Microfluidic Hub Substrate Spacing and Droplet Actuation
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Solution Overview
Problem
Existing digital microfluidic devices face challenges in reliably fixturing substrates close together to maintain a consistent gap for droplet movement and in making robust electrical connections, as well as in delivering and removing fluids from the interstitial space between substrates, leading to issues with droplet actuation and contamination.
Innovation Solution
The use of microfluidic hubs and fixtures that set a predetermined distance between substrates, allowing for precise positioning and actuation of droplets using digital microfluidic technology, and providing mechanisms for electrical and fluidic connections without the need for physical channels, such as capillaries and ferrules, to facilitate droplet manipulation and interface disparate fluidic systems.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If substrates are fixed close together to maintain consistent gap for droplet movement, then droplet actuation reliability is improved, but device complexity increases due to fixture requirements
Solution Approach 1:
The device is divided into two separate substrates (first substrate with actuated electrode, second substrate with ground plane electrode) that can be independently fabricated and then assembled together with a controlled gap, eliminating the need for complex single-substrate fixtures
Solution Approach 2:
A dielectric layer is introduced as an intermediary between the actuated electrode on the first substrate and the droplet, enabling electrical actuation while maintaining a consistent physical gap without requiring complex mechanical fixtures
2Ease of operation
If physical channels such as capillaries and ferrules are used for fluid delivery, then fluidic connections are established, but contamination risks increase
Solution Approach 1:
The invention extracts and eliminates the need for physical fluidic channels (capillaries, ferrules) by using digital microfluidic droplet manipulation to transport fluids directly between locations on the substrate surface, thereby removing the contamination risk associated with physical channels
Solution Approach 2:
Physical mechanical fluid delivery systems (capillaries and ferrules) are replaced with an electrical field-based droplet manipulation system that moves fluids through electrowetting and body forces without requiring physical contact channels
3Ease of operation
If open format devices with continuous ground electrodes are used, then droplet movement is enabled, but manufacturing precision is reduced due to electrode patterning constraints
Solution Approach 1:
The continuous ground electrode is segmented and relocated to the second substrate, allowing the first substrate to focus on precise actuated electrode patterning while the ground plane is independently fabricated on the second substrate with less stringent precision requirements
Solution Approach 2:
The ground electrode is moved from the same plane as the actuated electrode to a separate second substrate, creating a three-dimensional electrode configuration that relaxes the patterning precision constraints on the first substrate
4Manufacturing precision
If closed format devices with spacers are used to maintain gap, then substrate positioning is improved, but device complexity increases due to spacer integration
Solution Approach 1:
The gap-maintaining function previously requiring separate spacer components is merged into the dielectric layer that is already part of the electrode structure, eliminating the need for additional spacer integration steps
Solution Approach 2:
The dielectric layer serves multiple functions: it provides electrical insulation between the actuated electrode and droplet, maintains the consistent gap distance, and enables the closed-format substrate configuration, eliminating the need for separate spacer 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
This approach enables reliable and repeatable droplet actuation, reduces contamination risks, and improves the integration of microfluidic systems by allowing for precise control over droplet movement and fluid handling within the microfluidic hubs, enhancing the reliability and versatility of digital microfluidic devices.
Implementation Method 1
By applying an electric field in an area adjacent a droplet, interfacial (e.g. electrowetting) and body forces are generated, which may attract the droplet into the region of higher field intensity, thus moving the droplet.
Implementation Method 2
A voltage may be applied, for example to another electrode 110, which may alter the contact angle between the droplet and substrate 115 and/or produce a localized electric field gradient, resulting in motion of the droplet 125
Data Source
AI summary
Embodiments of microfluidic hubs and systems are described that may be used to connect fluidic modules. A space between surfaces may be set by fixtures described herein. In some examples a fixture may set substrate-to-substrate spacing based on a distance between registration surfaces on which the respective substrates rest. Fluidic interfaces are described, including examples where fluid conduits (e.g. capillaries) extend into the fixture to the space between surfaces. Droplets of fluid may be introduced to and/or removed from microfluidic hubs described herein, and fluid actuators may be used to move droplets within the space between surfaces. Continuous flow modules may be integrated with the hubs in some examples.