Abstract: An electrokinetic device is capable of operating for extended periods of time, e.g. days to a week, without producing significant gaseous byproducts and without significant evolution of the pump fluid. Features of the electrokinetic device include: the electrodes in the electrokinetic device are capacitive with a capacitance of at least 10−4 Farads/cm2; at least part of the inner surfaces of the electrodes have an area greater than the effective area of the porous dielectric material; at least part of the inner surfaces of the electrodes have a current flux less than 20 microamperes/cm2; and at least part of the inner surfaces of the electrodes have a current flux that varies by less than a factor of two. The electrokinetic device can have one or several of these features in any combination.

Abstract: An electrokinetic pump achieves high and low flow rates without producing significant gaseous byproducts and without significant evolution of the pump fluid. A first feature of the pump is that the electrodes in the pump are capacitive with a capacitance of at least 10−4 Farads/cm2. A second feature of the pump is that it is configured to maximize the potential across the porous dielectric material. The pump can have either or both features.

Abstract: A laminated flow device comprises a porous material encapsulated within bonding material. The porous material forms a flow path and the bonding material forms an enclosure surrounding the flow path. Micro-components, such as capillaries, electrodes, reservoirs, bridges, electrokinetic elements, and detectors, can be encapsulated within the device.

Abstract: In accordance with the present invention, stable electroosmotic flow systems and methods for designing the same are disclosed. The invention provides electroosmotic flow systems comprising electroosmotic flow elements, including bridge elements, that have matching flux ratios, i.e., when two or more elements of an electroosmotic flow system are in fluidic and electrical communication at a junction, the flux ratio for each of the elements is selected so that the difference in flux ratios of any two elements is less than a target value. The invention also provides methods for designing such systems. Also disclosed is a novel design for the terminal portions of electroosmotic flow (EOF) and bridge elements and for junctions in electroosmotic flow systems, whereby the elements are designed so that the terminal current flux is much smaller than the element current flux.

Abstract: An electrokinetic high pressure hydraulic pump for manipulating fluids in capillary-based system. The pump uses electro-osmotic flow to provide a high pressure hydraulic system, having no moving mechanical parts, for pumping and/or compressing fluids, for providing valve means and means for opening and closing valves, for controlling fluid flow rate, and manipulating fluid flow generally and in capillary-based systems (microsystems), in particular. The compact nature of the inventive high pressure hydraulic pump provides the ability to construct a micro-scale or capillary-based HPLC system that fulfills the desire for small sample quantity, low solvent consumption, improved efficiency, the ability to run samples in parallel, and field portability. Control of pressure and solvent flow rate is achieved by controlling the voltage applied to an electrokinetic pump.

Abstract: Microfluidic devices are disclosed which can be manufactured using surface-micromachining. These devices utilize an electroosmotic force or an electromagnetic field to generate a flow of a fluid in a microchannel that is lined, at least in part, with silicon nitride. Additional electrodes can be provided within or about the microchannel for separating particular constituents in the fluid during the flow based on charge state or magnetic moment. The fluid can also be pressurized in the channel. The present invention has many different applications including electrokinetic pumping, chemical and biochemical analysis (e.g. based on electrophoresis or chromatography), conducting chemical reactions on a microscopic scale, and forming hydraulic actuators.

Abstract: A precision flow controller is capable of providing a flow rate less than 100 microliters/minute and varying the flow rate in a prescribed manner that is both predictable and reproducible where the accuracy and precision of the flowrate is less than 5% of the flow rate. A plurality of variable pressure fluid supplies pump fluid through a single outlet. Flowmeters measure the flow rates and a controller compares the flow rates to desired flowrates and, if necessary, adjusts the plurality of variable pressure fluid supplies so that the variable pressure fluid supplies pump fluid at the desired flow rate. The variable pressure fluid supplies can be pneumatically driven.

Abstract: A flowmeter for accurately measuring the flowrate of fluids in high pressure chromatography systems. The flowmeter is a porous bed of a material, the porous bed having a porosity in the range of about 0.1 to 0.6 and a pore size in the range of about 50 nm to 1 &mgr;m, disposed between a high pressure pumping means and a chromatography column. The flowmeter is provided with pressure measuring means at both the inlet and outlet of the porous bed for measuring the pressure drop through the porous bed. This flowmeter system provides not only the ability to measure accurately flowrates in the range of &mgr;L/min to nL/min but also to provide a signal that can be used for a servo loop or feedback control system for high pressure pumping systems.

Abstract: An electrokinetic pump capable of producing high pressure is combined with a nozzle having a submicron orifice to provide a high pressure spray device. Because of its small size, the device can be contained within medical devices such as an endoscope for delivering biological materials such as DNA, chemo therapeutic agents, or vaccines to tissues and cells.

Abstract: Electroosmotic flow controllers that may be used in conjunction with multiple fluids and methods of fluid flow control are described. The invention uses an electroosmotically generated flow component in combination with a pressure driven flow component to modulate fluid flow. A working fluid and a second fluid that supports electroosmotic function may be used in conjunction with embodiments of the invention. Embodiments of the invention may include salt bridges for making electrical connections between a power supply and a channel filled with a porous dielectric material and a fluid.

Abstract: Electroosmotic flow controllers and methods of fluid flow control are described. The invention uses an electroosmotically generated flow component in conjunction with a pressure driven flow component to modulate fluid flow. The devices and methods of the invention may include salt bridges for making electrical connection between a power supply and a channel filled with a porous dielectric material and a fluid. Embodiments including flow controllers and flow splitters are described as is their use in a variety of fluid handling applications.

Abstract: An electrokinetic pump capable of producing high pressure is combined with a nozzle having a submicron orifice to provide a high pressure spray device. Because of its small size, the device can be contained within medical devices such as an endoscope for delivering biological materials such as DNA, chemo therapeutic agents, or vaccines to tissues and cells.

Abstract: A flowmeter for accurately measuring the flowrate of fluids in high pressure chromatography systems. The flowmeter is a porous bed of a material, the porous bed having a porosity in the range of about 0.1 to 0.6 and a pore size in the range of about 50 nm to 1 &mgr;m, disposed between a high pressure pumping means and a chromatography column. The flowmeter is provided with pressure measuring means at both the inlet and outlet of the porous bed for measuring the pressure drop through the porous bed. This flowmeter system provides not only the ability to measure accurately flowrates in the range of &mgr;L/min to nL/min but also to provide a signal that can be used for a servo loop or feedback control system for high pressure pumping systems.

Abstract: A flowmeter for accurately measuring the flowrate of fluids in high pressure chromatography systems. The flowmeter is a porous bed of a material, the porous bed having a porosity in the range of about 0.1 to 0.6 and a pore size in the range of about 50 nm to 1 &mgr;m, disposed between a high pressure pumping means and a chromatography column. The flowmeter is provided with pressure measuring means at both the inlet and outlet of the porous bed for measuring the pressure drop through the porous bed. This flowmeter system provides not only the ability to measure accurately flowrates in the range of &mgr;L/min to nL/min but also to provide a signal that can be used for a servo loop or feedback control system for high pressure pumping systems.

Abstract: Apparatus and method for improving the resolution of non-pressure driven capillary chromatographic systems, and particularly for capillary electrochromatography (CEC) systems. By reducing the cross-sectional area of a packed capillary column by means of a second open capillary contiguous with the outlet end of a packed capillary column, where the packed capillary column has a cross sectional area of between about 2 and 5 times that of the open capillary column, the phenomenon of band broadening in the transition region between the open capillary and the packed capillary column, where the individual components of the mixture are analyzed, can be eliminated, thereby providing for a significant improvement in resolution and more accurate detection and analysis.

Abstract: Apparatus and method for driving a sample, having a well-defined volume, under pressure into a chromatography column. A conventional high pressure sampling valve is replaced by a sample injector composed of a pair of injector components connected in series to a common junction. The injector components are constructed so as to provide for electroosmotic flow of a sample into the junction. At an appropriate time, a pressure pulse from a high pressure source, that can be an electrokinetic pump, connected to the common junction, drives a portion of the sample, whose size is determined by the dead volume of the common junction, into the chromatographic column for subsequent separation and analysis. The apparatus can be fabricated on a substrate for microanalytical applications.

Abstract: Apparatus and method for driving a sample, having a well-defined volume, under pressure into a chromatography column. A conventional high pressure sampling valve is replaced by a sample injector composed of a pair of injector components connected in series to a common junction. The injector components are containers of porous dielectric material constructed so as to provide for electroosmotic flow of a sample into the junction. At an appropriate time, a pressure pulse from a high pressure source, that can be an electrokinetic pump, connected to the common junction, drives a portion of the sample, whose size is determined by the dead volume of the common junction, into the chromatographic column for subsequent separation and analysis. The apparatus can be fabricated on a substrate for microanalytical applications.

Abstract: A method for eliminating gas bubble blockage of current flow during operation of an electrokinetic pump. By making use of the ability to modify the surface charge on the porous dielectric medium used in electrokinetic pumps, it becomes possible to place electrodes away from the pressurized region of the electrokinetic pump. While gas is still generated at the electrodes they are situated such that the generated gas can escape into a larger buffer reservoir and not into the high pressure region of the pump where the gas bubbles can interrupt current flow. Various combinations of porous dielectric materials and ionic conductors can be used to create pumps that have desirable electrical, material handling, and flow attributes.

Abstract: An electrokinetic high pressure hydraulic pump for manipulating fluids in capillary-based systems. The pump uses electro-osmotic flow to provide a high pressure hydraulic system, having no moving mechanical parts, for pumping and/or compressing fluids, for providing valve means and means for opening and closing valves, for controlling fluid flow rate, and manipulating fluid flow generally and in capillary-based systems (Microsystems), in particular. The compact nature of the inventive high pressure hydraulic pump provides the ability to construct a micro-scale or capillary-based HPLC system that fulfills the desire for small sample quantity, low solvent consumption, improved efficiency, the ability to run samples in parallel, and field portability. Control of pressure and solvent flow rate is achieved by controlling the voltage applied to an electrokinetic pump.

Abstract: A valve for controlling fluid flows. This valve, which includes both an actuation device and a valve body provides: the ability to incorporate both the actuation device and valve into a unitary structure that can be placed onto a microchip, the ability to generate higher actuation pressures and thus control higher fluid pressures than conventional microvalves, and a device that draws only microwatts of power. An electrokinetic pump that converts electric potential to hydraulic force is used to operate, or actuate, the valve.