Vacuum Filtration Head Shielding Against Membrane Retro-Contamination
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Solution Overview
Problem
Current vacuum filtration systems face the risk of retro-contamination of membrane filters due to micro-droplets generated by residual liquid and air, leading to false positive results and increased costs in microbiological testing.
Innovation Solution
The introduction of a protective shield in the filtration head that blocks direct connections between the drain channel opening and the membrane filter, while maintaining a fluid path, reducing the void volume and preventing micro-droplet contamination.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the drain chamber volume is increased to prevent retro-contamination, then the risk of retro-contamination is reduced, but the size of the filtration head increases
Solution Approach 1:
The drain chamber is divided into two functional zones by the shield: a first region that receives liquid from the membrane filter and a second region that communicates with the drain channel. This segmentation prevents direct communication between the drain channel opening and the membrane filter, blocking the path for micro-droplet retro-contamination while maintaining a compact overall structure without requiring excessive volume increase.
2Reliability
If the distance between the liquid level and the back surface of the membrane filter is increased, then retro-contamination risk is reduced, but the filtration head size increases
Solution Approach 1:
Instead of increasing the vertical distance between liquid level and membrane filter (one-dimensional solution), the shield introduces a spatial barrier that blocks the direct line-of-sight path for micro-droplet travel. This multi-dimensional approach to blocking contamination paths allows maintaining compact filtration head dimensions while effectively preventing retro-contamination.
3Reliability
If a three-way valve is installed to flush the drain channel, then retro-contamination is prevented, but the device complexity and time consumption increase
Solution Approach 1:
The shield extracts and blocks the harmful direct communication path between the drain channel opening and the membrane filter. By removing this direct connection, the system eliminates the need for complex valve systems and flushing procedures, achieving retro-contamination prevention through a simple passive geometric barrier that requires no additional control mechanisms.
4Volume of stationary object
If the void volume of the drain chamber is reduced, then material and footprint are optimized, but the accommodation space for residual liquid is reduced
Solution Approach 1:
The shield creates localized functional regions within the drain chamber: the first region provides sufficient space to accommodate residual liquid and protect the membrane filter from retro-contamination, while the second region maintains necessary fluid communication with the drain channel. This local differentiation of space quality allows optimizing the overall void volume and footprint while ensuring each region performs its specific function effectively.
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
Reduces the risk of retro-contamination, minimizes false positive results, and optimizes the filtration process by reducing material and footprint, while allowing for efficient buffer liquid use and easier cleaning.
Implementation Method 1
perform the filtration by reducing the pressure downstream from an outlet drain channel of the filtration head by means of a vacuum pump in order to actively draw the liquid sample through the filtration membrane by the pressure differential on both sides of the membrane
Implementation Method 2
The filter membrane captures microorganisms of interest and is accordingly arranged in the fluid flow path between the sample reservoir and the drain chamber
Implementation Method 3
a (protective) shield separate from the support arranged in the filtration head so as to block a fictive direct line connection between the opening of the drain channel into the drain chamber and the membrane filter
Data Source
Figure 1~2
Figure 3~4
Figure 5a~5c
AI summary
A filtration head (1) for vacuum filtration, the filtration head (1) comprising a receptacle for a support (2) for a membrane filter (3) for microbiological testing of a liquid substance to be drawn from an upstream side of the membrane filter (3) to a downstream side of the membrane filter (3) through the membrane filter (3), or the support (2) for such membrane filter (1), a drain chamber (4) located downstream of the support (2) and communicating with a downstream side of the membrane filter (3) when the membrane filter (3) is in place on the support (2) to receive the liquid substance that has passed through the membrane filter (3), and a drain channel (5) communicating with the drain chamber (4) at an opening (9) and intended to communicate, in use, with downstream equipment including a vacuum pump to drain the liquid substance. A protective shield (6) is arranged in the filtration head (1) so as to block/interfere with a fictive direct line connection between the opening (9) of the drain channel (5) into the drain chamber (4) and the membrane filter (3), while retaining a fluid path (7) to the drain channel (5) past the protective shield (6).