Microfluidic Valve Section With Expanding Cross-Section
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Solution Overview
Problem
Microfluidic elements face challenges in reliably controlling liquid flow and venting multiple times, especially with siphon channels, due to issues like soap film formation and residual liquid retention, which hinder efficient biochemical assays.
Innovation Solution
A microfluidic element with a channel structure featuring a valve section that widens in the direction of flow, ensuring a larger liquid transport cross-section at the inlet opening than the preceding channel section, and a chamber with a significantly larger relevant cross-sectional area, preventing uncontrolled liquid entry and allowing reliable venting by external forces.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a siphon channel structure is used for liquid transport, then liquid can be controlled through capillary forces, but residual liquid remains in the channel edges and corners preventing reliable venting
Solution Approach 1:
The channel is divided into a first channel section with constant cross-section and a second channel section with increasing cross-section. This segmentation allows the liquid to be completely emptied in the first section while the second section provides a gradual transition that prevents residual liquid retention, enabling reliable venting for multiple uses.
Solution Approach 2:
The channel cross-section is varied along the flow direction, transitioning from a constant cross-section to an increasing cross-section. This dimensional change in the flow direction allows complete liquid emptying while preventing residual liquid adhesion in edges and corners, solving the venting problem.
2Device complexity
If geometric valves are used for liquid control, then space is saved, but soap film formation prevents reliable venting during multiple uses
Solution Approach 1:
The channel cross-section parameter is changed along the flow direction, increasing from the first to the second channel section. This parameter change prevents soap film formation by eliminating the abrupt cross-section transition that causes surface tension effects, ensuring reliable venting during multiple uses.
3Ease of manufacture
If the channel cross-section remains constant, then manufacturing is simplified, but liquid residues remain at channel ends preventing subsequent filling
Solution Approach 1:
The channel is segmented into two sections: the first with constant cross-section for easy manufacturing, and the second with increasing cross-section to ensure complete liquid emptying. This segmentation maintains manufacturing simplicity while enabling multi-use efficiency by preventing residual liquid retention.
Solution Approach 2:
The channel cross-section is varied in the flow direction, creating a gradual expansion in the second section. This dimensional change ensures complete liquid emptying without significantly complicating manufacturing, thereby improving multi-use efficiency while maintaining ease of fabrication.
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 design ensures complete emptying of the channel, prevents soap film formation, and allows multiple uses without residual liquid, enhancing the reliability and efficiency of liquid handling in multi-stage biochemical analysis processes.
Implementation Method 1
Capillary liquid transport is stopped by the abrupt change in cross-section where the small channel merges into the larger chamber. This transition thus forms a valve.
Implementation Method 2
In particular in the case of washing buffers which comprise detergent-containing solutions, a soapy skin often forms on the valve, so that the valve and the channel are prevented from being vented by the soapy skin.
Data Source
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AI summary
A microfluidic element (1) for analysis of a liquid sample has a substrate (34) and a microfluidic pipe system (2) enclosed by the substrate (34) and a covering layer, which microfluidic pipe system (2) has a channel structure (7). The channel structure (7) comprises a channel (8, 13) having two side walls (22) and a chamber (9, 11) which is in fluid connection with the channel (8, 13). The chamber (9, 11) has a chamber wall (20) having an inlet opening (21). The channel (8, 13) comprises a channel section (18) and a valve section (19) contiguous with the channel section (18), wherein the valve section (19) is in fluid connection with the inlet opening (21) in the chamber wall (20) in such a manner that a liquid can flow from the channel (8, 13) through the valve section (19) into the chamber (9, 11). The valve section (19) has a liquid transport cross section which increases in the direction of flow. The liquid transport cross section in the valve section (19) is greater than the liquid transport cross section in the preceding channel section (18).