WO2013110481A2

WO2013110481A2 - Arrangement for generating and/or detecting ultrasonic waves and method for producing an arrangement for generating and/or detecting ultrasonic waves

Info

Publication number: WO2013110481A2
Application number: PCT/EP2013/050049
Authority: WO
Inventors: Michael Seiter; Andre Gerlach
Original assignee: Robert Bosch Gmbh
Priority date: 2012-01-25
Filing date: 2013-01-03
Publication date: 2013-08-01
Also published as: WO2013110481A3; DE102012201055A1

Abstract

The invention relates to an arrangement (1) for generating and/or detecting ultrasonic waves, comprising a piezoelectric layer (2) having a first side and a second side, at least one electrically conductive element (5, 6, 7) being arranged on the first side and opposite on the second side, a protective layer (10) comprising graphene being formed on the first side on the side of the electrically conductive element (5) opposite the piezoelectric layer (2). Said type of arrangement (1) is particularly stable and can work in a particularly secure and reliable manner. Said invention also relates to the use of said type of arrangement (1) and to a method for producing said type of arrangement.

Description

description

title

Arrangement for generating and / or detecting ultrasonic waves and method for producing an arrangement for generating and / or detecting ultrasonic waves

The present invention relates to an apparatus for generating and / or detecting ultrasonic waves. The present invention further relates to a method for producing an apparatus for generating and / or detecting ultrasonic waves.

State of the art

Ultrasonic transducers are nowadays used and needed in a wide range of applications. For example, in ultrasound-based environmental sensing, ultrasonic transducers typically emit ultrasonic waves, particularly in a range above the audio frequency range, to the ambient air. The sound waves are from objects at a distance of, for example, 10 meters

backscattered and registered by a sound receiver, so as to be able to detect obstacles, for example.

The document US 7,995,777 B2 describes a sound transducer, as

Speaker is used. The sound transducer comprises an example piezoelectric and transparent thin film, which is arranged between two electrically conductive thin films. The piezoelectric thin film may, for example, be made of polyvinylidene fluoride (PVDF), whereas the electrically conductive thin films disposed on the piezoelectric thin film may be constructed of carbon nanotubes, carbon nanofibers, graphene or combinations thereof. DISCLOSURE OF THE INVENTION The invention relates to an arrangement for producing and / or

Detecting ultrasonic waves comprising a piezoelectric layer having a first side and a second side, wherein at least one electrically conductive element is disposed on the first side and opposite on the second side, respectively, and on the first side on the opposite side of the piezoelectric layer of the electrically conductive

Element is a protective layer comprising graphene is formed.

In the sense of the present invention, ultrasonic waves may in particular be waves which have a frequency which lies above the range audible to humans. For example, ultrasonic waves can

Frequency of more than 16 kHz. In this case, the term ultrasonic waves can also include waves which have a frequency of about 1 GHz and thus can be referred to as hypersonic waves. For the purposes of the present invention, a piezoelectric layer can be understood in particular to mean a layer or any element of suitable shape which has piezoelectric properties and can thus undergo a change in size or a change in geometry, for example, by the action of a voltage, such as an alternating voltage. Furthermore, a piezoelectric layer may have the property that it can induce a voltage such as by a change in size and / or a change in shape.

In the context of the invention, an electrically conductive element can furthermore be understood in particular to be an electrode which has an electrical

Having conductivity sufficient to activate the piezoelectric layer, so by generating an electrical voltage and acting on the latter in the piezoelectric layer in this a molding and / or

To generate geometry change, or to absorb induced voltage from the piezoelectric layer. The electrically conductive element may be present, for example, in the form of a layer. For the purposes of the present invention, graphene can be understood in particular to be a carbon modification, which may in particular have a two-dimensional structure. In this structure, each of the carbon atoms may be surrounded by three other carbon atoms, whereby a structure formed as a honeycomb-shaped pattern may be formed. By localized double bonds, this structure can also be described as a two-dimensional chain of benzene molecules. At the outer end of the structure, for example, other groups of atoms may be arranged. These can, however, regarding the properties of the

Total material negligible. A graphene-comprising layer can furthermore be any layer which is completely formed from graphene or at least partially comprises graphene.

The present arrangement may thus be particularly suitable for generating ultrasonic waves starting from a voltage applied to the electrically conductive elements by activation of the piezoelectric layer. For this purpose, the electrically conductive elements are arranged opposite one another on different sides of the piezoelectric layer. Consequently, they are arranged so that they can activate the piezoelectric layer and at least partially overlap, for example, in a plan view. The present arrangement may further be adapted to detect ultrasonic waves by ultrasonic wave induced deformation of the piezoelectric layer and thereby by a voltage induced in the electrically conductive elements, the ultrasonic waves. The present arrangement can thus be referred to as ultrasonic transducer. Such devices have a very large application potential. For example, such

Arrangements or ultrasound transducers are used for ultrasound-based environment sensing, as can be used, for example, in connection with motor vehicles, moving machines such as robots, or even to assist visually impaired people. In this case, the ultrasonic transducers can be used in particular to prevent collisions with environmental objects and environmental maps for

To determine path planning. Such arrangements for generating and / or detecting ultrasonic waves may also be used with others

Sensing technologies, such as combined with video systems, so that complement the technologies and the detection performance of the

Overall system can be further improved.

A generation of ultrasonic waves can be realized by activating the piezoelectric layer, in particular by applying a voltage, such as an alternating voltage, to the electrically conductive elements. By an action of the electrical voltage on the piezoelectric layer arranged between the electrically conductive elements, the latter can undergo a change in shape and / or geometry. Through this

Change that can take place as a function of the frequency of the alternating voltage, ultrasonic waves can be generated, the frequency of which may be dependent on the frequency of the alternating voltage applied, for example.

Accordingly, ultrasonic waves can be detected by causing a change in shape and / or geometry of the piezoelectric layer, whereby an electric voltage can be generated at the piezoelectric layer, which is detectable by the electrically conductive elements.

Characterized in that on the first side on the opposite side of the piezoelectric layer of the electrically conductive element, a protective layer comprising graphene is formed, the robustness or resistance of the ultrasonic transducer against environmental effects such as in particular against mechanical effects can be improved.

Consequently, the graphene-comprising layer can serve in particular as a protective layer, which can protect the electrically conductive elements and the piezoelectric layer from external influences. This can be made possible in particular by the outstanding properties of graphene. In detail, graphene can have a particularly high hardness, which can be comparable to that of diamond. In addition, graphene surface crystals within the surfaces are extremely stiff and strong. The modulus of elasticity may correspond to that of diamond at about 1200GPa. The tensile strength of about 1, 25x10 ¹¹ can be about 125 times higher than steel.

Consequently, by means of a graphene-comprising protective layer, the arrangement can operate in a particularly reliable and reliable manner, whereby the susceptibility to interference can be reduced, which permits particularly cost-effective operation. By means of a graphene-comprising layer as a protective layer, small demands can be made with regard to the robustness of the electrically conductive elements or of the piezoelectric layer. As a result, the electrically conductive elements and the piezoelectric layer can be tailored with respect to their actual field of use.

In this case, the robustness of the protective layer and thus of the entire arrangement, which is improved by a graphene-comprising layer, can be of particular advantage in applications which are exposed to strong environmental influences, for example when used as a parking sensor in bumpers of motor vehicles. The first page of the

piezoelectric layer in particular be the side into which the

Ultrasonic waves can be sent, so can be referred to as a functional side, whereas the arrangement on the second side of the piezoelectric

Layer can be arranged for example on a substrate.

Basically, a graphene-comprising layer alone can be sufficient in the use of only one protective layer alone, ie in particular no plurality of different layers with their minimum thicknesses and possible adhesive layers may be necessary.

As a result, an arrangement for generating ultrasonic waves can furthermore be produced in a particularly simple and cost-effective manner. The use of a reduced number of protective layers has the further advantage that, due to a smaller number of layers, even less material improves the transmission and reception strength of the

may be given piezoelectric layer or the arrangement. In addition, a graphene-containing layer can be improved compared with other useful protective layers in a previously described

Robustness significantly reduce or influence the transmission strength or reception strength of the arrangement compared to other comparably robust protective layers. For example, graphene, due to its comparatively low weight per unit area, offers the advantage of only a slight vibration mechanical impairment of the piezoelectric layer. As a result, a high reception and transmission strength can be achieved and also only a low maintenance requirement may be necessary.

In addition, when using a graphene-containing layer as a protective layer, an EMC protection, ie a protection against electromagnetic

There may be scattering or influencing, which can be pronounced by the good conductivity of the graphene.

As a further advantage, it can be mentioned that graphene can be selectively applied in a particularly simple manner, which allows the generation of a defined structure.

Thus, a prescribed arrangement for generating

Ultrasonic waves not only be particularly robust, but also be particularly powerful.

Within the scope of an embodiment, the piezoelectric layer may comprise a ferroelectric layer or may at least partially be formed in particular completely from it. In this case, it is particularly preferred if the ferroelectric layer comprises a ferroelectret material or at least partially, in particular, is completely formed therefrom. Such layers can be characterized in particular by a great robustness and cost-effective production. From such materials can be produced in various designs, such as a so-called array arrangement, particularly cost piezoelectric layers. These layers can, for example, be designed or produced as in particular flexible films and also be referred to as cellular films or as an electromechanical film (EM Fl) transducer. Ferroelectret layers can be used in the context of the present invention

in particular be such, which may have a pore structure, at the interface electrostatically positive and negative charges can be located and permanently stored. Furthermore, an electric dipole moment can be present and this can change the direction of the spontaneous polarization by the application of an external electric field, that is to say by an applied voltage to the electrically conductive elements. In particular, all non-conductive ferroelectric materials may also be piezoelectric. Suitable ferroelectret materials include, for example, polymers such as polytetrafluoroethylene, polytetrafluoroethylene-propylene, polyethylene terephthalate, polyvinylidene fluoride or copolymer of one or more of the foregoing polymers.

In a further embodiment, the piezoelectric

Protective layer have a thickness in a range of> 50 μηι to <500 μηι. Piezoelectric layers with such thicknesses are inexpensive to produce and also provide a change in shape sufficient transmit power and receiving strength of the generated ultrasonic waves. In addition, piezoelectric layers of this thickness provide suitable stability.

In a further embodiment, the graphene-comprising layer may have a thickness in a range of <300 μm. In this embodiment, the vibration mechanical impairment of the piezoelectric layer can be kept very low by a small thickness, which the

Efficiency in terms of transmission and reception strength thus keeps large. In this embodiment, despite the small thickness, a great robustness against external influences can be given. Because such thicknesses are sufficient by the very great robustness of the graphene to a sufficient

Stability and thus to realize a sufficient protection of the electrically conductive elements or the piezoelectric layer.

In the context of a further embodiment, at least one further protective layer may be arranged on the side of the graphene-comprising protective layer opposite the electrically conductive elements. In this embodiment, the protection of the arrangement can be further improved. In addition, the graphene-containing layer itself can be protected, so that, for example, chipping or exposure of unwanted substances to the graphene can be prevented. Furthermore, the graphene-comprising layer can be protected, in particular, against effects such as moisture, dirt or light. By way of example, suitable further protective layers may comprise parylene or polyimide, such as Kapton, or may be formed at least partially from these materials, for example completely. Parylene, for example, are hydrophobic and chemically resistant

Plastics that have a good barrier effect, for example inorganic and organic media, strong acids, alkalis, gases and water vapor may have. In addition, parylene provide a good electrical insulation capability. Kapton is available under its trade name from DuPont, which is a polyimide. This can be particularly good heat resistance and

Have radiation resistance. In this embodiment, the thickness of all provided protective layers in a range of <300 μηι lie.

In a further embodiment, the arrangement may comprise a plurality of individual transmitters and / or individual receivers. In this embodiment, the advantage of extended signal processing can be achieved.

In particular, it may be possible in this embodiment, the direction and distance to determine several objects simultaneously. This arrangement can therefore be used particularly advantageously in environmental sensing in complex environments with multiple objects. In order to achieve a particularly high performance, the arrangement may comprise five or more individual transmitters and / or individual receivers, for example in the number of ten to thirty. In this case, an arrangement in this embodiment may be referred to as a so-called array arrangement in particular if the distance from two or more individual transmitters or

Individual recipients each less than half

Air scarf wavelength is. The compliance with these distances can be much simpler possible by the arrangement according to the invention, as it is possible according to the prior art, such as mechanical resonance transducers. In this context, a single transmitter or a single receiver can be understood in particular as a combination of a piezoelectric layer and in each case an electrically conductive element on the first and second side, in which at least one of the piezoelectric layer and / or at least one electrically conductive element of the respective

corresponding component of the adjacent receiver and / or transmitter is separated in particular electrically insulating.

The invention further relates to a use of an inventive arrangement for generating and / or detecting ultrasonic waves for environment sensing or wireless communication. In this

Embodiment may be through the use of an inventive arrangement An environment sensing be carried out particularly safe and reliable, since the arrangement is particularly robust and stable against external influences. An environmental sensation can in particular be an examination of the

Surroundings with respect to existing objects include. The environment sensing can serve to prevent collisions with objects and / or to create an environment map, for example, a path planning

perform. An environment sensing can be used, for example, in driver assistance systems in motor vehicles such as in

Parking systems, in a maneuver support, or when monitoring the blind spot. Furthermore, an application to robots, such as

Vacuum cleaners, lawn mowers or transport robots, approximately in one

Production plant, or be suitable in hospitals or nursing homes. Further exemplary applications include the monitoring of manufacturing processes, the support of visually impaired people, such as obstacle detectors, ultrasonic shock devices or a so-called ultrasonic guide dog. Finally, an application in the

Safety technology be advantageous, especially in space monitoring, the location of invading people or objects. As a further exemplary application, the ultrasonic communication may be in the air, for example, in a remote control or the communication between moving vehicles or machines offer.

With regard to further advantages, reference is made to the above statements regarding the arrangement according to the invention.

The invention further provides a method for producing an arrangement according to the invention for generating and / or detecting

Ultrasonic waves comprising the process steps:

a) providing a piezoelectric layer having a first side and a second side;

b) arranging at least one electrically conductive element on the

first side of the piezoelectric layer;

c) arranging at least one electrically conductive element on the

second side of the piezoelectric layer; and d) arranging a graphene-comprising protective layer on the first side of the piezoelectric layer on the side of the electrically conductive element opposite the piezoelectric layer. With the method according to the invention, an arrangement for generating and / or detecting ultrasonic waves can be produced, which has a particularly high robustness or stability against external influences and thereby operates particularly safely and reliably.

In principle, the process steps may be in any desired

Order to be performed. Further, placing one component on another component may mean applying each of the components to one another. However, in an exemplary embodiment, the arrangement may be made as follows. First, the piezoelectric layer, which may be a ferroelectric layer, is provided. At least one electrically conductive element can then be applied to its first side. This element can, for example, constitute a layer and be applied as a metallization, for example. In principle, metals, such as aluminum or copper, and electrically conductive polymers, such as, for example, poly (3,4-ethylenedioxythiophene) poly (styrenesulfonate (PEDOT: PSS) can be used as electrically conductive elements, examples described above not being intended to be limiting Methods for arranging the electrically conductive element are, for example

Sputtering or printing, for example by screen printing or flexographic printing, suitable. This electrically conductive element can then have the function of a ground electrode. In the following, at least one graphene-comprising protective layer can be applied to the electrically conductive element on the first side of the piezoelectric layer. Furthermore, further protective layers can be applied to the graphene-comprising protective layer; with respect to the second side of the piezoelectric layer, at least one, in particular a plurality of spatially separated, electrically conductive elements can likewise be applied here. For example, the

piezoelectric layer are glued together with the disposed on the second side electrically conductive elements on a substrate, wherein the adhesive, the electrically conductive elements of each other can be spatially separated and electrically isolated. With regard to further advantages, reference is made to the above statements regarding the arrangement according to the invention. In an embodiment, the graphene-comprising protective layer can be arranged by epitaxial growth on the first side of the piezoelectric layer on the side of the electrically conductive element opposite the piezoelectric layer. In this embodiment, the graphene-comprising protective layer can be applied particularly well controllable, whereby defined properties can be generated. In addition, such a method can produce a graphene structure which is particularly robust against external influences. In this context, epitaxial growth can be understood in particular to mean a process in which graphene is formed or arranged in an orderly manner on a surface of, for example, another material. As a non-limiting example, a method is mentioned here in which, with heating, carbon dissolves in a metal, that is, for example, in the electrically conductive element, emerges again on cooling and subsequently arranges as graphene on the surface.

Drawings and examples

Further advantages and advantageous embodiments of the objects according to the invention are illustrated by the drawing and explained in the following description. It should be noted that the

Drawing has only descriptive character and is not intended to limit the invention in any way. 1 shows a schematic sectional view of an embodiment of a

inventive arrangement.

FIG. 1 shows an embodiment of an arrangement 1 for generating and / or detecting ultrasonic waves. Such an arrangement 1 can be used, for example, in environmental sensing or wireless communication. The arrangement 1 comprises a piezoelectric layer 2, such as a ferroelectric layer or a ferroelectret-comprising

Layer, with a first page and a second page. In Figure 1, the pore-shaped structure of the ferroelectret-comprising layer is as

piezoelectric layer 2, which has a matrix 3 made of a ferroelectret material and pores 4 present in the matrix. The piezoelectric layer may have a thickness in a range of> 50 [im to <500 [im.

At least one electrically conductive element 5, 6, 7 is arranged on the first side and opposite on the second side. For example, an electrically conductive element 5 designed as a layer may be provided on the first side, whereas on the second side a plurality of electrically conductive elements 6, 7 are arranged, which may be formed as conductor tracks and form a transducer electrode. In this case, the arranged on different sides electrically conductive elements 5 can be arranged relationship meadow 6 and 7 opposite one another. Furthermore, the elements 6, 7 arranged on one side can be spatially separated from one another and electrically insulated from each other, so that the arrangement 1 comprises a plurality of individual transmitters 8, 9, which likewise can serve as individual receivers. Thus, the individual transmitters 8, 9 or the individual receiver can be referred to as individual transducer elements.

FIG. 1 furthermore shows that a protective layer 10 comprising graphene is formed on the first side on the side of the electrically conductive element 5 opposite the piezoelectric layer 2. The graphene-comprising protective layer 10 may have a thickness in the range of <300 μm. Furthermore, at least one further protective layer 11, for example comprising parylene or kapton, may be arranged on the side of the graphene-comprising protective layer 10 opposite the electrically conductive elements 5, 6, 7.

In addition, the piezoelectric layer 2 can be arranged together with the electrically conductive elements 6, 7 on a substrate 12, for example by an adhesive 13 bonded thereto. It can, for example, the Adhesive 13, the electrically conductive elements 6, 7 spatially separate from each other and electrically isolated from each other.

A method for producing an arrangement according to the invention for generating and / or detecting ultrasonic waves may in particular comprise the following method steps:

a) providing a piezoelectric layer 2 having a first side and a second side;

b) arranging at least one electrically conductive element 5 on the first side of the piezoelectric layer 2;

c) arranging at least one electrically conductive element 6, 7 on the second side of the piezoelectric layer 2; and

d) arranging a graphene-comprising protective layer 10 on the first side of the piezoelectric layer 2 on the opposite side of the piezoelectric layer 2 of the electrically conductive element 5, in particular by epitaxial growth.

Claims

claims

Arrangement for generating and / or detecting ultrasonic waves, comprising a piezoelectric layer (2) having a first side and a second side, wherein at least one electrically conductive element (5, 6, 7) is arranged on the first side and opposite on the second side. is arranged, and wherein on the first side on the piezoelectric layer (2) opposite side of the electrically conductive member (5), a protective layer (10) comprising graphene is formed.

Arrangement according to claim 1, wherein the piezoelectric layer (2) comprises a ferroelectric layer.

Arrangement according to one of claims 1 or 2, wherein the piezoelectric layer (2) has a thickness in a range of> 50 μηι to <500 μηι.

Arrangement according to one of claims 1 to 3, wherein the Graphenumfassende protective layer (10) has a thickness in a range of <300 μηι.

Arrangement according to one of claims 1 to 4, wherein on the said electrically conductive elements (5, 6, 7) opposite side of the Graphenumfassenden protective layer (10) at least one further protective layer (11) is arranged.

Arrangement according to claim 5, wherein the further protective layer (11) comprises parylene and / or polyimides.

Arrangement according to one of claims 1 to 6, wherein the arrangement (1) comprises a plurality of individual transmitters (8, 9) and / or individual receivers.

8. Use of an arrangement (1) for generating and / or detecting ultrasonic waves according to one of claims 1 to 7 for a

Environment sensing or for wireless communication.

9. A method for producing an arrangement (1) for generating and / or detecting ultrasonic waves according to one of claims 1 to 7, comprising the method steps:

a) providing a piezoelectric layer (2) having a first side and a second side;

b) arranging at least one electrically conductive element (5) on the first side of the piezoelectric layer (2);

c) arranging at least one electrically conductive element (6, 7) on the second side of the piezoelectric layer (2); and

d) arranging a graphene-comprising protective layer (10) on the

first side of the piezoelectric layer (2) on the

piezoelectric layer (2) opposite side of the electrically conductive element (5).

The method of claim 9, wherein the graphene-comprising protective layer (10) is epitaxially grown on the first side of the

piezoelectric layer (2) on the piezoelectric layer (2) opposite side of the electrically conductive element (5) is arranged.