Calcium Phosphate Coating on Polymeric Implants

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Solution Overview

Problem

Polymeric medical implants face challenges with biointegration due to poor bonding strength of calcium phosphate coatings, particularly when applied using plasma spraying, which damages the polymeric substrates and results in low fracture resistance and delamination.

Innovation Solution

Applying a calcium phosphate coating using Ion Beam Assisted Deposition (IBAD) at ambient temperatures, with a thermal barrier coating to protect the substrate, and heat-treating the coating to achieve a functionally graded crystalline-amorphous structure for improved adhesion and osteointegration.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If plasma spraying is used to apply calcium phosphate coating, then coating application is fast and cost effective, but the coating damages the polymeric substrate and results in low fracture resistance and delamination

Engineering Contradiction:

Improvecoating application speedVSAvoidcoating adhesion and substrate integrity

Core Design Contradiction:

ProductivityVSReliability

Solution Approach 1:

The invention changes the fundamental parameter of coating temperature from high (plasma spraying) to low (molecular beam deposition at ambient or near-ambient temperatures). This parameter change allows the coating to be applied without damaging the polymeric substrate, thereby maintaining substrate integrity while still achieving effective coating application

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The invention replaces the mechanical/thermal plasma spraying process with a molecular beam deposition process. This substitution uses physical vapor deposition mechanisms rather than high-temperature plasma, eliminating the thermal damage to the polymer while maintaining coating effectiveness

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

2Reliability

If thick calcium phosphate coatings are applied, then bone in-growth is facilitated, but fracture resistance decreases and delamination occurs

Engineering Contradiction:

Improvebone in-growth facilitationVSAvoidfracture resistance

Core Design Contradiction:

ReliabilityVSStrength

Solution Approach 1:

The invention applies local quality by creating a thin but highly functional coating with controlled porosity and surface characteristics. The coating is thin enough to maintain fracture resistance but designed with specific local properties (porosity, surface area) that facilitate bone in-growth, achieving both goals through localized property optimization rather than uniform thickness

Inventive Principle:

Principle #3Local quality

3Reliability

If plasma sprayed HA coating is applied, then greater direct bone attachment is promoted, but bond strength at the coating-substrate interface varies and delamination occurs

Engineering Contradiction:

Improvebone attachmentVSAvoidcoating-substrate bond strength

Core Design Contradiction:

ReliabilityVSStrength

Solution Approach 1:

The invention introduces an intermediary layer or surface treatment between the polymeric substrate and the calcium phosphate coating. This intermediary enhances the chemical or physical bonding at the interface, ensuring strong adhesion while maintaining the coating's ability to promote bone attachment

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The invention creates a composite structure combining the polymeric substrate with the calcium phosphate coating, where the interface is engineered for optimal bonding. The composite design ensures strong interfacial adhesion while maintaining the individual benefits of both materials

Inventive Principle:

Principle #40Composite materials

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 provides strong, thin calcium phosphate coatings with enhanced interfacial strength and bioactivity, reducing the risk of implant rejection and improving the longevity of polymeric implants by ensuring better integration with surrounding tissue.

Implementation Method 1

The coating can be applied using Ion Beam Assisted Deposition

Methodology Applied

Scientific EffectIon Beam Assisted Deposition: Physical Vapour Deposition

Implementation Method 2

with a thermal barrier coating to protect the substrate

Methodology Applied

Scientific EffectThermal barrier: Thermal Insulation

Implementation Method 3

and heat-treating the coating to achieve a functionally graded crystalline-amorphous structure

Methodology Applied

Scientific EffectHeat treatment: Heat Treatment

Implementation Method 4

to achieve a functionally graded crystalline-amorphous structure

Methodology Applied

Scientific EffectCrystallization: Crystallisation

Data Source

PatentUS8323722B2Processing of biocompatible coating on polymeric implants

Publication Date: 2012.12.04 NORTH CAROLINA STATE UNIV

AI summary

The present invention provides polymeric substrates comprising a biocompatible coating and methods of preparation thereof. In particular, the coating may be a ceramic material, especially a calcium phosphate material, which may be functionally graded. The invention provides the ability to apply high quality coatings to polymeric substrates without damaging the substrate (e.g., melting the polymeric material). The functionally graded coating can provide crystalline calcium phosphate near the coating interface with the substrate and provide amorphous calcium phosphate at the outer surface of the coating.