Silicone Hydrogel Contact Lens Aqueous Extraction
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Solution Overview
Problem
Existing methods for producing silicone hydrogel contact lenses face challenges in achieving high oxygen permeability while maintaining optical transparency and biocompatibility, often requiring the use of hydrophobic silicone or fluorinated monomers that lead to phase separation, poor compatibility with hydrophilic monomers, and complex solvent-based extraction processes.
Innovation Solution
A method involving a solvent-free polymerizable formulation comprising fluorine-containing and non-fluorine-containing silicone monomers, along with hydrophilic monomers, that uses exclusively aqueous extraction and hydration processes to produce contact lenses with enhanced oxygen permeability and biocompatibility, avoiding the need for organic solvents and their associated complexities.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If hydrophobic silicone or fluorinated monomers are added to improve oxygen permeability, then oxygen permeability is improved, but phase separation and poor compatibility with hydrophilic monomers occur
Solution Approach 1:
The patent introduces hydrophilic monomers as intermediary components that act as compatibilizers between hydrophobic silicone/fluorinated monomers and the aqueous environment. These hydrophilic monomers form a bridge, allowing hydrophobic monomers to be incorporated without causing phase separation, thus maintaining both high oxygen permeability and optical transparency.
Solution Approach 2:
The patent creates a composite material system combining hydrophilic monomers, hydrophobic silicone monomers, and fluorinated monomers in specific ratios. This composite approach allows the material to simultaneously achieve high oxygen permeability from the hydrophobic components while maintaining optical transparency and compositional stability through the hydrophilic matrix.
2Reliability
If substantial amounts of hydrophobic materials are added to increase oxygen permeability, then oxygen permeability is improved, but optical transparency and biocompatibility deteriorate
Solution Approach 1:
The patent carefully controls the concentration parameters of hydrophobic monomers within specific ranges (e.g., 5-30 wt% silicone monomer, 5-30 wt% fluorinated monomer) and adjusts the hydrophilic monomer content accordingly. By optimizing these parameters, the material achieves high oxygen permeability while maintaining optical transparency and avoiding micro-phase separation that would compromise biocompatibility.
3Stability of the object's composition
If non-reactive solvents or diluents are used to reduce micro-phase separation, then compatibility is improved, but manufacturing complexity and cost increase
Solution Approach 1:
The patent eliminates the need for non-reactive solvents and diluents by using a solvent-free formulation approach. The hydrophilic monomers themselves serve as the dispersing medium, allowing direct polymerization without requiring additional extraction steps to remove solvents, thus simplifying the manufacturing process while maintaining compatibility.
Solution Approach 2:
The hydrophilic monomers perform multiple functions simultaneously: they act as the matrix material, provide hydrophilicity for comfort, and serve as compatibilizers for the hydrophobic monomers. This self-service approach eliminates the need for separate non-reactive diluent components and their associated removal processes.
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 approach results in contact lenses with improved oxygen permeability and biocompatibility, achieved through careful selection of formulation components and processing conditions, reducing manufacturing costs and environmental impact while maintaining the required properties for successful contact lens materials.
Implementation Method 1
reacting in a mould a polymerisable formulation comprising: (i) at least one fluorine-containing silicone monomer... (ii) at least one non-fluorine-containing silicone monomer and (iii) at least one hydrophilic monomer to form a contact lens
Implementation Method 2
subjecting the contact lens to one or more solvent extraction steps to remove impurities, oligomers and unreacted monomers and hydrate the contact lens, wherein all of the solvent extraction steps are undertaken using an aqueous solvent
Data Source
AI summary
A method of making a contact lens comprising the steps of reacting in a mold a polymerizable formulation comprising at least one fluorine-containing silicone monomer at least one non-fluorine-containing silicone monomer and at least one hydrophilic monomer to form a contact lens, subjecting the contact lens to one or more solvent extraction steps to remove impurities, oligomers and unreacted monomers and hydrate the contact lens, wherein all of the solvent extraction steps are undertaken using an aqueous solvent.