Ferroelectric Sensor

Abstract

A sensor (1) is described, which consists of a first electrode (3a), a ferroelectric layer (2) and a second electrode (3b), the second electrode (3b) being grounded and the ferroelectric layer (2) being disposed between the first electrode (3a) and the second electrode (3b).

Description

[Technical field]

[0001] The present invention relates to a ferroelectric sensor. [Background technology]

[0002] Due to the increasing digitalization currently being promoted under the terms Industry 4.0 or the Internet of Things, interactions between machines and with humans are becoming more and more commonplace. One of the many challenges is to increase the safety of humans and machines in these interactions by avoiding accidents.

[0003] In this context, various types of sensors, often based on various physical effects, are integrated into increasingly intelligent machines in order to detect dangers and avoid possible collisions. On the one hand, optical sensors or camera modules can be used for early detection of possible dangers thanks to the range of their detection field. On the other hand, ultrasonic sensors are suitable for measuring at close ranges, for example, and can therefore detect obvious dangers. In the immediate area, i.e. when contact occurs between the machine and the surroundings, capacitive or resistive sensors, such as contact protection strips, can be used for contact detection.

[0004] Partially or fully autonomous machines often incorporate multiple different types of sensors to prevent collisions, which cover different areas and therefore can create a more complete picture of the surroundings.

[0005] Nevertheless, integrating multiple sensors of different types into an application is costly. Moreover, the use of different types of sensors is associated with high technical costs. Different sensor types require their own control and evaluation electronics, which makes the whole sensor system more complex and larger. Moreover, each different type of sensor must be subjected to at least one continuous and specific functional test of its own, which constantly checks the sensors and electronics, further expanding the whole system.

[0006] Therefore, a sensor that functions based on a variety of physical effects and integrates various types of sensors within itself is desirable. Summary of the Invention [Problem to be solved by the invention]

[0007] It is an object of the present invention to provide a sensor which generates a measurement signal based on different physical effects. [Means for solving the problem]

[0008] This problem is solved by a sensor according to claim 1. Further advantageous embodiments and possible configurations can be seen from the further claims.

[0009] A sensor is described that consists of a first electrode, a ferroelectric layer, and a second electrode, the ferroelectric layer being disposed between the two electrodes, and the second electrode being connected to ground.

[0010] The measurement signal can be picked up as a voltage change between the electrodes. The earth can be at earth potential.

[0011] The ferroelectric layer here can consist of a material which exhibits ferroelectric properties in an electric field. Preferably, the layer consists of a ferroelectric material with piezoelectric properties, particularly preferably of a ferroelectric material with pyroelectric properties.

[0012] Since all pyroelectric materials are also piezoelectric materials, the functional layer between the electrodes is sensitive not only to temperature changes, but also to any deformation of the sensor due to the piezoelectric effect. Since one of the electrodes is grounded, any significant approach or contact with the electrode can change the capacitance between the approaching object and the electrode, and can also result in a voltage change between the electrodes. In this way, three different physical effects can be effectively utilized in one sensor: the capacitive effect, the piezoelectric effect and the pyroelectric effect.

[0013] The integration of the pyroelectric, piezoelectric and capacitive effects in one sensor is particularly advantageous, since the three effects are suitable for the detection of different events. The pyroelectric effect allows temperature changes resulting from the environment to be recorded. Temperature changes resulting from, for example, human body temperature or machine heat generation can be determined from a distance without contact. The capacitive effect can also be used for contactless detection, but this requires a large proximity to the sensor. However, it is advantageous to be able to detect proximity by the capacitive effect, even if the detection of the pyroelectric effect due to the proximity of an object of the same temperature would result in no or only a small sensor signal. The piezoelectric or capacitive effect can be effectively used to complement the pyroelectric effect and to grasp the contact of the sensor with another object. Furthermore, the piezoelectric or capacitive effect can allow improved detection, since in the same sensor, the voltage signal generated by the pyroelectric effect is 10 to 100 times weaker than the piezoelectric or capacitive effect. The piezoelectric effect is distinguished from the capacitive effect in that for a voltage change at the electrode, an active spatial deformation of the piezoelectric layer must occur, whereas in the capacitive effect, already static contact leads to a voltage change. Thus, with the piezoelectric effect, for example, in the case of a spatially externally arranged sensor that is flexible and bent by an approaching object, a voltage change is caused by the bending of the piezoelectric layer. The voltage change is suitable for measuring the distance to the approaching object, since the magnitude of the voltage change depends on the degree of bending. In contrast, if the deformed piezoelectric layer is stationary or no deformation occurs, no voltage change due to the piezoelectric effect occurs. In this case, the capacitive effect comes into play, which leads to a voltage change between the electrodes when the grounded electrodes come into contact, even without deformation of the layer.

[0014] The ability of sensors to utilize different physical effects as the basis for detection allows a reduction in the number of different types of sensors that must be integrated into an application. Furthermore, the required control and evaluation electronics can be simplified and streamlined, since they do not have to be provided separately for each sensor type. Furthermore, if different physical effects that cover complementary detection areas are used in the sensor, a more accurate overview of the surroundings is given, and therefore the approach of an object can be confirmed.

[0015] The measured changes in the electrical signal may include changes in the signal-time course and / or amplitude and / or time scale and / or time dynamics and / or polarity, thus making it possible to know the full dynamics of the electrical signal.

[0016] The electrical signal may comprise a voltage and / or a charge and / or a capacitance and / or a polarity, and therefore may be independent of the type of measurement or the measurements may be based on different measurement principles.

[0017] The ferroelectric layer can comprise a polymer, a ceramic or a polymer-ceramic matrix, where as the polymer polyvinylidene fluoride (PVDF) and its copolymers can be used, and as the ceramic lead zirconate titanate (PZT) or BaTiO3 can be used. The aforementioned examples are ferroelectric materials that have pyroelectric properties and meet industrial requirements. PVDF is flexible and therefore a particularly suitable pyroelectric plastic. Suitable methods for applying PVDF onto the first electrode can be spin coating, screen printing or inkjet printing. In contrast, PZT and BaTiO3 are pyroelectric ceramics that are flexible only as thin layers. PZT ceramics can additionally be doped with Na, Ca or La to adapt the electrical properties. If the pyroelectric layer is PZT, BaTiO3 or other lead-free or lead-containing ceramics, it can be applied onto the first electrode by thin film processes such as CVD, PVD, a combination of sol-gel methods and spin coating or by screen printing.

[0018] Both the first and second electrodes can be made of a material that is transparent and / or thermally conductive in the UV-Visible and / or preferably IR range, thereby ensuring that the infrared thermal radiation reaches the ferroelectric layer directly, thus increasing the sensitivity of the sensor. Suitable materials can be, for example, ITO, PEDOT:PSS, graphite, metal nanowires, carbon nanotubes or graphene.

[0019] In addition, the electrode can consist of or contain one or more layers of metals such as Al, Cr, Ni, Ag, Cu, or mixtures, intermetallic compounds and alloys of these elements. It is preferably a sputtered layer. In the case of a sputtered layer, several layers of different metals, for example Cr / Ni / Ag, can also be sputtered one on top of the other. Through the selection of the respective metal, the contact of the sensor, for example by soldering, can be improved, since better fastening is possible. Electrodes made of metals have high electrical and thermal conductivity, so that the sensitivity of the sensor is not significantly impaired.

[0020] The sensor may further comprise a first electrode, a second electrode and a ferroelectric layer, the ferroelectric layer being disposed between the first and second electrodes. By realising the sensor as a multi-layer component, multiple functional ferroelectric layers may be sequenced, improving both the sensitivity and accuracy of the sensor.

[0021] The arrangement on or between the components can be either a direct arrangement, where the arranged components contact each other and rest directly on top of each other, or an indirect arrangement, where there can be additional components between the overlapping arranged components. In either case, the electrodes are arranged directly on the ferroelectric layer, so that the electrodes contact the ferroelectric layer and establish electrical contact.

[0022] In a multi-layer component, the individual functional layers can be contacted separately, with the first electrodes being electrically contacted with respective separate first contact elements and the second electrodes being electrically contacted with respective separate second contact elements, so that separate sensor signals can be evaluated for each functional layer and furthermore it is possible to pick up different types of sensor signals for the individual functional layers.

[0023] Alternatively, in the multi-layer component, all first electrodes can be electrically contacted with the same first electrical contact element and all second electrodes can be electrically contacted with the same second electrical contact element. Thus, all first electrodes are connected in parallel with one another and all second electrodes are connected in parallel with one another. Electrical signals can be picked up between the contact elements. This makes an amplified signal available for evaluation, in the sense of signal addition of the sensor signal from the signals of the individual functional layers.

[0024] Furthermore, the first electrode can be arranged inside the sensor, the ferroelectric layer can cover the first electrode, and the second electrode can cover the ferroelectric layer. Such an embodiment can preferably be formed in a cylindrical or plate-like shape. The layers in the sensor can be arranged such that the extent of the sensor in a direction perpendicular to the layers of the sensor is short compared to the extent of the sensor along the layers. This embodiment allows a myriad of further applications for the sensor according to the invention. Furthermore, the cylindrical shape of the sensor is beneficial for increasing the sensitivity to deformations. Also, the covered sensor can be manufactured in an endless process, similar to the manufacturing of a wire or cable, which allows for cheap manufacturing.

[0025] According to one possible use of the term "covering", a layer can also be considered covered by another layer if the covering layer covers the layer below it but not completely but to a large extent. If cross-sectional images are taken across the layer, a layer can be considered covered if more than 90%, 95%, 99% or 99.9% of the cross-sectional images do not have defects in the covering layer that extend over the entire thickness of the layer. During the production of a layer, defects or cracks can unavoidably occur in the layer, which can make complete coverage difficult. During operation, mechanical loads can also cause cracks in the layer of the sensor, but this only interferes with the function of the sensor to a limited extent. A layer or component covered by a layer can alternatively be completely enveloped by the layer.

[0026] Furthermore, the sensor can have an insulating layer on which the first electrode or the second electrode can be disposed, and the sensor can be wound such that the insulating layer is located on the inside. The inner surface faces toward the central axis of the sensor in the wound sensor and away from the outer surface of the sensor. The winding results in a helical electrode in a cross section through the sensor and a ferroelectric layer that extends in a helical shape in a cross section through the sensor and sandwiched between the similarly helical electrodes. Thus, the one of the electrodes that is not disposed directly on the insulating layer forms the outer surface of the wound sensor.

[0027] The rolled sensor can preferably be formed in a cylindrical shape. By rolling the sensor, it is also possible to manufacture a cylindrical sensor by the manufacturing process for flat layers. The insulating layer is mainly used to electrically insulate the electrodes that would otherwise short when rolled. If the sensor is rolled multiple times, a multi-layer member is created, but the sensor only has a first and a second electrode. The electrical behavior is significantly different from the coated embodiment with multiple stacked layers, because in the case of the rolled sensor, a single capacitance is formed that corresponds to a parallel connection of capacitors, while in the case of the coated embodiment with multiple stacked layers, the capacitance formed between the electrodes corresponds to a series connection of capacitors. Thus, for a comparable number of layers, materials and dimensions, a higher capacitance is created for the rolled sensor, which makes the capacitive effect significantly more pronounced in the sensor.

[0028] Furthermore, the sensor can have a carrier material. Depending on the field of application, the carrier material can be inelastic or elastic. Inelastic carrier materials can improve the mechanical stability of the sensor. Especially for the transportation and installation of the component, high mechanical stability can be useful to avoid damage. For certain applications, placement on a carrier material made of glass, concrete or steel can be necessary, although the piezoelectric effect is thereby reduced. Elastic materials that come into consideration as carrier materials can be, inter alia, rubber, plastic or woven fabrics, such as polyester.

[0029] The first electrode or the second electrode can be disposed on a carrier material. It should be noted that sufficient adhesion between the electrode and the carrier material is necessary. Sufficient adhesion can be obtained by appropriately selecting the material of the carrier material and the electrode. Surface treatment of the carrier material, such as roughening, can also be carried out to improve adhesion between the carrier material and the electrode.

[0030] Furthermore, the sensor can have an insulating layer on which the first or second electrode is arranged, and the sensor is wound so that the insulating layer is located on the carrier material. Thus, through the selection of the carrier material, the mechanical stability of the wound sensor can be controlled. Such an arrangement opens up a large number of possible application areas for the sensor, since various materials and even articles are taken into consideration as the carrier material. By winding the sensor, the capacitive effect of the sensor is increased.

[0031] In a further embodiment, a carrier material can be arranged inside the sensor, with the first electrode covering the carrier material, the ferroelectric layer covering the first electrode, and the second electrode covering the ferroelectric layer. Through the selection of the carrier material, the sensor can be configured and optimized to be more rigid or more flexible depending on the application. This embodiment can also be preferably formed in the shape of a cylinder or a plate. Furthermore, it is also possible to manufacture a sensor configured in this way in an endless process and therefore cheaply.

[0032] A sensor having a first electrode therein can have further first electrodes, second electrodes and ferroelectric layers, the first and second electrodes being radially alternating, with each ferroelectric layer being disposed between one of the first electrodes and one of the second electrodes, such that multiple functional ferroelectric layers can be arranged in sequence, thereby improving both the sensitivity and the accuracy of the sensor.

[0033] The coated and rolled sensors, with or without a carrier material, can have further first electrodes, second electrodes and ferroelectric layers, one ferroelectric layer each arranged between one of the first electrodes and one of the second electrodes, thus increasing the signal strength and thus the sensitivity and accuracy of the sensor, similar to stacked multi-layer members.

[0034] The carrier material for the coated or wrapped sensor can be, for example, a textile fiber. The sensor can be woven, for example, into clothing, covers or carpets. Artificial textile fibers, for example made of polyester, are particularly suitable for this use. However, natural fibers can also be used, provided that they can withstand the manufacturing process.

[0035] Furthermore, the carrier material can be glass fiber, which can be used to communicate the system state to the outside world through a color output or color change, for example whether direct contact of a sensor has occurred or there is an approaching heat source.

[0036] A part of the jacket surface of the glass fiber can be coated with an optically reactive sensor layer. This reactive layer can react to the pH value or O2 content in the environment, for example, by a color change. With the help of the glass fiber, this color change can be measured and the sensor can be extended to include a further sensory dimension. It is also possible to use fiber Bragg gratings as carrier material, which can increase the information output of the sensor.

[0037] It may be advantageous to form the sensor in a cylindrical shape. The sensor is thus radially symmetrical, and the measurement signal, for example generated by the deformation of the sensor, is direction-independent. It is also possible to form the sensor in a plate-like shape. In the case of a plate-like shape, the width and length can be at least ten times the height. This allows the manufacturing processes for flat layers to be used for the production of the sensor.

[0038] Furthermore, the sensor can have at least one mechanical amplification element. The mechanical amplification element can be, for example, a hair-like or bristle-like protrusion that transmits a mechanical contact to the sensor. In this way, the effective range of triggering the piezoelectric and capacitive effects by deformation can be increased. The mechanical amplification element can be made of a composite material or a plastic such as PET, a thermosetting resin or Teflon.

[0039] The mechanical amplification element can be formed from the first and / or second electrodes. The fabrication of the mechanical amplification element can be integrated into the manufacturing process of the electrodes, so that the sensor can be expanded to include the mechanical amplification element in an inexpensive and uncomplicated manner.

[0040] If the sensor has a carrier material, the at least one mechanical amplification element can also be formed from the carrier material. In particular in the case of cylindrical sensors, whether coated or wound, the internally arranged carrier material can protrude from the sensor and thus form the mechanical amplification element in a simple manner.

[0041] Alternatively, at least one mechanical amplifier element can be formed from the first electrode and the carrier material. This embodiment is also particularly suitable for cylindrical sensors. In this case, the carrier material and the electrodes arranged on the carrier material protrude from the sensor. Thus, the effective range of the piezoelectric effect as well as the effective range of the capacitive effect of the sensor is extended.

[0042] The individual layers of the sensor, i.e. the ferroelectric layer and the first and second electrodes, can each be thinner than 50 μm. By constructing the sensor extremely thin, it is flexible and can be bent, which is particularly advantageous in measurements based on the piezoelectric effect. The thin construction, especially of the pyroelectric layer, allows for a low thermal mass of the sensor, thus improving the response time and sensitivity of the sensor to temperature changes.

[0043] An advantageous arrangement may comprise a sensor and evaluation electronics as described above. The evaluation electronics may be configured to measure the voltage generated in the ferroelectric layer and to detect the voltage changes due to the piezoelectric, pyroelectric and capacitive effects. The evaluation electronics should be designed to classify the measurement signal into one or more physical effects based on the amplitude, time scale, time dynamics and polarity from the signal-time course. Based on the classification of the voltage changes into one or more physical effects, the evaluation electronics may detect whether an object is approaching the sensor or whether an object is in contact with the sensor.

[0044] In a further advantageous configuration, a number of sensors can be arranged in a matrix. By arranging the sensors in a matrix, measurements with spatial resolution can be performed and therefore movements can also be tracked. For example, planar sensors can be arranged on the substrate or cylindrical sensors can be arranged to protrude from the substrate, like a carpet.

[0045] Sensors can be integrated into robots. Robots, for example autonomous robots such as cleaning robots, lawnmower robots, delivery robots or transport robots, benefit from simplified sensors that can identify the approach to the robot. If the approach is registered by the sensor, the robot can act accordingly in such a way that it slows down, stops or avoids the obstacle.

[0046] A cooperative system with a sensor according to the invention also benefits from the possibility of recording approaches. In a cooperative system, a large number of interactions of machines with humans and with other machines occur with the risk of collision. A reliable detection of the environment by the sensor minimizes the risk of accidents and ensures safe work processes.

[0047] The sensor according to the invention can also be integrated into automatic doors, in particular automatic revolving doors or elevator doors: if the sensor detects the approach of a person, the door can be opened, the door can be prevented from closing, or the rotation speed of the revolving door can be slowed down to prevent collision or pinching of the approaching person.

[0048] A further aspect relates to a method for manufacturing a sensor as described above, wherein a ferroelectric layer is applied onto the first electrode by a thin film process, such as for example CVD or PVD, or a combination of sol-gel processing and spin-coating.

[0049] In the following, the invention is explained in detail on the basis of schematic illustrations. [Brief description of the drawings]

[0050] [Figure 1] 1 shows a schematic cross-sectional view of a first embodiment of the present invention. [Diagram 2] 1 shows a schematic arrangement with a sensor and evaluation electronics. [Diagram 3] 3 shows a further schematic arrangement with a sensor and evaluation electronics; [Figure 4] A diagram of the evaluation structure is shown. [Diagram 5]4 shows a schematic measurement curve of the sensor. [Figure 6] 4 shows a measurement curve of the voltage change due to the pyroelectric effect. [Figure 7] 4 shows a measurement curve of the voltage change due to the piezoelectric effect. [Figure 8] 4 shows a measurement curve of voltage change due to the capacitance effect. [Figure 9] 1 shows a schematic cross-sectional view of a multi-layer embodied sensor in which the electrical signal is amplified. [Figure 10] FIG. 2 shows a schematic cross-sectional view of a sensor embodied in multiple layers, where multiple individual electrical signals are read out. [Figure 11] FIG. 2 shows a schematic cross-sectional view of a plate-shaped coated embodiment in which the first electrode is arranged inside the sensor. [Figure 12] 1 shows a schematic cross-sectional view of a plate-shaped coated embodiment in which a carrier material is arranged inside the sensor. [Figure 13] 4 shows a schematic cross-sectional view of a further embodiment in which the amplifying element is arranged on the second electrode; [Figure 14] 2 shows a schematic cross-sectional view of a cylindrical embodiment in which an amplifying element is arranged on a carrier material and a first electrode. [Figure 15] FIG. 13 shows a schematic cross-sectional view of a fourth cylindrical embodiment in which an elongated carrier material acts as an amplifying element together with a first electrode. [Figure 16] 1 shows a schematic cross-sectional view of a cylindrical embodiment. [Figure 17] 1 shows a schematic cross-sectional view of a multi-layer cylindrical embodiment. [Figure 18] 1 shows a schematic cross-sectional view of a cylindrical embodiment in which an optically reactive layer is disposed on a carrier material. [Figure 19] FIG. 2 shows a schematic cross-sectional view of an embodiment having an insulating layer around which a sensor is wound. [Figure 20] FIG. 2 shows a schematic cross-sectional view of an embodiment with an insulating layer, in which the sensor is wrapped around a carrier material. [Figure 21] The robot is shown with possible sensor positions. [Figure 22] The cooperative system is shown with possible sensor locations. [Figure 23] An automatic revolving door is shown with possible sensor locations. [Figure 24] An automatic elevator door is shown with possible sensor locations. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0051] Identical, similar or obviously identical elements are provided with the same reference numbers in the figures. The figures and the size ratios therein are not to scale.

[0052] 1 shows a schematic cross-sectional view of a sensor 1 according to the invention. A ferroelectric layer 2 is arranged on a first electrode 3a, on which a second electrode 3b is arranged, which is electrically contacted and grounded.

[0053] The ferroelectric layer here can consist of a material which exhibits ferroelectric properties in an electric field. Preferably, the layer consists of a ferroelectric material with piezoelectric properties, particularly preferably of a ferroelectric material with pyroelectric properties.

[0054] The electrodes 3a, 3b are electrically contacted (not shown) and for example a voltage change between the electrodes 3a, 3b can be read out as a measurement signal. The pyroelectric layer 2, which is also piezoelectric, reacts to both temperature changes and deformations with a charge separation which results in a voltage change at the electrodes 3a, 3b. As the second electrode 3b is grounded, a voltage change between the electrodes 3a, 3b occurs in case of large proximity or contact as a result of a capacitance change between the second electrode 3b and the approaching object. The sensor 1 of the present invention exploits three different physical effects, namely the capacitive effect, the piezoelectric effect and the pyroelectric effect, to cover different detection areas.

[0055] Thanks to the pyroelectric effect, temperature changes can be detected depending on a heat source, which can be several meters away. The capacitive effect can also be used for contactless detection, but this requires that the object to be detected approaches the sensor 1 on a large scale, up to several centimeters. The piezoelectric effect and the capacitive effect can be used to check the contact of the sensor 1 with other objects. The piezoelectric effect is distinguished from the capacitive effect in that for a voltage change at the electrodes 3a, 3b, an active spatial deformation of the pyroelectric layer 2 must occur, whereas in the capacitive effect, already a static contact already leads to a voltage change.

[0056] The ferroelectric layer 2 comprises PVDF or PZT. Both materials are pyroelectric. PVDF is particularly suitable as a pyroelectric plastic, being elastic, since the ferroelectric layer 2 is easily deformed and thus a voltage change can be caused by the piezoelectric effect. The ferroelectric layer 2 made of PVDF can be applied, for example, by spin coating, screen printing or inkjet printing. In contrast, PZT is a pyroelectric ceramic that is flexible as a very thin layer. To adapt the electrical properties, it is possible to add Na, Ca or La to the PZT ceramic. PZT or other pyroelectric ceramics can be applied with the aid of thin film processes, for example CSD or PVD. PVDF has the advantage, compared to ceramics such as PZT, that it can be applied over larger areas without problems, since ceramics as layers over large areas can burst due to internal tensions and pressures.

[0057] Preferably, the first and second electrodes 3a, 3b consist of a transparent and electrically conductive material, such as, for example, ITO, PEDOT:PSS, silver, graphite, metal nanowires, carbon nanotubes or graphene. Materials that are transparent in the UV-Visible and / or IR range and / or exhibit good thermal conductivity are particularly suitable for the electrodes 3a, 3b. This facilitates the heat input to the ferroelectric layer 2, since the infrared thermal radiation directly impinges on the ferroelectric layer 2. Thus, the sensitivity of the sensor 1, in particular with regard to the pyroelectric effect, is increased. The electrodes 3a, 3b can also consist of metals, such as Al, Cr, Ni, Ag, Cu, mixtures of metals, intermetallic compounds or alloys. Metals are also suitable as electrode materials, since they have high electrical and thermal conductivity.

[0058] The layers of the sensor 1 are each less than 50 μm thick, which makes the entire sensor 1 flexible and bendable. The sensor 1 can therefore be easily deformed, which results in a voltage change between the first and second electrodes 3a, 3b due to the piezoelectric effect. Because the sensor 1 is extremely thin, it has a small thermal mass, which shortens the response time and increases the sensitivity of the sensor 1 to temperature changes.

[0059] The sensor 1 does not have to be composed of only one pyroelectric layer 2 as shown in Fig. 1, but can be realized as a multi-layer structure with multiple pyroelectric layers 2 and multiple first and second electrodes 3a, 3b. Here, the pyroelectric layer 2 is always disposed between the first and second electrodes 3a, 3b, and the first and second electrodes 3a, 3b are alternately disposed in the stacking direction. By realizing the sensor 1 as a multi-layer member, both the sensitivity and accuracy of the sensor 1 can be improved.

[0060] The measurement signal, which is picked up as a voltage change at the first and second electrodes 3a, 3b, is transferred to the evaluation electronics. The evaluation electronics 7 can here be arranged on the same carrier material 4 as the sensor 1, as shown in FIG. 2, or not on the same carrier material 4, as shown in FIG. 3. The evaluation electronics 7 is in contact with the sensor 1 directly or via the carrier material 4, as shown in FIG. 3. If a measurement event causes a voltage change at the sensor 1, this is transferred analogically to the evaluation electronics 7, as can be seen in FIG. 4. The evaluation electronics 7 comprises, among other things, a signal amplifier, a comparator and a microprocessor and is designed to classify the measurement curve into piezoelectric, pyroelectric or capacitive effects. The signal is then sent digitally to a digital evaluation unit 8, which again outputs an output signal.

[0061] In Fig. 5, examples of curves showing the voltage change after mechanical or thermal excitation of the sensor 1 are shown. In the graph of Fig. 5, the voltage is plotted against time, similarly to the graphs of Figs. 6, 7 and 8. In Fig. 6, the voltage change due purely to the pyroelectric effect is shown: at site Y1 the heat source is switched on and at site Y2 it is switched off again. In Fig. 7, a measurement curve resulting only from the piezoelectric effect is shown: at site X1 a deformation is caused by the application of pressure and at site X2 the pressure application is removed again. The measurement curve of Fig. 8 shows the voltage change at the sensor 1, which is due exclusively to the capacitive effect.

[0062] The deflection of the measurement curve due to the pyroelectric effect is slower than that due to the piezoelectric or capacitive effects, as shown for example by a comparison of Fig. 6 with Figs. 7 and 8. Furthermore, as can be seen in Fig. 6, the progression of the curve in the case of the pyroelectric effect may have a discontinuity when the heat source acts on the sensor 1 (Y1) or when it is subsequently switched off or blocked (Y2). In this case, switching off the heat source acts as a negative temperature difference, which changes the polarity and causes the measurement curve to abruptly change its sign.

[0063] In the case of the piezoelectric effect, a change of sign may also occur in the measurement curve, as shown in Fig. 7, for example when the sensor 1 is pre-deformed (X1) and then released (X2). In contrast to the pyroelectric effect, however, the progression of the curve is continuous and can be much faster. The amplitude or voltage change is typically 10 to 100 times smaller in the case of the pyroelectric effect than in the case of the piezoelectric effect, but this is not evident in the comparison of Fig. 6 with Fig. 7, since the curves are correspondingly pre-amplified.

[0064] On the other hand, capacitive effects may not cause a change of sign in the measurement curve and the deflection may be faster in time than the deflection due to the piezoelectric effect, as can be seen in FIG. 8. The two measurement curves in FIG. 8 were recorded with a sensor 1 in which the second electrode 3b is grounded in one case and not grounded in the other case. Since no voltage change occurs in the measurement curve without the ground connection of the second electrode 3b, it can be confirmed that the voltage change must come solely from the capacitive effect and not from the piezoelectric effect, which would result in a voltage change regardless of the ground connection of the second electrode 3b. Through the analysis of the measurement curves for these different characteristics, the evaluation electronics 7 can make a classification into physical effects.

[0065] If the sensor 1 is present as a multi-layer component as shown in Fig. 9, all first electrodes 3a can be electrically contacted with the same first electrical contact element and all second electrodes with the same second electrical contact element. The individual first and second electrodes are thus connected in parallel. This allows the electrical signals S of the individual functional layers, in the sense of signal summation, the amplified electrical signal S1, to be used for evaluation.

[0066] In an alternative embodiment, the individual functional layers are contacted separately, as shown in Fig. 10. In this case, the first electrodes are electrically contacted with respective separate first contact elements and the second electrodes with respective separate second contact elements. This allows evaluating separate electrical signals (S1, S2, S3, S4) for each functional layer, and further allows picking up different types of sensor signals for the individual functional layers and distinguishing them according to physical effects.

[0067] In FIG. 11 a schematic cross-section of a plate-shaped coated embodiment is shown, in which a first electrode 3a is placed inside the sensor 1, a ferroelectric layer 2 covers the first electrode 3a and a second electrode covers the ferroelectric layer 2. Such a sensor 1 can be built up layer by layer with the help of a suitable manufacturing process for flat layers, for example screen printing. In this case, it can be advantageous to overprint the inner layer with a layer that is larger in terms of area in order to achieve the coating. However, when producing a coating, it can also be advantageous to first apply to one side of the inner layer the layer that is to be placed on it, then invert the part and apply the same type of layer on the other side. Before inversion, the applied layer is dried.

[0068] Figure 12 shows a schematic cross-section similar to Figure 11 of a plate-shaped coated embodiment of the sensor 1, in which the carrier material 4 is arranged inside the sensor. This embodiment can also be produced, as in Figure 11, using a manufacturing process for flat layers, the layers being applied one after the other or by inverting the part for each coating layer.

[0069] The carrier material 4 may be inelastic or elastic. An inelastic carrier material 4, such as a substrate, increases the stability of the sensor 1. For selected applications, an arrangement on a carrier material 4, which consists, for example, of glass, concrete or steel, may be preferred. Elastic materials that come into consideration as the carrier material 4 may be, inter alia, rubber, plastic or a woven material, such as, for example, cotton thread.

[0070] FIG. 13 shows a schematic cross-section of a sensor 1 similar to FIG. 1, which is arranged on a carrier material 4 and has a mechanical amplification element 5 on the second electrode 3b.

[0071] The mechanical amplification elements 5, shown as hair-like or bristle-like projections in Fig. 13, can mechanically transmit the contact to the second electrode 3b. As the ferroelectric layer 2 is fixed to the second electrode 3b, this contact is also transferred to the ferroelectric layer 2, which is thus deformed. This increases the detection area that can be covered by the piezoelectric effect. The mechanical amplification elements 5 consist either of a composite material or of a plastic such as PET, a thermosetting resin or Teflon.

[0072] The mechanical amplification element 5 can also be applied or formed on cylindrical sensors 1 and on sensors 1 that are not arranged on a carrier material 4. Preferably, the amplification element 5 is attached as an extension of the first electrode 3a and / or the carrier material 4 in the axial direction, as shown in FIG. 14. Preferably, the amplification element 5 is not applied additionally here, but rather no further ferroelectric layer 2 and no further second electrode 3b are applied on the first electrode 3a and the carrier material 4 in the area that is realized by the first electrode 3a and the carrier material 4 and serves as the amplification element 5. A cross-section of a sensor embodied in this way is shown in FIG. 15. For additional signal amplification, such cylindrical sensors 1 provided with amplification elements 5 can be bundled together, consisting of several individual sensors 1.

[0073] Alternatively, the amplification element 5 can also be formed only from the carrier material 4. In a cylindrical embodiment in which the carrier material 4 is arranged internally, the first electrode 3a is also omitted in the region of the amplification element 5. If the sensor 1 is arranged on a carrier material 4 having a size larger than the sensor 1 itself, the protruding part of the carrier material 4 also serves as the amplification element 5. In an embodiment in which the first electrode 3a is arranged internally rather than the carrier material 4, the amplification element 5 can also be formed only from the first electrode 3a. In that case, the first electrode 3a protrudes from the sensor 1 and the ferroelectric layer 2 and the second electrode 3b are omitted.

[0074] In Fig. 16, a schematic cross-section of a cylindrically embodied sensor 1 is shown. Inside, a first electrode 3a is arranged, which is covered by a pyroelectric layer 2. The ferroelectric layer 2 is covered by a second electrode 3b. The second electrode 3b is grounded, which is not shown in Fig. 16.

[0075] The first electrode 3a can be a commercially available wire. Preferably, the first electrode 3a is kept very thin with a diameter of about 150 μm to 250 μm in order to reduce the thermal mass of the sensor 1. The ferroelectric layer 2 is embodied with a thickness of less than 5 μm for the same reason. In the case of the second, in this embodiment the outermost electrode, a balance must be struck in the choice of layer thickness between the sensitivity of the sensor 1 and the protection of the pyroelectric layer 2. In practice a thickness of about 10 μm has been found to be an advantageous compromise.

[0076] The cylindrical shape of the sensor 1 is particularly advantageous for applications where the sensor 1 must be inserted into a narrow opening. Furthermore, the cylindrical shape of the sensor 1 is beneficial for increasing sensitivity to deformation. Furthermore, the cylindrical embodiment allows the sensor 1 to be manufactured in an endless process, similar to the manufacturing of a wire or cable. This simplifies manufacturing and reduces manufacturing costs.

[0077] FIG. 17 shows a schematic cross-section of the sensor 1, which is embodied cylindrically, as in FIG. 14. Inside, a carrier material 4 is arranged. Two first and second electrodes 3a, 3b, respectively, alternately cover the carrier material 4, and one ferroelectric layer 2, respectively, is arranged between the first and second electrodes 3a, 3b. The inner layers of the sensor 1 are also thinner than 5 μm in this embodiment. The thickness of the second electrode 3b, which forms the outermost layer, is preferably 10 μm. The use of several pyroelectric layers 2 increases the accuracy of the sensor 1 compared to the embodiment with one pyroelectric layer 2.

[0078] The carrier material 4 can be, for example, textile fibers, glass fibers or fiber Bragg gratings. If textile fibers are used as the carrier material 4, they can be woven into clothing, covers, carpets and other textile products. Textile fibers made of plastics such as polyester are outstandingly suitable as the carrier material 4. Natural fibers made of, for example, cotton can also be used. Glass fibers as the carrier material 4 can be used to indicate the system state, for example whether direct contact or proximity has occurred, by transmitting light of a certain color through the glass fibers. It is also possible to use fiber Bragg gratings as the carrier material 4. These can extend the sensor technology, for example by being used as force sensors. It should be noted, however, that for this a further optical evaluation set-up is required.

[0079] In FIG. 18, a longitudinal section of the cylindrically embodied sensor 1 is shown. Inside, a glass fiber covered by first and second electrodes 3a, 3b is arranged, and a ferroelectric layer 2 is arranged between the first and second electrodes 3a, 3b. On a part of the outer surface of the glass fiber, the first and second electrodes 3a, 3b and the ferroelectric layer 2 are not applied, but instead an optically reactive sensor layer 6 is applied. This optically reactive layer 6 can react to the pH value or the O2 content in the environment, for example, by a color change or a change in fluorescence. With the help of evanescent light waves emerging from the glass fiber, this color change can be measured. In this way, the potential application fields for the sensor technology and the sensor 1 can be expanded.

[0080] 19 shows a schematic cross-section of an embodiment with an insulating layer 9, where the sensor 1 is rolled with the insulating layer 9 on the inside. The insulating layer is an electrically insulating flexible layer, which may also consist of a flexible and thin carrier material 4. The insulating layer 9 prevents the first and second electrodes 3a / 3b from shorting out when rolled.

[0081] The rolled embodiment allows for the manufacture of a cylindrical sensor 1 by planar manufacturing processes. It should be noted that by rolling the sensor 1 multiple times, a multi-layer member can be manufactured, in which radially successive electrodes are not electrically isolated from each other as in the case of the coated sensor 1, but connected to each other. The rolled sensor 1 therefore has an increased capacitance compared to the coated sensor 1, and the capacitive effect is more pronounced.

[0082] In Fig. 20, similarly to Fig. 19, a schematic cross-section of an embodiment with an insulating layer 9 is shown, in which the sensor 1 is wound around a carrier material 4. With the help of the carrier material 4 the mechanical properties of the wound sensor 1 can be influenced.

[0083] A combination of the different embodiments is also possible: thus, for example, the coated sensor 1 can serve as a carrier material 4, and a further sensor is wound around the coated sensor 1. Thus, the significant capacitive effect of the wound sensor 1 can be combined with the advantages of the coated sensor 1.

[0084] All embodiments may further comprise a protective layer, for example made of plastic, to protect the sensor 1 from harmful environments.

[0085] In FIG. 21 an autonomous transport robot for a general robot is shown by way of example. The box in the lower area of ​​the robot shows an advantageous position for mounting the sensor 1 according to the invention. If the robot approaches, for example, a human, at a distance of a few meters a voltage change due to the pyroelectric effect of the electrodes 3a, 3b of the sensor 1 is observed, as a result of which the robot can, for example, slow down its speed. If the robot approaches the human further, from a distance of about one meter a voltage change caused by the capacitive effect is observed. The robot would be able to change its direction of movement at this point, since it is approaching the human. If the robot nevertheless collides with the human, the sensor 1 is deformed and a voltage change is detected as a result of the piezoelectric effect. The robot would now be able to stop or turn back in order not to cause damage. If the robot stops, and thus the deformation of the ferroelectric layer does not change, the voltage change due to the piezoelectric effect disappears. Nevertheless, the contact can still be detected by the capacitive effect.

[0086] FIG. 22 shows a cooperative system in which a sensor 1 according to the invention is integrated. In particular, the end of a robot arm, which may be particularly close to the collaborating human being, is suitable for positioning the sensor 1. In FIGS. 23 and 24 an advantageous position of the sensor 1 on an automatic door is shown. An automatic revolving door could for example slow down its rotation speed in case of approach and increase it again in case of contact of the sensor 1. An automatic elevator door as shown in FIG. 24 could for example already keep the door open in case of approach of a human being. As a result, an increase in safety can be achieved in comparison with the frequently used light barriers, since the sensor can already detect the approach of a human being to the door and does not only react when this human being is already inside the door. [Explanation of symbols]

[0087] 1 Sensor 2 Ferroelectric layer 3a First electrode 3b Second electrode 4. Carrier Materials 5. Mechanical Amplification 6 Optically responsive layer 7. Evaluation Electronic Devices 8 Digital Evaluation Section 9 Insulating Layer S signal

Claims

1. A sensor (1), a first electrode (3a), Ferroelectric layer (2), a second electrode (3b), having the second electrode (3b) is grounded, and the ferroelectric layer (2) is disposed between the first electrode (3a) and the second electrode (3b); the sensor (1) comprises a carrier material (4) and at least one mechanical amplifier element (5), the amplifier element (5) being mounted as an axial extension of the first electrode (3a) and / or the carrier material (4), The sensor (1) is arranged on the carrier material (4) and has a number of amplification elements (5) on the second electrode (3b).

2. The sensor (1) according to claim 1, wherein the ferroelectric layer (2) comprises a polymer, a ceramic or a polymer-ceramic matrix.

3. The sensor (1) according to claim 1 or 2, wherein the first electrode (3a) and / or the second electrode (3b) comprise a transparent, thermally and electrically conductive material.

4. The sensor (1) according to any one of claims 1 to 3, wherein the first electrode (3a) and / or the second electrode (3b) comprises a metal or metals, the metal or metals comprising Al, Cr, Ni, Ag, Cu, Fe, and mixtures or alloys of these elements.

5. The sensor (1) according to any one of claims 1 to 4, wherein the first electrode (3a) and / or the second electrode (3b) comprise a conductive layer transparent in the UV-Visible and / or IR range.

6. The sensor (1) according to any one of claims 1 to 5, wherein the first electrode (3a) and / or the second electrode (3b) comprise ITO, PEDOT:PSS, silver, nanowires, graphite, carbon nanotubes or graphene.

7. The sensor (1) according to any one of claims 1 to 6, wherein the sensor (1) comprises a further first electrode (3a), a second electrode (3b) and a ferroelectric layer (2), the ferroelectric layer (2) being arranged between the first electrode (3a) and the second electrode (3b).

8. all the first electrodes (3a) are connected in parallel to one another and all the second electrodes (3b) are connected in parallel to one another; The sensor (1) according to claim 7, wherein an electrical signal (S) is read between the first electrode and the second electrode.

9. 8. The sensor (1) according to claim 7, wherein the individual ferroelectric layers (2) are contacted separately and an electrical signal is read out for each of the ferroelectric layers (2) between one of the first electrodes (3a) and one of the second electrodes (3b), respectively.

10. The sensor (1) according to any one of claims 1 to 9, wherein the first electrode (3a) is arranged inside the sensor (1), the ferroelectric layer (2) covers the first electrode (3a), and the second electrode (3b) covers the ferroelectric layer (2).

11. The sensor (1) comprises an insulating layer (9) on which the first electrode (3a) or the second electrode (3b) is arranged, The sensor (1) according to any one of the preceding claims, wherein the sensor (1) is wound so that the insulating layer (9) is located on the inside.

12. The sensor (1) according to any one of the preceding claims, wherein the first electrode (3a) or the second electrode (3b) is arranged on the carrier material (4).

13. The sensor (1) comprises an insulating layer (9) on which the first electrode (3a) or the second electrode (3b) is arranged, The sensor (1) according to any one of the preceding claims, wherein the sensor (1) is rolled such that the insulating layer (9) is arranged on top of the carrier material (4).

14. The sensor (1) according to any one of claims 1 to 13, wherein the carrier material (4) is arranged inside the sensor (1), the first electrode (3a) covers the carrier material (4), the ferroelectric layer (2) covers the first electrode (3a), and the second electrode (3b) covers the ferroelectric layer (2).

15. a further first electrode (3a) and second electrode (3b) and a further ferroelectric layer (2) covering said second electrode (3b), The first electrodes (3a) and the second electrodes (3b) are alternately arranged in the radial direction, 15. The sensor (1) according to claim 10 or 14, wherein one of the ferroelectric layers (2) is arranged between one of the first electrodes (3a) and one of the second electrodes (3b).

16. The sensor (1) according to any one of the preceding claims, wherein the carrier material (4) is a textile fibre or a glass fibre.

17. 17. The sensor (1) according to claim 16, wherein a part of the surface of the fibreglass jacket is coated with an optically responsive sensor layer (6).

18. The sensor (1) according to any one of the preceding claims, wherein the sensor (1) is cylindrically shaped or the sensor (1) is plate-shaped.

19. The sensor (1) according to any one of the preceding claims, wherein the at least one mechanical amplification element (5) is formed from the first electrode (3a).

20. The sensor (1) according to any one of the preceding claims, wherein the at least one mechanical amplification element (5) is formed from the carrier material (4).

21. The sensor (1) according to any one of the preceding claims, wherein the at least one mechanical amplification element (5) is formed from the first electrode (3a) and the carrier material (4).

22. The sensor (1) according to any one of the preceding claims, wherein the ferroelectric layer (2) and / or the first electrode (3a) and / or the second electrode (3b) are thinner than 50 μm.

23. The sensor (1) according to any one of the preceding claims, wherein the ferroelectric layer (2) comprises a piezoelectric or pyroelectric material.

24. at least one evaluation electronic device (7), A sensor (1) according to any one of claims 1 to 23, An apparatus having The evaluation electronics (7) is configured to measure the electrical signal (S) generated by the sensor (1) and to recognise the piezoelectric, pyroelectric and capacitive effects through variations in the electrical signal (S).

25. 25. The device according to claim 24, wherein the evaluation electronics (7) is configured to recognize, based on a change in the measured electrical signal, whether an object is approaching or in contact with the sensor (1).

26. Apparatus according to claim 24 or 25, wherein the changes in the measured electrical signal (S) comprise changes in the signal-time course and / or amplitude and / or time scale and / or time dynamics and / or polarity.

27. Apparatus according to any one of claims 24 to 26, wherein the electrical signal (S) comprises a voltage and / or a charge and / or a capacitance and / or a polarity.

28. A plurality of sensors (1) according to any one of claims 1 to 22, Including, The sensors (1) are arranged in a matrix. Apparatus according to any one of claims 24 to 27.

29. A robot comprising a sensor (1) according to any one of the preceding claims.

30. A cooperative system comprising a sensor (1) according to any one of the preceding claims.

31. An automatic door comprising a sensor (1) according to any one of the preceding claims.

32. A method for manufacturing a sensor according to any one of claims 1 to 23, wherein the ferroelectric layer (2) is applied onto the first electrode (3a) by a thin film process, by a combination of a sol-gel process and spin-coating, or by screen printing.

33. The sensor (1) according to any one of the preceding claims, wherein the mechanical amplification elements (5) are hair-like or bristle-like projections.

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