Abstract: The present invention provides microfabricated fluidic systems and methods. Microfabricated fluidic devices of the present invention include switches that can be opened and closed to allow or block the flow of fluid through a channel in response to the pressure level in a gate of the switch. The microfabricated fluidic switches may be coupled together to perform logic functions and Boolean algebra, such as inverters, AND gates, NAND, gates, NOR gates, and OR gates. The logic gates may be coupled together to form flip-flops that latch signals. The present invention also includes microfabricated fluidic pressure multipliers that increase the pressure in a second chamber relative to a first chamber. Microfabricated fluidic devices of the present invention also include pressure sources. A pressure source of the present includes a pump coupled to a reservoir through unidirectional valves. The pressure source may be high pressure source or a low pressure source.

Abstract: A micropump includes a body (10) of semiconductor material, accommodating fluid-tight chambers (32), having an internal preset pressure, lower than atmospheric pressure. The fluid-tight chambers (32), sealed by a diaphragm (35) that can be electrically opened, are selectively openable using a first electrode (37) and second electrodes (38), accommodating between them portions of the diaphragm (35).

Abstract: A variable capacity hydraulic machine has a rotating group located within a casing and a control housing secured to the casing to extend across and seal an opening in the casing. The control housing accommodates a control circuit and a pair of sensors to sense change in parameters associated with the rotating group. One of the sensors is positioned adjacent the barrel on the rotating group to sense rotational speed and the other senses displacement of the swashplate. The control housing accommodates a control valve and accumulator to supply fluid to the control valve.

Abstract: In order to provide a seal arrangement for sealing between a first medium space filled with a first medium and a second medium space filled with a second medium which ensures reliable sealing between the medium spaces with very low leakage values even over a prolonged period of use, wherein said seal arrangement comprises a moveable component which is displaceable in the longitudinal direction thereof and/or rotatable about the longitudinal direction thereof and extends through the seal arrangement and wherein the seal arrangement comprises a sealing element which comprises a first sealing region that is sealing in relation to the first medium space and a second sealing region that is sealing in relation to the second medium space, wherein the first sealing region comprises a first dynamic sealing section abutting against the moveable component and the second sealing region comprises a second dynamic sealing section abutting against the moveable component and at least one of the two dynamic sealing sections h

Abstract: A pump includes an ink pressurizing chamber, an inlet port and an outlet port communicating with the chamber, a first valve member provided near the inlet port, a second valve member provided near the outlet port, a pressure adjustment channel communicating with the chamber, an electrode provided on a wall surface forming the channel, a driver IC which applies a voltage to the electrode, an insulating film provided on a surface of the electrode and in which when the voltage is applied to the electrode a wetting angle of ink on a surface of the insulating film is greater than that when no voltage is applied to the electrode, and a common electrode always in contact with ink in the chamber and held at a ground potential. Accordingly, a pump having a simple structure without any movable parts and with a low noise and less energy consumption can be provided.

Abstract: Macroscopic volumes of fluid can be moved across a surface, including windshields, without mechanical assistance. Insulated electrodes, which for windshields and windows are preferably transparent, are embedded in the surface of the windshield. Varying voltages are supplied to the electrodes to generate intense surface fringe electric fields moving in a given direction across the surface. The intense surface fringe electric fields exert strong electrical forces on the polar molecules of the fluid. These forces move the fluid in specific directions dependent on the geometry of the electrode array and the manner in which voltage is applied to each electrode within an array of electrodes.

Abstract: A number of micromachined devices including a micromachined pump for on-chip vacuum is provided. For example, a single-chip micromachined implementation of a Knudsen pump having one or more stages and which uses the principle of thermal transpiration with no moving parts is provided. A six-mask microfabrication process to fabricate the pump using a glass substrate and silicon wafer is shown. The Knudsen pump and two integrated pressure sensors occupy an area of 1.5 mm×2 mm. Measurements show that while operating in standard laboratory conditions, this device can evacuate a cavity to 0.46 atm using 80 mW input power. High thermal isolation is obtained between a polysilicon heater of the pump and the rest of the device.

Abstract: A gas injection port structure for a flat fluorescent lap (FFL) is provided. The FFL has a flat lower plate and an upper plate that form a channel therebetween, and at least one gas injection port in communication with the channel. The gas injection port may be formed at a predetermined position on the upper plate so that a height of the gas injection port is level with or lower than a height of the channel. The gas injection port may contain a mercury getter and a sealing material having a passage formed therethrough so that mercury vapor may be injected into the channel and then the channel sealed. The gas injection port minimizes a thickness of the FFL, and improves durability of the FFL.

Abstract: An electroosmotic micropump having a plurality of thin, closely-spaced, approximately planar, transversel aligned partitions formed in or on a substrate, among which electroosmotic flow (EOF) is generated. Electrodes are located within enclosed inlet and outlet manifolds on either side of the partition array. Inlet and outlet ports enable fluid to be pumped into and through the micropump and through an external friction load or head. Insulating layer coatings on the formed substrate limit substrate leakage current during pumping operation.

Abstract: A structure is prepared by preparing a getter assembly by furnishing a single-piece getter base including a getter substrate and a getter-shield precursor, affixing a getter material to the getter substrate, and processing the getter-shield precursor to form a getter shield. The processing is preferably performed by folding at least a portion of the getter-shield precursor to overlie the getter material affixed to the getter substrate. There may be provided a vacuum housing and a device. The getter assembly and the device are inserted into the vacuum housing, and the vacuum housing is evacuated and sealed.

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.

Abstract: Provided is an image display apparatus including: a vacuum container having an electron source enclosed therein for displaying an image; an ion pump communicating with the vacuum container for discharging air therefrom and decreasing pressure therein; and a resistor connected in series with the ion pump with respect to a power supply for driving the ion pump. Even if internal resistance of the ion pump undergoes order-of-magnitude changes according to its operating state, current consumption can be suppressed and the ion pump can be driven efficiently.

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 electrohydrodynamic conduction liquid pumping system includes a vessel configured to contain a liquid or a liquid/vapor therein. This vessel can be of a elongate conduit configuration, an elongate channel configuration or a liquid enclosure configuration. At least a single pair of electrodes are disposed in a spaced apart relation to each other on the vessel and configured to be oriented in the liquid. A power supply is coupled to the electrodes and operable to generate electric fields in between the pair of electrodes, the electric forces inducing a net liquid movement relative to the vessel. Various electrode designs are embraced within the concept of this invention.

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: The apparatus for generating ionic flow of media includes a DC voltage supply having a positive terminal and a negative terminal with a collector connected to the negative terminal of the direct current voltage supply. The collector has a substantially tubular configuration with a rear and front section with inwardly tapering frusto-conical section therebetween. An emitter pin is connected to the positive terminal of the direct current voltage supply with the majority of the tip being located within the frusto-conical section of the collector. Alternatively, the front section of the collector may be made of a dielectric material, such as plastic. As a result, fluid flow, such as air flow, is generated from the input port of the rear section of the collector, through the frusto-conical section of the collector and out the output port of the front section of the collector.

Abstract: Apparatus and methods according to the present invention preferably utilize electroosmotic pumps in fluid handling and field sampling applications. The electroosmotic pumps used in these applications are capable of generating high pressure and flow without moving mechanical parts and the associated generation of unacceptable electrical and acoustic noise, as well as the associated reduction in reliability. Having multiple small flow channels in parallel provides both a high flow rate and high pressure in liquid handling. These electroosmotic pumps are fabricated with materials and structures that improve performance, efficiency, and reduce weight and manufacturing cost relative to presently available micropumps. These electroosmotic pumps also allow for recapture of evolved gases and deposited materials, which may provide for long-term closed-loop operation.

Abstract: A system for detecting a collection of liquid, notifying a person or thing that liquid has been detected and pumping the liquid. The system includes a control unit, at least one sensor and relay and a pump. Preferably, the system includes a first sensor that senses a collection of liquid which activates a relay which completes an electrical circuit to activate a notification means, such as a siren, light, telephone dialer or other notification device. Preferably, the system also includes a second sensor that senses an additional collection of liquid and thereby activates a second relay which completes an electrical circuit and delivers DC power to the pump which pumps the additional collection of liquid to its desired location. The control unit includes a transformer, relays and plugs to connect to an AC or DC power supply, typically a standard 110 volt AC, 15 amp power supply.

Abstract: A valve which has a structure with at least one opening and a member which has a fixed static charge and also has a first position exposing the opening and a second position sealing the opening. A method for making the valve includes providing a structure with at least one opening and providing a member having a fixed static charge where the member has a first position exposing the opening and a second position sealing the opening. An agitator includes a base with at least one trench, a structure with at least one opening, and a membrane with a fixed static charge. The structure is connected to the base over the trench with the opening in the structure extending through to the trench in the base. The membrane is connected to the base across at least a portion of the trench. A pump includes a base with at least one trench, a structure with at least two openings, a membrane with a fixed static charge, a first cantilever arm having a fixed static charge, and a second cantilever arm having a fixed static charge.

Abstract: Apparatus and methods according to the present invention preferably utilize electroosmotic pumps that are capable of generating high pressure and flow without moving mechanical parts and the associated generation of unacceptable electrical and acoustic noise, as well as the associated reduction in reliability. These electroosmotic pumps are preferably fabricated with materials and structures that improve performance, efficiency, and reduce weight and manufacturing cost relative to presently available micropumps. These electroosmotic pumps also preferably allow for recapture of evolved gases and deposited materials, which may provide for long-term closed-loop operation. Apparatus and methods according to the present invention also allow active regulation of the temperature of the device through electrical control of the flow through the pump and can utilize multiple cooling loops to allow independent regulation of the special and temporal characteristics of the device temperature profiles.

Abstract: To prevent partial saturation of a getter by contact with absorbable atmospheric gases when the getter is introduced into a vacuum vessel, a method for introducing and activating the getter and a getter unit includes introducing the getter into the vacuum vessel packaged in a protective sleeve, closing off the vacuum vessel, evacuating the vessel, and opening the protective sleeve only after the evacuation has commenced. The protective sleeve can be opened by the sleeve being made to burst under the action of a protective gas atmosphere that is present.

Abstract: An apparatus that includes an electroosmotic pump and an aqueous or nonaqueous electrolyte liquid and generates relatively low amount of hydrogen gas is described herein. The apparatus may further include a hydrogen absorber.

Abstract: Microfluidic channels utilizing magnetohydrodynamics are used to pump very small volumes of solution. The channels have electrodes along the walls of the channel and a current carrying species within the solution carries the current through the solution. The electric field generated by the use of the current carrying species is perpendicular to a magnetic field applied to the channel. The combination of the electric and magnetic fields causes the solution to flow through the channel.

Abstract: A fluid pump for pumping fluid. The fluid pump includes a driver having a substantially tubular shaped body defining a body axis and, a number of elements circumferentially spaced around the body. Each element is responsive to a signal to so as cause a corresponding portion of the body to expand or contract in a direction substantially parallel to the tube axis. The pump also includes an urging member positioned in a flow path. In use, the urging member is coupled to the driver such that selective expansion and/or contraction of the body causes the urging member to rotate, thereby urging fluid along the flow path.

Abstract: An electroosmotic pump and method of manufacturing thereof. The pump having a porous structure adapted to pump fluid therethrough, the porous structure comprising a first side and a second side, the porous structure having a plurality of fluid channels therethrough, the first side having a first continuous layer of electrically conductive porous material deposited thereon and the second side having a second continuous layer of electrically conductive porous material deposited thereon, the first second layers coupled to a power source, wherein the power source supplies a voltage differential between the first layer and the second layer to drive fluid through the porous structure at a desired flow rate. The continuous layer of electrically conductive porous material is preferably a thin film electrode, although a multi-layered electrode, screen mesh electrode and beaded electrode are alternatively contemplated.

Abstract: An improved getter device and method for forming a calcium-rich getter thin film in an electronic vacuum device is disclosed. The getter device includes a powder of a Ca—Ba—Al ternary alloy composed of between 53% and 56.8% by weight of aluminum, from 36% to 41.7% by weight of calcium and from 1.5% to 11% by weight of barium. The method allows the formation of a calcium-rich getter thin film with a substantially reduced amount of released hydrogen in the vacuum 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: The invention relates to a device for displacement of at least a small volume of liquid (5) under the effect of an electrical control, including a substrate (1) provided with first electrically conducting means (2), the device also comprising second electrically conducting means (3) arranged facing the first electrically conducting means (2), the first electrically conducting means and the second electrically conducting means possibly being connected to electrical power supply means to enable the application of electrostatic forces to the small liquid volume (5). The second electrically conducting means include at least one conducting wire (3) arranged parallel to the substrate and at a fixed distance from the substrate to enable displacement of the small volume of liquid (5) along said conducting wire (3) under the effect of the applied electrostatic forces.

Abstract: The present invention provides a pump for generating an Electroosmotic Flow (EOF) in a solution in a canal, guide, pipe or equivalent. Electroosmotic flow is generated by application of an electric field through a solution in a canal defined by insulating walls. The phenomenon depends on ionisation of sites on the surface so that for electroneutrality there is an excess mobile charge in the solution. The electric field acts on the excess charge in the solution causing the fluid to flow. The quantity and distribution of excess charge in the solution depends on the solution and the surface materials and is related to a parameter, the zeta (z) potential characterising material/solution combinations.

Abstract: An electrode configuration for use in association with a heat transfer member provided in a thermal energy transfer system. Separate multiple electrical conductors are each received on a respective first surface alteration. Each of the multiple conductors is connected to a different terminal of a multiphase alternating power source so that an electric traveling wave moves in a longitudinal direction of the heat transfer member so as to induce pumping of at least the liquid phase in the longitudinal direction to thereby enhance the thermal energy transfer characteristics of the thermal energy transfer system. In a preferred embodiment, the aforementioned heat transfer members are provided inside of an outer conduit.

Abstract: The present disclosure relates generally to microelectronic technology, and more specifically, to an apparatus used for the cooling of active electronic devices utilizing electro-osmotic pumps and micro-channels.

Abstract: A high efficiency plasma pump for use in a plasma processing system that includes a plasma processing device having a first plasma density proximate a processing region and a second plasma density proximate an exit region is disclosed. The plasma pump includes an inter-stage plasma (ISP) source fluidly coupled to the plasma processing device proximate the exit region, the ISP source comprising an inter-stage plasma region having a third plasma density; and a plasma pump fluidly coupled to the ISP, the plasma pump having a fourth plasma density, wherein pumping speed is dependent upon the third plasma density and the fourth plasma density. The ISP source increasing the third plasma density to increase the pumping efficiency.

Abstract: An electrohydrodynamic (EHD) conduction pump is provided for pumping dielectric liquids, and a particular adaptation for mass transport of isothermal and non-isothermal single phase liquids. The EHD conduction pump does not require direct injection of electric charges into the fluid. The EHD conduction pump includes an EHD pumping section and associated connecting tubes with electrodes arranged in series in the pumping section. The electrodes are coupled to a high voltage low current dc power supply. A positive polarity dc voltage is applied to the electrodes. Various electrode configurations may be used, such as three-needle, hollow-tube, or pin-needle electrode configuration.

Abstract: A method for preventing contamination, oxidation and gas absorption of reactive materials, and articles formed thereby. The method generally entails depositing a first layer of a reactive material and a second layer of a substantially nonreactive material so that the second layer protects the first layer from a surrounding atmosphere. For example, the first and second layers may be deposited to form a film on a surface within a chamber that is desired to be maintained in a vacuum during use of the article. The second layer is sufficiently thin such that appropriately heating the first and second layers causes the reactive material of the first layer to become interdiffused with the nonreactive material of the second layer, to the extent that at least a portion of the reactive material is able to react and getter gases from the surrounding atmosphere.

Abstract: A closed-drift Hall effect plasma vacuum pump includes one or more pumping conduits which are linked with a radial magnetic field. The magnetic field separates a plasma from a plasma at a higher pressure which is formed by cross-field plasma transport from a plasma processing region.

Abstract: The invention concerns a device comprising at least one field effect electron source within a sealed structure, which encompasses an internal space that contains a reducing gas whose purpose is to prevent oxidation of the emissive material of the electron source, whereby the reducing gas is a gas with the formula NxHy where x=1 or 2 and y=3 or 4, and which is advantageously under a pressure of between 10?8 and 10?1 mbar. It also concerns manufacturing processes for such a device and apparatuses for implementing these processes.

Abstract: An electrokinetic pump for pumping a liquid includes a pumping body having a plurality of narrow, short and straight pore apertures for channeling the liquid through the body. A pair of electrodes for applying a voltage differential are formed on opposing surfaces of the pumping body at opposite ends of the pore apertures. The pumping body is formed on a support structure to maintain a mechanical integrity of the pumping body. The pump can be fabricated using conventional semiconductor processing steps. The pores are preferably formed using plasma etching. The structure is oxidized to insulate the structure and also narrow the pores. A support structure is formed by etching a substrate and removing an interface oxide layer. Electrodes are formed to apply a voltage potential across the pumping body. Another method of fabricating an electrokinetic pump includes providing etch stop alignment marks so that the etch step self-terminates.

Abstract: A stand-alone plasma vacuum pump for pumping gas from a low-pressure inlet to a high-pressure outlet, composed of: a housing enclosing one or more pumping regions located between the inlet and the outlet; a plurality of permanent magnet assemblies providing magnetic fields that extend in the pumping region between the inlet and the outlet, the magnetic field forming magnetic flux channels for guiding and confining plasmas; elements disposed for coupling microwave power into the flux channels to heat electrons, ionize gas, and accelerate plasma ions in a direction from the inlet to the outlet; elements disposed for creating an electric in the magnetic flux channels to accelerate ions in the flux channels toward the outlet by momentum transfer; and a differential conductance baffle proximate to the outlet for promoting flow of plasma ions and neutral atoms to the outlet.

Abstract: An evaporable getter device is provided for cathode-ray tubes (CRTs). The getter device is formed by a metallic container (101; 201) containing a mixture of powders (104; 205) of the compound BaAl4 and nickel (Ni), and by two different metallic nets (106, 107; 207, 208), superimposed and positioned in the container over the powders. The device allows one to obtain a barium distribution in the CRT that is more uniform and wider than that obtainable with a conventional getter device.

Abstract: A vacuum container includes a getter filled with a gettering material for maintaining a vacuum condition, and includes a getter support which includes a control plate member, a support leg and a holder. The getter support is arranged in the spreading direction of the getter material in order to limit the directions of the spreading of the getter material. This structure reduces the number of relevant components, simplifies the procedure of fabrication and maintains the degree of vacuum.

Abstract: A getter device is shaped like a substrate used in a deposition process. Embodiments of the device include a powdered getter material coated onto one or both sides of a support with a narrow rim portion left uncoated so that the device can be manipulated by automatic handling equipment. A method for using the getter device includes providing a vacuum chamber and automatic handling equipment, loading the device into the chamber, reducing the chamber pressure to a desired value by using the getter device in conjunction with an external pump, removing the getter device and replacing it with a substrate, and depositing a thin film on the substrate. The getter device can be in an activated state when loaded into the chamber, or it can be activated after being loaded by employing heating equipment ordinarily used to heat substrates placed in the chamber. The getter material of the device may also be activated in a separate activation chamber before the getter device is loaded into the vacuum chamber.

Abstract: An apparatus for removing contaminants from a display device is disclosed. In one embodiment, an auxiliary chamber is adapted to be coupled to a surface of a display device such that contaminants within the display device can travel from the display device into the auxiliary chamber. A getter is disposed in the auxiliary chamber. The getter is adapted to capture the contaminants once the contaminants travel from the display device into the auxiliary chamber. In other embodiments, the getter is disposed in the border region surrounding the active area of the display.

Abstract: An arc discharge lamp has an arc chamber with an amalgam tip attached to and communicating with the arc chamber through a constricted area. An amalgam retainer is positioned in the arc chamber and is abutted against the constricted area. The amalgam retainer is vibration-insensitive, solid and liquid amalgam impervious and mercury vapor pervious. An amalgam is contained within the amalgam tip.

Abstract: In a method for manufacturing an electron tube including a front substrate and a back substrate, a wiring and an electrode are formed on the front substrate and/or the back substrate. A component is mounted on the front substrate and/or the back substrate. A ring-less getter is mounted on at least one of the front substrate, the back substrate and the component. A vessel is assembled and sealed so that the front substrate faces the back substrate. A light is irradiated on the ring-less getter from outside of the sealed vessel, thereby activating the ring-less getter.

Abstract: An ion pump includes one or more anode pump cells, a cathode positioned in proximity to the one or more anode pump cells and a magnet assembly for producing a magnetic field in the one or more anode pump cells. An electric field is applied between the cathode and the one or more anode pump cells. The magnet assembly includes primary magnets of opposite polarities disposed on opposite ends of the anode pump cells and secondary magnets disposed on opposite sides of the anode pump cells. The magnet assembly may further include a magnet yoke which provides a magnetic flux return path. The magnet assembly produces a substantially uniform axial magnetic field in the one or more anode pump cells.

Abstract: An electrostatic fluid regulating device and methods. The device has a substrate. The device also has a first electrode coupled to the substrate. The device has a polymer based diaphragm. A second electrode is coupled to the diaphragm. A polymer based fluid chamber is coupled to the diaphragm. The device also has an inlet coupled to the polymer based fluid chamber and an outlet coupled to the polymer based fluid chamber.

Abstract: The present invention provides a pump for generating an Electroosmotic Flow (EOF) in a solution in a canal, guide, pipe or equivalent. Electroosmotic flow is generated by application of an electric field through a solution in a canal defined by insulating walls. The phenomenon depends on ionisation of sites on the surface so that for electroneutrality there is an excess mobile charge in the solution. The electric field acts on the excess charge in the solution causing the fluid to flow. The quantity and distribution of excess charge in the solution depends on the solution and the surface materials and is related to a parameter, the zeta (z) potential characterising material/solution combinations.

Abstract: An electroosmotic micropump having a plurality of planar features formed in a substrate to form an electroosmotic flow (EOF) pumping region. Inlet and outlet manifolds on either side of the pumping region to enable fluid to be pumped into and through the micropump. A cover is bonded to the substrate to seal the pumping region and manifolds. An insulating layer coating is applied to the formed substrate to reduce current flow when an electric filed is applied during pumping operation. An additional layer is applied on top of the insulating layer to provide electrochemistry at the liquid-solid interface in the electroosmotic micropump that enhances micropump performance.

Abstract: The invention relates to a fan blower (18) for a heating/air conditioning system, in particular for a motor vehicle, with an impeller (22) and a motor (24) that drives this impeller (22).

Abstract: The present invention provides a pump for generating an Electroosmotic Flow (EOF) in a solution in a canal, guide, pipe or equivalent. Electroosmotic flow is generated by application of an electric field through a solution in a canal defined by insulating walls. The phenomenon depends on ionisation of sites on the surface so that for electroneutrality there is an excess mobile charge in the solution. The electric field acts on the excess charge in the solution causing the fluid to flow. The quantity and distribution of excess charge in the solution depends on the solution and the surface materials and is related to a parameter, the zeta (z) potential characterising material/solution combinations.