Electrokinetic pump
Inventors
Assignees
National Technology and Engineering Solutions of Sandia LLC • Sandia National Laboratories
Publication Number
US-7297246-B2
Publication Date
2007-11-20
Expiration Date
2024-04-22
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Abstract
A method for altering the surface properties of a particle bed. In application, the method pertains particularly to an electrokinetic pump configuration where nanoparticles are bonded to the surface of the stationary phase to alter the surface properties of the stationary phase including the surface area and/or the zeta potential and thus improve the efficiency and operating range of these pumps. By functionalizing the nanoparticles to change the zeta potential the electrokinetic pump is rendered capable of operating with working fluids having pH values that can range from 2-10 generally and acidic working fluids in particular. For applications in which the pump is intended to handle highly acidic solutions latex nanoparticles that are quaternary amine functionalized can be used.
Core Innovation
The invention relates to an electrokinetic pump (EKP) configuration where nanometer-size particles are fixedly attached to the surface of the particles comprising the stationary phase in a porous dielectric material disposed in a microchannel. This method alters the surface charge (zeta potential) and surface area of the stationary phase, thereby improving the efficiency and operating range of the pump. The particles used in the stationary phase are preferably silica beads to which functionalized nanoparticles are bonded, typically by electrostatic attraction, but also by chemical or physical means.
The problem being addressed arises from limitations in existing electrokinetic pumps, especially their inability to operate effectively under a wide range of pH values, particularly acidic conditions. Traditional silica surfaces have high zeta potentials but are effective mainly at neutral to basic pH, and are unstable at lower pH due to dissolution. Prior surface modifications to channel walls or stationary phases have issues such as limited lifetime, surface contamination, charge neutralization, and complex fabrication. Polymer monoliths with charged groups suffer from low surface charge density and structural fragility. Existing approaches do not reliably produce pumps that can operate efficiently in highly acidic solutions at high pressures.
The core innovation involves using nanoparticles, such as latex particles functionalized with quaternary amine groups (NR4+), bonded to silica stationary phase particles to produce a pump capable of operating effectively across a broad pH range, specifically from pH 2 to 10, and particularly in acidic environments. This configuration leverages the high structural integrity and narrow pore size distribution of packed silica beads combined with increased surface area and enhanced zeta potential from the nanoparticle coating. The resulting electrokinetic pump can generate high hydraulic pressures, exceeding 5000 psi, with improved efficiency, reduced power dissipation, and enhanced robustness, enabling operation with challenging electrolytes such as highly acidic solutions.
Claims Coverage
The patent includes two independent claims covering an electrokinetic pump with specific structural and functional features. The claims focus on the composition of the stationary phase and its functionalized surface to enable improved pump performance, particularly with acidic solutions.
Nanoparticle-coated stationary phase
The electrokinetic pump comprises a microchannel with a porous dielectric stationary phase comprising a bed of nonporous particles whose surfaces have nanoparticles fixedly attached thereto.
Functionalized nanoparticles for altered surface properties
The use of functionalized nanoparticles, including polymer, colloidal metal, or metal oxide particles, notably functionalized latex nanoparticles, to modify surface charge and area of the stationary phase.
Quaternary amine functionalized latex nanoparticles for acidic pumping
The stationary phase's nonporous particles surfaces have quaternary amine functionalized latex nanoparticles fixedly attached, enabling the pump to handle acid electrolytes effectively.
The inventive features center on modifying the stationary phase surfaces with fixedly attached functionalized nanoparticles, especially quaternary amine functionalized latex nanoparticles on silica particles, to produce an electrokinetic pump capable of operating at a wide pH range and particularly effective for pumping acidic solutions with high efficiency and robustness.
Stated Advantages
Enables operation of electrokinetic pumps with working fluids having pH values ranging from 2 to 10, including highly acidic solutions.
Improved pump efficiency by increasing the surface area and zeta potential through nanoparticle functionalization.
Allows use of packed silica beads as a stationary phase with high structural integrity and narrow pore size distribution.
Capability to generate hydraulic pressures greater than about 5000 psi with highly acidic solutions.
Reduces power dissipation in microfluidic devices and minimizes current flow-related issues such as concentration polarization and Joule heating.
Documented Applications
Use in fluid dispensing and metering in microfluidic devices.
Application in high pressure liquid chromatography systems.
Use in micro-analysis systems generally requiring precise fluid delivery.
Electrokinetic pumping of acidic electrolyte solutions with pH below 4 at pressures exceeding 5000 psi.
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