Mandrel Support for Stent Coating Uniformity

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Solution Overview

Problem

Existing methods for coating stents often result in defects such as non-uniform surfaces, bare spots, and flaking, which can lead to thrombus formation and variations in drug release, complicating the effectiveness of therapeutic agents.

Innovation Solution

A mandrel support system that intermittently contacts the stent, allowing for six degrees of freedom movement, ensuring all surfaces are exposed to the coating composition and preventing adherence to the mandrel, thereby achieving a uniform and consistent coating.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Manufacturing precision

If the stent is mounted on a fixed mandrel for coating, then the stent is stable and easy to handle, but coating defects occur such as non-uniform surfaces, bare spots, and flaking

Engineering Contradiction:

Improvecoating uniformityVSAvoidmandrel-stent contact structure

Core Design Contradiction:

Manufacturing precisionVSDevice complexity

Solution Approach 1:

The mandrel is designed to allow six degrees of freedom movement of the stent relative to it, transforming the static contact relationship into a dynamic one. This enables all stent surfaces to be intermittently exposed to the coating composition during rotation, eliminating bare spots and non-uniform coating while maintaining simple mandrel structure

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The mandrel structure preliminarily prevents adherence between the stent and mandrel by providing clearance and freedom of movement before the coating process begins. This preliminary anti-action prevents coating defects such as flaking that would occur if the stent were fixed to the mandrel

Inventive Principle:

Principle #9Preliminary anti-action

2Manufacturing precision

If the stent is freely rotated during coating, then all surfaces are exposed to coating composition, but the stent may adhere to the mandrel causing coating defects

Engineering Contradiction:

Improvecoating coverageVSAvoidcoating defect prevention

Core Design Contradiction:

Manufacturing precisionVSReliability

Solution Approach 1:

The mandrel design incorporates a collar structure that loosely fits the stent bore, allowing the stent to move freely while maintaining positional relationship. This flexible connection ensures complete coating coverage without adherence, preventing coating defects while maintaining reliability

Inventive Principle:

Principle #30Flexible shells and thin films

3Manufacturing precision

If the mandrel contacts the stent at fixed points, then the stent is stable during rotation, but shadowing occurs preventing uniform coating on contact areas

Engineering Contradiction:

Improvecoating uniformityVSAvoidstent stability

Core Design Contradiction:

Manufacturing precisionVSEase of operation

Solution Approach 1:

The mandrel allows dynamic movement of the stent during rotation, so that contact points between stent and mandrel are constantly changing. This dynamic relationship eliminates shadowing effects while maintaining stent stability during the coating process, achieving uniform coating coverage

Inventive Principle:

Principle #15Dynamics

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

This approach significantly reduces coating defects, ensuring a uniform drug distribution and preventing adverse reactions, such as thrombus formation, by ensuring all stent surfaces are evenly coated and preventing adherence issues between the stent and the mandrel.

Implementation Method 1

a drive pin of the rotating mandrel striking the first end of the stent to thereby impart rotating motion to the stent

Methodology Applied

Scientific EffectImpact force: Impact Force

Implementation Method 2

spraying the coating composition on the stent

Methodology Applied

Scientific EffectSpray deposition: Spray

Implementation Method 3

The solvent is allowed to evaporate, leaving on the stent strut surfaces a coating of the polymer and the therapeutic substance impregnated in the polymer

Methodology Applied

Scientific EffectEvaporation: Evaporation

Data Source

PatentUS8313791B2Mandrels supporting medical devices during processing of the medical devices

Publication Date: 2012.11.20 ABBOTT CARDIOVASCULAR SYSTEMS INC

AI summary

An apparatus and method for applying a coating composition to a stent. A mandrel for supporting the stent has one or more drive pins and other supporting structure that loosely supports the stent, in an unstable position. The support permits freedom of movement of the stent relative to the mandrel to cause the stent to frequently re-position itself over the mandrel during a spraying process. When a coating composition is applied, the stent randomly or periodically moves about relative to the mandrel due to intermittent contact between the stent and the rotating mandrel and fluidic forces applied through the sprayed coating composition.