Disposable Microfluidics Cartridge Using Electrowetting and Suction
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Solution Overview
Problem
Existing digital microfluidics systems require larger volumes of liquids and are not portable, limiting their application in manipulating small volumes of biological samples efficiently.
Innovation Solution
A disposable cartridge with a flexible hydrophobic bottom layer and a rigid cover plate, sealed by a gasket, which is attracted to an electrode array by underpressure, allowing for efficient manipulation of liquid droplets using electrowetting without the need for spacers, enabling portable and efficient processing of small sample volumes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If digital microfluidics systems are designed to process small volumes of liquid, then sample volume is reduced, but system portability and automation are compromised
Solution Approach 1:
The system is divided into a permanent base unit containing the electrode array and a disposable cartridge containing the hydrophobic film. This segmentation allows the base unit to remain stationary and automated while the cartridge can be easily replaced, enabling portability without sacrificing automation capability.
Solution Approach 2:
The invention uses a disposable cartridge with a hydrophobic film that is discarded after a single use. This eliminates the need for cleaning and maintenance of the microfluidic channels, enabling the system to be simpler and more portable while maintaining automated processing capability for small liquid volumes.
2Device complexity
If a disposable cartridge is designed without spacers, then device complexity is reduced, but gap definition between hydrophobic surfaces becomes difficult
Solution Approach 1:
The invention replaces the traditional mechanical spacer system with an electrostatic field-based gap definition. The gap between the hydrophobic film and the electrode array is defined by the balance between electrostatic attraction forces (when voltage is applied) and surface tension forces of the liquid, eliminating the need for physical spacers and reducing device complexity.
Solution Approach 2:
The gap definition is achieved by changing the electrical parameter (applying voltage) rather than using a fixed mechanical structure. When voltage is applied to the electrode array, the electrostatic attraction pulls the hydrophobic film closer to the electrode array, dynamically defining the gap size based on the applied voltage and liquid properties.
3Productivity
If automated liquid handling is implemented, then processing efficiency is improved, but system size and portability are compromised
Solution Approach 1:
The disposable cartridge is designed to be pre-filled with reagents and samples, and the microfluidic channels are designed to allow automatic liquid handling through capillary action and electrostatic control. This self-service design enables automated processing without requiring large, complex liquid handling robots, improving portability while maintaining processing efficiency.
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 allows for precise manipulation of liquid droplets in a portable format, reducing the need for larger volumes of liquids and enabling efficient processing of biological samples, while maintaining cleanliness and ease of disposal.
Implementation Method 1
By applying a defined voltage to electrodes of the electrode array, a change of the surface tension of the liquid droplet, which is present on the addressed electrodes, is induced. This results in a remarkable change of the contact angle of the droplet on the addressed electrode, hence in a movement of the droplet.
Implementation Method 2
The flexible bottom layer is configured to be laid on an uppermost surface of a cartridge accommodation site of the digital microfluidics system and to be attracted to and spread over the uppermost surface by the underpressure in an evacuation space
Data Source
Figure 1~3
Figure 4~6B
Figure 7~9
AI summary
A disposable cartridge (2) for use in a digital microfluidics system (1) comprises a bottom layer (3) with a first hydrophobic surface (17'), a rigid cover plate (12) with a second hydrophobic surface (17"), and a gap (6) there-between. The bottom layer (3) is a flexible film laid onto an uppermost surface (52) of a cartridge accommodation site (8) of a digital microfluidics system (1), attracted to and spread over the uppermost surface (52) by an underpressure in an evacuation space (46). The disposable cartridge (2) may be assembled at a cartridge accommodation site (8), a lower surface (48') of the rigid cover plate (12) and the flexible bottom layer (3) then are sealingly attached to each other by mutual contacting. The assembled disposable cartridge (2) is removed from the cartridge accommodation site (8) in one piece that comprises the bottom layer (3), the plane rigid cover plate (12), and the gap (6) that potentially comprises samples and processing fluids. The digital microfluidics system (1) comprises a base unit (7) and a cartridge accommodation site (8) with an electrode array (9) that comprises a number of individual electrodes (10). The digital microfluidics system (1) comprises a central control unit (14) for controlling the selection of the individual electrodes (10) and for providing these electrodes (10) with individual voltage pulses for manipulating liquid droplets within the gap (6) of the cartridge (2) by electrowetting.