Discretisation Structure for Rapid Microfluidic Mixing
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Solution Overview
Problem
Microfluidic devices face challenges in mixing and diluting liquids due to laminar flow and the need for rapid mixing in point-of-care applications, where existing methods rely on diffusion and chaotic advection, which are inefficient for achieving quick and effective mixing.
Innovation Solution
A device with a discretisation structure that creates discrete, temporally separated liquid volumes by controlling inflow and outflow rates, using a siphon-like mechanism or surface tension energy barriers to ensure periodic emptying and refilling, enhancing mixing by intermingling liquids in a mixing chamber.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If diffusion and chaotic advection are used for mixing in microfluidic systems, then mixing can be achieved without external means, but mixing speed is slow and efficiency is low
Solution Approach 1:
The patent employs periodic action by creating discrete, temporally separated liquid volumes that are dispensed in a sequence. This periodic dispensing creates repeated cycles of liquid introduction and mixing events, which significantly accelerates mixing compared to continuous diffusion-based approaches. The discretisation structure periodically fills and empties to generate this rhythmic flow pattern that enhances mixing efficiency.
Solution Approach 2:
The patent applies segmentation by dividing the continuous liquid flow into discrete, temporally separated volumes. The discretisation structure creates individual liquid packets that are dispensed one after another, rather than as a continuous stream. This segmentation increases the contact surface area between different liquids and reduces diffusion lengths, thereby improving mixing speed and efficiency.
2Productivity
If continuous flow is used in microfluidic devices, then liquid transport is simple, but mixing efficiency is poor due to laminar flow
Solution Approach 1:
The patent transforms continuous flow into periodic flow by using a discretisation structure that fills and empties in cycles. This periodic action creates discrete liquid volumes that are dispensed at regular intervals, generating repeated mixing events that dramatically improve mixing efficiency while maintaining relatively simple flow control through passive structural design.
Solution Approach 2:
The patent segments the continuous liquid flow into discrete volumes using the discretisation structure. By creating individual liquid packets separated in time and space, the system enhances intermingling between different liquids. This segmentation approach improves mixing efficiency without requiring complex active flow control mechanisms.
3Productivity
If discrete liquid volumes are created to enhance mixing, then contact surface area increases and diffusion length decreases, but flow control becomes more complex
Solution Approach 1:
The discretisation structure operates on a self-service principle where the liquid flow itself drives the filling and emptying cycles. The structure passively responds to the incoming liquid flow, automatically creating discrete volumes without requiring external actuators or complex control systems. The geometry of the structure and the flow rate naturally regulate the discretisation process.
Solution Approach 2:
The patent extracts the mixing enhancement function from complex active control systems and embeds it in a passive discretisation structure. By taking out the need for external mixing mechanisms (such as pumps, valves, or chaotic advection elements) and replacing them with a simple geometric structure that naturally creates discrete flows, the system achieves efficient mixing with minimal device complexity.
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 approach enables rapid mixing within seconds by increasing contact surface area and reducing diffusion lengths, allowing for precise control of mixing ratios and efficient dilution, particularly suitable for point-of-care applications.
Implementation Method 1
To achieve a siphon action emptying of the discretisation structure once the liquid level exceeds a threshold level
Implementation Method 2
the outlet is arranged to provide a surface tension energy barrier to flow of the liquid, thereby retaining liquid in the discretisation structure until the liquid reaches the level
Implementation Method 3
the liquid head acting on the outlet under the influence of the driving force is sufficiently large to overcome the surface tension barrier, so that liquid will flow until the corresponding liquid column breaks
Data Source
Figure 1a~1b
Figure 1c~1d
Figure 2a~2b
AI summary
Devices for generating discrete flow of liquids in response to a driving force are disclosed, for example centrifugal microfluidic devices for generating discrete flow in response to a constant driving force. The devices find applications in liquid mixing, for example for diluting samples, such as blood plasma samples.