Microfluidic Structure for Bubble-Free Liquid Combining
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Solution Overview
Problem
Existing microfluidic systems face challenges in bubble-free combining of liquid volumes due to insufficient capillary pressure, requiring alternative methods for reliable liquid delivery and prevention of air bubbles in the combined liquid.
Innovation Solution
A microfluidic structure with a fluid chamber that broadens in cross section from the inlet to the outlet channel, allowing a pressure-driven first liquid to expand and encompass a second liquid, which is held in place by surface contact structures, ensuring bubble-free combination and efficient liquid delivery through the outlet channel.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If capillary forces are used to drive liquid flow in microfluidic channels, then liquid delivery can be passive and simple, but the cross-sectional dimensions must be very small (10-2000 μm) which limits the volume of liquid that can be combined
Solution Approach 1:
The microfluidic system is divided into multiple functional modules: a first module with capillary-driven channels for small volume liquid delivery, and a second module with a fluid chamber for larger volume combining. This segmentation allows each module to optimize for its specific function while working together to achieve both passive operation and larger combined volumes.
Solution Approach 2:
The patent implements a nested structure where a microfluidic chip with capillary channels is integrated into a larger fluid handling system. The chip's channels are nested within a fluid chamber that can hold larger volumes, allowing the small-scale capillary structures to be contained within a larger volume-capable system.
2Quantity of substance
If the cross section of fluid channels is increased to handle larger liquid volumes, then more liquid can be combined, but capillary pressure becomes insufficient for reliable liquid delivery
Solution Approach 1:
The system separates the functions of liquid delivery and liquid combining into different modules. The first module uses narrow capillary channels (10-2000 μm) to generate sufficient capillary pressure for reliable delivery, while the second module provides a larger fluid chamber for volume combining, thus resolving the conflict between channel size and available capillary pressure.
Solution Approach 2:
Different regions of the microfluidic system have different cross-sectional dimensions optimized for their specific functions. The inlet channels and capillary structures have small dimensions (10-2000 μm) to generate high capillary pressure, while the fluid chamber has a larger cross section to accommodate larger liquid volumes for combining.
3Productivity
If liquid volumes are combined in a Y-shaped structure with acute angle inlet lines, then two liquids can be merged, but air bubbles are easily included and the process is not bubble-free
Solution Approach 1:
The patent replaces the sharp Y-shaped acute angle structure with a fluid chamber that has curved, rounded geometry. This spherical/curved design allows liquids to merge more smoothly and prevents air bubbles from becoming trapped in sharp corners, thereby achieving bubble-free operation while maintaining combining efficiency.
Solution Approach 2:
The patent acknowledges that Y-shaped structures inherently trap air bubbles in their acute angles, but converts this harmful effect into a beneficial design choice by explicitly avoiding such geometry. Instead, the fluid chamber is designed with curved surfaces that naturally guide both liquids and air away from trapping zones, turning the potential harm of bubble formation into a design criterion for bubble-free operation.
4Ease of operation
If inlet lines are narrowed at discharge points to control liquid flow by capillary forces, then liquid can be halted before entering the channel, but pressure pulses are required to trigger liquid movement which complicates operation
Solution Approach 1:
The patent extracts the pressure control mechanism from the microfluidic chip itself and places it in the external operator device. The chip contains only passive capillary channels and fluid chambers that rely on capillary forces for flow control, while pressure pulses are applied externally through the operator device's syringe pump, simplifying the chip design and making operation more intuitive.
Solution Approach 2:
The patent introduces an operator device as an intermediary between the user and the microfluidic chip. This intermediary handles the complex pressure pulse generation and delivery, allowing the chip itself to remain simple and passive, relying only on capillary forces for flow control while the operator device manages the pressure actuation.
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
The solution enables secure, error-prone, and economical bubble-free combining of liquid volumes, preventing air inclusion and ensuring reliable operation by utilizing pressure-driven flow and wettable surfaces for efficient liquid handling.
Implementation Method 1
a first liquid volume, which is essentially pressure-driven and conducted through the inlet channel (3) and through the fluid chamber (2)
Implementation Method 2
is designed, thanks to the broadened cross section, to broaden a first liquid volume (41) which is essentially pressure-driven
Implementation Method 3
a second liquid volume (42), placed in the fluid chamber (2) through the feed opening (5), can be held in the region of the holding position (6)
Implementation Method 4
the second liquid volume (42) when the first liquid volume (41) is moved through by pressure is taken up by the latter and delivered as a combined liquid volume
Data Source
AI summary
Pressure-operable microfluidic structure for the bubble-free combining of two liquid volumes with a fluid chamber that has a feed opening, as well as an inlet and outlet channel emerging into the fluid chamber, wherein the fluid chamber has a cross section that broadens out relative to the inlet channel in the direction of flow from the inlet to the outlet channel and is designed, thanks to the broadened cross section, to broaden a first liquid volume that is essentially pressure-driven and conducted through the inlet channel and through the fluid chamber to a cross section at least approximately corresponding to the full cross section of the fluid chamber, while the fluid chamber has a holding position and is configured so that a second liquid volume, placed in the fluid chamber through the feed opening, can be held in the region of the holding position and the second liquid volume when the first liquid volume is moved through by pressure can be taken up by the latter and delivered as a combined liquid volume through the fluid chamber and into the outlet channel.