Aqueous, conductive, printable carbon black-filled ink, process for its preparation, coated article and process for the preparation of the coated article

Abstract

The present invention relates to an aqueous ink comprising at least one functional silicone oil, at least one crosslinking molecule, at least one surfactant, carbon black, and water. Furthermore, the present invention relates to a process for producing an ink as described above. A further aspect of the present invention is a coated article produced by coating a substrate with the aforementioned ink, as well as a process for producing the article. In particular, the present invention relates to an aqueous ink filled with conductive carbon black, the application of the ink by printing processes to elastic substrates such as silicones, polyurethanes, and SEBS (styrene-ethylene-butylene-styrene) plastics, and their use as flexible sensors, actuators, and transducers.

Description

[0001] The present invention relates to an aqueous ink comprising at least one functional silicone oil, at least one crosslinking molecule, at least one surfactant, carbon black, and water. Furthermore, the present invention relates to a process for producing an ink as described above. A further aspect of the present invention is a coated article produced by coating a substrate with the aforementioned ink, as well as a process for producing the article. In particular, the present invention relates to an aqueous ink filled with conductive carbon black, the application of the ink by printing processes to elastic substrates such as silicones, polyurethanes, and SEBS (styrene-ethylene-butylene-styrene) plastics, and their use as flexible sensors, actuators, and transducers. State of the art and disadvantages of the state of the art

[0002] In recent years, the development of stretchable transducers such as sensors, actuators and generators based on the deformation of elastomers has received great interest [F. Carpi, D. DeRossi, R. Kornbluh, R. Pelrine, P. Sommer-Larsen, Dielectric Elastomers as Electromechanical Transducers, Elsevier Ltd., 2008].

[0003] Planned applications of such novel, compliant and damage-resistant transducers are sensors [T. Takahashi, K. Takei, AG Gilies, RS Fearing, A. Javey, Carbon nanotube active-matrix backplanes for conformal electronics and sensors, Nano Letters 11(12) (2011) 5408-5413, T. Sekitani, T. Someya, Stretchable, large-area organic electronics, Advanced Materials 22 (2010) 2228-2246], high-load electroactive actuators [R. Perline, R. Kornbluh, Q. Pei, J. Joseph, High-speed electrically actuated elastomers with strain greater than 100%, Science (2000) 836-839, G. Kovacs, L. Duering, S. Michel, G. Terrasi, Stacked dielectric elastomer actuator for tensile force transmission, Sensors and Actuators A 155 (2009) 299-307], stretchable energy storage and electronic devices [K. Xie, B. Wei, Materials and structures for stretchable energy storage and conversion devices, Advanced Materials 26 (2014) 3592-3617] or artificial muscles [Y.Bar-Cohen, Electroactive Polymer (EAP) Actuators as artificial muscles - Reality, potential, and challenges, 2nd edition, SPIE, Ipswich, MA, 2011, P. Brochu, Q. Pei, Advances in dielectric elastomers for actuators and artificial muscles, Macromolecular Rapid Communication 31 (2010) 10-36, T. Smela, Conjugated polymer actuators or biomedical applications, Advanced Materials 15 (6) (2003) 481-494]. .

[0004] However, to be competitive with established electromechanical transducer technologies, a cost-effective and efficient manufacturing process is required. The electrode composition and deposition process, in particular, represent one of the key elements in this context. Among other materials, silicone elastomers are interesting materials as elastomer dielectrics for stretchable capacitors. They are lightweight, easy to process using a variety of methods, and highly compliant. However, applying electrodes to silicone elastomers is very difficult due to the highly hydrophobic nature of the surface.

[0005] On the other hand, the use of organic solvents such as toluene, hexane, acetone, or isopropanol in carbon black-filled ink formulations can result in solvent penetration into the elastomer layer, leading to reversible deformation of the elastomer layer and thus potentially disrupting the application process [Den Braven, Technical Report TB122013-010]. Like any elastomer, silicone also has the tendency to physically absorb materials with a similar solubility parameter. This absorption causes swelling. The volume changes of silicones caused by solvent absorption are primarily physical. After complete evaporation of the solvent, the silicone will return to its original shape and properties.

[0006] The carbon black-filled inks used to date are based on mixing carbon black with, for example, silicone oil and an organic solvent. Carbon black has been used extensively to produce electrodes for dielectric elastomer actuators (DEAs) because it is sufficiently conductive and has very little influence on the effective stiffness of a DEA. However, this only applies when the carbon black is in powder form or combined with a silicone oil to form a conductive grease in organic solvents. The main disadvantage of carbon black in these formulations is that the carbon black does not adhere well to silicone elastomers and therefore very robust electrodes cannot be formed to date [S. Schlatter, S. Rosset, H. Shea, Inkjet printing of carbon black electrodes for dielectric elastomer actuators, Proc. SPIE 10163, Electroactive Polymer Actuators and Devices (EAPAD), 2017, 1016311 (17 April 2017); doi: 10.1117 / 12.2258615].In addition, the use of organic or silicone-based solvents leads to the swelling of the elastic substrates described above and possibly to the penetration of soot particles into the elastomer layer.

[0007] Another publication [Y. Liao, R. Zhang, H. Wang, S. Ye, Y. Zhou, T. Ma, J. Zhu, LD Pfefferleb, J. Qian, Highly conductive carbon-based aqueous inks toward electroluminescent devices, printed capacitive sensors and flexible wearable electronics, RSC Advances 9 (2019) 15184, DOI: 10.1039 / c9ra01721f] describes the use of a highly conductive, aqueous, carbon black-containing ink that, in addition to the carbon black, also contained multi-wall modified carbon nanotubes and a water-based acrylic resin as a binder and was deposited on paper as a flexible substrate. The use of this ink on elastic substrates, such as silicones, was not described. Object of the present invention

[0008] It is an object of the present invention to develop a stable, aqueous, conductive, printable carbon black-filled ink in an aqueous-dispersible silicone oil matrix containing functional groups, which is subsequently stabilized with crosslinking molecules. This formulation should be suitable for application by printing processes and print very well on hydrophobic, elastic substrates such as silicones. Description of the invention

[0009] This problem is solved by the features of the independent patent claims. The respective dependent patent claims relate to advantageous developments.

[0010] According to a first aspect, the present invention thus relates to an aqueous ink containing or consisting of at least one silicone oil functionalized with at least one functional group, wherein the at least one functional group is capable of undergoing crosslinking via at least one crosslinking molecule reactive with the at least one functional group, at least one crosslinking molecule reactive with the at least one functional group of the silicone oil, at least one surfactant, carbon black, and water.

[0011] This results in an aqueous, carbon black-based conductive ink with a water-dispersible, silicone-containing matrix that can be printed and undergoes stabilization upon drying through additional crosslinking within the layer. On the one hand, the use of water as a solvent prevents swelling of the elastomer layer. On the other hand, the water-dispersible silicone matrix enables the ink to be printed on the highly hydrophobic silicone elastomer and subsequently crosslinked, forming highly stable electrode layers.

[0012] According to a preferred embodiment, the at least one functional group is a nucleophilic functional group and is in particular selected from the group consisting of amino groups, hydroxyl groups, and thiol groups,

[0013] The electrophilic functional group may in particular be a functional group selected from the group consisting of carboxylic anhydride groups, carbonyl groups, carboxyl groups, carboxylic acid ester groups, sulfonic acid ester groups (e.g. tosylate, triflate) and groups containing a halogen atom.

[0014] More preferably, the at least one crosslinking molecule has a polarity complementary to the at least one functional group and is in particular electrophilic if the functional group is a nucleophilic functional group or nucleophilic if the functional group is an electrophilic functional group.

[0015] Particularly preferably, the at least one crosslinking molecule is electrophilic and is selected from the group consisting of maleic anhydride, glyoxal and mixtures and combinations thereof.

[0016] It is further advantageous if the silicone oil is aminofunctionalized, wherein the amino number is preferably 0.05 to 5.0 ml 1N HCl / g, preferably 0.1 to 2.0 ml 1N HCl / g, particularly preferably 0.15 to 0.4 ml 1N HCl / g and the crosslinking molecule is glyoxal or maleic anhydride.

[0017] Preferably, the total solids content of the aqueous ink is from 0.1 to 30 wt.%, preferably from 0.5 to 20 wt.%, more preferably from 1.0 to 10 wt.%, particularly preferably from 1.5 to 5.0 wt.%.

[0018] It is preferred if the proportion of carbon black in the total solids content of the ink is from 5 to 60%, preferably 20 to 40%.

[0019] The carbon black used in the aqueous ink preferably has a BET surface area of ​​500 to 1200 m 2 / g, preferably 800 to 1100 m 2 / g and densities of approx. 1.0 to 2.5 g / cm 3 , preferably 1.6 to 2.0 g / cm 3An exemplary determination of the BET surface area can be carried out, for example, according to DIN ISO 9277:2014.

[0020] A further advantageous embodiment provides that the molar ratio of the total of all functional groups of the silicone oil to the total of the crosslinking molecules is from 1:10 to 10:1, preferably from 1:5 to 5:1, particularly preferably from 1:2 to 2:1.

[0021] In particular, the at least one surfactant is selected from the group consisting of non-ionic surfactants, in particular polyalkylene glycol ethers and / or (p-tert-octylphenoxy)-polyethoxyethanols, wherein the aqueous ink preferably contains two different surfactants.

[0022] Preferably, the total content of the at least one surfactant in the aqueous ink is from 0.10 to 5.0 wt.%, preferably from 0.15 to 1.0 wt.%, more preferably from 0.20 to 0.50 wt.%, particularly preferably from 0.25 to 0.40 wt.%.

[0023] In a further aspect, the present invention relates to a process for producing an aqueous ink according to the invention as described above, in which a first aqueous solution or dispersion containing or consisting of the at least one functionalized silicone oil, the at least one crosslinking molecule and at least one first surfactant, a second aqueous dispersion containing or consisting of carbon black and a second surfactant, are mixed.

[0024] According to a preferred embodiment of the method, it is provided that the at least one first and the at least one second surfactant are different from one another, wherein preferably the at least one first surfactant is selected from the group consisting of polyalkylene glycol ethers and the at least one second surfactant is selected from the group consisting of (p-tert-octylphenoxy)-polyethoxyethanols.

[0025] Furthermore, the present invention relates to a coated article comprising or consisting of a substrate with a coating applied at least partially or completely to at least one surface, which coating was produced by applying and crosslinking an ink according to the invention as described above.

[0026] It is particularly preferred that the crosslinking is or was carried out by heat treatment, preferably at temperatures of 20 to 200 °C, preferably at 50 to 150 °C, particularly preferably at 80 to 125 °C.

[0027] Further advantageously, the substrate comprises or consists of a material selected from the group consisting of polymers, in particular silicones, polyurethanes, styrene-ethylene-butylene-styrene rubbers, polyacrylates or combinations thereof.

[0028] The coating of the coated article has a thickness of 0.1 to 50 µm, preferably 1 to 20 µm, completely or in regions.

[0029] In an exemplary embodiment, the coated article may also have a stacked structure and be iteratively formed from a plurality of substrates and coatings.

[0030] The present invention also relates to the use of the above-described coated article according to the invention as a flexible sensor, actuator, transducer or flexible dielectric.

[0031] In addition, the present invention relates to a method for producing a coated article as described above, in which an aqueous ink according to the invention as described above is applied at least partially or completely to a surface of a substrate and then crosslinked.

[0032] In this process, application is preferably carried out by means of inkjet printing, dispensers, dosing devices, pad printing, doctor blade coating, doctor blade coating, spin coating, slot die coating, spray coating, screen printing.

[0033] It is further advantageous that the crosslinking is carried out by heat treatment, whereby a crosslinking reaction of the functional silicone oil takes place, whereby the heat treatment is preferably carried out at temperatures of 20 to 200 °C, preferably at 50 to 150 °C, particularly preferably at 80 to 125 °C.

[0034] For example, the heat treatment can be carried out over a period of 1 to 60 minutes, preferably 5 to 20 minutes.

[0035] Preferably, a drying step is carried out before the heat treatment, preferably at temperatures of 20 to 80 °C.

[0036] A further preferred embodiment of the method according to the invention for producing the coated article provides that a coated article with a stack structure is produced by iteratively applying and crosslinking aqueous ink on a substrate as described above and subsequently applying a further substrate layer on the coating of the crosslinked ink.

[0037] Preferred embodiments of the invention are described below.

[0038] The object of the invention formulated at the outset is achieved by way of example and in particular by using water-based, functionalized silicone oils which are self-dispersing in water and which are provided, for example, with hydroxyl, amine or carboxyl groups, as a matrix. A water-soluble crosslinking molecule such as maleic anhydride or glyoxal is additionally added to this solution. This matrix solution is combined with an aqueous solution containing carbon black, which is additionally stabilized by the addition of surfactants. The self-dispersing, functionalized silicone oils which are provided, for example, with hydroxyl, amine or carboxyl groups, subsequently form the compatible matrix with the elastic substrate and, on the other hand, the compatibility with water through the hydrophilic functionalization.The addition of a water-soluble crosslinking molecule enables the layer to bond with the silicone-containing matrix during drying, thus contributing to the stabilization of the soot particles on the silicone. The ink formulation prepared in this way can then be used for printing electrodes on silicone elastomers. This allows for the creation of durable, stretchable electrodes on silicone elastomers. Since water is used as the solvent, swelling of the elastomer layer is also prevented. Furthermore, the use of water as a solvent is very environmentally friendly.

[0039] First, commercially available water-dispersible silicone oils containing functional groups such as amine, carboxy, or hydroxy groups are diluted with a surfactant to approximately 2-8 wt.%. Water-soluble crosslinking molecules such as maleic anhydride (MA) or glutaraldehyde (GLA) are then added. Another aqueous dispersion was prepared with the carbon black. For example, carbon black was dispersed with a surfactant in water using ultrasonic treatment. Dispersions with a solids content of approximately 0.5 to 10 wt.% were produced.

[0040] Both solutions are gently mixed while stirring. These aqueous solutions have total solids contents between 0.5 and 20 wt.%, preferably between 1 and 10 wt.%, and particularly preferably between 1.5 and 5 wt.%, with the carbon black solids content being between 5 and 60 wt.%, preferably between 20 and 40 wt.%. The resulting aqueous ink can then be used for inkjet printing. A subsequent tempering step initiates crosslinking, providing additional stabilization to the printed layers. The result is printed layers with layer thicknesses in the range of 1 to 20 µm.

[0041] This printing process can also be used to build stacks (multi-layer systems), for example, for actuators. For example, the elastomer layers can first be produced using wet chemical methods, such as doctor blade coating or spin coating. The electrodes are then applied to them using a printing process. An elastomer is then repeatedly spin coated or doctor blade coated over the top, and the electrodes are then applied again using a printing process, and so on.

[0042] The present invention is described in more detail with reference to the following examples, without limiting the invention to the specific parameters shown. Preparation of the aqueous, silicone-containing matrix

[0043] As a water-dispersible silicone oil, WETSOFT ®LV 810 was used. This is a commercially available self-dispersing polyetheraminofunctional silicone oil with a reduced content of cyclic siloxanes, which is normally used in the textile industry. The amine number is 0.25 ml 1 N HCl / g, the solids content is 80%, and the dynamic viscosity is 1000-6000 mPas at 25°C. A spatula tip of a Brij 98 surfactant (HLB value 13) was added to 30 ml of deionized water and heated to 40°C with stirring. 15 ml of the WETSOFT solution was then added in portions with vigorous stirring. ® LV 810. This mixture was stirred for a further 2 hours. This stock solution is stable for weeks.

[0044] 3.5 g of the 27 wt.% WETSOFT ®The LV 810 solution was further diluted with 20.12 g of water to form a 4 wt.% solution. 4.2 mg of maleic anhydride (5 wt.% based on the solids content) was added to 2 g of this 4% solution as a crosslinker, and the solution was stirred until a homogeneous mixture was obtained. Preparation of the aqueous carbon black-containing dispersion

[0045] 0.75 g of carbon black (Printex XE2) was weighed into a flask, followed by 50 ml of water and 0.3 ml of TritonX-100. The dispersion was briefly stirred and then dispersed using an ultrasonic finger (Sonoplus, HD2070, Bandelin) according to the following regime: • 15 min, power 40%, pulsation mode: working step 0.1 s, resting step 0.9 s • 30 min, power 100%, pulsation mode: working step 0.2 s, resting step 0.8 s • 30 min, power 70%, pulsation mode: working step 0.1 s, resting step 0.9 s • 30 min, power 30%, pulsation mode: working step 0.3 s, resting step 0.7 s

[0046] During homogenization, the flask is cooled in an ice bath to prevent evaporation of the water. Combining the aqueous, silicone-containing matrix with the aqueous carbon black-containing dispersion

[0047] To 2 g of the aqueous, silicone-containing matrix solution, 2.03 g of the Carbon Black Printex solution are first slowly added in portions at 20°C and then stirred using a stir bar. This solution is then used for printing. Printing process and structure of the electrodes on the silicone elastomer films

[0048] The ink was then printed on Wacker Elastosil 2030 silicone films (50 µm thick) using a GESIM Nano-Plotter NP 2.1 with a Vermes MDS 3200A microdispensing system, without any further pretreatment of the silicone films. The following printing parameters were used: • Rising: 0.5 ms • Falling: 1.0 ms • Open: 0.3 ms • Delay: 1.0 ms • No-of-Pulses: 3 • Needle lift: 40%

[0049] After printing, the electrodes were first dried for 20 min at 20°C and then for 10 min at 105°C. Fig. Figure 1 shows printed electrodes with the measurement valve on the Gesimplotter based on the aqueous ink formulation with MSA crosslinker. Fig. Figure 2 shows the structure of a multilayer system with printed electrodes with a measurement valve on the Gesimplotter with the aqueous ink formulation with MSA crosslinker and spin-coated silicone layers. Use of a different cross-linking agent

[0050] Instead of using maleic anhydride, glyoxal can also be added as a crosslinking agent. Here, 5 wt.% of glyoxal, based on the solids content, was also used. This silicone-containing matrix solution was also combined with the carbon black-containing solution as described above and printed in a stack on both commercially available elastomer films (Wacker Elastosil 2030, thickness 50 µm) and on the films produced separately here using wet-chemical processing.

[0051] Fig. Figure 3 shows printed electrodes (a) and multilayer structure of Eilikon elastomers and printed electrodes (b) using glyoxal as crosslinking agent. Electrical properties of the electrodes

[0052] The conductivity of the processed layers was determined by resistance measurements using the four-point method. The processed electrode layers exhibited conductivities in the range of 4 to 6 kOhm / square. Electrical properties of the electrodes under stretching

[0053] To characterize the electrodes under mechanical stretching, they were applied to Wacker Elastosil 2030 silicone films using inkjet printing with a geometry of 30 mm length and 10 mm width, as described above. The elastomer films with electrodes were clamped lengthwise, and the electrode resistance was measured over a length of 30 mm. This was also carried out at various cyclic stretchings of, for example, 3.3; 6.6; 10; 20; and 30% and at a speed of 3 mm / s, see Figure 1. Fig. 4.

[0054] Fig. Figure 4 shows the electrical resistance of the electrodes applied to silicone films made of aqueous ink formulation during different stretchings, length of the electrode 30 mm. Electromechanical properties of dielectric elastomer actuators with electrodes prepared via an aqueous ink formulation

[0055] Flexible electrodes are used, for example, in dielectric elastomer actuators (DEA) [F. Carpi, D. DeRossi, R. Kornbluh, R. Pelrine, P. Sommer-Larsen, Dielectric Elastomers as Electromechanical Transducers, Elsevier Ltd., 2008, R. Perline, R. Kornbluh, Q. Pei, J. Joseph, High-speed electrically actuated elastomers with strain greater than 100%, Science (2000) 836-839, P. Brochu, Q. Pei, Advances in dielectric elastomers for actuators and artificial muscles, Macromolecular Rapid Communication 31 (2010) 10-36]. These consist of an elastomer film (typically silicone, elastic modulus e.g. approx. 1 MPa, thickness e.g. 20-100 µm) with flexible electrodes applied to both sides of the film surface. The application of potential differences in the kilovolt range to the two electrodes leads to electrical attraction between the electrodes and thus, due to the softness of the elastomer film, to a reduction in its thickness.Since the elastomer is incompressible, this reduction in thickness leads to an increase in the surface area of ​​the elastomer film and thus to actuator movement. This expansion is in the range of a few percent, and in some scientific studies, significantly higher. The electrodes must also undergo corresponding expansion or stretching.

[0056] According to the described actuator mode, the actuator performance of the DEA is simply measured by detecting, for example, the change in length of an actuator sample strip (as in Fig. (shown on the left) while applying an electric field between the two applied flexible electrodes.

[0057] DEA constructed with electrodes made from aqueous ink formulations show comparable actuator expansions as DEA constructed with electrodes printed from solvent-based ink formulations, compare Fig.5, which shows the actuator expansions of DEA with electrodes printed from aqueous or solvent-based ink formulations. QUOTES CONTAINED IN THE DESCRIPTION

[0000] This list of documents submitted by the applicant was generated automatically and is included solely for the convenience of the reader. This list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions. Cited non-patent literature

[0000] F. Carpi, D. DeRossi, R. Kornbluh, R. Pelrine, P. Sommer-Larsen, Dielectric Elastomers as Electromechanical Transducers, Elsevier Ltd., 2008 [0002, 0055] T. Takahashi, K. Takei, AG Gilies, RS Fearing, A. Javey, Carbon nanotubeactive-matrix backplanes for conformal electronics and sensors, Nano Letters 11(12) (2011) 5408-5413

[0003] T. Sekitani, T. Someya, Stretchable, large-area organic electronics, Advanced Materials 22 (2010) 2228-2246

[0003] R. Perline, R. Kornbluh, Q. Pei, J. Joseph, High-speed electrically actuated elastomers with strain greater than 100%, Science (2000) 836-839 [0003, 0055] G. Kovacs, L. Duering, S. Michel, G. Terrasi, Stacked dielectric elastomer actuator for tensile force transmission, Sensors and Actuators A 155 (2009) 299-307

[0003] K. Xie, B. Wei, Materials and structures for stretchable energy storage and conversion devices, Advanved Materials 26 (2014) 3592-3617

[0003] Y. Bar-Cohen, Electroactive Polymer (EAP) Actuators as artificial muscles - Reality, potential, and challenges, 2nd edition, SPIE, Ipswich, MA, 2011

[0003] P. Brochu, Q. Pei, Advances in dielectric elastomers for actuators and artificial muscles, Macromolecular Rapid Communication 31 (2010) 10-36 [0003, 0055] T. Smela, Conjugated polymer actuators or biomedical applications, Advanced Materials 15 (6) (2003) 481-494

[0003] Den Braven, Technischer Bericht TB122013-010

[0005] S. Schlatter, S. Rosset, H. Shea, Inkjet printing of carbon black electrodes for dielectric elastomer actuators, Proc. SPIE 10163, Electroactive Polymer Actuators and Devices (EAPAD), 2017, 1016311 (17 April 2017); doi: 10.1117 / 12.2258615

[0006] Y. Liao, R. Zhang, H. Wang, S. Ye, Y. Zhou, T. Ma, J. Zhu, L. D. Pfefferleb, J. Qian, Highly conductive carbon-based aqueous inks toward electroluminescent devices, printed capacitive sensors and flexible wearable electronics, RSC Advances 9 (2019) 15184, DOI: 10.1039 / c9ra01721f

[0007]

Claims

[1] Aqueous ink containing or consisting of at least one silicone oil functionalized with at least one functional group, wherein the at least one functional group is capable of undergoing crosslinking via at least one crosslinking molecule reactive with the at least one functional group, at least one crosslinking molecule reactive with the at least one functional group of the silicone oil, at least one surfactant, Soot, as well as Water. [2] Aqueous ink according to claim 1, characterized bythat the at least one functional group is a nucleophilic functional group and is in particular selected from the group consisting of amino groups, hydroxyl groups and thiol groups. electrophilic functional group, in particular a functional group selected from the group consisting of carboxylic anhydride groups, carbonyl groups, carboxyl groups, carboxylic acid ester groups, sulfonic acid ester groups (e.g. tosylate, triflate) and groups containing a halogen atom. [3] Aqueous ink according to any one of the preceding claims, characterized by that the at least one crosslinking molecule has a polarity complementary to the at least one functional group, in particular is electrophilic if the functional group is a nucleophilic functional group or is nucleophilic if the functional group is an electrophilic functional group. [4] Aqueous ink according to any one of the preceding claims, characterized bythat the at least one crosslinking molecule is electrophilic and is selected from the group consisting of maleic anhydride, glyoxal and mixtures and combinations thereof. [5] Aqueous ink according to any one of the preceding claims, characterized by that the silicone oil is aminofunctionalized, wherein the amino number is preferably 0.05 to 5.0 ml 1N HCl / g, preferably 0.1 to 2.0 ml 1N HCl / g, particularly preferably 0.15 to 0.4 ml 1N HCl / g and the crosslinking molecule is glyoxal or maleic anhydride. [6] Aqueous ink according to any one of the preceding claims, characterized by a total solids content of 0.1 to 30 wt.%, preferably 0.5 to 20 wt.%, more preferably 1.0 to 10 wt.%, particularly preferably 1.5 to 5.0 wt.%. [7] Aqueous ink according to any one of the preceding claims, characterized by that the proportion of carbon black in the total solids content of the ink is from 5 to 60%, preferably 20 to 40%. [8] Aqueous ink according to any one of the preceding claims, characterized by that the soot has BET surface areas of 500 to 1200 m 2 / g, preferably 800 to 1100 m 2 / g and densities of approx. 1.0 to 2.5 g / cm 3 , preferably 1.6 to 2.0 g / cm 3 has. [9] Aqueous ink according to any one of the preceding claims, characterized by that the molar ratio of the total of all functional groups of the silicone oil to the total of the crosslinking molecules is from 1:10 to 10:1, preferably from 1:5 to 5:1, particularly preferably from 1:2 to 2:

1. [10] Aqueous ink according to any one of the preceding claims, characterized by that the at least one surfactant is selected from the group consisting of non-ionic surfactants, in particular polyalkylene glycol ethers and / or (p-tert-octylphenoxy)polyethoxyethanols, wherein the aqueous ink preferably contains two different surfactants. [11] Aqueous ink according to any one of the preceding claims, characterized by that the total content of the at least one surfactant in the ink is 0.10 to 5.0 wt.%, preferably 0.15 to 1.0 wt.%, more preferably 0.20 to 0.50 wt.%, particularly preferably 0.25 to 0.40 wt.%. [12] A process for producing an aqueous ink according to any one of the preceding claims, characterized by , that a first aqueous solution or dispersion containing or consisting of the at least one functionalized silicone oil, the at least one crosslinking molecule and at least one first surfactant, a second aqueous dispersion containing or consisting of carbon black and a second surfactant, be mixed. [13] Method according to the preceding claim, characterized bythat the at least one first and the at least one second surfactant are different from one another, wherein preferably the at least one first surfactant is selected from the group consisting of polyalkylene glycol ethers and the at least one second surfactant is selected from the group consisting of (p-tert-octylphenoxy)-polyethoxyethanols. [14] Coated article comprising or consisting of a substrate with a coating applied at least partially or completely to at least one surface, which coating was produced by applying and crosslinking an ink according to one of claims 1 to 11. [15] Coated article according to the preceding claim, characterized by that the crosslinking is carried out by heat treatment, preferably at temperatures of 20 to 200 °C, preferably at 50 to 150 °C, particularly preferably at 80 to 125 °C. [16] Coated article according to one of the two preceding claims, characterized bythat the substrate comprises or consists of a material selected from the group consisting of polymers, in particular silicones, polyurethanes, styrene-ethylene-butylene-styrene rubbers, polyacrylates or combinations thereof. [17] Coated article according to any one of claims 14 to 16, characterized by that the coating has a thickness of 0.1 to 50 µm, preferably 1 to 20 µm, completely or in regions. [18] Coated article according to any one of claims 14 to 17, characterized by that it has a stacked structure and iteratively comprises a plurality of substrates and coatings. [19] Use of a coated article according to any one of claims 14 to 18 as a flexible sensor, actuator, transducer or flexible dielectric. [20] A method for producing a coated article according to any one of claims 14 to 18, wherein an aqueous ink according to any one of claims 1 to 11 is applied at least partially or completely to a surface of a substrate and then crosslinked. [21] Method according to the preceding claim, characterized by that the application is carried out by means of inkjet printing, dispenser, dosing device, pad printing, doctor blade coating, spin coating, slot die coating, spray coating, screen printing. [22] Method according to one of the two preceding claims, characterized by that the crosslinking is carried out by heat treatment, whereby a crosslinking reaction of the functional silicone oil takes place, wherein the heat treatment is preferably carried out at temperatures of 20 to 200 °C, preferably at 50 to 150 °C, particularly preferably at 80 to 125 °C. [23] Method according to the preceding claim, characterized bythat the heat treatment is carried out over a period of 1 to 60 minutes, preferably 5 to 20 minutes. [24] Method according to one of the two preceding claims, characterized by that a drying step is carried out before the heat treatment, preferably at temperatures of 20 to 80 °C. [25] Method according to one of claims 20 to 24, characterized by that a coated article with a stack structure is produced by iteratively applying and crosslinking aqueous ink on a substrate according to one of claims 20 to 24 and subsequently applying a further substrate layer on the coating of the crosslinked ink.

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