Variable-Flexibility Catheter Coating for Pushability and Kink Resistance
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Solution Overview
Problem
Standard angiography catheters fail under high pressures due to their limited pushability, trackability, and torqueability, while microcatheters with thin walls and small diameters struggle to navigate complex vasculature and are prone to kinking, and nitinol hypotubes are expensive and lack sufficient flexibility.
Innovation Solution
A catheter design featuring a hypotube with a polymer coating of varied flexibility, including flexibility-enhancing cuts and a liner, which provides differential flexibility along its length to enhance pushability, trackability, and torqueability, and withstands high pressures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If standard angiography catheters are used, then they can be manufactured from thermoplastic materials by extrusion processes, but they fail under high pressures exceeding their pressure ratings
Solution Approach 1:
The catheter combines a metal hypotube (stainless steel or nitinol) with a polymer coating to create a composite structure. The metal hypotube provides high pressure resistance and structural strength, while the polymer coating provides flexibility and biocompatibility. This composite approach allows the catheter to withstand pressures up to 1,200 psi while maintaining manufacturability through a multi-step process involving hypotube formation, cutting, and polymer coating application.
2Ease of operation
If microcatheters with thin walls and small diameters are used, then they can navigate tiny vessels, but they are prone to kinking and have limited length
Solution Approach 1:
The catheter uses a thin-walled metal hypotube with flexibility-enhancing cuts that create a flexible shell structure. These cuts allow the hypotube to bend and flex without kinking, while the polymer coating further enhances flexibility and prevents kinking. This flexible shell design enables the catheter to navigate tiny vessels (OD less than 6 French) while maintaining structural stability and resisting kinking even at lengths up to 150 cm.
3Stability of the object's composition
If nitinol hypotubes are used, then they are kink resistant, but they are much more expensive to manufacture and lack sufficient flexibility
Solution Approach 1:
The patent applies parameter changes by creating flexibility-enhancing cuts in the hypotube wall at specific locations and orientations. These cuts modify the structural parameters of the hypotube, allowing it to flex more easily while maintaining kink resistance. The polymer coating is then applied to further enhance flexibility and reduce manufacturing costs compared to using nitinol throughout. This approach achieves the desired flexibility and kink resistance at a lower manufacturing cost than pure nitinol solutions.
4Ease of manufacture
If the polymer coating has uniform flexibility, then manufacturing is simplified, but the catheter cannot provide differential pushability, trackability, and torqueability
Solution Approach 1:
The polymer coating is applied with varying properties along the length of the catheter to create local quality differences. The proximal portion has different flexibility characteristics than the distal portion, allowing each section to provide appropriate pushability, trackability, and torqueability. This local quality variation enables the catheter to navigate complex vasculature with different maneuverability requirements at different locations, while the coating process remains manufacturable through sequential application methods.
Data Source
AI summary
A catheter that is at least partially defined from a hypotube includes a polymer coating of varied flexibility on an outer surface of the hypotube. The polymer coating may include a plurality of adjacent sections that are continuous with each other, but have different flexibilities from each other. The sections may have different hardnesses, or durometers that impart them with their different flexibilities. Methods for manufacturing such catheters are also disclosed.