Microfluidic AM-EWOD Device Fluid Loading Method
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Solution Overview
Problem
Existing microfluidic devices face challenges in efficiently loading and controlling the volume of assay fluids due to the hydrophobic nature of their internal surfaces, which makes it energetically unfavorable for aqueous fluids to fill by capillary action, and lack effective methods for introducing discrete droplets and measuring input volumes.
Innovation Solution
A method and device configuration that involves introducing a metered volume of a filler fluid into the chamber, allowing it to partially fill, and then using capillary action and electro-wetting forces to introduce assay fluid while venting out filler fluid, with optional electro-wetting control for precise positioning and volume management.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the internal surfaces of the microfluidic device are made hydrophobic to enable droplet manipulation, then droplet control is improved, but capillary filling of aqueous fluids becomes energetically unfavorable
Solution Approach 1:
The patent introduces an intermediary substance (filler fluid, typically oil) that mediates between the hydrophobic surface and the aqueous assay fluid. The filler fluid fills the chamber first, creating a compatible interface that allows subsequent aqueous fluid introduction without direct contact with hydrophobic surfaces, thus resolving the contradiction between hydrophobic droplet manipulation and capillary filling
2Productivity
If external pumps or pressure systems are used to force fluid into the device, then fluid loading speed is improved, but device complexity and risk of leakage increase
Solution Approach 1:
The patent enables the system to load fluids without external pumping by utilizing the inherent properties of the filler fluid and assay fluid combination. The assay fluid automatically enters the chamber through inlet ports driven by interfacial tension and surface energy differences between the oils and aqueous fluid, eliminating the need for external pumps and pressure systems
3Manufacturing precision
If the chamber is completely filled with filler fluid to enable electro-wetting control, then droplet positioning precision is improved, but volume management becomes difficult
Solution Approach 1:
The patent creates a dynamic system where the filler fluid level can be adjusted and controlled during operation. By controlling the amount of filler fluid introduced and using electro-wetting to manipulate the interface, the system achieves both precise droplet positioning and flexible volume management, allowing the chamber to transition between different filling states as needed
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
Enables efficient, accurate, and controlled loading of assay fluids without the need for external pumps or pressure, reducing the risk of leakage and allowing for precise volume management, thus improving the reliability and simplicity of microfluidic operations.
Implementation Method 1
it is energetically unfavourable for aqueous fluids to fill into such a device from outside by capillary action alone
Implementation Method 2
Electro-wetting-On-Dielectric (EWOD) is a known technique for manipulating droplets of fluid on an array
Data Source
AI summary
A microfluidic AM-EWOD device and a method of filling such a device are provided. The device comprises a chamber having one or more inlet ports. The device is configured, when the chamber contains a metered volume of a filler fluid that partially fills the chamber, preferentially maintain the metered volume of the filler fluid in a part of the chamber. The device is configured to allow displacement of some of the filler fluid from the part of the chamber when a volume of an assay fluid introduced into one of the one or more inlet ports enters the part of the chamber, thereby causing a volume of a venting fluid to vent from the chamber.