Electrowetting Microfluidic Pump Actuation
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Solution Overview
Problem
Current small, low-power pumps for applications like lab-on-a-chip diagnostics and drug delivery often have moving parts that reduce operational lifetime and expose payload fluids to substances that degrade electrodes or alter the fluid properties, limiting their use in certain applications.
Innovation Solution
A pump design using electrowetting to manipulate a working fluid isolated by an immiscible isolation fluid, which prevents contamination and degradation by translating mechanical energy into a net flow of payload fluid through mechanical valves and diffusers, avoiding direct exposure to degrading substances.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If moving parts (armatures, piezo membranes, valves) are used in pumps, then pumping function is achieved, but operational lifetime is reduced due to repeated flexure and movement
Solution Approach 1:
The patent replaces mechanical moving parts with an electrowetting-based actuation system. Electrical signals are applied to electrodes to manipulate liquid droplets, creating pressure changes that drive fluid flow through the channel without any mechanical moving components. This substitution of mechanical systems with electrical fields directly resolves the contradiction by eliminating wear and fatigue associated with moving parts while maintaining pumping functionality.
Solution Approach 2:
The patent changes the operational parameter from mechanical displacement to electrical field application. By controlling the voltage applied to electrodes, the system modulates the wettability of surfaces to move liquid droplets and generate pressure waves. This parameter change eliminates the need for mechanical movement while achieving the same pumping effect, thereby extending operational lifetime.
2Reliability
If payload fluid is exposed to magnetic nanoparticles, solvents, electrode coatings, or other substances, then pumping action is achieved, but the properties of the payload fluid are limited or altered
Solution Approach 1:
The patent introduces an intermediary liquid droplet system that acts as a mediator between the electrowetting actuation mechanism and the payload fluid. The actuation droplets contain the electrowetting agents and are separated from the payload fluid by channel geometry and flow dynamics. This intermediary system allows the pumping action to be transmitted to the payload fluid without direct contact between the payload fluid and potentially degrading substances like electrode coatings or surfactants.
Solution Approach 2:
The patent segments the fluid system into distinct droplet regions within the microchannel. Different droplets serve different functions: some contain electrowetting agents for actuation, while others carry the payload fluid. This segmentation prevents mixing and direct exposure between incompatible substances, allowing each droplet to maintain its properties while still participating in the overall pumping process.
3Reliability
If electrodes and membranes are used in pumps, then pumping function is achieved, but they are degraded by payload fluid contents (chloride ions, proteins, cells)
Solution Approach 1:
The patent uses liquid droplets as intermediaries that are in contact with electrodes during actuation, while the payload fluid remains separated. The intermediary droplets can be formulated with protective agents and are replaceable, whereas the electrodes and channel structure remain intact. This intermediary layer protects the electrodes from direct exposure to harmful payload fluid contents like proteins and cells, significantly extending electrode durability.
Solution Approach 2:
The patent creates an inert environment for the electrodes by using carefully selected droplet materials and compositions that are chemically compatible with the electrode surfaces. The intermediary droplets form a protective interface that prevents harmful chemical reactions between the payload fluid and electrodes, effectively creating a chemically inert environment around the sensitive electrode surfaces.
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 pump achieves extended operational lifetime and prevents fluid contamination, allowing for the use of surfactants and substances incompatible with payload fluids, while maintaining efficiency and reliability.
Implementation Method 1
A pump is provided that includes first, second, and third electrodes within a second channel... a working fluid... disposed within the second channel between the first and second droplets of isolation fluid... applying, during a first period of time, a voltage between the first electrode and the second electrode; applying, during a second period of time, a voltage between the third electrode and the second electrode
Data Source
AI summary
Microfluidic pumps are provided that use electrowetting to manipulate the location of one or more droplets of a working fluid (e.g., water) in order to pump tears, blood, laboratory samples, carrier fluid, or some other payload fluid. The working fluid is separated from the payload fluid by one or more droplets of an isolating fluid that is immiscible with the working fluid. The working fluid is manipulated via electrowetting, by applying voltages to two or more electrodes, to repeatedly move back and forth. Forces, pressures, and/or fluid flows exerted by the working fluid are coupled to the payload fluid via the droplet(s) of isolation fluid and reed valves, diffuser nozzles, or other varieties of valve can act as flow-rectifying elements to convert the coupled forces into a net flow of the payload fluid through the pump.