Rotatable Disc Test Element for Centrifugal Flow Control
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Solution Overview
Problem
Existing disc-shaped test elements based on centrifugal and capillary forces face challenges in controlling reaction specificity and residence times of sample liquids, particularly in immunoassays, leading to reduced detection accuracy due to immobilization difficulties and volume limitations.
Innovation Solution
A disk-shaped test element with a central axis, featuring a sample introduction opening, a capillary-active zone with immobilized reagents, and a sample channel that utilizes both centrifugal and capillary forces for precise control of liquid flow, allowing targeted reaction conditions and efficient reagent interaction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If centrifugal and capillary forces are used for sample transport in disc-shaped test elements, then miniaturization and parallelization are enabled, but control of reaction specificity and residence times deteriorates
Solution Approach 1:
The test element is divided into distinct functional zones: a sample application zone, a reaction zone with immobilized reagents, and a separate detection zone. This segmentation allows each zone to perform its specific function optimally while maintaining overall miniaturization. The sample channel connects these zones, enabling controlled transport through capillary and centrifugal forces.
Solution Approach 2:
The system dynamically controls sample transport by adjusting rotation speed to switch between capillary-dominated flow (for precise residence time control in reaction zones) and centrifugal-dominated flow (for rapid sample introduction and waste removal). This dynamic control enables reliable reaction specificity despite the miniaturized format.
2Measurement precision
If reagent immobilization is attempted in disc-shaped test elements, then detection accuracy should improve, but immobilization difficulty increases
Solution Approach 1:
The test element incorporates a porous matrix material in the reaction zone that provides high surface area for reagent immobilization. The porous structure enables efficient reagent loading while maintaining ease of manufacture through simple impregnation or adsorption processes. The capillary forces within the porous structure also help retain reagents in place during rotation.
Solution Approach 2:
The test element uses composite construction combining a rigid disc substrate with a porous reaction matrix and hydrophobic barrier layers. This composite structure facilitates reagent immobilization in the porous zone while the hydrophobic barriers prevent reagent leakage, achieving both detection accuracy and manufacturing simplicity.
3Quantity of substance
If sample volume is reduced in miniaturized test elements, then reagent consumption decreases, but detection accuracy deteriorates
Solution Approach 1:
The test element concentrates reagents and sample in a localized reaction zone with optimized geometry and porous structure. This local quality enhancement ensures that even with reduced overall sample volume, the binding reactions occur in a region with sufficient reagent-sample interaction, maintaining detection accuracy while minimizing reagent and sample consumption.
Solution Approach 2:
The test element design copies the essential functional features of larger test strips into a miniaturized disc format, preserving the critical sample-reagent interaction volume in the reaction zone. By replicating the key functional architecture at smaller scale, detection accuracy is maintained despite reduced total sample volume.
4Device complexity
If capillary forces are used for liquid transport, then external driving forces are eliminated, but control of liquid flow precision deteriorates
Solution Approach 1:
The system dynamically balances capillary and centrifugal forces by controlling rotation speed. At low or zero rotation, capillary forces dominate providing passive, simple liquid transport. At higher rotation speeds, centrifugal forces take over for rapid sample introduction and waste removal. This dynamic switching enables precise liquid flow control without complex additional mechanisms.
Solution Approach 2:
The test element design changes the dominant transport mechanism parameter by adjusting rotation speed. This parameter change allows the system to switch between capillary-dominated precise flow control and centrifugal-dominated rapid transport, achieving both precision and efficiency without increasing device complexity.
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 enables precise control of liquid flow and reagent interaction, enhancing binding efficiency and reducing reagent and sample volume requirements, thereby improving detection accuracy and minimizing depletion effects.
Implementation Method 1
the liquid sample is transported from an end of the capillary-active zone which is farther from the axis to an end closer to the axis by capillary forces
Implementation Method 2
Disc-shaped test carriers, so-called LabDiscs or optical BioDiscs, further develop the concept of controlled sample transport using centrifugal force
Data Source
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AI summary
The invention relates to a test element that is essentially disc-shaped and flat and rotatable about an axis perpendicular to the disc-shaped test element plane, comprising a sample introduction opening for introducing a liquid sample, a capillary-active zone, in particular a porous, absorbent matrix, with a first end far from the axis and a second end close to the axis, and a sample channel extending from a region close to the axis to the first end far from the axis of the capillary-active zone. The invention further relates to a method for determining an analyte using the test element.