Hybrid Stent Balloon-Expandable Self-Expanding Shape Memory Alloy
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Solution Overview
Problem
Current stents used to treat aneurysms face challenges in balancing radial stiffness and flexibility, as radial stiffness must be sacrificed to achieve flexibility and vice versa, which is critical for bridging gaps between main grafts and target vessels with varying tortuousity and motion due to respiration and physical movements.
Innovation Solution
A hybrid balloon-expandable/self-expanding stent fabricated from a shape memory alloy wire with a self-expanding distal portion and a balloon-expandable proximal portion, featuring a helical configuration for the distal portion and a ring-like configuration for the proximal portion, allowing for controlled austenite transformation temperatures to achieve both flexibility and stiffness without joints or welds.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If radial stiffness is increased to provide structural support and sealing force, then the ability to navigate tortuous vessels is reduced
Solution Approach 1:
The stent is divided into multiple segments or cells along its length, with each segment capable of independent deformation. This segmentation allows the stent to flex and conform to tortuous vessel geometries while maintaining radial stiffness through the coordinated expansion of individual segments, resolving the contradiction between flexibility and radial support capability
Solution Approach 2:
Different portions of the stent are designed with different structural characteristics - some segments have higher radial stiffness for sealing and support, while other segments have enhanced flexibility for navigation. This local differentiation allows the stent to simultaneously exhibit both required properties in different locations along its length
2Adaptability or versatility
If the stent is made more flexible to accommodate vessel motion and tortuousity, then radial stiffness and sealing capability are compromised
Solution Approach 1:
The stent incorporates dynamic elements that allow it to adapt its mechanical properties in response to applied forces. During delivery, the stent remains flexible for navigation, but upon deployment it transitions to a rigid state to provide sealing force, dynamically adjusting its stiffness based on the deployment phase and external conditions
3Strength
If additional reinforcement is added to increase radial stiffness, then device complexity and manufacturing difficulty increase
Solution Approach 1:
The stent utilizes composite material structures combining different materials with complementary properties within a unified architecture. This allows the achievement of high radial stiffness through material composition rather than added structural complexity, maintaining manufacturing feasibility while providing required mechanical performance
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 hybrid stent provides a balance of flexibility and radial stiffness, enabling secure anchoring and deployment in tortuous vessels while maintaining structural integrity, suitable for endovascular applications and reducing the need for additional reinforcement or welding.
Implementation Method 1
A hybrid balloon-expandable/self-expanding stent fabricated from a shape memory alloy wire
Implementation Method 2
controlled austenite transformation temperatures to achieve both flexibility and stiffness
Data Source
Figure 1A~1C
Figure 2
Figure 3A~3C
AI summary
A hybrid prosthesis (100) for deployment in a body vessel includes a tubular stent body (110) comprising a wire (105) comprising a shape memory alloy, where the tubular stent body (110) has a self-expanding portion (110a) comprising a distal portion (115) of the wire (105) and a balloon-expandable portion (110b) comprising a proximal portion (120) of the wire (105). The shape memory alloy comprises an Af of less than 37°C in the self-expanding portion (110a) and an As of greater than 37°C in the balloon-expandable portion (110b).