Polymeric salt bridges for conducting electric current in microfluidic devices
Inventors
Shepodd, Timothy J. • Tichenor, Mark S. • Artau, Alexander
Assignees
National Technology and Engineering Solutions of Sandia LLC • Sandia National Laboratories
Publication Number
US-7618524-B1
Publication Date
2009-11-17
Expiration Date
2024-08-10
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Abstract
A “cast-in-place” monolithic microporous polymer salt bridge for conducting electrical current in microfluidic devices, and methods for manufacture thereof is disclosed. Polymeric salt bridges are formed in place in capillaries or microchannels. Formulations are prepared with monomer, suitable cross-linkers, solvent, and a thermal or radiation responsive initiator. The formulation is placed in a desired location and then suitable radiation such as UV light is used to polymerize the salt bridge within a desired structural location. Embodiments are provided wherein the polymeric salt bridges have sufficient porosity to allow ionic migration without bulk flow of solvents therethrough. The salt bridges form barriers that seal against fluid pressures in excess of 5000 pounds per square inch. The salt bridges can be formulated for carriage of suitable amperage at a desired voltage, and thus microfluidic devices using such salt bridges can be specifically constructed to meet selected analytical requirements.
Core Innovation
The invention provides a cast-in-place monolithic microporous polymer salt bridge for conducting electrical current within microfluidic devices. These polymeric salt bridges are formed in situ within capillaries or microchannels by injecting a formulation that includes monomers, suitable cross-linkers, solvents, and initiators which are then polymerized using radiation such as UV light or by thermal curing. The resulting monolithic salt bridge conforms to the microchannel shape and possesses sufficient porosity to allow ionic migration while preventing bulk fluid flow through the bridge.
A key aspect of the invention is that the polymeric salt bridges seal against high fluid pressures, exceeding 5000 pounds per square inch, and can be formulated to carry specific amperages at desired voltages, facilitating microfluidic devices that meet analytical requirements. The bridges can be tailored for strength, flexibility and compatibility with aqueous or organic solvents and analytical reagents. This cast-in-place approach allows stable, electrically conductive yet fluid flow resistive structures to be integrally manufactured within microfluidic channels, avoiding the disadvantages of metal electrodes in such devices.
Claims Coverage
The patent includes one independent claim defining the core features of a microfluidic device incorporating a polymeric salt bridge.
Integration of a monolithic microporous polymer salt bridge in microchannels
The device includes a polymeric salt bridge formed in situ within a selected microchannel portion so as to substantially block bulk fluid flow while enabling ionic conduction.
Formulation parameters for the polymeric salt bridge
The salt bridge is formulated using a selected first monomer and first cross-linker (ethoxylated (15) trimethylolpropane triacrylate) alongside solvent and initiator, where monomer and cross-linker determine porosity and ionic conductivity at a specified voltage.
Electrical conduction and structure of the polymeric salt bridge
The polymeric salt bridge has defined first and second ends along the microchannel and conducts electricity by ionic migration when voltage is applied.
The independent claim covers a microfluidic device including a polymeric salt bridge formed in situ with defined formulation parameters to achieve controlled porosity and conductivity, which effectively conduces ions while resisting bulk fluid flow.
Stated Advantages
The salt bridges provide a low resistance electrical path enabling completion of electrical circuits in microfluidic devices.
The polymeric salt bridges block bulk fluid flow and seal against high fluid pressures up to or exceeding 6000 pounds per square inch.
They allow formulation to meet desired amperage and voltage requirements and are compatible with varied solvents and analytical reagents.
The bridges can be rapidly fabricated in place via UV or thermal polymerization, simplifying manufacturing without expensive assembly.
Documented Applications
Use in microfluidic systems for chemical, physical, and electrochemical analyses including analytical chemistry, biochemistry, medical testing, and industrial process control.
Serving as electrically conductive but fluid flow resistive elements within microfluidic channels, aiding electroosmosis and electrophoresis.
Incorporation in microfluidic devices that utilize electrokinetic pumping and fluid manipulation requiring high pressure resistive seals.
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