Combed Spacer for Side-Loaded EWOD Fluid Control
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Solution Overview
Problem
Conventional side loading designs for EWOD devices face challenges in controlling the input of polar fluids, particularly when using an incomplete oil filling method, leading to unsuccessful fluid loading due to air bubbles and lack of oil at the correct positions within the EWOD channel.
Innovation Solution
An enhanced spacer configuration with combed teeth extending into the EWOD channel defines fluid input ports, ensuring polar fluid contact with nonpolar oil for successful loading, and includes a spacerless region for oil pinning, allowing controlled fluid entry and preventing mixing of different fluids.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If apertures are formed in the upper substrate for fluid input, then fluid loading reliability is improved, but manufacturing complexity and cost increase
Solution Approach 1:
The patent extracts the fluid input function from the upper substrate by removing the need for apertures in the upper substrate. Instead, fluid input is achieved through side loading ports formed only in the lower substrate, eliminating the complexity of forming and aligning apertures in both substrates while maintaining reliable fluid loading through the oil filling method
Solution Approach 2:
The patent segments the fluid input function into separate components: the lower substrate contains the fluid input ports and oil filling mechanism, while the upper substrate remains intact without apertures. This segmentation allows each substrate to be manufactured independently with simpler processes, reducing overall manufacturing complexity while maintaining fluid loading reliability
2Productivity
If more fluid input ports are created in the upper substrate, then fluid entry density is improved, but mechanical strength decreases
Solution Approach 1:
The patent transitions from vertical fluid input through apertures in the upper substrate to horizontal side loading through ports in the lower substrate. This dimensional change allows multiple fluid input ports to be arranged along the edges of the lower substrate without compromising the structural integrity of either substrate, thereby increasing fluid entry density while maintaining mechanical strength
Solution Approach 2:
The patent removes the requirement for upper substrate apertures entirely, extracting the fluid input function to the lower substrate only. This enables the upper substrate to maintain its full mechanical strength while the lower substrate accommodates multiple side loading ports along its edges, achieving high fluid entry density without substrate weakening
3Device complexity
If side loading is used without oil pinning structures, then device simplicity is improved, but fluid loading reliability deteriorates
Solution Approach 1:
The patent implements self-service through the oil filling method where the nonpolar oil automatically pins to the hydrophobic spacer structure without requiring additional active control mechanisms. The oil's natural surface tension and the spacer's hydrophobicity work together to automatically position the oil meniscus at the fluid input ports, ensuring reliable polar fluid loading while maintaining device simplicity
Solution Approach 2:
The patent introduces the nonpolar oil as an intermediary substance that mediates between the polar fluid input and the EWOD channel. The oil forms a meniscus at the hydrophobic spacer structure, creating a controlled interface that guides polar fluid entry into the channel while maintaining simple device architecture without complex active control mechanisms
4Productivity
If incomplete oil filling is used, then productivity is improved, but fluid loading reliability worsens due to air bubbles
Solution Approach 1:
The patent applies local quality by creating hydrophobic regions specifically at the fluid input ports through the spacer structure. This localized hydrophobicity ensures that the nonpolar oil pins preferentially at these locations, creating reliable oil menisci that guide polar fluid entry even when the channel is incompletely filled, thereby maintaining fluid loading reliability while enabling fast productivity through incomplete filling
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 enhanced spacer configuration ensures reliable and controlled side loading of polar fluids into the EWOD channel, reducing the need for apertures in the upper substrate, thereby reducing manufacturing costs and increasing the density of fluid entry points while maintaining precision and mechanical strength.
Implementation Method 1
A suitable gap or channel between the two substrates may be realized by means of a spacer 18, and a nonpolar surround fluid 20 (e.g. oil) may be used to occupy the volume not occupied by the liquid droplet 14. The function of the oil is to reduce the surface tension at the surfaces of the polar droplets, and to increase the electro-wetting force
Implementation Method 2
The function of the oil is to reduce the surface tension at the surfaces of the polar droplets, and to increase the electro-wetting force
Implementation Method 3
the teeth isolate adjacent fluid input ports from each other
Implementation Method 4
includes a spacerless region for oil pinning, allowing controlled fluid entry and preventing mixing of different fluids
Data Source
AI summary
An EWOD device includes a first and second substrate assemblies, and a spacer that spaces apart the first substrate assembly from the second substrate assembly to define a channel between them. The spacer defines fluid input ports that are in fluid communication with the channel, and the spacer is configured for directing fluid from the fluid input ports into the channel. The spacer has a combed spacer configuration to define the fluid input ports, including alternating teeth that extend into the channel from a base region, and the teeth isolate adjacent fluid input ports from each other. The spacer may contact only a portion of the first and second substrate assemblies to form a spacerless region within the EWOD device, and the spacer includes regions that are in contact with both the first and second substrate assemblies and extend into the channel to define a cell-gap of the channel.