DE102007051977A1 - Process for the preparation of electrically and / or magnetically controllable membranes and magnetic actuator with such a membrane - Google Patents

Abstract

The present invention relates to a method for producing electrically and / or magnetically controllable membranes, in particular for switches or pumps. In the method, micro- and / or nanoparticles having magnetic and / or electrical properties are mixed with a flowable state matrix material which has elastic properties after solidification. The matrix material is applied as a layer to a substrate and a distribution of the particles in the layer with one or more electric and / or magnetic fields selectively changed in order to obtain an accumulation of the particles at one or more points of the layer. The layer is then solidified with the aggregated particles to form one or more membranes. The invention also relates to a magnetic actuator with such a membrane. The method allows the use of elastic membranes with embedded magnetic or magnetizable particles, without affecting the elastic properties in certain areas of the membrane negative.

Description

Technical application

The The present invention relates to a process for the preparation of electrically and / or magnetically controllable membranes, in which Micro and / or nanoparticles with magnetic and / or electrical Properties by which they are in a magnetic or electrical Field experience a force effect, embedded in a matrix material from which the membrane is subsequently formed. The invention also relates to a magnetic actuator based on a such membrane. Such membranes or magnetic actuators can be used, for example, for magnetic switches, valves or use pumps.

State of the art

The addition of micro- and / or nanoparticles to a matrix material for the targeted influencing of material properties is a common method in the production of materials. This results in materials - so-called micro- and / or nanocomposites - that can exhibit novel, advantageous properties. Films of such materials usually have largely homogeneous properties due to the uniform distribution of the micro- and / or nanoparticles. For many applications, however, these admixtures bring not only advantages but also disadvantages which require a compromise of new desired properties and unfavorable properties. For example, increasing the dielectric constant of polymers by embedding TiO ₂ particles can also cause an undesirable increase in the elastic modulus.

Especially in the production of elastic membranes, the embedding of, for example, magnetic micro- and / or nanoparticles can lead to a stiffening of the membrane, which is not sustainable for the intended application. For example, Kai et al. "A Robust Low-Cost PDMS Peristaltic Micropump With Magnetic Drive", Solid State Sensor, Actuator and Microsystems Workshop, June 6-10, 2004, pages 270-273 , a peristaltic micropump with a magnetically controllable membrane made of PDMS (polydimethylsiloxane). In the membrane small chambers are provided for receiving magnets, which are made of a magnetic powder in a thermoplastic matrix material. In this way, a deterioration of the elastic properties of the membrane is avoided. The placement of the magnets in the membrane, however, makes the manufacturing process consuming.

The The object of the present invention is a method for the production of electrically and / or magnetically controllable Specify membranes that perform with less effort and the manufacture of diaphragms for pumps, valves and Switch allows.

Presentation of the invention

The Task is with the method according to claim 1 solved. Claim 10 is a magnetic actuator An, which is produced with an inventive Membrane is operated. Advantageous embodiments of the method as well as the actuator are the subject of the dependent claims or leave The following description and the embodiments remove.

at the proposed method will be micro- and / or nanoparticles provided with magnetic and / or electrical properties, by they exert a force in a magnetic or electric field Experienced. The micro- and / or nanoparticles are mixed with one in a flowable one Conditional matrix material mixed after solidification has elastic properties. The resulting dispersion from Matrix material and micro- and / or nanoparticles is used as a layer applied to a substrate. This can be done, for example, by spin-coating, Scrape, pour or spray done. The layer becomes then one or more electrical and / or exposed to magnetic fields through which the mixing approximately even distribution of Micro- and / or nanoparticles in the layer deliberately changed is an accumulation of micro and / or nanoparticles at one or more locations of the layer. Subsequently the layer with the corresponding accumulated micro- and / or nanoparticles to form one or more membranes solidified. The solidified layer, which is both a single and may also comprise a plurality of interconnected membranes may subsequently detached from the substrate and the corresponding Use be supplied. So the detached one Layer, for example, bonded to a silicon substrate, in which corresponding recesses were generated, about where the one or more membranes are attached. Especially Advantageously, the method can be used with membranes of arrays of Create clusters, hereinafter also as a membrane array designated subsequently to a substrate with accordingly arrayed recesses are applied.

In the present patent application, the term microparticles is to be understood as meaning particles in the size range between 1 and 1000 μm, nanoparticles being particles in the size range below 1 μm. The procedure is self-evident It is not certain that particles larger than 1 mm in size are also present under the micro- and / or nanoparticles. This is not desirable. The micro- and / or nanoparticles may consist of para-, ferro- or permanent magnetic materials, for example.

in principle can use the process membranes or membrane arrays in Any dimensions are produced. Particularly advantageous The process for the production of micro-membranes or micromembrane arrays, for example for microvalves, Micropumps or microswitch applications.

The proposed method uses the mobility of micro and / or Nanoparticles in a still fluid state matrix material around these magnetic and / or selectively accumulate electric fields locally, to align and by solidification of the matrix material in this fix specifically generated distribution. This assumes that the matrix material in the targeted influencing the micro and / or Nanoparticles is present in a flowable state. This can be a liquid or even a act highly viscous state. If necessary, the matrix material temporarily transferred to this state. This For example, depending on the material, by loosening or Melting done or can also, for example, in the case of polymers be achieved as a matrix material in that the matrix material still in at least partially uncrosslinked and therefore flowable Condition exists. After application of the matrix material with the contained therein micro- and / or nanoparticles on the substrate the layer then becomes a static and / or variable magnetic field and / or electrical field exposed by a force effect exerted on the micro and / or nanoparticles in the layer becomes. The fields are chosen so that a targeted Accumulation of micro- and / or nanoparticles in the layer takes place. The choice of fields used, d. H. electrical or magnetic Field or both depends on the characteristics of the chosen one Micro and / or nanoparticles from. The layer can be used for improvement the surface quality of the membranes also in addition be provided with a corresponding cover, of course the action of the electric and / or magnetic fields the layer must allow.

The field-creating organization must be able to provide a timely and / or to create a location-variable field, in this way the particles accumulate and align in the desired manner. Especially movable arrangements of permanent magnets, arrangements electrical coils and arrangements of electrically conductive Sheets and layers can be used here. Furthermore, the superposition of static and dynamic fields possible to spatially resolved Minima or maxima of the field strength over the lateral extent to create the layer.

The final fixation of the particles and their orientation then takes place by the solidification of the matrix material. This can For example, in plastics by cooling, evaporation the solvent or a crosslinking reaction induced by Heat, radiation and / or a cross-linking chemical component, respectively. During this process, the layer may continue remain exposed to the magnetic or electric field.

By the targeted influencing of the distribution of micro- and / or nanoparticles In the membrane membrane areas can be used for the elastic function of the membrane in the corresponding application are largely free of the stored microorganisms. and / or nanoparticles, so that in these areas no unwanted stiffening of the membrane occurs. So For example, the micro- and / or nanoparticles in the central area of the membrane are piled so that the margins, if any, only a low concentration have these particles. Furthermore, the allows with the process producible local accumulation of the particles an increased permeability of the membrane for electric fields, since the membrane in this case does not form a shield, as with a uniform distribution electric conductive particle would be the case. Such a thing produced membrane is therefore advantageous for the already mentioned applications in valves, pumps or electrical switching elements. The membrane can be easy to manufacture, since no attachment of additional Components such as magnets are required. Especially advantageous the method is suitable for the production of membrane arrays, because the accumulation of micro and / or nanoparticles for the entire array with an appropriately trained device is executable in one step.

In a particularly advantageous embodiment, the micro- and / or nanoparticles are magnetic or magnetizable particles. In the case of magnetizable particles, these are preferably magnetized after solidification of the layer with the same device with which the accumulation of the particles was controlled in the layer. Examples of magnetic particles are particles of AlNiCo, barium ferrite, cobalt, CoPt ₃ , CrO ₂ , CuNiFe and CuNiCo alloys, Fe, Fe ₂ O ₃ , Fe ₃ O ₄ , FeCoCr alloys, NdFeB alloys, Ni, NiCuCo, NiFe , Strontium ferrite, SmCo, MnAs, EuO, iron oxide-containing pigments. Examples of matrix materials are silicones or thermoplastic elastomers based on olefins, polyurethanes, styrenes and polyamides.

With Such a membrane can be a magnetic actuator realize the preferably elastic membrane with the therein accumulated micro- and / or nanoparticles and a device for Contactless deflection of the membrane, which has a generated on the membrane acting magnetic field.

One Such magnetic actuator can be, for example use in switching elements as a magnetic switch. That is how it is In mobile communication technology there is an increasing demand for reconfigurable Antennas, for example, by interconnecting smaller Single antenna elements to so-called patch antennas a variety Geometries can be realized. This is a larger one Number of separately controllable switches necessary. The cost of such smart antennas should be however, not significantly exceed those currently used. Out This reason is a technology for mass production of reconfigurable Antennas including the switches necessary that are low cost. This can with a manufactured according to the present method Elastomer membrane with locally distributed magnetic properties or with an array of such membranes. In order to can switching arrays with a variety of matrix-like, magnetic realize actuatable switches.

In In this context, the location of the magnetic particles in the membrane a big advantage, since this accumulation leads to a low electrical conductivity of the membrane. Would be a homogeneous with magnetic, electrically conductive Particles loaded elastomeric membrane in such an application used in high frequency and mobile technology, this would act as a shield and thus the radiation behavior of the antennas significantly influence. But these are just local clusters the particles in the membrane will be significantly less to none emitted radiation absorbed in the actuator material.

One Another very advantageous application of the method produced membranes or the listed magnetic Aktors exists in the field of pumps and valves. Here offers also the accumulation of magnetic particles in one or several areas of the membrane considerable advantages. By the Localization of the particles in the membrane will be mostly negative occurring stiffening of the membrane by the embedded particles also restricted to these subareas. The membrane This can be compared to a membrane with homogeneously distributed Particles same load density deflected much stronger become. The deflection takes place in a known manner an external magnetic field through which the magnetic areas of the Membrane excited to movements or for local warming can be.

On The field of bioanalytics is becoming increasingly manipulated needed for the smallest amounts of liquid, which are usually formed in silicon technology. For However, many applications require a more cost-effective alternative. Micropumps and microvalves based on easy-to-process Plastics, such as thermoplastics, thermosets, elastomers or silicones, are suitable for this. With the proposed method to produce an elastic membrane with embedded localized Magnetic particles can be inexpensive arrangements magnetically actuated micropumps and microvalves can be realized. These actuators consist of at least one elastic membrane with the localized magnetic particles. Furthermore, at least a field-generating device, such as coils or permanent magnets, an essential part of the actor. Pumps or valves continue to point at least one chamber with incoming or outgoing channels on. Typical dimensions of the cross sections of the chambers and channels are preferably less than 3 mm. The aktorische effect is through a change in the magnetic field acting on the membrane realized. Depending on the type of embedded particles results in a attractive or repulsive force that a shape and / or Movement of the membrane has the consequence. For pumps follows from this a volume displacement or extension in the Chamber, what a movement of the medium to be conveyed to Episode has. If the actuator is a valve, it is generated the shape or location change of the membrane an expansion or narrowing up to the positive fit of a channel diameter with resulting change in the fluidic resistance.

Brief description of the drawings

The Proposed methods and the proposed actuator are hereafter based on embodiments in conjunction with the drawings briefly explained again. Hereby show:

1 an example of the accumulation of micro- and / or nanoparticles in a layer;

2 schematically an example of the orientation of the micro and / or nanoparticles in the layer;

3 an example of a device for targeted accumulation of micro- and / or nanoparticles at specific locations of a layer;

4 another example of a device for the targeted accumulation of micro- and / or nanoparticles in a layer;

5 an example of one with the institution of 3 machined layer in which the micro- and nanoparticles are accumulated in different places in the form of an array;

6 schematically an example of a use of the membrane as a pumping element; and

7 schematically an example of a use of the membrane as a switching element.

Ways to carry out the invention

1 shows very schematically the process performed in the proposed method accumulation of micro- and / or nanoparticles in a layer by magnetic and / or electric fields. In the left-hand part of the figure, this is a layer mixed homogeneously with micro- and / or nanoparticles 1 shown. Such a layer can be achieved by mixing the micro- and / or nanoparticles with the matrix material before it is applied to a corresponding substrate as a layer. Before the solidification of the matrix material, the distribution of the micro- and / or nanoparticles in the layer can then be selectively changed by the action of electrical and / or magnetic fields. For this purpose, the micro- and / or nanoparticles must of course be chosen so that they experience a force under the influence of the electrical and / or magnetic fields used. In the right part of the 1 For this purpose, an accumulation of the microparticles and / or nanoparticles by the specific influence of electrical and / or magnetic fields in the layer can be recognized purely by way of example. In this case, by suitable use of the fields, almost any desired geometry of the clusters can be generated, such as, for example, stripe-shaped clusters 2 or circular clusters 3 the micro and / or nanoparticles. In these pilings 2 . 3 then there is a higher particle concentration than in the original layer 1 , On the other hand sinks in the spaces between the clusters 2 . 3 the particle density, so that there is a significantly lower particle density or almost no particles. This is through the areas 4 low particle density in the 1 too indicated.

In addition to the accumulation of the particles in asymmetric micro- and / or nanoparticles, in particular magnetic particles, also an orientation of the particles in the layer through the field. Such an orientation of the particles 5 is schematic in 2 indicated.

3 shows as an example a device for the targeted accumulation of magnetic or magnetizable micro- and / or nanoparticles. The device consists of two opposing or can be brought into this position forming units 6 , which are realized in this example as plates with pin-shaped elements formed thereon. The pin-shaped elements are arrayed in opposite directions, in the present example as a 5 × 5 array, and consist of a ferroelectric material such as iron. With these shaping units 6 becomes an open magnetic circuit 7 formed, the at least one electric coil 8th for generating a magnetic field. The substrate 9 with the layer thereon (not visible in the figure) is in the air gap between the two shaping units 6 positioned. By generating a magnetic field across the electrical coil 8th The layer on the substrate is also exposed to a magnetic field, its distribution through the topography of the forming devices 6 is fixed. This topography generates local concentrations of the magnetic field lines in the exposed material which lead to an accumulation of the micro- and / or nanoparticles corresponding to this topography in the layer. About the electric coil 8th a static and / or a time-varying magnetic field can be built up in the material. In addition, the substrate can also be 9 be moved relative to the magnetic field. This can also be done in time with the variable change of the external magnetic field. In this way, different accumulations can be generated in the layer. Furthermore, in this arrangement, a temperature, for example, a heating, of the material to be treated by the magnetic circuit in the 3 Tempering device not shown receives. Furthermore, the magnetic field form in the device of 3 after solidification of the matrix material of the layer also be used to magnetize the particles in the matrix material. For this purpose, the particles are exposed to a strong magnetic field through the device.

4 shows another example of a device for local accumulation of micro and / or nanoparticles in the layer. The device consists of two carrier layers 10 . 11 , in each of which electrical flat coils 12 are formed. The coils are realized in Helmholtz arrangement, as shown in the 4 is recognizable. In the space between the two carrier layers 10 . 11 In turn, the substrate may be positioned with the layer applied thereon. The individual coils 12 are provided with individual connections, so that by targeted control of these coils targeted Anhäu tions of the particles in the layer can be achieved. Through the flat coils 12 Directed magnetic fields are generated which collect the magnetic particles in the material in the area of the field maxima.

Farther For example, such a device can be included combine a device for generating a static magnetic field, to achieve an overlay of the fields. this makes possible the targeted transport of magnetic nanoparticles and / or microparticles the entire area of the layer.

5 shows an example of a layer 13 on a substrate with local clusters of micro- and / or nanoparticles, as used for example in the device of 3 can be generated when using a static magnetic field. Like from the 5 in plan view of the layer 13 can be seen, this contains an array-like arrangement of accumulated with the particles areas 14 , each of an area 15 are surrounded with a significantly reduced particle density. The particles of the clusters 14 were due to the magnetic field from the areas 15 deducted. In the remaining area of the layer 13 , which was not subjected to the magnetic field, the particles are still in the original uniform distribution. Such a layer is suitable after solidification as a membrane array, for example for a switch or pump array.

to Preparation of such a layer is an example 2-component silicone (PDMS) according to manufacturer's instructions. The micro- and / or nanoparticles are then called Underlaid fillers, the degree of filling dependent of the type, size and structure of the particles. For example, in the case of anisotropic strontium ferrite particles good results with a concentration of about 35% by volume in the matrix material reached. In the case of NdFeB as micro and / or nanoparticles suitable a proportion of about 50% by volume in the matrix material. After the subsets The fillers become the dispersion of fillers and degas matrix material in the desiccator for about 20 minutes.

Subsequently, a thin layer of about 50 to 100 .mu.m of this dispersion, which contains the still uncrosslinked PDMS and the fillers, spin coated on a carrier substrate. In the present example, this is a 100 mm wafer TOPAS ^®. The wafer is then brought into the localization device, ie for example between the two molding units 6 the institution of 3 , Subsequently, the localization of the micro- and / or nanoparticles by turning on the corresponding magnetic field. After this localization, the PDMS is crosslinked by leaving it at room temperature for about 48 hours or at 120 ° C for about 15 minutes. The solidified layer then produced has the corresponding clusters of micro- and / or nanoparticles fixed in the layer.

Such a membrane or such a membrane array can be used very advantageously in the manufacture of pumps. 6 shows a highly schematic example in which the membrane 16 with the area 14 Accumulated nanoparticles on a silicon substrate 17 is bonded, so that the accumulated area 14 over a recess 18 lies in the silicon substrate. This recess 18 represents a pumping chamber, which is connected to not shown in the figure inflows and outflows for a fluid. Above the membrane layer 16 becomes another substrate 19 arranged, via corresponding spacers (not shown) with the silicon substrate 17 is connected. In this further substrate 19 is an electromagnet 20 directly above the area 14 positioned with accumulated particles. By temporally variable operation of the electromagnet 20 can thus be a deflection of the membrane layer 16 over the recess 18 reach, which leads to a pumping action with suitable control.

In the same way can also be realized switching elements with such a membrane, as this is highly schematic and exemplified by an open or closed single switch in the 7 is indicated. In this case, under the membrane 16 at least two contact increases 21 arranged, which in the closed state with a contact surface 22 at the bottom of the membrane 16 stay in contact. The contact increases 21 are designed such that they bias the membrane, so that the membrane in the idle state, ie without external magnetic or electrical forces, always presses with a contact force on the contact increases. In this closed state, the switching contact (s) is / are realized. By connecting the electromagnet with hard or soft magnetic core 20 can the membrane 16 and thus the contact 22 from the contact increase 21 lifted and deflected upward, and thus transferred to the open state. This condition is due to the force acting between the electromagnet 20 and the membrane 16 also currentless stable as the previously described closed state. In this way, a bistable switch can be realized. Corresponding conductor tracks 23 in the substrate 17 are indicated in the figure. It can also strip conductors, for example by screen printing or sputtering, on the solidified membrane 16 be applied.

1

layer with homogeneous particle distribution

2

strip accumulation

3

round accumulation

4

areas low particle density

5

micro- and / or nanoparticles

6

shaping unit

7

magnetic circuit

8th

Kitchen sink

9

substratum with layer

10

upper carrier

11

lower carrier

12

flat coil

13

Area with homogeneous distribution

14

Area with particle accumulation

15

Area with low particle concentration

16

membrane layer

17

silicon substrate

18

recess

19

additional substratum

20

electromagnet with hard or soft magnetic core

21

Contact increases

22

contact area

23

conductor tracks

QUOTES INCLUDE IN THE DESCRIPTION

This list The documents listed by the applicant have been automated generated and is solely for better information recorded by the reader. The list is not part of the German Patent or utility model application. The DPMA takes over no liability for any errors or omissions.

Cited non-patent literature

• "A Robust Low-Cost PDMS Peristaltic Micropump With Magnetic Drive", Solid State Sensor, Actuator and Microsystems Workshop, June 6-10, 2004, pp. 270-273 [0003]

Claims (18)

Process for the production of electrical and / or magnetically controllable membranes, in particular for valves, Switch or pump in which - Micro and / or nanoparticles provided with magnetic and / or electrical properties, by putting them in a magnetic or electric field Experiencing force, - the micro and / or nanoparticles with a fluid state Matrix material are mixed, which is elastic after solidification Has properties, - The matrix material as a layer is applied to a substrate, - a distribution the micro- and / or nanoparticles in the layer with one or more electrical and / or magnetic fields is changed specifically, an accumulation of micro- and / or nanoparticles on one or to obtain multiple digits of the layer, and - the Layer with the accumulated at one or more places Micro and / or nanoparticles for forming one or more membranes is solidified. Method according to claim 1, characterized in that in that a polymer is used as matrix material for mixing with the micro- and / or nanoparticles in uncrosslinked or only partially crosslinked Condition provided and to strengthen the layer stronger is networked. Method according to claim 1, characterized in that in that a polymer is used as matrix material for mixing with the micro- and / or nanoparticles in dissolved or partially solved state is provided. Method according to claim 1, characterized in that in that a polymer is used as matrix material for mixing with the micro- and / or nanoparticles in molten or softened Condition is provided. Method according to one of claims 2 to 4, characterized in that the matrix material is an elastomer or a silicone is used. Method according to one of claims 1 to 5, characterized in that micro and / or nanoparticles para-, ferro- or permanent magnetic materials used become. Method according to one of claims 1 to 5, characterized in that micro and / or nanoparticles magnetizable materials are used and the micro- and / or Nanoparticles after solidification of the layer over Magnetic field to be magnetized. Method according to one of claims 1 to 7, characterized in that by the one or more electrical and / or magnetic fields locally different field strengths be generated in the layer. Method according to one of claims 1 to 8, characterized in that the one or more electrical and / or magnetic fields generated by a device, in which the substrate with the applied layer between an upper and a lower unit for generating the one or more electrical and / or magnetic fields are positioned and / or moved. Method according to claim 9, characterized in that that the upper and / or lower unit moves relative to the substrate become. Method according to one of claims 1 to 10, characterized in that the distribution of micro and / or Nanoparticles in the production of several on the substrate side by side lying membranes with the one or more electrical and / or magnetic fields is influenced so that in each the membranes in one or more places an accumulation the micro- and / or nanoparticles in the layer is obtained. Method according to one of claims 1 to 11, characterized in that the distribution of micro and / or Nanoparticles are influenced so that an accumulation of Micro- and / or nanoparticles in the center of the membrane is obtained. Magnetic actuator with a membrane, in which micro- and / or nanoparticles are embedded, which experience a force effect in a magnetic field, and a device ( 20 ) for non-contact deflection of the membrane ( 16 ), which are used to produce a membrane ( 16 ) magnetic field is formed, wherein the micro- and / or nanoparticles at one or more locations ( 14 ) of the membrane ( 16 ) are accumulated according to a method according to one or more of the preceding claims. Magnetic actuator according to Claim 13, in which the membrane ( 16 ) on at least one side of an electrical contact surface ( 22 ), which by deflection of the membrane ( 16 ) with one or more of the membrane ( 16 ) opposite electrical contact surfaces ( 21 ) Can be brought into contact or solvable from these. Magnetic actuator according to Claim 13, in which the membrane ( 16 ) on one side a volume ( 18 ) with at least one inlet and one outlet limited. Use of the magnetic actuator according to claim 14 in an electrical switching element. Use of the magnetic actuator according to claim 14 in micro switch arrays in radio frequency or mobile radio technology. Use of the magnetic actuator according to claim 15 in a pump.