WO2008055641A1

WO2008055641A1 - Field cage and associated operating method

Info

Publication number: WO2008055641A1
Application number: PCT/EP2007/009579
Authority: WO
Inventors: Thomas Schnelle; Torsten Müller
Original assignee: Evotec Technologies Gmbh
Priority date: 2006-11-09
Filing date: 2007-11-05
Publication date: 2008-05-15
Also published as: EP2069071A1; DE102006052925A1

Abstract

The invention relates to a field cage (1) for spatially fixing suspended particles (10) by means of an electrical captive field, with at least six cage electrodes (2 - 9) for producing the captive field, wherein the cage electrodes (2 - 9) have at least two different phase angles, and at least one electrode plane, in which a plurality of the cage electrodes (2 - 9) are arranged, wherein the electrode plane is aligned substantially at right angles with respect to an external force of gravity (g). The invention proposes that two directly adjacent cage electrodes (2 - 9) have the same phase angle in the electrode plane. Furthermore, the invention comprises a corresponding operating method.

Description

DESCRIPTION

Field cage and associated operating method

The invention relates to a field cage for the spatial fixation of suspended particles by an electric capture field and an associated operating method.

From Müller, T. et al .: "A 3-D microelectrode system for handling and caging single cells and particles", Biosensors & Bioelectronics, 1999, Volume 14, no. 3, pp 247-256 microfluidic systems are known which have a carrier flow channel in which a carrier stream with suspended therein

Particles (e.g., biological cells) flow, whereby the suspended particles in the microfluidic system can be examined and manipulated. For this purpose, so-called field cages are arranged in the carrier flow channel, which generate a dielectrophoretic capture field which spatially fixes the suspended particles in the field cage, which allows manipulation and examination of the suspended particles in the fixed state.

FIGS. 1 and 2 show different operating modes of such a conventional field cage 1 with eight cage electrodes 2-9, which are arranged cubically and can be electrically controlled independently of one another in order to generate a capture field by means of dielectrophoresis, which contains a suspended particle 10 fixed a specific focal height H _F above the lower channel wall of the carrier flow channel.

FIG. 1 shows a conventional control of the individual cage electrons 2-9, which is also referred to as the RED mode is because the suspended particle 10 is not only fixed in the field cage 1, but also rotated. For this purpose, the cage electrodes 2-5 in the upper electrode plane and the cage electrodes 6-9 in the lower electrode plane so controlled that in the circumferential direction adjacent cage electrodes 6-9 each have a phase difference of 90 °, as can be seen from the phase information in Figure 1 is.

By contrast, FIG. 2 shows a conventional operating mode of the cage, which is also referred to as the ACC mode and merely leads to a spatial fixation of the particle 10 in the field cage 2, without a rotation of the fixed particle 10 taking place. For this purpose, the cage electrodes 2-5 in the upper electrode plane and the cage electrodes 6-9 in the lower electrode plane in each case in the circumferential direction with a phase difference of 180 ° between the adjacent cage electrodes 2-5 and 6-9 are driven, as from the phase information can be seen in Figure 2.

A disadvantage of the known ACC mode is the fact that the focal height H _{F of} the particle 10 in the field cage 1 depends on the particle size, so that particles 10 of different sizes are fixed in the field cage 1 at different positions within the field cage 1. This is particularly troublesome if, for examining the fixed particles, 10 optical examination methods are to be used which have a specific focal point.

Another disadvantage of the known ACC mode is that only those particles are reliably fixed in the field cage 1, which are sufficiently large.

In addition, in the ACC mode there is a risk that particles outside the field cage 1 near or between one above the other cage electrodes 2-9 are fixed (see middle figures in Figure 4). On the one hand, this is problematic since the particles are generally not recognized there by conventional examination methods. On the other hand, when the field cage 1 is shut off, the particles fixed outside the field cage 1 are released together with the particles 10 fixed in the field cage 1, which can lead to contamination if, after an examination in the field cage, the particles are divided into different channels or channels Flow paths should be sorted.

Although the above-described ROT mode does not have these disadvantages, the RED mode inevitably leads to a rotation of the suspended particles and is therefore only suitable for extremely fast examination methods, in which the examination result is not impaired by the particle rotation.

The invention is therefore based on the object to improve the well-known field cages accordingly.

This object is achieved by a field cage according to the invention and an associated operating method according to the independent claims.

The invention is based on a field cage which has at least six cage electrodes in order to generate a capture field for the spatial fixation of suspended particles, wherein the cage electrodes have at least two different phase positions.

Furthermore, the field cage according to the invention has at least one electrode plane in which a plurality of the cage electrodes are arranged, wherein the electrode plane is aligned substantially perpendicular to an external gravity.

The invention provides that in the electrode plane two directly adjacent cage electrodes have the same phase position. This feature is based on the technical knowledge gained by the inventors for the first time that in this way the focus height in the field cage is essentially independent of the particle size. This has the advantage that the particles having the same specific physical properties (density, conductivity, polarizability) in the field cage according to the invention are fixed at a certain point, which is also referred to as the focal point, irrespective of their particle size. In a study of the fixed particles by microscopic or other examination methods, the focus of the investigation method can therefore be set exactly to the focal point of the field cage, without depending on the particle size adjustment is required.

The definition of immediately adjacent cage electrodes used in the context of the invention means that these cage electrodes follow one another directly in a closed polygon in a common electrode plane along the traverse.

Preferably, in the field cage according to the invention at least two electrodes are arranged in each electrode plane. For example, the field cage according to the invention can have two parallel electrode planes, in each of which four cage electrodes are arranged. In another example of a field cage according to the invention, on the other hand, four cage electrodes are arranged in one electrode plane and two cage electrodes are arranged in the other electrode plane. The invention However, in terms of the distribution of the individual cage electrodes on the different electrode levels is not limited to these two examples, but also feasible in other ways.

In addition to the force of gravity, the particles in a microsystem generally also have an additional additional external force, which is oriented substantially perpendicular to the gravitational force and is generated, for example, by a hydrodynamic flow. The additional external force is then aligned parallel to the flow direction in the carrier flow channel of the microfluidic system. In the field cage according to the invention then act on the suspended particles at least three different forces, namely gravity, the hydrodynamic flow force and the fixing force of the field cage, which is usually produced by dielectrophoresis.

In a preferred exemplary embodiment, the field cage according to the invention has a plane of symmetry in which a plurality of the cage electrodes are arranged and with respect to which the cage electrodes of the individual phase layers are each arranged symmetrically, the plane of symmetry being inclined with respect to gravity. For example, the cage electrodes lying in the plane of symmetry on the one hand and the cage electrodes arranged outside the plane of symmetry, on the other hand, can be driven in antiphase fashion.

The individual cage electrodes are in this case arranged symmetrically with respect to the symmetry plane in the sense that the individual cage electrodes are each imaged by mirroring on the plane of symmetry onto an in-phase cage electrode. In this case, the plane of symmetry preferably has an angle of inclination between 10 ° and 80 ° with respect to gravity, with any values and subregions within this interval being possible. For example, the angle of inclination between 30 ° and 60 ° or between 40 ° and 50 °, with an inclination angle of 45 ° is particularly advantageous.

Experiments by the inventors have shown that the symmetry principle mentioned above offers the advantage that the focus height is essentially independent of the particle size.

In a preferred embodiment of the invention, the plane of symmetry is oriented substantially parallel to the additional external force and therefore preferably runs parallel to the hydrodynamic force or to the longitudinal axis of the carrier flow channel.

Preferably, the field cage has exactly eight cage electrodes, which are each arranged at the corners of a hexahedron, in particular a cube.

In another variant of the invention, however, the field cage on six cage electrodes, which are each arranged at the corners of a pentahedron.

However, the invention is not limited to hexahedron or pentahedron in terms of the spatial arrangement of the cage electrodes, but in principle also feasible with other arrangements.

It should also be mentioned that all cage electrodes of the field cage according to the invention can have the same voltage amplitude. However, there is also the alternative possibility that the cage electrodes have different voltage amplitudes. For example, the ratio of the voltage amplitudes of the cage electrodes in the upper electrode plane on the one hand and the cage electrodes in the lower electrode plane on the other hand can be varied to adjust the focal height.

In the eight-cage electrode variant mentioned above, four of the cage electrodes may be in the plane of symmetry, while the other four cage electrodes may be outside the plane of symmetry.

The cage electrodes lying in the plane of symmetry then preferably have a common phase position (e.g., 180 °), as well as the off-symmetry plane cage electrodes preferably have a common phase (e.g., 0 °). On the other hand, the cage electrodes lying in the plane of symmetry on the one hand and the cage electrodes lying outside the plane of symmetry, on the other hand, are preferably in the opposite phase, ie. they have a phase difference of 180 °.

In this case, there is also the possibility that the cage electrodes lying in the plane of symmetry have a common phase position, while the cage electrodes lying outside the plane of symmetry are grounded and therefore inevitably have a common phase position as well.

Furthermore, it is advantageous if the connecting lines between the cage electrodes with the same phase angle are inclined in each case by a predetermined angle, preferably 90 °, with respect to gravity. In addition, in a variant of the invention, a plane of symmetry is present with respect to which the cage electrodes of the individual phase layers are each arranged antisymmetrically. In the context of the invention, this means that the individual cage electrodes are respectively imaged onto an opposite-phase cage electrode when mirrored at the plane of symmetry. For example, a cage electrode with a phase angle of 0 ° is then imaged at a mirroring on the plane of symmetry onto another cage electrode with a phase angle of 180 °. The plane of symmetry in this case preferably runs parallel to the force of gravity.

It should also be mentioned that the cage electrodes are arranged in at least one of the electrode planes in each case at the corners of a closed polygon, which is necessarily the case with a cubic arrangement.

The invention comprises not only the field cage according to the invention described above, but also a microfluidic system with such a field cage for fixing suspended particles in a carrier flow channel of the microfluidic system.

Furthermore, the invention also encompasses a device, in particular a particle sorter, with such a microfluidic system. The device according to the invention has a control unit which activates the individual cage electrodes of the field cage according to the invention with the phase positions described above.

Finally, the invention also encompasses a corresponding operating method for controlling the individual cage electrodes of the field cage according to the invention, as already evident from the above description. In the context of the operating method according to the invention, the field cage can also be operated alternately in the novel ACCY mode and in the known ROT mode. In the ACCY mode, the fixed particle can then be examined without particle rotation. To examine the particle from a different perspective, a RED mode can then be turned on to rotate the fixed particle in the field cage.

Furthermore, various investigation methods can be used within the scope of the operating method according to the invention, such as, for example, light microscopy, impedance spectroscopy or ultrasound microscopy, to name only a few.

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:

Figure 1 is a perspective view of a conventional

Field cage in the so-called RED mode,

Figure 2 shows the field cage of Figure 1 in the so-called

ACC mode,

FIG. 3 shows a preferred embodiment of the field cage according to the invention,

FIG. 4 shows field distributions in the field cages according to FIGS. 1-3, FIG. 5 shows a force diagram which illustrates the power contributions in the various operating modes,

FIG. 6 shows a diagram showing the focal point as a function of the voltage ratio between the upper electrode plane and the lower electrode plane,

7 shows a greatly simplified perspective view of a microfluidic system according to the invention with a field cage according to the invention, FIG.

FIG. 1 shows another embodiment of a field cage according to the invention with a different orientation to the flow force, FIG.

FIG. 9 shows an exemplary embodiment of a field cage according to the invention with six cage electrodes,

FIGS. 10A-10D show the field distribution in the field cage according to FIG

FIG. 9,

FIGS. 11A-11C show the field distribution in the field cage according to FIG

FIG. 9 with enlarged center electrodes,

Figures 12A-12C, the field distribution in the field cage according to

FIG. 9 during a rotation control of the field cage.

The field cage according to the invention according to FIG. 3 corresponds in part to the conventional field cages described above and shown in FIGS. 1 and 2, so that Reference is made to avoid repetition of the above description, wherein the same reference numerals are used for corresponding elements.

An essential difference of the field cage according to the invention according to FIG. 3 is the different phase position of the individual cage electrodes 2-9. Thus, the two cage electrodes 2, 3 in the upper electrode plane on the one hand and the two cage electrodes 8, 9 in the lower Elektrodenebe- ne in phased with a phase angle of 0 ° are driven. By contrast, the two cage electrodes 4, 5 in the upper electrode plane on the one hand and the two cage electrodes 6, 7 in the lower electrode plane are driven with a common phase position of 180 °. The cage electrodes 2-9 are thus arranged symmetrically with respect to a plane of symmetry 11 in the sense that the cage electrodes 2-9 are imaged by a reflection on the plane of symmetry 11 respectively on in-phase cage electrodes 2-9.

The plane of symmetry 11 is in this case aligned parallel to a flow force F _FLOW , which acts on the suspended particles 10 and is generated by the flow in a carrier flow channel of a microfluidic system.

In addition, the plane of symmetry 11 is inclined to an external gravity g by an inclination angle of 45 °.

FIG. 4 shows on the left the field distribution E ² in the field cage 1 according to FIG. 1 in the conventional ROT mode and in the middle the field distribution in the field cage 1 according to FIG. 2 in the known ACC mode. In contrast, on the right side, FIG. 4 shows the field distribution in the field cage 1 according to the invention according to FIG. 3 in the new, so-called ACCY mode. The pictures in the upper row show the field distribution in a central plane parallel to the XY plane. In contrast, the images in the lower row show the field distribution in a central plane parallel to the YZ plane.

Figure 5 shows a force diagram for a suspended in an aqueous medium having a specific electric resistance of 0.3 Sm ^"1 biological particle 10 (cell) having a size of 12 microns, in a field cage with 40 microns distance between electrodes according to FIG 4, when activated with a voltage amplitude of IV and a drive frequency of 0.7 MHz, the vertical axis being plotted with the force F acting on the suspended particles 10 in the field cage 1. The horizontal axis, on the other hand, is along the height 2 and for the ACCY mode according to FIG 3 and the RED mode according to Figure 1. The force diagram shows that the values for the ACC mode shown in FIG focussing force in the focal point is relatively weak even for 12 μm particles, since in this control the gradient of E ² in the central axis disappears, Only dielectrophoretic forces that are proportional to the fifth power of the particle radius become effective. On the other hand, since the sedimentation force is volume-dependent, the focal height depends strongly on the particle size. In contrast, in the novel ACCY mode and in the conventional ROT mode, the focus force has a relatively strong gradient at the focal point and the dielectric force is proportional to the particle volume, resulting in stabilization and fixation largely independent of the particle size.

FIG. 6 shows a further diagram in which the offset ΔZ of the focal point in the Z direction of the field cage 1 as a function of the voltage ratio between the voltage amplitude the cage electrodes 2-5 in the upper electrode plane on the one hand and the cage electrodes 6-9 in the lower electrode plane on the other hand is shown (with the influence of gravity was neglected).

FIG. 7 shows a greatly simplified example of a micro fluidic system 12 having a carrier flow channel with a rectangular cross section, in which a carrier flow with particles 10 suspended therein flows, wherein a field cage 1 according to the invention is arranged in the carrier flow channel.

FIG. 8 shows an alternative exemplary embodiment of a field cage 1 according to the invention, which largely corresponds to the exemplary embodiment according to FIG. 3, so that reference is made to the above description in order to avoid repetitions.

A special feature of this embodiment is the spatial orientation of the field cage 1 with respect to the outer flow force F _FLOW - Thus, the plane of symmetry 11 in the embodiment of Figure 3 is aligned parallel to the outer flow force F _FLOW , while the symmetry plane 11 in the embodiment of FIG the outer flow force F _FLOW is inclined at an angle of 45 °. This advantageously leads to the fact that the particles in the field cage 1 can be better fixed against the flow.

Figure 9 shows an alternative embodiment of a field cage 13 according to the invention with six cage electrodes 14-19, which are arranged in the form of a penta-leather. The cage electrodes 16-19 are in this case arranged in a lower electrode plane in each case at the corners of a square, while the cage electrodes 14, 15 are arranged in an upper electrode plane. Also this embodiment allows a fixation of suspended particles 20 in a certain focal height H _F above the lower electrode plane, wherein the focal height H _{f is} largely independent of the particle size.

FIGS. 10A-10C show the field profile in the field cage according to FIG. 9 in different sectional planes, as can be seen directly from the drawings.

FIGS. 11A-11C show the field profile in a modified embodiment of the field cage according to FIG. 9, in which the upper cage electrodes 14, 15 are enlarged in relation to the lower cage electrodes 16-19. This leads to the fact that the particle can be fixed in the channel center.

Finally, FIGS. 12A-12C show the field profile in the field cage 13 according to FIG. 9 during a rotation drive. The cage electrode 18 is driven at 0 °, the cage electrode 19 at 180 °, the cage electrode 16 at 300 ° and the cage electrode 17 at 120 °. The cage electrode 14 in the upper electrode plane, however, is driven at 60 °, while the cage electrode 15 is driven in the upper electrode plane at 240 °.

The invention is not limited to the preferred 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. Reference sign list:

I field cage

2-9 cage electrodes 10 particles

II symmetry plane

12 Microfluidic system

13 field cage 14-19 cage electrodes 20 particles

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Claims

1. Field cage (1; 13) for the spatial fixation of suspended particles (10; 20) by an electric trapping field, with a) at least six cage electrodes (2-9; 14-19) for generating the trapping field, wherein the cage electrodes ( 2-9, 14-19) have at least two different phase positions, b) at least one electrode plane in which a plurality of the cage electrodes (2-9, 14-19) are arranged, wherein the electrode plane is substantially perpendicular to an external gravity ( g) is aligned, characterized in that c) in the electrode plane two immediately adjacent cage electrodes (2-9, 14-19) have the same phase position.

2. Field cage (1; 13) according to claim 1, characterized in that the suspended particles (10; 20) are fixed in the field cage (1; 13) at a specific focal height (H _F ), the focal height (H _F ) being regardless of the size of the fixed particles (10; 20).

3. Field cage (1; 13) according to one of the preceding claims, characterized in that at least two cage electrodes (2-9; 14-19) are arranged in each electrode plane.

4. field cage (1; 13) according to one of the preceding Ansprü ^¬ che, characterized in that in addition a further external force (F _FLOW ) acts on the particles (10; 20), which is aligned substantially perpendicular to the gravitational force (g) is.

5. Field cage (1; 13) according to claim 4, characterized in that the additional external force (F _FL0W ) is generated by a hydrodynamic flow.

6. Field cage (1; 13) according to one of the preceding claims, characterized by: a) a plane of symmetry (11) in which a plurality of the cage electrodes (2-9) are arranged and with respect to which the cage electrodes (2-9) of the individual phase positions each symmetrically arranged, and b) an inclination of the plane of symmetry with respect to gravity (g).

7. field cage (1; 13) according to claim 6, characterized marked, that the plane of symmetry (11) with respect to gravity (g) with an inclination angle between 10 ° and 80 °, in particular between 30 ° and 60 °, in particular 45 ° , is inclined.

8. field cage (1; 13) according to one of claims 6 to 7, character- ized in that the plane of symmetry (11) is aligned substantially parallel to the additional external force (F _FL0W ).

9. Field cage (1; 13) according to one of the preceding claims, characterized in that a) that the field cage (1; 13) comprises eight cage electrodes (2-9), each at the corners of a hexahedron, in particular a cube, or b) that the field cage (1; 13) comprises six cage electrodes (14-19) each disposed at the corners of a penta-cher.

10. Field cage (1; 13) according to one of the preceding claims, characterized in that all the cage electrodes (2-9; 14-19) have the same voltage amplitude.

11. Field cage (1; 13) according to one of claims 9 to 10, characterized in that four of the cage electrodes (2-9) lie in the plane of symmetry (11), while the other four cage electrodes (2-9) lie outside the plane of symmetry ,

12. field cage (1; 13) according to claim 11, characterized in that a) that in the plane of symmetry (11) lying cage electrodes (2-9) have a common phase position, b) that the outside of the plane of symmetry (11) lying cage electrodes ( 2-9) have a common phase position, and c) that in the plane of symmetry (11) lying cage electrodes (2-9) on the one hand and the outside of the plane of symmetry (11) lying cage electrodes (2-9) on the other hand are in opposite phase.

13. Field cage (1; 13) according to claim 11 or 12, characterized in that a) that in the plane of symmetry (11) lying cage electrodes (2-9) have a common phase position, b) that outside the plane of symmetry (11 ) lying on ground cage electrodes (2-9).

14. Field cage (1; 13) according to one of the preceding claims, characterized in that the cage electrodes (2-9;

14-19) in the different electrode planes have either a) the same voltage amplitude or b) a different voltage amplitude.

15. Field cage (1; 13) according to one of the preceding claims, characterized in that the connecting lines between the cage electrodes (2-9; 14-19) with the same phase angle are each at a predetermined angle, preferably 90 °, with respect to the force of gravity (g ) are inclined.

16. field cage (1; 13) according to one of claims 1 to 6, characterized in that a) that a plane of symmetry is present, with respect to which the cage electrodes (2-9; 14-19) of the individual phase positions are each arranged antisymmetric, and b) that the plane of symmetry is parallel to gravity.

17. Field cage (1; 13) according to one of the preceding claims, characterized in that the cage electrodes (2-9; 14-19) are arranged in at least one of the electrode planes at the corners of a closed traverse.

18. A microfluidic system (12) with a field cage (1; 13) according to one of the preceding claims.

19. Particle sorter with a microfluidic system according to claim 18.

20. Operating method for a field cage (1; 13) with a plurality of cage electrodes (2-9; 14-19), in particular for a field cage (1; 13) according to one of claims 1 to 17, with the following step: activation of the individual cage electrodes (2-9, 14-19) with alternating current signals having at least two different phase positions, so that suspended particles (10; 20) in the field cage (1; 13) are spatially fixed by a trapping field, wherein in a perpendicular to an external gravity ( G) a plurality of cage electrodes (2-9, 14-19) are arranged, characterized in that at least two immediately adjacent cage electrodes (2-9; 14-19) are driven in phase in the electrode plane.

21. Operating method according to claim 20, characterized in that the suspended particles (10; 20) are fixed in the field cage (1; 13) at a certain focal height (H _F ), the focal height (H _F ) being independent of the size of the suspended particles (10; 20).

22. Operating method according to one of claims 20 to 21, characterized in are that a) that the cage electrodes (2-9) of the individual phase positions respectively with respect to (a plane of symmetry 11) symmet arranged ^¬ driven, b) that in the plane of symmetry (11) several of the cage selectors (2-9, 14-19) are arranged, and c) that the plane of symmetry (11) against gravity

(g) is inclined.

23. Operating method according to one of claims 20 to 22, characterized in that the plane of symmetry (11) relative to the gravitational force (g) with an inclination angle between 10 ° and 80 °, in particular between 30 ° and 60 °, in particular 45 °, is inclined ,

24. Operating method according to one of claims 20 to 23, characterized in that in addition an external force (F _FLO w) acts on the particles (10; 20), which is aligned substantially perpendicular to the external gravitational force (g).

25. Operating method claim 24, characterized in that: the additional external force (F _FLO w) is generated by a hydrodynamic flow.

26. Operating method according to one of claims 20 to 25, characterized in that the field cage (1) eight cage electrodes (2-9), which are arranged at the corners of a hexahedron, in particular a cube.

27. Operating method according to one of claims 20 to 26, characterized in that all the cage electrodes (2-9, 14- 19) are driven with the same voltage amplitude.

28. Operating method according to one of claims 20 to 27, characterized in that four of the cage electrodes (2-9) lie in the plane of symmetry (11), while the other four cage electrodes (2-9) lie outside the plane of symmetry.

29. Operating method according to one of claims 20 to 28, characterized in that a) that in the plane of symmetry (11) lying cage electrodes (2-9) have a common phase position, b) that the outside of the plane of symmetry (11) lying cage electrodes (2 9) have a common phase position, and c) that the cage electrodes (2-9) lying in the plane of symmetry (11) on the one hand and the cage electrodes (2-9) lying outside the plane of symmetry (11), on the other hand, are in opposite phase.

30. Operating method according to one of claims 20 to 29, characterized in that a) that in the plane of symmetry (11) lying cage electrodes (2-9) have a common phase position, b) that lying outside the plane of symmetry (11) cage electrodes (2-9) are grounded.

31. Operating method according to one of claims 20 to 30, characterized in that the cage electrodes (2-9; 14-19) in the different electrode planes are driven either a) with the same voltage amplitude or b) with different voltage amplitudes.

32. Operating method according to claim 31, characterized in that a) that the cage electrodes (2-9; 14-19) of the upper electrode plane and the cage electrodes (2-9; 14-19) of the lower electrode plane with different voltage amplitudes corresponding to a certain amplitude ratio be controlled, and b) that the amplitude ratio is set according to the desired focus height (H _F ).

33. Operating method according to one of claims 20 to 32, characterized in that the connecting lines between the cage electrodes (2-9, 14-19) with the same phase position in each case by a predetermined angle, in particular 90 °, with respect to the gravity (g) are inclined.

34. Operating method according to one of claims 20 to 33, characterized in that the connecting lines between the cage electrodes (2-9; 14-19) are aligned with the same phase position each substantially parallel to the gravitational force (g).

35. Operating method according to one of claims 20 to 34, characterized by the following steps: a) setting of a fixing mode for fixing the suspended particles (10; 20) in the field cage (1; 13) and b) setting a rotation mode of the field cage (1; 13) before and / or after the fixing mode, wherein in the rotation mode the suspended particles (10; 20) in the field cage (1; 13) are rotated.

36. Operating method according to claim 35, characterized in that the cage electrodes (2-9, 14-19) in the rotation mode are each driven in pairs with four different phase angles.

37. Operating method according to claim 36, characterized in that the four phase positions in the rotation mode are 0 °, 90 °, 180 ° and 270 °.

38. Operating method according to one of claims 34 to 37, characterized in that alternately the fixing mode and the rotation mode is set.

39. Operating method according to one of claims 34 to 38, characterized by the following step: examination of the in the field cage (1; 13) fixed particle (10; 20) in the fixing mode of the field cage (1; 13).

40. Operating method according to claim 39, characterized in that the examination of the particles (10; 20) in the field cage (1; 13) takes place by one of the following examination methods: a) light microscopy, b) impedance spectroscopy or c) ultrasonic microscopy.

41. Operating method according to one of claims 39 to 40, characterized by the following step:

Selection of certain particles (10; 20) depending on the result of the study.

42. Operating method according to claim 41, characterized by the following step:

Sorting the selected particles (10; 20) into one of several carrier flow output lines of a microfluidic system.

43. Operating method according to one of claims 20 to 42, characterized in that the suspended particles (10; 20) in the field cage (1; 13) are fixed without rotation.

44. Operating method according to one of claims 20 to 43, characterized in that a) that the cage electrodes (2-9, 14-19) of the individual phase positions are each arranged antisymmetrically with respect to exactly one plane of symmetry, and b) that the plane of symmetry parallel to the gravity runs.

* * * * *