Bioprosthetic Heart Valve Metal Frame Coating Fatigue Life

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Solution Overview

Problem

Metal frames used in bioprosthetic heart valves, such as wireforms and stents, face premature failure due to surface imperfections like inclusions, draw lines, and scratches, which are difficult to uniformly polish, especially on intricate geometries, leading to reduced fatigue life.

Innovation Solution

Applying a bond layer and a coating layer, such as chromium nitride, using physical vapor deposition or chemical vapor deposition techniques at low temperatures, to enhance the fatigue life of metal frames, ensuring uniform coverage and maintaining the frame's structural integrity.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Manufacturing precision

If mechanical polishing is used to remove surface imperfections, then surface smoothness is improved, but uniformity of treatment and accessibility to all surfaces deteriorates due to intricate geometries

Engineering Contradiction:

Improvesurface smoothnessVSAvoiduniformity of treatment

Core Design Contradiction:

Manufacturing precisionVSEase of manufacture

Solution Approach 1:

The patent replaces mechanical polishing with electropolishing, substituting a mechanical removal process with an electrochemical process. This allows uniform treatment of complex geometries through electrical field distribution rather than mechanical contact, resolving the contradiction between achieving surface smoothness and maintaining ease of manufacture across intricate structures

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent modifies the treatment parameters by controlling electropolishing conditions (electrical current, electrolyte composition, temperature, time) to achieve uniform surface treatment across complex geometries. This parameter optimization enables consistent surface quality without the limitations of mechanical methods

Inventive Principle:

Principle #35Parameter changes

2Manufacturing precision

If mechanical or electropolishing is used to remove surface imperfections, then certain flaws are removed, but other imperfections below the surface are exposed

Engineering Contradiction:

Improvesurface qualityVSAvoidfatigue life

Core Design Contradiction:

Manufacturing precisionVSReliability

Solution Approach 1:

The patent applies electropolishing as a preliminary treatment before final coating or implantation. This preliminary action removes surface imperfections that would initiate fatigue cracks, and the subsequent low-stress coating process seals the surface without exposing subsurface flaws, thereby improving both surface quality and fatigue life

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent creates a composite structure with the metal frame and a surface coating layer. This composite approach combines the structural integrity of the metal frame with the protective surface properties of the coating, which seals surface imperfections and prevents stress concentration, thereby improving fatigue life while maintaining surface quality

Inventive Principle:

Principle #40Composite materials

3Reliability

If coating is applied to enhance fatigue life, then durability is improved, but the complexity of the manufacturing process increases

Engineering Contradiction:

Improvefatigue lifeVSAvoidmanufacturing process complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent optimizes coating parameters (thickness, composition, deposition conditions) to achieve the minimum necessary protection against fatigue. By carefully controlling these parameters, the coating provides sufficient durability enhancement while minimizing the added manufacturing complexity and processing time

Inventive Principle:

Principle #35Parameter changes

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 method significantly increases the fatigue life of metal frames by distributing stress and enhancing durability, as demonstrated by improved performance in fatigue tests compared to uncoated controls.

Implementation Method 1

applying a coating material to at least a portion of the bond layer disposed on the external surface of the metal frame using a technique selected from the group consisting of: physical vapor deposition (PVD) and chemical vapor deposition (CVD)

Methodology Applied

Scientific EffectPhysical vapor deposition: Physical Vapour Deposition

Implementation Method 2

Methodology Applied

Scientific EffectChemical vapor deposition: Chemical Vapour Deposition

Data Source

PatentUS9549816B2Method for manufacturing high durability heart valve

Publication Date: 2017.01.24 EDWARDS LIFESCIENCES CORP

AI summary

An improved heart bioprosthetic device having a metal frame wireform or stent having an outer external surface. The metal frame has a bond layer coating at least a portion of the external surface and a coating layer disposed on at least a portion of the bond layer. The bond layer comprises a metal selected from the group consisting of: chromium, titanium, zirconium, aluminum, platinum, palladium, and niobium. The coating layer is selected from the group consisting of: a metal nitride, a metal oxide, a metal carbide, and combinations thereof. The coating layer may have a thickness of about 10 μm or less and a grain size of about 10 nm to about 15 nm, and may be characterized as polycrystalline with randomly-oriented grains with both cubic and orthorhombic phases. In one embodiment, the bond layer comprises chromium and the coating layer comprises chromium nitride.