Bridging Membrane for Electroosmotic Fluid Focusing
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Solution Overview
Problem
Existing microchip devices face challenges in transporting chemical and biological materials without generating electrochemically produced gases, which can disrupt fluid flow and hinder electrokinetic transport due to the inability to make direct electrical contacts within microchannels without producing electrolysis products like oxygen and hydrogen gas.
Innovation Solution
A microfabricated device with a bridging membrane that allows ionic electric current and gas transport while inhibiting bulk fluid flow, enabling electrokinetic manipulation of materials in an electric field-free region, thereby minimizing electrochemically generated products and facilitating the transport of fluidic materials.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If direct electrical contacts are made within microchannels, then electrokinetic transport can be enabled, but electrolysis products are generated that separate the fluid and hinder transport
Solution Approach 1:
The microchannel is divided into distinct regions: an electrokinetic transport region with electrical contacts and an analysis region without electrical contacts. This segmentation allows electrokinetic transport to occur in one region while preventing electrolysis product interference in the analysis region, resolving the contradiction between enabling transport and avoiding harmful effects.
Solution Approach 2:
The harmful electrolysis process is extracted and isolated to a specific region away from the analysis zone. By separating the electrical contact region from the analysis region, the harmful electrolysis products are confined to one area while the analysis region remains free from such interference, maintaining both transport capability and analysis integrity.
2Speed
If electric fields are applied throughout the microchannel, then fluid transport is achieved, but interference with detection and analysis occurs
Solution Approach 1:
The microchannel is segmented into an electrokinetic pumping region where electric fields enable rapid fluid transport and an analysis region where the absence of electric fields allows undisturbed detection and measurement. This spatial segmentation resolves the contradiction between achieving fast transport and enabling accurate detection.
Solution Approach 2:
A bridging membrane serves as an intermediary structure that allows pressure-driven flow from the electrokinetic region to continue into the analysis region without requiring electric fields in the detection zone. This mediator enables the transition from field-driven transport to field-free analysis, resolving the detection interference issue.
3Ease of operation
If external pumping apparatus is used, then fluid control is achieved, but device complexity and hardware requirements increase
Solution Approach 1:
The microdevice uses self-contained electrokinetic pumping mechanisms integrated directly into the microchannel structure, eliminating the need for external pumping apparatus. The system serves itself by using embedded electrodes to generate the necessary fluid flow, thereby maintaining ease of operation while reducing device complexity and hardware requirements.
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 device effectively confines and transports fluidic streams in an electric field-free region, reducing electrochemically generated byproducts and enabling efficient handling of chemical and biological materials, including concentration and separation of ionic species, while preventing bulk fluid flow and gas transport.
Implementation Method 1
A bridging membrane is created in one of the intersecting channels or between the two adjacent channels. The bridging membrane permits an ionic electric current flow or gas transport while inhibiting bulk fluid flow therethrough.
Implementation Method 2
Electroosmosis is the bulk flow of fluid due to the combined effects of an electrical double layer in the presence of an axial electrical field. The high density of ions in the diffuse region of the double layer are pulled electrostatically by the electric field along the walls of the channel.
Implementation Method 3
Electrophoresis is the velocity imparted to an ion in solution when exposed to an electric field. The velocity of the ion is determined by the charge of the ion, the electric field strength, the viscosity of the solvent and the hydrodynamic radius of the ion.
Data Source
AI summary
A microfabricated device employing a bridging membrane and methods for electrokinetic transport of a liquid phase biological or chemical material using the same are described. The bridging membrane is deployed in or adjacent to a microchannel and permits either electric current flow or the transport of gas species, while inhibiting the bulk flow of material. The use of bridging membranes in accordance with this invention is applicable to electrokinetically inducing fluid flow to confine a selected material in a region of a microchannel that is not influenced by an electric field. Other structures for inducing fluid flow in accordance with this invention include nanochannel bridging membranes and alternating current fluid pumping devices. Applications of the bridging membranes according to this invention include the separation of species from a sample material, valving of fluids in a microchannel network, mixing of different materials in a microchannel, and the pumping of fluids.