Graphene backing for ultrasonic transducers

Abstract

To provide a mechanically stable backing material with high damping and high thermal conductivity. [Solution] For ultrasonic transducers, graphene, in the form of flakes or sheets, is used in a backer having a polymer matrix. The graphene is incorporated into a polymer matrix type backing block. Graphene provides good attenuation and good thermal conductivity at low frequencies.

Description

Technical Field

[0001] The embodiments disclosed herein relate to ultrasonic transducers.

Background Art

[0002] An ultrasonic transducer includes a piezoelectric (PZT) layer laminated on a backing (support) block. The ultrasonic backing block is typically made of a composite of a polymer (epoxy or silicone) matrix that supports metal particles. Such a type of backing (support) is often not thermally conductive and has low attenuation at low frequencies or weak mechanical strength.

[0003] High thermal conductivity can be provided by porous graphite or metal foam having polymer-filled voids. Such a backing in which the thermally conductive material forms a matrix or support structure has low attenuation at low frequencies. Some unfilled voids can potentially induce image artifacts.

Summary of the Invention

[0004] First, the preferred embodiments described below include methods, systems, backings, and components related to ultrasonic transducers. Graphene, such as flakes or sheets, is used in a backing having a polymer matrix. Graphene provides good attenuation at low frequencies and thermal conductivity.

[0005] A transducer array system according to a first aspect includes an array of ultrasonic transducer elements and a backing having a polymer framework, and one or more sheets of graphene are supported by the polymer framework.

[0006] In a second aspect, a method of forming an ultrasonic backing block is provided. A graphene sheet is combined with a polymer. The polymer is cured. The cured polymer becomes a support matrix that supports graphene flakes or sheets.

[0007] An ultrasonic transducer backing block according to a third embodiment includes a matrix of cured polymer, the cured polymer comprising a soft polymer and graphene flakes in the matrix. Each flake of graphene is held in a predetermined position in the matrix by the cured polymer surrounding the graphene.

[0008] Further embodiments and features are outlined in the embodiments illustrated below. Each embodiment and / or feature may be used in various combinations. An embodiment and / or feature in one context (e.g., a system, backing, or method) may also be used in another context.

[0009] The present invention is defined by the claims, and what is stated in this section should not be construed as a limitation to those claims. Further aspects and advantages of the present invention will be described below in connection with preferred embodiments, and may be claimed separately or in combination thereafter. Different embodiments may or may not achieve different purposes or advantages. [Brief explanation of the drawing]

[0010] The components and drawings are not necessarily to scale, and are rather exaggerated in order to illustrate the principles of the present invention. Furthermore, in the drawings, the same reference numerals indicate corresponding parts throughout the figures. [Figure 1] A cross-sectional view showing an example of a transducer stack using a backing with integrated graphene flakes. [Figure 2] The damping and thermal conductivity of various backings, including those with integrated graphene, are shown as bar graphs in Figures 2A and 2B, respectively. [Figure 3] A cross-sectional view showing an example of a backing with a graphene sheet. [Figure 4]A cross-sectional view showing an example of a backing with a graphene sheet. [Figure 5] A cross-sectional view showing an example of a backing with a graphene sheet. [Figure 6] A cross-sectional view showing an example of a backing with a graphene sheet. [Figure 7] A cross-sectional view showing an example of a backing with a graphene sheet. [Figure 8] A perspective view showing an example of a backing formed as a roll of graphene supported by a polymer matrix. [Figure 9] A flowchart illustrating one embodiment of a method for forming a backing having integrated graphene. [Modes for carrying out the invention]

[0011] [Detailed description of drawings and currently preferred embodiments]

[0012] The backing block structure contains graphene. Graphene possesses high mechanical strength and high thermal conductivity of 1000 W / mK along the sheet. Graphene also exhibits low velocity and high damping in the Z-direction or thickness direction due to weak (van der Waals) forces between graphene layers. The unique properties of graphene can be used to achieve a mechanically stable backing with high damping and high thermal conductivity.

[0013] Instead of using voided graphite blocks (e.g., foam matrices), graphene is incorporated into polymer matrix-type backing blocks. The resulting backing leverages the mechanical and thermal properties of graphene to provide good damping, thermal conductivity, and mechanical strength in a balanced approach. Graphene is incorporated into polymer-based backings with metallic particles as microflakes, combining high impedance, high damping, and high thermal conductivity compared to many existing backers. Graphene can also be incorporated into polymer-based backings as graphene sheets potted with the polymer-based backing to overcome the bonding problems of graphene sheets.

[0014] Composite backings of polymer matrices with integrated graphene can be used in various transducers, including 1D, 1.5D, and 2D transducers. Thermal quality is better than other polymer-based backings. Imaging quality may be better than metal foam-based backings. Better low-frequency operation may be provided.

[0015] Figure 1 is a cross-sectional view showing one embodiment of a transducer array system. This cross-section is in the depth-elevation direction, where depth is the longitudinal direction on the drawing and elevation is the transverse direction on the drawing. Each element of the array 100 is distributed along the azimuth direction (the direction towards or away from the plane of the drawing). The transducer array system includes a backing block 170 formed of a polymer matrix 172 supporting graphene flakes 174 and optional powders or particles 176, such as metal powder, for impedance matching.

[0016] The transducer array system is used in ultrasound transducer probes, for example, in handheld probes for scanning from outside the patient, or in intracavitary (e.g., TEE or TTE) or catheter-based probes for scanning from inside the patient. The system includes a one-dimensional or multi-dimensional transducer array 100. In the case of a multi-dimensional array 100, the array 100 may be a 1.25, 1.5, 1.75, or 2D array with elements distributed in both azimuth and elevation.

[0017] The transducer array system includes matching layers 110, 120, an array layer (e.g., a piezoelectric (PZT) layer 130), and an acoustic backer (a backing block of acoustic attenuation material) 170. Additional or different layers, such as ground electrodes and signal electrodes, may be included, or there may be fewer layers. In another example, an integrated circuit or chip connected to the backing layer is provided. In yet another example, neither of the matching layers 110, 120 is included, or an additional matching layer is included. In one example, a lens and / or housing is provided around the transducer array system or adjacent to a second acoustic matching layer 110. In another example, layers of flexible circuit material connect between the backing block 170 and the PZT layer 130, connect to one side of the PZT layer 130, connect on the back side of the backing block 170 opposite to the PZT layer 130, and / or connect at other locations for routing a signal path between the PZT layer 130 and an ultrasonic scanner. The transducer array system and the corresponding probe are formed using the method shown in Figure 9 or another method.

[0018] The matching layer 110 and the matching layer 120 are quarter wavelength thick layers of material. A plurality of layers may be used to stepwise vary the acoustic impedance, although in other embodiments only one matching layer is provided. The second matching layer 110 provides an acoustic impedance transition between the patient, lens, or other material and the first matching layer 120. Similarly, the first matching layer 120 provides an acoustic impedance transition from the second matching layer 110 to the piezoelectric or other transducer array layer 130.

[0019] The array layer is shown as the PZT layer 130, but may include the first matching layer 120. The PZT layer 130 is a slab or plate of PZT material. Solid PZT may be used. Single crystal or polycrystalline PZT material may be used. In other embodiments, a composite of a piezoelectric material and an epoxy or other polymer is used. Microelectromechanical (capacitive membrane) elements may also be used instead of PZT. Since an example of a piezoelectric element is used here, the array layer is referred to as the PZT layer 130.

[0020] After dicing, the PZT layer 130 forms an array 100 of transducer elements. The transducer elements of the array 100 or the PZT layer 130 are distributed in a grid pattern that extends one-dimensionally or two-dimensionally. When the PZT layer 130 forms a 1D array, each transducer element is distributed linearly as a straight or curved line. The PZT layer 130 may also form a multi-dimensional array 100 in which each element is distributed two-dimensionally (azimuth and elevation).

[0021] The transducer array 100 is an array of PZT elements. Each element converts acoustic energy and electrical energy, such as an array of transducer elements formed from PZT material. A kerf (cutting groove) separates each element of the PZT layer 130. The kerf may also separate the first acoustic matching layer 120. In other embodiments, the kerf separates the second matching layer 110. In still other embodiments, the kerf does not extend through the first acoustic matching layer 120. The array is flat, concave, or convex.

[0022] Each of the transducer elements of the array includes at least two electrodes, a ground electrode and a signal electrode. The signal electrode is separated by a kerf together with the PZT layer 130, such as an electrode formed on the PZT layer 130. Each element converts electrical energy and acoustic energy. The electrical energy generated by or provided to the PZT is provided to the signal electrode separated from the ground electrode. The signal electrode 165 is connected to the signal conductor of the backing block, the signal conductor of the flexible circuit, or other conductor forming the signal path between the array 100.

[0023] The array 100 and the corresponding PZT layer 130 are disposed adjacent to the backing block 170. One side surface of the backing block 170 contacts one side surface of the array 100 or the flexible circuit material between the PZT layer 130 and the backing block 170 (e.g., by asperity contact or by solder). Another layer, such as a bonding material, can separate the PZT layer 130 from the backing block 170.

[0024] The backing block 170 is the backing of the ultrasonic transducer formed by the array 100. The backing block 170 can be a single molded or fabricated (e.g., machined) block for all elements. Alternatively, a plurality of individual backing blocks 170 are provided for each group of elements and / or for each portion of the block.

[0025] The backing block 170 is shaped and sized to bond seamlessly to the array 100. The dimensions of the backing block 170 along the azimuth and transverse directions of the array 100 may be equal to or wider than the array 100. Figure 1 shows the elevation range of the backing block 170 extending outward from the array 100. The depth of the backing block 170 may be greater than one-quarter of the longest wavelength used for the array 100. In one embodiment, this depth is greater than the depth of the PZT layer 130. The backing block 170 may include projections or recesses for close bonding with the PZT layer 130. The backing block 170 may be connected to the PZT layer 130 or the intervening layer in asperity contact using a bonding agent or adhesive such as epoxy. Clips, fasteners, or other structures may be used to close bond or connect the backing block 170 to the array 100. After being aligned, the backing block 170 (for example, a molded block for an acoustic absorber) is bonded or fixed to the PZT layer 130.

[0026] The backing block 170 is an acoustic absorber. The backing block 170 is formed from polymers such as epoxy or silicone, other thermosetting or thermoplastic polymers, or other acoustic absorbers. These polymers can be combined with other materials, such as to form composites of different materials. Multiple materials can be mixed, for example, as a composite backing.

[0027] The matrix or base material is polymer 172, but other bonding agents such as elastomers may be used for the acoustic damping material. The backing block 170 is formed from a support structure of cured polymer 172, such as epoxy, which is mixed with thermosetting and thermoplastic components for chemical curing. Cured epoxy or other cured polymers may be formed using heat, pressure, or other environmental control. The cured polymer 172 as a support structure surrounds, holds, and / or supports filler materials such as graphene 174 and any powder or particles 176. The matrix of cured polymer 172, such as cured epoxy, forms the majority of the volume and / or weight of the backing block 170. The backing block 170 is a polymer framework, by which graphene 174 is supported. A polymer-based composite has graphene 174 embedded inside the polymer framework. The continuous matrix of polymer 172 is the support structure or framework. The graphene 174 to be integrated is within the continuous matrix.

[0028] To alter acoustic attenuation, for example, an arbitrary filler may be mixed with the polymer before curing and added to the framework, in which case the liquid polymer may be poured around the filler and cured, and / or built up on top of the cured polymer pieces.

[0029] In one embodiment, metal powder 176 is included as a filler. For example, aluminum-based (AIN) particles and / or tungsten powder 176 are included in or supported by a polymer matrix. The metal powder 176 may be used to adjust impedance, but may also have attenuation and / or thermal effects. Other powders or particles 176, such as rubber (e.g., RBT or silicone), may also be included.

[0030] The backing block 170 contains graphene 174. Graphene 174 has high mechanical strength and high thermal conductivity (~1000 W / mK) throughout the sheet or flake, but exhibits low rate and high damping in the thickness direction due to weak (van der Waals) forces between graphene layers. This unique property of graphene can be utilized to achieve high damping and even higher thermal conductivity in a mechanically stable backing block 170.

[0031] The filler graphene 174 is added to the polymer matrix. Polymer 172 supports the graphene 174. The graphene 174 is in the matrix and is held in place within the matrix by the cured polymer 172 around the graphene 174.

[0032] In the embodiment shown in Figure 1, graphene 174 is in the form of flakes, such as flower-like or chip-like structures. The flakes are of uniform or varying sizes. For example, most flakes have a maximum dimension of 5 to 500 μm. Each flake is formed from two or more layers of graphene. The large particle size of the graphene flakes (e.g., about 500 μm) and the weak bonding between the graphene sheets forming the flakes contribute to high attenuation at low frequencies (e.g., 1 to 2 MHz). In one embodiment, most flakes have a maximum dimension of 400 to 500 μm. The graphene 174 flakes, as multilayer graphene sheets bonded by weak van der Waals forces, contribute to acoustic energy absorption.

[0033] Graphene 174 flakes are supported or integrated within a framework or matrix of polymer 172. For example, microflakes of graphene 174 are mixed with polymer 172 in a liquid state (before curing). Polymer 172 can be a rigid or flexible polymer (i.e., a Shore A range in which the cured polymer 172 is rigid or flexible). In one embodiment, the epoxy is flexible, such as Shore D of 25 or less (e.g., Shore A of 75 or less, such as 69). Mid-Shore D (e.g., 26-46) or hard Shore D (e.g., 47 or more) may be used. Soft epoxy supporting graphene (e.g., Shore A-69 or Shore D-22) provides substantially better acoustic attenuation than intermediate or rigid epoxy-supported graphene, for example, 3.2 dB / mm at 2.5 MHz for backings made with DER332 epoxy with graphene flakes at Shore D-78, 7.4 dB / mm at 2.5 MHz for backings made with Hysol epoxy with graphene flakes at Shore D-70, and over 18.85 dB / mm at 2.5 MHz for backings made with Epo-tek310M epoxy with graphene flakes at Shore D-22. At 1.5 MHz, soft epoxy with graphene may be 10 dB / mm better (more) than using intermediate or rigid Shore D epoxy. The cured backing block 170 composite has a matrix of polymer 172 supporting graphene 174 flakes, and the distribution of flakes within the matrix is ​​uniform or variable (stepwise).

[0034] Various ratios of polymer 172 and graphene 174 can be used, with or without other powders or particles 176. Compositions can be selected for optimal attenuation and thermal conductivity. Figures 2A and 2B show the attenuation and thermal conductivity at 1.5 MHz, respectively, for different backing blocks. Graphene backing block 170 (GrphnBB) is formed with polymer 172, graphene 174, and metal powder 176 in a ratio of 26 wt% epoxy, 60 wt% tungsten powder, and 13 wt% graphene flakes or powder.GrphnBB is compared with Poco-HTC (graphite matrix or foam with epoxy void filler) and HI-IB (8 wt% epoxy, 24 wt% silicone rubber powder, 25 wt% aluminum nitride, and 42 wt% tungsten powder). As shown in Figure 2A, the graphene-based composite has better acoustic attenuation than others at 1.5 MHz (similar acoustic attenuation to other backers with the best acoustic impedance). As shown in Figure 2B, the graphene-based composite has the second-best thermal conductivity. Graphite matrix backing (Poco-HTC) has the highest thermal conductivity, but low attenuation and high cost are problematic. The HI-IB composite has very low thermal conductivity. The graphene-filled epoxy composite-based backing block 170 improves low-frequency attenuation by utilizing the high absorption between graphene sheets (e.g., attenuation of 10-30 dB / mm or more at 1.5-2 MHz). The graphene-filled epoxy composite offers a good combination of all desirable properties (high acoustic impedance, high attenuation, and high thermal conductivity).

[0035] Figures 3 to 8 show examples of polymer backers having graphene fillers as sheets 174B of graphene 174. One or more sheets 174B of graphene 174 are contained within a polymer framework or matrix. Polymer 172 supports or holds the sheets 174B of graphene 174. Each graphene sheet 174B (e.g., 0.1 mm to 1 mm) is embedded in polymer 172 to form a polymer-based backer. The sheets 174B of graphene 174 enhance damping and thermal conductivity. By using sheets 174B as fillers in the polymer-based backing 170, concerns about the weak bonding of graphene are eliminated. The matrix of polymer 172 holds the sheets 174B of graphene 174 in place. Other fillers may also be included, such as graphene 174 flakes (see Figure 1) and / or other particles or powders 176.

[0036] Direct use of graphene sheet 174B as a backer is not feasible due to the weak bonding of graphene sheet 174B and the extremely low rate that results in strong reflection at the backer interface. Instead, the graphene sheet 174B is integrated (e.g., embedded) into polymer 172 or another backer matrix. Graphene 174 enhances thermal conductivity and attenuation, while the polymer 172 of the matrix or supporting structure holds the sheet 174B in place and limits reflection.

[0037] Sheets 174B of graphene 174 are fabricated from layers of monomolecular graphene joined by van der Waals forces (weak). In one embodiment, each sheet has a thickness of 0.1 to 1 mm and has a region that stretches substantially from edge to edge within the backer 170. In this context, "substantially" is + / - 10%, taking into account tolerances and / or bridges or gaps for the continuity of the polymer matrix. Other thicknesses and / or narrower regions (e.g., stretching only partway through the backer 170) may also be used. For example, sheet 174B stretches to at least halfway between opposing sides. A region of more than a quarter of the cross-section between opposing sides may be used.

[0038] Graphene 174 sheets 174B exhibit high thermal conductivity (e.g., approximately 1000 W / mK) and good tensile strength along the sheet. In the thickness direction, it has low velocity and impedance (e.g., close to air) and high damping. These unique properties are utilized to provide good backer performance (high impedance, high damping, and high thermal conductivity).

[0039] Any number of graphene 174 sheets 174B can be used. For example, Figure 3 shows 3 sheets, Figure 5 shows 9 sheets, and Figure 6 shows 2 sheets. Other numbers may also be used. When multiple sheets 174B are used, each sheet 174B is separated from one another by at least a portion of the polymer framework. The sheets 174B are within the polymer 172, but one or more sheets 174B may be on the edges or surfaces of the polymer 172 or the backing block 170.

[0040] The sheet 174B can be oriented in any way within the backing block 170. The orientation of the graphene sheet 174B can be arranged in various ways for optimal thermal and acoustic performance.

[0041] Figure 3 shows one embodiment. Multiple separate sheets 174B are oriented from front to back in the polymer framework. The front is the surface adjacent to the array 100, and the back is the opposite side from the front. In cross-section, the sheets 174B are stretched from the front and / or back of the backing 170 at arbitrary angles. In the embodiment of Figure 3, each sheet 174B is at a different angle. The graphene 174 sheets 174B spread out in a fan shape in the direction of elevation. At the front, the sheets 174B are densely packed to guide heat away from the array 100. The sheets 174B spread out in a fan shape to dissipate heat well. This fan shape can also be reversed, for example, by bringing the sheets 174B closer together at the back. The sheets 174B can be shifted to be further apart from each other, closer together, and / or at different angles than shown. The distribution of sheet 174B may be shifted in the backer, such that one or more sheets (e.g., all of them) are offset from the center in the elevation direction. Sheet 174B is indicated to stretch approximately in the thickness (z direction) and azimuth (x direction), but may also stretch along any other direction (e.g., elevation-thickness or elevation-azimuth).

[0042] In the embodiments shown in Figures 4 and 5, each sheet 174B is at the same angle to the front surface. The sheets 174B are at an angle of 45 to 85 degrees from the front surface. Larger or smaller angles, such as 1 to 44 degrees or 86 to 90 degrees, may also be used. The graphene 174 sheets 174B are tilted to increase attenuation by causing multiple reflections between the sheets 174B. One or more sheets 174B may be at different angles.

[0043] The spacing between sheets 174B can be larger or smaller. Figure 5 shows the change in spacing when the sheets 174B are more densely packed near the center in the elevation direction. Multiple sheets 174B are at angles of 45 to 85 degrees from the front and have variable spacing across the polymer framework. The graphene 174 sheets 174B are slightly tilted to increase attenuation, either with a uniform pitch or a finer pitch in the center, toward higher thermal conductivity and pressure apodization (e.g., lower impedance in the center for more reflection in the center).

[0044] Figure 6 shows another embodiment. Two or more sheets 174B are within 20 degrees from parallel to the front surface of the polymer framework or backing block 170. Each of the two or more sheets 174B is separated from the other sheets 174B by at least a portion of the polymer framework. One of these sheets 174B is substantially parallel to the front surface (e.g., + / - 2 degrees). Another of these sheets 174B is at a non-zero angle to the other sheet and / or the front surface, such as at an angle of 3 to 20 degrees. For example, two 65 μm thick sheets 174B are used, with the sheet closer to the front surface of the backing block 170 tilted 3 degrees from parallel. This tilt can avoid coherent interference. The two graphene 174 sheets 174B face each other at an angle that increases absorption between the sheets 174B, maximizing attenuation. For example, compared to HI-IB, the configuration in Figure 6 can have attenuation 60 dB greater or more at 2 MHz. Additional sheets 174B, different orientations (angles), separation at different angles, and / or different arrangements of each sheet 174B may also be used. All sheets 174B may be tilted away from being parallel to the front. Multiple sheets 174B may be substantially parallel to the front.

[0045] In the embodiment shown in Figure 7, the angular difference between the sheets 174B in Figure 6 is replaced by an example where one or more sheets 174B are curved or not flat. In this embodiment or any other configuration, one or more sheets 174B are flat and / or one or more sheets 174B are curved. A slight curvature can increase the absorption between the sheets 174B and maximize damping.

[0046] Other configurations of sheet 174B may also be used. For example, the embodiment in Figure 6 may be combined with the embodiments in Figures 3, 4, or 5. Sheet 174B may be a band that can be made into a woven structure. Sheet 174B may have holes or notches for passing other sheets 174B through. Sheet 174B may be made narrower in spread so that sheets 174B can be assembled in various patterns of different angles or directions.

[0047] Figure 8 shows another embodiment. A single sheet 174B of graphene 174 is wound in a helical pattern with a polymer 172 that separates the layers of the sheet. For example, the sheet 174B of graphene 174 is coated with polymer 172, and then the coated sheet 174B is wound. The polymer 172 may be provided on the outside to provide the shape required for the backing block 170. In the example of Figure 8, the roll may be sliced ​​in cross-section so that the sheet 174B extends from the front to the rear of the backing block 170 to form the backing block 170. Other orientations may also be used.

[0048] The roll can be squeezed or twisted before curing. The rolled cylinder is deformed under control to provide an oblique bias to the internal graphene sheet in the spiral. The twisting can change the angle along the rolled sheet, resulting in different spacings between the helical layers at different depths along the roll or backing block 170 during curing. Larger rolls may be used when producing multiple backing blocks 170 by slicing or cutting the roll at different cross-sections.

[0049] For use, the array 100 is electrically connected to an ultrasonic system or scanner. Flexible circuits, wire bonds, and / or other electrical connection methods extend from the ground electrode and signal electrode. For example, a flexible circuit material having pads and metal traces is bonded between the backing block 170 and the array 100 for connection to the signal electrode. Wire jumpers or bonds connect the ground electrode, which is positioned or formed by the matching layer 120, to the flexible circuit material or another wire. Cables connect the ultrasonic scanner (e.g., transmit beamformer and receive beamformer) to the traces of the flexible circuit.

[0050] Array 100 is used for transmission and reception. The backing block 170 reduces acoustic echo or interference from behind Array 100. Reflections are reduced by having an acoustic impedance close to Array 100. The intensity of any reflections is reduced by having higher attenuation. Heat is reduced in the transducer by having higher thermal conductivity, which can avoid pauses for cooling and / or patient discomfort.

[0051] Figure 9 shows an example of a method for forming an ultrasonic backing block for an ultrasonic transducer. Graphene is used as a filler in the polymer-based backing block. The polymer forms a support structure or matrix that supports the graphene.

[0052] This method forms the backing block 170 shown in Figure 1 or Figures 3-8, or another backing block for use with the array 100 in Figure 1 or other arrays. This method can also be used to form other acoustic absorbers for other acoustic transducers.

[0053] Additional or different processes may be provided, or the number of processes may be reduced. For example, a process for alignment with the array and / or bonding in the array stack may be provided. In another example, a process for adding other fillers may be provided. In yet another example, process 920 may not be provided.

[0054] Each process is performed in the order shown in the diagram (e.g., from top to bottom or in numerical order) or in a different order. For example, process 910 is performed before process 900, in which case the graphene filler is stacked with the cured polymer pieces.

[0055] In process 900, graphene is combined with a polymer. Graphene flakes and / or sheets are incorporated into the polymer.

[0056] In one embodiment, a blender, vibrator (e.g., shaker), centrifuge, or other stirring device is used to mix the composite mixture. For example, two parts, liquid epoxy (e.g., epoxy thermosetting resins and thermoplastic resins) and a filler, are placed in a vat. The filler is graphene flakes, with or without other powders or particles. Additional, different, or fewer components may be added. The mixture in the vat is mixed by vibration, rotation, stirring, and / or application of other types of energy to evenly distribute each filler.

[0057] Fillers such as graphene flakes containing or not containing rubber powder (e.g., silicone particles), ceramic powder (e.g., aluminum nitride particles), and / or metal powder (e.g., tungsten or aluminum particles) may be added separately or pre-mixed. Each type of filler may be added separately in any order, or combined and then added to the epoxy. The ratios, deposition percentages, and / or weight percentages of different types of fillers may be used as desired. The components of the fillers are measured and added.

[0058] The components for forming the composite backing are mixed. Any mixing process may be used, including the order of addition, mixing duration, mixing rate, mixing temperature, mixing pressure, mixing humidity, and other controllable mixing characteristics. The result of the mixing is a slurry of the composite or mixture.

[0059] A robot, pump, and / or servo-controlled nozzle dispense the mixture into a mold for the acoustic backing block. The mixture is poured, injected, extruded, or otherwise placed into the mold. In an alternative embodiment, the mixture is poured into the mold manually.

[0060] The mold is shaped to form an acoustic absorber. Its size and shape are based on the transducer or array on which the backing is formed. Other components that are fixed to the backing, such as wires and / or brackets, may also be included in the mold. After creation, the mold may include recesses, extensions, and / or other shapes for backing alignment, machining, or use.

[0061] In another embodiment, sheets of graphene are positioned within a framework by pins, clamps, spacers, and / or fasteners. For example, one clamp holds one end of a sheet, which is then rotated around one or more pegs or rollers and held by another clamp, forming two or more sheets within a mold to form a backer. In another example, individual sheets are clamped in a predetermined orientation. The framework forms or contains the mold. The polymer, in liquid form, is poured or injected into the framework so that the polymer fills the gaps between and / or around the sheets of graphene. This process combines the polymer with the sheets of graphene, with or without additional fillers.

[0062] In another embodiment, a sheet of graphene is combined with a polymer by stacking the sheet with a cured polymer. Multiple molded or cut pieces of cured polymer form parts of a backing block. These pieces are stacked with the sheet to form the backing. For example, three pieces of cured polymer are formed, one of which is flat and two of which are wedge-shaped with a 3-degree angle, as shown in Figure 6. These pieces are stacked with two sheets of graphene, as shown in Figure 6. Additional polymers, clamps, and / or other fasteners may be used to connect the stacks together and / or hold the sheets in place relative to the pieces of cured polymer. In one example, the stacks (laminations) are laminated by being potted together.

[0063] In process 910, the polymer is cured. The mixture poured into the mold is cured. The mold can be sealed, for example, by covering the open top with a plate. The mold is held still or moved (e.g., vibrated) during curing.

[0064] Curing is due to chemical activation. The epoxy hardens, becoming harder or changing from a liquid to a gel or solid state. Alternatively or additionally, heat, pressure, or other energy may be applied to accelerate curing. In one embodiment, a clamp applies pressure to the top plate to ensure size and flatness during curing at 70°C for 12 hours. Other approaches, temperatures, or durations may also be used. Changes in curing properties over time during the slurry curing process may be utilized.

[0065] After curing, the backing composite is removed from the mold. The backing can be machined, such as by grinding, planing, cutting, drilling, punching, and / or other methods to modify it for use. For example, a single plate of cured composite material may be cut to form multiple backing blocks for multiple transducers. Alternatively, a given cured composite from the mold may be used for one or a given transducer.

[0066] When stacking cured polymers, multiple pieces of cured polymer are formed by molding and / or machining for lamination. If the combination with graphene is done before curing (e.g., by mixing graphene flakes with the liquid polymer), the cured polymer becomes a graphene-containing composite. Machining is used to form the backing block.

[0067] The cured polymer provides a support matrix for graphene flakes or sheets. Graphene, as a sheet or flake, is supported by the cured polymer, which acts as its filler and / or holds it in place. The polymer is a matrix for polymer-based composites or backing blocks, with graphene as the filler.

[0068] In process 920, the graphene backing block is positioned relative to or within the transducer stack (for example, relative to a flexible circuit material providing signal electrodes for each element of the array, or relative to a plated PZT layer). Using epoxy, clamps, and / or other connections, the backing is held in place relative to the transducer stack. Each element may be formed after or before the lamination and bonding of the array layer and the backing block.

[0069] Once the transducers are formed (e.g., after bonding and kerfing of the acoustic stack including the backing block), the array becomes ready for ultrasonic scanning and imaging. Based on acoustic impedance, acoustic attenuation, and thermal conductivity, the transducers can be used with additional power (e.g., less prone to overheating) while providing sufficient noise reduction (e.g., absorbing undesirable acoustic energy) and avoiding reflections (e.g., impedance closely matching the transducer elements). Graphene fillers provide predetermined or tuned properties for the backing.

[0070] The following are exemplary embodiments. These exemplary embodiments represent a collection of various aspects and features. Different exemplary embodiments may be combined or combined in other ways as shown below. One type of aspect or feature (e.g., system, backing, or method) may be combined with or used in conjunction with another type.

[0071] Exemplary Embodiment 1: A transducer array system, An array of ultrasonic transducer elements, A transducer array system comprising a polymer framework and a backing comprising one or more sheets of graphene supported by the polymer framework.

[0072] Exemplary Embodiment 2: The polymer framework comprises a cured epoxy, as is the transducer array system of exemplary embodiment 1.

[0073] Exemplary Embodiment 3: The polymer framework comprises a polymer-based composite in which the graphene is embedded within the polymer framework, in an exemplary embodiment 1 or 2 of the transducer array system.

[0074] Exemplary Embodiment 4: The polymer framework comprises a continuous matrix of polymers, and the integrated graphene is located within the continuous matrix, in any of the exemplary embodiments 1 to 3 of the transducer array system.

[0075] Exemplary Embodiment 5: The transducer array system of any of the exemplary embodiments 1 to 4 further comprises a backing containing metal powder supported within the polymer framework.

[0076] Exemplary Embodiment 6: The one or more sheets include at least two sheets separated from each other by at least a portion of the polymer framework, A transducer array system according to any of the exemplary embodiments 1 to 5, wherein each of the sheets has multiple layers of graphene.

[0077] Exemplary Embodiment 7: The one or more sheets include a plurality of separate sheets oriented from front to rear in the polymer framework, A transducer array system according to any of the exemplary embodiments 1 to 6, wherein the front surface is adjacent to the array and the rear surface is on the opposite side.

[0078] Exemplary Embodiment 8: The transducer array system of exemplary embodiment 7, wherein the plurality of separate sheets are at different angles with respect to the front surface.

[0079] Exemplary Embodiment 9: The transducer array system of exemplary embodiment 7 or 8, wherein the plurality of separate sheets are at an angle of 45 to 85 degrees from the front.

[0080] Exemplary Embodiment 10: The transducer array system of any of the exemplary embodiments 7 to 9, wherein the plurality of separate sheets are at an angle of 45 to 85 degrees from the front surface and have varying spacings across the polymer framework.

[0081] Exemplary Embodiment 11: The one or more sheets include two or more sheets that are parallel to the front surface of the polymer framework at an angle of 20 degrees or less. A transducer array system according to any of the exemplary embodiments 1 to 11, wherein the front surface is adjacent to the array, and the two or more sheets are separated by at least a portion of the polymer framework.

[0082] Exemplary Embodiment 12: A transducer array system of exemplary embodiment 11, wherein the first of the two or more sheets is at a non-zero angle and / or not flat with respect to the second of the two or more sheets.

[0083] Exemplary Embodiment 13: The transducer array system of any of the exemplary embodiments 1 to 12, wherein the one or more sheets include a first sheet wound in a helical pattern.

[0084] Exemplary Embodiment 14: An ultrasound imaging probe, probe housing and The lens attached to the probe housing, One or more matching layers are attached to the lens and located within the probe housing, An ultrasonic imaging probe comprising a transducer array system of any of the exemplary embodiments 1 to 13, which is attached to the matching layer and located within the probe housing.

[0085] Exemplary Embodiment 15: Input devices such as keyboards or touchscreens, An ultrasonic imaging probe of exemplary embodiment 14, Display devices and, The system includes the input device, the ultrasonic imaging probe, and one or more processors that communicate with the display device, An ultrasonic imaging system comprising one or more processors that receive inputs from the input device and signals from the ultrasonic imaging probe, and that cause the display device to provide feedback to the user based on the inputs and signals.

[0086] Exemplary Embodiment 16: A method for forming an ultrasonic backing block, Combining graphene flakes or sheets with polymers, This includes curing the polymer combined with the graphene flakes or sheets, A method wherein the cured polymer includes a support matrix that supports the graphene flakes or sheet.

[0087] Exemplary Embodiment 17: The aforementioned combination is To support the graphene flakes or sheets, This includes pouring a polymer as a fluid around the graphene flakes or sheet, The curing method of exemplary embodiment 16 includes curing a polymer to support the graphene flakes or sheet.

[0088] Exemplary Embodiment 18: The aforementioned combination is a method of exemplary embodiment 16 or 17, which includes stacking the graphene flakes or sheets with the cured polymer.

[0089] Exemplary Embodiment 19: An ultrasonic transducer backing block, A cured polymer matrix and graphene in the matrix, Certain curing polymers include a soft polymer, The graphene comprises flakes and is held in a predetermined position in the matrix by the cured polymer surrounding the graphene, in an ultrasonic transducer backing block.

[0090] Exemplary Embodiment 20: An exemplary embodiment 19 of an ultrasonic transducer backing block, wherein the majority of the flakes have a maximum dimension of 400-500 μm.

[0091] Regardless of grammatical usage, the term includes individuals who identify as male, female, or of another gender identity.

[0092] While the present invention has been described with reference to various embodiments, it should be understood that many changes and modifications can be made without departing from the scope of the invention. Therefore, the above detailed description should be understood as illustrative rather than limiting, and it should be understood that the claims, including all equivalents, are intended to define the spirit and scope of the invention.

Claims

1. A transducer array system, An array of ultrasonic transducer elements, A transducer array system comprising a polymer framework and a backing comprising one or more sheets of graphene supported by the polymer framework.

2. The transducer array system according to claim 1, wherein the polymer framework comprises a cured epoxy.

3. The transducer array system according to claim 1, wherein the polymer framework comprises a polymer-based composite in which the graphene is embedded within the polymer framework.

4. The transducer array system according to claim 1, wherein the polymer framework comprises a continuous matrix of polymers, and the integrated graphene is located within the continuous matrix.

5. The transducer array system according to claim 1, wherein the backing further comprises metal powder supported within the polymer framework.

6. The transducer array system according to claim 1, wherein the one or more sheets include at least two sheets separated from each other by at least a portion of the polymer framework, and each of the sheets has a plurality of layers of graphene.

7. The one or more sheets include a plurality of separate sheets oriented from front to rear in the polymer framework, The transducer array system according to claim 1, wherein the front surface is adjacent to the array and the rear surface is on the opposite side.

8. The transducer array system according to claim 7, wherein the plurality of separate sheets are at different angles with respect to the front surface.

9. The transducer array system according to claim 7, wherein the plurality of separate sheets are at an angle of 45 to 85 degrees from the front surface.

10. The transducer array system according to claim 7, wherein the plurality of separate sheets are at an angle of 45 to 85 degrees from the front surface and have varying spacings across the polymer framework.

11. The one or more sheets include two or more sheets that are parallel to the front surface of the polymer framework at an angle of 20 degrees or less. The transducer array system according to claim 1, wherein the front surface is adjacent to the array, and the two or more sheets are separated by at least a portion of the polymer framework.

12. The transducer array system according to claim 11, wherein the first sheet among the two or more sheets is at a non-zero angle with respect to the second sheet among the two or more sheets and / or is not flat.

13. The transducer array system according to claim 1, wherein the one or more sheets include a first sheet wound in a helical pattern.

14. An ultrasound imaging probe, probe housing and The lens attached to the probe housing, Attached to the lens, and comprising one or more matching layers located within the probe housing, An ultrasonic imaging probe comprising the transducer array system according to claim 1, which is attached to the matching layer and located within the probe housing.

15. Input device and, The ultrasonic imaging probe according to claim 14, Display devices and, The system includes the input device, the ultrasonic imaging probe, and one or more processors that communicate with the display device, An ultrasonic imaging system in which one or more processors receive input from the input device and signals from the ultrasonic imaging probe, and cause the display device to provide feedback to the user based on the input and the signals.

16. A method for forming an ultrasonic backing block, Combining graphene sheets with polymers, The process includes curing the aforementioned polymer, A method wherein the cured polymer includes a support matrix that supports the graphene sheet or flakes.

17. The aforementioned combination is To support the graphene sheet, This includes pouring a polymer as a fluid around the graphene sheet, The method according to claim 16, wherein the curing includes curing a polymer to support the graphene sheet.

18. The method according to claim 16, wherein the combination includes stacking the graphene sheet with the cured polymer.

19. An ultrasonic transducer backing block, A cured polymer matrix and graphene in the matrix, The cured polymer is composed of a soft polymer, The graphene comprises flakes and is held in a predetermined position in the matrix by the cured polymer surrounding the graphene, in an ultrasonic transducer backing block.

20. The ultrasonic transducer backing block according to claim 19, wherein the majority of the flakes have a maximum dimension of 400 to 500 μm.

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