EP1858645A1

EP1858645A1 - Microfluidic system and corresponding control method

Info

Publication number: EP1858645A1
Application number: EP06723476A
Authority: EP
Inventors: Torsten Müller; Thomas Schnelle
Original assignee: Evotec Technologies GmbH
Current assignee: PerkinElmer Cellular Technologies Germany GmbH
Priority date: 2005-03-16
Filing date: 2006-03-16
Publication date: 2007-11-28
Also published as: US20090008254A1; DE102005012128A1; WO2006097312A1

Abstract

The invention relates to a microfluidic system comprising a carrier current channel (1) for receiving a carrier current containing particles suspended therein, and at least one electrode arrangement (3) which is arranged in the carrier current channel and used to manipulate the suspended particles (2), said electrode arrangement (3) comprising two manipulation electrodes (4, 5). According to the invention, the electrode arrangement (3) comprises two centering electrodes (6, 7), in addition to the two manipulation electrodes (4, 5), for centering the particles, the two centering electrodes (6, 7) being arranged in the carrier current channel (1) respectively upstream of one of the two manipulation electrodes (4, 5). The invention also relates to a corresponding control method.

Description

DESCRIPTION

Microfluidic system and associated driving method

The invention relates to a microfluidic system and an associated driving method according to the preamble of the independent claims.

Such microfluidic systems are known, for example, from Müller, T. et al. : "A 3D microelectrode for handling and caing single cells and particles", Biosensors and Bioelectronics 14, 247-256, 1999 known and have a flat carrier flow channel for receiving a carrier stream with particles suspended therein (eg biological Cells) with a dielectrophoretic electrode assembly in the carrier flow channel to manipulate the suspended particles. For example, the suspended particles in the carrier stream may be centered by a funnel-shaped electrode arrangement ("funnel") or fixed by a so-called "hook".

However, a disadvantage of the known microfluidic retention systems, for example the above-mentioned dielectrophoretic hooks, is the fact that the particles from the dielectrophoretic electrode arrangements in the carrier flow channel can be pushed upwards or downwards in the direction of the channel wall, which is particularly troublesome in biological cells ,

From Schnelle, T. et al. : "Trapping of Viruses in High Frequency Electric Field Cages", Naturwissenschaften 83, 172-176 (1996), Springer-Verlag is the use of dielectrophoretic cages are known to fix suspended particles in a field minimum within the field cage. These field cages have eight cubically arranged cage electrodes and center the suspended particles in all spatial directions, which is required here to prevent adhesion of the particles to the channel walls. For an individual electrical supply of the cage electrodes is necessary, which is technically very complicated and difficult, for example, the parallelizability.

Further embodiments of such field cages are known from Fuhr, G. et al .: "Positioning and Manipulation of Cells and Microparticles Using Miniaturized Electric Field Traps and Traveling Waves", Sensors and Materials, Vol. 2 (1995) 131-146.

The subsequently published patent application DE 10 2004 017 482 A1 likewise discloses microfluidic systems with dielectrophoretic elements, such as the field cages (cages) already mentioned in the beginning, funnels (Engles), and particle switches (Engl. switches "). However, the field cages also center the suspended particles in all spatial directions, which is necessary to prevent adhesion of the suspended particles to the channel walls of the carrier flow channel.

From ÜS2002 / 0182627 Al so-called biochips are known in which suspended particles are manipulated by electrophoresis. In addition, this patent application also discloses planar dielectrophoretic field cages, each positioning a suspended particle in a bore of a plate. However, this type of fixation leads deliberately to a physical contact between the fixed particles and the channel boundary, which is particularly disturbing in biological cells.

Furthermore, DE 199 52 322 C2, DE 103 11 716 A1 and US Pat. No. 5,454,472 disclose methods and devices for separating suspended particles by means of dielectrophoretic elements. From these patent applications, however, no measures are known to prevent the adhesion of suspended particles to the channel walls.

The invention is therefore based on the object of improving or simplifying the known microfluidic retaining systems described at the outset, in which case it is to be prevented that the suspended particles are pressed by the electrode arrangement in the direction of the channel wall.

This object is achieved by an inventive microfluidic system and an associated driving method according to the independent claims.

The invention includes the general technical teaching of arranging upstream of the manipulation electrodes (e.g., a so-called "hook") centering electrodes which focus the particles suspended in the carrier stream in the central plane of the carrier flow channel and thereby prevent the suspended particles from being forced towards the channel wall.

The term centering or focusing used in the context of the invention preferably means that the suspended particles are centered or focused at right angles to the flow direction. The microfluidic system according to the invention has an electrode arrangement with at least two manipulation electrodes and at least two centering electrodes arranged upstream of the manipulation electrodes.

The two manipulation electrodes may, for example, be so-called hooks ("hooks"), which in themselves are already known from the publication by Müller, T. et al. : "A 3D microelectrode for handling and caging single cells and particles", Biosensors and Bioelectronics 14, 247-256, 1999 are known, so that the content of this publication of the present description in the design of the manipulation electrodes in full account is.

It should also be mentioned that the manipulation electrodes do not necessarily have to be one-piece or continuous. Rather, there is also the possibility that the individual manipulation electrodes consist of a plurality of sub-electrodes, wherein the individual sub-electrodes of the manipulation electrodes can be controlled separately. For example, the individual manipulation electrodes can also be interrupted by passivation layers.

It is important, however, that the manipulation electrodes are curved against the direction of flow, as is the case for example with the known so-called hooks. Instead of hook-shaped manipulation electrodes, however, there is also the possibility that the manipulation electrodes are arc-shaped (eg semicircular) or annularly closed. They can also have the shape of a rectangle or part of a rectangle, a hexagon, or generally a polygon. The shape is therefore just as with the centering electrodes almost arbitrary. For example, the manipulation be circular electrodes, which allows the arrangement of multiple particles on closed paths.

Furthermore, the invention provides that the centering electrodes are at least partially enclosed by the manipulation electrodes arranged downstream of them. In the case of a hook-shaped manipulation electrode, this can be achieved in that the associated centering electrode is preferably arranged between the two legs of the hook-shaped manipulation electrode. In the case of an annular manipulation electrode, the associated centering electrode can be arranged inside the manipulation electrode.

In addition, the invention provides that the centering electrodes have a smaller spatial extent transversely to the flow direction than the manipulation electrodes, which is not the case in the case of the above-mentioned field cages with eight cubically arranged cage electrodes.

The centering electrodes are preferably triangular, rectangular, hexagonal, circular, circular or elliptical in shape, wherein the centering electrodes are transversely to the flow direction, preferably smaller than the manipulation electrodes.

It should also be mentioned that, in a preferred embodiment of the invention, the two centering electrodes can be controlled electrically separately from each other, so that the centering electrodes can be electrically driven in antiphase.

The same applies preferably also to the two manipulation electrodes which are used to enable an antiphase Control preferably also electrically isolated from each other are controlled.

In addition, the manipulation electrodes on the one hand and the centering electrodes on the other hand are electrically separately controlled, since the manipulation electrodes and the respectively associated centering electrodes should be electrically driven in anti-phase to achieve a centering effect.

It should also be mentioned that the two manipulation electrodes and / or the two centering electrodes are each preferably substantially planar (i.e., plane), wherein the two manipulation electrodes on the one hand and the two centering electrodes are preferably arranged in pairs substantially coplanar. This means that the individual electrodes are arranged in two mutually parallel planes, wherein in each plane in each case a manipulation electrode and an associated centering electrode is located. Compared to the field cage, the proposed arrangement is more robust to offset, which simplifies the manufacture of the systems.

The centering electrodes and the manipulation electrodes are in this case arranged in the flow direction at a distance from each other, which is preferably in the range of 1/8 to twice the distance of the electrode planes. For the handling of animal suspension cells, for example, blood cells, this is preferably in the range of 5 microns to 80 microns, with a distance of about 40 microns has been found to be particularly advantageous.

In an advantageous variant of the invention, the electrode arrangement has a plurality of manipulation electrode pairs and these associated Zentrierelektrodenpaare on. The individual manipulation electrode pairs may be arranged side by side or one behind the other in the carrier flow channel with respect to the flow direction. This array arrangement allows simpler and better long-term culturing of biological cells in microfluidic chips compared to conventional dielectrophoretic cages. For example, a plurality of so-called hooks can be arranged next to one another in the flow direction in order to fix suspended particles.

In this case, the individual manipulation electrode pairs can be electrically connected to one another, which enables a common electrical actuation, with the individual manipulation electrodes of a pair of manipulation electrodes being driven in antiphase in a conventional manner.

However, it is alternatively also possible for the individual manipulation electrode pairs to be at least partially electrically separated from one another and to be actuated at least partially electrically separately, which enables simple selective detection of the suspended particles.

Furthermore, the goal of the invention is to minimize the thermal loading of the suspended particles, which is particularly important in biological cells. However, the thermal loading of the suspended particles depends on the electrode width and electrode spacing, which parameters also affect the force exerted by the electrode assembly on the suspended particles.

Preferably, the lateral electrode width is in the range of 10% to 50% of the electrode spacing between the planes, since the ratio of the desired force to the unreacted desired heating of the suspended particles in this area is particularly good.

It should also be mentioned that the carrier flow channel of the microfluidic system according to the invention preferably has a flow cross-section which is in the range of 0.006 mm ² to 0.6 mm ² , which is customary in microfluidic systems. The height of the carrier flow channel may be, for example, in the range of 1 .mu.m to 400 .mu.m, while the width of the carrier flow channel may be, for example, in the range of 5 .mu.m to 1.5 mm.

In general, the cross section of the carrier flow channel may be different, it may be rectangular or trapezoidal, for example.

Furthermore, there is the possibility that the two coplanar arranged manipulation electrodes of the electrode arrangement according to the invention are arranged offset in the flow direction to each other. In the same way, the two can

Centering electrodes of the electrode assembly to be offset in the flow direction to each other. The offset in the flow direction may be in the range of 5% to 95%, 10% to 90%, 20% to 80% or 30% to 70% in relation to the distance between the manipulation electrodes and the centering electrodes. The possibility of offsetting the electrodes has the advantage that as a result the manufacturing process does not have to be set as high as, for example, in the already known field cages, where precise alignment of the electrodes for the functionality is fundamental.

However, the invention includes not only the microfluidic system according to the invention but also a biological device (eg a cell sorter) with such a microfluidic system.

Furthermore, the invention comprises an associated drive method for such a microfluidic system. On the other hand, the manipulation electrodes, on the one hand, and the centering electrodes assigned thereto, on the other hand, are preferably driven in an ephemeral manner in order to achieve the desired centering effect.

Alternatively, the arrangement can also be operated only single-phase. The activation takes place as described above, wherein the second phase is replaced by ground or free potential. This represents a significant simplification compared to the known field cage (2 or 4).

This not only simplifies the chip and the control electronics, but it also reduces the demands on the interface (capacitances, inductances), as phase shifts and propagation delays become less important.

Furthermore, there is the possibility that the centering electrodes are switched off when a particle has been fixed by the associated manipulation electrodes. Despite the deactivation of the centering electrodes, the trapped particles then remain in the hydrodynamic flow in the central plane in front of the downstream manipulation electrodes. This reduces the thermal and electrical load on the trapped particles, which is particularly important for biological cells.

The deactivation of the centering electrodes can optionally be done by the centering electrodes are switched to ground or floating, the centering electrodes at a ner floating circuit have a floating electrical potential.

Furthermore, there is the possibility that the centering electrodes are briefly actuated with an increased electrical voltage before being switched off.

Furthermore, the flow velocity in the carrier flow channel can be increased shortly before the deactivation of the centering electrodes.

In an advantageous variant of the invention, the centering electrodes serve not only for centering the suspended particles in the carrier flow channel, but also for examining the suspended particles. For example, the centering electrodes may first cause centering of the suspended particles until the suspended particles are trapped by the downstream manipulation electrodes. During this centering phase, the manipulation electrodes and the centering electrodes are electrically driven in anti-phase, as explained above. After trapping of the suspended particles by the manipulation electrodes, the centering electrodes can then be used as measuring electrodes. For this purpose, the centering electrodes are disconnected from the electrical control and connected to a corresponding measuring device. For example, the centering electrodes can be used as impedance measuring electrodes and perform an impedance spectroscopic examination of the trapped particles. The advantage of this is the good signal-to-noise ratio, since the centering or measuring electrodes have a small size and the particles to be examined are fixed close to the centering or measuring electrodes. In a variant of the invention, the electrode arrangement has annular manipulation electrodes both on the upper channel wall of the carrier flow channel and on the lower channel wall of the carrier flow channel. Preferably, the manipulation electrodes are actuated on the upper channel wall on the one hand and on the other hand on the lower channel wall on the other hand in an out-of-phase manner. However, there is alternatively also the possibility that the manipulation electrodes on the lower channel wall are grounded and only the manipulation electrodes on the upper channel wall are electrically driven. Furthermore, there is also the possibility that the manipulation electrodes on the upper channel wall are grounded and only the manipulation electrodes on the lower channel wall are electrically driven. Furthermore, there is the possibility that the manipulation electrodes on the upper channel wall on the one hand and on the lower channel wall on the other hand are electrically controlled with a phase difference of 90 °, for example, to generate rotational fields.

In the embodiments with annular manipulation electrodes described above, the centering electrodes are preferably located in the center of the annular manipulation electrodes. The centering electrodes can be electrically grounded. Alternatively, there is the possibility that only the centering electrodes on the upper channel wall or only the centering electrodes on the lower channel wall are grounded, while the respective other centering electrodes are electrically driven. In a variant of the invention, the electrical control of the centering electrodes takes place on the upper channel wall on the one hand and on the other hand on the lower channel wall in electrically opposite phase.

Furthermore, there is the possibility that the annular manipulation electrodes are interrupted and in each case consist of several Reren circle segment-shaped electrode segments exist, but which are electrically connected to each other. The interruptions between the individual electrode segments advantageously permit the entry of particles into the electrode arrangement or the emergence of particles from the electrode arrangement.

Furthermore, there is the possibility that the individual electrode segments have outwardly projecting limbs, with the outwardly projecting limbs of adjacent electrode segments forming a funnel-shaped electrode arrangement ("funnel"), as explained in the description of the prior art , These funnel-shaped electrode arrangements facilitate the introduction of particles into the electrode arrangement.

Furthermore, there is the possibility that downstream of the electrode arrangements, particle switches are arranged, as described in the publication by Müller, T. et al. "A 3D microelectrode for handling and caging single cells and particles", Biosensors and Bioelectronics 14, 247-256, 1999 are known. The particles emerging from the field cages can then be selectively conveyed or laterally deflected by the particle switches located behind them into a further electrode arrangement.

In an advantageous embodiment of the invention, a multiplicity of electrode arrangements arranged in the form of a matrix are provided, each of which has at least one centering electrode and at least one manipulation electrode. The individual electrode arrangements can in this case be constructed in accordance with the variants described above. For each line of the electrode arrangements in this case preferably two line control lines are provided, wherein the a row control line is connected to the centering electrodes of the electrode arrays of the respective row, while the other row control line is connected to the manipulation electrodes of the electrode arrays of the respective row. In addition, two column control lines are provided for each column, wherein one column control line is connected to the centering electrodes of all the electrode arrangements of the respective column, while the other column control line is connected to the manipulation electrodes of all the electrode arrangements of the respective column , Each centering and manipulation electrode is thus connected in each case to a row control line and a column control line. In this way, specific electrode arrangements can be selectively switched off by switching the two associated row or column control lines to ground or free potential. The other electrode arrangements then remain switched on.

Other advantageous developments of the invention are characterized in the subclaims or are explained in more detail below together with the description of the preferred embodiments of the invention with reference to FIGS. Show it:

FIG. 1 shows a simplified perspective illustration of a microfluidic system according to the invention,

FIGS. 2A-2D show various views of a conventional microfluidic system, FIGS. 3A-3D show views corresponding to FIGS. 2A-2D in the case of the microfluidic system according to the invention, 4A, 4B show different views of an electrode arrangement of another exemplary embodiment of a microfluidic system according to the invention,

FIGS. 5A, 5B show a further exemplary embodiment of an electrode arrangement according to the invention,

Figures 6A-6C further variants of possible orders in a Elektrodenan- ^"according to the invention mikroflu- idischen system,

FIGS. 7A, 7B show further exemplary embodiments of electrode arrangements which can be used in a microfluidic system according to the invention,

FIG. 8 is a graph showing the heating produced by the electrode assembly and the force applied to the suspended particles as a function of electrode width and electrode spacing;

FIGS. 9A-9E show further variants of electrode arrangements in a microfluidic system according to the invention,

FIG. 10 shows different views of an electrode arrangement in a further exemplary embodiment of a microfluidic system according to the invention,

FIG. 11 shows different views of further electrode arrangements,

FIG. 12 shows different views of further electrode arrangements, in which the centering electrodes on the one hand and the manipulation electrodes on the other hand are driven with different frequencies,

13A, 13B show a variant of the embodiment according to FIGS. 5A and 5B, 14A, 14B show a further variant of an embodiment according to the invention with circular centering electrodes and annular manipulation electrodes, FIGS. 15A, 15B show yet another embodiment of an arrangement according to the invention with circular centering electrodes of annular manipulation electrodes, wherein the control of the centering electrodes takes place in a different manner, FIG. 16B shows an alternative embodiment with circular segment-shaped manipulation electrodes and circular centering electrodes,

17A, 17B show a further embodiment with annular manipulation electrodes and circular centering electrodes,

18 shows a simplified representation of a matrix-shaped electrode arrangement according to the invention with a multiplicity of circular or annular electrode structures, FIGS. 19A-19C show further variants of electrode structures according to the invention,

20 shows an electrode structure according to the invention with a plurality of electrode arrangements, each of which has centering and manipulation electrodes.

The perspective view in FIG. 1 shows a carrier flow channel 1 of a microfluidic system, as can be used, for example, in a cell sorter for sorting biological cells. The cell sorter itself may in this case be designed in a conventional manner, so that a detailed description of the cell sorter can be omitted below. The carrier flow channel 1 in this case has a rectangular cross-section with a height of 40 microns and a width of 150 microns and carries a carrier stream with particles suspended therein, with only a biological cell 2 is shown schematically for simplicity.

The carrier stream with the biological cells 2 suspended therein flows in the carrier flow channel 1 in the x-direction, as illustrated by the arrows.

In the carrier flow channel 1, an electrode assembly 3 is arranged, which consists of two hook-shaped manipulation electrodes 4, 5 and two circular centering electrodes 6, 7.

The two manipulation electrodes 4, 5 are formed in a conventional manner and are driven accordingly, which from the already mentioned above publication by Müller, T. et al. : "A 3D microelectrode for handling and caging single cells and particles", Biosensors and Bioelectronics 14, 247-256, 1999 is known so as to avoid

References to this publication, the contents of which are to be fully attributed to the present description. It should be mentioned at this point only briefly that the two manipulation electrodes 4, 5 are each formed planar and coplanar with each other, wherein the manipulation electrode 4 is disposed on the upper channel wall of the carrier flow channel 1, while the other manipulation electrode 5 at the lower channel wall of Carrier flow channel 1 is arranged.

The two centering electrodes 6, 7 are also planar and aligned coplanar with each other, wherein the centering electrode 6 is disposed on the upper channel wall of the carrier flow channel 1, while the centering electrode 7 at the lower channel wall of the carrier flow channel 1 is arranged. The centering electrode 6 thus lies with the manipulation electrode 4 in a plane, while the centering electrode 7 lies with the manipulation electrode 5 in a plane.

Between the centering electrode 6 and 7 and the associated manipulation electrode 4 and 5 is in the flow direction, a distance of about 40-50 microns, which allows a good centering effect of the centering electrodes 6, 7.

In operation, the manipulation electrodes 4, 5 are electrically driven in opposite phase to each other, as well as the centering electrodes 6, 7 are electrically driven in opposite phase to each other. In addition, the centering electrode 6 is also driven in phase opposition to the associated manipulation electrode 4, just as the centering electrode 7 is also driven in antiphase to the associated manipulation electrode 5. In this way, the suspended biological cells 2 are focused in the carrier flow channel 1 in the central plane, whereby a contact contact of the biological cells 2 with the channel walls of the carrier flow channel 1 is prevented.

However, the centering electrodes 6, 7 and the manipulation electrodes 4, 5 do not have to be controlled exactly in antiphase (ie with a phase shift of 180 °). Rather, other phase shifts are possible within the scope of the invention. This phase shift may be arbitrary between the electrodes at the upper channel wall and at the lower channel wall, said shift generally being between 90 ° and 270 °. For electrodes in a plane, for example, manipulation and centering electrode on the upper channel wall, the displacement is generally in the range of 135 ° -225 ° (180 ° + 45 °). In addition, the centering electrodes 6, 7 and the manipulation electrodes 4, 5 can also be driven with different frequencies and voltages, as will be described in detail later.

FIGS. 3A-3D show different views of the electrode arrangement 3 in the case of the microfluidic system according to the invention, FIGS. 3B-3C showing the respective electric field distribution. FIGS. 3A and 3B show a plan view of the electrode arrangement 3 in the z-direction, while FIGS. 3C and 3D reproduce sectional images in the y-z plane and the x-z plane, respectively.

FIGS. 2A-2D show, for comparison, corresponding views in a conventional electrode arrangement without the centering electrodes 6, 7. It can thus be seen that the biological cells 2 are pressed in the direction of the channel wall in the conventional electrode arrangement, in particular from FIGS. 2C and 2D is apparent. In contrast, the biological cells 2 in the inventive

Electrode arrangement 3 centered, as can be seen in particular from Figures 3C and 3D.

FIGS. 4A and 4B show an alternative embodiment of an inventive electrode arrangement with semicircular manipulation electrodes 8, wherein the illustrations on the left side show a corresponding conventional electrode arrangement without centering electrodes, while the illustration on the right side shows the field distribution in an electrode arrangement according to the invention with a centering electrode 9 show. It can also be seen from these illustrations that the centering electrode 9 has centering of the biological cells 2 in the central plane of the carrier power cable. nals 1 and additionally causes a fixation against the flow in the x direction.

Finally, FIGS. 5A and 5B show an alternative exemplary embodiment of an electrode arrangement according to the invention, in which an annular manipulation electrode (with rim 10, 11) and also a concentric, centrally arranged centering electrode 12 are provided. The manipulation electrode (10, 11) and the centering electrode 12 are in this case arranged in a common plane on the upper channel wall or on the lower channel wall of the carrier flow channel 1 and thus aligned coplanar. The biological cells 2 can be arranged in this embodiment on closed tracks, as can be seen in particular from the illustration in Figure 5A.

Figures GA-6C show further alternative embodiments of electrode assemblies according to the invention 13, 13 'and 13 ", each having a manipulation electrode 14, 14', or 14" and a centering electrode 15, 15 ', 15 ".

In the carrier flow channel 1, such an electrode arrangement 13, 13 'or 13 "is respectively arranged on the upper channel wall and on the lower channel wall.

FIGS. 7A and 7B show further exemplary embodiments of electrode arrangements 16 and 17 according to the invention, in which a plurality of hook-shaped manipulation electrodes 18-21 are arranged next to one another in the carrier flow channel 1 in the flow direction. Upstream of the individual manipulation electrodes 18-21, in each case a centering electrode 22-25 is arranged in order to center the biological cells 2 in the central plane of the carrier flow channel 1. The difference between the embodiments according to FIGS. 7A and 7B consists in the electrical supply of the manipulation electrodes 18-21 and the centering electrodes 22-25.

Thus, the manipulation electrodes 18-21 of the electrode assembly 16 are electrically driven together according to Figure 7A and are therefore electrically connected to each other. In contrast, in the case of the electrode arrangement 17 according to FIG. 7B, the manipulation electrodes 18-21 are electrically separated from one another, so that the manipulation electrodes 18-21 are also not electrically connected to one another.

In contrast, in the case of the electrode arrangement 16 according to FIG. 7A, the centering electrodes 22-25 are electrically driven together, which is also the case with the electrode arrangement 17 according to FIG. 7B.

In the carrier flow channel of the microfluidic system according to the invention, several of the electrode arrangements 16 and 17 illustrated in FIGS. 7A and 7B can also be arranged one behind the other in the flow direction. This provides the ability to store particles in defined arrays.

Several electrode arrangements according to FIG. 7A / B can be found in FIG

Flow direction can be arranged one behind the other so as to be able to store particles in defined arrays.

Finally, Figure 8 shows a diagram showing the functional dependence of several different sizes on the electrode width and the electrode spacing.

A curve 26 indicates the dependence of the heating ΔT of the suspended biological cells 2 as a function of the ratio between electrode width and electrode spacing between the planes at constant voltage again. It can be seen from the course of the curve 26 that the heating ΔT of the suspended cells 2 increases with the electrode width and decreases with the electrode spacing. It should be noted that the heating of the biological cells 2 by the dielectrophoretic electrode arrangement for the biological cells 2 can be harmful and therefore undesirable.

In contrast, a further curve 27 shows the dependence of the force F exerted on the biological cell 2 by the dielectrophoretic electrode arrangement as a function of the ratio of the electrode width to the electrode spacing. It can be seen from the course of the curve 27 that the exerted force F increases with the electrode width and decreases with the electrode spacing.

Finally, another curve 28 shows the ratio of the desired force F to the unwanted heating ΔT of the suspended cells as a function of the ratio of electrode width to electrode gap. It can be seen from the course of the curve 28 that a certain operating range is particularly advantageous, in which the ratio of electrode width to electrode gap is approximately between 0.15 to 0.5. In this region, the force exerted by the electrode assembly on the suspended particles is relatively large relative to the undesirable heating ΔT.

FIGS. 9A to 9E show further exemplary embodiments of electrode arrangements which can be used in a microfluidic system according to the invention. The individual electrode arrangements each consist of a centering electrode 29 and a manipulation electrode 30. The centering electrode 29 would thus take the place of the centering electrodes 6 and 7 in the embodiment according to FIG. 1, while the manipulation electrode 30 replaces the manipulation electrodes 4 and 5.

The different electrode arrangements according to FIGS. 9A to 9E differ here by the shape of the centering electrode 29.

Thus, the centering electrode 29 can be rectangular, triangular, drop-shaped, angular or box-shaped, as can be seen from the various figures.

Furthermore, FIG. 10 shows different views of a further exemplary embodiment of an electrode arrangement in a microfluidic system according to the invention. This embodiment is largely consistent with the embodiment described above and shown in Figures 1 and 3, so reference is made to avoid repetition of the above description.

A special feature of this embodiment is that the upper manipulation electrode 4 is arranged offset in the flow direction with respect to the lower manipulation electrode 5.

In the same way, the upper centering electrode 6 is offset relative to the lower centering electrode 7 in the flow direction. The offset here corresponds to half the distance between the manipulation electrodes 4, 5 and the associated centering electrodes 6, 7.

The images on the left side of FIG. 10 show field distributions that arise when the manipulation electrodes 4, 5, on the one hand, and the centering electrodes, on the other hand, are driven with the same electrical voltage.

On the right side in FIG. 10, on the other hand, field distributions are shown which arise when the centering electrodes 6, 7 are driven with a voltage three times as high as the manipulation electrodes 4, 5.

Furthermore, FIG. 11 shows different views of a further exemplary embodiment of an electrode arrangement in a microfluidic system according to the invention. This embodiment is largely consistent with the embodiment described above and shown in Figures 1 and 3, so reference is made to avoid repetition of the above description.

A special feature of this embodiment is that on the other hand there is a phase shift of 90 ° between the manipulation electrode 4 and the centering electrode 6 on the upper channel wall on the one hand and the manipulation electrode 5 and the centering electrode 7 on the lower channel wall.

In addition, the manipulation electrodes 4, 5 on the one hand and the centering electrodes 6, 7 on the other hand driven with a phase shift of 90 °. This is shown in the left column of FIG. The right-hand column, on the other hand, shows an out-of-phase drive, but using a square centering electrode.

Furthermore, FIG. 12 shows different views of a further exemplary embodiment of an electrode arrangement in a microfluidic system according to the invention. This embodiment is largely consistent with the embodiment described above and shown in Figures 1 and 3, so reference is made to avoid repetition of the above description.

A special feature of this embodiment is that the manipulation electrodes 4, 5 on the one hand and the centering electrodes 6, 7 on the other hand are driven with different frequencies.

In this case, the images in the left-hand column show the field distribution for the case in which the manipulation electrodes 4, 5 and the centering electrodes 6, 7 are driven with the same voltage values, the drive frequency Fl or F2 being selected such that the cells 2 are equal experience strong polarization in both fields.

On the other hand, in the images in the right column, the polarization of the particle relative to the medium at the frequency F2 is only 1/4 of the polarization at the frequency Fl.

Even when controlled with two different (not necessarily consumable) frequencies Fl, F2, the cells 2 are focused in the Z direction. At moderate voltages, however, they are not kept central in the horizontal XY central plane, but can be balanced with the hydrodynamic force are held in two positions. This allows two more new modes of operation:

On the one hand, switching to control with a uniform frequency or absolute or relative

Weakening of the manipulation electrodes (lower voltage, frequency change, increase in the flow rate) two cells 2 or particles are supplied to each other or separated by the reverse process from each other, if the binding fertil not too strong. This can be exploited to determine binding constants and / or to selectively activate and / or influence cells, in particular immune cells.

On the other hand, by varying one of the two frequencies Fl, F2 from the change in position of the cells 2 to their dielectric properties can be inferred (in the pictures in the right column, the two cells 2 are further apart). This makes the dielectrophoresis spectrum easily accessible.

The exemplary embodiment according to FIGS. 13A and 13B corresponds largely to the exemplary embodiments described above and to FIGS. 5A and 5B, so that reference is made to the above description for avoiding repetitions, the same reference numerals being used for corresponding components.

A special feature of this embodiment is the diameter of the manipulation electrode 10, which is lower compared to the embodiment according to Figures 5A, 5B.

It should also be mentioned that the manipulation electrodes 10, 11 on the one hand and the centering electrode 12 on the other hand be driven in opposite phase in this embodiment, as can be seen from the phase indication in Figure 13B.

In addition, in this embodiment also follows an opposite-phase control of the electrodes on the upper channel wall on the one hand and on the -unteren channel wall on the other. Thus, the manipulation electrode 10 on the upper channel wall on the one hand and the manipulation electrode 10 are driven in anti-phase to the lower channel wall. In the same way, the centering electrodes 12 on the upper channel wall are driven in opposite phase to the centering electrodes 12 on the lower channel wall.

The electric fields are formed in this electrode structure in such a way that the cells 2 are caught centrally and not on a ring, as in FIG. 5.

The exemplary embodiment according to FIGS. 14A and 14B corresponds largely to the exemplary embodiment described above and illustrated in FIGS. 13A and 13B, so that reference is made to the above description for avoiding repetitions, the same reference numerals being used for corresponding components.

A special feature of this embodiment is that the centering electrodes 12 are connected to ground. As a result, the trapped cells 2 are brought in the Z direction in the vicinity of the manipulation electrode 10 and thus in flow-stabilized zones. This has the advantage that a stable holding in free solution can be realized with reduced electrical (heating) power.

The exemplary embodiment according to FIGS. 15A and 15B again largely agrees with that described above and in FIG 14A and 14B illustrated embodiment, so reference is made to avoid repetition of the above description, wherein the same reference numerals are used for corresponding components.

A special feature of this embodiment is the electrical control of the centering electrodes 12 on the upper side and the underside of the carrier current channel. Thus, the control of the centering electrode 12 at the upper channel wall is performed with ground, while the centering electrode 12 is driven at the lower channel wall in opposite phase to the upper manipulation electrode 10 as can be seen from the phase indication in Figure 15B.

The exemplary embodiment according to FIGS. 16A and 16B corresponds largely to the exemplary embodiment described above and illustrated in FIGS. 13A and 13B, so that reference is made to the above description for avoiding repetitions, the same reference numerals being used for corresponding components.

A special feature of this embodiment is that the manipulation electrode 10 consist of four annular segment-shaped electrode segments 3IA, 31B, 31C and 31D. The individual electrode segments 31A-31D are in this case electrically connected to each other and therefore only spatially separated from each other so that the trapped cells 2 can more easily enter and leave the X-direction and Y-direction in the field cage.

Again, the embodiment according to FIGS. 17A and 17B largely corresponds to the exemplary embodiments described above, so that reference is made to the above description in order to avoid repetition, wherein FIG the same reference numerals are used for corresponding components.

A special feature of this embodiment is the electrical control of the manipulation electrode 10 and the centering electrodes 12.

The manipulation electrode 10 at the top of the channel wall and the manipulation electrode 10 at the bottom of the channel wall, however, are driven in this embodiment with a phase difference of 90 °.

In addition, in this embodiment, the two centering electrodes 12 are driven in opposite phase at the top or at the bottom of the carrier flow channel. In this way, rotation fields are generated in the field cage.

FIG. 18 shows a matrix-like arrangement of a multiplicity of circular or annular electrode arrangements 32, the individual electrode arrangements 32 each having manipulation electrodes and centering electrodes, as described above. The individual electrode arrangements 32 are actuated by line control lines 33 and column control lines 34. In order to switch off a specific electrode arrangement 32, the associated row control lines 33 and the associated column control lines 34 are switched to ground or free potential , With this, all the cells remain fixed with the exception of the cell held in the relevant electrode arrangement 32. In the affected electrode assembly 32, however, all electrodes are grounded, so that the particles therein can leave the associated electrode assembly 32 with the carrier flow. FIGS. 19A-19C show different variants of electrode arrangements according to the invention with centering electrodes 35 and manipulation electrodes 36, the manipulation electrodes 36 each consisting of four segments surrounding the centering electrode 35.

In addition, the manipulation electrodes 36 still have funnel-shaped electrode arrangements ("funnel"), as described initially in the description of the state of the art

Technique were explained. These funnel-shaped electrode arrangements facilitate the entry of particles into the electrode structure.

Finally, FIG. 20 shows a multiplicity of electrode arrangements which largely correspond to the electrode arrangements according to FIGS. 19A-19C, so that reference is made to the above description to avoid repetition, the same reference symbols being used for corresponding components. ¹

A special feature of this embodiment is that downstream of the individual electrode arrangements, in each case particle switches 37 are arranged, which make it possible to selectively convey the exiting particles into the downstream electrode structure or to deflect them laterally.

The invention is not limited to the exemplary embodiments described above. Rather, a variety of variants and modifications is possible, which also make use of the inventive idea and therefore fall within the scope. LIST OF REFERENCE NUMBERS

1 carrier flow channel

2 cell

3 electrode arrangement

4, 5 manipulation electrodes

6, 7 centering electrodes

8 manipulation electrodes

9 centering electrode

10, 11 manipulation electrodes

12 centering electrode

13, 13 ', 13 "electrode arrangement

14, 14 ', 14' 'manipulation electrode

15, 15 ', 15' 'centering electrode

16, 17 electrode arrangements 18-21 manipulation electrodes 22-25 centering electrodes

26-28 turns

29 centering electrode

30 manipulation electrode 31A-31D electrode segments

32 electrode arrangements

33 line control lines

34 column control lines

35 centering electrode

36 manipulation electrode

37 Particle switch

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Claims

1. Microfluidic system with a) a carrier flow channel (1) for receiving a carrier stream with particles (2) suspended therein, b) at least one electrode arrangement (3, 13, 16, 17) arranged in the carrier flow channel (1) for manipulating the suspended particles (2), c) wherein the electrode assembly (3, 13, 16, 17) at least two manipulation electrodes (4, 5, 8, 10, 11, 14, 14 ', 14 ", 18-21), characterized , d) that the electrode arrangement (3, 13, 16, 17) in addition to the two manipulation electrodes (4, 5, 8, 10, 11, 14, 14 ', 14 ", 18-21) at least two centering electrodes (6, 7 , 12, 15, 15 ', 15 ", 22-25) in order to center the suspended particles (2) at right angles to the flow direction, e) that the centering electrodes (6, 7, 12, 15, 15', 15 ", 22-25) in the carrier flow channel (1) in each case at least partially upstream of one of the two manipulation electrodes (4, 5, 8, 10, 11, 14, 14 ', 14", 18-21) are arranged, f) that the centr at least partially enclosed by the manipulation electrodes (4, 5, 8, 10, 11, 14, 14 ', 14 ", .18-21) are.

2. Microfluidic system according to claim 1, characterized in that the centering electrodes (6, 7, 12, 15, 15 ', 15 ", 22-25) transverse to the flow direction, a smaller spatial extension than the manipulation electrodes (4, 5, 8, 10, 11, 14, 14 ', 14'', 18-21).

3. Microfluidic system according to one of the preceding claims, characterized in that the manipulation electrodes (4, 5, 8, 10, 11, 14, 14 ', 14' ', 18-21) are curved counter to the flow direction.

4. Microfluidic system according to one of the preceding claims, characterized in that the manipulation electrodes (4, 5, 8, 10, 11, 14, 14 ', 14' ', 18-21) are arcuate, hook-shaped or annularly closed.

5. Microfluidic system according to one of the preceding claims, characterized in that the electrode arrangement (16, 17) has a plurality of manipulation electrode pairs (18-21) and their associated Zentrierelektrodenpaare (22-25).

6. microfluidic system according to claim 5, characterized in that the Zentrierelektrodenpaare (22-25) at least partially electrically connected to each other and at least partially electrically driven together and / or that the manipulation electrode pairs (18-21) at least partially electrically connected to each other and at least partially Electrically driven together.

7. Microfluidic system according to claim 5 or β, characterized in that the centering electrodes (22-25) and / or the manipulation electrodes (18-21) in the carrier flow channel (1) are arranged side by side with respect to the flow direction. 8. Microfluidic system according to one of the preceding claims, characterized in that the manipulation electrodes (4, 5,

8, 10, 11, 14, 14 ', 14' ', 18-21) are arranged at a certain electrode distance from each other and have a certain lateral electrode width, wherein the electrode width is in the range of 10% to 50% of the electrode distance.

9. Microfluidic system according to one of the preceding claims, characterized in that the two centering electrodes (6, 7, 12, 15, 15 ', 15' ', 22-25) are electrically controlled separately from each other.

10. Microfluidic system according to one of the preceding claims, characterized in that the two manipulation electrodes (4, 5, 8, 10, 11, 14, 14 ', 14' ', 18-21) are electrically controllable separately from each other.

11. Microfluidic system according to one of the preceding claims, characterized in that the two manipulation electrodes (4, 5, 8, 10, 11, 14, 14 ', 14' ', 18-21) separated from the centering electrodes (6, 7, 12, 15, 15 ', 15' ', 22-25) are electrically controllable.

12. Microfluidic system according to one of the preceding claims, characterized in that the two manipulation electrodes (4, 5, 8, 10, 11, 14, 14 ', 14' ', 18-21) and / or the two centering electrodes (6, 7, 12, 15, 15 ', 15 ", -22-25) are each substantially planar.

13. Microfluidic system according to one of the preceding claims, characterized in that the two manipulation electrodes (4, 5, 8, 10, 11, 14, 14 ', 14'', 18-21) on the one hand and the two centering electrodes (6, 7 , 12, 15, 15 ', 15'', 22-25) on the other hand are arranged in pairs coplanar.

14. Microfluidic system according to one of the preceding claims, characterized in that the centering electrodes (6, 7, 12, 15, 15 ', 15' ', 22-25) and the manipulation electrodes (4, 5, 8, 10, 11, 14, 14 ', 14 ", 18-21) have a distance in the direction of flow which is in the range of 1/8 to twice the channel height, therefore in particular for a 40 μm high channel in the range of 5 μm to 80 ° μm is located.

15. Microfluidic system according to one of the preceding claims, characterized in that the carrier flow channel (1) has a flow cross-section which is in the range of up to 0.006 mm ² to 0.6 mm ² .

16. Microfluidic system according to one of the preceding claims, characterized in that the carrier flow channel (1) has a height in the range of 1 micron to 400 microns and / or a width in the range of 5 microns to 1.5 mm.

17. Microfluidic system according to one of the preceding claims, characterized in that the electrode arrangement (3, 13, 16, 17) is a dielectrophoretic electrode arrangement.

18. Microfluidic system according to one of the preceding claims, characterized in that the centering the (6, 7, 12, 15, 15 ', 15'', 22-25) and / or the manipulation electrodes round, circular, elliptical, rectangular , triangular or teardrop-shaped.

19. Microfluidic system according to claim 18, characterized in that the centering electrodes surround the manipulation electrodes in an annular manner.

20. Microfluidic system according to claim 18 or 19, characterized in that the annular centering electrodes have a plurality of circular ring segments, which are galvanically connected to each other and spatially separated from each other.

21. Microfluidic system according to one of the preceding claims, characterized in that the two coplanar arranged manipulation electrodes (4, 5) and / or the two centering electrodes (6, 7) of the electrode assembly (3) are arranged offset to one another in the flow direction.

22. Microfluidic system according to one of the preceding claims, characterized by a plurality of electrode arrangements, each having at least two manipulation electrodes and in each case at least two centering electrodes, wherein the individual electrode arrangements are arranged in matrix form in rows and columns.

23. Microfluidic system according to claim 22, characterized in that - at least one of the individual lines

Control line is provided, which is connected to the electrode assemblies of the respective row and controls them together, but independently of the electrode arrangements of the other rows, and - that for each column at least one

Control line is provided which is connected to the electrode assemblies of the respective column and controls them together, but independently of the electrode arrangements of the other columns,

24. Cell sorter with a microfluidic system according to one of the preceding claims.

25. A driving method for an electrode assembly (3, 13, 16, 17) in a microfluidic system with two manipulation electrodes (4, 5, 8, 10, 11, 14, 14 ', 14 ", 18-21) and two upstream of the Manipulation electrodes (4, 5, 8, 10, 11, 14, 14 ', 14 ", 18-21) arranged centering electrodes (6, 7, 12, 15, 15', 15", 22-25), wherein the centering electrodes ( 6, 7, 12, 15, 15 ', 15 ", 22-25) in the carrier flow channel (1) in each case at least partially upstream of one of the two manipulation electrodes (4, 5, 8, 10, 11, 14, 14', 14 ", 18-21) are arranged and enclosed by this, characterized in that the manipulation electrodes (4, 5, 8, 10, 11, 14, 14 ', 14", 18-21) and their associated centering electrodes (6, 7, 12, 15, 15 ', 15 ", 22-25) are electrically driven in anti-phase or single-phase.

26. A driving method according to claim 25, characterized in that the centering electrodes (6, 7, 12, 15, 15 ', 15 ", 22-25) have a smaller spatial extent in the carrier flow channel transversely to the flow direction than the manipulation electrodes (4 , 5, 8, 10, 11, 14, 14 ', 14 ", 18-21)

27. Control method according to claim 25 or 26, characterized in that in two parallel planes in each case a manipulation electrode and an associated centering electrode is arranged, wherein the manipulation electrodes and the centering electrodes are controlled with a phase shift of 90 ° between the planes.

28. A driving method according to any one of claims 25 to 27, characterized in that the centering electrodes (6, I ₁ 12, 15, 15 ', 15'', 22-25) are turned off when a particle (2) from the manipulation electrodes ( 4, 5, 8, 10, 11, 14, 14 ', 14 ", 18-21) has been fixed.

29. A driving method according to any one of claims 25 to 28, characterized in that the centering electrodes (6, 7, 12, 15, 15 ', 15' ', 22-25) is switched to shutdown to ground or potential-free.

30. A driving method according to any one of claims 25 to 29, characterized in that the centering electrodes (6, 7, 12, 15, 15 ', 15' ', 22-25) are briefly controlled before their shutdown with an increased electrical voltage.

31. A driving method according to any one of claims 25 to 30, characterized in that the flow velocity in the carrier flow channel (1) before switching off the centering electrodes (6, 7, 12, 15, 15 ', 15' ', 22-25) is briefly increased.

32. A driving method according to any one of claims 25 to 31, characterized in that the centering electrodes (6, 7, 12, 15, 15 ', 15' ', 22-25) are used as impedance measuring electrodes.

33. Control method according to one of claims 25 to 32, characterized in that the centering electrodes (6, 7) on the one hand and the manipulation electrodes (4, 5) on the other hand with different voltages and / or frequencies and / or with an adjustable phase position are controlled to each other.

34. Use of a microfluidic system according to one of claims 1 to 23 in a cell sorter.

35. Use of the microfluidic system according to one of claims 1 to 23 for the determination of dielectric properties of particles.

36. Use of the microfluidic system according to one of claims 1 to 23 for cell activation and / or influencing of cells.

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