Filter Vial Plunger Sealing and Dead Volume Reduction
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Solution Overview
Problem
Current filter vials face challenges in sealing and fluid retention due to variations in filter diameter and thickness, leading to fluid bypass and contamination, with existing solutions failing to efficiently process all fluid samples, especially for small volumes.
Innovation Solution
A filter vial apparatus with a tubular design featuring a protrusion at the bottom, an annular recess, and a plunger assembly with a cap that forms a fluid-tight seal, ensuring all fluid passes through the filter by using shallow channels and a frustoconical shape to minimize dead volume and prevent contamination.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If ultrasonic welding is used to attach filters to vial walls, then filtration effectiveness is improved, but plasticizer contamination of the fluid increases
Solution Approach 1:
The invention removes the ultrasonic welding step and associated plasticizers from the system by using a mechanical press-fit connection between the plunger assembly and vial. The filter remains attached to the plunger without requiring ultrasonic welding to the vial walls, thereby eliminating the source of plasticizer contamination while maintaining filtration effectiveness.
Solution Approach 2:
The plunger assembly with filter is designed as a disposable component that is pressed into the vial for use and then discarded. This eliminates the need for permanent attachment methods like ultrasonic welding, avoiding plasticizer contamination from reusable components while maintaining effective filtration during the service life of the device.
2Adaptability or versatility
If filters with varying diameter and thickness are used, then filtration capability is improved, but sealing reliability deteriorates
Solution Approach 1:
The invention creates a localized sealing zone at the interface between the plunger assembly and vial using an elastomeric material. This sealing zone accommodates variations in filter dimensions by providing a compliant, conforming seal that adapts to the specific geometry of each filter while maintaining reliable sealing, thus allowing use of filters with varying diameter and thickness.
Solution Approach 2:
The invention uses an elastomeric material with specific physical properties (compliance, conformability) that allow the seal to adapt to dimensional variations. The elastomeric nature of the sealing material enables it to deform and conform to filters with different diameters and thicknesses, maintaining sealing reliability despite parameter variations in the filter components.
3Reliability
If the plunger is designed to fit tightly in the vial, then fluid sealing is improved, but dead volume at the bottom increases
Solution Approach 1:
The invention solves the sealing problem not by increasing radial interference fit, but by using a frustoconical geometry in the axial dimension. The tapered shape of the plunger assembly creates sealing through axial engagement and geometric constraint rather than radial compression, allowing the bottom of the plunger to sit close to the vial bottom without requiring excessive tightness that would create dead volume.
Solution Approach 2:
The frustoconical (tapered) geometry of the plunger assembly provides sealing through its curved, converging surfaces that guide and seal fluid flow. This curved geometry creates effective sealing with minimal dead volume by directing fluid along the tapered surfaces into the plunger, avoiding the need for tight radial fits that would trap fluid at the bottom.
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 apparatus effectively seals and processes nearly all fluid samples, minimizing contamination and retaining nearly all fluid within the plunger, especially beneficial for small volumes, by ensuring a snug fit and efficient fluid passage through the filter.
Implementation Method 1
fluid passes through the filter and into the plunger in order to separate the fluid from particles or molecules too large to pass through the filter
Implementation Method 2
an outer surface of the outer sidewall of the cap has a diameter sufficiently larger than diameter D to form a fluid tight seal when the plunger assembly is inserted into the vial
Data Source
Figure 1A~1C
Figure 2A~2C
Figure 3A~3C
AI summary
A filter vial for separating biological and chemical fluids has a cylindrical sidewall with an open top and a closed bottom. A protrusion extends upwards from the middle of the bottom to form an annular recess. A tubular plunger has an open bottom end to which is fastened an annular cap having an outer sidewall sized to fit into and seal against the vial's sidewall. An inner sidewall of the annular cap holds a filter over an opening in the bottom of the plunger and forms a shaped cavity leading to that filter. The annular cap on the plunger fits into the annular recess in the vial to force fluid from the vial through the filter and into the plunger.