Asymmetric Membrane Surface Porosity for Viscous Fluid Filtration
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Solution Overview
Problem
Asymmetric membranes tend to prematurely clog and have poor throughput when used with viscous or heavily loaded streams, such as food syrups, serum, and blood products, despite their high flux and throughput in water-based solutions.
Innovation Solution
Increasing the surface porosity of the tight side of asymmetric membranes by adjusting the dew point and lacquer solids concentration during the casting process or post-casting treatments like mechanical abrasion, chemical exposure, or irradiation to create a highly porous reticulated surface.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the tight side surface is made dense to achieve high flux in water-based solutions, then throughput is improved, but the membrane clogs prematurely when used with viscous or heavily loaded streams
Solution Approach 1:
The membrane is designed with different surface properties at different locations: the tight side has a reticulated porous structure with larger pores to prevent clogging, while the bulk maintains the asymmetric gradient structure for high flux. This local differentiation allows the membrane to handle viscous streams without sacrificing throughput capability.
Solution Approach 2:
The tight side surface is transformed from a dense structure to a reticulated porous structure with interconnected larger pores. This porous configuration allows viscous and heavily loaded streams to pass through without clogging, while the underlying asymmetric structure maintains high flux performance for water-based solutions.
2Reliability
If the tight side surface is made porous to prevent clogging, then reliability is improved, but flux decreases in water-based solutions
Solution Approach 1:
The membrane structure is segmented into distinct regions: a reticulated porous tight side surface for clogging resistance, a transition zone, and a porous bulk structure for high flux. This segmentation allows each region to optimize its function without compromising the other.
Solution Approach 2:
The reticulated porous structure is nested within the asymmetric membrane architecture. The larger pores of the reticulated surface are positioned upstream, containing the flux-generating asymmetric structure within them, allowing both clogging resistance and high flux to coexist.
3Manufacturing precision
If a dense skin is formed on the tight side to achieve high separation performance, then purification is improved, but throughput with viscous fluids deteriorates
Solution Approach 1:
The dense skin is replaced with a reticulated porous surface layer that has larger, interconnected pores. This porous structure maintains separation performance by providing sufficient pore density while allowing viscous fluids to pass through with reduced resistance, improving throughput.
Solution Approach 2:
The membrane combines two distinct structural features: a reticulated porous surface layer for low resistance to viscous flow and an asymmetric gradient structure for high separation performance. This composite structure integrates the benefits of both dense and porous configurations.
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 modified membranes exhibit higher throughput and flux, effectively filtering viscous fluids like serum and plasma with reduced clogging, as demonstrated by improved flow times and flux rates compared to unmodified membranes.
Implementation Method 1
adjusting the dew point near the surface of a freshly cast asymmetric membrane
Implementation Method 2
asymmetric membranes having a substantially reticulated surface microstructure by increasing the surface porosity of a tight side
Data Source
Figure 1A~1B
Figure 2A~2B
Figure 3~4
AI summary
A microporous asymmetrical membrane formed of one or more layers wherein the "tight" side of the membrane has an "opened" face or otherwise highly-porous reticulated surface is described. The microporous asymmetrical membrane has high throughput and high flux, even when used for filtering viscous materials, such as serum or plasma. The membrane's surface can be formed by ablation or solvation, or in a two or more layered structure, through an appropriate selection of casting dopes.