Composite Catheter Shaft Variable Stiffness via Mechanical Deformation

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Solution Overview

Problem

Existing catheter shafts face challenges in achieving variable flexibility along their length, making them difficult to manufacture using continuous extrusion or co-extrusion processes and prone to kinking due to abrupt changes in stiffness, while also requiring a balance between pushability and torqueability.

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.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of operation

If a catheter shaft has variable flexibility along its length, then the catheter can be pushed through blood vessels with better pushability and torqueability, but the catheter becomes difficult to manufacture using continuous extrusion or co-extrusion processes

Engineering Contradiction:

Improvepushability and torqueabilityVSAvoidcontinuous extrusion manufacturing

Core Design Contradiction:

Ease of operationVSEase of manufacture

Solution Approach 1:

The catheter shaft's flexibility parameter is varied along its length by applying different degrees of mechanical deformation to different segments. The proximal section undergoes greater deformation to increase stiffness for pushability, while the distal section maintains lesser deformation for flexibility to navigate vessels, achieving variable properties through controlled parameter changes during manufacturing

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The catheter shaft is divided into multiple segments along its length, with each segment undergoing different mechanical deformation to achieve different stiffness characteristics. This segmentation allows the proximal portion to be stiffer for pushability while the distal portion remains more flexible for navigation, resolving the manufacturing complexity by treating segments differently

Inventive Principle:

Principle #1Segmentation

2Adaptability or versatility

If a catheter shaft has abrupt changes in stiffness along its length, then the catheter can transition between rigid and flexible sections, but the catheter becomes prone to kinking due to stress concentrations

Engineering Contradiction:

Improvevariable flexibilityVSAvoidkinking resistance

Core Design Contradiction:

Adaptability or versatilityVSReliability

Solution Approach 1:

The stiffness parameter changes gradually along the catheter shaft length through controlled mechanical deformation, transitioning from a stiffer proximal section to a more flexible distal section. This gradual parameter change avoids abrupt stiffness transitions that cause stress concentrations and kinking, while still achieving the desired variable flexibility profile

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The catheter shaft exhibits dynamic stiffness characteristics where the stiffness varies continuously along its length rather than being discrete. The proximal section is stiffer for pushability while the distal section is more flexible for navigation, creating a dynamic stiffness gradient that prevents kinking by distributing stress more evenly throughout the structure

Inventive Principle:

Principle #15Dynamics

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, reducing kinking and stress concentrations, while maintaining necessary pushability and torqueability, by using mechanical deformation to create regions of delamination and burnished surfaces within the catheter shaft, resulting in a consistent and controlled reduction in bending stiffness.

Implementation Method 1

a segment is mechanically deformed to have reduced stiffness

Methodology Applied

Scientific EffectMechanical deformation: Deformation

Implementation Method 2

creating regions of delamination and burnished surfaces within the catheter shaft

Methodology Applied

Scientific EffectDelamination:

Implementation Method 3

creating regions of delamination and burnished surfaces within the catheter shaft

Methodology Applied

Scientific EffectBurnishing:

Data Source

PatentUS8303569B2Composite laminated catheter with flexible segment and method of making same

Publication Date: 2012.11.06 MEDTRONIC VASCULAR INC

AI summary

A medical catheter including a composite laminated shaft having a longitudinal segment that is mechanically deformed to have reduced and varying stiffness. A method of making the catheter is also disclosed.