Microfluidic Evaporation Compensation via Capillary Pressure Differential
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Solution Overview
Problem
Microfluidic systems face issues with liquid evaporation, leading to air intrusion, flow termination, and reduced sample volume, which affects the accuracy of analytical results, especially in biological samples like blood, due to the rapid evaporation of liquids in miniaturized systems.
Innovation Solution
A microfluidic system with a compensating channel that exerts a retention capillary pressure to refill liquid in outlet channels, preventing evaporation and air intrusion by flowing liquid from the compensating channel to the sample manipulation portion when evaporation occurs, thus maintaining continuous capillary flow without the need for pumps or user intervention.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If microfluidic channels are used for sample analysis, then rapid analysis response and portability are achieved, but liquid evaporation occurs quickly leading to air intrusion and flow termination
Solution Approach 1:
The compensating channel is pre-filled with liquid and positioned to provide liquid before evaporation causes problems. The channel geometry and liquid volume are designed in advance to compensate for expected evaporation losses during the analysis period, ensuring continuous flow without air intrusion.
Solution Approach 2:
The compensating channel acts as an intermediary liquid reservoir between the liquid supply and the evaporation-prone outlet channels. It provides a buffer supply of liquid that compensates for evaporation losses, mediating between the main liquid source and the vulnerable capillary channels.
2Reliability
If sample liquid is isolated from ambient air to prevent evaporation, then evaporation problems are reduced, but the system becomes difficult to control and not viable for point-of-care devices
Solution Approach 1:
The system uses passive capillary forces for automatic liquid compensation without requiring external control mechanisms. The compensating channel self-regulates liquid flow based on evaporation rates, eliminating the need for pumps, valves, or user intervention while maintaining ease of operation for point-of-care applications.
Solution Approach 2:
The patent replaces active mechanical control systems (pumps, valves) with passive capillary forces. The capillary pressure differential automatically drives liquid from the compensating channel to offset evaporation, providing a simple, controllable solution suitable for portable devices.
3Quantity of substance
If liquid evaporates from outlet channels, then sample volume is reduced, but this leads to decreased accuracy of analytical results
Solution Approach 1:
The compensating channel is designed with sufficient liquid volume and appropriate capillary dimensions to preemptively compensate for evaporation losses before they affect the sample volume in the analysis channels. This ensures that the sample volume remains constant throughout the analysis process, maintaining measurement precision.
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 effectively compensates for evaporation in microfluidic systems, preventing air intrusion and maintaining accurate analytical results by passively replenishing liquid in the system, ensuring consistent capillary flow and sample volume, even under varying conditions.
Implementation Method 1
the compensating microfluidic channel is arranged to exert a retention capillary pressure on the liquid
Implementation Method 2
each outlet channel of the plurality of outlet channels is arranged to exert a retention capillary pressure on the liquid
Implementation Method 3
such that the liquid flows from the compensating microfluidic channel towards the sample manipulation portion if liquid evaporates from one or more of the plurality of outlet channels
Data Source
AI summary
The present inventive concept relates to a microfluidic system for compensation of evaporation of liquid from channels. The microfluidic system comprises: a compensating microfluidic channel having a first end arranged for hindering capillary driven flow of a liquid out from the compensation microfluidic channel via the first end, and, a second end, being connected to a first microfluidic channel: a sample manipulation portion comprising a plurality of outlet channels, wherein each outlet channel ends in a respective stop valve, wherein the first microfluidic channel connects to the sample manipulation portion, thereby being in fluidic connection with the plurality of outlet channels, wherein each outlet channel of the plurality of outlet channels is arranged to exert a retention capillary pressure on the liquid, wherein the compensating microfluidic channel is arranged to exert a retention capillary pressure on the liquid, wherein the retention capillary pressure of each outlet channel is larger than the retention capillary pressure of the compensating microfluidic channel, such that the liquid flows from the compensating microfluidic channel towards the sample manipulation portion if liquid evaporates from one or more of the plurality of outlet channels at the respective stop valve, thereby compensating for evaporation of the liquid from the plurality of outlet channels at the respective stop valve.