Bistable Polymer Stent Strut Snap-Through Buckling

Resolve Bottlenecks,
Find Innovative SolutionsGenerate Solutions

Solution Overview

Problem

Polymer stents for luminal organs face challenges in maintaining expanded diameter due to low Young's modulus and lack of plasticity, leading to potential diameter reduction and loss of self-expanding ability over time.

Innovation Solution

The indwelling medical device features a cylindrical network structure with struts connected via hinges, allowing for snap-through buckling deformation to maintain an expanded diameter by transitioning between stable states, preventing reverse deformation through elastic forces.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Object-affected harmful factors

If a polymer material is used to reduce stress on the lumen wall and improve biocompatibility, then the material strength and elasticity deteriorate, causing the device to cannot maintain expanded diameter over time

Engineering Contradiction:

Improvestress on lumen wallVSAvoidmaterial strength

Core Design Contradiction:

Object-affected harmful factorsVSStrength

Solution Approach 1:

The strut is divided into multiple strut pieces (first, second, third, fourth strut pieces) connected by hinges, allowing each segment to deform independently through snap-through buckling while collectively maintaining structural strength

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The device transitions from a static structure to a dynamic one with bistable states, where the strut can switch between compressed and expanded configurations through snap-through buckling, enabling the polymer material to maintain expanded diameter over time

Inventive Principle:

Principle #15Dynamics

2Adaptability or versatility

If a polymer material is used to improve flexibility and reduce mechanical stimulus, then the ability to resist diameter reduction deteriorates, leading to potential relapse of stenosis

Engineering Contradiction:

ImproveflexibilityVSAvoidability to resist diameter reduction

Core Design Contradiction:

Adaptability or versatilityVSReliability

Solution Approach 1:

The device employs dynamic bistable structures that can actively switch between states to resist diameter reduction forces, rather than relying solely on static material properties, thereby maintaining reliability while preserving flexibility

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The structural parameters of the strut (length, thickness, hinge positions) are optimized to enable snap-through buckling at specific force thresholds, allowing the device to transition from a flexible state during insertion to a rigid state for maintaining patency

Inventive Principle:

Principle #35Parameter changes

3Strength

If a metal material is used to provide strength and maintain expanded diameter, then the device becomes rigid and causes mechanical stimulus to the lumen wall

Engineering Contradiction:

Improvestrength to maintain diameterVSAvoidmechanical stimulus to lumen wall

Core Design Contradiction:

StrengthVSObject-affected harmful factors

Solution Approach 1:

The device changes its effective stiffness parameters dynamically through snap-through buckling, remaining flexible during insertion and deployment, then transitioning to a high-stiffness bistable state for maintaining diameter without continuous mechanical stimulus

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The device combines polymer material with a bistable structural design, creating a composite system that exhibits both the biocompatibility of polymers and the structural stability traditionally associated with metals

Inventive Principle:

Principle #40Composite materials

4Device complexity

If the strut is made from a single piece to simplify structure, then the ability to achieve snap-through buckling deformation deteriorates

Engineering Contradiction:

Improvestrut structure complexityVSAvoidsnap-through buckling capability

Core Design Contradiction:

Device complexityVSReliability

Solution Approach 1:

The strut is segmented into multiple pieces connected by hinges, creating the necessary degrees of freedom for snap-through buckling while maintaining a relatively simple overall structure that can be manufactured from a single polymer piece

Inventive Principle:

Principle #1Segmentation

Data Source

PatentUS10966849B2Indwelling medical device having bistable structure in lumen organ

Publication Date: 2021.04.06 YAMAGUCHI UNIV

AI summary

A cylindrical indwelling medical device is formed by connecting a plurality of struts in a circumferential direction of the device in such a way to share a rib in an axial direction in neighboring struts to form annular or spiral columns of struts and connecting the columns of struts in the axial direction via links. Each strut has at least one set of strut pieces providing a bistable structure for supporting a load from reducing a diameter of the indwelling medical device and portions for inducing snap-through buckling deformation. load is in a direction preventing reverse snap-through buckling deformation to hold an expanded diameter state of the device. After the indwelling medical device with its diameter reduced has been introduced into a luminal organ and has expanded its diameter to indwell there, the device can resist sufficiently against the reduction in diameter, thus maintaining the expanded diameter state of the device.