Abstract: The invention concerns a method for determining Clausius-Mossotti Factors ‘CMF’ of a solution of colloidal particles, comprising the following steps: putting said solution of colloidal particles (1) in contact with at least a pair of coplanar electrodes (3a, 3b) arranged on a substrate (5); placing colloidal particles in specific locations with reference to said electrodes; applying an AC electric field with an adapted dielectrophoretic ‘DEP’ frequency between each pair of electrodes, so that the colloidal particles move away from said specific locations by DEP forces, the motion of the colloidal particles being dictated by a DEP regime; determining velocities of the moving colloidal particles during the DEP regime, said velocities being determined along the electric field gradient direction; and calculating the CMF of said colloidal particles by using said velocities.

Abstract: The device comprises first and second contact pads having a contact surface. The first and second contact pads move with respect to one another between an ohmic contact position between these contact surfaces and another position. The device further comprises means for applying a non-uniform electric field around the first contact pad. The electric field has a component in a direction parallel to the contact surface of the first contact pad. A fluid with a first dielectric permittivity value is arranged between the first contact pad and the decontamination electrode. The decontamination device and the fluid are configured in such a way that the electric field generates a force directed towards the decontamination electrode on a contaminant, by dielectrophoresis.

Abstract: A dielectrophoresis apparatus for separating particles from a sample, including an apparatus body; a dielectrophoresis channel in the apparatus body, the dielectrophoresis channel having a central axis, a bottom, a top, a first side, and a second side; a first mesa projecting into the dielectrophoresis channel from the bottom and extending from the first side across the dielectrophoresis channel to the second side, the first mesa extending at an angle to the central axis of the dielectrophoresis channel; a first electrode extending along the first mesa; a second mesa projecting into the dielectrophoresis channel from the bottom and extending from the first side across the dielectrophoresis channel to the second side, the second mesa extending at an angle to the central axis of the dielectrophoresis channel; a space between at least one of the first electrode and the second side or the second electrode and the second side; and a gap between the first electrode and the second electrode.

Abstract: A device for dielectrophoretic manipulation of suspended particulate matter comprises an analysis electrode and a separate cover electrode wherein the analysis electrode comprises an electrically conductive layer of material provided on a substrate support and apertures are defined through the electrically conductive layer. The device can be used for detection, analysis, fractionation, concentration or separation of particulate matter.

Abstract: A three-dimensional nanochannel device and a method of manufacturing the same are provided. In the device, a first substrate, a second substrate, and a channel layer sandwiched by the first and the second substrates are included. At least one channel is constituted by the first and the second substrates and the channel layer and includes a fluid inlet, a fluid outlet, and at least one condensed channel between the fluid inlet and the fluid outlet. The condensed channel at least has a first size and a second size on an X-Y plane and has a third size and a fourth size on an X-Z plane. A difference between the first size and the second size is about at least two orders in scale, and a difference between the third size and the fourth size is about at least two orders in scale.

Abstract: Electrowetting devices coated with one or more polymeric layers and methods of making and using thereof are described herein. The coatings may be formed in a single layer or as multiple layers. In one embodiment the first layer deposited serves as an insulating layer of high dielectric strength while the second layer deposited serves as a hydrophobic layer of low surface energy. These materials may themselves be deposited as multiple layers to eliminate pinhole defects and maximize device yield. In one embodiment the insulating layer would be a vapor deposited silicone polymeric material including, but not limited to, polytrivinyltrimethylcyclotrisiloxane or polyHVDS. In another embodiment the insulating layer may be a vapor deposited ceramic such as SiO2 with very little carbon content. In a further embodiment the insulating layer may be composed of alternating layers of a siloxane material and a ceramic material.

Abstract: Methods are provided for manipulating droplets. The methods include providing the droplet on a surface comprising an array of electrodes and a substantially co-planer array of reference elements, wherein the droplet is disposed on a first one of the electrodes, and the droplet at least partially overlaps a second one of the electrodes and an intervening one of the reference elements disposed between the first and second electrodes. The methods further include activating the first and second electrodes to spread at least a portion of the droplet across the second electrode and deactivating the first electrode to move the droplet from the first electrode to the second electrode.

Abstract: The present invention provides a device and methods of use thereof in microscale cell sorting. This invention provides sorting cytometers, which trap individual cells within vessels following exposure to dielectrophoresis, allow for the assaying of trapped cells, such that a population is identified whose isolation is desired, and their isolation.

Abstract: A droplet can be moved along a surface of a moving surface forming member in a simple method. At both sides of the moving surface forming member 1 configured to form a moving surface on which the droplet is moved and made of a nonmagnetic material, magnetic field forming members 4A and 4B configured to form a magnetic field gradient such that intensity of a magnetic field decreases as a distance from an area where the droplet is positioned on the surface of the moving surface forming member 1 increases along the surface is provided. By relatively moving the moving surface forming member 1 with respect to the magnetic field forming members 4A and 4B along the surface, the droplet is moved along the magnetic field gradient.

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 device for producing at least one of fluid flows and particles flows includes a substrate having a substrate surface. The substrate surface includes a matrix including a plurality of regions having at least one of a different magnitude of a surface charge, a different sign of the surface charge, and a different height above the substrate. A fluid including at least partially electrically charged particles is disposed at the substrate surface. A first control element is configured to supply a plurality of electrical voltages to a plurality of electrode pairs. The electric field exerts a first force on a component of the fluid within an electrical double layer. The component is disposed adjacent to the substrate surface. The electric field exerts a second force within the double layer and outside the double layer, the second force is exerted on the at least partially electrically charged particles.

Abstract: Systems, devices, and methods are presented that facilitate electronic manipulation and detection of submicron particles. Time-multiplexed dielectrophoresis can be employed by cycling between two or more disparate electric fields during separate portions of a duty cycle. By cycling between these two or more disparate electric fields, two or more disparate particle types can be separated from one another based on differences in electrical properties of the two or more disparate particle types.

Abstract: A biological sample immobilizing apparatus is provided, comprising a holding unit which holds a biological sample, a pair of electrodes which allows a dielectrophoretic force to act on the biological sample to move the biological sample to the holding unit, and a power source which applies an AC voltage to the pair of electrodes. Accordingly, a plurality of components contained in the biological sample can be conveniently separated into individuals one by one and respective genes thereof can be analyzed one by one quickly and simultaneously, while providing a high density and being miniaturized.

Abstract: Systems and methods for trapping and moving individual particles of a target material of a suspension are disclosed. In one aspect, a system includes a tube and an electronically addressable float. The float includes one or more arrays of electrodes in which each electrode can be independently addressed to create non-uniform electric fields that trap and isolate target particles near the float. The electrodes can be dynamically operated to move the target particles to particular locations on the float for analysis and collection.

Abstract: A fluid structure control device has a liquid chamber holding a solution containing an electrolyte dissolved therein and conductive particles dispersed in the solution, and a pair of electrodes for applying an AC voltage to the conductive particles in the liquid chamber. Electro-osmotic flows are caused to occur due to electric double layers induced at the interface between the solution and the conductive particles by application of a voltage, thereby producing interaction among the conductive particles to displace the conductive particles and change reversibly the dispersion state of the conductive particles in accordance with the applied voltage.

Abstract: A microfabricated particle focusing device comprises an acoustic portion to preconcentrate particles over large spatial dimensions into particle streams and a dielectrophoretic portion for finer particle focusing into single-file columns. The device can be used for high throughput assays for which it is necessary to isolate and investigate small bundles of particles and single particles.

Abstract: Provided are a device for varying wetting properties and a device for separating particles using the same. The magnitude and switching period of a voltage applied to a droplet are changed to separate particles contained in the droplet based on mass or size. The device for varying wetting properties includes an electrode layer that is electrically conductive with one of different electrical polarities, an insulating layer disposed at one side of the electrode layer, and a droplet that is in contact with the other polarity and contains different particles desired to be separated. Wetting properties of the droplet are varied according to application of a voltage.

Abstract: A microfluidic separation device is provided that includes a sample channel having a first sample channel region and a second sample channel region, where a cross-section of the first sample channel region is smaller than a cross-section of the second sample channel region. The invention further includes a detection region having a first detection region and a second detection region, where a cross-section of the first detection region is larger than a cross-section of the second detection region and the second sample channel region is connected to the first detection region. Additionally, the invention includes a marker input channel disposed to input markers into the second sample channel region, where the markers are larger than the cross-section of the first sample channel region and the cross-section of the second detection region, where the markers collect in the first detection region.

Abstract: Apparatus and methods are provided for liquid manipulation utilizing electrostatic field force. The apparatus is a single-sided electrode design in which all conductive elements are embedded on the first surface on which droplets are manipulated. An additional second surface can be provided parallel with the first surface for the purpose of containing the droplets to be manipulated. By performing electrowetting based techniques in which different electrical potential values are applied to different electrodes embedded in the first surface in a controlled manner, the apparatus enables a number of droplet manipulation processes, including sampling a continuous liquid flow by forming individually controllable droplets from the flow, moving a droplet, merging and mixing two or more droplets together, splitting a droplet into two or more droplets, iterative binary mixing of droplets to obtain a desired mixing ratio, and enhancing liquid mixing within a droplet.

Abstract: A device for manipulating magnetic or magnetizable objects in a medium is provided. The device has a surface lying in a plane and comprises a set of at least two conductors electrically isolated from each other, wherein the at least two conductors are adapted for both generating a magnetophoresis force for moving the magnetic or magnetizable objects over the surface of the device in a direction substantially parallel to the plane of the surface, and generating a dielectrophoresis force for moving the magnetic or magnetizable objects in a direction substantially perpendicular to the plane of the surface. Also provided is a method for manipulating magnetic or magnetizable objects in a medium. The method uses a combined magnetophoresis and dielectrophoresis actuation principle for controlling in-plane as well as out-of-plane movement of the magnetic or magnetizable objects.

Abstract: Sensing device and sensing method are disclosed. The multi-dimensional force sensing device includes a soft laminose dielectric structure, a conductive sheet, at least one first electrode sheet, at least one second electrode sheet, a measuring unit and an analysis unit. The soft laminose dielectric structure has a first surface and a second surface opposite to each other. The conductive sheet is disposed on the first surface and has a vertical projection area. The first electrode sheet is disposed on the second surface and totally in the range of the vertical projection area. The second electrode sheet is disposed on the second surface and partially in the range of the vertical projection area. The analysis unit analyzes the magnitude and direction of a force applied on the conductive sheet according to the capacitance between the at least one first electrode sheet and between the first and the second electrode sheets.

Abstract: The invention pertains to a method and apparatus to separate and quantify particles using time-variable force fields. The force fields can be for dielectrophoresis (positive or negative), electrophoresis, or electrohydrodynamic. In one aspect, the fields are translated and/or modified in space at a speed substantially comparable to the speed of translation of the fastest particles in the sample. The translation and/or modification of the force fields can also occur with varying speed. In another aspect, the field is translated and/or modified in a first direction at high speed. In another aspect, the quantity or size of the particles is determined by an indirect measurement of the speed of movement after varying the force field by means of a relationship between the speed of movement and the volume of the particles. This invention also pertains to an apparatus to produce appropriate field configurations necessary for the selective movement of particles.

Abstract: Methods and related devices are illustrated for generating time-variable electric fields suitable for determining the creation of closed dielectrophoretic cages able to trap inside even single particles without the cages being necessarily positioned at relative minimum points of the electric field.

Abstract: A device for manipulating magnetic or magnetizable objects in a medium is provided. The device has a surface lying in a plane and comprises a set of at least two conductors electrically isolated from each other, wherein the at least two conductors are adapted for both generating a magnetophoresis force for moving the magnetic or magnetizable objects over the surface of the device in a direction substantially parallel to the plane of the surface, and generating a dielectrophoresis force for moving the magnetic or magnetizable objects in a direction substantially perpendicular to the plane of the surface. Also provided is a method for manipulating magnetic or magnetizable objects in a medium. The method uses a combined magnetophoresis and dielectrophoresis actuation principle for controlling in-plane as well as out-of-plane movement of the magnetic or magnetizable objects.

Abstract: The high throughput particle separation system includes an aqueous solution container for storing an aqueous solution containing specific particles to be separated, an electrode array, having a plurality of electrodes arranged at regular intervals or at various different intervals in series or in parallel, for deflecting specific particles simultaneously in a nonuniform electric field according to sizes and dielectric properties of the particles to separate a large quantity of the particles at high throughput, a path separation unit for establishing movement paths of the particles separated by the electrode array, and a control unit for applying the same voltage and frequency or different voltages and frequencies to the electrodes of the electrode array based on sizes and dielectric properties of specific particles to be separated.

Abstract: Methods, devices, and systems for separating disparate liquid-suspended particles in a flow channel using dielectrophoresis induced by concave-shaped electrodes and field-flow fractionation.

Abstract: Examples of the present invention include methods of assembling structures, such as nanostructures, at predetermined locations on a substrate. A voltage between spaced-apart electrodes supported by substrate attracts the structures to the substrate, and positional registration can be provided the substrate using topographic features such as wells. Examples of the present invention also include devices, such as electronic and optoelectronic devices, prepared by such methods.

Abstract: The present teachings relate to systems and methods for separation of substances such as cells, nucleic acids, and carbon nanotubes. The substances are combined with a separation medium in a liquid sample cavity, for example a microchannel, and transit through the separation by optically activated dielectrophoretic forces. The substances are advantageously labeled and visualized using a microscope and camera.

Abstract: A device for electrophoresis applies a voltage to a medium in contact with a plurality of electric conductors so that a potential of adjacent conductors is within a certain range. This allows preventing decline in electrophoresis speed. A device for electrophoresis and transfer includes an electrode having a plurality of electrode regions being insulated one another and arranged in a specific direction. This allows providing a practical and easy-to-use device for electrophoresis and transfer. A device for transfer alters an applied voltage or applied voltage duration to a certain position to another position. This allows improving transfer efficiency.

Abstract: Disclosed are a method and apparatus that use an electric field for improved biological assays. The electric field is applied across a device having wells, which receive reactants, which carry a charge. The device thus uses a controllable voltage source between the first and second electrodes, which is controllable to provide a positive charge and a negative charge to a given electrode. By controlled use of the electric field charged species in a fluid in a fluid channel are directed into or out of the well by an electric field between the electrodes. The present method involves the transport of fluids, as in a microfluidic device, and the electric field-induced movement of reactive species according to various assay procedures, such as DNA sequencing, synthesis or the like.

Abstract: An apparatus for controlling flow of ER fluid. The apparatus has a first channel 10 for conveying carrier fluid 1 of a first dielectric constant and droplets 2 of a second dielectric constant in the carrier fluid. The apparatus further comprises a second channel 20 conveying the ER fluid and a first conductor 100 for conveying an electrical potential from the second channel to the first channel. A circuit 61 is provided for applying potential difference between the first and second channels. When a droplet is present in the first channel, the ER fluid is solidified in the second channel; when no droplet is present, the ER fluid flows as liquid in the second channel. Therefore the apparatus acts as an IF gate. Arrangements for other types of fluidic logic gate are also disclosed.

Abstract: The present invention relates to an apparatus and method for manipulation and/or position control of particles by means of force fields of electrical nature in electrically conductive solutions, wherein power dissipated by Joule effect, which may cause the death of biological specimens under examination, is advantageously removed. The apparatus comprises a first substrate, upon which lies an array of electrodes, the application of a set of electric voltages to the electrodes generating a force field; a second substrate at a distance from, and parallel to, the first substrate so as to delimit a microchamber within which a liquid containing the particles is inserted; and cooling means for extracting an appropriate amount of heat from the microchamber, the cooling means comprising a second microchamber made in contact with, or by means of, the first or second substrate and through which a flow of cooling liquid or gas is pumped.

Abstract: An optically-induced dielectrophoresis chip including a substrate, a first electrode layer disposed on the substrate, and an interface modification layer disposed on the first electrode layer. A photo-conductive layer is disposed on the interface modification layer and includes an optical absorbent polymeric material. A barrier layer is disposed on the photo-conductive layer, and a compartment forming layer is disposed on the barrier layer defining a compartment. A second electrode layer covers the compartment forming layer.

Abstract: Particle separation apparatus separate particles and particle populations using dielectrophoretic (DEP) forces generated by one or more pairs of electrically coupled electrodes separated by a gap. Particles suspended in a fluid are separated by DEP forces generated by the at least one electrode pair at the gap as they travel over a separation zone comprising the electrode pair. Selected particles are deflected relative to the flow of incoming particles by DEP forces that are affected by controlling applied potential, gap width, and the angle linear gaps with respect to fluid flow. The gap between an electrode pair may be a single, linear gap of constant gap, a single linear gap having variable width, or a be in the form of two or more linear gaps having constant or variable gap width having different angles with respect to one another and to the flow.

Abstract: A process and a device for retaining polarizable target-particles from a fluid suspension of polarizable target-particles comprising the steps of pumping that suspension into a vertical or inclined channel and applying an alternating electric field inducing a negative dielectrophoretic force on the target-particles, the force being sufficient to push them a distance of at least or about 25 m from the surface of an electrode-bearing wall, thereby creating an upward-moving clarified fluid zone in the vicinity of that wall and a downward-moving target-particle containing fluid zone at a distance from that wall.

Abstract: A liquid transporting device using electrowetting on dielectric technique is provided. A sampling liquid is accurately transported on a substrate in a channel-free manner. The sampling liquid is spun off the substrate by a centrifugal force after the sampling liquid has been detected. The liquid transporting device can be applied to a biochemical detecting apparatus and a biochemical detecting method, thereby fulfilling requirements of accurate sample transportation in the biomedical field. The liquid transporting device is simplified to reduce overall costs, thus being helpful for decreasing high prices of biomedical detecting systems.

Abstract: Methods and devices for the separation of particles (20, 21, 22) in a compartment (30) of a fluidic microsystem (100) are described, in which the movement of a liquid (10) in which particles (20, 21, 22) are suspended with a predetermined direction of flow through the compartment (30), and the generation of a deflecting potential in which at least a part of the particles (20, 21, 22) is moved relative to the liquid in a direction of deflection are envisaged, whereby further at least one focusing potential is generated, so that at least a part of the particles is moved opposite to the direction of deflection relative to the liquid by dielectrophoresis under the effect of high-frequency electrical fields, and guiding of particles with different electrical, magnetic or geometric properties into different flow areas (11, 12) in the liquid takes place.

Abstract: A monolithic fabrication method of parallel-plate electrowetting-on-dielectric (EWOD) chips for digital microfluidics of picoliter droplets is disclosed. Instead of assembling a second substrate to form a top plate, the top plate is generated in situ as a thin-film membrane that forms a monolithic cavity having a gap height on the order of micrometers with excellent accuracy and uniformity. The membrane is embedded with EWOD driving electrodes and confines droplets against the device substrate to perform digital microfluidic operations. Two main attributes of the monolithic architecture that distinguish it from tradition methods are: (i) it enables excellent control of droplet dimensions down to the micrometer scale, and (ii) it does not require the typical alignment and assembly steps of the two plates.

Abstract: A distribution of AC electric field regularly arranged in a cell is formed while storing a sample having particles dispersed in a medium in the cell, whereby the particles are dielectrically migrated in the medium to generate a diffraction grating by density distribution of the particles. Diffracted light generated by irradiating the diffraction grating by density distribution with measuring light is detected, and evaluation of dielectrophoretic intensities of the particles and/or the medium is performed from the detection result. According to this method, evaluation of dielectrophoretic characteristics can be performed without adhering a phosphor to particles, and since even a particle small in size can achieve a detection level by collecting a number of such particles to form a diffraction grating, dielectric characteristics of microparticles of several nanometers in diameter can be thus quantitatively measured with high sensitivity.

Abstract: This paper presents a microfluidic pumping approach using traveling-wave dielectrophoresis (tw-DEP) of microparticles. Flow is generated directly in the microfluidic devices by inducing electromechanical effects in the fluid using microelectrodes. The fluidic driving mechanisms due to the particle-fluid and particle-particle interactions under twDEP are analyzed, and the induced flow field is obtained from numerical simulations. Experimental measurements of the flow velocity in a prototype DEP micropumping device show satisfactory agreement with the numerical predications.

Abstract: A cell sorting apparatus includes a flow channel through which fluid including cells flows, an electric-field application section capable of applying an electric field having a gradient in a direction different from the flowing direction of the fluid at a first position on the flow channel in accordance with a cell sorting signal requesting an operation to sort the cells, and a flow splitting section configured to split the cells changing their flowing directions due to a dielectrophoretic force caused by application of the electric field at a second position on the downstream side of the first position on the flow channel.

Abstract: A fluid-application mechanism is to cause fluid to be applied onto media. An electrowetting mechanism is to generate an electric field to affect the fluid applied onto the media.

Abstract: A method is provided for classifying nanoobjects having different electrical properties, such as conductivities and permittivities. The method includes: suspending nanoobjects having different electrical properties in a liquid medium; passing the liquid medium through a microchamber; and filtering nanoobjects having a first type of electrical property from the liquid medium by applying an electric field to the liquid medium in the microchamber.

Abstract: The present invention is directed to the use of dielectrophoretic forces for the arbitrary manipulation of micrometer- and nanometer-sized particles and to devices capable of arbitrarily manipulating micrometer- and nanometer-sized particles by means of dielectrophoretic forces within a two- or three-dimensional region. The devices and methods of the invention are capable of arbitrarily controlling the velocities, locations, and forces applied to a particle, arbitrarily specifying a force or set of forces at a location in space, and determining friction and/or drag coefficients of a particle, and are thus well-suited for a range of applications including cell sorting, drug delivery, as a diagnostic tool for determining membrane stiffness, and in the heterogeneous integration of micro- and nano-components through directed assembly.

Abstract: Systems and methods for combining dielectrophoresis, magnetic forces, and hydrodynamic forces to manipulate particles in channels formed on top of an electrode substrate are discussed. A magnet placed in contact under the electrode substrate while particles are flowing within the channel above the electrode substrate allows these three forces to be balanced when the system is in operation. An optical detection scheme using near-confocal microscopy for simultaneously detecting two wavelengths of light emitted from the flowing particles is also discussed.

Abstract: The invention provides droplet actuators with droplet operations surfaces for manipulating droplets, e.g., by conducting droplet operations. The droplet operations surfaces are typically exposed to a droplet operations gap. One or more regions of a droplet operation surface may include patterned topographic features. The invention also provides a droplet actuator in which one or both gap-facing droplet operations surfaces is formed using a removable film. The removable film may, in various embodiments, also include other components ordinarily associated with the droplet actuator substrate, such as the dielectric layer and the electrodes. Further, the invention provides droplet actuator devices and methods for coupling and/or sealing substrates of a droplet actuator, such as techniques for self-aligning assembly of droplet actuator substrates.

Abstract: A microfluidic system for creating encapsulated droplets whose shells can be further removed comprises: two electrode plates and a spacing structure disposed between the two electrode plates. One of the electrode plates has three reservoir electrodes and a plurality of channel electrodes. The three electrodes are respectively used for accommodating a shell liquid, a core liquid, and a removing liquid which is able to remove the shell liquid. The channel electrodes are used for communicating droplets among the three reservoir electrodes. Via these arrangements, the microfluidic system can create a quantitative shell droplet and a quantitative core droplet, and then merge the shell and core droplets to form an encapsulated droplet. Moreover, the shell of the encapsulated droplet can be removed by mixing it with the removing liquid. This invention is further provided with a method for creating an encapsulated droplet with a removable shell.

Abstract: A novel electrowetting system for the smooth continuous movement of a droplet across a single circuit using a continuous applied voltage regardless of polarity. The actuation of the droplet is achieved by introducing a diode into the idealized electrical circuit of the electrowetting system. The diode is in parallel with a capacitor (dielectric) and effectively shorts the droplet on the side of a lower potential electrode so that the entire voltage drop is across the dielectric over the opposite electrode. This creates an energy imbalance that moves the droplet towards the higher potential. If the voltage polarity is reversed, the direction of actuation will reverse as well.

Abstract: Systems, devices, and methods are presented that facilitate electronic manipulation and detection of submicron particles. A particle manipulation device contains a plurality of electrodes formed on an active semiconductor layer of an integrated circuit chip, where the electrodes and gap spacing between adjacent electrodes is submicron in size. The chip is oriented with its substrate face up, and at least a portion of the substrate is removed from the chip so the electrodes are in close proximity to a fluid chamber(s) placed over the chip, to facilitate manipulation of particles, contained in a buffer solution in the fluid chamber(s), to form a defined pattern. Innovative macro-scale optical detection is employed to detect the submicron particles, where a light beam is applied to the defined pattern, and interaction of the defined pattern with the light beam is detected and evaluated to facilitate detecting the particles.

Abstract: Disclosed are a method and apparatus that use an electric field for improved biological assays. The electric field is applied across a device having wells, which receive reactants, which carry a charge. The device thus uses a controllable voltage source between the first and second electrodes, which is controllable to provide a positive charge and a negative charge to a given electrode. By controlled use of the electric field charged species in a fluid in a fluid channel are directed into or out of the well by an electric field between the electrodes. The present method involves the transport of fluids, as in a microfluidic device, and the electric field-induced movement of reactive species according to various assay procedures, such as DNA sequencing, synthesis or the like.