Catheter Liner Tie Layer Expansion for Hypotube Adhesion
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Solution Overview
Problem
Existing catheter liner constructions face challenges in achieving strong adhesion to metallic or polymeric hypotubes while maintaining flexibility, often requiring fluoropolymers due to tight clearance demands, which limits material options and increases the risk of delamination.
Innovation Solution
A modified catheter liner with an expandable tie layer coating that expands upon heat, providing a chemical bond to adjacent components, allowing for improved adhesion and flexibility without relying solely on fluoropolymers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a heated mandrel or balloon is used to force the liner and tie layer against the hypotube inner diameter, then adhesion is improved, but the liner is over-stretched and dimensional tolerances become tight
Solution Approach 1:
The tie layer is pre-formed with an expanded state that naturally conforms to the hypotube inner diameter without requiring excessive force during assembly. This preliminary expansion action eliminates the need for aggressive heating and forcing methods, thereby avoiding liner over-stretching while still achieving strong adhesion through the pre-compressed tie layer configuration.
Solution Approach 2:
The tie layer material is selected with specific physical parameters (durometer, elasticity) that allow it to maintain adequate compliance with the hypotube surface without requiring extreme dimensional precision. By optimizing the material parameters rather than relying solely on tight dimensional tolerances, the system achieves reliable adhesion while accommodating normal manufacturing variations.
2Ease of operation
If fluoropolymers are used to maintain lubricity, then insertion is easier, but material options are limited
Solution Approach 1:
The expandable tie layer acts as an intermediary between the liner and hypotube, providing the necessary lubricity and compliance without requiring the liner itself to be made of fluoropolymer. This intermediary layer enables the use of alternative liner materials (such as polyurethanes or polyether block amides) while still achieving easy insertion through the lubricious tie layer interface.
Solution Approach 2:
The tie layer material parameters (surface energy, friction coefficient) are optimized to provide adequate lubricity for insertion, allowing the liner material to be selected based on other criteria such as flexibility, strength, or chemical resistance. This parameter optimization of the tie layer decouples the insertion performance requirement from the liner material selection, expanding available material options.
3Ease of operation
If tight clearance is maintained between liner and hypotube, then lubricity is improved, but adhesion becomes difficult to achieve
Solution Approach 1:
The tie layer is pre-expanded to a state that creates optimal contact pressure with the hypotube surface, establishing strong adhesion bonds before the liner is fully inserted. This preliminary bonding action allows the system to maintain adequate clearance for lubricity while still achieving strong adhesion through the pre-compressed tie layer configuration.
Solution Approach 2:
The system uses a composite structure combining the liner material with the expandable tie layer material, where each material performs its specialized function. The liner provides structural integrity and lubricity, while the tie layer provides enhanced adhesion. This composite approach allows tight clearance to be maintained for lubricity while the tie layer compensates with strong chemical bonding to achieve adequate adhesion.
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 expandable tie layer enhances adhesion to hypotubes and other components, enabling the use of a broader range of materials, including polyurethanes and polyether block amides, while maintaining lubricity and reducing the risk of delamination.
Implementation Method 1
an expandable tie layer coating on at least a portion of an outer surface that can expand about 5% or more in outer diameter when subjected to heat
Implementation Method 2
providing a chemical bond to adjacent components
Data Source
AI summary
A common issue when building a catheter with a laser-cut hypotube is bonding the OD (outer diameter) of the PTFE or PE liner to the ID (inner diameter) of an adjacent component, e.g., a laser-cut hypotube An expandable tie layer or “heat grow tie layer” as described herein can be used as a coating for the liner that will expand or foam up to the ID (inner diameter) of an adjacent component, e.g., hypotube and improve adhesion to the hypotube without impacting the flexibility or lubricity of the liner. This and other applications of the expandable layer are described herein.