Embedded Hydrogel Contact Lens Bonding Against Insert Delamination
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Solution Overview
Problem
Hydrogel contact lenses with embedded rigid inserts are prone to delamination due to significant differences in mechanical properties and water-swelling between the insert material and the silicone hydrogel lens material, leading to lens distortion during hydration and handling.
Innovation Solution
A method involving the use of a thermal free-radical initiator and a free-radical photoinitiator with ethyleneically-unsaturated groups to form a covalent linkage between the insert and the bulk hydrogel material, ensuring the insert is crosslinked and photoactive, allowing for photocuring-based cast-molding to create a stable embedded hydrogel contact lens.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If rigid inserts are embedded in silicone hydrogel contact lenses, then vision correction performance is improved, but delamination occurs during hydration due to mechanical property differences
Solution Approach 1:
The patent applies preliminary action by incorporating photoinitiators and crosslinking agents into the lens material before the insert is embedded. The covalent bonding is established in advance during the lens fabrication process, creating predetermined bonding sites that will form strong chemical bonds between the insert and lens material before hydration occurs, thereby preventing delamination during subsequent hydration and wear.
Solution Approach 2:
The patent employs composite materials by combining silicone hydrogel lens material with rigid insert materials (such as RGP or PMMA) to create a multi-material contact lens structure. The lens material contains incorporated photoinitiators and crosslinking agents that enable covalent bonding between the different materials, creating a composite structure that maintains the optical properties of the rigid insert while preventing delamination through chemical bonding.
2Measurement precision
If rigid inserts with different mechanical properties are embedded in hydrogel lenses, then optical performance is improved, but lens distortion occurs during hydration
Solution Approach 1:
The patent applies preliminary action by pre-incorporating photoinitiators and crosslinking agents into the lens material before hydration. This creates a covalently bonded network that is established in advance, constraining the rigid insert and preventing lens distortion when the lens absorbs water during hydration, thereby maintaining both optical performance and shape stability.
Solution Approach 2:
The patent applies parameter changes by modifying the chemical composition of the lens material to include photoinitiators and crosslinking agents. This changes the bonding parameters between the insert and lens material from weak physical adhesion to strong covalent bonding, which maintains lens shape stability during hydration while preserving the optical properties of the rigid insert.
3Ease of manufacture
If conventional physical adhesion is used between insert and lens material, then manufacturing simplicity is maintained, but bonding strength is insufficient
Solution Approach 1:
The patent replaces mechanical/physical adhesion systems with chemical bonding systems. Instead of relying on physical adhesion between the insert and lens material, the lens material incorporates photoinitiators and crosslinking agents that form covalent bonds with the insert, creating a chemical bonding system that provides significantly stronger and more reliable attachment.
Solution Approach 2:
The patent uses composite materials by combining the lens material with incorporated photoinitiators and crosslinking agents to create a chemically active composite. This composite material system enables covalent bonding with the rigid insert, transforming the bonding mechanism from weak physical adhesion to strong chemical bonding while maintaining manufacturability through integrated formulation.
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 enhances the resistance to delamination by creating a covalent bond between the insert and the bulk hydrogel material, improving the stability and durability of the embedded hydrogel contact lenses.
Implementation Method 1
a free-radical photoinitiator that comprises an ethyleneically-unsaturated group and a photoiniator-moiety capable of generating free radicals upon irradiation by an UV and/or visible light
Implementation Method 2
a thermal free-radical initiator
Data Source
AI summary
A method for producing embedded hydrogel contact lenses comprises at least the following steps: obtaining an insert made of a crosslinked polymeric material comprising repeating units of a free-radical photoinitiator; placing the insert in a female lens mold half; dosing an amount of a lens-forming composition to immerse the insert in the female lens mold half; closing tightly a male lens mold half onto the top of the female lens mold half halves to form a molding assembly; actinically curing both the lens-forming composition in the molding assembly to form an embedded hydrogel lens precursor which comprises a bulk hydrogel material formed the lens-forming composition and the insert that is embedded therein and covalently linked to the bulk hydrogel material.