ES2310967B2 - MANUFACTURING METHOD FOR M ICROMETRIC SCALE FLUID FOCUSING DEVICE - Google Patents

Abstract

Manufacturing method for focusing device of micrometric scale fluid.

The object of the present invention is a manufacturing procedure for a device intended for dispersion of a fluid, called focused, in another or others, called focusing, accurately and controlled on a micrometric scale using the technique known as "flow focusing" and devices manufactured according to that procedure. The object method of the present invention allows the manufacture of a device capable of producing coaxial fluid currents (three-dimensional encapsulation). The manufacturing process, based on standard techniques in microsystem technology (systems microelectromechanical or MEMS, Micro Electro Mechanical Systems), allows mass production of dispersion devices with micrometric precision, at low cost, and with a very large size reduced.

The manufactured device can easily be integrated in two-dimensional matrices, being able to create flows coaxial in the direction perpendicular to the matrix of dispositives.

Description

Manufacturing method for focusing device of micrometric scale fluid.

Object of the invention

The object of the present invention is a manufacturing procedure for a device intended for dispersion of a fluid, called focused, in another or others, called  focusing, accurately and controlled on a scale micrometric using the technique known as "flow focusing" and devices manufactured according to that procedure.

The method object of the present invention allows in a simple way the manufacture of a device capable of producing coaxial currents of fluids (three-dimensional encapsulation). The manufacturing process, based on standard techniques in microsystem technology (microelectromechanical systems or MEMS, Micro Electro Mechanical
Systems), allows the mass production of dispersion devices with micrometric precision, at low cost, and with a very small size.

The manufactured device can easily be integrated in two-dimensional matrices, being able to create flows coaxial in the direction perpendicular to the matrix of dispositives.

State of the art

The technique known as Flow-Focusing, or fluid focusing, is a mechanical method for the production of very small jets diameter. Depending on the method's application, you can get a stable jet, or it can be forced to break in micro droplets of controlled size. The technique is based on wrapping the liquid jet with another immiscible fluid with the first, of so that it flows coaxially with said immiscible fluid (or focusing) It is also possible to use a liquid as a fluid envelope and that the focused fluid is a gas.

The main applications of encapsulation of fluid are the following:

one.

Aerosol generation By dispersing a liquid in the air it is possible to generate drops with very controlled and homogeneous sizes. The diameters of the drops generated can vary between hundreds of microns and tens of nanometers.

2.

Bubble generation If the focused fluid is a gas and the focusing fluid is a liquid, then bubbles are generated, the size of which is perfectly uniform and can be controlled.

3.

Generation of foams and emulsions . By applying the two methods described in the previous sections, highly efficient production of emulsions and foams is possible.

Four.

Production of complex particles . If the technique of coaxial jets of immiscible fluids is applied two or more times successively, and its rupture in drops is caused, the production of fluid drops containing other drops inside it can be achieved. These particles find application in the dispensing of medicines, whose active principle would be inside, and would be surrounded by a protective material that would dissolve, releasing said active principle in a controlled manner.

6.

Particle analysis . A particle analyzer is able to measure the spectrum-photometric properties of the circulating particles. To achieve a linear flow of particles, it is usual to force the fluid that contains them to flow surrounded by another coaxial current. In this way a highly stable jet of predetermined dimensions is achieved.

7.

Flow cytometry In the event that the particles analyzed according to the method described in the previous section are cells of an animal or plant organism, the technique is called flow cytometry.

There are several known techniques and devices for two-dimensional fluid focusing (see, for example, the US20040043506, inventors Haussecker and Sundarajan). The manufacturing techniques commonly used for these devices allow linear groupings of them, but they make it extremely difficult to make a two-dimensional matrix of devices.

Devices and their corresponding manufacturing processes have also been previously designed to achieve three-dimensional fluid encapsulation (see Sundarajan et al ., IEEE J. Microelectromech. Syst., Vol. 13, no. 4, pp. 559-567). Until now, the manufacturing processes and materials used for these devices do not allow the grouping of several forming a two-dimensional matrix.

The integration of the devices of matrix encapsulation offers the advantage of allowing increased production in the unit of time, increasing the Global system efficiency.

Other manufacturing processes for devices of encapsulation integrable in matrices have been published previously (for example, patent ES2199048, inventor Gañán-Calvo), but they are complex and the level of integration achieved is small, given the difficulty of small-scale machining of the materials on which they are based, mainly metals.

The high number of patents and publications scientific oriented to the achievement of a device of flow focusing that can be easily manufactured at small scale and be integrable in matrices demonstrates the usefulness of said device.

As for the manufacturing processes of micrometric devices, these are classified as machining, engraved and molded. Traditional machining techniques do not They are usually suitable for the construction of a device such as described, since they lack the necessary precision, and also do not they have the economy of scale necessary to manufacture large low cost quantities. Molding processes are used to manufacture complex geometry devices using materials moldable, but currently they are not so widely used for manufacture microsystems such as engraving processes. The processes of engraving, which are used in the manufacturing method subject to The present invention evolve from the manufacturing techniques of  integrated circuits in microelectronics, and are based on chemical reactions that remove material from a substrate. They can be classified as surface engraving or volume, depending on the geometry of the material to be engraved. In turn, engraving techniques by volume they are divided into wet etch (when the reagent that removes material is in liquid phase) and dry etching (when in any other phase, usually gas).

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Description of the invention

The manufacturing method described is intended for the manufacture of a device that has two inputs of fluid and a single outlet, through which both will go outside inlet fluids The internal geometric configuration enables performing the technique known as "flow-focusing", in which one of the fluids, called focusing, completely surrounds the other fluid, called focused, so that it is dragged concentrically by the focusing in the form of a capillary micro-jet or of microscopic drops, the size of these being determined by the flow conditions (flow rate) of both focusing fluids and in focus.

This device has uses in sectors of the technique such as the pharmaceutical industry (drug encapsulation), materials science and engineering, the food industry, the Chemical industry, biotechnology, and instrumentation scientific

Some of the device's applications are the generation of microsprays, microdrops, and foams, as well as the creation of complex particles, and particle analysis or cells.

The advantages of the method object of the Present invention with respect to other previous inventions are:

-

It allows manufacturing in a simple way of a device capable of producing coaxial fluid currents (focused three-dimensional), what other methods developed previously they are not able to perform.

-

He manufacturing process, based on standard techniques in technology  microsystems, allows mass production of devices dispersion with a low cost, and with a very small size (being dimensions in the order of microns).

-

He manufactured device can be easily integrated into matrices two-dimensional, and can also create coaxial flows in the address perpendicular to the array of devices.

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The device object of the invention consists of in two wafers that have been mechanized and joined for encapsulation of fluids, as shown in figure 2. In the Wafer (1) there is a hole (4) where the focused fluid rises. The focusing fluid is supplied through the duct (6) to reach the cylindrical structure (5) responsible for driving the focused fluid This geometry guarantees the encapsulation of the focused fluid by the focusing fluid. Both fluids come out through the discharge hole (3) of the upper wafer (2).

The manufacturing process of the invention is the following (see figure 5):

one.

Be make an engraving on a silicon wafer (wafer # 1) using a RIE reactor (Reactive Ion Etching), to realize channels of distribution of the focusing fluid. The engraving is done starting from A side of the wafer. To define the way to record is done first a photolithography stage on the same face A, using a mask that contains the shape of the channels, and by which areas that do not want to record are protected.

2.

Using the same mask as in the step 1, photolithography is performed on face B of wafer # 1, and they record the unprotected areas, creating a mirror image of the existing channels on side B, with a smaller depth. This Image will be used later for alignment between masks in other stages of photolithography.

3.

Since the B side of wafer # 1 returns to another stage of photolithography, aligning the mask with the copy of the channels made in step 2, and then the wafer is recorded on all its thickness using RIE. This creates the necessary step to the focused fluid.

Four.

In a # 2 wafer is made an RIE engraving from its face B, defining previously the form by photolithography. The depth of this engraving determines the separation between the upper end of the cylindrical surface (5) and the upper wafer (2).

5.

The two wafers are joined by a physical or chemical bonding process hermetic, for example silicon fusion bonding, or bonding anodic

6.

In the Wafer # 2 defines an area on its upper face by photolithography, and through RIE a through hole is made that communicate the outside with the cavity created inside the two wafers This hole must be aligned with the hole through the interior of the cylindrical structure (5) and will allow the outflow of focused and focusing fluids once the encapsulation

7.

Additionally, in step 6 you can machining wafer # 2 to perform the discharge nozzle (9) of the Figure 3, or to reduce its thickness.

8.

It is also possible to machine the wafer # 1 on its underside to define by photolithography a network of channels of distribution of the focused fluid, leading to it until the entrance of the internal hole to the structure cylindrical

Description of the figures

Figure one

Fluid Focusing Concept

In the figure, (7) is the focusing fluid and (8) the focused fluid.

Figure 2

Device section

The device consists of two wafers: bottom # 1 (1) and higher # 2 (2), which have been micromachined and joined. In the bottom wafer (1) has been carved a cylindrical surface (5) and a backwater chamber that surrounds it from the upper face. From the bottom side of the wafer (1) two holes have been opened inlet for focused fluid (4) and focusing fluid (6). In the upper wafer (2) an outlet opening (3) has been opened which is is aligned with the fluid inlet port focused (4). The focused fluid enters through (4) while the fluid focusing enters through (6). The cylindrical shape in (5) makes the focusing fluid wrap the focused fluid and let both come out the hole (3).

Figure 3

Device section, with alternative geometry for exit

The discharge hole may present different output geometries. Figure 3 shows a conical outlet (9). Other profiles in the discharge nozzle are possible.

Figure 4

Arrangement of several integrated devices forming a matrix

This figure shows how the devices they can be manufactured from the same substrate, distributed in a flat, and with the outlet of the encapsulated fluid perpendicular to said flat.

Figure 5

Fabrication process

The drawing (a) shows the reduction made initially in a bottom wafer # 1 to create the surface cylindrical and the backwater chamber. The drawing (b) shows the engraving from the bottom face to finish the inner hole to the cylindrical surface (where the focused fluid will circulate) and the inlet hole of the focusing fluid. Drawing (c) shows the recess made in the upper wafer # 2, and that determines the separation between the cylindrical surface and the cover. The drawing (d) shows the union of the two mechanized wafers so far. He drawing (e) shows the final device, after performing the exit hole in the upper wafer.

Embodiment of the invention

An example of how to explain embodiment of the present invention which is not intended to be nor exhaustive or limit the field covered by the present invention, and only included by way of illustration, the field being limited only by the claims set forth at the end.

The manufacturing method is similar to what has been previously described. As these are standard techniques of microsystem manufacturing, the optimal dimensions for this manufacturing method range from a few micrometers to tens or hundreds. The manufacturing process of a typical device consists in:

1st.

Photolithography of a lower wafer of silicon 380 micrometers thick, defining a network of distribution channels of variable-width thickening fluid and between 100 and 400 micrometers.

1 B.

RIE engraving of the wafer, with a 180 micrometer depth (um) in the areas defined by the previous photolithography

2nd.

Photolithography on the opposite face (bottom) of the same wafer using the same mask as in the step 1st.

2b

Engraving of the wafer on the face bottom, with a depth of 5 um to use as a pattern of alignment.

3rd.

Photolithography from the lower face using a new mask and aligning it with the patterns made in step 2b, defining holes of 50 um in diameter, which are they will use as channels for the focused fluid.

3b

Deep engraving of the Wafer from the underside in the areas defined by the Photolithography done in 3rd. The engraving depth is the necessary to completely traverse the entire thickness of the wafer, in this case 380 um.

4th.

In a new superior silicon wafer 380 um thick is made a photolithography on the lower face, defining the areas in the that the focusing fluid meets the focused. These areas they have a diameter of 600 um.

4b

Engraving of the wafer in the zones defined in the previous photolithography, with a depth of 20 um.

5.

Union by fusion of the two silicon wafers, with the second wafer on top from the first.

6.

Reduction by machining the thickness of the second wafer, until the resulting thickness is 20 um.

7a.

Photolithography on the upper face of the set formed by the two wafers, defining the holes of outlet, with a diameter of 50 um.

7b

Deep engraving of the second wafer from its upper face in the areas defined by photolithography anterior, with the depth necessary to drill the wafer in its totality (in this case 20 um).

Claims (15)

1. Method of manufacturing a fogging device by capillary fluid focusing consisting of n discharge mouths, through which a focused fluid exits, located in one or several backwater chambers and facing n exit holes through from which the focused fluid and one or more focusing fluids, characterized in that it comprises the following threads in the order indicated or in any other:

to.

an engraving or etching on the A side of a wafer # 1 in one or more stages, defined on its surface one or more cameras haven within defined n discharge outlets, n being greater than or equal performed that one; to define the form to be recorded, a photolithography stage is first performed;

b.

a etching or chemical attack is carried out on wafer # 1 which, in one or several stages, defines (i) one or more focusing fluid inlets that directly or indirectly feed all the backwater chambers and (ii) n fluid inlets focused that feed the n discharge mouths; to define the form to be recorded, a photolithography stage is first performed;

C.

a etching or chemical attack is carried out on the A-side of wafer # 1 which, in one or several stages, defines one or more channels that allow the focusing fluid to be distributed from the focuser inlet or channels to each of the backwater chambers where are the n discharge mouths; to define the form to be recorded, a photolithography stage is first performed;

d.

a etching or chemical attack is carried out on the B side of wafer # 1 which, in one or several stages, defines a distribution network with or without channels that allow the focused fluid to be distributed to each of the n focused fluid inlets from one or more general entries; It is considered a particular case of this network of channels that there is a general input for each focusing input; to define the form to be recorded, a photolithography stage is first performed;

and.

an engraving or etching on a wafer # 2, in one or more stages, n defines the outlet orifices of the device is; to define the form to be recorded, a photolithography stage is first performed;

F.

an engraving or etching on the side B of the wafer # 2, in one or more stages, lowers the thickness of the plate in the vicinity of the n outlet orifices in an amount equal to or greater than 0 mm is performed; to define the form to be recorded, a photolithography stage is first performed;

g.

a physical or chemical method is used to join the face A of the wafer # 1 to the face B of the wafer # 2, so that the n discharge mouths are aligned with the n exit holes, being separated by a certain distance by the recess of face B of wafer # 2 and the height of the discharge mouth of wafer # 1.

2. Method of manufacturing a fogging device by capillary fluid focusing consisting of n discharge mouths through which a focused fluid exits, located in one or several backwater chambers and facing n exit holes through which the focused fluid and one or several focusing fluids, according to claim 1, characterized in that it comprises the following threads in the order indicated or in any other:

to.

a chemical etching is carried out by means of an RIE reactor (reactive ion etching) on the A side of a # 1 silicon wafer that, in one or several stages, defines on its surface one or several backwater chambers within which n discharge mouths, being n greater than or equal to one; to define the form to be recorded, a photolithography stage is first performed using the necessary masks;

b.

previously defining the shape and alignment by photolithography, a chemical etching is carried out by means of the RIE reactor on wafer # 1 which, in one or several stages, defines (i) one or several focusing fluid inlets that directly or indirectly feed all the chambers backwater and (ii) n focused fluid inlets that feed the n discharge mouths;

C.

previously defining the shape and alignment by photolithography, a chemical etching is carried out by means of the RIE reactor on the A side of wafer # 1 which, in one or several stages, defines one or several channels that allow the focusing fluid to be distributed from the inlet (s) focusing on each of the backwater chambers where the n discharge mouths are located;

d.

previously defining the shape and alignment by photolithography, a chemical etching is performed by means of the RIE reactor on the B side of wafer # 1 which, in one or several stages, defines a distribution network with or without channels that allow the focused fluid to be distributed to each of the n fluid inlets focused from one or more general inlets; It is considered a particular case of this network of channels that there is a general input for each focusing input;

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and.

previously defining the shape and alignment by photolithography, chemical etching is conducted by RIE reactor on a silicon wafer # 2, in one or more stages, n defines the outlet ports of the device;

F.

previously defining the shape and alignment by photolithography, chemical etching is conducted by reactor RIE on the side B of the wafer # 2, in one or more stages, lowers the thickness of the plate in the vicinity of the n exit holes an amount equal to or greater than 0 mm;

g.

a fusion bonding method is used to join the A-side of wafer # 1 to the B-side of wafer # 2, so that the n discharge nozzles are aligned with the n exit holes, being separated by a distance determined by the recess of face B of wafer # 2 and the height of the discharge mouth of wafer # 1.

3. Method according to claim 1 characterized in that one or more of its stages are performed by laser ablation instead of chemical attack with photolithography stages. 4. Method according to claims 1-3, characterized in that the discharge mouth obtained is a tube of circular section, or a conduit of variable section with a three-dimensional geometry, including truncated conical, pyramidal, axyl-symmetrical shapes with curved generatrix or combinations of the same. 5. Method according to claims 1-3, characterized in that the outlet orifice obtained is of circular section along its entire length or has a variable section and a three-dimensional geometry, including truncated conical, pyramidal, axilsymmetric shapes with a curved generatrix, nozzles convergent, divergent nozzles, convergent-divergent nozzles or combinations thereof. Method according to claims 1-3, characterized in that the joining of the two wafers is carried out by means of chemical fusion, anodic bonding, conventional adhesives, mechanical bonding or other procedures that ensure the fixation of the geometry and the absence of interstitial leaks. . 7. Method according to claims 1-3, characterized in that the wafer # 1 and / or # 2 are subjected at some time to one or more additional stages of physical or chemical processing, in particular physical-chemical milling, conventional machining, laser ablation, which allow varying the thickness of the wafer, the shape of the exit holes, the shape of the channels and / or the discharge mouths. 8. Fogging device characterized by being manufactured according to the procedures of claims 1-7. 9. Device according to claim 8, characterized in that the base material on which the structures are formed is silicon and that the engraving techniques used on the wafers are conventional techniques in the manufacture of microsystems. 10. Device according to claim 8, characterized in that the base material on which the structures are formed is glass, composite, plastic, or any other material capable of being mechanized by chemical attack or etching according to the described procedure. 11. Device according to claim 8, characterized in that n is equal to 1 and, therefore, the device consists of a single discharge port and a single outlet opening. 12. Device according to claim 8, characterized in that the direction of the fluid focused inside the discharge mouth is essentially perpendicular to the two wafers. 13. Device according to claim 8, characterized in that the inlet of the focused fluid comes from another fluid focusing device according to claim 8, said input being therefore constituted by a focused fluid and a focusing fluid. In this way, the focus of three fluids is achieved simultaneously. The complete device can be constructed by stacking two devices as described in claim 8, so that the output of the two encapsulated fluids of the lower device is connected to the fluid inlet or the upper device. 14. Device according to claim 8, characterized in that it consists of electrodes that allow establishing a difference in electrical potential between the outlet port and the discharge port, so that the generated electric field causes effects on the formation and breakage of the micro-focused jet. 15. Device according to claim 8, characterized in that the focusing fluid inlet (s) that feed the backwater chambers or chambers are located on side B or on the side face of wafer # 1.