Embedded Hydrogel Contact Lens Bonding to Prevent Delamination
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Solution Overview
Problem
Hydrogel contact lenses with embedded rigid inserts are susceptible 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 an insert-forming composition with a free-radical initiator and iniferter to create a crosslinked polymeric insert, which is then covalently linked to a bulk hydrogel material during lens formation, minimizing delamination through iniferter-induced polymerization and covalent bonding.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If rigid inserts are embedded in silicone hydrogel contact lenses, then vision correction and corneal health functions are improved, but delamination and lens distortion occur during hydration due to different water-swelling degrees
Solution Approach 1:
The insert is pre-formed with a surface that has chemical groups capable of covalent bonding before being embedded in the hydrogel lens. This preliminary preparation ensures that when the lens is manufactured, the insert can form strong covalent bonds with the hydrogel matrix, preventing delamination during subsequent hydration and wear.
Solution Approach 2:
The invention creates a composite structure where a rigid insert (made of materials like PMMA, silicone, or other rigid polymers) is combined with silicone hydrogel lens material through covalent bonding. This composite approach allows the rigid insert to provide optical correction while the hydrogel provides comfort and oxygen permeability, with the covalent bond ensuring structural integrity during hydration.
2Ease of manufacture
If conventional cast-molding process is used to produce hydrogel contact lenses, then manufacturing simplicity is maintained, but delamination occurs during hydration due to mechanical property differences between insert and lens material
Solution Approach 1:
The invention modifies the chemical parameters of the insert surface by incorporating specific functional groups (such as carboxyl, hydroxyl, amine, or isocyanate groups) that can form covalent bonds with the hydrogel matrix. This chemical parameter change enables strong bonding while maintaining the simplicity of the conventional cast-molding process.
Solution Approach 2:
The covalent bond acts as an intermediary mechanism between the rigid insert and the hydrogel lens material. This chemical bond serves as a strong connection that bridges the mechanical property differences between the two materials, preventing delamination during hydration without complicating the manufacturing process.
3Adaptability or versatility
If rigid inserts with different water-swelling properties are embedded in hydrogel lenses, then optical correction is enhanced, but lens distortion occurs during hydration
Solution Approach 1:
The insert is pre-formed with appropriate dimensions and surface chemistry before embedding. This preliminary action ensures that the insert fits precisely within the lens mold and forms covalent bonds that maintain the overall lens shape during hydration, preventing distortion while preserving optical correction capabilities.
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 produces embedded hydrogel contact lenses with reduced susceptibility to delamination, ensuring structural integrity and stability during hydration and wear.
Implementation Method 1
initiating iniferter-induced polymerization of the lens-forming composition at and near the surface of the insert
Implementation Method 2
the insert-forming composition comprises (i) at least one polymerizable material, (ii) at least one first free-radical initiator
Implementation Method 3
During hydration, the hydrogel contact lenses will absorb water and typically can swell significantly in size
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 iniferter moieties covalently attached thereto; 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; curing 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.