Silicone Hydrogel Contact Lens Transferable LbL Coating
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Solution Overview
Problem
There is a need for a cost-effective method to produce silicone hydrogel contact lenses with a durable and wettable surface, as existing methods such as plasma treatment are costly and LbL coatings may not be durable enough for extended wear.
Innovation Solution
A method involving the application of transferable LbL coatings on mold surfaces during the molding process, using polyionic materials and non-crosslinkable hydrophilic polymers to create a durable and wettable surface on silicone hydrogel contact lenses, where the coatings detach from the mold and reattach to the lens, promoting entanglement with the polymer matrix for enhanced durability.
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 becomes more wettable and resistant to lipid/protein deposition, but the production cost increases due to equipment investment and additional processing steps
Solution Approach 1:
The patent uses a disposable mold with pre-applied LbL coating instead of expensive reusable plasma treatment equipment. The mold is discarded after a single use, eliminating the need for costly plasma treatment infrastructure while achieving the same surface modification effect on the lens during the molding process itself
Solution Approach 2:
The patent combines the surface coating application and lens molding operations into a single integrated process. The LbL coating is applied to the mold surface beforehand, and during lens formation, the coating transfers to the lens surface, merging two separate steps (coating and molding) into one simultaneous operation that reduces overall process complexity and cost
2Ease of manufacture
If LbL coating is applied to silicone hydrogel contact lenses to improve wettability, then the production cost is reduced, but the coating durability is insufficient for extended wear applications
Solution Approach 1:
The patent applies the LbL coating to the mold surface in advance, before lens molding. This preliminary action ensures the coating is already in position and properly adhered to the mold, allowing it to transfer effectively to the lens during molding and achieve sufficient durability for extended wear
Solution Approach 2:
The patent uses the mold surface as an intermediary carrier for the LbL coating. The coating is first applied to the mold, then transfers to the lens during molding. This intermediary approach allows the coating to achieve proper adhesion and durability that would be difficult to obtain through direct coating of the finished lens
3Ease of operation
If wetting agents are incorporated into the lens formulation, then the surface becomes wettable without additional processing steps, but the wetting effect is not durable over time and hydrophobic spots remain susceptible to lipid/protein adsorption
Solution Approach 1:
The patent changes the fundamental approach from incorporating soluble wetting agents into the lens bulk material to applying an insoluble LbL coating on the lens surface. This parameter change from internal to external modification ensures the wettability effect persists indefinitely without depleting, as the coating forms a stable, adherent layer that does not migrate or degrade over time
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 silicone hydrogel contact lens with a wettable and durable surface that can survive multiple digital rubbing tests, maintaining hydrophilicity and resistance to lipid/protein adsorption, while reducing production costs.
Implementation Method 1
the non-crosslinkable hydrophilic polymer is capable of forming an interfacial film at interface between the coated molding surfaces and the lens-forming fluid material
Implementation Method 2
soaking the transferable LbL coatings with the lens-forming fluid material for a time period sufficient both to allow the non-crosslinkable hydrophilic polymer in the interface film penetrate into the transferable LbL coatings and to entangle with coating materials
Data Source
AI summary
The invention provides a cost-effective method for making a silicone hydrogel contact lens which has a good wettable coating with a good durability.