Monolithic Multilayer Catheter Shaft Balancing Strength and Flexibility
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Solution Overview
Problem
Conventional balloon catheters face challenges in balancing strength and flexibility, often resulting in kinking and bond failures, particularly in rapid exchange catheters, which complicates their use in tortuous anatomy and stent delivery systems.
Innovation Solution
A balloon catheter with a monolithic multilayer distal outer member, featuring a high-tensile strength inner layer and a flexible outer layer, necked to specific diameters for improved strength and flexibility, and integrated with a hypotube and guidewire lumen for enhanced pushability and trackability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If a relatively stiff proximal shaft section is used to facilitate advancement, then pushability is improved, but the catheter becomes more prone to kinking and bond failures
Solution Approach 1:
The catheter shaft is divided into multiple sections with different flexibility characteristics: a proximal shaft section with higher stiffness for pushability, a midshaft transition section with intermediate flexibility, and a distal shaft section with higher flexibility for trackability. This segmentation allows each section to perform its specific function without compromising overall reliability
Solution Approach 2:
Different sections of the catheter shaft are constructed with different material properties and structural characteristics. The proximal section uses a first outer member with specific stiffness, the midshaft uses a second outer member with transition properties, and the distal section uses a third outer member with higher flexibility. This local differentiation resolves the contradiction by providing appropriate properties in each location
2Ease of operation
If multiple shaft sections with different flexibility are bonded together, then pushability and trackability are improved, but kinking and bond failures occur
Solution Approach 1:
The transition between shaft sections is achieved by gradually changing the flexibility parameter along the catheter length. The midshaft transition section provides a gradual transition from the stiffer proximal section to the more flexible distal section, preventing abrupt changes that cause kinking and bond failures
Solution Approach 2:
The catheter shaft employs composite construction with multiple outer members made from different materials or material combinations. The first outer member, second outer member, and third outer member are constructed with varying material properties to achieve the desired flexibility gradient while maintaining bond integrity
3Ease of manufacture
If a single-layer distal outer member is used, then manufacturing is simpler, but strength and flexibility balance is insufficient
Solution Approach 1:
The distal outer member is constructed as a multilayer composite structure with an inner layer providing tensile strength and an outer layer providing flexibility. This composite construction achieves the required strength-flexibility balance while maintaining manufacturing feasibility through co-extrusion or layering processes
Solution Approach 2:
The distal outer member uses different materials for different functional requirements: the inner layer is made from a material with high tensile strength to prevent rupture, while the outer layer is made from a material with appropriate flexibility for navigation. This local differentiation of material properties resolves the strength-manufacturing contradiction
Data Source
Figure 1
Figure 2~4
AI summary
Balloon catheter includes an outer shaft (13) including a hypotube (30) and a monolithic multilayer distal outer member (40) and having an inflation lumen (11) defined therethrough, a balloon (20) in fluid communication with the inflation lumen, and an inner tubular member (50) having a guidewire lumen (51) defined therethrough. The monolithic multilayer distal outer member has a proximal end portion (44) and a distal end portion (43). The monolithic multilayer distal outer member has an inner layer (41) comprising a first polymer having a tensile strength greater than about 8,000 psi and an outer layer (42) comprising a second polymer having a flexural modulus of less than about 130,000 psi at room temperature. A proximal end of the monolithic multilayer distal outer member is coupled to the hypotube. The monolithic multilayer distal outer member is necked to a reduced diameter along at least a portion of a length thereof. The balloon has a proximal balloon shaft (23) coupled to a distal end of the monolithic multilayer distal outer member. The inner tubular member extends distally from a proximal port in the proximal end portion of the monolithic multilayer distal outer member through at least a portion of the balloon.