer for force transmission and the distal section being more flexible for navigating bends. This is achieved through varying braid pitch in the reinforcement layer, allowing the shaft to have different mechanical properties at different locations to simultaneously satisfy both force transmission and navigation requirements.
3Ease of operation
If discrete tubular portions are assembled to create variable flexibility, then flexibility profile is improved, but manufacturing complexity increases
Solution Approach 1:
Multiple discrete tubular portions with different flexibility characteristics are joined together to form a single catheter shaft. The proximal portion with tighter braid pitch is connected to the distal portion with wider braid pitch, creating a variable flexibility profile. This merging approach allows the catheter to achieve its desired flexibility characteristics while maintaining a unified structure that can be manufactured through coordinated extrusion processes.
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 enables easy manufacturing of catheters with variable stiffness, enhancing flexibility and pushability while maintaining torsional strength, reducing manufacturing complexity and material limitations, and providing a consistent reduction in bending stiffness.
Implementation Method 1
A segment of the shaft is mechanically deformed to have reduced stiffness
Data Source
AI summary
A medical catheter including a composite laminated shaft having a segment that is mechanically deformed to have reduced stiffness.