DE10356308A1 - Integrated fluid mixer comprises at least one fluid channel for supplying liquids, a branch for splitting the liquid flow, and a step section - Google Patents

Abstract

An integrated fluid mixer comprises at least one fluid channel (1) for supplying the liquids, a branch for splitting the liquid flow into primary and secondary channels (4,3), and a step (7) section. The second channel has the same flow resistance as the first channel, and the channels are bordered by an unstructured plate (14). The mixer has a flow splitting element (2).

Description

The The invention relates to an integrated fluidic mixer for mixing of fluids flowing through. The invention further relates to a manufacturing method for manufacturing such an integrated fluidic mixer.

at In microfluidics, small amounts of fluid are transported, manipulated and analyzed. An important process in many microfluidic Applications is the mixing of different liquids, e.g. Solutions and Analytes.

The liquids become small in liquid channels Cross section transported. Due to the small cross-section flow liquids in these channels always laminar, i. there is no turbulence. Two liquids, the above corresponding channels together are therefore running parallel to each other and mixing only via diffusion, but not by turbulence. In these cases, the mixing takes a lot long, allowing fluid channels with comparatively huge lengths must be provided in the microfluidic device, thus a complete mixing both liquids can be done.

to Acceleration of the mixing process is usually the maximum distance, which is to be mixed by diffusion, reduced. To do this divided the liquid streams and recombined in some other way, so that the fluid flows into each other be interwoven and thus the size of the interface between both liquid flows is increased. For example, can the two fluid streams repeated divided horizontally and merged vertically again, so instead of an interface between the liquid flows more interfaces be created where diffusion takes place.

at the production of a fluidic mixer are usually two substrates with simple processes, e.g. Embossing, casting, isotropic or anisotropic etching structured and then composed, since the liquid guide is not can be realized in a block. The joining of two substrates is relatively expensive, since connecting e.g. two semiconductor substrates due to the high purity requirement on the surfaces poses a high risk regarding the process yield includes and thus is expensive. In addition, two are structured Wafer needed, which double the material and process costs.

Though can be a structured glass wafer by means of anodic bonding be well connected to a structured semiconductor substrate, However, the structuring of the glass wafer is complex and thus costly.

It It is an object of the present invention to provide a fluidic mixer as well as a simple manufacturing method for the fluidic mixer available put.

These The object is achieved by the integrated fluidic mixer according to claim 1 and solved by the method of claim 11.

Further advantageous embodiments of the present invention are in the dependent claims specified.

According to one The first aspect of the present invention is an integrated fluidic Mixer for mixing through-flowing Liquids provided. The mixer comprises a fluid channel, around the liquids to be mixed be forwarded. By branching the liquid channel is in a first and split a second sub-channel. In the first of the two subchannels a stage is arranged, with the subchannels behind the branch in a merge together are. The stage is arranged in the first subchannel such that a flow away End of the stage essentially arranged at the junction of the two sub-channels is. The second subchannel is designed to be the same flow resistance has, as the first sub-channel. In particular, in the second Partial channel arranged a stage so that it has the flow resistance and that you are facing away from the flow End before the merger the subchannels ends. A boundary of both subchannels is characterized by an unstructured Plate formed.

Of the integrated fluidic mixer according to the invention has the advantage that it can be easily constructed, in particular by it is avoided that two structured substrates are joined together have to, to form the mixer structure. The mixer assembly according to the invention allows it to perform the structuring within a single substrate, the so finished with a substantially unstructured plate can be that a fluidic mixer with fluid channel, branching, together and the subchannels is formed.

Especially can the branching and merging of the mixer by one in the liquid channel be arranged element arranged. In this way, the Branching and merging be formed by a single structure, thereby structuring the mixer can be done in a simple manner.

Preferably For example, the mixer has a substantially circular, quadrangular or oval floor plan surface.

Especially The mixer can be made with a silicon substrate, silicon dioxide and / or plastic.

Especially can be provided that the steps arranged in the sub-channels are that the subchannels essentially the same flow resistance exhibit. This has the advantage that the liquid flows in the subchannels are distributed substantially the same, so that through each of the sub-channels one sufficient amount of fluid flow can.

Preferably the steps in both subchannels are on the same inside wall side arranged. The inner wall side is preferably that of the boundary through the unstructured plate opposite inner wall surface.

This represents a particularly simple embodiment of the mixer according to the invention because the stages are made in a single process step can be without the functionality of the Mischers impaired becomes.

alternative can the steps also as passages in a wall structure of the mixer introduced into each subchannel be formed, wherein the passage in the first subchannel in sufficient Distance to the merge, z. Near the branch and in the second subchannel near the junction together is arranged. In this way, another preferred embodiment the mixer according to the invention be created, which can also be constructed so that the substrate in which the fluidic mixer structure is introduced is, can be completed by an unstructured plate, to form the fluidic mixer.

Preferably is behind the passage in the first subchannel the structure of first sub-channel designed to transfer the fluid flow into a first Directing the plane and designing the structure of the second subchannel, to the liquid flow to the appropriate passage near the merge to direct the fluid flow in a second level in the merge issue. To this Manner may be a mixer structure for a fluidic mixer be created, which is a liquid flow divides and the parts of the liquid flow reassembled in a rotated arrangement.

According to one Another aspect of the present invention is a method for Preparing a fluidic mixer provided. It is in a Substrate material over Shaping and Separation method introduced an upwardly open mixer structure or applied to a substrate material, in which case the Mixer structure with a substantially unstructured plate is covered to create the closed mixer structure. In this way, a manufacturing process for producing a fluidic mixer available be made with the fluidic mixer in a simple manner and with a large production yield, i.e. economical can be produced.

It it can be provided that the mixer structure with a fluid channel for supplying liquid, with a branch for dividing the liquid channel into two sub-channels and with Levels in each of the subchannels is formed. For this purpose, an etching stop layer is formed on a first functional layer applied and this structured so that when etching the Steps are formed. On the first functional layer and the etch stop layer a second functional layer is applied. A deep etching process is running, wherein the second functional layer according to a predetermined channel structuring etched becomes. The deep etching process becomes at the etch stop layer stopped and the first functional layer according to the structuring the etch stop layer etched. In this way, with the help of a single Tiefenätzpro process the channel and the steps are formed in the channel.

It can be provided that the first functional layer on the substrate is applied or is included in the substrate.

The surface the second functional layer can be processed so that a bondable surface arises, so that the unstructured plate with the bondable surface with Help of a wafer bonding process and the like. Can be connected.

Alternatively it can be provided that the mixer structure is formed with a liquid channel for supplying liquid, with a branch for dividing the liquid channel into two sub-channels and with steps in each of the sub-channels. For this purpose, a sacrificial layer is applied to a substrate, to which a first functional layer is applied. On the first functional layer, an etch stop layer is applied, and this structured. On the first functional layer and the structured etching stop layer, a second functional layer is applied. A deep etching process is carried out, the first and second functional layers being etched in accordance with a predetermined channel structuring. The deep etching process is stopped at an etching stop layer so that the covered first functional layer remains. After throughput In a further etching step, the sacrificial layer is etched into the first functional layer, with undercuts being made below the first functional layer, the sacrificial layer being substantially etched from both sides of the wall structure under a wall structure formed by the first functional layer so as to form a passage under the wall structure. In this way, it is possible to produce passages in wall structures after a deep etching step, so that three-dimensional flow guides in a sub strate can be generated by a one-sided structuring of a substrate, without structuring two substrates, which are then joined together in a suitable, mutually adjusted manner have to.

preferred embodiments The invention will be described below with reference to the accompanying drawings explained in more detail. It demonstrate:

1A a first embodiment of a fluidic mixer according to the invention;

1B a representation of a series arrangement of fluidic mixers after 1A ;

1C and 1D Further variants of the first embodiment of the fluidic mixer according to the invention after 1A ; 2A to 2D the method of manufacturing the mixer element with reference to a sectional view and a plan view according to the first embodiment of the invention;

3A a plan view of a fluidic mixer according to a second embodiment of the invention;

3B a cross section through the fluidic mixer according to the second embodiment of the invention;

4A to 4C illustrate the process steps for manufacturing the fluidic mixer according to the second embodiment of the invention.

In 1A is shown in a perspective view, a fluid mixer without top cover according to a first embodiment of the invention. Such a fluidic mixer is often used in a series arrangement of multiple mixer elements, as in FIG 1B represented, arranged. The fluidic mixer has a supply channel 1 via which two or more combined liquid streams are fed to the mixer. A flow divider element 2 forms a branch for the liquid flow. Through the flow divider element 2 become a first subchannel 3 and a second subchannel 4 educated. Downstream of the flow divider element 2 become the two subchannels 3 . 4 merged again in a merger and into a drainage channel 5 output.

In the first subchannel 3 is a first step 6 and in the second subchannel 4 a second stage 7 arranged. The first stage 6 in the first subchannel 3 causes the partial liquid flow at the branch to be raised to a second flow level E2, while the liquid flow at and after the branching in the second sub-channel 4 still remains in a first flow level E1. The second stage 7 begins in a branch downstream from the branch and ends when the two subchannels are merged 3 . 4 , so that the partial liquid flow of the second sub-channel 4 in the second flow level E2 is passed into the merge. The first stage 6 ends well before the merge, so that the partial liquid flow flows again via the first flow level E1 in the merge. When merging, the liquid flow passing through the second subchannel 4 flows, thus via the liquid flow, in the first sub-channel 3 flows, pushed. In this way, a mixer structure is created, which divides a liquid flow vertically and then horizontally superimposed. The first stage 6 is essentially intended that in both sub-channels 3 . 4 the same flow resistance prevails, so that the amounts of liquid in both sub-channels are substantially equal.

The into the subchannels 3 . 4 introduced steps 6 . 7 lift the partial flows in the sub-channels in certain places. The flow divider divides the liquid into two partial flows and brings them together again after a short distance. By inserting steps at a suitable location, the first sub-channel is raised shortly before merging. The corresponding liquid flow thus slides over the other, the horizontally separated liquid flows are brought together vertically again. The position of the steps and the geometric design are arbitrary depending on the requirements of the mixer (flow, mixing rate, etc.) and can be determined, for example, by previous simulations.

at the shown circular Floor plan of the fluidic mixer, the steps can be like a circle segment within the circular Floor plan may be arranged, wherein the stage with respect to the total height of the flow channel a height having a superposition the partial flow allows. For example, the height a step about half the total height of the flow channel be.

In the 1C and 1D are other variants of the mixer according to the first embodiment form shown. Instead of a circular flow divider element 2 is in 1C a square or rhombic flow divider element and in 1D a lenticular divider element is provided. The formation of the stages in the sub-channels is essentially arbitrary, it is only necessary that in one of the sub-channels, the stage ends only with the merger of the sub-channels, while the stage in the respective other sub-channel should be designed so that substantially the same Flow resistance is ensured and that the stage ends before the merger of the sub-channels.

By the repeated splitting of the liquid flow in two partial flows and by subsequent Rejoining the partial flows in another arrangement, the interface between the two is to be mixed Fluid flows increased, so that a mixing of the two liquids Diffusion can be done faster than without mixer element the case would be.

In a square channel, simply rotating the assembly does not yet increase the interface, only the repeated splitting and twisted placement result. Only if the aspect ratio of the channel deviates significantly from the value 1, can an improvement in the mixture be established even after the arrangement has been turned. It is therefore generally useful to arrange a plurality of such mixers in series for optimal mixing efficiency, regardless of the channel shape, such as in 1B is shown.

The in the 1A - 1D Mixers shown are preferably formed in a semiconductor substrate, in particular in a silicon substrate, since this can be structured in a simple manner by means of known methods. However, it is also conceivable that such mixer structures in other materials, such as plastic, glass and the like can be produced.

One Semiconductor substrate made of silicon is therefore particularly suitable because the mixer structure in a known manner with a substantially unstructured plate of suitable material, eg. Borosilicate glass, can be closed by anodic bonding, so that completed Fluid channels formed become.

In the 2A to 2D the manufacturing method for the fluidic mixer according to the first embodiment is shown. In the first step, for example, a wafer substrate or a first functional layer applied to a substrate is applied to a suitable semiconductor surface 10 , z. Example, an epitaxial layer, for example of silicon, a suitable Ätzstoppschicht, for example, silica SiO ₂ , by means of a suitable method (eg, thermal oxidation, CVD method or the like) applied and patterned. The first functional layer 10 is for example made of semiconductor material, such as. Example, silicon in the form of epipoly-silicon, which would be applied with a polysilicon starter layer and a polycrystalline Epitaxieschicht. The patterning of the etch stop layer takes place, for example, by wet-chemical or dry etching. The structuring is done according to the in 1A executed stepped structures, ie the etching stop layer 11 stops the etching process in the area of the stepped structures. A top view of the structure of the etch stop layer 11 is on the right side of the page 2A shown.

The next step is a second functional layer 12 of the semiconductor material is applied by a suitable epitaxial method or the like. For example, as a second functional layer 12 a semiconductor material such as silicon in the form of epipoly-silicon having a polysilicon starter layer and a polycrystalline epitaxial layer may be deposited. The thicknesses of the first and second functional layers 10 . 12 depend on the necessary thickness of the sub-channels above and beside the steps 3 . 4 ,

After application of the second functional layer, the surface of the second functional layer is processed so that a bondable surface is formed. For example, the bondable surface can be produced by polishing. This layer is then patterned by anisotropic etching, for example by a trench etching process. For this purpose, a suitable etch masking is carried out with the aid of photoresist on the surface. The photoresist structure 13 in the 2 B shows the Aussparen the flow divider element of the subsequent deep etching.

The result of the deep etching process is in 2C shown. The dashed sections illustrate the areas of the first and second functional layer remaining in front of or behind the cutting line.

The anisotropic etch is in the area of the steps where the etch stop layer 11 was not removed, stopped at this, the other areas are further etched into the depths. In the upper semiconductor layer, the masking through the photoresist thus completely forms. The semiconductor layer below the etch stop layer (the first functional layer) becomes an intersection of the upper masking by the photoresist 13 with the structuring of the etch stop layer 11 etched. It is thus possible to realize several stages in the semiconductor substrate simultaneously with a deep etching step. The etching of the lower semiconductor layer takes place according to a predetermined Time, reducing the depth of the etching of the first functional layer and thus the height of the steps 6 . 7 can be determined. However, there may be another below the first functional layer 10 introduced suitable further Ätzstoppschicht stop the etching defined.

In order to complete the fluidic mixer, it must be on the remaining surface of the second functional layer 12 a substantially unstructured plate 14 , For example, be applied from silicon dioxide or the like by a suitable bonding technique. This creates fluid channels that are closed off from the environment. When using a silicon substrate is the substantially unstructured plate 14 made of a suitable material, preferably borosilicate glass o. Ä., Which can be connected by means of anodic bonding, direct bonding or the like with the silicon substrate. As a result, the fluidic mixer is sealed and can thus ensure a fluid guide.

In 3A is another embodiment of a fluidic mixer according to the invention, which on a substrate 25 with a first and a second functional layer 32 . 34 is constructed, shown. The division of the liquid flow takes place through a passage 20 in a wall 21 at the entrance to the mixer element, ie at a branch passing through a flow divider element 22 is formed. In 3B the cross-section along the section line II is shown, wherein it can be seen that the liquid flow into two partial streams in a first sub-channel 23 and in a second subchannel 24 is split and behind the flow divider element 22 be reunited in a merger. The merging of the partial flows takes place in a vertical arrangement, so that the horizontally divided partial flows receive a new arrangement to each other.

The one in the wall 21 manufactured passage 20 forms a stage according to this invention and is present in both subchannels of the mixer of this second embodiment to provide equal flow resistance in both subchannels 23 . 24 sure.

In order to achieve the vertical merging of the partial flows, the passage is 21 in the first subchannel 23 arranged substantially in the region of the merger of the sub-channels.

In order for the liquid streams in different flow levels can be introduced into the merger, different levels must be provided for the liquid streams. The dotted areas in the 3A represent a first flow level, which in the 3B marked as E1. The dashed areas of the 3A represent a second flow level, shown in Figure 3B is shown as the second level E2. It can be seen that when merging behind the passage 21 in the first subchannel 23 the first partial flow flows substantially close to the second flow level E2 in the merger, while the second partial flow through the second sub-channel 24 on the first flow level E1 is led to the merge. As a result, the two partial flows lie vertically one above the other.

In the 4A to 4C the process for producing the mixer according to the invention according to the second embodiment is shown. A suitable substrate, but preferably a silicon substrate, becomes a sacrificial layer 26 suitable thickness, which can also be used as Ätzstoppschicht constructed. The sacrificial layer 26 is preferably formed of silicon dioxide. On the sacrificial layer 26 becomes the first functional layer 32 applied, consisting of a starting layer 27 and a first epitaxial layer deposited thereon 28 can be constructed. On this first epitaxial layer 28 becomes a suitable etch stop layer 33 applied and structured as shown. The structuring essentially corresponds to the shaping of the first flow level E1, as in FIG 3B shown.

On the thus prepared layer structure is according to 4B for applying a second functional layer 34 again another start layer 29 and then a second epitaxial layer 30 deposited. On the second epitaxial layer 30 becomes a masking layer 31 so applied that the areas of the inlet channel, the outlet channel and the sub-channels (see 3B ) are accessible to a subsequent etching process, while the remaining areas are substantially unaffected by the etching process. In 4B the layer structure is shown before the depth etching process. In 4C one recognizes the forming structure after the deep etching process. The etching process ends at the etch stop layers 26 . 33 , which are preferably formed of silicon dioxide.

The anisotropic etching step, which is the etch stop layer 26 (Sacrificial layer) exposes to the required areas, etching steps in the layer system, as in 4C shown. The sacrificial layer simultaneously acts as an etch stop layer at which the anisotropic etch step ends. If the sacrificial layer and the etch stop layer are formed in separate layers, it must be ensured that the etching step is in any case etched through the sacrificial layer in order to be able to excise it.

Subsequently, by a suitable selective etching of the sacrificial layer (eg Gasphasenät zen with HF vapor in a silicon layer system with SiO ₂ sacrificial layer) completely removed the sacrificial layer. Since the gas phase etching is isotropic, undercuts of the sacrificial layer occur, with the under the wall 21 sacrificial layer is undercut so far on both sides that the passage 20 is formed.

By then Bonding to an unstructured plate (e.g., wafer) through Anodic bonding or direct bonding, the mixer structure is closed and a mixer formed.

1

supply channel

2

Flow divider element

3

first subchannel

4

second subchannel

5

drain channel

6

first step

7

second step

10

first functional layer

11

etch stop layer

12

second functional layer

13

Photoresist structure

14

unstructured plate

20

passage

21

wall

22

Flow divider element

23

first subchannel

24

second subchannel

25

substratum

26

sacrificial layer

27

first starting layer

28

first epitaxial layer

29

second starting layer

30

second epitaxial layer

31

masking layer

32

first functional layer

33

etch stop layer

34

second functional layer

Claims (16)

Integrated fluidic mixer for mixing through-flowing liquids, with at least one liquid channel ( 1 ) to supply the liquids to be mixed, with at least one branching, to the liquid channel in a first and a second sub-channel ( 4 . 3 . 23 . 24 ), wherein in the first subchannel ( 4 ) a step ( 7 ), the subchannels ( 4 . 3 . 23 . 24 ) are merged behind the branch in a merge, characterized in that the stage in the first subchannel ( 4 . 23 ) is arranged so that a downstream end of the step ( 7 ) essentially at the merger of the two subchannels ( 4 . 3 . 23 . 24 ), wherein the second sub-channel ( 3 . 24 ) is designed so that it has the same flow resistance as the first sub-channel ( 4 ), wherein a limitation of the sub-channels ( 4 . 3 . 23 . 24 ) by a substantially unstructured plate ( 14 ) is formed. Mixer according to claim 1, characterized in that the second sub-channel ( 3 . 24 ) another step ( 6 ), which is designed so that its end facing away from the flow before the merger of the sub-channels ( 4 . 3 . 23 . 24 ) ends and that the further stage ( 6 ) the same flow resistance in the second sub-channel ( 4 ) causes. Mixer according to claim 2, characterized in that the branching and the merging by an arranged in the liquid channel element ( 2 ) is formed. Mixer according to one of claims 2 or 3, characterized by a substantially circular, quadrangular or oval Floor area. Mixer according to one of claims 2 to 4, characterized that the mixer with a substrate of silicon, ceramic, glass and / or plastic is formed. Mixer according to one of claims 2 to 5, characterized in that the stages ( 6 . 7 ) in the subchannels ( 4 . 3 ) are arranged so that the subchannels ( 4 . 3 ) have substantially the same flow resistance. Mixer according to claim 2, characterized in that the stages in the two sub-channels ( 4 . 3 ) are arranged on the same inner wall side. Mixer according to one of claims 2 to 6, characterized in that the step is formed as a passage in a wall structure of the mixer, wherein the passage in the first sub-channel ( 23 ) at a sufficient distance from the merger, z. B. near the branch and in the second sub-channel near the junction is arranged. Mixer according to claim 8, characterized in that behind the passage ( 20 ) in the first subchannel ( 4 . 23 ) the structure of the sub-channel is designed to direct the liquid flow in a first plane and wherein the structure of the second sub-channel ( 3 . 24 ) is designed so that the liquid flow to the corresponding passage ( 20 ) near the merge to dispense the liquid stream in a second plane into the merge. Mixer arrangement with several mixers according to one of claims 1 to 9, which are arranged one behind the other on a substrate. Method for producing a fluidic mixer with a closed mixer structure, wherein in a substrate material via shaping and Separation method introduced an upwardly open mixer structure is, with closing the mixer structure with a substantially unstructured plate is covered to create the closed mixer structure. Method according to claim 11, wherein the mixer structure is provided with a liquid channel ( 1 ) for supplying liquid, with a branch for splitting the liquid channel ( 1 ) into two subchannels ( 4 . 3 . 23 . 24 ) and a stage in at least one of the subchannels ( 4 . 3 . 23 . 24 ) is formed, wherein on a first functional layer ( 32 ) an etch stop layer ( 33 ) is applied and this is structured so that when etching the stages ( 6 . 7 ), wherein on the first functional layer ( 32 ) and the etch stop layer ( 33 ) a second functional layer ( 34 ), wherein a deep etching process is carried out, wherein the second functional layer is etched in accordance with a predetermined channel patterning, wherein the deep etching process is applied to the etching stop layer (10). 33 ) is stopped and the first functional layer ( 32 ) according to the structuring of the etching stop layer ( 33 ) is etched. The method of claim 12, wherein the first functional layer ( 32 ) on the substrate ( 25 ) or in the substrate ( 25 ) is included. The method of claim 12 or 13, wherein the surface of the second functional layer ( 34 ) is processed so that a bondable surface is formed, wherein the unstructured plate is bonded to the bondable surface. The method of claim 10, wherein the mixer structure is provided with a fluid channel ( 1 ) for supplying liquid, with a branch for dividing the liquid channel into two sub-channels ( 4 . 3 . 23 . 24 ) and with steps ( 7 . 6 ) in each of the subchannels ( 4 . 3 . 23 . 24 ), wherein on a substrate ( 25 ) a sacrificial layer ( 26 ), wherein a first functional layer ( 32 ) on the sacrificial layer ( 26 ) is applied, wherein an etch stop layer ( 33 ) to the first functional layer ( 32 ) is applied and this is structured, wherein on the first functional layer ( 32 ) and the patterned etch stop layer ( 33 ) a second functional layer ( 34 ), wherein a deep etching process is carried out, wherein the first and the second functional layer ( 34 ) is etched according to a predetermined channel patterning, wherein the depth etching process is applied to the etch stop layer ( 33 ) is stopped so that the covered first functional layer ( 32 ) remains, wherein after throughputs of the first functional layer ( 32 ) the sacrificial layer ( 26 ) is etched, with undercuts below the first functional layer ( 32 ), wherein under one through the first functional layer ( 32 ) wall structure the sacrificial layer ( 26 ) is substantially etched so that a passage through the wall structure is formed. Method according to one of claims 9 to 13, characterized in that the functional layers ( 32 . 34 ) of silicon, preferably of an epipoly layer system with a starting layer ( 27 . 29 ) and a polycrystalline silicon layer ( 28 . 30 ), and that the etching stop layers ( 33 ) are formed of silicon dioxide.