Compression-Resistant Sheath Structure for Flexible Catheter Tracking
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Solution Overview
Problem
Existing medical devices, such as catheters and sheaths, face challenges in maintaining resistance to axial compression while preserving flexibility, leading to undesirable conditions like shortening, internal spring forces, whipping, and material fracture when navigating tortuous vasculature.
Innovation Solution
The design incorporates a helical member with a braided support and a strain relief layer, using materials with different moduli of elasticity to enhance compression resistance and flexibility, where the helical member maintains winding alignment and the strain relief layer absorbs bending stresses, preventing axial compression and maintaining flexibility.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If existing medical devices use conventional materials and structures, then manufacturing is simpler, but resistance to axial compression deteriorates
Solution Approach 1:
The sheath is divided into multiple functional layers: an outer jacket layer, a braided support member layer, and a helical member layer. Each layer serves a specific mechanical function, with the braided and helical members providing compression resistance while the outer jacket provides flexibility. This segmentation allows the device to achieve high compression resistance without requiring a single complex material structure.
Solution Approach 2:
The invention uses composite construction combining different materials with complementary properties: the outer jacket material provides flexibility and biocompatibility, while the braided support member and helical member provide structural reinforcement and compression resistance. This composite approach enables the sheath to simultaneously achieve softness for patient comfort and strength for pushability.
2Strength
If materials with high modulus of elasticity are used to improve compression resistance, then flexibility deteriorates
Solution Approach 1:
Different regions of the sheath have different mechanical properties optimized for their specific functions. The outer jacket is made from softer, more flexible material to allow navigation through tortuous vasculature, while the braided support member and helical member provide localized reinforcement for compression resistance. This local differentiation of material properties resolves the contradiction between overall flexibility and localized strength.
Solution Approach 2:
The invention changes the modulus of elasticity parameter across different layers of the sheath. The outer jacket has a lower modulus for flexibility, while the braided and helical members have higher modulus for compression resistance. This gradient in mechanical parameters allows the device to exhibit both flexible and strong characteristics simultaneously.
3Ease of operation
If the sheath is made more flexible to improve anatomical tracking, then resistance to axial compression deteriorates
Solution Approach 1:
The sheath structure is segmented into flexible outer layers and reinforced inner layers. The outer jacket and intermediate layers provide flexibility for anatomical tracking, while the braided support member and helical member provide axial compression resistance. This segmentation allows each layer to optimize its function without compromising the other.
Solution Approach 2:
The composite construction combines materials with different mechanical properties: softer outer materials for flexibility and tracking, and stiffer braided and helical members for compression resistance. This composite approach enables the sheath to simultaneously achieve the contradictory properties of flexibility and compression strength.
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 configuration improves resistance to axial compression and kink resistance while maintaining desired flexibility, ensuring effective anatomical tracking and navigation.
Implementation Method 1
a strain relief layer formed from a second material having a second modulus of elasticity less than the first modulus of elasticity. The strain relief layer may be disposed about the helical member and radially inward of the outer jacket
Data Source
AI summary
An elongate tubular shaft having a lumen extending from a proximal portion to a distal portion may include an outer jacket forming an outer surface of the elongate tubular shaft, the outer jacket being formed from a first material having a first modulus of elasticity, a helical member extending from the proximal portion to the distal portion, a braided support member disposed about the helical member, and a strain relief layer formed from a second material having a second modulus of elasticity less than the first modulus of elasticity, wherein the strain relief layer is disposed about the helical member and radially inward of the outer jacket.