Microfluidic Holding Section for Reliable Liquid Combination
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Solution Overview
Problem
Existing microfluidic structures face challenges in reliably combining liquids separated by buffer media, especially for wetting and high surface tension liquids, as they tend to advance or retract into narrower conductions due to capillary forces, leading to inconsistent mixing and impaired functionality.
Innovation Solution
A microfluidic structure with a holding section that has a narrow area with a smaller wall spacing and an adjacent wide area, where the first liquid is transported into the narrow area due to capillary forces and the second liquid is introduced through the same fluid line, allowing the buffer medium to be conveyed past the first liquid, ensuring both liquids combine and exit together under specific volume conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If complex valve circuits and precise monitoring are used to control liquid column positions, then reliable combination of liquids is achieved, but device complexity increases
Solution Approach 1:
The patent replaces complex mechanical valve circuits with a passive geometric structure. The holding section with varying cross-sectional area (narrow area with spacing d1, wide area with spacing d2) uses capillary forces and surface tension to automatically control liquid flow and combination, eliminating the need for active mechanical valve control systems.
Solution Approach 2:
The fluid line structure enables self-regulating liquid combination through its geometric design. The varying wall spacing creates different capillary pressures that automatically draw liquids together in the holding section without external control systems. The system serves itself by using the liquid's own surface tension properties to achieve reliable combination.
2Device complexity
If passive fluid control structures are used to combine liquids, then device complexity is reduced, but reliability for wetting and high surface tension liquids deteriorates
Solution Approach 1:
The patent applies different geometric properties to different sections of the holding section. The narrow area has smaller wall spacing (d1) to retain wetting liquids through strong capillary forces, while the wide area has larger wall spacing (d2) to accommodate liquid combination. This local differentiation of geometric quality ensures reliable handling of wetting and high surface tension liquids.
Solution Approach 2:
The patent changes the geometric parameter of wall spacing from d1 in the narrow area to d2 in the wide area. This parameter change creates different capillary pressure conditions that reliably control liquid behavior for wetting and high surface tension liquids, ensuring consistent mixing without complex control systems.
3Device complexity
If liquid columns are allowed to combine without active control, then device complexity is minimized, but gas buffers separate the liquid columns
Solution Approach 1:
The patent converts the harmful effect of gas buffers into a beneficial control mechanism. The gas buffer's presence creates pressure differences that, combined with the varying capillary forces in the narrow and wide areas, actually help drive the liquid columns together. The geometric design ensures that gas buffers are gradually expelled while liquids combine, turning a potential problem into a functional advantage.
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 configuration ensures reliable combination and conveyance of liquids, reducing the need for complex valve circuits and minimizing production costs while maintaining process reliability across various liquid types.
Implementation Method 1
a first liquid is transported into the narrow area due to capillary forces
Data Source
Figure 1a~1c
Figure 2a~2c
Figure 3a~3c
AI summary
The invention relates to a fluidic structure for controlling one or more fluids. A fluid line (12, 32, 62, 82, 122) has a holding region (20, 40, 70, 90) which extends in the direction of flow (13) in which region the fluid line has a narrow portion (24, 44, 74, 94, 134, 170) and laterally adjacent a wide portion (26, 46, 76, 96, 136, 172), the narrow portion, in at least a first direction perpendicular to the direction of flow, having a smaller wall distance he than the minimum wall distance hw of the wide portion. The invention further relates to a method for combining at least two fluid volumes, a first liquid (140) being conveyed through the fluid line to the narrow or the wide portion of the holding region, then a second liquid (150) which was previously separated from the first fluid by a buffer medium (146) being conveyed to the same portion while the buffer medium is conveyed out from the holding region through the wide or the narrow portion past the first fluid.