Silicone Hydrogel Contact Lens Coating for Durability
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Solution Overview
Problem
Current methods for modifying silicone hydrogel contact lenses to enhance hydrophilicity and durability are either cost-inefficient, susceptible to lipid and protein deposition, or compromise the mechanical properties of the lens material, particularly due to issues with plasma treatment and layer-by-layer deposition techniques.
Innovation Solution
A method involving a plasma base coating on silicone hydrogel contact lenses, followed by a layer of poly(alkylacrylic acid) and subsequent thermally-crosslinkable hydrophilic polymeric material to form a composite coating that is durable and lubricious, minimizing exposure to ocular environments and antimicrobial deposition.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If plasma treatment is used to modify the hydrophilicity of silicone hydrogel contact lenses, then the surface wettability and durability are improved, but the manufacturing cost increases due to equipment investment and drying requirements
Solution Approach 1:
The coating is divided into multiple functional layers: a plasma base coating layer (0.5-40 nm) that provides strong adhesion and hydrophilicity, and a thicker hydrogel top coating layer that provides lubricity and durability. This segmentation allows each layer to optimize its specific function while reducing overall manufacturing complexity
Solution Approach 2:
The invention uses a composite coating structure combining plasma-treated base coating material with hydrogel top coating material. The plasma base coating provides chemical attachment to the silicone hydrogel surface, while the hydrogel top coating provides the desired lubricious properties, creating a composite structure that achieves both wettability and comfort
2Reliability
If plasma treatment is used to modify the hydrophilicity of silicone hydrogel contact lenses, then the surface wettability is improved, but the manufacturing process complexity increases due to drying requirements
Solution Approach 1:
The plasma base coating is applied first to the silicone hydrogel contact lens surface before the hydrogel top coating is applied. This preliminary action creates a chemically-active surface that enhances adhesion of the subsequent hydrogel layer, eliminating the need for drying steps between coating applications
Solution Approach 2:
The plasma base coating acts as an intermediary layer between the silicone hydrogel substrate and the hydrogel top coating. It provides chemical attachment points for the hydrogel layer while maintaining hydrophilicity, serving as a bridge that simplifies the overall manufacturing process
3Ease of manufacture
If layer-by-layer polyionic material deposition is used to modify hydrophilicity, then the manufacturing cost is reduced, but the coating durability decreases due to hole formation and patchiness
Solution Approach 1:
The invention changes the deposition parameters by using a plasma-based initial layer that allows for longer deposition times and better coverage. The plasma base coating creates a uniform foundation that prevents hole formation and patchiness, enabling the subsequent hydrogel top coating to form a continuous, durable layer
4Ease of manufacture
If layer-by-layer coating is used to modify hydrophilicity, then the manufacturing cost is reduced, but the coating thickness is insufficient to prevent exposure of silicone hydrogel material
Solution Approach 1:
The coating structure is organized in nested layers: the plasma base coating (0.5-40 nm) is nested directly on the silicone hydrogel surface, and the hydrogel top coating is nested on top of the plasma layer. This nested structure ensures that the thickest protective layer (hydrogel top coating) is positioned farthest from the ocular environment, providing maximum protection
5Reliability
If LbL coatings are used to modify hydrophilicity, then the surface wettability is improved, but the susceptibility to antimicrobial deposition increases due to high negative surface charges
Solution Approach 1:
The invention applies different charge characteristics to different parts of the coating structure. The plasma base coating provides a controlled charge environment, while the hydrogel top coating is formulated to reduce overall negative surface charges. This local quality differentiation maintains surface wettability while reducing antimicrobial attraction
6Strength
If crosslinking of LbL coatings is used to improve durability, then the coating strength is improved, but the hydrophilicity and lubricity deteriorate
Solution Approach 1:
The coating is segmented into two functional layers with different properties: the plasma base coating provides strong adhesion and hydrophilicity, while the hydrogel top coating provides lubricity and maintains hydrophilicity. This segmentation allows the adhesive layer to be crosslinked for strength while the top layer remains hydrophilic and lubricious
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 a contact lens with improved hydrophilicity, durability, and reduced friction, maintaining oxygen permeability and mechanical integrity while preventing antimicrobial accumulation, ensuring comfort and effectiveness over extended wear.
Implementation Method 1
a plasma base coating which is chemically-attached directly onto the surface of the silicone hydrogel contact lens
Implementation Method 2
chemically-attached directly onto the surface
Implementation Method 3
heating the soft contact lens precursor obtained in step (2), in a second aqueous coating solution which comprises a water-soluble and thermally-crosslinkable hydrophilic polymeric material at a temperature of from about 60° C. to about 140° C. for at least 30 minutes to crosslink the water-soluble thermally-crosslinkable hydrophilic polymeric material
Data Source
AI summary
The invention is related to a method for producing soft contact lenses comprises a silicone hydrogel lens body and a composite coating thereon. The composite coating comprises: a plasma base coating which is chemically-attached directly onto the surface of the silicone hydrogel contact lens and functions as a fail-proof measure for ensuring the hydrophobic silicone hydrogel lens material to be shielded from any exposure to ocular environments even after at least 30 days of daily uses including daily waring and daily cleaning/disinfecting; and a relatively-durable lubricious hydrogel top coating for ensuring wearing comfort. A method of the invention comprises forming a plasma-reactive hydrophilic polymer hybrid base coating having reactive functional groups on a silicone hydrogel contact lens and heating the silicone hydrogel contact lens with the hybrid base coating in an aqueous solution of a water-soluble and thermally crosslinkable hydrophilic polymeric material to form a stable lubricious hydrogel coating thereon. This method has a minimized adverse impact on the mechanical properties of silicone hydrogel lens body.