WO2004030210A1 - Actuator comprising nanotubes, especially carbon nanotubes, layers of carbon nanotubes, and the production and use of the same - Google Patents

Abstract

The invention relates to an electromechanical actuator comprising at least one layer provided with nanotubes having an average predominant direction in the layer and over the nanotube arrangement. The invention also relates to electrolytes for actuators, actuators having a multilayer arrangement, geometric arrangements of the nanotube layers, actuators having an improved control capacity, special kinematics, shear force decoupling, relaxation electrodes, and means for increasing the ion speed. The invention also relates to methods for producing and using said actuators.

Description

Applicant: Fraunhofer Society for the Promotion of Applied Research e.V., Leonrodstraße 54, 80636 Munich

Actuator with nanotubes, in particular carbon nanotubes,

Layers of carbon nanotubes and theirs

Production and application

The present invention relates to actuators based on nanotubes, in particular micromechanical actuators made of carbon nanotubes, layers made of nanotubes (bucky paper), their manufacture and use.

In recent years, research has been carried out on a series of actuators or microactuators, ie the smallest systems for converting electrical into mechanical energy ("artificial muscles"), which are based on new materials such as ceramic systems, piezoelectric polymers.

ren, electrostrictive polymers, polyelectrolytic polymers, conductive polymers and nanotubes.

Actuators generally comprise at least two electrodes and at least one layer which changes their expansion in at least one dimension due to the influence of electrical energy.

From the article by Baughman et al. in Science 1340 (1999) it is known that single-wall nanotubes (SWNT) change their length and their diameter when an electrical voltage is applied. Single-wall nanotubes are perfect carbon tubes with a diameter of a few nanometers and a length in the micro to millimeter range. The changes in length and diameter of the nanotubes are based on the change in the length of the carbon-carbon bond as a function of the amount of charge injected as a result of quantum mechanical processes.

Ideally, a change in length of approx. 1% can be achieved with nanotubes by applying a voltage.

Carbon nanotubes are characterized by excellent mechanical and thermal properties. In contrast to polymer actuators, which show no actuation even at temperatures of 70 ° C, they are stable up to 750 ° C or even up to 2,800 ° C in a vacuum. It is also assumed that they are biocompatible, which enables their use in medical technology. In addition, far greater forces can be generated with carbon nanotubes than is the case with the previously known polymer and piezo actuators. In principle, carbon nanotubes can also be operated with a very low supply voltage of 1 volt, whereas supply voltages of 70-300 V are required for polymer actuators and supply voltages of up to 1000 V are required for piezo actuators. Furthermore, the carbon nanotubes show no overshoot behavior.

54341b.doc Various working groups have worked to achieve the greatest possible actuator effects. In this context, attempts have been made to store large amounts of charges in the electrochemical double layer on the carbon nanotubes by producing layers of carbon nanotubes (bucky paper), immersing them in an electrolyte and applying an electrochemical potential.

Baughman et al. describe in Science 1340 (1999) investigations of electromechanical actuators made of carbon nanotube papers, which were carried out in 1 m NaCl as an electrolyte. This article also reports on the determination of the gravimetric capacity in the electrolytes 38% H ₂ SO ₄ and LϊCI0 ₄ in acetonitrile or propylene carbonate. Activity measurements of nanotube papers in 1 m NaCI are also presented in the article "Electro-mechanical behavior of carbon nanotube sheets in electrochemical actuators" in "Smart Structures and Materials" 25 (2000) by Mazzoldi et al.

To produce the previously known bucky paper, a suspension of nanotubes on a PTFE filter is subjected to vacuum filtration and then the dried nanotube paper (bucky paper) is removed from the filter. Bucky papers with a statistical arrangement of the nanotubes are obtained by this method.

The change in the longitudinal and transverse axes, which is achieved in the previously known bucky papers, is far below the ideally observed length and transverse changes of approx. 1% for individual nanotubes. With increasing layer thickness of a bucky paper, the change in the longitudinal and transverse axes continues to decrease and the actuation speed continues to decrease.

The previously known nanotube actuators have an insufficient actuation amplitude, i.e. too little change in the longitudinal and transverse axis of the nanotubes in the bucky paper and too little force. So far, developments in the field of bucky paper and nanotubes have essentially been limited to basic research.

54341b doc For the reasons mentioned above, no industrially applicable nanotube actuator is currently available.

The object of the present invention is to provide actuators with better actuation characteristics, in particular larger actuation sample situations and higher actuation speeds, and to specify methods of their production and use.

This object is achieved by the features of claims 1, 5, 11, 16 to 25.

In the context of the present invention, it was found that an improvement in the actuation characteristics of nanotube actuators, in particular of carbon nanotube actuators, can be achieved if the nanotubes distributed in the layer of nanotubes (hereinafter referred to as “bucky paper”) are not statistically The invention therefore provides for the nanotubes to be arranged essentially at least partially in a preferred direction in the paper plane with respect to their longitudinal axis in relation to the preferred direction of the nanotubes in the be oriented essentially at an angle of less than 90 °, preferably less than 60 ° and particularly preferably 'less than 45 °, up to the parallel arrangement.

With this arrangement, the destructive actuation behavior known in the statistical arrangement can be reduced and the actuation amplitude increased.

It can be seen that the mechanical properties of bucky paper with highly aligned nanotubes decrease compared to bucky paper with statistically distributed nanotubes, so that, for example, the elastic properties deteriorate. The use of additives such as compounds that increase adhesion or flexibly embedding the aligned nanotubes without affecting their expansion are then preferred.

Carbon nanotubes, in particular single-wall nanotubes made of carbon, are preferably used in the context of the present invention. In principle, however, it is also possible to use multi-wall carbon nanotubes or even nanotubes made of other elements or compounds such as boron nitride (BN), metal sulfides (MoS ₂ , WS ₂ ) or metal oxides (eg V ₂ O ₅ ) use. In principle, all tube-shaped materials can be used that show mechanical deflection when electrical quantities, such as voltage or current, are applied.

As far as the term "bucky papers" is used below, it includes not only layers made of carbon nanotubes, but also layers made of other nanotubes.

A further improvement in the actuation behavior of actuators made of carbon nanotubes can be achieved if the bucky paper is largely free of impurities such as fullerenes, graphite particles and catalyst additives, since these impurities contribute to poor actuation behavior. The impurities can be removed by hydrothermal oxidative processes and subsequent treatment in acids. The purity of the nanotube paper should be at least 60%, preferably at least 80%.

The alignment of the nanotubes in the bucky paper can take place during the manufacture of the bucky paper by aligning the nanotubes using physical or chemical methods. For example, the nanotubes can be aligned in a surfactant suspension by an electrical, magnetic and / or electromagnetic field and / or under the influence of ultrasound. Sedimentation carried out under these conditions or transfer to a suitable substrate, based on the Langmuir-Blodgett technique, enables a higher degree of alignment.

54341b.doc The alignment of the nanotubes can also be carried out by rotation methods, in which the nanotubes in a suspension are aligned by rotation essentially along their longitudinal axis and the aligned nanotube layer is then skimmed off or transferred to a carrier and dried.

In the context of the present invention, it was also found that the actuation amplitude and the actuation speed can be increased by suitable selection of the electrolytes.

An increase in the actuation amplitude can be achieved by using electrolytes with large ions and / or a high charge number. Electrolytes with large anions are preferably used if the bucky papers are connected to the positive pole and electrolytes with large cations if the bucky papers are connected to the negative pole.

However, the type of electrolyte also has an influence on the actuation speed. By using fast ioneri, i.e. highly charged, smaller ions, the actuation speed can be increased.

Since a large actuation amplitude can be achieved with large ions, but the actuation speed is reduced and vice versa, it is important to select suitable electrolytes in which good values are achieved both for the actuation amplitude and for the actuation speed.

In principle, the electrolytes from the group of the alkali and alkaline earth salts, but also aluminum salts or metal salts of the halides, nitrates, sulfates, phosphates, hydrogen phosphates, dihydrogen phosphates, halogenates and perhalates, hydroxides, acetates, oxalates or - to the extent that they are stable - theirs Acids selected such as LiCl, NaCI, KCI or the corresponding fluorides, NaNO _{3 /} Na ₂ S0 ₄ , Na ₃ P0 ₄ , NaCIO ₃ , NaCIO ₄ or the corresponding lithium or potassium salts or alkaline earth salts.

Electrolyte mixtures can also be used for optimization.

Water or another polar solvent which enables the dissociation of the ions is suitable as the solvent for the electrolytes. Gel-like, highly viscous electrolytes, such as polyelectrolytes, ionomers or hydrogels swollen with electrolyte, can also be used to adjust the viscosity, for example.

The concentration of the electrolyte in the solvent is preferably between 0.1 and 5 mol / l, particularly preferably 0.2 to 2 mol / l.

If Na ₂ SO _{4 is used} as the electrolyte, the Na ₂ SO ₄ concentration in the aqueous solution is preferably between 0.5 and 2 mol / l, particularly preferably about 1 mol / l.

If phosphates or hydrogen phosphates are used as the electrolyte, the phosphate concentration in the aqueous solution is preferably between 0.1 and 1 mol / l, particularly preferably about 0.5 mol / l.

The solubility can be varied if necessary by adjusting the pH.

The phosphates, for example Na ₂ HP0 ₄ , additionally have a higher viscosity in aqueous solution, so that sealing problems when using the in-case technology in multilayers are reduced at the point of the plunger. Particularly good results were achieved with an approximately 1 m aqueous Na ₂ SO ₄ as the electrolyte. The chemical reactivity, in particular the corrosion, of Na ₂ S0 ₄ as electrolyte is reduced compared to saline. In order to further improve the actuation amplitude of the bucky paper in an actuator, a preferred embodiment of an actuator provides for stacking several thin layers comprising nanotubes, preferably very thin layers of the bucky paper, into multilayers until the desired actuator thickness is reached. Very thin layers of the bucky paper are layers of at least one monolayer, preferably several monolayers, preferably in the range between 100 nm and 100 μm. Thicknesses down to the millimeter range are also possible.

Multilayers are understood to mean at least two, preferably at least 5 and particularly preferably at least 10, nanotube layers stacked one above the other. In principle, there is no restriction regarding the maximum thickness of the actuator.

If desired, a preferably porous contacting layer can be provided between the bucky paper layers, also to allow the electrolyte to pass through quickly. Without a contacting layer, the efficiency of the multilayer stack is reduced since the bucky paper itself yields under load at first. The rigid contact layer serves as a counter bearing for the actuation.

In addition to the greater force, an advantage of contacting is faster actuation, since the entire surface of the bucky paper is contacted.

Areas of application for multilayers with a contacting layer are, for example: Fast and powerful actuators, such as B. Actuators.

The contacting layer can consist of an electrically conductive material. Suitable as electrically conductive materials are metals such as, in particular, noble metals such as silver, gold, platinum, copper, but also aluminum, electrically conductive polymers and others. The materials can be rolled or glued onto the bucky paper as a film. It is also possible to sputter, evaporate, CVD or PVD the metal layer

54341b.doc Apply the process or spin coating to the Bucky paper. The bucky paper can also be grown on a metal layer.

The thickness of the contacting layer is preferably between 1 Dm and 100 Dm, preferably about 5 to 10 Dm, in order to meet the requirements of both a thin and a rigid layer, which of course depends on the respective properties of the contact material.

In principle, the multilayer technique can be used both in the previously known and in the bucky paper according to the invention, the latter being preferred.

With this multi-layer arrangement, the actuation force can be multiplied by the number of individual layer layers of the bucky papers.

A preferred embodiment provides for contacting each individual contacting film in the multilayer at its end which extends beyond the individual bucky paper layers.

Another embodiment provides for the multilayer stack to be built up concentrically or according to the onion principle. This achieves great strength and rapid actuation, so that specific use of actuation through multilayer technology, e.g. B. radial, axial, linear.

Such an actuator in a multi-layer arrangement can be controlled without electrolyte by direct electrical contacting, it being preferred, but not absolutely necessary, to connect the bucky paper layer to the minus and the contacting layer to the positive pole.

S4341b.doc In addition to optimizing the electrolyte, there is also the option of forcing the bucky paper to be actuated without electrolyte. To do this, the voltage and current must be adjusted. A voltage between 0.5 and 100 V, particularly preferably less than 10 V (because of later areas of use) is preferably used. The currents are in the range from micro- to milliamps.

Even the actuation of bucky paper layers or multilayers by E-field alone without physical contacting is possible.

An actuator based on the multilayer technology can also be used in an electrolyte, preferably the electrolyte according to the invention. In order to ensure better penetration of the electrolyte, the contacting layers - like the bucky paper layers - are preferably porous. The application of the actuator based on the multilayer technology is preferably based on the in-case (envelope) technology. Bucky paper and the contacting layers are integrated in an electrolyte to form an actuator strand in a casing. In order to build up the individual bucky paper layers, the individual bucky paper layers can be contacted using bonding technology.

The shell can preferably be changed in at least one dimension, in particular in a main direction of movement of the actuator. The sheath can be designed, for example, as a sealing tube made of polymeric, electrolyte-resistant material, in particular as a polymer housing.

When using the in-case technology, the liquid electrolyte should not have a viscosity that is not too low to prevent it from running out of the plug where the force is taken off. Leakage problems can thus be reduced by suitable selection of the electrolyte. Adequate tightness was achieved, for example, with saturated NaH ₂ P0 ₄ .

54341b.doc With the multilayer technology, on the one hand, actuators for short distances (artificial muscles) can be provided. However, the conversion from electrical to mechanical energy can also be reversed, so that the actuators based on the multilayer technology can also be used, for example, as a load cell, that is to say that a force acting on the stack causes a change in voltage, which is measured and from which the force is generated is determined.

In addition to the standard configuration described in the in-case technology, the bucky paper can be kept free of ions during the relaxation phase if an additional relaxation electrode is used. Both the force and the speed of the actuator can thus be positively influenced.

The actuation characteristic of the actuators also depends on the type of electrical actuation of the actuator. According to the invention, the actuator is preferably controlled by changing the voltage. In principle, however, it is also possible to provide a current-controlled control. The current-controlled control has the advantage that a greater force can be achieved.

The actuation amplitude can also be increased by an electrical polarity corresponding to the electrolyte. This can be achieved by a specific change in the electrical polarity on the software side or also by means of a flip-flop circuit.

In principle, it is possible to contact both the plus and the minus pole with the bucky paper, but a minus contact on the bucky paper and a plus contact on the contacting layer are preferred.

It was also found that the geometry of the bucky paper in the electrolyte also influences the electric fields. Bucky paper with round geometries is preferably used. Elongated or streaked Shaped geometries of the bucky paper are less suitable, but their use is possible in principle.

Due to the mechanical and chemical properties of the bucky paper, a special application technique, in particular shear force decoupling, a special kinematics and the use of the already described in-case technology are preferably used.

In the shear force decoupling, the actuator is provided in a protective housing, the protective housing absorbing shear forces and shear forces on the actuator being avoided. Such protective housings can be made, for example, of stainless steel or high-performance polymers, such as PEEK.

In addition, the amplitude of the acuations and the maximum force are preferably additionally increased using special kinematics. Lever geometries or special geometries and arrangements of the bucky paper in space, such as folding or spiral form, can be used to increase the path or force.

The actuation characteristic can be further improved by increasing the ion velocity by choosing a geometrically close arrangement of the electrodes and their insulation. To further increase the ion velocity, the electrolyte pools can be designed in the form of Venturi tubes. It is also possible to generate electric fields in a targeted manner, on the orbits of which the ions move particularly quickly.

The nanotube actuator optimized according to the invention has the following advantages over the known actuators:

It can be operated with the low voltage of only one volt, which means it is 1000 times lower than with ceramic systems. Can with the actuator according to the invention far greater forces can be achieved than in polymer systems and larger expansions than in ceramic systems. Efficiencies of almost 1 are achieved. In contrast to piezo systems, the maximum expansion is achieved without overshoots. Since there is also an almost linear course between the change in length and the applied voltage and the actuation speed is short, the actuators can also be controlled in several stages - even at short time intervals.

With a density of D = 1.4 g / mm ^{2, the} actuator according to the invention is considerably lighter than alloys. It also has a high temperature resistance, the raw material carbon is inexpensive. The dimensions are also small and the efficiency is high.

Areas of application of the actuator according to the invention include robotics, medical technology, micropositioning technology, the automotive industry, aerospace, precision engineering, production technology and measurement technology.

Because of the advantages mentioned, in addition to the substitution of classic actuators, new areas of application that are critical for high voltage, such as in medical technology (implants, endoscopy) or the interior of motor vehicles, can be developed.

The invention is described in more detail below with reference to figures and exemplary embodiments.

1 shows a schematic representation of a nanotube,

2 shows a schematic top view of the arrangement of the nanotubes in the bucky paper according to the invention,

3 shows a schematic illustration of a bucky paper multilayer,

S4341b.doc 4 shows a schematic illustration of a bucky paper multilayer in in-case technology,

5 shows a schematic illustration of a bucky paper

Multilayers in in-case technology with additional relaxation electrode,

6 shows the rise times of actuators made of carbon nanotube layers in various electrolytes up to half (white) and full (black) deflection,

7 shows the actuators as a function of the electrolytes used,

8 shows the influence of polarity on the change in force as a function of time,

9 shows the change in force / volume as a function of the contact,

10 shows the actuation amplitude with Na ₂ S0 ₄ as electrolyte as a function of time,

11 schematically shows the use of the actuator as an artificial muscle in medical technology,

12 shows the percentage expansion of various previously known actuators compared to nanotube actuators,

13 shows the permissible maximum temperature of previously known actuators in comparison to nanotube actuators and

54341b.doc 14 shows the supply voltage of previously known actuators in comparison to nanotube actuators.

The single-wall nanotubes (SWNT) made of carbon, which are shown schematically in FIG. 1, are perfect carbon tubes with a diameter of a few nanometers and a length in the micrometer range. Manufacturing processes for these nanotubes are known in the prior art (e.g., Science 1340 (1999) with further references).

According to the invention, the nanotubes are not arranged statistically in the layer of the bucky paper, but instead have a preferred orientation in the layer averaged over the nanotube arrangements, as the schematic plan view of the bucky paper according to the invention in FIG. 2 shows. In particular, the angle between the longitudinal axes of the nanotubes and the preferred direction is essentially less than 90 °, preferably less than 60 ° and particularly preferably less than 45 °, up to a particularly preferred arrangement in which the longitudinal axes are oriented essentially parallel to the preferred direction are. To achieve the required strength and the elasticity of the layers, the layer preferably comprises additives which, for example, increase the adhesion and / or flexibly embed the nanotubes.

The arrangement of the bucky paper in the form of multilayers according to the invention is shown in FIG. 3. The bucky paper 11, which preferably each consist of a few monolayer-thick layer of the essentially aligned nanotubes shown in FIG. 2, are stacked to the desired actuator thickness d. Contacting layers 12 made of electrically conductive materials are located between the individual bucky paper layers.

The use of the actuators in multilayer technology with electrolyte in the in-case technology is shown in FIG. 4. The multilayer of the bucky paper 11 and the contacting layers 12 already described in FIG. 3 is integrated together with the electrolyte 13 and the counter electrode 18 in a sleeve 14 made of a polymeric material.

54341b.doc riert. Contacting layers 12 and bucky paper 11 are connected in series. The plunger 16 adjoins the upper bucky paper layer, by means of which the force is transmitted. Adjacent to the plunger 16 there is a sealing lip 17 in the area of the casing 14, which prevents the electrolyte from flowing out.

FIG. 5 shows the additional use of a relaxation electrode 19 in the system described in FIG. 4. The actuation force and the actuation speed can be increased by the relaxation electrode 19.

The rise times of actuators with bucky papers up to half (F _ma χ / 2, white) and full (F _max , black) expansion are shown for various electrolytes in aqueous solution in FIG. 6. Particularly short rise times up to half and maximum expansion are observed in 1 m Na ₂ S0 ₄ , in 0.1 m Na ₂ SO ₄ and in 0.1 m Na ₂ HPO ₄ and Na ₃ P0 ₄ .

According to FIG. 7, the greatest maximum forces are achieved in 1 m KCI and 1 m Na ₂ S0 ₄ . Only about half of the maximum force with 1 m KCI is achieved with 1 m K ₂ S0 ₄ . The maximum force drops significantly at low electrolyte concentrations.

The graph according to FIG. 8 shows the change in force / volume with positive connection (area 1), subsequent disconnection (area 2), subsequent negative connection (area 3) and final disconnection (area 4), each of the bucky paper layers. If the bucky paper layers are connected negatively, a far greater change in force is observed.

Fig. 9 shows the change in force as a function of time for multilayers with different contacts. The graph shows that the best arrangement in the multilayer bucky paper / contacting layer / bucky paper / contacting

54341b.doc layer etc. This is attributed to the fact that the stiffness of the contacting layer has a positive influence on the actuation. Other options, such as contacting layer / bucky paper / bucky paper / contacting layer, do not show such good values.

10 shows the actuation amplitude in Na ₂ SO ₄ as a function of time. 0.8 V / 5 mA was applied to bucky paper and after reaching the maximum force after 5 min. Cut. Voltage was then applied again after 10 minutes. The graph shows that the actuation is reproducible (two waves). A 0.1 mm thick bucky paper takes 5 minutes to reach the maximum force. The maximum force of 0.12 N is reached without overshoot.

11 shows an application example of the actuator in medical technology (implant technology). The multi-layer actuator 21 (instead of the multi-layer actuator, depending on the force required, a single-layer bucky paper can also be used) is located on both sides of the artificial lens 22 of an eye and is connected to the lens by clamping. An electrical control device 23 changes the length of the bucky papers, which changes the lens - as shown in the right figure - compared to the state in the left figure and thus enables the light to be focused on the optic nerve.

12-14 show comparisons of various actuators with regard to the expansion, permissible maximum temperature and supply voltage. (IPMC and IPM are polymer actuators, shape memory alloys are shape memory metals). The Nanotube actuators are characterized by extreme temperature resistance and the lowest supply voltage of all previously known systems. The expansion of the nanotube is small compared to other systems. However, the comparatively small expansion of the nanotube system due to the lever laws causes a far greater force than that which is observed in systems with high expansion, such as polymers.

54341b.doc

Claims

Applicant: Fraunhofer Society for the Promotion of Applied Research eV, Leonrodstraße 54, 80636 Munich 1. Electromechanical actuator, which actuator has at least one layer (11) comprising nanotubes, characterized in that the nanotubes in the layer have a preferred direction averaged over the nanotube arrangements. 2. Actuator according to claim 1, characterized in that the nanotubes in the layer are at least partially, based on their longitudinal axis, arranged in a preferred direction, the nanotubes, based on the preferred direction, preferably at an angle of less than 90 °, preferably less than 60 °, particularly preferably less than 45 °, are aligned up to the parallel arrangement. 3. Actuator according to one of the preceding claims, characterized in that the nanotubes are single or multi-wall carbon nanotubes or nanotubes made of inorganic components, such as BN, MoS ₂ or V ₂ 0 ₅ . 4. Actuator according to claim 3, characterized in that the layer consisting of carbon nanotubes (bucky paper layer) (11) is substantially free of fullerenes, graphite particles and catalyst additives. 5. Electromechanical actuator, which actuator has at least one layer comprising nanotubes (11), in particular according to one of claims 1 to 4, characterized in that the actuator comprises an electrolyte which is selected from the group consisting of alkali and alkaline earth metal, aluminum and Metal salts of the halides, nitrates, sulfates, phosphates, dihydrogen phosphates, hydrogen phosphates, halogenates, perhalogenates, hydroxides, acetates, oxalates or their acids or mixtures thereof is selected. 6. Actuator according to claim 5, characterized in that the electrolyte from LiCl, KCI, LiF, NaF, KF, NaNO ₃ , Na ₂ SO ₄ , Na ₂ P0, Na ₃ PO ₄ , NaCIO ₃ , NaÖ0 or the appropriate lithium, potassium or earth alkali salts and the corresponding acids group is selected. 7. Actuator according to claim 6, characterized in that the solvent of the electrolyte is water or a polar solvent. 8. Actuator according to one of claims 5 to 7, characterized in that the concentration of the electrolyte in the solvent is between 0.1 and 5 mol / l, in particular between 0.2 and 2 mol / l. 9. Actuator according to one of claims 5 to 8, characterized in that the electrolyte is a 0.5 to 2 molar, in particular about 1 molar, aqueous Na ₂ SO ₄ solution. 10. Actuator according to one of claims 5 to 9, characterized in that the electrolyte additionally comprises gelling agents and / or highly viscous electrolytes, such as polyelectrolytes, ionomers or hydrogels swollen with electrolytes. 11. An electromechanical actuator, which actuator comprises at least one nanotube comprising layer (11), in particular according to one of ^'claims 1 to 10, characterized in that at least two, preferably more than 5 and more preferably more than 10 nanotubes extensive layers (11) are stacked into at least one multilayer. 12. Actuator according to claim 11, characterized in that the layers (11) comprising nanotubes are very thin layers of at least one monolayer, preferably several monolayers and particularly preferably thicknesses in the range between 100 nm and 100 μm. 13. Actuator according to one of claims 11 or 12, characterized in that between the layers comprising nanotubes (11), preferably the bucky paper layers, at least one contacting layer (12), preferably in each case between two layers comprising nanotubes, a contacting layer of one electrically conductive material is provided. 14. Actuator according to claim 13, characterized in that the contacting layer (12) is porous and / or comprises a metal, in particular a noble metal or aluminum or a conductive polymer. 5434l3.doc 15. Actuator according to one of claims 5 to 14, characterized in that it comprises at least one multilayer (11, 12) and a liquid electrolyte (13) which are integrated in a sheath (14) which can be changed in at least one dimension, the layers of nanotubes (11) and contacting layers (12) are connected in series and the layers of nanotubes are preferably contacted using bonding technology. 16. Electromechanical actuator, which actuator has at least one layer (11) comprising nanotubes, in particular according to one of the preceding claims, characterized in that for controlling the actuator, a targeted change of polarities by means of a hardware and / or software circuit, in particular a flip Flop circuit is provided. 17. Electromechanical actuator, which actuator has at least one layer (11) comprising nanotubes, in particular according to one of the preceding claims, characterized in that the layer (s) comprising nanotubes have essentially round geometries. 18. Electromechanical actuator, which actuator has at least one layer (11) comprising nanotubes, in particular according to one of claims 11 to 16, characterized in that a shear force decoupling is additionally provided. 19. Electromechanical actuator, which actuator has at least one layer (11) comprising nanotubes, in particular according to one of the preceding claims, characterized in that, in addition to increasing the macroscopic deflections, a special kinematics such as additional levers or a folded or spiral arrangement of the nanotube layers is provided. 54341a.doc 20. Electromechanical actuator, which actuator has at least one layer (11) comprising nanotubes, in particular according to one of claims 11 to 16, characterized in that an additional relaxation electrode (19) is provided. 21. Electromechanical actuator, which actuator has at least one layer (11) comprising nanotubes, in particular according to one of the preceding claims, characterized in that a geometrically close arrangement of the electrodes and insulation is selected to increase the ion velocity and / or the electrolyte pools in Venturi tubes are designed and / or additional electric fields are provided to accelerate the ions. 22. Use of an actuator according to one of claims 1 to 21 as an actuator for short distances, as a load cell, in medical technology, the automotive industry, robotics, micropositioning technology, aerospace technology, precision engineering, measurement technology or production technology , 23. A method for producing an actuator which has at least one layer (11) comprising nanotubes according to one of claims 1 to 21, characterized in that the nanotubes either by an electric, magnetic or electromagnetic field or under the influence of ultrasound in a ten - Align the sidsuspension or align the nanotubes in a suspension using a rotation process so that the nanotubes in the layer essentially have a preferred direction. 24. A method for producing a layer (11) for an actuator comprising carbon nanotubes according to claim 3, characterized in that the impurities are removed by hydrothermal oxidizing methods and subsequent treatment in acids. 54341a doc 25. Process for the production of actuators according to one of the claims. before 13 to 15, which comprise multilayers (11, 12) composed of layers (11) and contacting layers (12) comprising nanotubes, characterized in that the contacting layers (12) on the layers (11) comprising nanotubes by sputtering, vapor deposition, CVD or PVD process or spin coating or the layer comprising nanotubes is grown on a metal layer. 54341a.doc