Surfactant Extraction for Silicone Hydrogel Lens Shape Accuracy

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Solution Overview

Problem

Silicone hydrogel contact lenses experience surface distortion during extraction and hydration processes due to swelling and shrinking, which can result in temporary adherence and distortion when in contact with carrier surfaces.

Innovation Solution

A method involving a liquid composition of alcohol, water, and a surfactant is used to reduce surface tension, preventing or minimizing distortion by allowing lenses to swell and contract freely without adherence to carrier surfaces.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Manufacturing precision

If silicone hydrogel contact lenses are exposed to alcohol-based extraction solutions, then extractable components are removed from the lenses, but the lenses undergo excessive swelling and surface distortion

Engineering Contradiction:

Improvelens shape accuracyVSAvoidextraction efficiency

Core Design Contradiction:

Manufacturing precisionVSProductivity

Solution Approach 1:

The patent modifies the chemical composition parameters of the extraction solution by adding surfactants to alcohol-based solutions. This changes the surface tension and wetting properties of the extraction medium, allowing it to effectively remove extractable components while minimizing excessive swelling and surface distortion of the lenses during the extraction process

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent introduces surfactants as intermediary substances in the extraction solution. These surfactants act as mediators between the alcohol-based extraction medium and the silicone hydrogel lens material, enabling effective extraction while controlling the swelling behavior and preventing surface distortion through modified interfacial properties

Inventive Principle:

Principle #24Intermediary (Mediator)

2Ease of operation

If silicone hydrogel contact lenses are placed in carrier pockets during extraction, then individual handling is enabled, but surface distortion occurs due to adherence to carrier surfaces

Engineering Contradiction:

Improveindividual lens handlingVSAvoidlens surface integrity

Core Design Contradiction:

Ease of operationVSManufacturing precision

Solution Approach 1:

The patent uses surfactants in the extraction solution as intermediary substances that modify the interaction between the lens surface and carrier pocket surfaces. The surfactants reduce surface tension and prevent direct adherence between the lens and carrier, allowing individual handling while maintaining lens surface integrity

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The patent changes the surface tension parameter of the extraction solution by adding surfactants. This parameter modification prevents the lens surface from adhering to the carrier pocket surfaces during extraction, thereby preventing surface distortion while enabling individual lens handling

Inventive Principle:

Principle #35Parameter changes

3Manufacturing precision

If silicone hydrogel contact lenses undergo swelling during extraction, then extractable components are removed, but temporary adherence to carrier surfaces causes distortion

Engineering Contradiction:

Improvelens shape accuracyVSAvoidsurface distortion

Core Design Contradiction:

Manufacturing precisionVSObject-affected harmful factors

Solution Approach 1:

The patent introduces surfactants as intermediary substances in the extraction solution that mediate the swelling process. The surfactants control the interaction between the extraction medium and lens material, allowing necessary swelling for extraction while preventing harmful adherence to carrier surfaces that would cause distortion

Inventive Principle:

Principle #24Intermediary (Mediator)

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 use of a surfactant in the alcohol-water composition significantly reduces surface distortion in silicone hydrogel lenses, maintaining their designed shape and preventing deformation during extraction and hydration.

Implementation Method 1

contacting the delensed ophthalmic lens product with a liquid composition that comprises alcohol, water, and a surfactant

Methodology Applied

Scientific EffectSurfactant: Surfactant

Implementation Method 2

Methodology Applied

Scientific EffectSurface tension reduction: Surface Tension

Implementation Method 3

The silicone hydrogel lens products undergo swelling and shrinking as a result of exposure to solutions used in the extraction and hydration steps

Methodology Applied

Scientific EffectSwelling:

Implementation Method 4

When placed in contact with an alcohol, a pre-extracted silicone hydrogel lens product will expand to a greater degree compared to when soaking in a solution containing only part alcohol

Methodology Applied

Scientific EffectAbsorption: Absorption (physical)

Data Source

PatentUS7968018B2Use of surfactants in extraction procedures for silicone hydrogel ophthalmic lenses

Publication Date: 2011.06.28 COOPERVISION INT LTD

AI summary

Methods of producing silicone hydrogel ophthalmic lenses include contacting one or more delensed silicone hydrogel ophthalmic lens with a liquid composition that contains alcohol, water, and a surfactant. The methods can be steps of an extraction/hydration procedure used in the production of silicone hydrogel contact lenses. In some examples, contacting silicone hydrogel ophthalmic lens products with a liquid composition that contains alcohol, water, and a surfactant can significantly reduce or prevent surface distortion of the ophthalmic lens resulting from the extraction procedure. Some methods include subsequently contacting the silicone hydrogel ophthalmic lens with a liquid composition consisting essentially of water and a surfactant.