Microfluidic Sampling Valve for Fresh Sample Isolation
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Solution Overview
Problem
Existing liquid sampling devices often fail to ensure that only fresh body fluid samples are tested, as initial portions of the sample can be unsuitable for analysis and may contaminate the measuring chamber, and there is a need for efficient control over fluid flow without moving parts or external power.
Innovation Solution
A microfluidic liquid sampling device with a support structure featuring a liquid reception interface, capillary fluid passageway, reservoir chamber, and passive microfluidic valve that allows fluid to flow into the measuring chamber only when the reservoir is completely filled, using static pressure differences and capillary action to control fluid transport, and an air bubble is injected to stop further flow once the measuring chamber is full.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If a liquid sampling device collects body fluid through a reception interface, then the sample volume is sufficient for testing, but the initial portion of the sample may contaminate the measuring chamber and affect test accuracy
Solution Approach 1:
The device divides the fluid path into distinct segments: a reservoir chamber that receives and holds the initial sample portion, and a measuring chamber that receives only the fresh sample portion. The microfluidic valve creates a clear separation between these segments, ensuring that the initial sample that may contain contaminants remains in the reservoir chamber while only the fresh sample flows to the measuring chamber for analysis.
2Device complexity
If a passive microfluidic valve without moving parts is used to control fluid flow, then the device complexity is reduced and reliability is improved, but the control of fluid flow becomes dependent on static pressure differences
Solution Approach 1:
The passive microfluidic valve operates autonomously based on static pressure differences that naturally occur during fluid flow. The valve structure includes a valve chamber and valve seat that automatically open or close based on the pressure differential across the valve, without requiring external actuation mechanisms. This self-regulating behavior simplifies the device structure while maintaining reliable fluid flow control.
3Reliability
If the reservoir chamber is configured to prevent static pressure from exceeding the threshold, then the microfluidic valve remains closed and prevents premature flow, but the hydrostatic pressure from capillary forces is absorbed by the reservoir chamber
Solution Approach 1:
The reservoir chamber acts as an intermediary element between the fluid reception interface and the microfluidic valve. It absorbs the hydrostatic pressure generated by capillary forces in the fluid passageway, preventing this pressure from directly acting on the microfluidic valve. This intermediary role allows the valve to remain reliably closed until the reservoir chamber is completely filled, at which point the pressure differential triggers valve opening.
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
Ensures that only fresh body fluid samples are fed to the testing chamber, preventing initial sample contamination and providing reliable, reproducible sampling without the need for moving parts or external power, ensuring accurate analyte detection.
Implementation Method 1
a capillary fluid passageway leading to a reservoir chamber
Implementation Method 2
Passing of liquid through the microfluidic valve is controlled by the static pressure difference (pressure drop, ΔP) over the microfluidic valve
Implementation Method 3
the hydrostatic pressure that is inter alia caused by capillary forces in the fluid passageway between the liquid reception interface and the entrance of the reservoir chamber
Data Source
AI summary
The invention relates to a liquid sampling device a support structure having a liquid reception interface that is in fluid communication with a reservoir chamber and a microfluidic valve, the microfluidic valve being connected to a measuring chamber. The liquid reception interface, the reservoir chamber and the microfluidic valve are configured to allow liquid entering the liquid reception interface to flow into the reservoir chamber while being prevented from passing the microfluidic valve unless a predetermined static pressure difference over the microfluidic valve is exceeded. The microfluidic valve is a passive valve without moving parts. Passing of liquid through the microfluidic valve is controlled by a static pressure difference over the microfluidic valve. The reservoir chamber is configured and arranged to cause high enough a static pressure at an entrance side of the microfluidic valve that causes a flow of liquid through the microfluidic valve into the measuring chamber once the reservoir chamber is completely filled.