WO2003068381A1

WO2003068381A1 - Method for producing monodispersed nanodrops or nanoparticles and two devices for carrying out said method

Info

Publication number: WO2003068381A1
Application number: PCT/EP2003/001418
Authority: WO
Inventors: Steffen Hardt; Volker Hessel
Original assignee: INSTITUT FüR MIKROTECHNIK MAINZ GMBH
Priority date: 2002-02-13
Filing date: 2003-02-13
Publication date: 2003-08-21
Also published as: DE10206083A1; DE10206083B4

Abstract

The invention relates to a method and a device for producing monodispersed nanodrops. The aim of the invention is to obtain a size distribution which can be better controlled, and a more regular form of the nanodrops, than that obtained by the already known methods and devices. The inventive method for producing monodispersed nanodrops is characterised in that an immiscible second fluid B is introduced into a continuously flowing fluid A, fluid B is surrounded by fluid A, and the flow cross-section (16, 25) of fluid B diminishes in the direction of flow (2) in such a way that fluid B disintegrates into individual drops (26) as a result of its hydrodynamic instability. The invention also relates to a microfluidic reactor for carrying out the method in which a fluid A is introduced into a fluid B in a first continuous fluid flow, fluid B is surrounded by fluid A, and fluids A and B are immiscible. Said microfluidic reactor is characterised by a focussing module (1) comprising a receiving hopper (3) which tapers off in the flow direction (2). A drop forming channel (5) is connected to the small opening end (4) of said receiving hopper.

Description

METHOD FOR PRODUCING MONODISPERSE NANOTROPS OR NANOPARTICLES, AND TWO DEVICES FOR IMPLEMENTING THE METHOD

The invention relates to a method for producing monodisperse nanodroplets and to a microfluidic reactor for carrying out the method.

The production of nanoparticles and nano drops by means of diffusion or low pressure flames is described, for example, in "Parametric study of zirconia nanoparticle synthesis in low pressure flames", A. Colibaba-Evulet et al., Scripta mater. 44 (2001) 2259-2262. The interaction of the parameters pressure, temperature and flow rate with regard to the particle geometry is examined in particular.

In the publication "In site characterization of TiO _> nanoparticle in chemical vapor reactor", JHYu et al. scripta mater. (2001) 2213-2217, a method for producing nanoparticles is presented which is based on a chemical precipitation reaction in emulsions. The focus of the investigation was the size distribution of TiO ₂ particles as a function of the oxygen supplied, with the result that the synthetic TiO ₂ particles become smaller and narrower in their size distribution due to flocculation as the inflow of oxygen increases.

A method and a device for producing nanoparticles is described in the publication "Aero-sol-gel Reactor for nano-powder-synthesis" by G. Beaucage et al., Journal of Nanoparticle Research 1 (1999) 379-392. Here, the nanoparticles are generated by sol-gel reactions in aerosols. The Aero-Sol-Gel reactor allows the structure, chemical composition and outer surface of silicon oxide powders to be influenced by changing the process parameters. The Aero-Sol-Gel reactor contains a dry nitrogen, which is bubbled through precursor liquids to form steam flows. The The blowing device can be heated to control the concentrations of the reactants in the feed streams. In the formation process of silicon oxide from tetraethoxysilane (TEOS), three steam flows are given up in a laminar flow, namely TEOS, water and hydrochloric acid. All process steam flows are heated to approx. 110 ° C to prevent premature condensation. The laminar flows flow into an air mix / condensation / reaction zone, which is similar to that of pyrolytic reactors. The nano-structured powders are then collected in a funnel-shaped filter.

The main disadvantage of the known methods is the poor controllability of the particle size and shape. The size and size distribution of the particles largely depends on the reaction conditions, such as temperature, pressure and concentrations, which as a rule cannot be set arbitrarily. The same applies to the shape of the particles.

Accordingly, the object of the invention was to develop a method with which nanotropic droplets or nanoparticles of spherical geometry and a defined size can be produced. Another subtask consists in providing a microfluidic reactor for performing the method.

The object is achieved with a method in which an immiscible second fluid B is introduced into a continuously flowing first fluid A, in which the fluid B is surrounded by the fluid A and in which the flow cross section of the fluid B is tapered in the direction of flow, that the fluid B disintegrates into individual drops due to its hydrodynamic instability. The main advantage of this method is the ability to change the size of the fluid simply by selecting the fluid flow rates without having to make any changes to a device to be able to control the resulting particles. At the same time, the optimally desired spherical shape of the particles with a predeterminable particle size is achieved.

The fluids A, B are advantageously accelerated in a focusing module by a geometric cross-sectional reduction and fed to a drop formation channel with a constant opening width. The geometric cross-sectional reduction in the focusing module is an easy-to-implement option for tapering the flow cross-section of the fluids in the direction of flow. The geometric cross-sectional reduction can be achieved using a decreasing cross-section, e.g. a funnel or via a step-like reduction in the opening width. In the case of a step-like reduction in the opening width, stationary vortices can form in the storage space of the steps, but these have no influence on the principle of action.

In an alternative method, in a focusing module, instead of the geometric cross-sectional reduction described above, a fluid A is supplied to a fluid stream B via inlet openings distributed in the flow direction. This significantly reduces the risk of blockages due to particles already forming in the drop formation channel.

After flowing through the focusing module, the fluid A is preferably returned in a return flow channel against the flow direction. As a result, the fluid A can be reused and its consumption can be minimized.

A control fluid X is advantageously introduced into the fluid A via an access. In this way, the location of the drop formation in the drop formation channel can be influenced, since the location of the drop formation depends not only on the size of the flow cross section, but also on material parameters such as density, viscosity and surface tension. By adding a control fluid X, for example, the interfacial tension between the fluids A and B could be changed and the drop formation of the fluid B could thus be triggered. The control fluid X thus contributes to further optimizing the formation process of nano drops with regard to its geometric specifications.

The fluids A, B are advantageously fed to the focusing module via a distributor module. The distributor module is used to apply the fluids A, B with defined initial conditions.

Preferably, a plurality of parallel-spaced fluid streams B are emitted from the distributor module into the focusing module. By parallelizing the drop formation, the flow rate and thus the conversion can be increased and the pressure drop reduced. With only one fluid flow B, the drop formation channel has a very small flow cross section. In contrast, several fluid flows B allow a larger flow cross section.

A force is advantageously exerted on electrically conductive fluids A, B by means of a magnetic coil or a solid-state magnet. As a result, the electrically conductive fluids A, B flow through a magnetic field in which they are stabilized. With the help of the magnetic field, for example, premature decay into drops could be prevented. Both magnetic coils and solid-state magnets can be used to generate the magnetic field.

The fluids A, B are advantageously irradiated with a laser. Fluid B could be heated with the help of the laser, which in turn changes the properties of the material. In this way, the location of the drop formation in the drop formation channel can be influenced. The method can also be carried out advantageously by supplying the focusing module with a third fluid C, the fluid B being chosen to be hydrodynamically unstable than the fluid C. Fluid B and fluid B should be surrounded by fluid A in the direction of flow of the fluid C, ie the fluid streams should be nested within one another. This type of fluid application, in conjunction with the requirement that the fluid B is more hydrodynamically unstable than the fluid C, enables concentric drops of the fluid C in the fluid B. The fluid C is completely surrounded by the fluid B.

Another alternative can also be useful, in which the fluid C is chosen to be more unstable than the fluid B. This can then be used to generate drops of fluid B which contain a number of smaller drops C.

A voltage can advantageously be impressed into the fluids A, B, at least one fluid A or fluid B having electrolytic properties. As a result, a defined electrical charge can be applied to the fluid A or fluid B, as a result of which drop agglomerations and drop coalescence are prevented. For example, the outer fluid A and the inner fluid B can be in contact with an anode and a cathode, one of which is located in the region of the distributor module and the other in the region of the reaction module. If Fluid B has electrolytic properties and there is an electrode at the reactor inlet, charges in Fluid B migrate away from the electrode to the location of the drop formation. As a result, a defined charge is applied to the drops, which prevents the drops from coalescing and makes it possible to collect the drops or the particles formed from the drops on the counterelectrode.

It has proven to be particularly favorable to convert the drops into particles in a reaction module in order to produce nanoparticles from nanodrops. The conversion of the monodisperse nano drops into Nanoparticles enable the production of nanoparticles with a very narrow particle size distribution and a very regular spheroidal shape. Nanoparticles which are produced by the processes known from the prior art do not achieve such a narrow particle size distribution and particle shape. Furthermore, the size of the nanoparticles can be controlled very precisely with the method according to the invention through the choice of the geometric cross-sectional reduction or the setting of the hydrodynamic conditions and the choice of the quantitative ratios of the fluids. In addition, the process can process many more different substances into nanoparticles than with the already known processes, which all only take place under extreme and very narrow process conditions. Nanoparticles produced by the method according to the invention are of great importance for many relatively new fields of application, such as coatings for surfaces, catalysts, etc.

The particles are preferably generated in the reaction module by polymerization. This permits spatial separation of the process steps, formation of the drops in the drop formation channel and formation of the particles in the subsequent reaction module.

A solution of monomers is advantageously used as fluid B. When particles are formed by polymerization, monomers are in the form of a fluid.

The polymerization is preferably induced by adding initiators. With the addition of initiators, the location and time of particle formation can be controlled. The polymerization is favorably induced by introducing heat or light. Both possibilities represent simple methods to initiate the polymerization and thus the formation of the particles.

The subtask is solved with a microfluidic reactor in which a second fluid stream of a fluid B is introduced in a first continuous fluid stream of a fluid A, the fluid B being surrounded by fluid A and the fluids A, B being immiscible and in the one Focusing module is formed with an inlet funnel tapering in the direction of flow, to which a drop formation channel is connected at its small opening end. The device constructed in this way enables a defined generation of nanotropes or nanoparticles with a spherical geometry and a defined size. In addition, the microfluidic reactor does not require small, difficult-to-manufacture microstructures for shaping the fluid streams, which can be chosen to be larger than the nanotropes or nanoparticles, which in particular reduces the manufacturing outlay. The focusing module does not necessarily have to have an inlet funnel that continuously narrows in the narrower sense. The tapering of the fluid cross-sections can also be achieved by step-like cross-sectional constrictions in the focusing module.

In a preferred embodiment, a distributor module for supplying the fluids A, B into the focusing module is formed with a plurality of outlet channels of the fluid A and outlet channels of the fluid B.

The outlet channels of the fluid B preferably have an opening width of 100 nm to 500 μm, an opening width of 1 μm to 100 μm having been found to be particularly advantageous.

In a special embodiment, the drop formation channel has the opening width of the small opening end of the inlet channel. In another alternative embodiment of the microfluidic reactor, a second fluid stream of a fluid B is introduced in a first continuous fluid stream of a fluid A, the fluid B being completely surrounded by the fluid A and the fluids A, B being immiscible and in a focusing module a substantially constant opening width, in which inlet openings for supplying the fluid A are arranged offset in the flow direction in at least one peripheral wall of the focusing module, and in which a drop formation channel is connected to the focusing module. Such a microfluidic reactor focuses the fluid flows hydrodynamically. As a result, the microfluidic reactors can be provided with larger structures that are easier to manufacture, since the cross section of the second fluid flow is not tapered by the geometry of the microfluidic reactor, but by a repeated metering in of the fluid A.

The focusing module of the microfluidic reactor described above preferably has separating structures for delimiting a backflow channel. The separation structures enable better guidance of the fluid A.

It has proven to be expedient to form accesses in the peripheral wall for the task of a third control fluid X miscible with fluid A.

A reaction module is advantageously connected to the drop formation channel in the flow direction.

In a special embodiment, the reaction module has inlet openings through which, for example, initiators for initiating a polymerization can be added. This allows the location and time of particle formation to be controlled. The reaction module preferably comprises a heat or light source in order to initiate the polymerization reaction and thus the formation of the particles.

A magnet coil is advantageously arranged on the focusing module. A magnetic field is built up via the magnetic coil, which stabilizes the electrically conductive fluids and prevents premature decay in the drop. A solid-state magnet can also be used instead of the magnetic coil.

A laser is advantageously arranged on the drop formation channel. The two fluids A, B can be heated by means of the laser, as a result of which the material properties change. In this way, the location of the drop formation can be influenced.

In a favorable embodiment, an electrode is attached to each of the distributor module and the reaction module, with which a voltage can be impressed into the fluids A, B.

The invention is explained in more detail by way of example with reference to the following figures. They show:

Figure 1 is a schematic representation of a microfluidic reactor according to a first embodiment;

FIG. 2 shows a schematic illustration of a microfluidic reactor according to a first embodiment with a plurality of parallel flows of the fluid B;

FIG. 3 shows a microfluidic reactor according to FIG. 2 with a magnetic coil arranged outside the reactor; FIG. 4 shows a microfluidic reactor according to FIG. 2 with a laser;

Figure 5 is a schematic representation of a microfluidic reactor according to the first embodiment for encapsulating a third fluid C;

FIG. 6 shows a microfluidic reactor according to FIG. 1 with electrodes on the distributor module and reaction module;

FIG. 7 shows a schematic illustration of a microfluidic reactor according to a second embodiment;

FIG. 8 shows a microfluidic reactor according to FIG. 7 with two opposite return flow channels; and

Figure 9 is a schematic representation of a microfluidic reactor with inlet openings for the control fluid X.

FIG. 1 schematically shows a microfluidic reactor according to a first embodiment, in which the flow of the fluids A, B is focused by the geometric configuration of the reactor. Starting from the distributor module 6, in which the fluid A is fed via the outlet channels 7 and the fluid B via the outlet channel 8 into the focusing module 1, the fluids A, B flow in the flow direction 2 through a cross-sectional reduction 27 into the drop formation channel 5. The Outlet channel 8 of the fluid B has an opening width 9 in the region of the transition into the focusing module 1, the dimension of which is typically a few micrometers. Due to the arrangement of the outlet channels 7 on both sides of the outlet channel 8, the fluid B is surrounded on both sides by the fluid A. Due to the geometric cross-sectional widening 27 from the opening width 11 of the focusing module 1 to the opening width 10 of the drop formation channel 5, there is a narrowed flow cross-section 16 of the fluid B. The geometric cross-sectional widening 27 can take place in one or in two spatial directions. In Figure 1, the funnel walls 30 are shown perpendicular to the drop formation channel 5, so that a vortex or dead water zone 29 is formed. The inclination of the funnel walls 30 with the end 31 on the peripheral wall side in the direction of the distributor module 6 can reduce or avoid the formation of the vortex and dead water zone 29.

Within the drop formation channel 5, which has a constant opening width 10, individual drops 26 are detached from the previously continuous flow of the fluid B.

A reaction module 17 is connected to the drop formation channel 5 in order to generate particles 28 from drops 26. The droplets 5 of the fluid B, together with the fluid A, reach the reaction module 17 via the inlet opening 18. The actual particle formation takes place, for example, by polymerization under the influence of heat. In the exemplary embodiment, the heat is generated via a heat source 19 arranged outside the peripheral wall 32 of the reactor module 17.

FIG. 2 also shows a microfluidic reactor according to the first embodiment, that is to say with a geometrical focusing, but a plurality of parallel flows of the fluid A and the fluid B are alternately fed into the distributor module 6. As a result, the throughput of the fluids and thus the output on the droplet 26 or particles 28 (not shown) is increased. In a departure from the embodiment shown in FIG. 1, the funnel walls 30 run toward one another in an arc shape in the direction of the small opening end 4 of the inlet funnel 3.

A reaction module 17 could follow the drop formation channel 5 to form particles 28 from the drops 26, but this is not shown in FIG. 2.

FIG. 3 shows an embodiment of the microfluidic reactor according to FIG. 2 with a magnet coil 21 which is arranged in the region of the peripheral wall 12 and is suitable for forming an axial magnetic field 24. With the help of the magnetic field 24, a force is exerted on the fluid B if its electrical conductivity is different from zero. A finite conductivity could be achieved with the help of an electrolyte. It is known from magnetohydrodynamics that a sufficiently strong magnetic field can prevent a breakdown of fluid flows. It is thus possible to stabilize the flows of the fluid B in the focus module 1 and to limit the effect of the hydrodynamic instability and thus the formation of drops 26 on the drop formation channel 5.

FIG. 4 also shows a first embodiment of the microfluidic reactor, in which, however, a laser 22 is arranged in the area of the drop formation channel 5. The pulsed laser embosses a periodic temperature profile on the streams of fluid B flowing through the drop formation channel 5. The wavelength of the temperature profile makes it possible to determine the decay wavelength. In turn, the size of the drops 26 can thus be influenced and variations beyond the ratio of drop size to size of the fluid flow of the fluid B which is characteristic of the undisturbed dynamics are possible. In this context, selective influencing of specific fluids can be achieved by tuning the laser wavelength to the absorption bands of the molecules of the fluid B. In FIG. 5, the distributor module 6 has an additional possibility of nesting a third fluid C in the fluid B, and in turn enclosing it surrounded by the fluid A. Such a microfluidic reactor offers the possibility of producing drops 26 or particles 28 (not shown) made up of several layers. For this it is necessary to choose the material properties so that the formation of drops 26 of the fluid B takes place before the decay of the fluid flow of fluid C. In this case, the drops 26 or particles 28 (not shown) have a core 33 around a shell 34 made of different materials.

FIG. 6 shows a microfluidic reactor according to the first embodiment, to whose distributor module 6 cathodes 23a and in the area of the reaction module 17 an anode 23b are attached. The field lines 36 are drawn as broken lines from the cathodes 23a to the anode 23b. In the exemplary embodiment, negative charges migrate in the fluid B having electrolytic properties from the cathode 23a to the location of the drops 26 in the drop formation channel 5. This brings a defined negative charge onto the drops, which prevents the drops 26 from coalescing and entering Collecting the drops 26 or the particles 28 at the anode 23b is possible.

A light source 20 is present in the area of the reaction module 17 to form the particles 28 by means of polymerization.

FIG. 7 shows a schematic illustration of a microfluidic reactor according to a second embodiment. The fluid B is located in the center of the focusing module 1 or the droplet formation channel 5, surrounded by the fluid A. Offset in the direction of flow 2, the peripheral wall 12 of the focusing module 1 is provided with inlet openings 13, which successively supply the fluid A into the focusing module 1 allow. Different from the first embodiment the opening width 11 of the focusing module 1 is identical to the opening width 10 of the droplet formation channel 5. The flow cross-section 25 of the fluid B is reduced without a geometric change in the microfluidic reactor solely from the supply of the fluid A.

FIG. 8 shows a preferred embodiment of the reactor according to FIG. 7, in which a partial flow reversal 37 of the fluid A takes place in the transition area 38 from the focusing module 1 to the drop formation channel 5, part of the fluid A in the return flow channel 15 separated by separating structures 14 flows back and flows again through the inlet openings 13 into the focusing module 1. With the help of this design, the required amount of fluid A can be minimized.

Figure 9 illustrates the second embodiment of the microfluidic reactor in which in the flow direction 2, an ^'access 35 is formed for the addition of a control fluid X both sides behind the inlet ports 13 of the fluid A in the peripheral wall 12 of the focusing module. 1 The control fluid X enables the position of the formation of the drops 26 in the drop formation channel 5 to be influenced.

LIST OF REFERENCE NUMBERS

A First fluid

B Second fluid

C Third fluid

X control fluid

1 focusing module

2 flow direction

3 inlet funnels

4 opening small end inlet funnel

5 drop formation channel

6 distribution module

7 outlet channel fluid A

8 outlet channel fluid B

9 Opening width of outlet channel Fluid B

10 opening width drop formation channel

11 Focus module opening width

12 peripheral wall focusing module

13 inlet openings for fluid A

14 separation structures

15 reverse flow channel

16 Flow cross section fluid B, first embodiment

17 reaction module

18 Inlet opening reaction module 9 heat source 0 light source 1 magnetic coil 2 laser 3a cathode 3b anode 4 magnetic field Flow cross-section, fluid B, second embodiment drop cross-section reduction particles vortex zone or dead water zone funnel wall circumferential end, funnel wall circumferential wall, reaction module core-shell access, control fluid X field lines, electric field flow reversal transition area, focusing module / drop formation channel

Claims

claims

1. A method for producing monodisperse nanodroplets, in which an immiscible second fluid B is introduced into a continuously flowing first fluid A, in which the fluid B is surrounded by the fluid A and in which the flow cross section (16, 25) of the fluid B in Flow direction (2) is tapered in such a way that the fluid B breaks down into individual drops (26) due to its hydrodynamic instability.

2. The method according to claim 1, wherein the fluids A, B in a focusing module (1) accelerated by a geometric cross-sectional reduction (27) and a drop formation channel (5) with a constant opening width (10) are supplied. (Fig. L)

3. The method according to claim 1, in which a fluid A is supplied in a focusing module (1) to a fluid stream B via inlet openings (13) distributed in the flow direction (2). (Fig.7)

4. The method according to claim 3, wherein the fluid A is returned after flowing through the focusing module (1) in a return flow channel (15) against the flow direction. (Fig.8)

5. The method according to any one of claims 1-4, in which a control fluid X is introduced into the fluid A via an access (35). (Fig.9)

6. The method according to any one of claims 2 to 5, wherein the fluids A, B via a distributor module (6) are fed to the focusing module (1).

7. The method according to claim 6, in which from the distributor module (6) a plurality of parallel spaced fluid streams B are emitted into the focusing module. (Fig. 2, 3, 4)

8. The method according to any one of claims 1-7, in which a force is exerted on electrically conductive fluids A, B by means of a magnet coil (21) or a solid-state magnet. (Fig.3)

9. The method according to any one of claims 1-8, wherein the fluids A, B are irradiated with a laser (22).

10. The method according to any one of claims 2-9, wherein a third fluid C is added to the focusing module (1), wherein the fluid B is chosen hydrodynamically unstable than the fluid C. (Fig.5)

11. The method according to any one of claims 1-10, in which an electrical voltage is impressed in fluid A, B, at least one fluid A, B having electrolytic properties (FIG. 6)

12. A method for producing nanoparticles from nanoprops according to the method of claims 1-11, in which the drops (26) are converted into particles (28) in a reaction module (17).

13. The method according to claim 12, wherein the particles (28) in the reaction module (17) are generated by polymerization.

14. The method according to claim 13, in which a solution of monomers is used as fluid B.

15. The method according to claim 13, wherein the polymerization is induced by adding initiators.

16. The method according to any one of claims 12-15, wherein the polymerization is induced by the introduction of heat.

17. The method according to any one of claims 12-16, wherein the polymerization is induced by introducing light.

18. A microfluidic reactor for performing the method according to any one of claims 1-17, in which a second fluid stream of a fluid B is introduced in a first continuous fluid stream of a fluid A, the fluid B being surrounded by fluid A and the fluids A, B are immiscible and in which a focusing module (1) with an inlet funnel (3) tapering in the direction of flow (2) is formed, to which a drop formation channel (5) is connected at its small opening (4). (Fig. L)

19. Microfluidic reactor according to claim 18, wherein a distributor module (6) for supplying the fluids A, B in the focusing module (1) with a plurality of outlet channels (7) of the fluid A and outlet channels (8) of the fluid B are formed is.

20. Microfluidic reactor according to claim 19, wherein the outlet channels (8) of the fluid B have an opening width (9) of 100 nm - 500 microns.

21. A microfluidic reactor according to claim 20, wherein the outlet channels (8) of the fluid B have an opening width (9) of 1 micron to 100 microns.

22. Microfluidic reactor according to one of claims 18-21, wherein the drop formation channel (5) has the opening width (10) of the small opening end (4) of the inlet funnel (3).

23. Microfuidic reactor according to one of claims 18-22, in which in the area of the drop formation channel (5) accesses (35) are formed for feeding a third control fluid X miscible with fluid A.

24. A microfluidic reactor for carrying out the method according to one of claims 1-17, in which a second fluid stream of a fluid B is introduced in a first continuous fluid stream of a fluid A, the fluid B being completely surrounded by the fluid A and the fluids A , B are immiscible and flow in a focusing module (1) with a substantially constant opening width (11), in which in at least one peripheral wall (12) of the focusing module (1) in the flow direction (2) offset inlet openings (13) for supplying the Fluids A are arranged, and in which a drop formation channel (5) is connected to the focusing module (1).

25. The microfluidic reactor according to claim 24, wherein the focusing module (1) has separating structures (14) for delimiting a return flow channel (15). (Fig.8)

26. Microfluidic reactor according to claim 24 or 25, in which in the peripheral wall (12) accesses (35) are formed to feed a third control fluid X miscible with fluid A. (Fig.9)

27. Microfluidic reactor according to one of claims 18-26 in which a reaction module (17) is connected to the drop formation channel (5) in the flow direction (2).

28. The microfluidic reactor according to claim 27, wherein the reaction module (17) has at least one inlet opening (18).

29. The microfluidic reactor of claim 27, wherein the reaction module (17) comprises a heat source (19).

30. The microfluidic reactor of claim 27, wherein the reaction module (17) comprises a light source (20).

31. Microfluidic reactor according to one of claims 18 - 30, in which a magnet coil (21) is arranged on the focusing module (1).

32. Microfluidic reactor according to one of claims 18-30, in which a solid-state magnet is arranged on the focusing module (1).

33. Microfluidic reactor according to one of claims 18-32, in which a laser (22) is arranged on the drop formation channel (5).

34. Microfluidic reactor according to one of claims 19 - 33, in which an electrode (23a, 23b) is attached to each of the distributor module (6) and the reaction module (17).