Shape Memory Polymer Catheter Temperature Control

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Solution Overview

Problem

Intravascular catheters face challenges in navigating tortuous vascular systems while maintaining sufficient stability at the target site to support subsequent medical procedures.

Innovation Solution

A catheter with an elongate shaft made of shape memory polymer that transitions from a flexible, rubbery state to a stiff, glassy state based on temperature, allowing for navigation through tortuous vasculature and providing stability at the target site through controlled heating and cooling.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If the catheter is made sufficiently flexible to navigate tortuous vasculature, then the catheter can reach remote target sites, but the catheter lacks sufficient column strength and stability to remain in position during subsequent treatment

Engineering Contradiction:

ImproveflexibilityVSAvoidstability

Core Design Contradiction:

Adaptability or versatilityVSStability of the object's composition

Solution Approach 1:

The catheter employs a shape memory polymer that can dynamically change its mechanical properties between flexible and rigid states in response to temperature changes. This allows the catheter to adapt its flexibility and stability characteristics to match the operational requirements at different stages of the medical procedure.

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The catheter utilizes temperature as a control parameter to induce phase transition in the shape memory polymer material. By changing the temperature parameter, the catheter transitions between glassy (rigid) and rubbery (flexible) states, thereby controlling its mechanical properties to resolve the contradiction between flexibility for navigation and stability for treatment.

Inventive Principle:

Principle #35Parameter changes

2Stability of the object's composition

If the catheter is made rigid to provide stability at the target site, then the catheter can provide back-out support, but the catheter cannot navigate through narrow, tortuous vessels

Engineering Contradiction:

ImprovestabilityVSAvoidflexibility

Core Design Contradiction:

Stability of the object's compositionVSAdaptability or versatility

Solution Approach 1:

The shape memory polymer enables the catheter to dynamically switch between rigid and flexible states. During navigation through tortuous vessels, the polymer is heated to become flexible; upon reaching the target site, it is cooled to become rigid and provide stability and back-out support.

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The catheter exploits the glass transition phase transition of the shape memory polymer material. By controlling temperature to induce transition between glassy and rubbery phases, the catheter achieves both flexibility for navigation and rigidity for stability at different operational stages.

Inventive Principle:

Principle #36Phase transitions

3Ease of operation

If the catheter material is kept at body temperature to remain flexible, then the catheter can navigate vasculature, but the catheter cannot provide sufficient structural support for treatment device delivery

Engineering Contradiction:

ImproveflexibilityVSAvoidcolumn strength

Core Design Contradiction:

Ease of operationVSStrength

Solution Approach 1:

The catheter uses temperature as a controllable parameter to switch material properties. At body temperature, the shape memory polymer is formulated to be flexible for navigation; when cooled below its glass transition temperature, it becomes rigid to provide column strength and structural support for treatment device delivery.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The catheter material undergoes glass transition phase change to switch between flexible and rigid states. This phase transition allows the catheter to provide sufficient column strength when needed while maintaining flexibility during navigation through the vasculature.

Inventive Principle:

Principle #36Phase transitions

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

Enables flexible navigation through narrow, tortuous vessels while maintaining stability and back-out support during medical procedures, enhancing the catheter's ability to deliver therapeutic devices effectively.

Implementation Method 1

The shape memory polymer retains relatively stiff, glassy characteristics at temperatures below the glass transition temperature and becomes relatively flexible and rubbery at temperatures above the glass transition temperature

Methodology Applied

Scientific EffectGlass transition: Phase Change

Implementation Method 2

The guidewire may be connected to an electrical source, wherein thermal energy is created by electrical resistance along the guidewire

Methodology Applied

Scientific EffectJoule heating: Joule Heating

Data Source

PatentUS7828790B2Selectively flexible catheter and method of use

Publication Date: 2010.11.09 STRYKER EUROPEAN OPERATIONS HOLDINGS LLC

AI summary

Catheter assembly including an elongate shaft comprising a thermoplastic polymer such as a thermoplastic shape memory polymer having a pre-selected glass transition temperature (Tg) and a means for heating the thermoplastic polymer, wherein the thermoplastic polymer is in a rubbery state at temperatures above the glass transition temperature and is in a glassy state at temperatures below the glass transition temperature. The elongate shaft may be selectively heated and cooled to provide sufficient flexibility and retention during a medical procedure.