Silicone Contact Lens Hydrogel Coating for Oxygen Permeability

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Solution Overview

Problem

Current silicone contact lenses face challenges in maintaining high oxygen permeability and surface hydrophilicity due to their hydrophobic nature, which can lead to oxygen deprivation for the cornea and irritation, and existing coatings do not provide a durable, thermodynamically stable, and lubricious surface.

Innovation Solution

A method involving a plasma treatment followed by contacting with a reactive hydrophilic polymer and thermally-induced crosslinking of a thermally-crosslinkable hydrophilic polymeric material to form a durable, thermodynamically stable hydrophilic and lubricious hydrogel coating on a silicone contact lens.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Use of energy by moving object

If a silicone contact lens is made with high oxygen permeability, then oxygen supply to the cornea is improved, but the surface becomes hydrophobic causing irritation and poor wettability

Engineering Contradiction:

Improveoxygen permeabilityVSAvoidsurface hydrophobicity

Core Design Contradiction:

Use of energy by moving objectVSObject-affected harmful factors

Solution Approach 1:

The patent applies composite materials by combining a silicone base material (providing high oxygen permeability) with a hydrophilic polymer coating layer (providing surface wettability and comfort). This multi-layer composite structure resolves the contradiction by allowing each layer to fulfill its specific function: the silicone core ensures oxygen transmission while the hydrophilic coating ensures surface compatibility with the cornea.

Inventive Principle:

Principle #40Composite materials

Solution Approach 2:

The patent applies local quality by creating a surface coating with different properties than the bulk material. The inner silicone layer maintains high oxygen permeability while the outer hydrophilic polymer layer provides surface wettability and lubricity. This local differentiation allows the lens to have high oxygen permeability in the bulk while maintaining a hydrophilic surface.

Inventive Principle:

Principle #3Local quality

2Object-affected harmful factors

If a hydrophilic coating is applied to improve surface wettability, then comfort is improved, but the coating durability and thermodynamic stability are insufficient

Engineering Contradiction:

Improvesurface wettabilityVSAvoidcoating durability

Core Design Contradiction:

Object-affected harmful factorsVSReliability

Solution Approach 1:

The patent applies preliminary action by performing plasma treatment on the silicone surface before applying the hydrophilic polymer coating. This plasma treatment creates a reactive surface that enhances the bonding between the silicone substrate and the hydrophilic coating, ensuring durable attachment. By preparing the surface in advance, the coating remains stable and resistant to degradation during storage and use.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent replaces simple physical coating with chemically-bonded coating through plasma treatment. The plasma treatment creates covalent bonds between the silicone surface and the hydrophilic polymer, transforming the attachment mechanism from weak physical adsorption to strong chemical bonding. This substitution ensures the coating remains durable and thermodynamically stable.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

3Object-affected harmful factors

If plasma polymerization is used to improve wettability, then water contact angle is reduced, but the surface hydrophilicity and lubricity are not sufficient for long-term stability

Engineering Contradiction:

ImprovewettabilityVSAvoidhydrophilicity duration

Core Design Contradiction:

Object-affected harmful factorsVSDuration of action of stationary object

Solution Approach 1:

The patent applies parameter changes by selecting specific hydrophilic polymers with high water content (at least 10% by weight) and specific molecular weight ranges (1,000 to 5,000,000 Daltons). These parameter optimizations ensure the coating maintains adequate water content for sustained hydrophilicity and lubricity. The plasma treatment parameters (power, time, gas composition) are also optimized to create sufficient surface reactivity without degrading the polymer.

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 solution enhances oxygen permeability, maintains surface hydrophilicity and lubricity even after storage, reducing corneal oxygen deprivation and irritation, while ensuring the coating's durability and stability over time.

Implementation Method 1

treating the silicone contact lens with a plasma

Methodology Applied

Scientific EffectPlasma treatment: Plasma

Implementation Method 2

thermally-induced crosslinking of a thermally-crosslinkable hydrophilic polymeric material

Methodology Applied

Scientific EffectThermal crosslinking:

Data Source

PatentEP3344302B1Soft silicone medical devices with durable lubricious coatings thereon

Publication Date: 2022.04.13 ALCON INC

AI summary

The invention is related to a medical device comprising a core material made of a crosslinkined silicone material and a hydrogel coating which is thermodynamically stable. The invention is also related to a method for producing such a medical device, especially a soft contact lens.