Expandable Structure With Counterbalancing Shape Memory Forces
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Solution Overview
Problem
Existing expandable structures, such as stents, face challenges in maintaining stability and balance between expansion and contraction forces, leading to inefficient deployment and potential collapse or chronic outward forces on lumen walls.
Innovation Solution
A stent design incorporating a shape memory (SM) portion and a second portion mechanically coupled to resist expansion, where the SM portion's expanding force decreases with strain, and the second portion applies a reactive contracting force, achieving a balance between different expansion states and configurations, ensuring stability in both crimped and deployed states.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a shape memory portion is used to provide expanding force, then the stent achieves self-expansion capability, but the stent experiences recoil and instability after deployment
Solution Approach 1:
The patent applies the counterweight principle by introducing a second portion with contracting force that balances the expanding force of the shape memory portion. This second portion acts as a counterbalancing element that prevents recoil and stabilizes the stent after deployment, directly resolving the instability caused by unbalanced expansion forces.
Solution Approach 2:
The patent utilizes parameter changes by treating the shape memory portion to modify its force-strain characteristics. The treatment causes the expanding force to decrease as strain increases, creating a natural balancing effect that enhances stability while maintaining self-expansion capability throughout the deployment process.
2Force
If the SM portion expanding force is high, then the stent can overcome resistance during deployment, but the stent exerts chronic outward forces on lumen walls
Solution Approach 1:
The patent applies parameter changes by treating the shape memory portion to create a decreasing force-strain relationship. This treatment ensures that while high expanding force is available initially to overcome deployment resistance, the force automatically decreases as the stent expands, preventing chronic outward forces on the lumen walls after deployment.
Solution Approach 2:
The second portion with contracting force serves as a counterbalancing element that offsets the expanding force of the shape memory portion. This counterweight mechanism ensures that the net force on the lumen walls remains low after deployment, eliminating chronic outward forces while preserving the high initial expanding force needed for deployment.
3Stability of the object's composition
If the stent is designed to be stable in crimped state, then the stent resists premature expansion, but the stent requires higher deployment force
Solution Approach 1:
The second portion with contracting force acts as a counterbalancing element that stabilizes the crimped state by opposing premature expansion. During deployment, this same counterweight mechanism contributes to the force balance, allowing the stent to transition smoothly from crimped to deployed state without requiring excessive deployment force.
Solution Approach 2:
The treatment of the shape memory portion creates a decreasing force-strain relationship that facilitates controlled deployment. As the stent transitions from crimped to deployed state, the expanding force naturally decreases, working in conjunction with the contracting force of the second portion to enable stable deployment without requiring excessive force.
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 design allows for stable deployment and self-crimping, reducing recoil and enhancing crush resistance, while maintaining a low outward force on the lumen, thereby improving conformability and migration resistance.
Implementation Method 1
The SMA which is initially in an initial configuration in which it can be placed into position within the body, can be mechanically deformed into an operational configuration in which it remains deployed within the body.
Implementation Method 2
This conversion increases the temperature of transformation (As) from an initial transformation temperature As ° to a temperature As '. When the SMA, once in the second configuration, is heated to a temperature higher than As ', it transforms to an at least partial austenite and it transforms towards the undeformed first configuration with a decrease of As from As ' to As °.
Data Source
Figure 1A~1B
Figure 2~3
Figure 4~5
AI summary
An expandable structure comprising: a first shape memory (SM) portion which is in a strain-induced state; and a second portion which resists expansion of said structure due to said first portion, over a plurality of different expansion states of said first portion. Optionally, wherein said SM portion resists contraction of said structure due to forces applied by said second portion. Optionally or alternatively, said strain induced state is characterized by a SM portion expanding force decreasing as a function of strain of said SM portion, so as to have a difference of at least 10% in force between two strain states said structure is usable at.