Composite Storage Bag Lap Seam Sealing for Cryopreservation
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current cryopreservation storage bags face issues with durability at freezing temperatures, leakage, and interaction of plastic extractables with biologic drug substances, particularly at the ends and corners.
Innovation Solution
A composite storage bag is formed with an inner surface of a higher melting non-melt-processible polymer and an outer surface of a lower melting melt-processible polymer, featuring a lap seam joint constructed between the melting points of the two polymers to enhance durability and reduce leakage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a single polymer material is used for the storage bag, then the manufacturing process is simple, but the bag exhibits poor durability at freezing temperatures and has high extractables that interact with drug substances
Solution Approach 1:
The storage bag uses a composite structure with an inner layer of non-melt-processible polymer (such as PTFE or polyimide) and an outer layer of melt-processible polymer (such as FEP). This composite material approach provides both the chemical inertness and low extractables of fluoropolymers and the durability at freezing temperatures through the combination of materials with complementary properties.
Solution Approach 2:
Different regions of the storage bag have different material properties - the inner surface facing the drug substance uses a non-melt-processible polymer for chemical compatibility and low extractables, while the outer surface uses a melt-processible polymer for durability and ease of sealing. This local differentiation of material quality resolves the contradiction between simplicity and performance.
2Reliability
If conventional sealing methods are used at the ends and corners, then the manufacturing process is simple, but leakage problems occur particularly at these locations
Solution Approach 1:
The sealing process utilizes temperature parameter changes by heating the bag to a temperature between the melting points of the two polymers. At this intermediate temperature, the melt-processible outer polymer becomes sufficiently soft to allow sealing while the non-melt-processible inner polymer remains stable. This parameter-based approach enables reliable sealing at corners and ends without excessive process complexity.
Solution Approach 2:
The bag is pre-formed as a composite tube with the two-layer structure before sealing. This preliminary formation of the composite structure ensures that the material properties are optimized for sealing before the actual sealing operation, allowing for more reliable sealing at critical locations like corners and ends.
3Object-affected harmful factors
If a non-melt-processible polymer is used for the inner surface, then extractables interaction with drug substances is minimized, but conventional sealing processes cannot be applied
Solution Approach 1:
The storage bag employs a composite material system where the inner layer (non-melt-processible polymer like PTFE or polyimide) provides chemical inertness and low extractables interaction, while the outer layer (melt-processible polymer like FEP) provides sealability. This composite approach allows both requirements to be satisfied simultaneously - the inner surface protects the drug substance while the outer surface enables conventional sealing processes at intermediate temperatures.
Solution Approach 2:
The melt-processible outer polymer acts as an intermediary layer that enables sealing operations. During sealing, this outer layer softens at intermediate temperatures to allow bonding while the inner non-melt-processible layer remains chemically stable and does not interact with the drug substance. The intermediary outer layer mediates between the conflicting requirements of chemical inertness and sealability.
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 solution provides improved durability and reduced leakage in cryopreservation bags, maintaining protein stability and minimizing interactions with drug substances, thereby enhancing the storage and transportation of biologics.
Implementation Method 1
forming a joint at one of the ends at a temperature between respective melting points of the higher melting polymer and the lower melting polymer
Implementation Method 2
disposing the composite sheet over the joint such that the first side comprising a lower melting polymer engages the joint and forming a lap seam over the joint
Data Source
AI summary
A method of making a storage bag comprising the following steps performed in any order: (a) forming a composite tube having an inner surface comprising a higher melting polymer, an outer surface comprising a lower melting polymer, two ends, and a diameter; (b) flattening the tube in a direction perpendicular to the diameter; (c) forming a joint at one of the ends at a temperature between respective melting points of the higher melting polymer and the lower melting polymer; (d) providing a composite sheet having a first side comprising a higher melting polymer and a second side comprising a lower melting polymer; and (e) disposing the composite sheet over the joint such that the first side comprising a lower melting polymer engages the joint and forming a lap seam over the joint at a temperature between respective melting points of the higher melting polymer and the lower melting polymer, and a storage bag made by such method.