Thermal Nitriding of Titanium Implantable Device Components

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Solution Overview

Problem

Titanium components in implantable medical devices, particularly in batteries, face corrosion issues due to aggressive chemical environments like fluorine-containing electrolytes, leading to increased electrical impedance and reduced power output over time.

Innovation Solution

A thermal nitriding process is used to form a corrosion-resistant surface region with increased nitrogen concentration, comprising titanium nitride or dititanium nitride, which provides uniform and strong adhesion on complex geometries, reducing the risk of cracking and flaking.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If titanium components are used in aggressive chemical environments, then biocompatibility is maintained, but corrosion resistance deteriorates due to fluorine-containing electrolytes

Engineering Contradiction:

ImprovebiocompatibilityVSAvoidcorrosion resistance

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The patent applies composite material structure by creating a titanium nitride surface layer on titanium components. The base titanium material maintains biocompatibility while the titanium nitride surface layer provides enhanced corrosion resistance against fluorine-containing electrolytes, effectively combining the beneficial properties of both materials in a layered composite structure.

Inventive Principle:

Principle #40Composite materials

Solution Approach 2:

The patent changes the chemical composition parameter of the titanium surface by introducing nitrogen through thermal nitriding process. This parameter change transforms the surface chemistry to form titanium nitride compounds, which fundamentally alter the surface's interaction with corrosive electrolytes while preserving the bulk titanium's biocompatible properties.

Inventive Principle:

Principle #35Parameter changes

2Reliability

If thermal nitriding process is used to form corrosion-resistant surface region, then corrosion resistance is improved, but manufacturing complexity increases

Engineering Contradiction:

Improvecorrosion resistanceVSAvoidmanufacturing complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The thermal nitriding process is performed as a preliminary treatment before the titanium components are assembled into the battery. By pre-forming the corrosion-resistant titanium nitride surface layer on raw titanium components, the manufacturing complexity is managed through staged processing, allowing each component to be treated independently before final assembly.

Inventive Principle:

Principle #10Preliminary action

3Ease of manufacture

If coating thickness is minimized, then manufacturing cost is reduced, but corrosion protection effectiveness may deteriorate

Engineering Contradiction:

Improvemanufacturing costVSAvoidcorrosion protection effectiveness

Core Design Contradiction:

Ease of manufactureVSReliability

Solution Approach 1:

The patent optimizes the thermal nitriding process parameters (temperature, time, nitrogen partial pressure) to achieve the minimum necessary nitrogen diffusion depth that provides adequate corrosion protection. By precisely controlling these parameters, the surface layer thickness is minimized while maintaining sufficient corrosion resistance, thereby reducing material costs and manufacturing complexity.

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 thermal nitriding process effectively protects titanium components from corrosion, maintaining electrical impedance stability and extending the lifespan of implantable medical device batteries by forming a thin, uniformly coated surface region that adheres strongly to the underlying material.

Implementation Method 1

a corrosion-resistant surface region of increased nitrogen concentration is formed at an exposed surface of the titanium or titanium-based alloy component by heating the component in a nitrogen-bearing atmosphere

Methodology Applied

Scientific EffectDiffusion: Diffusion

Implementation Method 2

using a thermal nitriding process to grow a corrosion-resistant surface region of increased nitrogen concentration on a titanium component

Methodology Applied

Scientific EffectNitriding: Nitriding

Data Source

PatentUS8916004B2Thermal nitriding process for components of implantable medical devices

Publication Date: 2014.12.23 MEDTRONIC INC

AI summary

A component of an implantable medical device comprises a body comprising at least one external surface, the body comprising at least one of titanium, titanium-based alloys, and composites thereof, and a corrosion-resistant surface region at the at least one external surface, the corrosion-resistant surface region comprising at least one of titanium nitride, dititanium nitride, and a solid solution of nitrogen dissolved in the body, wherein the corrosion-resistant surface region is formed by thermal nitridation of the body.