WO2017005958A1 - Acoustic wave transducer construction and method for accomplishing mechanical waves - Google Patents

Acoustic wave transducer construction and method for accomplishing mechanical waves Download PDF

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Publication number
WO2017005958A1
WO2017005958A1 PCT/FI2015/050489 FI2015050489W WO2017005958A1 WO 2017005958 A1 WO2017005958 A1 WO 2017005958A1 FI 2015050489 W FI2015050489 W FI 2015050489W WO 2017005958 A1 WO2017005958 A1 WO 2017005958A1
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WO
WIPO (PCT)
Prior art keywords
acoustic wave
mechanical waves
material
characterized
impedance characteristics
Prior art date
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PCT/FI2015/050489
Other languages
French (fr)
Inventor
Kimmo Mustonen
Pasi Karppinen
Heikki Juhani Nieminen
Antti KASKELA
Edward HÆGGSTRÖM
Esko Kauppinen
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Aalto University Foundation
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Priority to PCT/FI2015/050489 priority Critical patent/WO2017005958A1/en
Publication of WO2017005958A1 publication Critical patent/WO2017005958A1/en

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Classifications

    • AHUMAN NECESSITIES
    • A61MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61BDIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B8/00Diagnosis using ultrasonic, sonic or infrasonic waves
    • A61B8/44Constructional features of the ultrasonic, sonic or infrasonic diagnostic device
    • A61B8/4483Constructional features of the ultrasonic, sonic or infrasonic diagnostic device characterised by features of the ultrasound transducer
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B06GENERATING OR TRANSMITTING MECHANICAL VIBRATIONS IN GENERAL
    • B06BMETHODS OR APPARATUS FOR GENERATING OR TRANSMITTING MECHANICAL VIBRATIONS OF INFRASONIC, SONIC, OR ULTRASONIC FREQUENCY, e.g. FOR PERFORMING MECHANICAL WORK IN GENERAL
    • B06B1/00Methods or apparatus for generating mechanical vibrations of infrasonic, sonic, or ultrasonic frequency
    • B06B1/02Methods or apparatus for generating mechanical vibrations of infrasonic, sonic, or ultrasonic frequency making use of electrical energy
    • B06B1/06Methods or apparatus for generating mechanical vibrations of infrasonic, sonic, or ultrasonic frequency making use of electrical energy operating with piezo-electric effect or with electrostriction
    • B06B1/0644Methods or apparatus for generating mechanical vibrations of infrasonic, sonic, or ultrasonic frequency making use of electrical energy operating with piezo-electric effect or with electrostriction using a single piezo-electric element
    • B06B1/0662Methods or apparatus for generating mechanical vibrations of infrasonic, sonic, or ultrasonic frequency making use of electrical energy operating with piezo-electric effect or with electrostriction using a single piezo-electric element with an electrode on the sensitive surface
    • B06B1/067Methods or apparatus for generating mechanical vibrations of infrasonic, sonic, or ultrasonic frequency making use of electrical energy operating with piezo-electric effect or with electrostriction using a single piezo-electric element with an electrode on the sensitive surface which is used as, or combined with, an impedance matching layer
    • GPHYSICS
    • G01MEASURING; TESTING
    • G01SRADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S15/00Systems using the reflection or reradiation of acoustic waves, e.g. sonar systems
    • G01S15/88Sonar systems specially adapted for specific applications
    • G01S15/89Sonar systems specially adapted for specific applications for mapping or imaging
    • G01S15/8906Short-range imaging systems; Acoustic microscope systems using pulse-echo techniques
    • G01S15/895Short-range imaging systems; Acoustic microscope systems using pulse-echo techniques characterised by the transmitted frequency spectrum
    • G01S15/8954Short-range imaging systems; Acoustic microscope systems using pulse-echo techniques characterised by the transmitted frequency spectrum using a broad-band spectrum
    • GPHYSICS
    • G10MUSICAL INSTRUMENTS; ACOUSTICS
    • G10KSOUND-PRODUCING DEVICES; METHODS OR DEVICES FOR PROTECTING AGAINST, OR FOR DAMPING, NOISE OR OTHER ACOUSTIC WAVES IN GENERAL; ACOUSTICS NOT OTHERWISE PROVIDED FOR
    • G10K11/00Methods or devices for transmitting, conducting or directing sound in general; Methods or devices for protecting against, or for damping, noise or other acoustic waves in general
    • G10K11/002Devices for damping, suppressing, obstructing or conducting sound in acoustic devices
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B06GENERATING OR TRANSMITTING MECHANICAL VIBRATIONS IN GENERAL
    • B06BMETHODS OR APPARATUS FOR GENERATING OR TRANSMITTING MECHANICAL VIBRATIONS OF INFRASONIC, SONIC, OR ULTRASONIC FREQUENCY, e.g. FOR PERFORMING MECHANICAL WORK IN GENERAL
    • B06B1/00Methods or apparatus for generating mechanical vibrations of infrasonic, sonic, or ultrasonic frequency
    • B06B1/02Methods or apparatus for generating mechanical vibrations of infrasonic, sonic, or ultrasonic frequency making use of electrical energy
    • B06B1/0207Driving circuits
    • B06B1/0215Driving circuits for generating pulses, e.g. bursts of oscillations, envelopes
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B06GENERATING OR TRANSMITTING MECHANICAL VIBRATIONS IN GENERAL
    • B06BMETHODS OR APPARATUS FOR GENERATING OR TRANSMITTING MECHANICAL VIBRATIONS OF INFRASONIC, SONIC, OR ULTRASONIC FREQUENCY, e.g. FOR PERFORMING MECHANICAL WORK IN GENERAL
    • B06B1/00Methods or apparatus for generating mechanical vibrations of infrasonic, sonic, or ultrasonic frequency
    • B06B1/02Methods or apparatus for generating mechanical vibrations of infrasonic, sonic, or ultrasonic frequency making use of electrical energy
    • B06B1/06Methods or apparatus for generating mechanical vibrations of infrasonic, sonic, or ultrasonic frequency making use of electrical energy operating with piezo-electric effect or with electrostriction
    • B06B1/0607Methods or apparatus for generating mechanical vibrations of infrasonic, sonic, or ultrasonic frequency making use of electrical energy operating with piezo-electric effect or with electrostriction using multiple elements
    • B06B1/0611Methods or apparatus for generating mechanical vibrations of infrasonic, sonic, or ultrasonic frequency making use of electrical energy operating with piezo-electric effect or with electrostriction using multiple elements in a pile
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B06GENERATING OR TRANSMITTING MECHANICAL VIBRATIONS IN GENERAL
    • B06BMETHODS OR APPARATUS FOR GENERATING OR TRANSMITTING MECHANICAL VIBRATIONS OF INFRASONIC, SONIC, OR ULTRASONIC FREQUENCY, e.g. FOR PERFORMING MECHANICAL WORK IN GENERAL
    • B06B1/00Methods or apparatus for generating mechanical vibrations of infrasonic, sonic, or ultrasonic frequency
    • B06B1/02Methods or apparatus for generating mechanical vibrations of infrasonic, sonic, or ultrasonic frequency making use of electrical energy
    • B06B1/06Methods or apparatus for generating mechanical vibrations of infrasonic, sonic, or ultrasonic frequency making use of electrical energy operating with piezo-electric effect or with electrostriction
    • B06B1/0688Methods or apparatus for generating mechanical vibrations of infrasonic, sonic, or ultrasonic frequency making use of electrical energy operating with piezo-electric effect or with electrostriction with foil-type piezo-electric elements, e.g. PVDF
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B06GENERATING OR TRANSMITTING MECHANICAL VIBRATIONS IN GENERAL
    • B06BMETHODS OR APPARATUS FOR GENERATING OR TRANSMITTING MECHANICAL VIBRATIONS OF INFRASONIC, SONIC, OR ULTRASONIC FREQUENCY, e.g. FOR PERFORMING MECHANICAL WORK IN GENERAL
    • B06B2201/00Indexing scheme associated with B06B1/0207 for details covered by B06B1/0207 but not provided for in any of its subgroups
    • B06B2201/70Specific application
    • B06B2201/76Medical, dental
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B82NANOTECHNOLOGY
    • B82YSPECIFIC USES OR APPLICATIONS OF NANOSTRUCTURES; MEASUREMENT OR ANALYSIS OF NANOSTRUCTURES; MANUFACTURE OR TREATMENT OF NANOSTRUCTURES
    • B82Y30/00Nanotechnology for materials or surface science, e.g. nanocomposites

Abstract

An object of the invention is an acoustic wave transducer construction for accomplishing mechanical waves to an object. The construction comprises at least one source (100) for receiving electrical current and for producing mechanical waves on the basis of the received current and receiving means (108, 110, 111) for detecting said mechanical waves. The source (100) comprises material having impedance characteristics close to the impedance characteristics of the object, and the construction further comprises an attenuation material (104) for directing the produced mechanical waves to the object.

Description

Acoustic wave transducer construction and method for accomplishing mechanical waves

Field of the invention

Ultrasound arrays are required in medical imaging and therapy to rapidly and flexibly image or treat internal organs and tissue of a patient. State of the art

Traditionally ultrasound arrays comprise piezo-ceramic elements that mechanically are joined together by a rigid framework. The elements are electrically isolated from each other. The arrays can be driven with e.g. sinusoidal or coded signals in line- ar/non-linear or phased manner depending on the driving electronics and the application in question.

State-of-the art arrays are of CMUT (capacitive micromachined ultrasonic transducer) type, although not broadly commercially available. Films of e.g. carbon nano- tubes (CNTs) can produce audible sound and high frequency ultrasound through thermoacoustic emission; a short current pulse driven through the film induces a heat transient that quickly expands the surrounding dielectric (gas or solid) and thus excites a pressure pulse. At audible frequencies the energy conversion efficiency (i.e.e. ratio of introduced electronic power and emitted acoustic power) of such a device is low, but it increases remarkably at ultrasonic frequencies (dictated by the current pulse duration).

In the patent application document EP 2114088 (A2) is presented a sound producing device including a signal device and a sound generator. The sound generator is electrically connected to the signal device. The sound generator includes a CNT structure that produces sound in response to receiving an input signal from the signal device. Ultrasound imaging devices require sufficient ultrasound pressure produced by the device to image a patient. Low pressure causes image quality problems, which can lead e.g. to misleading or inconclusive diagnoses. Short description of the invention

An object of the present invention is to achieve an acoustic transducer construction and method which produce high acoustic pressures and temporally and/or spatially short pulses (i.e. broadband frequency content) into an object (e.g. a patient) to produce high image quality. This is achieved by an acoustic wave transducer construction for accomplishing mechanical waves to an object. The construction comprises at least one source for receiving electrical current and for producing mechanical waves on the basis of the received current and receiving means for detecting said mechanical waves, the source comprising material having impedance character- istics close to the impedance characteristics of the object, and the construction comprises an attenuation material for directing the produced mechanical waves to the object.

An object of the invention is also an acoustic wave method for accomplishing me- chanical waves to an object. In the method is received electric current and produced mechanical waves on the basis of the received current by material having mechanical impedance characteristics close to the mechanical impedance characteristics of water, and is attenuated said mechanical waves in order to direct mechanical waves to the object.

The invention is based on utilizing the electric impedance characteristics of a source that receives electric current and produces mechanical waves on the basis of the received electric current. The invention is further based on using an attenuation material that directs the produced mechanical waves to an object, which is e.g. a patient.

A benefit of the invention is that high signal to noise ratio (SNR) and short sound pulses can be achieved that result in high image quality, which increases the probability of making correct and conclusive diagnoses on the basis of the acoustic imag- es. Other benefits of the invention are that the nano-tube transducer is (i) durable, (ii) flexible, (iii) heat-resistant, and (iv) optically semi-transparent. In an ultrasound imaging transducer, flexibility potentially reduces cross-talk artifacts between adjacent transducer elements and potentially reduces propensity for impure emission modes.

Short description of figures

Figure 1 presents first exemplary embodiment according to the present inven- tion.

Figure 2 presents second exemplary embodiment according to the present invention. Figure 3 presents preferred embodiment according to the present invention.

Figure 4 presents alternative embodiment according to the present invention.

Figures 5A-5B present an ultrasound signal produced according to the present in- vention and the frequency content of said signal.

Detailed description of the invention

According to the present invention can be constructed constructions of an acoustic transducer, in which constructions can be produced acoustic wave energy, e.g. ultrasound energy, into compositions consisting of high amounts of water, e.g. into living tissue, with higher efficiency at high frequencies than low frequencies as proposed in EP 2114088 (A2). This energy conversion efficiency is important, because the more ultrasound can be produced within safety limits, the higher signal to noise ratio (SNR) can be achieved without excess heating. In practice in imaging applications this means higher image quality. In the embodiments according to the present invention are described constructions utilizing e.g. nano-tubes, nano-wires or nano- fibers so that the construction can be used as ultrasound transmitters in medical devices and in other imaging applications. One of the key benefits of the transducer construction is that it is thin and flexible and features acoustic impedance close to that of water. Due to the flexibility of the transducer construction it can be used e.g. in an ultrasound imaging glove and it can enable manufacturing complex transducer topologies that are (i) not possible or (ii) are burdensome to make with PTZ or CMUT technology. In addition, the flexibility allows one to modify the transducer geometry in extracorporeal and intracorporeal applications. Intracorporeal imaging and therapy applications are based on self-regulation (diameter of body cavity, e.g. varying vessel wall diameter) or on active geometry regulation (another device deforms the shape of the transducer). This allows one to modify the focusing capabil- ity of the ultrasound system e.g. during a diagnostic event (large radius of curvature for coarse imaging and modified smaller radius of curvature for imaging details). This has benefits at least for therapy application: Geometric focusing reduces the risk for unwanted off-focus heating and, in extreme cases, consequent tissue burns when high ultrasound intensity is produced. An alternative way to direct the beam is to use reflectors at 45 degree angle as described by Toda 2009 (New symmetric reflector ultrasonic transducers (SRUT). Ultrasonics, Ferroelectrics, and Frequency Control, IEEE Transactions on. 2009;56(10): 2311-2319).

The presented ultrasound transducer may tolerate time-averaged temperatures ex- ceeding 100°C without breaking. Therefore, the transducer could be used in conjunction with thermal ablation devices to monitor the ablation effect simultaneously, or the transducer could be used as a thermal ablation contact device itself. Exemplary embodiment 1: constant current through the transducer could heat the membrane and allow thermal ablation when in contact with tissue e.g. heart or tumor tissue. Exemplary embodiment 2: Focusing of ultrasound energy could lead to thermal ablation within the focus volume. Other ultrasound therapies, e.g. drug delivery/transport, cell stimulation or remote palpation (ARFI) can also be applied. In addition to ultrasound field, the electric field produced near the nano-tube, nano- fiber and /or nano-wire construct can be applied for imaging, actuation and/or ma- nipulation purposes.

In figure 1 is presented first exemplary imaging embodiment according to the present invention consisting of multiple layers of functional components and attenuation material 104 joined together by adhesives or by polymer casting. As attenua- tion materials, commercial polymers may be utilized, e.g. Kapton™ or PET (polyeth- lylene). Above, within or below attenuation material 104, the device is constructed layer by layer, consisting of i) conductive pathways, which may be produced with multiple techniques, e.g. printing, sputtering or with a stencil, ii) angle sensors to track the relative position of the array elements, iii) PVDF (polyvinylidene fluoride) film based receivers 108, iv) a patterned layer of film 106, that may be deposited either by dry transfer technique or by solution drop casting or by spraying or by spinning, v) an encapsulating layer 102 of polymer that hermetically encloses and passivates the film 106 constructed of nanowires or nanotubes or nanoflakes made of e.g. carbon, silver, gold, copper, or indium dioxide or graphene and functions as an acoustic matching layer between the tissue and the ultrasound emitter 100. In the embodiments according to the present invention the layer organization may differ from that presented in figure 1. The films 106 may easily be patterned into a formation of multiple point sources of ultrasound, thus efficiently mimicking the structure of ultrasound arrays. Moreover, these ultrasound arrays made of nanotube/nanowire films bear important advantages over the traditional approach; their acoustic impedance is close to that of water, they are flexible and cheap to manufacture, they suffer no charging prob- lems, and they are rather insensitive to contact. The elements of the ultrasound transducer according to the present invention can be manufactured in a smaller size than piezo transducers permitting manufacture of miniature ultrasound devices for e.g. intracorporeal use such as catheter-based devices or swallowable ultrasound devices that can be swallowed. Cheap manufacturing of transducers according to the present invention also permits use of large transducer mats fixed for long-term to a construction that moves and/or bends or is stationary in real-time monitoring fatigue e.g. in industrial applications or in applications in austere environments (e.g. space, aviation, factories, nuclear plants). Present invention permits manufacturing conventional or flexible ultrasound probes that are portable and enabling various industrial or material testing applications. Flexibility also permits integrating the ultrasound probes into materials e.g. clothing.

An arbitrary geometry 2D ultrasound array may be constructed in the previously explained way. Thanks to the flexibility of the layers, the array geometry may be altered on-the-fly by the end user (e.g. external force produced by hand). The geometry is tracked on-the-fly by angle sensors embedded inside the device as described. In figure 2 is presented a second exemplary embodiment according to the present invention, in which embodiment a rigid (non-flexible) or elastic (flexible) array of ultrasound point sources 100 may be constructed utilizing films made of nanowires or nanotubes e.g. carbon nanotubes. Such a device consists of i) an attenuation material 104, which may be any rigid or elastic material, preferably such having readily available facilities for required processing (e.g. silicon or silicon oxide, or alike), being patterned by etching or by other means to have grooves or dents and necessary conductive pathways, ii) a film 106 made of e.g. carbon nanotubes or a similar material consisting of sub-micrometer, electrically conductive fibers deposited in the bottom of the grooves or dents, and galvanically coupled to the conductive pathways iii) an inert gas (e.g. argon or nitrogen) atmosphere 105 filling the grooves or dents, iv) a membrane enclosing the grooves and dents to form cavities. The operation principle of such a device is similar to that of the device type described related to figure 1. A current pulse induces a heat transient, generating a propagating pressure pulse in the inert gas 105 enclosed inside the cavity. The propagating pulse and expansion of the inert gas induces a displacement on the water/electric current insulation layer 102 enclosing the cavity, which may then be coupled to any material in contact.

In the embodiments according to the present invention the coupling surface area between the nanowire/nanotube network film 106 and the encapsulating layer 102 should be maximized, to provide highest conversion efficiency of electronic power into pressure and pressure gradient. The electric impedance, consisting mainly of a resistive part, should be minimized in order to drive required power even when utilizing e.g. a low voltage system (< 50 V). The specific heat capacitance of the ultra- sound emitting film 106 should be minimized, also positively impacting the efficiency of the device, while the heat conductance should be maximized for the same reason. The encapsulating water-insulating layer 102 should consist of a polymer (or equivalent) having an acoustic impedance close or otherwise relevant to that of a human or animal tissue (~water). Preferably, but not necessarily, the specific heat capacitance of the polymer (or equivalent) can be minimized, while the thermal expansion coefficient of the polymer (or equivalent) can be maximized simultaneously. This enhances the conversion of electronic power to ultrasound. The transducer according to the present invention is preferably interfaced to a power source by matching electric and acoustic impedances to be similar. Also electric broadband matching can used. Maximum bandwidth means low acoustic impedance level, and maximum pressure level means large amplitude level. Preferably, but not necessarily, the base material should have high specific heat capacitance and high thermal conductivity to function as a heat sink of the operating device. The base layer 104 could also be acoustically mismatched from the rest of the device to reflect the ultrasound pulses towards the tissue of a patient, especially in therapeutic applications.

In figure 3 is presented one preferred embodiment according to the present inven- tion, in which the acoustic wave transducer construction comprises three layers: center: an ultrasound emitter 100 that produces mechanical waves on the basis of the electric current received by 106. The source 100 comprises material whose mechanical impedance characteristics are close to those of water. The construction comprises a layer 102, insulating electric current and water penetration, to electri- cally/wetting-wise insulate the film 106, and an attenuation material 104 to prevent mechanical waves from propagating in non-optimal directions. The objects of the invention are achieved on the basis of the functional combination of said layers.

In one preferred embodiment of the present invention the material having mechani- cal impedance characteristics close to those of water is made of at least partly nongaseous material, e.g. of metal (e.g. steel) or of plastic material. The mechanical impedance characteristics are considered close to those of water when they deviate 20% or less from the impedance characteristics of water. Said at least one source 100 comprises for producing mechanical waves to the patient thermoacoustic means 106 embedded in material whose mechanical impedance characteristics are close to those of water. The thermoacoustic means 106 can be arranged as nano- tubes being embedded in material whose mechanical impedance characteristics are close to those of water. The water and/or electric current insulation layer 102 for insulating the film 106 is made of material that is at least partly flexible. The atten- uation material layer 104 for directing the produced mechanical waves to the patient is made of material that attenuates the mechanical waves propagating in non- optimal directions. In the preferred embodiments of the invention the construction can also comprise at least one detection layer embedded in 104 for detecting the mechanical waves from the patient.

In the preferred embodiment according to the present invention the thermoacoustic means 106 can be arranged as at least one of nanotubes and nanowires and nano- fibers, which can be embedded in the material having impedance characteristics close to the impedance characteristics of water. The source, i.e. the emitter 100, emits mechanical waves, i.e. produces ultrasound to the patient, when electric current passes through the layer 106 comprising nanotubes/nanowires. Due to its mechanical impedance characteristics close to those of water, the nano-tube layer 106 material can produce imaging-wise non-negligible amount of ultrasound waves to the patient consisting mostly of water. A network of nanotubes is embedded in a polymer, or in an equivalent material, whose mechanical impedance is close to that of water. A physical phenomenon is that at an interface of two materials whose mechanical impedance are close to each other, sound waves (i.e. mechanical waves) pass from the first material to the other material efficiently. When electric current is passed through the nanotube network embedded in the polymer material, or in an equivalent material, the polymer material or gas expands due to heat that is produced by electric current in the nanotubes. This rapid, nano/microsecond time scale thermal expansion generates ultrasound. This ultrasound can then efficiently pass into the patient. The ultrasound wave penetration efficiency (imaging depth) into the patient can be further improved by embedding various materials and/or nano- particles into the nano-tube/nano-wire network for enhanced impedance matching. These materials or nano-particles can be e.g. gold nanoparticles and/or gas such as argon. An alternative to matching the transducer acoustically to water is e.g. matching the transducer to gas such as air. This can be necessary for imaging e.g. air- borne targets.

Figure 4 presents one exemplary embodiment in which film 106 comprising nanotubes/nanowires is attached to construction/electrode 109. When electric current is passed through film 106 mechanical waves are emitted from emitter 100. Incoming mechanical waves may be detected by optical means, e.g. using a vibrometer 111 that points an optical beam 110 towards film 106. Incoming mechanical wave displaces the film 106. This displacement can then be detected by means of 110 and 111. The emitter 100 may or may not be embedded in water- and electricity- insu- lating layer (insulating layer not in figure 4). Emitter 100 or film 106 can be coated with optically reflecting material to enhance reflection of optical waves back to the vibrometer 111.

The insulation layer 102 insulates the transducer construction from water: no fluid connection, no galvanic connection. This insulation layer protects the nanotube network from damage due to mechanical wear, chemical contamination or other adverse effects. In principle, the material can be a polymer similar to that used to embed the ultrasound emitting layer (see above). The purpose of the attenuation material layer 104 is to prevent ultrasound from propagating in an unwanted direction. The difference between this attenuation material layer 104, and that used in piezoelectric transducers is that this material does not need to dampen mechanical displacements in the ultrasound source (as is the case with traditional ultrasound transducers). In embodiments according the pre- sent invention said dampening layer 104 only needs to attenuate the ultrasound travelling in the "wrong" direction.

The transducer according to the present invention can potentially be self-calibrating i.e. it can monitor and/or control its acoustic output pressure and also other output characteristics, such acoustic output waveform and power. In embodiments according to the present invention the ultrasound system can also be used in a similar way as 3D-printed PZT-plastic transducer structures.

High peak emission energy of the presented transducer construction also allows ultrasonic therapeutic actuating use of the transducer (thermal ablation, drug delivery and/or release and/or transport, gene delivery, cell stimulation, sonoporation, nebulization and/or atomization etc.). Figure 5A presents an example of an ultrasound pulse generated with a device according to present invention. The sound is produced with a construct having 6 layers of carbon nano-tube membrane excited with 400 V electric pulses (pulse repetition frequency: 50 Hz; number of signal averages: 128) and recorded using a nee- die hydrophone, receiver-side amplifier (40 dB) and an oscilloscope. The positive peak pressure of the acoustic pulse is 11.8 ± 0.2 kPa. Figure 5B presents the frequency content of the same signal (center frequency: 5.2 MHz; -6 dB absolute/relative bandwidth: 6.9 MHz/133%). Although the invention has been presented in reference to the attached figures and specification, the invention is by no means limited to those, as the invention is subject to variations within the scope allowed for by the claims.

Claims

Claims
1. An acoustic wave transducer construction for accomplishing mechanical waves to an object, characterized by, that the construction comprises at least one source (100) for receiving electrical current and for producing mechanical waves on the basis of the received current and receiving means (108, 110, 111) for detecting said mechanical waves, the source (100) comprising material having impedance characteristics close to the impedance characteristics of the object, and the construction comprises an attenuation material (104) for directing the produced mechanical waves to the object.
2. An acoustic wave transducer construction according to claim 1, characterized by, that the construction comprises an insulation layer (102) for insulating at least one of the receiving means (108, 110, 111) and source (100).
3. An acoustic wave transducer construction according to claim 1, characterized by, that the material having impedance characteristics close to the impedance characteristics of water is being made of at least partly non-gaseous material.
4. An acoustic wave transducer construction according to claim 1, characterized by, that said at least one source (100) comprises for producing mechanical waves to the object thermoacoustic means (106) embedded in the material having impedance characteristics close to the impedance characteristics of water.
5. An acoustic wave transducer construction according to claim 3, characterized by, that the construction comprises the thermoacoustic means (106) being arranged as at least one of nanotubes and nanowires and nanofibers being embedded in the material having impedance characteristics close to the impedance characteristics of water.
6. An acoustic wave transducer construction according to claim 1, characterized by, that the insulation layer (102) for insulating the film (106) is being made of at least partly flexible material.
7. An acoustic wave transducer construction according to claim 1, characterized by, that the attenuation material (104) for directing the produced mechanical waves to the object is being made of material that attenuates the mechanical waves propagating in a non-optimal direction.
8. An acoustic wave transducer construction according to claim 1, characterized by, that the construction comprises at least one detection layer (108) for detecting the mechanical waves from the object.
9. An acoustic wave transducer construction according to claim 1, characterized by, that the construction comprises at least one optical system (110, 111) for detecting the mechanical waves from the object.
10. An acoustic wave method for accomplishing mechanical waves to an object, characterized by, that in the method is received electric current and produced mechanical waves on the basis of the received current by material having mechanical impedance characteristics close to the mechanical impedance characteristics of water, and is attenuated mechanical waves in order to direct said mechanical waves to the object.
11. An acoustic wave transducer method according to claim 10, characterized by, that in the method is insulated at least one of receiving means (108, 110, 111) and source (100).
12. An acoustic wave method according to the claim 10, characterized by, that the material having impedance characteristics close to the impedance characteristics of water is being made of at least partly non-gaseous material.
13. An acoustic wave method according to the claim 10, characterized by, that in the method is embedded thermoacoustic means (106) in the material having impedance characteristics close to the impedance characteristics of water for producing mechanical waves to the object.
14. An acoustic wave method according to the claim 12, characterized by, that the thermoacoustic means (106) are arranged as at least one of nanotubes and nanowires and nanofibers being embedded in the material having impedance characteristics close to the impedance characteristics of water.
15. An acoustic wave method according to the claim 10, characterized by, that the insulation of said material is performed by at least partly by utilizing flexible material.
16. An acoustic wave method according to the claim 10, characterized by, that the attenuation is performed by material that attenuates the mechanical waves propagating to a non-optimal direction.
17. An acoustic wave method according to the claim 10, characterized by, that in the method is detected the mechanical waves from the object by using at least one detection layer (108).
18. An acoustic wave method according to the claim 10, characterized by, that in the method is detected the mechanical waves from the object by using at least one optical system (110, 111).
PCT/FI2015/050489 2015-07-06 2015-07-06 Acoustic wave transducer construction and method for accomplishing mechanical waves WO2017005958A1 (en)

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