EP1565266B1 - Fluidic microsystem and method comprising field-forming passivation layers provided on microelectrodes - Google Patents

Description

The invention relates to a fluidic microsystem with the features according to the preamble of claim 1 and a method for field shaping in a channel of said fluidic microsystem.

It is known to manipulate suspended particles (eg biological cells, cell groups, cell constituents, macromolecules or synthetic particles in suspension solutions) in fluidic microsystems with high-frequency electric fields generated by microelectrodes in channels of the microsystem (cf. BT Schnelle et al. in "Langmuir". Vol. 12, 1996, pages 801-809 ). Non-contact particle manipulation (eg, move, stop, deflect, join, etc.) is based on negative dielectrophoresis. It is known to at least partially cover the arranged on channel walls microelectrodes with an electrically insulating thin layer to unwanted interactions between the microelectrodes and the suspension medium or the particles, such as. B. Ohm 'cal losses, electrolysis, induction of transmembrane potentials, etc. to minimize (passivation of the microelectrodes).

Typically, the fluidic microsystems include spatial electrode arrays. The microelectrodes are at opposite, z. B. lower and upper channel walls with typical distances in the range of 10 .mu.m to 100 .mu.m (s. T. Muller et al. in "Biosensors &Bioelectronics", Vol. 14, 1999, pp. 247-256 ). To achieve defined field effects, the microelectrodes must be shaped in a certain way and arranged relative to each other. In spatial electrode arrangements, this is with a high Justieraufwand the Channel walls (chip levels) connected. The accuracy must be better than 5 μm for typical dimensions of the microsystem in the cm range. Furthermore, problems arise in the production of the microsystem. This is usually done with semiconductor technology techniques, requiring multiple masks for wafer processing for the spatial electrode array. Finally, there is a problem of the spatial electrode arrangement with structured microelectrodes on different channel walls in the electrical contacting. As a rule, the electrical contacting of the upper channel wall (upper chip level) to the lower channel wall has to be carried out and separated electrically from this to a control connection. In particular, with a view to a mass use of fluidic microsystems, there is an interest in microsystems with a simplified structure and increased reliability.

It is known to structure electrically insulating passivation layers in order to effect a specific field shaping (s. DE 198 69 117 . DE 198 60 118 ). The structuring consists in the formation of openings or openings in the passivation layer over a planar electrode. Through the openings, the electric field can pass through from the electrode into the channel and form the desired field shape corresponding to the shape of the opening. However, the openings in the passivation layers have the disadvantage that a contact between the electrode material and the suspension liquid is formed. It may lead to irreversible electrode processes. For example, particles under the field effect can be pulled onto the electrodes and clog the channel. Furthermore, it may lead to a dissolution of the electrode material and thus to a contamination of the suspension liquid. This problem has been addressed by that suspension liquids with a rather low electrolyte content were used. However, this limited the scope of the microsystems. Many biological particles have limited ability to tolerate low electrolyte levels for extended periods of time.

It is also known that field shielding is effected by the passivation layers on microelectrodes. This can be used, for example, to amplify or attenuate field gradients in the channel in accordance with a specific spatial progression (see FIG BT Schnelle et al., S. above and G. Fuhr et al. in "Sensors and Materials", Vol. 7/2, 1995, pp. 131-146 ). A disadvantage, however, is that the attenuating influence of the passivation layer in the suspension liquids with low electrolyte content (low conductivity) is relatively weak.

Out US Pat. No. 6,387,707 B1 and US 2002/0166766 A1 Further fluidic microsystems are known in which a structured electrode is provided on a channel wall and an unstructured electrode is provided on an opposite channel wall.

The object of the invention is to provide an improved fluidic microsystem which overcomes the disadvantages of conventional microsystems. The object of the invention is in particular to provide a microsystem with a simplified structure, in particular a simplified electrode arrangement and a simplified contacting, increased reliability and an extended range of application, in particular in the manipulation of biological particles. The object of the invention is also to provide an improved method for field shaping in fluidic microsystems, in particular to provide for the dielectrophoretic manipulation of particles.

These objects are achieved by microsystems and methods having the features according to claims 1 and 7. Advantageous embodiments and applications of the invention will become apparent from the dependent claims.

A feature of the invention is a fluidic microsystem with at least one channel through which a particle suspension can flow, on the channel walls of which electrode devices for generating alternating electrical fields are arranged in the channel, of which a first electrode device for field shaping is provided with a structuring and a second electrode device is planar, unstructured is formed with a passivation layer, in particular to further develop in that the structuring of the first electrode device has characteristic dimensions smaller than the planar electrode layer of the second electrode device and the passivation layer of the second electrode device is a closed, the electrode surface of the second electrode device completely covering layer. These features considerably simplify the design of the microsystem since only the first electrode device, which is, for example, a lower electrode device on the lower chip level or bottom surface in the operating position, must be structured for field shaping, while advantageously as a second electrode device, in particular as an upper electrode device At the upper chip level or top surface of the channel, a flat, completely passivated electrode layer can be provided, which merely has a single connecting line for connection to a voltage supply or, if the second electrode device is potential-free is operated, no connection cable required. The planar second electrode device can be produced without complex masking steps during the wafer processing. The closed passivation layer on the second electrode device completely avoids undesired electrode processes. The arrangement of the first electrode device at the lower chip level and the second electrode device at the upper chip level is not a mandatory feature of the invention, but may in particular be provided in reverse. Generally, the first and second electrode means may be provided on different channel walls forming the top surfaces, bottom surfaces and / or side surfaces. A further advantage of the combination on the one hand of a structured electrode device (preferably on the bottom surface) and a non-structured, flat electrode device (preferably on the cover surface) is the possibility of realizing the most varied electrode arrangements and system functions, as shown below.

According to the invention, the passivation layer of the second (preferably) upper electrode device in turn has layer structures for field shaping in the channel, wherein the layer structures comprise regions which have a changed thickness in the passivation layer or a material other than the surrounding passivation layer. This structuring of the passivation layer is combined with a planar electrode layer. The patterning of the passivation layer may have advantages in terms of field shaping in the channel.

According to a first embodiment of the invention, the first electrode device may comprise at least one structured electrode layer having individual partial electrodes, which in their entirety constitute the structuring or at least one first structural element, as is known per se from conventional microelectrode arrangements. The provision of a plurality of sub-electrodes may be advantageous in relation to a separate controllability of each sub-electrode. The separate controllability is important, for example, if the fields in the channel are to be varied depending on certain external influences or measurement results. The sub-electrodes preferably comprise individually controllable electrode strips, ie microelectrodes with an elongated line shape with a typical width in the range of 50 nm to 100 μm and a typical length of up to 5 mm. The sub-electrodes can carry passivation layers, which optionally carry a defined opening corresponding to the position of the sub-electrodes.

The layer structures in which the field penetration is modulated into the channel are formed, for example, by regions of changed (reduced or increased thickness) in the passivation layer. Advantageously, these lowered or protruding layer structures can be produced by a simple etching process. The shape of the layer structures can be adjusted by masking. Emerging layer structures are particularly preferred when forming the passivation layer with materials having a relatively high dielectric constant. Alternatively, the layer structures may comprise regions which have at least one other material than the surrounding passivation layer, which is characterized in particular by a changed dielectric constant. Both forms of the layer structures, ie the thickness variation and the material variation can be provided in combination. Furthermore, the passivation layers can be formed of different layer materials in multiple layers.

Further advantages may result for the design of the microsystem if passivation layers are at least partially formed by layer materials whose dielectric properties are reversibly or irreversibly variable ("smart isolation"). The coating materials are converted, for example, by a laser treatment between different modifications (eg crystalline <-> amorphous), which are distinguished by different DK values. Such changeable materials are for example descriptive or rewritable optical storage (CD) known. Alternatively, as a variable layer materials, polymers can be used whose conductivity can be changed at least once by laser irradiation as in a direct laser writing method. Advantageously, specific prototypes (eg for rapid prototyping) can be produced with this embodiment particularly favorably.

Advantageously, the channel is equipped with the electrode devices described above with at least one transverse channel, in which a third electrode means for generating electrical DC fields in the transverse channel is arranged. Through the passivation of the first and second electrode devices, the transport processes in the transverse channel remain undisturbed.

An advantage of passivation layers compared to bare electrodes is that the resistance of bare electrodes can already change by orders of magnitude due to the superposition of monolayers. This can be relatively easy during the Chip production or in operation happen and endanger the function of dielectric elements in particular when the layers are not homogeneous. To avoid this problem, additional measures (plasma etching, etc.) had to be implemented so far. On the other hand, additional layers on passivation layers have a significantly less disturbing effect. The functional reliability of the microsystems is thereby improved.

Another object of the invention is a method for field shaping in a channel of the fluidic microsystem according to the invention, in particular for the dielectrophoretic manipulation of suspended particles in the fluidic microsystem according to the invention by the field shaping by means of lateral structures in passivation layers on electrodes.

Fign. 1A, 1D und 1E:

schematische Ansichten verschiedener Ausführungsbeispiele erfindungsgemäßer Mikrosysteme (Ausschnitte),

Fign. 1B und 1C:

Ausschnitte von weiteren Mikrosystemen (keine Ausführungsbeispiele der Erfindung),

Fig. 2:

eine weitere schematische Illustration einer Elektrodeneinrichtung mit einer strukturierten Passivierungsschicht,

Fign. 3A-3D:

Kurvendarstellungen zur Illustration der Feldwirkung der erfindungsgemäß vorgesehenen Passivierungsschichten,

Fign. 4A, B:

ein Ausführungsbeispiel der Erfindung mit einer Gradientenstruktur in der Passivierungsschicht,

Fig. 5:

kein erfindungsemäße Ausführungsbeispiel einer Elektrodenanordnung eines Mikrosystems,

Fig. 6:

eine Feldbarriere eines erfindungsgemäßen Mikrosystems,

Fign. 7A, 7B:

schematische Illustrationen eines weiteren Ausführungsbeispiels eines erfindungsgemäßen fluidischen Mikrosystems, und

Fig. 8:

ein weiteres Ausführungsbeispiel eines erfindungsgemäßen fluidischen Mikrosystems.

Further advantages and details of the invention will become apparent from the following description of the accompanying drawings. Show it:

FIGS. 1A, 1D and 1E:

schematic views of various embodiments of microsystems according to the invention (extracts),

FIGS. 1B and 1C:

Cutouts of further microsystems (no embodiments of the invention),

Fig. 2:

a further schematic illustration of an electrode device with a structured passivation layer,

FIGS. 3A-3D:

Graphs illustrating the field effect of the passivation layers provided according to the invention,

FIGS. 4A, B:

an embodiment of the invention with a gradient structure in the passivation layer,

Fig. 5:

no inventive embodiment of an electrode assembly of a microsystem,

Fig. 6:

a field barrier of a microsystem according to the invention,

FIGS. 7A, 7B:

schematic illustrations of another embodiment of a fluidic microsystem according to the invention, and

Fig. 8:

a further embodiment of a fluidic microsystem according to the invention.

In Figure 1A In a schematic perspective view, a part of a fluidic microsystem 100 according to the invention is shown. The microsystem 100 includes at least one channel 10 formed between two plate-shaped chip elements, namely the bottom element or substrate 20 and the cover element 30. Other parts of the microsystem, in particular lateral walls, spacers and the like are not shown for reasons of clarity. The substrate 20 forms a first (lower) channel wall with a bottom surface 21 facing the channel 10, on which a first electrode device, optionally with a passivation layer (see below), is arranged. The cover element 30 forms the second (upper) channel wall with a cover surface 31 facing the channel 10, on which the second electrode device (see below) is arranged accordingly. At least one of the electrode means is for field generation in the channel 10 with an AC voltage source (not shown). At least on the second electrode device according to the invention a passivation layer is provided.

The channel 10 is formed by a free space between the chip elements 20, 30. It is permeable by a liquid, in particular a particle suspension and has a height, for example. In the range of 5 .mu.m to 1 mm and application-dependent selected transverse and longitudinal dimensions in the micrometer to cm range. The chip elements 20, 30 are typically made of glass, silicon or an electrically non-conductive polymer.

The layer structure of electrode device and passivation layer is in the right, enlarged section of Figure 1A shown. For example, on the bottom surface 21 of the substrate 20 is the first electrode device 40 and a first passivation layer 50 (see, eg, FIG. Figure 1C , (not an embodiment of the invention). The layer structure is formed by per se known planar technology by deposition of the desired materials on the substrate. The electrode device consists of an electrically conductive material, for. As a metal or conductive oxide, for. Sn doped In ₂ O ₃ , (ITO), indium cadmium oxide (In _x Cd _1-x O), Cd ₂ SnO ₄ , or a conductive polymer (eg, polyaniline, polypyrrole, polythiophene). The thickness of the electrode device is, for example, in the range of 50 nm to 2 microns. The passivation layer 50 is a dielectric insulating layer having a thickness in the range of 0.1 μm to 10 μm. It consists, for example, of polyimide or an electrically insulating oxide, for. For example, silicon oxide, silicon nitride.

In the FIGS. 1B and 1C Illustrations of microsystems are illustrated in which the second electrode device carries an unstructured passivation layer (no embodiments of the invention). In the Figures 1D and 1E For example, the above preferred embodiments of the invention are illustrated with schematic plan views of the first (lower) and second (upper) channel walls 21, 31.

According to FIG. 1B (Not an embodiment of the invention), the first electrode means 40 is formed structured for field formation in the channel. It is generally equipped with at least one first structural element, which in the illustrated example comprises four electrode elements or partial electrodes 41, which are formed in strip-form on the bottom surface 21 in a manner known per se. The partial electrodes 41 may be covered with a passivation layer (not shown), which optionally has openings on the surfaces of the partial electrodes 41 in a manner known per se.

The second electrode device 60 on the cover surface 31 comprises a planar electrode layer 61 (shown in dashed lines) with a closed second electrode surface, which is completely covered by a second passivation layer 70.

It is provided that the first structural elements 41 of the first electrode device 40 form a smaller effective electrode area than the second electrode area 61 of the second electrode device 60 (the sum of the individual areas of the first electrode device 40 is smaller than the second electrode area 61). As a result, when the electrode devices 40, 60 are acted upon by electrical voltages, field line profiles are formed which combine on the bottom surface 21 at the partial electrodes 41 with an enlarged field line density and terminate on the top surface 31 in the electrode layer 61. The electric field in the channel is shaped according to the shape of the sub-electrodes. For example, a field barrier or a field cage is formed, with which the movement of particles in the channel can be influenced or particles can be held.

The electrode layer 61 of the second electrode device 60 may be connected to a control device via a connecting line in accordance with a first operating mode. In contrast to conventional electrode arrangements, advantageously only one connecting line for forming the counterelectrode is sufficient, for example for a field cage with a barrier shape corresponding to the partial electrodes 41. In accordance with a second operating mode, the second electrode device may be arranged on the cover surface 31 without being connected to a control device. In this so-called "floating" state, the potential of the second electrode device automatically forms as a function of the surrounding potential conditions. In each case a charge distribution is formed in the electrode layer, which compensates for the field occurring in the channel in the interior of the electrode layer. In this case, advantageously can be completely dispensed with a contact.

Figure 1C (Not an embodiment of the invention) illustrates a microsystem in which both electrode devices 40, 60 are formed by flat, closed electrode layers 42, 61 which are each covered by closed passivation layers 50, 60. The first (lower) electrode device 40 is equipped with at least one structural element, which in this embodiment is formed by a structure in the first passivation layer 50. The layer structure in the first passivation layer 50 comprises Areas 51 with z. B. reduced thickness and / or in comparison to the remaining passivation layer varied materials. The regions 51 have laterally in the layer plane a geometric shape corresponding to the conventionally formed microelectrodes, that is, for example, a strip shape. The second electrode device 60 is according to Figure 1C as in FIG. 1B formed by an electrode layer with closed, unstructured passivation layer 70.

By using the patterned passivation layer 50 on the sheet-like electrode layer 42, the geometric shape of the passage of the electric field from the electrode layer 42 into the channel is set in a predetermined manner according to the shape of the areas 51. The regions 51 can, for example, be a line-up element with a funnel-shaped field barrier (FIG. Figure 1C ) form. Alternatively, a plurality of structured regions (field structuring elements) can be realized in a passivation layer which covers a closed electrode layer. This has the advantage that a fluidic microsystem, for. B. a sorting system with a plurality of functional elements with only two, provided on opposite channel walls and with structured passivations electrodes is constructed, possibly only one electrode is driven with a high-frequency voltage and the other electrode is left in the floating state.

According to FIG. 1D is the first electrode device on the bottom surface 21 with a plurality of partial electrodes 41 as in FIG. 1B is constructed while the second electrode means 60 according to the invention with a structured passivation layer 70 is covered. The structured regions 71 in the passivation layer 70 have, for example, a geometric shape according to the orientation of the opposing sub-electrodes 41 to form the field cage.

Finally, according to the embodiment in FIG Figure 1E the structuring may be provided on both passivation layers, that is to say both on the bottom surface and on the top surface.

FIG. 2 illustrates a section of an electrode device according to the invention with structured passivation layer in an enlarged, exploded perspective view. On the substrate 20 there is the electrode layer 40 with a dielectric insulating layer or passivation layer 50 having a structured region 51 processed thereon. The thickness d _{p of} the passivation layer 50 is, for example, 600 nm. At the structured region 51, the thickness d _s is _set to a value of z , B. 200 nm or formed with an altered composition having other electrical properties, a modified dielectric constant or an altered specific electrical conductivity.

The structuring of the passivation layer 50 can be carried out, for example, by photolithography. If the first and / or second passivation layer is formed at least partially by a layer material whose dielectric properties are reversibly or irreversibly variable, the structuring can be carried out, for example, by laser irradiation in accordance with the geometry of the desired structures.

FIGS. 3A to 3D illustrate the effect of the passivation layers structured according to the invention on the basis of the results of model calculations. The structure of the two electrode devices on channel walls with the suspension-flow channel is modeled by a liquid-filled plate capacitor assuming infinitely large capacitor plates in which, for example, an electrode is provided with a passivation layer. The field strength inside the channel (or the plate capacitor) depends on both the frequency and the dielectric and geometric conditions. The modeling takes place with the following parameters: Dielectric constant of the suspension or solution between the capacitor plates: 80, dielectric constant of the passivation layer: 5 and conductivity of the passivation layer: 10 ^-5 S / m.

FIG. 3A illustrates the relative field strength E _rel (field strength with passivation layer / field strength without passivation layer) in the channel as a function of the frequency f at different conductivities of the aqueous suspension in the channel. The thickness of the passivation layer is 1% of the distance of the electrode device. FIG. 3A shows that the field coupling into the channel depends on the conductivity of the suspension and the frequency. Surprisingly, it has been found that the insulating effect of the passivation layer depends on the frequency and becomes increasingly strong as the electrolyte content increases.

FIG. 3B shows with the same parameters as in FIG. 3A the phase angle Φ (in radians) of the electric field. The phase angle Φ is also strongly frequency-dependent with increasing conductivity. According to the in the FIGS. 3A and 3B As shown, electric field gradients in the channel can be realized in terms of phase and amplitude with homogeneous electrodes. This can be used, for example, to realize an octupole cage, which conventionally required eight electrodes, with only four electrodes, each one of them Electrode over a suitable passivation two in each case by approx. 90 ° out of phase signals.

FIG. 3C shows the relative field strength E _rel in the channel as a function of the frequency at different thicknesses of the passivation layer, which is indicated in each case as a% proportion relative to the electrode spacing. The modeling is done with a water-filled channel (conductivity: 0.3 S / m). It turns out that the field penetration is considerably reduced with increasing thickness of the passivation layer and that this effect is frequency-dependent. According to the in FIG. 3C As illustrated, locally at the structured regions (eg 51 in FIGS. 1C, E) an increase of the field strength in the channel can be achieved by a reduction in thickness. This effect depends on the frequency. This means that a functional element in the fluidic microsystem can be activated or ineffective depending on the frequency.

A corresponding result can be seen in structurings of the passivation layer by introducing regions with a changed dielectric constant. With a suspension conductivity of 0.3 S / m and a thickness of the passivation layer of 1% of the electrode spacing results according to Figure 3D with increasing dielectric constant an increasing field penetration even at lower frequencies.

The results according to FIG. 3 show a particular advantage of the invention in that the modulation of the field in the channel by the structured passivation is particularly effective at lower conductivities of the suspension in the channel. In the manipulation of artificial particles, in particular of plastic, for. As latex beads, there is an interest in using low conductivities. With a salt content of 1 mM results, for example, a conductivity of approx. 14 mS / m. Biological cells are often handled in media with conductivity around 1 S / m. Short term (up to 10 min) dielectric conduction in low conductivity up to 1 mS / m is well tolerated. For the dielectric manipulation typically 0.05-0.3 S / m are used.

According to a particular advantage of the invention, the structured passivation layers form frequency filters. Certain field components with certain frequencies are allowed to pass through the structured regions (eg 51) due to high field penetration, while other frequency components are attenuated (s. FIG. 3 ). This effect depends on the thickness and / or composition of the structured regions of the passivation layer. If the electrode devices with high-frequency voltage signals with a z. B. rectangular waveform, which represents a corresponding superposition of a plurality of frequencies, the frequency composition can be modulated in the channel by the passivation layer. Since the dielectrophoretic effect of the electric fields is frequency-dependent in particular, the function of the respective electrode device can be adjusted via the frequency of the control voltage.

According to an alternative embodiment of the invention, the structuring of the passivation layer may be formed inhomogeneous in itself. For example, a region 51 of reduced thickness in the passivation layer 50 may be formed according to FIG FIG. 4A have a Dickengradient in itself. At one end 51a with a larger thickness, the field penetration is lower than at the opposite end 51b with the smaller thickness. On this basis, only by a strip-shaped passivation according to FIG. 4B a filter for different types of particles or sizes are formed. A particle mixture flowing in a partial channel in the direction of the arrow strikes the field barrier which is formed on the structured region 51. The small particles, which are relatively unaffected by a strong field, can pass the field barrier at region 51 without deflection, while the larger particles are first deflected into an area with reduced field penetration. Correspondingly, after passage of the region 51, the particles of different size follow different paths in the channel.

FIG. 5 shows in more detail a non-inventive dielectric filter element, wherein the first electrode means 40 is provided at the upper chip level. The bottom element 20 and the cover element 30 are formed by glass substrates, which are mounted one above the other at a distance from one another and form the upper and lower boundary of the channel 10. The distance h is, for example, in the range of 5 .mu.m to 100 .mu.m. On the upper cover surface 31, an electrode strip 41 with a passivation layer 50 is provided. The electrode strip 41 is connected via a connecting line 43 to a power supply (not shown). The passivation layer 50 is opened above the electrode strip 41.

An unstructured electrode layer 61 is attached to the bottom part 20 as a second electrode device, and a structured passivation layer 70 is applied to this according to the invention. In region 71, passivation layer 70 is reduced in thickness and / or composition is varied. In the case of a passivation layer thickness in the region 71 of 10% of the electrode spacing (eg 400 nm to 600 nm), in the channel above the structured region 71 the relative field strength at a frequency of 1 MHz increases from 0.1 to 0.7 (see FIG. FIG. 3C ). Thereby For example, a sufficiently high field gradient in the flow passing through the channel 10 can be generated locally between the electrodes. The field gradient forms a field barrier, which, for example, restrains large particles and lets small particles through. Advantageously, it can be exploited here that the acting restraining force scales quadratically with the field strength.

The simulation representation in FIG. 6 shows the distribution of the field strength squares, ie the potentials for dielectric force effect, in an embodiment with two strip-shaped electrode structures 40, 60 (distance h = 40 microns), each carrying a passivation layer (not shown) with a thickness of 5 microns. In each passivation layer, two strips with a width of 50 μm are formed, each of which is a substance with an increased dielectric constant (DK = 100, eg TiO 2, higher values of DK of up to 12000 are for titanates such as BaTiO, SrTiO, CaTiO, PbTiO possible), while the remaining passivation layer in each case comprises polyimide (DK = 3.5) or SiN _x O _y . The channel 10 is filled with water at 10 mS / m. The electrodes are supplied with sinusoidal signals at a frequency of 10 MHz. Between the opposing electrode devices 40, 60, concentrated field lines form, which form two field barriers for the particles flowing in the channel 10.

The FIGS. 7A and 7B Illustrate in each case from the channel 10 from considered schematic plan views of the upper (A) and lower (B) channel wall of a fluidic system 100 according to the invention with the channel 10, which splits into two sub-channels 11, 12. In channel 10 are as dielectric functional elements 80, two deflectors 81, 82, a hook 83 and a switch (switch) 84 arranged, as it is in itself from the fluidic Microsystem technology is known. Furthermore, measuring devices, for. B. Particle detectors may be provided.

The lower chip level ( FIG. 7B ) is analogous to FIG. 1D constructed in a conventional manner with individually controllable sub-electrodes. The partial electrodes z. B. 41 with different geometric configurations each have a connecting line 43, leading to connection points (bond pads) 44. The electrode areas not required for the dielectric manipulation of the particles are completely passivated. The passivation is opened above the active electrode areas (see eg at 52).

The upper chip level ( FIG. 7A ) is simpler. It's analogous to FIG. 1D a single electrode layer (not shown) with a closed electrode surface on which a passivation layer (not shown) with structured regions 71 is formed. For the formation of an electric field between the electrode pairs of the upper and lower chip planes, only the upper level electrode layer and the lower level part electrodes are connected to a power supply (generator).

The field-shaping structures (sub-electrodes and structures in the passivation layer) may be arranged offset in the channel direction in order to form a channel-driving field.

The particles are flowed into the channel 10 in the direction of the arrow and exposed to the electric field barriers at the sub-electrodes. Depending on the desired function, individual partial electrodes can be switched on or off. For a trouble-free separation of the individual functional elements is preferably set a lateral electrode spacing (in the channel direction) which is greater than the channel height.

FIG. 8 shows an example of a microsystem 100 according to the invention, in which both the lower and the upper electrode means is completely covered with structured passivation layers and in addition a perpendicular from the channel 10 or diagonally branching transverse channel 13 is provided with a third electrode means 90 for generating a DC voltage field. In the transverse channel 13, a liquid or particle transport can take place between the electrodes 91, 92 by electroosmosis or electrophoresis under the effect of the DC voltage field (see double arrow), which remains undisturbed by the passivation of the first and second electrode devices. For example, it is provided to deflect a particle into the transverse channel 13 as a function of the signal of a particle detector. Furthermore, electroporation or electrofusion processes can be triggered when passing through transverse channel 13 when pulsed DC voltages are applied.

The features of the invention disclosed in the foregoing description, drawings and claims may be significant to the realization of the invention in its various forms both individually and in combination.

Claims (7)

1. A fluidic microsystem, comprising:

   - at least one channel (10) through which a particle suspension can flow, and

   - first and second electrode devices (40, 60) which are arranged on first and second channel walls (21, 31) for generating electrical alternating-voltage fields in the channel (10), wherein

   - the first electrode device (40) for field shaping in the channel is provided with first structure elements (41, 51), which are formed by structured partial electrodes (41, 51), wherein the structured partial electrodes (41, 51) comprise individually controllable electrode strips,

   - the second electrode device (60) comprises an area-like second electrode layer (61) with a closed second electrode surface, and

   - the sum of the individual areas of the electrode strips of the first electrode device (40) is smaller than the second electrode area (61),
   characterised in that

   - the area-like second electrode layer (61) carries a passivation layer (70), wherein

   - the passivation layer (70) is a closed layer which completely covers the second electrode layer (61),

   - the passivation layer (70) has at least one second structure element for field shaping in the channel (10), which is formed by layer structures (71) in the passivation layer (70), wherein

   - the layer structures (71) comprise regions, which have a changed thickness in the passivation layer (70) or a material that differs from the material of the surrounding passivation layer (70).
2. The microsystem according to claim 1, in which the regions of the layer structures (71) are inhomogeneous with a thickness gradient and/or a material gradient.
3. The microsystem according to any one of the preceding claims, in which the passivation layer (70) comprises several layers.
4. The microsystem according to any one of the preceding claims, in which the passivation layer (70) is at least partly formed by a layer material whose dielectric characteristics are reversibly or irreversibly changeable.
5. The microsystem according to any one of the preceding claims, in which a third electrode device (90) is provided for generating electrical direct-voltage fields or direct-voltage pulses in the channel (10) or in a transverse channel (13) which branches off from the channel (10).
6. The microsystem according to any one of the preceding claims 1 to 4, in which an external electrode device is provided for generating electrical direct-voltage fields or direct-voltage pulses in the channel (10) or in a transverse channel (13) which branches off from the channel (10).
7. A method for field shaping in a channel (10) of a fluidic microsystem (100) according to any one of the preceding claims, in which the geometric shape of electrical fields in the channel (10) is determined by the geometric shape of layer structures in the passivation layer (70) in which there is a modified field transconductance.

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