Polymeric Membrane Drying Sequence for Surfactant Retention
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Solution Overview
Problem
Existing methods for manufacturing porous dry cast membranes, such as those used in diagnostic tests, face challenges in removing dust particles and retaining surfactants, which affect the hydrophilicity and performance of the membranes, leading to increased manufacturing costs and quality variability.
Innovation Solution
A method involving initial drying of the membrane to evaporate most solvents and fix surfactants within the polymeric structure, followed by surface dust removal, which enhances surfactant retention and improves hydrophilicity without compromising membrane properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If cleansing is performed before drying (as in prior art), then dust particles are removed, but surfactant is lost and hydrophilicity decreases
Solution Approach 1:
The patent applies preliminary drying before cleansing to fix the surfactant in the membrane structure. By evaporating most solvent first, the surfactant becomes immobilized in the forming polymeric network, preventing its loss during subsequent dust removal operations. This sequence reversal (drying before cleansing instead of cleansing before drying) resolves the contradiction by protecting surfactant while still achieving dust removal.
2Manufacturing precision
If cleansing is performed on wet membrane (5-20% solvent remaining), then impurities are removed more effectively, but surfactant loss increases
Solution Approach 1:
The patent performs preliminary drying to reduce solvent content to below 5% before cleansing, which fixes the surfactant in the membrane structure first. This preliminary action of drying creates a matrix that retains surfactant while still allowing effective impurity and dust removal during the subsequent cleansing step.
3Quantity of substance
If post-treatment with surfactant solution is applied to compensate for surfactant loss, then surfactant content is restored, but manufacturing complexity and cost increase
Solution Approach 1:
The patent uses preliminary drying as a preventive measure to avoid surfactant loss in the first place, rather than using post-treatment to compensate for loss. This eliminates the need for additional surfactant solution application steps, reducing manufacturing complexity while maintaining surfactant content.
Solution Approach 2:
The patent inverts the conventional sequence of operations by drying before cleansing instead of cleansing before drying. This inversion prevents surfactant loss at the source, making post-treatment unnecessary and simplifying the overall manufacturing process.
4Object-affected harmful factors
If conventional cleansing methods are used, then dust removal is achieved, but hydrophilicity and application performance decrease
Solution Approach 1:
The patent applies preliminary drying to fix surfactant in the membrane structure before dust removal. This ensures that surfactant remains available to provide hydrophilicity and biomolecule binding capability, maintaining diagnostic application performance while still achieving effective dust removal.
Solution Approach 2:
The patent changes the parameter of solvent content from high (conventional cleansing on wet membrane) to low (below 5% solvent remaining) before cleansing. This parameter change fixes the surfactant in the membrane structure, preserving hydrophilicity and diagnostic performance while enabling effective dust removal.
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 results in significantly higher residual surfactant levels and improved consistency and reproducibility of the membranes, enhancing their performance in diagnostic applications while reducing manufacturing costs.
Implementation Method 1
due to the continuous evaporation of the applied solvents in the presence of the non-solvent, a porous polymeric layer, the target membrane, is formed
Implementation Method 2
the presence of residual surfactant content within the finished membrane has a major impact on the customer application performance, since the surfactant content affects the hydrophilicity of the finished membrane
Data Source
AI summary
Disclosed is a method and apparatus for manufacturing a continuous web of polymeric membrane and for continuous downstream processing of said web. The apparatus (10) comprises: a casting station (20) for casting the continuous web (M); a carrier (24) for carrying the web downstream; a membrane drier (30) downstream of the carrier, for drying the web; and a brushing station (40) downstream of the drier for brushing the web. Said drier is located immediately downstream of the carrier, and upstream of said brushing station. The apparatus (10) further includes an additional drying station (50) downstream of the brushing station (40). Brushing after drying retains more surfactant in the membrane which is useful for certain applications. In addition, initial drying eliminates virtually all solvents from the membrane, but leaves some non-solvent (e.g. water) within it, which in turn fixes the surfactant on the nitrocellulose fibers, which improves significantly the consistency and reproducibility of the membrane.