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    • 专利摘要:
    ABSTRACT Microfluidic device A device (100) for controlling a flow of a fluid is disclosed. The devicecomprises a first electrode (110) and a second electrode (120) offset from thefirst electrode in a downstream direction of the flow. The electrodes areconnectable to a voltage source. The first electrode comprises bridges (111)and joints (112)forming a grid structure which is arranged to allow the fluid toflow through the first electrode. At least a portion of at least one of the bridgeshas a maximum height (h1) in a direction parallel to the direction of the flowand a maximum gauge (w1) in a direction orthogonal to the direction of theflow, wherein said maximum height is larger than said maximum gauge so asto improve the pumping efficiency of the device. A method for manufacturingthe device, and a method for controlling a fluid flow by means of such device,is also disclosed. Figure elected for publication with abstract: 4a
    公开号:SE1351440A1
    申请号:SE1351440
    申请日:2013-12-04
    公开日:2015-06-05
    发明作者:Robert Thorslund；Are Björneklett；Peter Nilsson
    申请人:Apr Technologies Ab；
    IPC主号:
    专利说明:

    MICROFLUIDIC DEVICEField of the inventionThe invention disclosed herein relates to devices for transporting fluids.More precisely, it relates to an electro-hydrodynamic device for controlling afluid flow, as well as methods for manufacturing and controlling such device.
    Backqround of the inventionThe performance of electronic systems is to a large extent limited bythe available cooling techniques for keeping the electronics within anappropriate temperature range. Smaller electronic devices having improvedperformance are associated with increased heat dissipation over a relativelysmall area. ln other words, there is a growing need for space and energyefficient cooling of electronic devices.
    As an example, satellites, such as telecommunication satellites, areapproaching the technology limits of existing on-board thermal managementsystems. The power dissipation of these satellites increases to meet thegrowing requirements for broadcasting, broadband multimedia and mobilecommunications services. Micro, nano, or 'cube' satellites, which require low-mass heat removal from electronic components (satellite on a chip) are likelyto need more compact thermal management systems for maintaining a highperformance.
    Cooling is also a crucial factor in the design of other electronic deviceshaving heat-generating components, such as power electronics, powerfulprocessors, radio frequency amplifiers, lasers etc.
    Bologa et al., ”Multistage electrohydrodynamical pump", proceedings ofthe 2000 Conference on Electrical lnsulation and Dielectric Phenomena,discloses a multistage electrohydrodynamical (EHD) pump with latticedelectrodes of parallel wires embedded in a metal ring. According to Bologa etal., a formation of ions in a working medium, comprising a dielectric liquid,occurs at the emitter electrode, whereas the ions recombine at the collector.
    The ions move under the influence of Coulomb forces, which ions therebyentrain a flow of the working medium.
    Even though such EHD pump may be employed in various coolingapplications, there is still a need for an improved device and method forcontrolling the flow of a fluid and for providing improved pumping efficiency.There is also a need for an improved manufacturing method of such devices.
    Summarv of the inventionlt is an object of the present invention to control the flow of a fluid insuch manner that the efficiency of the transportation of the fluid is improved. ltis a particular object to improve the capacity of an EHD pump for dielectricfluids.
    Accordingly, the invention provides a device and a control method withthe features of the independent claims. The dependent claims defineadvantageous embodiments.ln a first aspect, the device is characterised in a first electrode and asecond electrode, wherein the second electrode is offset from the firstelectrode in a downstream direction of the flow and wherein the electrodesare connectable to a voltage source. The first electrode comprises bridgesand joints forming a grid structure, which is arranged to allow the fluid to flowthere through. According to this aspect, at least a portion of at least one of thebridges has a maximum height in a direction parallel to the direction of theflow, and a maximum gauge in a direction orthogonal to the direction of theflow, wherein the maximum height is larger than the maximum gauge,preferably at least twice the maximum gauge. The maximum height may alsobe three, four, five, or six times the maximum gauge, or larger.ln a second aspect, a pump assembly comprising a plurality of stackeddevices according to the first aspect is provided.ln a third aspect, the method for controlling the flow of a fluid ischaracterised in that a first electrode is provided, which comprises bridgesand joints forming a grid structure arranged to allow the fluid to flow throughthe first electrode. At least a portion of at least one of the bridges has amaximum height in a direction parallel to the direction of the flow and amaximum gauge in a direction orthogonal to the direction of the flow, andwherein said maximum height is larger than the maximum gauge, preferablyat least twice the maximum gauge. The maximum height may also be three,four, five, or six times the maximum gauge, or larger. Further, a secondelectrode is arranged offset from the first electrode in the direction of the flow,and an electric potential difference is applied to the first electrode and thesecond electrode so as to cause the fluid to flow through the first electrode.ln a fourth aspect, a method for controlling the flow of a fluid isprovided. The method comprises providing a device according to the firstaspect, providing a fluid contacting the first electrode of the device, andapplying an electric potential difference between the first electrode and thesecond electrode.
    By a grid it is understood any structure comprising bridges that arejoined to each other so as to e.g. a grating, net, or honeycomb structure, etc.The bridges and the joints define open areas of the grid which admit a fluidflow. Further, it is understood that the grid may comprise several bridgeshaving the above specified ratio between their height and gauge. As anexample, the whole grid other than its peripheral portions may e.g. be formedof such bridges. ln another example, most of or all of bridges of the grid mayfulfill the maximum height/gauge relation.
    Several advantages are associated with the invention. Firstly, byforming a grid of bridges that have a relatively large height in relation to theirgauge, the grid may be relatively rigid in terms of its ability to carry loads inthe height direction of the bridges, or the direction of the flow. Thereby, arelatively rigid electrode is enabled, which is less prone to bend or deform,especially in the direction of the flow, and hence the risk for e.g. short-circuiting of the device may be reduced. Further, the relatively rigid and stablegrid may still have a relatively large open area which may provide a relativelylow flow resistance being met by the fluid passing through the grid. Further,the relatively high and narrow bridges may reduce the amount of materialrequired for forming a relatively stable and rigid grid, which may reduce bothweight and cost of the device. By using a relatively rigid grid, the need foradditional support structures may be reduced and a relatively well definedand constant spacing between the first and second electrodes may beachieved. The spacing may e.g. be within the range of 10-2000 um, and morepreferably in the range of 50-1000 um.
    With their relatively large height, the bridges also provide a relativelylarge contact surface between the grid structure and the passing fluid, whichmay facilitate any interactions between the electrode and the fluid, such ase.g. diffusion of material and/or injection of ions or electrons.
    The distance, or spacing, between the first and the second electrodemay be varied so as to control the strength of the electric field being inducedbetween the electrodes. Experiments have shown that a smaller gap, andthus a stronger induced electric field, may enable increased pump efficiency,or flow rate, as compared to devices having a larger gap and being suppliedwith the same electric power.
    According to an embodiment, at least one of the bridges of the firstelectrode comprises a tapered portion forming an edge or tip that is directedtowards the second electrode. The present embodiment is based on theinsight that by providing the first electrode with beaked or pointed portions,the injection of electrons per unit area of the first electrode into the fluid maybe improved. lncreasing the emitting of electrons may enhance theelectrohydrodynamic effect, increase the flow through the device, and thusimprove its pumping efficiency. Further, increasing the electron emittingefficiency from the first electrode may advantageously allow for a reduction ofthe flow resistance through the grid, since the open area of the grid, i.e. thegrid area through which the fluid may pass, may be reduced withoutnecessarily reducing the injected current.
    According to an embodiment, at least one of the bridges comprises atapered portion forming an edge or tip directed away from the secondelectrode. ln other words, the tapered portion is directed anti-parallel to theflow of the fluid, which advantageously may streamline the upstream portionof the grid so as to reduce the flow resistance and enhance the efficiency ofthe device.
    According to an embodiment, the second electrode comprises bridgesand joints forming a grid structure that allows the fluid to flow through thesecond electrode. At least one of the bridges comprises a portion having amaximum height in a direction parallel to the direction of the flow and amaximum gauge in a direction orthogonal to the direction of the flow, whereinthe maximum height is larger than the maximum gauge, preferably at leasttwice the maximum gauge. The present embodiment is associated withsimilar advantages and effects as described with reference to the structure ofthe grid of the first electrode.
    According to an embodiment, the second electrode comprises astructured surface portion facing the first electrode. The structured surfaceportion may comprise micro- and/or nanostructures which may increase thearea of the surface portion. The microstructures and/or nanostructures mayfor example include the geometrical form of hills, ridges, paraboloids, pillars,or trenches. lncreasing surface area of the second electrode is advantageousin that it may improve the ability of collecting, or absorbing, electrons andhence improve the efficiency of the electrode. Further, by increasing thesurface area by means of micro- and /or nanostructures, a relatively higheractive surface area can be achieved on a relatively small surface portion. Thisadvantageously allows for a relatively larger active surface area and arelatively lower flow resistance. A relatively larger active area may alsoincrease the lifetime of the second electrode, since it may then be lesssensitive to contaminants passivating the surface.
    According to an embodiment, the second electrode comprises aconcave surface portion facing the first electrode. A concave surface portionis advantageous in that it may provide an increased surface area ascompared to a flat surface portion, thereby enhancing the ability to collectelectrons, e.g., electrons emitted by the first electrode. The concave surfacemay e.g. conform to an arc of a circle, or a surface of a sphere or of acylinder, having its centre or symmetry axis at an edge or tip of the firstelectrode. Thereby, a homogenous electric field may be achieved betweenthe first electrode and the second electrode.
    According to an embodiment, at least one of the bridges and/orjointsof the second electrode comprises a channel, or a plurality of channels,adapted to allow the fluid to flow through said channel. By arranging apassage through the material of the grid, the flow may be increased and/orthe fluid resistance reduced.
    According to an embodiment, the device comprises a support structurearranged to separate the second electrode from the first electrode in thedirection of the flow. The support structure may e.g. be electrically non-conductive and have a well defined thickness so as to maintain a desiredspacing between the first and second electrodes. The support structure maye.g. be formed as a grid or a spacer comprising e.g. ceramics or polymers,and the first and/or second e|ectrode(s) may be connected to or arranged onthe support structure by means of e.g. welding, gluing, soldering, brazing,glazing or sintering. The support structure may comprise an a|ignmentstructure adapted to a|ign the first electrode with the second electrode, and/orto a|ign several stacked device with each other. The a|ignment structure maye.g. comprise a protruding member and a receiving member, such as adepression or recess, wherein the protruding member is adapted to cooperatewith a corresponding receiving member of another support structure, and viceversa. Thereby the assemblage and a|ignment of the electrodes and/or thedevice may be facilitated.
    According to further embodiments, at least one of the first electrode,the second electrode and the support structure comprises a deformationstructure arranged to compensate for, or absorb, e.g. thermally inducedstresses, particularly in a plane orthogonal to the direction of the fluid flow.The deformation structure may e.g. be formed by a bridge being curved in theplane orthogonal to the direction of the flow. As the bridge is exposed tostresses or torsional torques in the plane orthogonal to its height (i.e. the flowdirection), the bridge may due to its relatively large height and small gaugetend to deform in that plane rather than in the flow or height direction. Thisadvantageously allows for a device being less sensitive to thermally inducedstresses and thermal expansion. Thereby a device having relatively welldefined dimensions and a relatively reliable shape may be achieved.Furthermore, the deformation structure may allow materials having differentcoefficients of thermal expansion (CTE) to be combined. As an example, thefirst and/or the second electrodes may be formed of a material having a firstCTE whereas the support structure, to which the first and/or the secondelectrodes may be attached, may have another CTE. ln such case, adeformation structure may be provided in the electrodes and/or the supportstructure so as to enable any internal thermal stresses that may be caused bythe difference in CTE to be absorbed by the deformation structure beingdeformed in the p|ane orthogonal to the direction of the fluid flow. Thus, thedeformation structure may enable a more reliable device having a prolongedlife.
    According to an embodiment, the first electrode and/or the secondelectrode and/or the support structure is formed of a material that isselectively deposited so as to form the desired structure. The depositingmethod may e.g. comprise molding, plating, screen printing, glazing,sputtering, evaporation or sintering.
    Alternatively, or additionally, the manufacturing may comprise removalof material, e.g. by selectively removing material from a substrate. Examplesof suitable techniques may include cutting, milling, etching, and abrasiveblasting.
    The first and/or second electrodes may advantageously comprise amaterial that has a relatively good ability of emitting electrons and ischemically stable, or inert, in relation to the pumped f|uid. Further, thematerial may have a relatively high temperature resistance. Examples of suchmaterials may include e.g. Pt, Au, and stainless steel.
    According to an embodiment, the applied electric potential differencebetween the first and the second electrodes may be varied as a function oftime. Experiments have shown that by e.g. alternating the potential differencebetween a first, positive value and zero, and/or between a positive and anegative value, the f|uid flow per unit area, and hence the pump efficiency,may be improved.
    Examples offluids, i.e. liquids and gases, that can be pumped bymeans of embodiments of the inventions includes e.g. dielectrics such asacetone, alcohols, helium, nitrogen, and fluorocarbon-based fluids such ase.g. FluorinertW' or NovecTM.
    Further objectives of, features of and advantages with the presentinvention will become apparent when studying the following detaileddisclosure, the drawings and the appended claims. Those skilled in the artrealise that different features of the present invention, even if recited indifferent claims, can be combined into embodiments other than thosedescribed in the following.
    Brief description of the drawinqsThe above, as well as additional objects, features and advantages ofthe present invention, will be better understood through the followingillustrative and non-limiting detailed description of embodiments of the presentinvention. Reference will be made to the appended drawings, on which:figure 1 is a schematic perspective view of a first and a secondelectrode according to an embodiment of the invention;figures 2a-d show cross sectional portions of the first and secondelectrodes according to an embodiment of the invention, wherein the crosssections are taken along the flow direction;figure 3 illustrates a device according to an embodiment of theinvenfion;figures 4a and b are top views of an electrode provided with adeformation structure according to embodiments of the invention;figure 5 is a cross section of a pump assembly according to anembodiment of the invention; andfigures 6a and b graphically illustrate electric current pulses applied tothe emitter in accordance with an embodiment of the invention.
    All the figures are schematic, generally not to scale, and generally onlyshow parts which are necessary in order to elucidate the invention, whereasother parts may be omitted or merely suggested.
    Detailed description of embodimentsFigure 1 shows a first electrode, or emitter 110, comprising bridges 111and joints 112 forming a grid that allows a fluid to flow through the emitter110. The emitter 110 has a lateral extension in a plane perpendicular to theintended flow direction, which is indicated by an arrow in figure 1. Accordingto this embodiment, the second electrode, or collector 120, comprises bridges121 and joints 122 that are arranged in a similar grid the one described withreference to the emitter 110. Consequentiy, the collector 120 may have a|atera| extension in a plane perpendicular to the direction of the flow such thatboth the emitter 110 and the collector 120 are parallel to each other.
    The emitter 110 and the collector 120 may be arranged spaced apartfrom each other in the flow direction by a positive distance d. The spacingmay e.g. be maintained by a support arrangement, or grid spacer 130 (notshown in figure 1) being arranged between the emitter 110 and the collector120. A relatively narrow gap d may be desirable since such gap may providea relatively high electric field and thus enhance the electrohydrodynamiceffect affecting the flow rate. The use of a grid spacer 130, which may have awell defined thickness, may advantageously reduce the risk of a shortcut orbreakdown between the emitter 110 and the collector 120. As will bediscussed in more detail below, the grid spacer 130 may e.g. have a similarconfiguration as the emitter 110 and/or the collector 120, i.e. comprising agrid of bridges 111, 121 and joints 112, 122. The grid spacer130 mayhowever have other configurations as well, such as e.g. being formed as aframe supporting the |atera| edges of the emitter 110 and/or collector 120.lt will also be realised that the grid may have one of a broad variety ofshapes, wherein the edges and the joints e.g. may form a grating, a net, ahole pattern, a honeycomb structure, or other structures or patterns suitablefor admitting a flow through the emitter 110 and/or collector 120.
    Figure 2 shows a cross section of a portion of the emitter 110 andcollector 120 of the device, taken through three pairs of the bridges 111, 121and along a plane parallel to the flow direction. According to this embodiment,the bridges 111 of the emitter 110 is arranged at a constant distance d fromthe bridges 121 of the collector 120, wherein the bridges 111 of the emitterhave a maximum height h1 in the flow direction and a maximum gauge w1 ina direction orthogonal to the flow direction. As shown in figure 2, themaximum height h1 is greater than the maximum gauge w1 so as to enable arelatively stable and rigid grid structure that can carry a relatively large load inthe flow direction without a risk of deforming or collapsing, and yet have arelatively large open area allowing the fluid flow. According to thisembodiment, the collector 120 may have a similar relationship between themaximum height hg and the maximum gauge wg of the bridges 121. The ratiobetween the maximum height h1, hg and the maximum gauge w1, wg may e.g.be larger than 1, and more preferably larger than 2.
    The cross section of the bridges 111 of the emitter 110 may comprise adownstream portion 113 having a tapered shape forming an edge or a point114 facing the collector 120. The tapered shape may e.g. be manifested asan edge or narrow end 114 extending along the downstream portion 113 ofthe bridge 111, or one or several protrusions having a shape conforming toe.g. a tip, needle, pyramid, dome, etc. As the emitter 110 is subjected to anelectric potential difference, there may be an electric field concentration at theedge 114 of the tapered portion 113 which may facilitate or promote emissionof electrons.
    Correspondingly, the portion of the bridges 121 of the collector 120which face the emitter 110 may be provided with a dedicated shape orsurface structure for enhancing collection of the emitted electrons. Thebridges 121 and/orjoints 122 of the collector 120 may e.g. be provided with aconcave surface portion 123 increasing the surface area, and/or a structuredsurface comprising microscopic protrusions and/or recesses 124 increasingthe active surface area. The structures 124 may e.g. be formed by molding,electroplating, surface treatment or by selectively adding and/or removingmaterial by e.g. abrasive blasting, etching, milling, grinding, etc.
    Figure 2a shows an example embodiment wherein the emitter 110 andthe collector 120 are formed by screen printed Pt paste which has beensintered at about 800°C so as to form a grid of bridges having a maximumheight h1, hg of about 100-200 um and a maximum gauge w1, wg of about 50um. As shown in figure 2b, the collector 120 has been equipped with a micro-structured surface portion 124, facing the emitter 110, by means of micro-blasting, wherein the surface is bombarded with sharp, micrometer-sizedparticles so as to increase the area of the surface.11The devices 100 in figures 2b-d is similar to the device 100 describedwith reference to figure 2a. According to figure 2b, the emitter 110 is furtherprovided with a tapered upstream portion 117, forming a relatively sharp edge118 directed towards the fluid flow so as to reduce the flow resistance andhence enhance the flow through the emitter 110. As indicated in figures 2cand d, the collector 120 may further define channels 126 extending throughthe bridges 121 and/or the joints 122 (not shown) of the grid in order todecrease the flow resistance. The channels 126 may e.g. be effected byetching, such as e.g. reactive ion etching, wet etching, etc.
    Figure 3a is a top view indicating the outline or contour of a first orsecond electrode, such as e.g. an emitter 110. As shown in figure 3a, theemitter 110 may comprise alignments structures 119, which also can be usedas electric contact portions for enabling electric connection of the emitter 110.The electric contact portions 119 may e.g. comprise protrusions which areintegrally formed with the emitter 110, and which may be adapted to engagewith a corresponding structure of e.g. a support structure 130 and/or stackingstructure 140 (not shown in figure 3a).ln figure 3b, a perspective view of a portion of an emitter 110 is shown,the emitter 110 being similar to the emitter 110 described with reference tofigure 3a. According to figure 3b, the alignment structure 119 is bent to form acontact portion enabling electric connection of the emitter.
    Even though the embodiments described with reference to figures 3aand b relates to an emitter 110, it will be appreciated that the same featuresand advantages e.g. may apply to a collector 120.
    Figures 4a is a cross section of a device according to an embodimentof the invention. The device comprises a first electrode, or emitter 110, and asecond electrode, or collector 120, which are arranged in a stacking structure140. The emitter 110 and the collector 120 has a lateral extension in a planeperpendicular to the direction of the fluid flow, and are arranged spaced apartfrom each other by a support structure, or grid spacer 130. According to figure4a, the emitter 110 and the collector 120 comprises a respective contactportion 119, 129 arranged at one of the sides of the device. The respectivecontact portions 119, 129 may formed as integrally formed protrusions of the12electrodes and be adapted to engage with an edge of the stacking structure.The protruding contact portions 119, 129 may hence act as alignmentstructures during assemblage of the devices and/or enable electric contactingof the electrodes 110, 120.
    The stacking structure 140 may comprise alignment structures 142 forfacilitating alignment of the stacked devices 100. The alignment structures142 of the stacking structure may 140 e.g. comprise a protruding portionadapted to fit into a recess of a corresponding alignment structure of a belowdevice of the stack. Correspondingly, the alignment structure 140 maycomprise a recess adapted to receive a protruding portion of a alignmentstructure of an above device in the same stack. Thereby the alignment of astack of a plurality of devices 100 may be facilitated.
    Figure 4b shows a similar device 100 as the one described withreference to figure 4a, wherein the emitter 110 and the collector 120 eachhave contacts portions 119, 129 arranged at both sides of the device.According to other embodiments, the contact portions 119, 129 may also bearranged such that the contact portions 119 of the emitter 110 are arranged ata side opposite to the side at which the contact portions 129 of the collector120 are arranged. This advantageously allows the emitters 110 and collectors120 to be electrically contacted at separate sides of the device 100, whichmay facilitate assemblage and handling of the devices 100 and/or pumpassembly 200.
    Figure 5a shows a deformation structure 115 of a grid acting as e.g. anemitter 110 in a device 100 according to embodiments of the presentinvention. The grid comprises bridges 111 and joints 112 in accordance withthe previously described embodiments. As indicated in figure 5a, thedeformation structure 115 is composed of bridges 111 that are curved in aplane normal to the flow direction. The curved shape may e.g. be formedduring manufacturing of the bridges 111, or induced by e.g. thermal stressesoccurring during use of the device 100. The curved shape may also comprisea weakened portion, e.g. a portion having a reduced gauge, so as to make iteasier to deform upon heat induced stresses. As the material of the grid mayexpand with an increasing temperature, the bridges 111 of the deformation13structure 126 may be compressed by compressive forces acting in the lengthdirection of the bridges 111. By length direction should be understood thedirection of extension between a first joint and a second joint. Thereby thelateral expansion of the grid may be absorbed by the deformation structure115 and thermally induced stresses reduced so that the emitter 110 otherthan the deformation structure 115 may keep its original shape despitethermal expansion. lt should however be understood that the forces acting onthe bridges 111 of the deformation structure 115 also, or alternatively, may becaused by e.g. a torsional moment, or torque, acting on the structure.
    Figure 5b shows a similar deformation structure 125 as described withreference to figure 5a, wherein the deformation structure 125 is formed ofbridges 121 of a collector 120 of a device 100 according to an embodiment. ltwill however be understood that the device 100 may be provided withdeformation structures 115, 125 arranged in any one, or several, of theemitter 110, the collector 120, and the support structure 130.
    The deformation structure 115, 125 may be provided in an emitter 110and/or collector 120 that is attached to a support structure 130, wherein in thesupport structure 130 may have a coefficient of thermal expansion (CTE) thatdiffers from the CTE(s) of the emitter 110 and/or collector 120. ln case theemitter 110 and/or collector 120 is/are rigidly attached to the support structure130, the risk for deformations, such as e.g. bending and flexures, anddamages such as fractures, disconnected or loosening joints etc. may bereduced by the deformation structure 115, 125. Thereby, reliability and usefullife of the device 100 may be increased.
    Figure 6 shows a cross section of a pump assembly 200 comprising astack of three devices 100 according to any one of the previously describedembodiments. The cross section is taken along the direction of the flow(indicated by an arrow in figure 6) and across a respective bridge 111, 121 ofthe grids of the electrodes 110, 120. Each device comprises an electronemitting electrode (emitter) 110, an electron collecting electrode (collector)120, and a grid spacer 130 arranged to separate the emitter 110 and thecollector 120 in the direction of the flow. According to this embodiment, the14emitters 110 and collectors 120 may comprise e.g. Pt, Au, or Stainless steelforming e.g. the bulk material or a surface coating.
    The grid spacer 130 may e.g. be formed as a grid supporting theemitter 110 and the collector 120. As illustrated in figure 6, the grid spacer130 may comprise a peripheral frame of bridges to which the edge portions ofthe emitter 110 and the collector 120 are attached by e.g. welding, solderingor gluing. Alternatively, or additionally, the grid spacer 130 may compriseother spacing structures such as pillars or spacers, etc. The grid spacer 130may also comprise one or several spacing members, such as e.g. additionalbridges or pillars, supporting the centre portions of the emitter and collector.The grid spacer 130 may also comprise a deformation structure 115, 125 (notshown) similar to the deformation structure described with reference tofigures 5a and b.
    The spacing d of the emitter and collector may be determined by theheight of the bridges of the grid spacer 130, which may hence determine themagnitude of the electric field induced between the emitter 110 and thecollector 120. The distance d between the emitter 110 and the collector 120may e.g. be within the range of 10 um and 1000 um.
    Further, the grid spacer 130 may comprise an alignment structure forfacilitating alignment of the emitter 110 and the collector 120, and/oralignment of the devices 100 of the stack.
    The pump assembly may also comprise a stacked structure with stagespacers 140 arranged to maintain a distance between the emitter 110 of afirst device and the collector 120 of a second device. The stacking structure140 may also comprise an alignment structure 142 (not shown in figure 6) forfacilitating alignment and assemblage of the stacked devices 100, andpossibly a deformation structure 115, 125 as described with reference tofigures 5a and b in order to reduce any mechanical stresses between thecomponents of the assembly 200.
    The grid spacer 130 and/or the stacking structure 140 may e.g.comprise a ceramic material, such as AlgOg or MacorTM.
    As shown in figure 6, the emitters 110 and the collectors 120 may beconnected to an external voltage supply (not shown) by an electric connectoror terminal 150. ln this manner, an electric potential difference may be appliedbetween the emitter 110 and collector 120 of the respective devices 100. Theelectric potential difference may induce an electric field which may promotethe electron emission and impart movement of the fluid between and througheach of the emitter 110 and collector 120. Further, the electric connection 150between the emitters 110 and/or collectors 120 and the external power supplymay be provided by mechanical features of the stacking structure and/or byelectric contact portions 129 (not shown in figure 6). The mechanical featuresmay e.g. be adapted so as to enable the electric connection to be formed bye.g. dispensing or screen printing, followed by e.g. sintering or welding.Advantageously, several or all of the emitters 110 and/or collectors 120 of thestack can be connected in the same manufacturing step.
    Figure 7a and b shows, as a function oftime t, an electric current iprovided to the emitter 110 of a device 100 according to the invention. lnfigure 7a, a positive current is applied and maintained for a first time period,and then removed. After a second time period the current supply is switchedon again, thus forming a second pulse. Repeating this procedure can reducethe space charges that may be present in the fluid and may also allow anyionized particles to recombine.
    To further improve relaxation, a pulse-reverse current may beintroduced between the pulses described with reference to figure 7a. Anexample of such process is shown in figure 7b, wherein the positive pulsesare separated by negative pulses. As shown in figure 7b, the negative pulsesmay have a larger absolute value than the positive pulses, but last for ashorter period of time so as to enable an overall positive flow. This procedureof separating the positive pulses by reverse pulses may advantageouslyimprove relaxation, possibly to remove contaminants of the emitter 110 and/orcollector 120.
    From a design point of view, it is an advantage to confine chargedparticles, such as e.g. ions, between a portion of a bridge 111 and/orjoint 112of the emitter 110 and a corresponding portion of a bridge 121 and/orjoint122 of the collector 120. Outside this volume, i.e. between the open portionsof the respective grid, the charged ions may have a limited effect on the16pumping action. The time duration of the positive pulses may be selectedsuch that negatively charged ions, created at the emitter, may just reach thecollector 120. Hence, if the time duration is sufficiently short, the spreading ofunwanted ions into the liquid loop may be limited. This time length can becalculated from the ion mobility, where a range from 2><10'8 to 2><10'7 mZ/Vs isknown form the prior art. For a pump having an electrode spacing of 100 um,this may correspond to pulse duration of around 1 ms. The zero or negativepulse may advantageously be sufficiently long to allow recombination of ionsor charged particles.
    As outlined above, the method for controlling the flow of a fluid asillustrated by figures 6a and 6b may be embodied as computer-executableinstructions distributed and used in the form of a computer-program productincluding a computer-readable medium storing such instructions. By way ofexample, computer-readable media may comprise computer storage mediaand communication media. As is well known to a person skilled in the art,computer storage media includes both volatile and non-volatile, removableand non-removable media implemented in any method or technology forstorage of information such as computer readable instructions, datastructures, program modules or other data. Computer storage media (or non-transitory media) includes, but is not limited to, RAM, ROM, EEPROM, flashmemory or other memory technology, CD-ROM, digital versatile disks (DVD)or other optical disk storage, magnetic cassettes, magnetic tape, magneticdisk storage or other magnetic storage devices. Further, it is known to theskilled person that communication media (or transitory media) typicallyembodies computer readable instructions, data structures, program modulesor other data in a modulated data signal such as a carrier wave or othertransport mechanism and includes any information delivery media.
    权利要求:
    Claims (18)
    [1] 1. A device (100) for controlling a flow of a fluid, comprising: a first electrode (110); and a second electrode (120) offset from the first electrode in adownstream direction of the flow, the electrodes being connectable to avoltage source; wherein the first electrode comprises bridges (111) and joints (112) forming agrid structure, which is arranged to allow the fluid to flow through the firstelectrode; and at least a portion of at least one of the bridges has a maximum height(h1) in a direction parallel to a direction of the flow and a maximum gauge (w1)in a direction orthogonal to the direction of the flow, wherein said maximumheight is larger than said maximum gauge.
    [2] 2. The device according to claim 1, wherein said at least one of thebridges has a portion with a substantially uniform cross section andcomprises a tapered portion (113) having a cross section forming an edgeand/or tip (114) facing the second electrode.
    [3] 3. The device according to claim 1 or 2, wherein said at least one of thebridges comprises a tapered portion (117) having a cross section forming anedge and/or tip (118) facing away from the second electrode.
    [4] 4. The device according to any one of the preceding claims, wherein:the second electrode comprises bridges (121) and joints (122) forming a grid structure, which is arranged to allow the fluid to flow through thesecond electrode, and a least a portion of at least one of the bridges has amaximum height (hg) in a direction parallel to the direction of the flow and amaximum gauge (w2) in a direction orthogonal to the direction of the flow, wherein said maximum height is larger than said maximum gauge. 18
    [5] 5. The device according to claim 4, wherein the second electrodecomprises a surface portion facing the first electrode and being provided withmicrostructures (124) for increasing the area of the surface portion.
    [6] 6. The device according to claim 4 or 5, wherein the second electrodecomprises a concave surface portion (123) facing the first electrode.
    [7] 7. The device according to any one of claims 4 to 6, wherein at least oneof the bridges and/orjoints of the second electrode comprise a channel (126)adapted to allow the fluid to flow through said channel.
    [8] 8. The device according to any one of the preceding claims, furthercomprising a support structure (130) separating the second electrode fromthe first electrode in the direction of the flow.
    [9] 9. The device according to any one of the preceding claims, wherein atleast one of the first electrode, the second electrode and the support structurecomprises a deformation structure (115, 125) arranged to deform in a planeorthogonal to the direction of the flow to absorb thermally induced stress inthe first electrode, the second electrode or the support structure, respectively.
    [10] 10.least one of the bridges being curved in the plane orthogonal to the direction The device according to claim 9, wherein said structure is formed of at of the flow.
    [11] 11. A pump assembly (200) comprising a plurality of stacked devices (100)according to any one of the preceding claims, further comprising a stackingstructure (140) adapted to align the devices with each other and to separatethe devices from each other in the direction of the flow.
    [12] 12. comprising: A method for manufacturing a device for controlling a flow of a fluid, 19 providing a first electrode (110) comprising bridges (111) and joints(112)forming a grid structure arranged to allow the fluid to flow through thefirst electrode, wherein at least a portion of at least one of the bridges has amaximum height (h1) in a direction parallel to the direction of the flow and amaximum gauge (w1) in a direction orthogonal to the direction of the flow, andwherein said maximum height is larger than said maximum gauge; providing a second electrode (120); and arranging the second electrode offset from the first electrode in thedirection of the flow.
    [13] 13.electrode(s) is/are provided by selectively depositing a metal. The method according to claim 12, wherein first and/or second
    [14] 14.electrode(s) is/are provided by selectively removing material from a metal The method according to claim 12, wherein first and/or second substrate.
    [15] 15.of providing the second electrode further comprises forming microstructures The method according to any one of claims 12 to 14, wherein the step (124) in a surface portion facing the first electrode.
    [16] 16.arranging the second electrode comprises arranging a support structure (130) The method according to any one of claims 12-15, wherein the step of arranged in between the first electrode and the second electrode.
    [17] 17. A method for controlling the flow of a fluid, comprising:providing a device (100) according to any one of claims 1 to 10;providing a fluid contacting the first electrode (110) ofthe device; andapplying an electric potential difference between the first electrode andthe second electrode (120).
    [18] 18.varying the electric potential difference as a function of time. The method according to claim 17, further comprising the step of
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    同族专利:
    公开号 | 公开日
    TWI662578B|2019-06-11|
    DK3090175T3|2019-05-06|
    EP3090175B1|2019-02-06|
    ES2723711T3|2019-08-30|
    SE537790C2|2015-10-20|
    WO2015084238A1|2015-06-11|
    EP3090175A1|2016-11-09|
    EP3090175A4|2017-11-01|
    US20160298617A1|2016-10-13|
    TW201533555A|2015-09-01|
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    法律状态:
    优先权:
    申请号 | 申请日 | 专利标题
    SE1351440A|SE537790C2|2013-12-04|2013-12-04|Electrohydrodynamic micropump device and method of manufacture of the device|SE1351440A| SE537790C2|2013-12-04|2013-12-04|Electrohydrodynamic micropump device and method of manufacture of the device|
    DK14868093.7T| DK3090175T3|2013-12-04|2014-12-01|Microfluidic device|
    PCT/SE2014/051426| WO2015084238A1|2013-12-04|2014-12-01|Microfluidic device|
    ES14868093T| ES2723711T3|2013-12-04|2014-12-01|Microfluidic device|
    EP14868093.7A| EP3090175B1|2013-12-04|2014-12-01|Microfluidic device|
    TW103141654A| TWI662578B|2013-12-04|2014-12-01|Microfluidic device|
    US15/100,566| US20160298617A1|2013-12-04|2014-12-01|Microfluidic device|
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