Capillary Sample Loading System with Timing Control
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Solution Overview
Problem
In capillary-driven microfluidic systems, accurately metering a specific volume of fluid is challenging due to the inability to shut off the fluid stream once it starts, leading to excess sample processing in applications like blood cell differentiation or counting.
Innovation Solution
A sample loading system with a metering volume reservoir and a second fluid reservoir, controlled by capillary valves and timing circuitry, allows for automatic and precise metering by varying flow resistances and timing, eliminating the need for active pumps and enabling passive operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If capillary-driven systems are used for fluid transport, then active pumps are eliminated and reliability is improved, but the ability to shut off fluid stream and precisely control volume is lost
Solution Approach 1:
A second fluid (buffer or carrier fluid) is introduced as an intermediary substance to displace the sample fluid through the capillary channel. This mediator fluid allows precise volume control by replacing the sample in the channel after a predetermined time, enabling accurate metering without active pumps
Solution Approach 2:
The system pre-fills a reservoir with a second fluid before the sample arrives. This preliminary preparation allows the second fluid to immediately displace the sample through the channel when it reaches a detection point, ensuring precise volume control and timing without requiring active pump intervention
2Quantity of substance
If a large amount of sample is added to the reservoir, then sufficient sample is available for processing, but excess sample is processed when only a minute quantity is needed
Solution Approach 1:
The system extracts only the necessary volume of sample from the reservoir by using a capillary channel with predetermined dimensions and flow characteristics. The channel geometry and flow resistance are designed to limit sample uptake to exactly the required amount, preventing excess sample from being drawn into the processing system
Solution Approach 2:
The second fluid acts as a displacement mediator that pushes the required sample volume through the channel while preventing further sample uptake. By controlling the volume and flow rate of the second fluid, the system precisely limits the amount of sample processed to only what is needed
3Device complexity
If passive capillary-driven systems are used, then device complexity is reduced by eliminating active elements, but control over timing and flow rate is limited
Solution Approach 1:
The system uses dynamic timing control where the capillary channel dimensions, flow resistance, and second fluid properties are selected to achieve predetermined flow rates and timing. This dynamic design allows automated timing control through passive physical principles rather than active mechanical components
Solution Approach 2:
The invention replaces active mechanical pump and valve systems with passive capillary flow control based on pressure gradients and surface tension. Timing is controlled through fluid dynamics principles rather than mechanical timers, maintaining automation while reducing 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 solution ensures accurate metering of a known sample volume with minimal excess, suitable for applications like blood cell counting, without requiring active elements, ensuring reliability and precise volumetric control.
Implementation Method 1
A sample loading system with a metering volume reservoir and a second fluid reservoir, controlled by capillary valves and timing circuitry
Implementation Method 2
a sample reservoir for receiving a sample and a metering volume reservoir, the sample reservoir and a first side of the metering volume reservoir being interconnected through a first channel with a first flow resistance
Data Source
AI summary
Described herein are sample loading systems for loading a sample into a processing and/or analysis system comprising: a sample reservoir for receiving a sample and a metering volume reservoir, the sample reservoir and a first side of the metering volume reservoir being interconnected through a first channel with a first flow resistance to allow filling of the metering volume reservoir with sample; a further reservoir for receiving a second fluid interconnected with the metering volume reservoir at the first side via a second channel having a smaller second flow resistance; a first valve for blocking flow of sample from the metering volume reservoir into the second channel; a second valve connected to a second side of the metering volume reservoir for controlling the blocking and flowing of sample; and a first timing circuitry for timing the opening of the second valve as a function of filling of the further reservoir.