Silicone Hydrogel Contact Lens Formulation for Wettability and Oxygen Permeability
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing silicone hydrogel contact lenses face challenges with poor wettability, high modulus, clarity, hydrolytic instability, and high costs due to the use of expensive raw materials, and struggle to achieve desirable levels of oxygen permeability and water content.
Innovation Solution
The development of silicone hydrogels with a specific composition comprising slow-reacting hydrophilic monomers, silicone-containing components, and hydroxyl-containing components, which are formulated to achieve a balance of properties such as high water content and oxygen permeability, while using commercially available and inexpensive monomers, without the need for surface modification or special compatibilizing agents.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If polyfunctional silicone monomers or macromers are used as crosslinking agents to improve wettability, then the modulus of the final polymer increases, but the desired low modulus and good clarity are compromised
Solution Approach 1:
The patent changes the chemical parameters by using monomeric N-vinylpyrrolidone (NVP) instead of polyfunctional crosslinking agents, and carefully controls the concentration of NVP (25-55% by weight) to achieve wettability without excessive crosslinking that would increase modulus
Solution Approach 2:
The patent replaces expensive polyfunctional silicone monomers and macromers with commercially available monomeric NVP, which is less expensive and does not require special handling or custom manufacturing of compatibilizing components
2Reliability
If monomeric N-vinylpyrrolidone (NVP) is incorporated into the monomer mix to improve wettability, then surface modification is eliminated, but achieving desirable oxygen permeability becomes difficult due to low silicone content in available monomers
Solution Approach 1:
The patent creates a composite monomer system combining NVP with HEMA and TRIS, where each component contributes different properties: NVP provides wettability, HEMA provides hydrophilicity and water content, and TRIS provides silicone content for oxygen permeability. This composite approach allows achieving all desired properties simultaneously
Solution Approach 2:
The patent optimizes the weight percentage composition of each monomer in the mix to balance wettability, oxygen permeability, and mechanical properties, achieving desirable levels without requiring surface modification
3Illumination intensity
If anionic monomers such as methacrylic acid (MAA) are added to reduce haziness, then clarity improves, but hydrolytic instability is caused
Solution Approach 1:
The patent replaces anionic monomers like MAA with non-anionic alternatives (HEMA and TRIS) that do not cause hydrolytic instability, while still achieving clarity through proper formulation and controlled reaction conditions
4Reliability
If expensive raw materials and special compatibilizing components are used to achieve desirable properties, then wettability and stability improve, but manufacturing cost increases significantly
Solution Approach 1:
The patent uses commercially available monomers (NVP, HEMA, TRIS) that are less expensive than polyfunctional silicone monomers and macromers, eliminating the need for custom-manufactured compatibilizing components and special handling procedures
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 resulting silicone hydrogels exhibit a water content of at least 50% and oxygen permeability of at least 80 barrers, providing a suitable balance of properties for biomedical applications, particularly in contact lenses, ensuring healthy corneal function and ocular environment compatibility.
Implementation Method 1
oxygen permeability of at least 80 barrers
Implementation Method 2
slow-reacting hydrophilic monomer having a slow-reacting hydrophilic monomer kinetic half life
Data Source
AI summary
The present invention relates to a process comprising the steps of reacting a reactive mixture comprising at least one silicone-containing component, at least one hydrophilic component, and at least one diluent to form an ophthalmic device having an advancing contact angle of less than about 80°; and contacting the ophthalmic device with an aqueous extraction solution at an elevated extraction temperature, wherein said at least one diluent has a boiling point at least about 10° higher than said extraction temperature.