Thin-Walled ePTFE Vascular Graft Self-Sealing Design
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Solution Overview
Problem
Existing multi-layer vascular grafts are thicker due to the need for impermeable elastomer and porous layers, which affects handling characteristics, flexibility, and ease of suturing, and the production of thin-walled ePTFE tubes is technically challenging.
Innovation Solution
A self-sealing vascular graft is produced using ePTFE tape helically wound with overlapping turns and sintered to form a thin-walled tube, combined with a resealable polymer layer, allowing for a tri-layer structure with improved strength and suture retention.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If multi-layer vascular grafts use impermeable elastomer layers for self-sealing, then sealing function is improved, but wall thickness increases and handling characteristics deteriorate
Solution Approach 1:
The patent uses a thin elastomeric layer (0.05-0.5mm) as a flexible shell that provides self-sealing properties while minimizing wall thickness. This thin film approach maintains the sealing function through the elastomer's ability to deform and seal around penetrations, while the reduced thickness improves handling characteristics compared to traditional thicker multi-layer constructions.
Solution Approach 2:
The patent combines ePTFE (expanded polytetrafluoroethylene) with a thin elastomeric layer to create a composite graft structure. The ePTFE provides structural integrity and porosity for tissue ingrowth, while the thin elastomeric layer provides self-sealing properties. This composite approach allows the graft to achieve both sealing function and improved handling through optimized material combination rather than increased thickness.
2Ease of operation
If ePTFE tube wall thickness is reduced for better handling, then flexibility is improved, but manufacturing precision becomes more difficult to achieve
Solution Approach 1:
The patent changes the manufacturing parameters by using ePTFE in a relaxed, non-oriented state rather than highly oriented stretched ePTFE. This parameter change allows for thinner walls (0.05-0.5mm) while maintaining uniform thickness and manufacturing feasibility. The relaxed state of the ePTFE enables better control over wall thickness uniformity during fabrication, resolving the contradiction between thin wall flexibility and manufacturing precision.
3Ease of operation
If thin-walled ePTFE tubes are produced by conventional extrusion, then wall thickness is reduced, but production complexity and cost increase
Solution Approach 1:
The patent employs a disposable mandrel that is removed after the ePTFE tube is formed and sintered. This approach simplifies the production process by eliminating the need for complex, reusable forming tools or intricate post-processing steps. The mandrel serves its purpose during formation and is then discarded, reducing production complexity and cost while enabling thin-walled tubes to be manufactured efficiently.
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 method enables the production of thin-walled vascular grafts with enhanced strength, flexibility, and uniformity, improving handling characteristics and suture retention while maintaining self-sealing properties.
Implementation Method 1
sintered to form a thin-walled tube
Implementation Method 2
heating above the crystalline melt point of ePTFE
Data Source
AI summary
There is provided a thin-walled self-sealing vascular graft with a first tubular structure formed from ePTFE and having a wall thickness of 0.2 mm or less, and a resealable polymer layer, such as a styrene copolymer, located on one surface of said first tubular structure. A second tubular structure may also be present, so that the resealable polymer layer is disposed between said first and second tubular structure. The second tubular structure is preferably formed from a textile layer but can also be ePTFE. The graft can be used for replacing a defective portion of the vasculature in a patient in need thereof.