Multi-Stage Sealing for Contact Lens Packaging Thermal Stress
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Solution Overview
Problem
Traditional contact lens packaging methods face challenges in minimizing thermal stress during the sealing process, leading to potential seal leaks, crumpled packages, and compromised sterility due to differential expansion and contraction of internal contents, which requires robust materials and complex sealing processes.
Innovation Solution
A multi-stage sealing method is introduced, where a first seal portion is formed with a gap that allows fluid escape during the initial sealing stage, followed by a second seal portion with different properties to completely seal the gap, reducing thermal stress and enabling the use of less robust materials while maintaining sterility.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a high temperature heated press is used to bond the multi-layer film to the boat, then the film layer is bonded along the outer perimeter of the boat, but the boat, film layer, and aqueous solution heat and expand creating significant strain on the seal
Solution Approach 1:
The sealing process is divided into multiple stages: a first seal is formed initially, then a second seal is formed after the package has cooled down. This segmentation allows the thermal expansion strain to be released between sealing operations, preventing seal failure while maintaining strong seals.
Solution Approach 2:
The first seal is formed preliminarily before the thermal expansion occurs during autoclaving. This preliminary seal allows the package to undergo heating and expansion, then the second seal is formed after cooling to lock in the sealed state without experiencing the full expansion strain.
2Strength
If preformed stiff packaging is used to protect the lens from damage, then the lens is protected, but the package becomes more difficult to open and costs increase
Solution Approach 1:
The package uses a compliant boat material that is flexible rather than stiff, and the seal is designed with specific local properties (first seal and second seal with different characteristics) that allow the package to be protective yet easily opened by applying force at the seal location.
3Reliability
If a multi-layer film is used to bond and seal the lens within the boat, then the seal provides durability, but the sealing process becomes time consuming and reduces production rates
Solution Approach 1:
The sealing operation is segmented into two distinct sealing steps rather than one long continuous seal, which can be more efficiently executed and allows for process optimization, maintaining durability while improving production throughput.
4Strength
If robust materials are used to withstand thermal expansion forces, then the seal withstands expansion forces, but the packaging cost increases
Solution Approach 1:
The sealing process parameters are changed by performing sealing at different thermal states (hot sealing then cool sealing), which allows the use of less robust, lower-cost materials while still achieving the required seal strength and durability.
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
This approach minimizes thermal damage, ensures a stronger seal, and allows for the use of thinner, lighter packaging materials, improving sterility assurance and reducing production costs while making the package easier to open.
Implementation Method 1
The boat, the film layer, and the seal itself must be sufficiently resilient to withstand the forces created by the expansion during heating
Implementation Method 2
The sealing heads of the heated press are heated and used to press the film layer against the outer perimeter of the boat
Implementation Method 3
The sealing heads of the heated press are heated and used to press the film layer against the outer perimeter of the boat
Implementation Method 4
The blister pack is then autoclaved using steam and pressure to ensure sterility
Implementation Method 5
The blister pack is then autoclaved using steam and pressure to ensure sterility
Implementation Method 6
the second seal portion closes the gap. The gap allows a flow of fluids after a formation of the first seal
Data Source
AI summary
A contact lens package may include a first package layer, a second package layer, a lens receiving area defined between the first and second package layers, a first seal portion between the first and second package layers extending around a first portion of the lens receiving area, a second seal portion between the first and second package layers extending around a second portion of the lens receiving area, and the second seal portion having different sealing properties than the first seal portion. The second seal portion together with the first seal portion complete a seal around the lens receiving area. The first seal portion defines an unsealed gap at a location around the lens receiving area, and the second seal portion closes the gap. The gap allows a flow of fluids after a formation of the first seal.