Abstract: A microfluidic chip configured to move a microdroplet along a predetermined path, includes a plurality of probe electrode groups spaced apart along the predetermined path. Each of the plurality of probe electrode groups includes a first probe electrode and a second probe electrode spaced apart from each other. The first probe electrode and the second probe electrode among a plurality of first probe electrodes and a plurality of second probe electrodes are configured to form an electrical loop with the microdroplet to thereby facilitate determining a position of the microdroplet.

Abstract: A DNA extraction device may include a substrate, at least one first side channel electrode, at least one second side channel electrode, optionally, at least one elongate central channel electrode, and a voltage source connected between the electrodes. The substrate defines an elongate central channel defining a major axis. A width of the elongate central channel is greater than its depth, and its depth is less than about 15 times a diameter of a cell to be introduced in the elongate central channel. The substrate also defines first and second side channels adjacent to the elongate central channel on opposite sides of the major axis. The substrate further defines first and second trapezoidally shaped connecting channels connecting the elongate central channel and the first and second side channels, respectively. The smaller parallel sides of the first and second trapezoidally shaped connecting channels open to the respective side channels.

Abstract: A method for the examination of a sample includes illuminating the sample in a sample plane along a sample line with an illuminating light beam. The sample is acted upon by a depletion or switching light beam, which overlaps in the sample plane in an overlap region with the illuminating light beam. Part of fluorescent light emanating from the sample plane is detected as detection light originating from a first subregion of the overlap region, in which the probability of an interaction of the sample molecules with the depletion or switching light beam is greater than 90%, and/or originating from a second subregion which is at least partially surrounded by the first sub-region and/or in which the depletion or switching light beam has a zero point, while at the same time the fluorescent light originating from outside the first subregion and the second subregion is suppressed and not detected.

Abstract: An apparatus and a method are provided for selectively and rapidly applying heat to a nanoscale environment in a controlled manner. The technology utilizes laser irradiation of a solid state material to heat a nanoscale point of interest by an optothermal effect. The technology can be used to the tip of an atomic force microscope, a spot on a flat surface, or a nanopore, or molecules in their vicinity. The apparatus and method are capable of rapidly scanning the temperature of a nanoscale object such as a molecule or biomolecular complex and to interrogate properties of the object at high throughput. The methods can be used in nanofabrication processes or to drive single molecule chemistry.

Abstract: A system includes a housing, a cartridge retainer disposed within the housing, a detection assembly disposed within the housing, and a reagent tray holder movably disposed in the housing. The cartridge retainer configured to receive a capillary cartridge having a capillary. The detection assembly includes at least one emitter, a first detector, and a second detector. The detection assembly is configured to transition between a first configuration, in which the first detector detects a first output of the at least one emitter, and a second configuration, in which the second detector detects a second output of the at least one emitter. The reagent tray holder is configured to move relative to the cartridge retainer to place the capillary of the capillary cartridge in fluid communication with a reagent volume.

Abstract: A sample analysis method capable of improving separation accuracy of at least one of hemoglobin A2 and hemoglobin S and downsizing an analysis device is provided. The method includes separating hemoglobin in a sample in an alkaline solution containing a cationic polymer by capillary electrophoresis.

Abstract: Compositions, devices, and methods are disclosed for the covalent modification of polymer surfaces with graft copolymers having a blend of side chains. The halogenated acrylic and polyalkylene glycol acrylic side chains of the graft copolymer provide the polymer surface with high hydrophobicity, as well as increased resistance to biofouling with proteinaceous material. The polymer surfaces can be particularly useful in microfluidic devices and methods that involve the contacting of the covalently modified polymer surfaces with emulsions of aqueous droplets containing biological macromolecules within an oil carrier phase.

Abstract: A capillary ionic transistor and method of using is disclosed. The method including providing a capillary pipette (100) having an inner surface defining a channel, and a conductive layer disposed (102) about electrode the channel; filling at least a portion of the channel with an ionic solution (110) such that an electrical double layer forms on the inner surface of the pipette; inducing an electric potential within the ionic solution sufficient to generate a longitudinal flow of ions within the channel; and inducing an electric potential in the conductive layer sufficient to alter the zeta potential of the electrical double layer and adjust the flow of ions within the ionic solution.

Abstract: Methods, systems and devices that generate differential axial transport in a fluidic device having at least one fluidic sample separation flow channel and at least one ESI emitter in communication with the at least one sample separation flow channel. In response to the generated differential axial transport, the at least one target analyte contained in a sample reservoir in communication with the sample separation channel is selectively transported to the at least one ESI emitter while inhibiting transport of contaminant materials contained in the sample reservoir toward the at least one ESI emitter thereby preferentially directing analyte molecules out of the at least one ESI emitter. The methods, systems and devices are particularly suitable for use with a mass spectrometer.

Abstract: A process for producing an optical glass with an anti-fog coating is disclosed. The process includes the steps of: a) providing an optical glass, b) preparing a layer having Si—H groups (silane groups) on the optical glass, and c) reacting the silane groups with a compound having hydrophilic groups and at least one group reactive to the silane group.

Abstract: Methods, systems and devices that generate differential axial transport in a fluidic device having at least one fluidic sample separation flow channel and at least one ESI emitter in communication with the at least one sample separation flow channel. In response to the generated differential axial transport, the at least one target analyte contained in a sample reservoir in communication with the sample separation channel is selectively transported to the at least one ESI emitter while inhibiting transport of contaminant materials contained in the sample reservoir toward the at least one ESI emitter thereby preferentially directing analyte molecules out of the at least one ESI emitter. The methods, systems and devices are particularly suitable for use with a mass spectrometer.

Abstract: Methods, systems and devices that generate differential axial transport in a fluidic device having at least one fluidic sample separation flow channel and at least one ESI emitter in communication with the at least one sample separation flow channel. In response to the generated differential axial transport, the at least one target analyte contained in a sample reservoir in communication with the sample separation channel is selectively transported to the at least one ESI emitter while inhibiting transport of contaminant materials contained in the sample reservoir toward the at least one ESI emitter thereby preferentially directing analyte molecules out of the at least one ESI emitter. The methods, systems and devices are particularly suitable for use with a mass spectrometer.

Abstract: A flow cell for use in a microfluidic detection system. The flow cell includes a flow cell body having a channel that extends along the flow cell body. The flow cell body has a substrate material that extends along the channel and that is transparent to at least one of excitation light or light emissions. The channel has a functionalized channel surface that includes reactive groups configured to attach to molecules for biochemical analysis. The flow cell also includes fluidic inlet and fluidic outlet ports provided on the flow cell body and an electroosmotic (EO) pump held within the flow cell body in fluid communication with the channel. The EO pump is operable to induce flow of a solution from the inlet port to the outlet port and along the functionalized channel surface.

Abstract: In one aspect, the present invention provides a systems and methods for the real-time amplification and analysis of a sample of DNA.

Abstract: A convenient technique allows detecting fluorescence emitted in the channel with a uniformly high detection sensitivity and a good reproducibility. On the front face side of a plate-like body 11, a groove-shaped introduction channel 12 and separation channel 14 are formed. In this micro-channel chip 10, on the inner faces of a groove constituting the separation channel 14 formed in a surface of the plate-like body 11, there is formed a fine particle layer 20 provided by sintering fine particles having an average particle diameter of 10 to 500 nm mainly composed of zinc oxide (ZnO) or titanium oxide (TiO2).

Abstract: A process for analyzing a sample by a capillary electrophoresis method is provided that allows for high analytic precision and reduction in apparatus size, and can be readily carried out by electrophoresing a complex of a sample and an anionic group-containing compound in the capillary channel, wherein the capillary channel includes an A layer that is coated on an inner wall thereof and a B layer that is coated on the A layer, where the A and B layers are as described.

Abstract: An array of transportable particle sets is used in a microfluidic device for performing chemical reactions in the microfluidic device. The microfluidic device comprises a main channel and intersecting side channels, the main channel and side channels forming a plurality of intersections. The array of particle sets is disposed in the main channel, and the side channels are coupled to reagents. As the particle sets are transported through the intersections of the main channel and the side channels, reagents are flowed through the side channels into contact with each array member (or selected array members), thereby providing a plurality of chemical reactions in the microfluidic system.

Abstract: Provided is a device comprising an upper chamber, a middle chamber and a lower chamber, wherein the upper chamber is in communication with the middle chamber through a first pore, and the middle chamber is in communication with the lower chamber through a second pore, wherein the first pore and second pore are about 1 nm to about 100 nm in diameter, and are about 10 nm to about 1000 nm apart from each other, and wherein each of the chambers comprises an electrode for connecting to a power supply. Methods of using the device are also provided, in particular for sequencing a polynucleotide.

Abstract: The present invention provides a device and methods of use thereof for desalting a solution. The methods, inter-alia, make use of a device comprising microchannels, which are linked to conduits, whereby induction of an electric field in the conduit results in the formation of a space charge layer within the microchannel. The space charge layer provides an energy barrier for salt ions and generates an ion depletion zone proximal to the linkage region between the microchannel and the conduit. The method thus enables the removal of salt ions from the region proximal to the conduit and their accumulation in a region distant from the conduit, within the microchannel.

Abstract: A detection optics configuration for bio-analysis, in which the direction of incident radiation, the axis of the separation channel, and the direction of collection of the output radiation are coplanar at the detection zone. The detection configuration incorporates ball-end optical fibers to direct incident radiation at and collection of output radiation from the detection zone. The detection optics configuration may be implemented in an improved bio-separation instrument, in particular a capillary electrophoresis instrument.

Abstract: Disclosed herein is a composition of a separation medium and method of its use for electrophoresis in bare channels, either capillaries or chips, with suppressed electroosmotic flow, wherein various forms of boric acid are adsorbed on the wall of said separation channel, efficiently suppressing zeta potential of the wall of said bare channel. A composition of a sieving separation medium for electrophoresis of DNA is disclosed. A composition of a sieving separation medium for electrophoretic size separation of proteins by SDS CSE is also disclosed. A composition of a separation medium for capillary electrophoresis without sieving is also disclosed.

Abstract: A cartridge-based bio-separation system configured to utilize a pen shaped bio-separation cartridge that is easy to assemble and use with no moving parts and that has an integrated reagent (separation buffer) reservoir. The cartridge includes a body, defining an opening as a detection window for receiving external detection optics, at least one capillary column supported in the body, having a first end extending beyond a first end of the body, wherein the detection window exposes a section along the capillary column, to which the external optics are aligned through the detection window, and a reservoir attached to a second end of the body in fluid flow communication with a second end of the capillary column. The reservoir is structured to be coupled to an air pressure pump that pressurizes the gel reservoir to purge and fill the capillaries with buffer as the separation support medium.

Abstract: A microfluidic device for separating, fractionating, or preconcentrating analytes contained in an electrolyte having at least two reservoirs separated by at least one microchannel and/or nanochannel. At least part of the wall of the microchannel is made of and/or coated interiorly with a conducting and polarizable material or group of materials constituting a polarizable interface or a network of polarizable interfaces. In that at least one electrode or at least one electrode network is connected at at least one point of the polarizable material or group of materials, the surface electrical conductance of said material being equal to at least 100 nS.

Abstract: A microfluidic control apparatus operating method is disclosed. The microfluidic control apparatus operating method is applied in a microfluidic control apparatus, and the microfluidic control apparatus includes a photoconductive material layer and a flow passage. The microfluidic control apparatus operating method includes steps of (a) when a light with a specific optical pattern is emitted toward the photoconductive material layer, at least three virtual electrodes being formed on the photoconductive material layer according to the specific optical pattern; (b) when the specific optical pattern changes, the at least three virtual electrodes also changing to generate an electro-osmotic force to control a moving state of a microfluid in the flow passage.

Abstract: Devices and methods are provided for performing droplet-based solid phase processing steps on a digital microfluidic device. A solid phase material, which may be a porous solid phase material such as a porous polymer monolith is formed or located on a digital microfluidic element. The solid phase may be formed by an in-situ method in which the digital microfluidic array is actuated to transport a droplet of solid phase pre-cursor solution to a selected element on the array, and subsequently processed to form a solid phase on the array element. The integration of a solid phase material with a digital microfluidic array enables a wide range of applications including solid phase extraction and sample concentration.

Abstract: A system that incorporates the subject disclosure may include, for example, a method for generating an electric or pressure difference force that induces a plurality of particles to flow through a through-hole. Independently adjustable heat source in a vicinity of the through-hole induces a thermodynamic force for modifying the flow of the plurality of particles through the through-hole. Additional embodiments are disclosed.

Abstract: A nanoparticle translocation device includes a first reservoir having a first reservoir electrode, a second reservoir having a second reservoir electrode, and at least one nanopore providing fluid communication between the first and second reservoirs. The device also includes one or more inner electrode portions on an inner wall of the nanopore and one or more outer electrode portions disposed on an outer wall of the nanopore. The device further includes at least one DC voltage supply for selectively applying a DC voltage to each of the first reservoir electrode, the second reservoir electrode, and the outer electrode layer, where the inner electrode portions, the outer electrode portions, and the nanopore are in a substantially coaxial arrangement.

Abstract: Molecular adsorption to the microfluidic device surfaces can be passively and actively mitigated by mixing certain hydrophilic polymers (organic polymers with repeating hydrophilic groups—the preferred polymers being amphipathic surfactants—with the sample liquid during or prior to relevant microfluidic operations. Nonionic surfactants such as polyoxyethylene sorbitan monooleate and polyoxyethylene octyl phenyl ether are especially effective. High molecular weight polyethylene polymers are also effective. The hydrophilic polymers appear to prevent binding of the fouling molecules to the microfluidic by occupying the surface sites in place of the fouling molecules or by interacting with the fouling molecules to prevent binding of the fouling molecules the surface. When surface adsorption is thus mitigated, microfluidic devices can readily handle samples containing biomolecules to enable active sample concentration, filtering, washing, transport, mixing and other sample handling operations.

Abstract: This invention provides devices and apparatuses comprising the same and methods of use thereof for efficient pumping and/or mixing of relatively small volumes of fluid, wherein the fluid contains a sample within an inner fluid phase dispersed in an outer phase. Such devices utilize nonlinear electrokinetics as a primary mechanism for driving fluid flow and/or mixing the fluid. Methods of cellular analysis, drug delivery and others, utilizing the devices are described.

Abstract: A device for forming at least one circulating flow, or vortex, at the surface of a drop of liquid, including at least two first electrodes forming a plane and having edges facing each other, such that the contact line of a drop, deposited on the device and fixed relatively to the device, has a tangent forming, when projected onto the plane of the electrodes, an angle between 0° and 90° with the edges facing each other of the electrodes.

Abstract: Various embodiments provide an exemplary lab-on-a-chip (LOC) system that serves as an analytical tool and/or as a separation medium for an electrolyte solution including various charged molecular species. The LOC system can include an integrated nanofluidic FET device in combination with suitable analysis systems. By applying and controlling a longitudinal electric field and a transverse electric potential, the flow and the pH of the electrolyte solution in the nanofluidic channels can be controlled.

Abstract: A device for electrophoretic analysis of multicomponent solutions comprises a capillary and vials for electrolyte and sample solutions. The device comprises streaming potential measurement means implemented to measure a potential difference between capillary ends and to form an electric connections with said capillary ends during capillary rinsing in such a way that said streaming potential measurement means and electrolyte inside capillary and vials form a closed measurement electric circuit. A means for generation of electrolyte flow is implemented so as to build up and maintain a preset differential pressure between capillary ends and wherein that streaming potential measurement means comprises means to disconnect said measurement electric circuit during electrophoretic analysis.

Abstract: An electrophoresis apparatus is generally disclosed for sequentially analyzing a single sample or multiple samples having one or more analytes in high or low concentrations. The apparatus comprises a relatively large-bore transport capillary which intersects with a plurality of small-bore separation capillaries and includes a valve system. Analyte concentrators, having antibody-specific (or related affinity) chemistries, are stationed at the respective intersections of the transport capillary and separation capillaries to bind one or more analytes of interest. The apparatus allows the performance of two or more dimensions for the optimal separation of analytes. The apparatus may also include a plurality of valves surrounding each of the analyte concentrators to localize each of the concentrators to improve the binding of one or more analytes of interest.

Abstract: A microfluidic control apparatus and operating method thereof. The microfluidic control apparatus includes a photoconductive material layer and a flow passage. When a light with a specific optical pattern is emitted toward the photoconductive material layer, at least three virtual electrodes are formed on the photoconductive material layer according to the specific optical pattern. The at least three virtual electrodes include a first virtual electrode, a second virtual electrode and a third virtual electrode disposed beside the first virtual electrode. There is a specific proportion among a distance between first virtual electrode and third virtual electrode, a width of first virtual electrode, a distance between first virtual electrode and second virtual electrode, and a width of second virtual electrode. When the specific optical pattern changes, the at least three virtual electrodes also change to generate an electro-osmotic force to control the moving state of a microfluid in a flow passage.

Abstract: Methods and devices are described for concentration and cleanup of samples containing bio-molecule analytes (e.g., polynucleotides, such as DNA, RNA, PNA). Various embodiments provide for pH-mediated sample concentration and cleanup of nucleic acid samples with channel devices (e.g., cross-T format, microchannel devices).

Abstract: A method for collecting an analyte species from a sample is provided, the method of collection potentially being supplemented to give a method of preparing a sample for analysis and/or a method of analysis. The method including providing part of a sample in a substrate, causing the sample to migrate to an interface between the substrate and a second substrate due to the action of an electrical potential difference, the electrophoretic velocity of the analyte species of the second substrate being balanced by or exceeded by the bulk flow velocity of the second substrate and the bulk flow velocity of the second substrate being in an opposing direction to the electrophoretic velocity of the analyte species in the second substrate. In this way substantial concentration of the analyte species at the interface is provided. Subsequently the species can be conveyed away from the interface for further preparation and/or analysis.

Abstract: The invention is directed to the elimination of changes of the chemical composition of a pumped liquid caused by introduction of strange components or by modification of original components. Another object of the invention is to provide the possibility of use of electrodes of the first order in order to increase productivity and decrease size and cost of the micropump. For this purpose, the electrokinetic micropump comprises a multichannel structure 810 made of non-conducting material, for example, a piece of a polycapillary column. The inlet and outlet end of this structure are adjacent to electrode sections 803, 804 having openings 821, 822 for inlet and outlet of the pumped liquid. These sections are divided by ion-exchange membranes 811, 812 into chambers 813, 814 for flow of the pumped liquid, communicating with the ends 841, 842 of the multichannel structure, and chambers 815, 816 filled with an auxiliary medium for transfer of electric charges. In the latter electrodes 817, 818 are located.

Abstract: An electrophoresis apparatus is generally disclosed for sequentially analyzing a single sample or multiple samples having one or more analytes in high or low concentrations. The apparatus comprises a relatively large-bore transport capillary which intersects with a plurality of small-bore separation capillaries and includes a valve system. Analyte concentrators, having antibody-specific (or related affinity) chemistries, are stationed at the respective intersections of the transport capillary and separation capillaries to bind one or more analytes of interest. The apparatus allows the performance of two or more dimensions for the optimal separation of analytes. The apparatus may also include a plurality of valves surrounding each of the analyte concentrators to localize each of the concentrators to improve the binding of one or more analytes of interest.

Abstract: A method for modeling turbidite channels which may contain oil that it is desired to extract is provided in which the final shape of the complex resulting from migration of elementary channels over the course of deposition and which is observable from seismic data is combined with the implementation of simple geometric rules, comprising simulation of one or several intermediate channels passing through points on trajectories running from a final channel to an initial channel. The trajectories involved are different from the channel axes or lines; they reflect channel migration over time.

Abstract: The present invention provides a device and methods of use thereof for desalting a solution. The methods, inter-alia, make use of a device comprising microchannels, which are linked to conduits, whereby induction of an electric field in the conduit results in the formation of a space charge layer within the microchannel. The space charge layer provides an energy barrier for salt ions and generates an ion depletion zone proximal to the linkage region between the microchannel and the conduit. The method thus enables the removal of salt ions from the region proximal to the conduit and their accumulation in a region distant from the conduit, within the microchannel.

Abstract: The invention provides uncharged water-soluble silica-adsorbing polymers for suppressing electroendoosmotic flow and to reduce analyte-wall interactions in capillary electrophoresis. In one aspect of the invention, one or more of such polymers are employed as components of a separation medium for the separation of biomolecules, such as polynucleotides, polysaccharides, proteins, and the like, by capillary electrophoresis. Generally, such polymers are characterized by (i) water solubility over the temperature range between about 20° C. to about 50° C., (ii) concentration in a separation medium in the range between about 0.001% to about 10% (weight/volume), (iii) molecular weight in the range of about 5×103 to about 1×106 daltons, and (iv) absence of charged groups in an aqueous medium having pH in the range of about 6 to about 9.

Abstract: The invention is directed to a capillary tube for electrophoresis that has a positively charged coating on the capillary inner surface that prevents positively charged analytes from adsorbing to the inner capillary surface. The capillary tube has an inner surface that is coated with a first polymer layer having a plurality of polymer groups comprising polyethylene imine, designated herein as (CH2CH2NH)x. The inner surface of the capillary typically has a second polymer layer covalently bonded to the first polymer layer. The invention includes a capillary tube where two or more than two polymer groups are covalently bonded to each other by a cross-linker. Also provided are an electrophoresis system the uses the coated capillary tubes, a method of performing electrophoresis that utilizes the coated capillary tubes, and a process for preparing the coated capillary tubes.

Abstract: A device for forming at least one circulating flow, or vortex, at the surface of a drop of liquid, including at least two first electrodes forming a plane and having edges facing each other, such that the contact line of a drop, deposited on the device and fixed relatively to the device, has a tangent forming, when projected onto the plane of the electrodes, an angle between 0° and 90° with the edges facing each other of the electrodes.

Abstract: A method for separating the constituents of a mixture M by electrophoresis in a single capillary includes (A) separating compounds of the mixture M in a single capillary according to the capillary electrophoresis technique; (B) isolating a fraction F of the compounds thus separated by evacuating part of the compounds having the highest migration speeds from the capillary and/or evacuating part of the compounds having the lowest migration speeds from the capillary; (C) introducing a separating medium MS having a higher migration speed than the compounds of the isolated fraction F into the capillary containing the isolated fraction F, and (D) the compounds contained in fraction F are separated in the new electrophoretic conditions thus obtained.

Abstract: A separation module operates to fractionate or separate an analyte into fractions according to pI, i.e., pI bands, utilizing capillary isoelectric focusing (“CIEF”) within a first microchannel. The fractions are stacked to form plugs, the number of which is determined by a number of parallel second microchannels integrally connected to the first microchannel, into which the fractions are directed according to the buffer characteristics found in each of the individual microchannels. Within the microchannels the plugs are separated into proteins according to a different chemical property, i.e., “m/z,” utilizing capillary electrophoresis (“CE”).

Abstract: A microchip for capillary electrophoresis is provided. The microchip comprises an injection channel and a separation channel configured to receive a sample through a sample well disposed on a first end of the separation channel; wherein the injection channel and the separation channel intersect to form a ‘T’ junction. The microchip further comprises a first valve disposed adjacent to the ‘T’ junction and on the separation channel and a second valve disposed at the ‘T’ junction. The second valve is a two-way valve. A sample plug is injected into an area between the ‘T’ junction and a second end of the separation channel.

Abstract: A microfluidic device for carrying a liquid, the device comprising a microfluidic channel having an interior wall and a polyelectrolyte film on the interior wall whereby liquid carried by the channel contacts the polyelectrolyte film, the polyelectrolyte film having a thickness of about 1 to about 1000 nanometers and comprising an interpenetrating network of a predominantly positively charged polymer and a predominantly negatively charged polymer, the predominantly positively charged polymer, the predominantly negatively charged polymer or both containing (i) a pH insensitive positively or negatively charged repeat unit having a pKa greater than 9 or less than 3, and (ii) a pH sensitive repeat unit, the pH sensitive repeat unit having a pKa of 3 to 9, whereby the pH of liquid in the microfluidic channel may be used to control the velocity or direction of electroosmotic flow of the liquid within said microfluidic channel.

Abstract: To suppress temperature variations of sample fluids within flow channels for electrophoresis, in a method for controlling temperatures within micro flow channels. When controlling the temperatures of sample fluids within micro flow channels of electrophoresis chips, in which flow channels through which electrophoresis occurs by application of electrical potential differences can be switched, temperature variations of the sample fluids within the micro flow channels, caused by differences in heat generated by the sample fluids prior to and following the switching of the flow channels, are predicted. Control properties for temperature control in order to cancel the temperature variations are changed during the switching of the flow channels.

Abstract: A fluidic device, the fluidic device comprising a planar fluidic conduit for conducting a fluid, wherein the fluidic conduit has a plurality of fluidic disturbance features located along at least a section of the fluidic conduit for disturbing a laminar flow of the fluid along the section.

Abstract: A flow controller which uses a combination of hydrostatic pressure and electroosmotic flow to control the flow of a fluid. A driving fluid (1204) whose flow rate is dependent on both hydrostatic pressures and electroosmotic flow can be used (a) directly as a working fluid in an operable device, for example a chromatograph, or (b) to displace a working fluid (1203) from a storage container (625) into an operable device (1301), or both (a) and (b). The driving fluid (1204) can be composed of one or more fluids. Part or all the driving fluid (1204) is passed through an electroosmotic device (100) so as to increase or decrease the flow rate induced by hydrostatic pressure.