Silicone Hydrogel Lens Coating During Autoclave Sterilization
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Solution Overview
Problem
Existing methods for modifying the hydrophilicity of silicone hydrogel contact lenses are either costly, time-consuming, or do not provide durable and effective coatings, such as plasma treatment, wetting agents, and layer-by-layer deposition techniques.
Innovation Solution
A method involving a water-soluble, thermally-crosslinkable hydrophilic polymeric material with azetidinium groups is used to form a crosslinked coating on silicone hydrogel contact lenses by reacting with amino and/or carboxyl groups on the lens surface at elevated temperatures during the autoclaving process, combining coating and sterilization steps.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If plasma treatment is used to modify surface hydrophilicity, then wettability is improved, but the process becomes costly and time-consuming
Solution Approach 1:
The invention changes the chemical parameters of the lens surface by incorporating functional monomers (amino or carboxyl groups) into the silicone hydrogel formulation. This allows the surface to undergo chemical modification through reaction with polymeric wetting agents, achieving durable hydrophilicity without requiring post-manufacturing plasma treatment processes.
Solution Approach 2:
The invention performs preliminary chemical modification by incorporating reactive functional groups into the lens material during the casting process. This preliminary action enables subsequent covalent bonding of hydrophilic polymers, eliminating the need for later plasma treatment steps and improving manufacturing efficiency.
2Reliability
If wetting agents are incorporated into lens formulation, then surface hydrophilicity is improved, but haziness occurs due to incompatibility with silicone components
Solution Approach 1:
The invention applies local quality by concentrating hydrophilic functional groups at the lens surface through the use of surface-active monomers. These monomers position hydrophilic segments at the surface while maintaining compatibility with the bulk silicone hydrogel material, thus achieving surface hydrophilicity without causing bulk haziness.
Solution Approach 2:
The invention creates a composite material system where functional monomers with both silicone-compatible and hydrophilic segments are incorporated into the lens formulation. This composite approach allows the material to exhibit both silicone hydrogel properties and surface hydrophilicity without phase separation or haziness.
3Ease of manufacture
If layer-by-layer polyionic material deposition is used, then cost-effectiveness is improved, but coating durability is reduced
Solution Approach 1:
The invention extracts the need for complex multi-step LbL deposition processes by incorporating reactive functional groups directly into the lens formulation during casting. This simplifies the manufacturing process to a single coating step while enabling durable covalent bonding of hydrophilic polymers, achieving both cost-effectiveness and durability.
4Duration of action of stationary object
If crosslinked LbL coatings are applied to improve durability, then coating durability is improved, but hydrophilicity and wettability are reduced
Solution Approach 1:
The invention changes the crosslinking parameters by using covalent bonding between amino/carboxyl groups in the lens material and hydroxyl groups of polymeric wetting agents. This crosslinking mechanism maintains the hydrophilic nature of the coating while providing durability, unlike crosslinked LbL coatings that reduce hydrophilicity.
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 results in contact lenses with high hydrophilicity, wettability, and durability, allowing direct use without additional rinsing, and maintaining oxygen permeability and comfort.
Implementation Method 1
covalently attach the hydrophilic polymeric material onto the surface of the contact lens through second covalent linkages each formed between one azetidinium group of the hydrophilic polymeric material and one of the amino and/or carboxyl groups on and/or near the surface of the contact lens
Implementation Method 2
heating the contact lens in an aqueous solution in the presence of the hydrophilic polymeric material to and at a temperature from about 40°C to about 140°C for a period of time sufficient to covalently attach
Data Source
AI summary
A cost-effective method for making a silicone hydrogel contact lens has a crosslinked hydrophilic coating applied thereon. The method involves heating a silicone hydrogel contact lens in an aqueous solution in the presence of a water-soluble, highly branched, thermally- crosslinkable hydrophilic polymeric material having positively-charged azetidinium groups, and at a temperature from 40 Centigrade to 140 Centigrade for a period of time sufficient to covalently attach the thermally-crosslinkable hydrophilic polymeric material onto the surface of the silicone hydrogel contact lens through covalent linkages each formed between one azetidinium group and one of the reactive functional groups on and/or near the surface of the silicone hydrogel contact lens, thereby forming a crosslinked hydrophilic coating on the silicone hydrogel contact lens. Such method can be advantageously implemented directly in a sealed lens package during autoclave.