PPR/NPR Composite Stent Materials for Auxetic Tissue Integration

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Solution Overview

Problem

Existing medical devices lack the ability to effectively utilize materials with negative and positive Poisson's ratios to achieve auxetic behavior, which is beneficial for deformation and tissue integration, particularly in implantable devices like stents and spine discs.

Innovation Solution

Composite medical devices are constructed using both Negative Poisson's Ratio (NPR) materials and Positive Poisson's Ratio (PPR) materials, incorporating geometric patterns such as re-entrant honeycomb structures, to exhibit auxetic behavior in response to deformation, including thermal strain and shape memory properties.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If traditional single-material construction is used, then manufacturing simplicity is maintained, but the device cannot achieve auxetic behavior for enhanced tissue integration

Engineering Contradiction:

Improveauxetic behaviorVSAvoidcomposite material structure

Core Design Contradiction:

Adaptability or versatilityVSDevice complexity

Solution Approach 1:

The patent applies composite materials by combining NPR foam material with PPR structural components (inner tube, wires, or mesh) to create a stent that exhibits auxetic behavior. The NPR material layer provides the negative Poisson's ratio effect while the PPR structural framework maintains mechanical integrity, enabling the device to expand surface area and improve tissue integration without sacrificing structural strength

Inventive Principle:

Principle #40Composite materials

2Area of moving object

If NPR foam material is added around the inner tube, then surface area and tissue integration are improved, but device complexity increases

Engineering Contradiction:

Improvesurface areaVSAvoidmulti-layer construction

Core Design Contradiction:

Area of moving objectVSDevice complexity

Solution Approach 1:

The patent implements the nested doll principle by placing the NPR foam material layer around the inner tube, with the NPR layer containing pores that provide surface area for tissue integration. This nested configuration allows the device to increase effective surface area for biological interaction while maintaining a compact, integrated structure that does not significantly increase overall device complexity

Inventive Principle:

Principle #7Nested doll (Nesting)

3Adaptability or versatility

If geometric patterns like re-entrant honeycomb are used, then auxetic behavior is achieved, but manufacturing precision requirements increase

Engineering Contradiction:

Improveauxetic behaviorVSAvoidgeometric pattern accuracy

Core Design Contradiction:

Adaptability or versatilityVSManufacturing precision

Solution Approach 1:

The patent applies porous materials by incorporating NPR foam material with inherent pore structures around the inner tube. The foam material naturally provides the auxetic behavior through its cellular structure, which expands in volume when compressed without requiring complex geometric patterns like re-entrant honeycombs. This approach achieves auxetic functionality while reducing manufacturing precision requirements compared to structurally complex geometric patterns

Inventive Principle:

Principle #31Porous 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 composite materials facilitate enhanced tissue integration and growth by applying radial pressure, expanding surface area, and providing improved biocompatibility through auxetic behavior, enhancing the functionality of implantable devices like stents and spine discs.

Implementation Method 1

an outer tube including a negative Poisson's ratio (NPR) foam material and disposed around an entirety of the inner tube. The stent is configured to exhibit an auxetic behavior in response to a deformation of the stent.

Methodology Applied

Scientific EffectNegative Poisson's ratio: Auxetic Materials

Implementation Method 2

an inner tube including a positive Poisson's ratio (PPR) material and defining a lumen extending along a longitudinal axis of the stent

Methodology Applied

Scientific EffectPositive Poisson's ratio: Poisson's Effect

Implementation Method 3

the deformation is caused by a thermal strain as part of a shape memory property

Methodology Applied

Scientific EffectShape memory property: Shape Memory Alloy

Data Source

PatentUS12453803B2Composite positive and negative Poisson's ratio materials for medical devices

Publication Date: 2025.10.28 PARK JOON BU

AI summary

A stent for insertion into a vessel of a patient includes an inner tube comprising a positive Poisson's ratio (PPR) material and defining a lumen extending along a longitudinal axis of the stent; and an outer tube comprising a negative Poisson's ratio (NPR) foam material and disposed around an entirety of the inner tube, the outer tube extending along the longitudinal axis of the stent. The stent is configured to exhibit an auxetic behavior in response to a deformation of the stent. An outer surface of the second portion is configured to apply a pressure to an inner surface of the vessel when the stent is implanted into the vessel and the deformation is removed.