Hybrid Stent Composite Design for Radial Strength and Delivery Profile

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Solution Overview

Problem

Current stents lack a combination of high radial stiffness and strength with low-profile delivery and elastic deployment, which are beneficial for both balloon-expandable and self-expanding stent attributes.

Innovation Solution

A hybrid stent that utilizes both plastic and superelastic deformation modes, featuring a resilient ring with a superelastic wire in a sinusoidal pattern and malleable cannula segments, allowing for crimping and balloon expansion while exhibiting superelastic recovery to crushing forces.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Strength

If a stent is designed as balloon-expandable, then radial stiffness and strength are improved, but delivery profile and elastic recovery capability deteriorate

Engineering Contradiction:

Improveradial stiffnessVSAvoiddelivery profile

Core Design Contradiction:

StrengthVSEase of operation

Solution Approach 1:

The stent employs a composite structure combining a superelastic wire core (providing elasticity and recovery) with an outer malleable layer (providing strength and stiffness). This composite design allows the stent to achieve high radial strength while maintaining excellent elastic recovery capability and low-profile delivery characteristics.

Inventive Principle:

Principle #40Composite materials

2Ease of operation

If a stent is designed as self-expanding, then delivery profile and elastic deployment are improved, but radial stiffness and controlled expansion deteriorate

Engineering Contradiction:

Improvedelivery profileVSAvoidradial stiffness

Core Design Contradiction:

Ease of operationVSStrength

Solution Approach 1:

The hybrid stent structure combines a superelastic wire core with an outer malleable layer, where the malleable outer layer provides the necessary radial stiffness and controlled expansion characteristics, while the superelastic core maintains delivery profile advantages.

Inventive Principle:

Principle #40Composite materials

3Reliability

If a stent is made from superelastic alloy, then elastic recovery capability is improved, but radial strength and structural stability deteriorate

Engineering Contradiction:

Improveelastic recoveryVSAvoidradial strength

Core Design Contradiction:

ReliabilityVSStrength

Solution Approach 1:

The stent uses a composite construction with a superelastic wire core (for elastic recovery) surrounded by a malleable outer layer (for radial strength). This composite approach allows the stent to exhibit both superior elastic recovery and adequate radial strength.

Inventive Principle:

Principle #40Composite materials

Solution Approach 2:

Different regions of the stent have different material properties optimized for specific functions: the core provides elastic recovery while the outer layer provides structural strength, creating local quality differentiation that resolves the contradiction.

Inventive Principle:

Principle #3Local quality

4Ease of operation

If a stent is crimped to low-profile configuration, then delivery capability is improved, but structural integrity and expansion control deteriorate

Engineering Contradiction:

Improvedelivery capabilityVSAvoidstructural integrity

Core Design Contradiction:

Ease of operationVSStability of the object's composition

Solution Approach 1:

The composite structure of superelastic core and malleable outer layer allows the stent to be crimped to low-profile configurations for delivery while maintaining structural integrity. The superelastic core provides structural support during crimping and delivery, preventing collapse.

Inventive Principle:

Principle #40Composite materials

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 maintains an expanded configuration with minimal recoil and effectively recovers from crushing forces, making it suitable for vessels like the superficial femoral artery, offering improved radial strength and resilience.

Implementation Method 1

A hybrid stent that exploits both plastic and superelastic modes of deformation for deployment and use in a body vessel

Methodology Applied

Scientific EffectSuperelasticity: Pseudoelasticity

Implementation Method 2

The hybrid stent is plastically deformed for crimping and balloon expansion

Methodology Applied

Scientific EffectPlastic deformation: Plasticity

Implementation Method 3

exhibits superelastic recovery in response to crushing forces experienced in vivo

Methodology Applied

Scientific EffectSuperelastic recovery: Pseudoelasticity

Data Source

PatentUS8679173B2Hybrid stent and method of making such a stent

Publication Date: 2014.03.25 COOK MEDICAL TECHNOLOGIES LLC

AI summary

A hybrid stent (100) includes at least one resilient ring (105) comprising a superelastic wire (102) formed in a sinusoidal pattern of alternating crests (110) and troughs (115) about a circumference of the ring (105). A plurality of malleable cannula segments (120) overlie the superelastic wire at the crests and troughs. Each of the cannula segments (120) includes a bend (125) and has an inner diameter sized to allow relative motion between the wire (102) and the cannula segment (120). The hybrid stent (100) may also include a plurality of gaps (130), where each gap (130) is defined by a spacing between opposing cannula segments (120). Deformation of the malleable cannula segments (120) dominates a response of the stent to substantially uniform radial forces, and deformation of the resilient ring (105) dominates a response of the stent to radially nonuniform crushing forces.