EP1525449A1 - Mesure d'impedance dans un microsysteme fluidique - Google Patents

Mesure d'impedance dans un microsysteme fluidique

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Publication number
EP1525449A1
EP1525449A1 EP03766323A EP03766323A EP1525449A1 EP 1525449 A1 EP1525449 A1 EP 1525449A1 EP 03766323 A EP03766323 A EP 03766323A EP 03766323 A EP03766323 A EP 03766323A EP 1525449 A1 EP1525449 A1 EP 1525449A1
Authority
EP
European Patent Office
Prior art keywords
impedance
detector
focusing
particle
electrode
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP03766323A
Other languages
German (de)
English (en)
Inventor
Thomas Schnelle
Torsten Müller
Stephen Shirley
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
PerkinElmer Cellular Technologies Germany GmbH
Original Assignee
Evotec OAI AG
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Evotec OAI AG filed Critical Evotec OAI AG
Publication of EP1525449A1 publication Critical patent/EP1525449A1/fr
Withdrawn legal-status Critical Current

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Classifications

    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N15/00—Investigating characteristics of particles; Investigating permeability, pore-volume or surface-area of porous materials
    • G01N15/10—Investigating individual particles
    • G01N15/1031—Investigating individual particles by measuring electrical or magnetic effects
    • G01N15/12—Investigating individual particles by measuring electrical or magnetic effects by observing changes in resistance or impedance across apertures when traversed by individual particles, e.g. by using the Coulter principle
    • G01N15/131—Details
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N15/00—Investigating characteristics of particles; Investigating permeability, pore-volume or surface-area of porous materials
    • G01N15/10—Investigating individual particles
    • G01N15/1031—Investigating individual particles by measuring electrical or magnetic effects
    • G01N15/12—Investigating individual particles by measuring electrical or magnetic effects by observing changes in resistance or impedance across apertures when traversed by individual particles, e.g. by using the Coulter principle
    • G01N15/131—Details
    • G01N2015/133—Flow forming
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N15/00—Investigating characteristics of particles; Investigating permeability, pore-volume or surface-area of porous materials
    • G01N15/10—Investigating individual particles
    • G01N15/1031—Investigating individual particles by measuring electrical or magnetic effects
    • G01N15/12—Investigating individual particles by measuring electrical or magnetic effects by observing changes in resistance or impedance across apertures when traversed by individual particles, e.g. by using the Coulter principle
    • G01N2015/135—Electrodes

Definitions

  • the invention relates to methods for impedance measurement in a fluidic microsystem, in particular methods for particle detection in fluidic microsystems by means of impedance measurements, and measuring devices for carrying out such methods.
  • WO 00/37628 describes a microsystem for cell permeation (or cell fusion) in which cell detection is carried out by electrical resistance measurement before the permeation.
  • the particles are transferred into different subchannels of the microsystem depending on their size under the effect of negative dielectrophoresis. In each subchannel, the particles with the flowing liquid are moved past a pair of electrodes on which the resistance measurement takes place.
  • a disadvantage of the detection technology according to WO 00/37628 is that the particles are not aligned with respect to the respective pair of electrodes. A focus is not planned. The detector signal nale therefore have a reduced reproducibility, the detection is unreliable.
  • planar impedance sensors or electrode pairs are also used on opposite walls of a compartment of the microsystem.
  • the cells are guided through a nozzle (e.g. channel with a cross-section of 20 ⁇ m • 20 ⁇ m) for alignment relative to the sensors in order to obtain an easily evaluable impedance signal.
  • the signal-to-noise ratio of the impedance method essentially depends on the ratio of the cell radius to the channel cross-section at a detector electrode (see Koch et al.).
  • narrow nozzles or channels are characterized by an increased risk of clogging. They also reduce cell throughput.
  • the impedance measurement is usually carried out at at least one fixed frequency in the range from a few 10 kHz to MHz. By using several frequencies, additional information about the detected cells can be obtained.
  • single-cell impedance spectroscopy the impedance measurement is carried out for a specific frequency spectrum (see HGL Coster et al. In “BioElectroChem. BioEnerg. ⁇ ⁇ Vol. 40, 1996, pages 79-98).
  • hydrodynamic focusing is provided instead of a nozzle.
  • a fundamental disadvantage of hydrodynamic focusing is that measuring electrodes are usually attached to a duct wall, but focusing in the edge area is excluded or only with great technical precision Effort is realizable.
  • the hydrodynamic focusing is also only of limited use. It is particularly difficult due to the system geometry (short channel length) or low pumping rates. In addition, there is hydrodynamic stress when focusing, which is particularly undesirable for sensitive biological cells.
  • the object of the invention is to provide improved methods for impedance measurement in fluidic microsystems, with which the disadvantages of conventional detection methods are overcome and which, in particular, enable improved focusing of particles in the vicinity of detector electrodes.
  • the object of the invention is also to further develop the impedance measurement in fluidic microsystems such that particles are not only counted, but also further information about the particles is obtained.
  • the object of the invention is also to provide improved measuring devices for impedance measurement in fluidic microsystems.
  • a basic idea of the invention is to focus suspended particles which are to be detected in a compartment of a fluidic microsystem with at least one impedance detector, under the action of dielectrophoretic field forces which act in the compartment, in the vicinity of the impedance detector.
  • at least two focusing electrodes high-frequency electrical fields are generated, under the effect of which negative particles are used to move the particles relative to a liquid flow in the compartment into a partial area of the flow and thus position them in a predetermined manner relative to the impedance detector.
  • the particles are moved past the impedance detector in the compartment along a predetermined trajectory defined by the dielectrophoretic focusing.
  • the inventive combination of the impedance detector with the at least two focusing electrodes advantageously overcomes the disadvantages of conventional focusing techniques. In particular, undesirable loads caused by mechanical or hydrodynamic forces are avoided. Furthermore, the dielectrophoretic focusing can be optimally adapted to the particles to be detected.
  • the impedance measurement is carried out with at least one impedance detector which is arranged in a compartment of the microsystem through which a liquid flow passes.
  • the compartment is generally a line structure in the microsystem, such as. B. a channel or a flow through the reserve voir. Typical cross-sectional dimensions of the compartment are, for example, in the range from 200 ⁇ m to 800 ⁇ m (width) ′′ 20 ⁇ m to 100 ⁇ m (height).
  • the compartment is made of a solid material in a chip body (eg semiconductor, ceramic, plastic or the like).
  • the at least one impedance detector comprises at least two detector electrodes which are attached to one or different walls of the compartment have a predetermined, preferably reduced, distance from one of the detector electrodes.
  • the focusing can take place upstream relative to the impedance detector.
  • This embodiment can be advantageous because of the separate activation of focusing and detector electrodes.
  • focusing can be done at the impedance detector. Advantages can result from a simplified electrode structure.
  • the dielectrophoretic focusing comprises a movement into a partial region of the flow (e.g. into the middle of the flow) which lies on a connecting line between two detector electrodes arranged on opposite walls of the compartment or in its vertical projection a wall of the compartment is arranged at least one detector electrode.
  • This movement has the advantage that all particles pass the at least one detector electrode in a predetermined window, as in the case of a field barrier formed by a nozzle or funnel.
  • the passage of the window takes place without loading stirring of mechanical, solid components and avoiding focusing flow forces. This advantageously achieves an improvement in the signal-to-noise ratio (SNR). A laterally offset passage on the detector electrode is avoided.
  • SNR signal-to-noise ratio
  • the dielectrophoretic focusing can include a movement of particles in such a way that the perpendicular distance of a particle passing at least one of the detector electrodes is reduced.
  • the vertical distance of the particle passage at the detector electrode is set in a predetermined manner.
  • the particle focusing takes place with at least two focusing electrodes which are attached to a wall, e.g. B. the bottom of the compartment.
  • the particles can be moved towards the opposite wall of the compartment near the detector. This can be advantageous if e.g. B. for impedance spectroscopy an increased measurement time (or: reduced flow velocity) is desired, as is the case at the edge of the flow.
  • three focusing electrodes can be used, two of which converge on a wall of the compartment, e.g. B. are arranged to form a funnel-shaped field barrier.
  • the third electrode is arranged as a counter electrode on the opposite wall of the compartment.
  • the invention is particularly preferably implemented with two focusing electrode pairs which are arranged on opposite sides of the compartment (eg bottom, lid).
  • Each pair of focusing electrodes consists of two focusing electrodes, e.g. B. in the form of converging electrode strips.
  • the use of two pairs of focusing electrodes can be advantageous for setting predetermined trajectories through a funnel-shaped field barrier.
  • the at least one measured impedance value is evaluated not only in relation to the presence of a particle, but also in relation to the dielectric properties of the particle detected in each case.
  • additional information about the flowing particles can be obtained, such as. B. Information about the vitality state of a cell or the like.
  • a plurality of impedance values are recorded with at least one impedance detector and their time profile is evaluated in relation to the point in time, the direction and / or the speed at which at least one particle passes the impedance detector.
  • an asymmetrical electrode shape is preferably realized, which is generally characterized in that the electrode shape is not mirror-symmetrical in a direction parallel to the passage or flow direction with respect to axes perpendicular to the passage or flow direction.
  • an impedance detector with a single pair of detector electrodes each of which is characterized by an electrode shape that is asymmetrical with respect to the flow direction.
  • an impedance detector with a single pair of detector electrodes each of which is characterized by an electrode shape that is asymmetrical with respect to the flow direction.
  • the impedance values are detected with an impedance detector with detector electrodes, the shape of at least one of the detector electrodes changing in a direction parallel to the direction of flow of the liquid and / or the detector electrodes being arranged on opposite sides of the compartment and have different shapes.
  • a time-dependency of the change in impedance in the course of the particle advance can thus be recorded and evaluated with only one impedance detector.
  • the invention also relates to a measuring device for impedance measurement in a fluidic microsystem with at least one impedance detector which is arranged in a compartment of the microsystem which is penetrated by a liquid flow, and at least one focusing device which has at least two focusing electrodes for exerting electrophoretic forces on suspended Is equipped with particles that flow through the compartment.
  • the provision of the at least two focusing electrodes enables the formation of a funnel-shaped field barrier for particle focusing and has the advantage that the measuring device according to the invention can be optimally integrated into known fluidic microsystems based on fluidic chips.
  • the focusing device comprises at least two pairs of focusing electrodes, which form the funnel-shaped field barrier in the compartment.
  • a field barrier is formed by a distribution of high-frequency fields, which emanate from the focusing electrodes and exert dielectrophoretic repulsive forces on the particles.
  • a funnel-shaped field barrier is characterized by a field distribution that, apart from a field minimum (e.g. in the middle of the compartment), forms retention forces so that particles cannot pass by with the liquid flow and are forced through the field minimum. With the funnel-shaped field barrier, the particles can advantageously pass the impedance detector at a predetermined position.
  • the impedance detector in each case comprises at least two detector electrodes, which preferably have a planar shape on a wall or different, e.g. B. opposite walls of the compartment are attached. If one of the planar detector electrodes has a non-uniform shape relative to the direction of flow, the impedance detector supplies additional information about the detected particles or the microsystem when a time series of impedance values is recorded.
  • the shape of the detector electrodes is determined by their external shape or by structuring.
  • the outer shape includes, for example, triangular, oval, rectangular or circular shapes or shapes composed of these.
  • An electrode breakthrough or a passivation layer is provided on the electrode as a structuring.
  • the impedance detector itself can have a shape that is non-uniform or asymmetrical with respect to the flow direction, in which the detector electrodes are shaped differently or are arranged offset relative to one another. With this design, too, the change of Capacitance between the detector electrodes when a particle enters a characteristic time dependency, which in the impedance measurement value the additional information, for. B. on the direction of flow.
  • the at least one electrode structuring is formed by at least one detector electrode, in the surface of which a partial electrode is integrated, measurements can advantageously be carried out with a particularly high sensitivity.
  • the partial electrode preferably has a characteristic size which is equal to or smaller than the size of the vertical projection of the particle passing by onto the detector electrode with the partial electrode.
  • the impedance detector comprises at least two detector electrodes, which are arranged on at least one wall of the compartment and extend across the width of the compartment transversely to the direction of flow
  • the impedance detector is of a particularly simple construction.
  • the detector electrodes are preferably formed by straight electrode strips which are arranged one above the other on the walls of the compartment parallel to the direction of flow and have electrode strips with different widths and / or structured edges, the structured edges being offset transversely to the direction of flow.
  • the invention has the following advantages.
  • the dielectrophoretic focusing is particularly gentle when used for the detection of cells.
  • the focus can easily be changed when the particle type or operating conditions change.
  • the measuring device can be manufactured using processing techniques known per se as part of known fluidic chips. Further details and advantages of the invention will become apparent from the following description of the accompanying drawings. Show it:
  • FIGS. 1 to 4 different embodiments of measuring devices according to the invention
  • FIGS. 1 to 4 illustrate various embodiments of combinations according to the invention of focusing devices and impedance detectors, each of which is arranged in a channel of a fluidic microsystem.
  • Fluidic microsystems in particular for manipulating biological cells, are known per se and are therefore not described in further detail here.
  • FIG. 1 shows a channel 10 of the microsystem in a schematic top view (a) and side view (b).
  • the channel 10 is delimited by the side walls 11, 12, a bottom 13 and a top surface 14.
  • the distance between the side surfaces 11, 12 is preferably in the range from 100 ⁇ m to 1 mm, for example in the range from 200 to 800 ⁇ m (width of the channel), while the distance between the bottom 13 and the top surface 14 is preferably around 5 ⁇ m to 200 ⁇ m, e.g. B. 20 to 100 microns (height of the channel).
  • a flow of liquid flows through the channel 10 in the direction of the arrow.
  • the liquid flow is typically a laminar flow with the illustrated speed profile 15 and with a flow speed in the range of e.g. B.
  • Particles 16, which are to be detected by the method according to the invention, are suspended in the liquid flow.
  • the particles 16 move in the direction of flow at the same speed as the liquid. Before the focusing according to the invention, the particles rest relative to the liquid.
  • the particles 16 comprise, for example, synthetic particles (for example plastic beads) or biological cells or cell components or biologically relevant organic macromolecules.
  • a measuring device 20 is provided in the channel (or compartment) 10, which comprises a dielectrophoretic focusing device 30 and an impedance detector 40.
  • the focusing device 30 is arranged upstream relative to the impedance detector 40.
  • the side walls of the channel are continuous between the focusing device 30 and the impedance detector 40 without lateral openings.
  • the focusing device 30 comprises at least two focusing electrodes 31, 32.
  • two pairs of focusing electrodes 31-34 are provided, of which the first pair 31, 32 are arranged, for example, on the top surface 14 and the second pair 33, 34 on the bottom 13 are.
  • Each focusing electrode comprises a straight electrode strip, which is in each case on the top surface 14 or on the bottom 13 from the channel edge to the channel center. te is directed.
  • the ends 35 of the focusing electrodes are spaced apart.
  • the focusing electrodes are each connected to a control device (with a high-frequency voltage source) via a connecting line (not shown).
  • the impedance detector 40 is preferably arranged in the flow direction at a distance in the range from 10 ⁇ m to 2 mm from the focusing device 30.
  • the impedance detector comprises at least two detector electrodes 41, 42, which are arranged on the bottom 13 and on the top surface 14 of the channel 10.
  • Each detector electrode 41, 42 can be constructed per se, as is known from conventional impedance measurements in electrolytes. They preferably each have a planar electrode surface with an asymmetrical or non-uniform shape (see below).
  • the particles 16 flow with the liquid in a generally disordered manner through the channel 10 until they reach the focusing device 30.
  • a funnel-shaped field barrier which narrows in the direction of flow, is formed on the latter with the focusing electrodes 31-34 when the voltage is applied uniformly.
  • the ends 35 of the focusing electrodes 31-34 span a square in which there is a field minimum through which the particles 16 can pass.
  • the particles 16 are then in a partial area of the flow according to the position of the field minimum, for. B. lined up in the middle of the channel. In this order, the particles pass through the detector electrodes 41, 42.
  • the impedance measurement is carried out there, according to principles known per se.
  • symmetrical focusing electrodes 31-34 focus in the center of the channel both in the horizontal direction, ie in the middle between the side surfaces 11, 12, as well as in the vertical direction, ie in the middle between the bottom 13 and the top surface 14. It is not absolutely necessary to always focus in the vertical and horizontal directions. It is not absolutely necessary that the particles 16 are lined up in a focused manner in the center of the channel. In general, the portion of the flow in which the particles 16 are lined up is aligned with the detector electrodes 41, 42 when projected perpendicularly onto the bottom and top surfaces. In the vertical direction, the focus results from the balance between electrical field forces and the weight. When the electric field forces and weight forces have the same effect, the particles 16 are lined up in the equilibrium in the middle between the bottom and top surfaces 13, 14. Alternatively, other equilibrium positions can be set in particular by the shape and / or height of the field barrier, which is formed with the focusing electrodes 31-34 (see also FIG. 4).
  • Focusing and detection are each carried out using high-frequency voltages. It is one of the important and unexpected discoveries of the inventors that a possibly interfering, mutual influencing of focusing and detection can be avoided.
  • the at least one particle is focused and the at least one impedance value is measured at different frequencies. For example, different (separate) frequency ranges are used. Line-friendly focusing can be achieved by using a focusing frequency above a few 100 kHz. This area must be excluded for the impedance measurement.
  • the impedance measurement is preferably carried out at a frequency below, for example, 100 kHz.
  • the impedance measurement can alternatively take place at higher frequencies (e.g. 1 MHz) in order to obtain information about the interior of the particles, e.g. B.
  • the impedance detector 40 can be equipped with a frequency filter, e.g. B. be equipped with a low or bandpass filter. With the frequency filter, the frequencies at which the focusing electrodes are operated are excluded from the detection.
  • the interaction between focusing device 30 and impedance detector 40 can also be reduced by increasing the mutual distance in the direction of flow.
  • the distance is preferably approx. 10 ⁇ m to 2 mm. This is advantageously possible due to the laminarity of the flow in the channel 10.
  • the distance can also be increased, for example, up to 3 mm.
  • the impedance detector 40 can be constructed from a plurality of different detector electrodes 41, 42 and 43.
  • a pair of detector electrodes comprising two relatively large-area detector electrodes 41, 42 is provided on the bottom and top surfaces 13, 14. Both detector electrodes 41, 42 have the same outer shape. Only the upper electrode 42 is shown completely in the schematic plan view.
  • the lower electrode 41 is shown in the lower part of FIG. 2 for illustration purposes.
  • the upper detector electrode 42 contains an electrode structuring in that a third detector electrode 43 (partial electrode 43) is integrated into the upper detector electrode. It is arranged in a recess in the electrode surface of the upper electrode 42 at a distance from it.
  • the lower electrode 41 is partially recognizable by the distance.
  • the larger detector electrodes 41, 42 have dimensions of approx. 120 '150 ⁇ m, while the single, smaller sub-electrode 43 has a size corresponding to typical cell sizes in the biology of e.g. B. has 2 to 20 microns.
  • the three detector electrodes 41-43 according to FIG. 2 are preferably connected according to the principle illustrated in FIG. 3.
  • the upper detector electrode 42 is at ground potential.
  • An electrical resistance R is arranged between the upper detector electrode 42 and the third detector electrode (partial electrode) 43, which is dimensioned in accordance with the resistance of the liquid flowing in the compartment.
  • the measuring voltage U is taken from the third partial electrode 43 with respect to ground potential.
  • the impedance measurement according to the invention is carried out in such a way that the voltage U is continuously detected and the impedance is determined. As soon as a particle is located above the third partial electrode 43, the latter is shielded so that the voltage U rises.
  • the particle to be measured is passed over the small partial electrode 43, a voltage difference between electrodes 42 and 43 results.
  • This measurement is advantageously particularly sensitive, since with partial electrode 43, as with a virtual opening, a measuring range of high local resolution and sensitivity is created becomes.
  • the partial electrode 43 should therefore preferably not be significantly larger than the projection of the particle onto the electrode level.
  • Accurate focusing with the focusing electrodes is also advantageous.
  • the impedance and direction of passage of the particle can be measured with increased accuracy and reproducibility (see also FIG. 7).
  • An advantage of the 2 and 3 illustrated embodiment of the invention consists in the possibility of passing the particles with high accuracy over the small, third electrode 43.
  • the dielectrophoretic focusing creates a "virtual" window instead of the conventional Coulter nozzle, which is precisely aligned with respect to the third electrode 43. This enables a particularly high signal-to-noise ratio to be achieved.
  • FIGS. 4a (top view) and 4b (side view) schematically illustrate focusing in the vertical direction.
  • the impedance detector 40 comprises a pair of detector electrodes 44, which is arranged only on the top surface 14.
  • Two pairs of focusing electrodes 31, 32 and 33, 34 are used as the focusing device 30, of which the lower focusing electrodes 33, 34 are designed to be a distance dx longer in the flow direction than the upper focusing electrodes 31, 32
  • the field minimum is shifted from the center of the channel to the top surface 14, so that the particles 16 are focused in a partial region of the flow that is close to the pair of detector electrodes 44.
  • the smallest distance between the particles 16 and the pair of detector electrodes 44 is, for example, 1 ⁇ m.
  • the embodiment according to FIG. 4 with the electrodes arranged offset in the flow direction or with different lengths can have the advantage that the particles remain unchanged (horizontal) focusing between the side surfaces in the vertical direction closer to the electrode 44 or according to FIG. 2 to the partial electrode 43 where, firstly, they run slower and secondly, an increased impedance Show signal.
  • This process can be carried out in a self-calibrating manner via feedback, so that the impedance signal can advantageously be optimized and maximized when particles pass through by changing the amplitude of one of the electrode levels as a function of the flow velocity and / or the particle properties.
  • the focusing electrodes are operated with a different degree of control (amplitude, frequency) of the two electrode levels and / or the focusing electrodes are at different angles are formed relative to the direction of flow.
  • the measuring device can additionally be equipped with a defocusing device 50, which is illustrated schematically in the right part of FIGS. 4a and 4b.
  • the defocusing device 50 has the task of redistributing the particles in the entire flow profile after the measurement, or of enriching them in the region of the greatest flow velocity. This advantageously reduces the probability of adhesion of the particles to one another (in particular of biological cells) and the throughput can be increased.
  • the defocusing device 50 comprises defocusing electrodes 51 to 54 which, analogous to the principles mentioned above, cause the particles in the liquid to be displaced by negative dielectrophoresis.
  • the focusing or defocusing electrodes of a measuring device are preferably in the form of electrode strips with an arrangement corresponding to the desired field barrier educated.
  • the electrode strips can be curved in the respective wall plane (eg in the bottom surface), as is illustrated in partial image a in FIG. 5.
  • Two straight, parallel electrode sections 37, 38 adjoin the converging electrode sections 35, 36.
  • the formation of straight, parallel electrode sections at the ends of the focusing electrodes located in the direction of flow can be advantageous with regard to the effectiveness of the field barrier.
  • the sub-images b and c show embodiments of focusing electrodes which consist of three sub-electrodes.
  • the focusing electrodes 31, 32 are arranged on the top surface of a compartment, while the focusing counter electrode 39 is arranged on the bottom surface.
  • the field barrier is generated, for example, by applying high-frequency AC voltages with an offset phase position.
  • the phase position is, for example: 31: 0 °, 32: 120 °, 39: 240 ° or: 31: 0 °, 32: 180 °, 39: ground potential.
  • the arrangement according to FIG. 5b can be modified with the focusing electrode shapes according to FIG. 5a (see FIG. 5c).
  • the arrangement of focusing electrodes can be used simultaneously as a detector device.
  • the electrode strips are converged to produce a funnel-shaped field barrier in such a way that the electrode tips are at a small distance in the direction of flow, which corresponds approximately to the channel height.
  • the focusing electrodes (e.g. according to FIG. 1) are subjected to high-frequency voltages for focusing.
  • the impedance is diagonal, e.g. between the electrodes 31 and 34 or 32 and 33 measured. With a design according to FIGS. 5b or 5c, the impedance measurement can take place between one of the electrodes 31, 32 and the counter electrode 39.
  • the measured impedance signal depends not only on the dielectric properties (in particular dielectric constant, conductivity) of the particle and the suspension solution, but also on the volume fraction of the particle between the measuring electrodes. If the measuring electrodes are constructed nonuniformly or asymmetrically relative to the direction of flow, as is illustrated by way of example in FIG. 6, an impedance signal which is nonuniform over time is measured during particle passage at a constant flow rate. The impedance signal is asymmetrical with respect to the maximum. In addition to the flow velocity, the flow direction can also be determined from the curve (see FIG. 7). To provide non-uniform or asymmetrical measuring electrodes, they are given a specific electrode shape and / or an electrode structure.
  • the electrode structuring comprises, for example, openings or holes in the electrode surface.
  • passivation through passivation layers can also be provided on the electrode surface.
  • FIGS. 6a and 6b show, by way of example, electrode surfaces 44 with circular openings 45 (or passivation layers).
  • An asymmetrical electrode surface of an impedance detector according to the invention is given when the effective electrode surface changes in the direction of flow. This is given here, for example, by the series of openings 45.
  • the variation of the electrode area according to FIGS. 6c to 6f can also be provided by changing the outer shape.
  • the border of the electrode surface is characterized by at least one triangular, rectangular, oval or circular structure.
  • the measuring electrodes consist of an inert, conductive material, in particular metal, such as. B. platinum or gold.
  • the passivation layers consist of an insulating material, e.g. B. silicon oxide.
  • FIG. 7 shows an example of the time profile of an impedance signal that was recorded with an asymmetrical impedance detector according to FIG. 2.
  • the curve shows the impedance signal (arbitrary units) as a function of time.
  • the circles drawn above mark particle passes that were determined by video control. With each particle pass, the impedance curve shows a characteristic asymmetry relative to the respective maximum.
  • two secondary maxima can be measured, of which the second shoulder, over time, has a lower amplitude than the first shoulder.
  • the direction of flow can be derived from this.
  • the flow velocity can also be derived from the distance dt between the minima between a shoulder and the maximum, since dt corresponds to the passage time of the particles and the size of the measuring electrode is known.
  • the features shown in FIG. 7 can also be acquired by combinations of several measurement methods that are spaced apart in the flow direction.
  • the figures 8a and b show embodiments of two impedance sensors which extend across the width of the entire channel transversely to the direction of flow (see arrow).
  • the dashed electrode 42 above and the solid electrode 41 below on the top and bottom surfaces (see above) or vice versa shown schematically and enlarged.
  • these detectors When particles and in particular biological cells pass through, these detectors generate an asymmetrical impedance signal with which the particles can be counted or which enables the direction of the passage to be determined.
  • the signal / noise ratio can be less favorable than with the individual sensors described above, but this can advantageously be compensated for by using a suitable bridge measurement.
  • the impedance measurement according to the invention can be modified as follows.
  • the focusing electrodes can be structured, as is known per se from microsystem technology for providing predetermined field barrier profiles.
  • the focusing field barriers can also be modified by controlling the voltage and / or phase of the high-frequency electrical fields in the focusing device.

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  • Chemical & Material Sciences (AREA)
  • Dispersion Chemistry (AREA)
  • Physics & Mathematics (AREA)
  • Health & Medical Sciences (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Analytical Chemistry (AREA)
  • Biochemistry (AREA)
  • General Health & Medical Sciences (AREA)
  • General Physics & Mathematics (AREA)
  • Immunology (AREA)
  • Pathology (AREA)
  • Investigating Or Analyzing Materials By The Use Of Electric Means (AREA)

Abstract

L'invention concerne un procédé et un dispositif de mesure destiné à la mesure d'impédance dans un microsystème fluidique comportant un compartiment (10) qui est traversé par un flux de liquide contenant des particules en suspension (16) et est placé dans au moins un détecteur d'impédance (40) qui permet de détecter au moins une valeur d'impédance pour la détection de la ou des particule(s), cette valeur d'impédance étant caractéristique de l'impédance du compartiment et se modifiant en présence de la ou des particule(s) de manière prédéterminée. On effectue une concentration de la ou des particules à une distance prédéterminée par rapport au détecteur d'impédance, la concentration comportant un déplacement de la ou des particule(s) par rapport au liquide s'écoulant dans le compartiment par des forces diélectrophorétiques exercées par au moins deux électrodes de concentration (30).
EP03766323A 2002-07-29 2003-07-28 Mesure d'impedance dans un microsysteme fluidique Withdrawn EP1525449A1 (fr)

Applications Claiming Priority (3)

Application Number Priority Date Filing Date Title
DE10234487 2002-07-29
DE10234487A DE10234487A1 (de) 2002-07-29 2002-07-29 Impedanzmessung in einem fluidischen Mikrosystem
PCT/EP2003/008312 WO2004013614A1 (fr) 2002-07-29 2003-07-28 Mesure d'impedance dans un microsysteme fluidique

Publications (1)

Publication Number Publication Date
EP1525449A1 true EP1525449A1 (fr) 2005-04-27

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US20060243594A1 (en) 2006-11-02
JP2005534911A (ja) 2005-11-17
WO2004013614A1 (fr) 2004-02-12
JP4152949B2 (ja) 2008-09-17
AU2003253345A1 (en) 2004-02-23
DE10234487A1 (de) 2004-02-26

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