Passive Microfluidic Pump Using Capillary Action
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Solution Overview
Problem
Microfluidic devices face limitations in widespread adoption due to the need for bulky and expensive external pumps for precise fluid flow control, which hinders their use in point-of-care diagnostics, food and water testing, and environmental monitoring, especially in low-resource environments.
Innovation Solution
Development of passive, simple, and inexpensive microfluidic pumps that utilize capillary-driven fluid flow through a resistive and absorbent region, allowing for accurate control of fluid flow without energy input, and can be designed as disposable and biodegradable.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If external pumps are used to control fluid flow in microfluidic devices, then fluid flow control precision is improved, but device complexity and cost increase
Solution Approach 1:
The patent replaces mechanical pumps with a passive microfluidic pump that uses capillary action and evaporative cooling to drive fluid flow. The pump comprises a porous medium with temperature-dependent wettability, where heated regions repel fluid and cooler regions attract fluid, creating spontaneous flow without external mechanical components. This substitution eliminates bulky external pumps while maintaining flow control capability.
Solution Approach 2:
The patent utilizes temperature as a control parameter to modulate the wettability of the porous medium. By locally heating or cooling regions of the porous material, the contact angle and capillary pressure change dynamically, enabling precise control of fluid flow rate and direction. This parameter-based control replaces complex mechanical flow control systems.
2Measurement precision
If external pumps are used for fluid flow control, then fluid flow precision is improved, but cost increases
Solution Approach 1:
The patent employs inexpensive porous materials such as paper, fabric, or foam that can be easily manufactured and potentially disposed of after single use. These materials replace costly external pumps and their associated infrastructure, making the system economically viable for point-of-care and resource-limited settings.
Solution Approach 2:
The invention utilizes porous materials with inherent capillary properties to drive fluid flow. The porous structure provides both the pumping mechanism and the flow control functionality, eliminating the need for expensive external pump hardware while maintaining precise flow control through material property selection and geometric design.
3Measurement precision
If external pumps are used, then fluid flow control is improved, but portability and ease of use deteriorate
Solution Approach 1:
The patent extracts the pumping function from external bulky equipment and integrates it directly into the microfluidic device itself. The passive pump is built-in using porous material and thermal management, eliminating the need for external pump hardware and making the device portable and suitable for field deployment.
Solution Approach 2:
The microfluidic pump is self-driven through capillary action and evaporative cooling, requiring no external power source or control system. The system uses the fluid's own evaporation to create the temperature gradient needed for pumping, making it autonomous and extremely portable while maintaining precise flow control.
4Device complexity
If passive pump design is used, then device simplicity is improved, but flow control capability may worsen
Solution Approach 1:
The patent introduces dynamic control to the passive pump system through time-varying thermal fields. By periodically heating and cooling different regions of the porous medium, the system can modulate flow rate, create pulsatile flow patterns, and respond to changing operational requirements, maintaining flow control capability despite the absence of mechanical components.
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
These pumps provide reliable and affordable control of fluid flow, enabling precise fluid handling in microfluidic systems, suitable for a range of applications including point-of-care diagnostics and environmental monitoring, without the need for external power sources.
Implementation Method 1
The resistive region and the absorbent region can be configured to establish a capillary-driven fluid front advancing from the fluid inlet through the resistive region to the absorbent region when the fluid inlet is contacted with fluid
Implementation Method 2
a fluidly non-conducting boundary defining a volume of a second porous medium sized to absorb a predetermined volume of fluid imbibed from the resistive region
Implementation Method 3
an evaporation barrier to minimize evaporation from the resistive region and the absorbent region
Data Source
Figure 1~2
Figure 3~4A
Figure 4B~4C
AI summary
Provided herein are passive microfluidic pumps. The pumps can comprise a fluid inlet, an absorbent region, a resistive region fluidly connecting the fluid inlet and the absorbent region, and an evaporation barrier enclosing the resistive region, the absorbent region, or a combination thereof. The resistive region can comprise a first porous medium, and a fluidly non-conducting boundary defining a path for fluid flow through the first porous medium from the fluid inlet to the absorbent region. The absorbent region can comprise a fluidly non-conducting boundary defining a volume of a second porous medium sized to absorb a predetermined volume of fluid imbibed from the resistive region. The resistive region and the absorbent region can be configured to establish a capillary-driven fluid front advancing from the fluid inlet through the resistive region to the absorbent region when the fluid inlet is contacted with fluid.