Microfluidic Liquid Lens via Electrowetting and Wetting Defects
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Solution Overview
Problem
Current methods for manufacturing liquid lenses with variable focal length lack a microfluidic approach, relying on macroscopic techniques or deformation of solid or liquid membranes, and there is no established method for producing two-phase liquid/liquid or gas systems in microfluidics.
Innovation Solution
A microfluidic device using electrowetting on dielectric (EWOD) to create inclusions of a first liquid within a drop of a second immiscible liquid, allowing for the production of liquid lenses with variable focal length by controlling the size and shape of the inclusion through electrode activation and wetting defects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If macroscopic techniques or deformation of solid/liquid membranes are used to manufacture liquid lenses, then liquid lenses with variable focal length can be produced, but the device cannot be miniaturized and integrated into microfluidic systems
Solution Approach 1:
The patent replaces macroscopic mechanical deformation methods with microfluidic electrowetting-on-dielectric (EWOD) technology. Instead of deforming solid or liquid membranes mechanically, the invention uses electrical fields to control the shape and volume of liquid inclusions within a droplet, enabling miniaturization while maintaining variable focal length capability through electrical actuation rather than mechanical manipulation
Solution Approach 2:
The invention employs liquid-liquid or gas-liquid two-phase systems within microfluidic channels. By controlling the volume and pressure of the internal liquid or gas phase through microfluidic actuation, the focal length of the liquid lens is varied. This hydraulic approach enables precise control of lens parameters at the microscale, replacing macroscopic mechanical deformation with fluid pressure control
2Ease of manufacture
If direct injection of oil into water is used, then liquid lenses can be produced, but there is no microfluidic method to manufacture this type of inclusion
Solution Approach 1:
The patent introduces a hydrophobic barrier layer as an intermediary between the oil and water phases. This barrier enables controlled formation of oil inclusions within water droplets in a microfluidic setting. The hydrophobic layer acts as a template that guides the phase separation and inclusion formation process, making microfluidic manufacturing of two-phase systems feasible while maintaining precise control over inclusion size and position
Solution Approach 2:
The invention creates local variations in wettability by introducing hydrophobic regions at specific locations within the microfluidic device. These localized hydrophobic zones control where and how the oil phase separates from the water phase, enabling precise formation of inclusions at predetermined positions. This local quality approach allows controlled inclusion manufacturing that would not be possible with uniform direct injection methods
3Adaptability or versatility
If electrowetting on dielectric is used to control liquid lens shape, then variable focal length is achieved, but the method requires precise control of wetting defects and electrode activation
Solution Approach 1:
The patent pre-forms hydrophobic defects or patterns in the dielectric layer during device fabrication. These pre-created wetting defects serve as predetermined sites where liquid inclusions will form and where electrowetting control will be most effective. By preparing the surface topology and wettability characteristics in advance, the device reduces the complexity of real-time control, as the electrowetting actuation only needs to modulate the shape of inclusions that are already positioned at the correct locations
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 the reproducible and controlled manufacture of liquid lenses with variable focal length, suitable for miniaturization and large-scale production, with adjustable parameters for precise inclusion volume and shape, facilitating integration into microfluidic optical systems.
Implementation Method 1
A microfluidic device using electrowetting on dielectric (EWOD) to create inclusions of a first liquid within a drop of a second immiscible liquid
Implementation Method 2
controlling the size and shape of the inclusion through electrode activation and wetting defects
Data Source
Figure 1A~2
Figure 3A~4
Figure 5~6
AI summary
The invention concerns a microfluidic device of a two-phase liquid/liquid or gas system using a first liquid or a gas and a second liquid non mutually miscible, said device having a first hydrophobic surface for the second liquid, the first liquid forming a film (6) on said first hydrophobic surface. The device comprises means for introducing a drop (7) of the second liquid into the first liquid or gas film and contacting said first hydrophobic surface, and means for moving the drop on said first hydrophobic surface along a specific path, the device having, on the path of the drop, at least one wetting defect causing, upon the passage of the drop on said defect, a break of the triple contact line of the drop on the first hydrophobic surface and the inclusion of the first liquid (8) or gas in the drop. The invention also concerns the related method.