Polymer Scaffold Crimping Damage Reduction

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Solution Overview

Problem

Polymer scaffolds used in drug-eluting medical devices are prone to damage and irregular deformations during the crimping process, leading to structural weaknesses and high rejection rates due to their brittle nature and susceptibility to misalignment and non-uniform forces, which are not adequately addressed by existing crimping methods designed for metal stents.

Innovation Solution

A modified crimping process and apparatus that includes using a crimping assembly with movable blades having softened edges, interior balloon support to stabilize the scaffold, and precise alignment systems to reduce damage and improve batch yield, involving initial diameter reduction followed by final crimp steps, and adjusting balloon pressure to compensate for irregular deformations.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of manufacture

If conventional crimping methods designed for metal stents are used on polymer scaffolds, then the crimping process can be performed with standard equipment, but the polymer scaffold suffers damage including cracks, indentations, and irregular deformations

Engineering Contradiction:

Improvecrimping process compatibilityVSAvoidscaffold structural integrity

Core Design Contradiction:

Ease of manufactureVSReliability

Solution Approach 1:

The patent modifies the crimping process parameters including reducing crimping force, controlling crimping speed, and adjusting temperature to match the mechanical properties of polymer scaffolds. These parameter changes prevent damage while maintaining the crimping process functionality.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent introduces a compliant intermediate layer or modified crimper blade surface that acts as a mediator between the rigid crimping equipment and the soft polymer scaffold. This intermediary distributes the crimping force uniformly, preventing localized stress concentrations that cause cracks and deformations.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Device complexity

If standard crimping blades are used on polymer scaffolds, then the crimping assembly can be kept simple, but the polymer scaffold experiences non-uniform forces and misalignment

Engineering Contradiction:

Improvecrimping assembly simplicityVSAvoidscaffold alignment and force distribution

Core Design Contradiction:

Device complexityVSManufacturing precision

Solution Approach 1:

The patent employs dynamically adjustable crimping blades that can adapt their position and force application points during the crimping process. This dynamic adjustment ensures uniform force distribution and proper alignment without requiring complex pre-programming or rigid mechanical structures.

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The patent incorporates feedback mechanisms such as force sensors and position detectors that monitor the crimping process in real-time. This feedback allows the system to automatically adjust blade position and force to maintain proper alignment and prevent scaffold damage.

Inventive Principle:

Principle #23Feedback

3Productivity

If high crimping force is applied to reduce scaffold diameter, then the crimping efficiency is improved, but the polymer scaffold develops cracks and structural weaknesses

Engineering Contradiction:

Improvecrimping speed and efficiencyVSAvoidscaffold mechanical strength

Core Design Contradiction:

ProductivityVSStrength

Solution Approach 1:

The patent employs periodic or staged crimping where the scaffold is crimped in multiple incremental steps rather than a single high-force application. This staged approach allows the polymer structure to gradually adapt to the deformation, maintaining strength while achieving the required diameter reduction efficiently.

Inventive Principle:

Principle #19Periodic action

Solution Approach 2:

The patent applies a compliant cushioning layer or uses temperature pre-treatment before crimping to soften the polymer scaffold. This beforehand cushioning reduces the peak force required during crimping, preventing cracks while maintaining crimping efficiency.

Inventive Principle:

Principle #11Beforehand cushioning (Prior cushioning)

4Object-generated harmful factors

If replaceable sheets are used to prevent coating buildup on blades, then blade contamination is avoided, but additional material handling and sheet replacement complexity is introduced

Engineering Contradiction:

Improvecoating material buildup on bladesVSAvoidsheet handling and replacement mechanism

Core Design Contradiction:

Object-generated harmful factorsVSDevice complexity

Solution Approach 1:

The patent uses inexpensive, disposable protective sheets or coatings on the crimping blades that can be easily replaced. These single-use components prevent coating buildup without requiring complex cleaning or maintenance systems, balancing protection needs with system simplicity.

Inventive Principle:

Principle #27Cheap short-living objects (Disposable)

Data Source

PatentEP3184085B1Reducing crimping damage to polymer scaffold

Publication Date: 2020.01.01 ABBOTT CARDIOVASCULAR SYSTEMS INC

Figure 1A
Figure 1B
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AI summary

A medical device includes a polymer scaffold crimped to a catheter having an expansion balloon. The scaffold is crimped to the catheter by a multi-step process for increasing scaffold-catheter yield following a crimping sequence. Damage reduction during a crimping sequence includes modifying blades of a crimper, adopting a multi-step crimping sequence, and inflating a supporting balloon to support the scaffold during crimping.