Ultrasonic transducer arrays and methods for operating the same

Abstract

Ultrasound transducer arrays, sensors, and methods of operation thereof are disclosed. An ultrasonic transducer array disclosed herein comprises a plurality of sub-apertures, each of the plurality of sub-apertures comprising a plurality of ultrasonic transducer elements, each ultrasonic transducer element of a respective sub-aperture comprising: a first electrical connection common to a group of ultrasonic transducer elements of the plurality of ultrasonic transducer elements within the respective sub-aperture, the first electrical connection configured to electrically connect the ultrasonic transducer elements of the respective group; and a second electrical connection configured to activate the ultrasonic transducer element individually, wherein each ultrasonic transducer element in the respective sub-aperture is individually activable through the first electrical connection of the respective group and the second electrical connection.

Description

ULTRASONIC TRANSDUCER ARRAYS AND METHODS FOROPERATING THE SAMECROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims priority to United States Provisional Patent Application No. 63 / 727,441 , filed on December 3, 2024, the entire contents of which is incorporated by reference herein for all purposes.TECHNICAL FIELD

[0002] The present disclosure relates to ultrasonic transducer arrays, and in particular to design and operation of large-area ultrasonic transducer arrays.BACKGROUND

[0003] Ultrasound systems have traditionally used piezoelectric materials for their transducers since the 1930s. Materials such as piezoelectric crystals (e.g., quartz), ceramics (e.g., lead zirconate titanate (PZT)), and polymers (e.g., polyvinylidene fluoride (PVDF)) have been used as the transducer materials

[0001] . Despite the fact that piezoelectric transducers technology is mature, it faces several drawbacks, particularly in the fabrication of large two-dimensional arrays where interconnection and integration at the die level are challenging [1], Advanced microfabrication techniques offer a promising solution to address these complexities.

[0004] A Micromachined Ultrasound Transducer (MUT) consists of a thin membrane suspended above a cavity. There are two main types of MUTs, which differ in the transduction mechanism: Capacitive Micromachined Ultrasonic Transducers (CMUT) are based on the electrostatic effect, while Piezoelectric Micromachined Ultrasonic Transducers (PMUT) rely on the piezoelectric effect.

[0005] CMUTs are deemed to be an alternative technology to the current piezoelectric-based transducers [1], A CMUT is essentially a parallel-plate capacitor with a fixed electrode at the bottom fixed to a substrate, with a suspended membrane over a cavity and sealed along the edges. A metallic electrode is patterned on top of the suspended membrane. Ultrasound waves are generated by a CMUT when an AC signal superimposed on a DC voltage is applied between both electrodes; alternately,ultrasound waves can be detected by measuring the variation in capacitance of the device while a DC voltage is applied in the presence of incoming ultrasound. Most CMUTs are made of silicon-based materials on a silicon substrate.

[0006] In a PMUT, the vibrating element can comprise a multi-layer structure comprising a piezoelectric thin-film layer metalized on both sides and coupled to an elastic membrane suspended over a cavity. Typically, this structure can cover part of the membrane. If an AC voltage is applied across the electrodes, an electrical field can be generated in the thin-film piezoelectric layer, typically AIN or PZT, which results in stress in the membrane due to the piezoelectric effect. This stress relaxes into a vertical movement of the clamped membrane and thereby generates acoustic waves in the surrounding medium. Vice versa, the piezoelectric effect can also be used to detect acoustic waves impinging on the membrane [2],

[0007] To achieve high-quality 3-D sonography, it is important to develop fully addressed matrix arrays in a rapid, cost-effective, and simplified manner, while reducing the channel count to a level manageable by standard ultrasound systems (e.g. less than 1024 channels). However, transducers systems that can be efficiently and effectively controlled remain limited and lacking.

[0008] Accordingly, additional, alternative, and / or improved ultrasonic transducer arrays, sensors, and methods of operation thereof remain highly desirable.SUMMARY

[0009] In accordance with one aspect of the present disclosure, an ultrasonic transducer array is disclosed, comprising: a plurality of sub-apertures, each of the plurality of sub-apertures comprising a plurality of ultrasonic transducer elements, each ultrasonic transducer element of a respective sub-aperture comprising: a first electrical connection common to a group of ultrasonic transducer elements of the plurality of ultrasonic transducer elements within the respective sub-aperture, the first electrical connection configured to electrically connect the ultrasonic transducer elements of the respective group; and a second electrical connection configured to activate the ultrasonic transducer element individually, wherein each ultrasonictransducer element in the respective sub-aperture is individually activable through the first electrical connection of the respective group and the second electrical connection.

[0010] In some aspects, the second electrical connection of an ultrasonic transducer element in the respective sub-aperture is common to a second electrical connection of an ultrasonic transducer element of a second sub-aperture.

[0011] In some aspects, the second electrical connection is configured to electrically connect the ultrasonic transducer element in the respective sub-aperture and the ultrasonic transducer element of the second sub-aperture.

[0012] In some aspects, the first electrical connection is activatable from an inactive state to an active state; in the inactive state, ultrasonic transducer elements in the group of ultrasonic transducer elements are inactive; and in the active sate, the ultrasonic transducer elements in the group of ultrasonic transducer elements are activatable.

[0013] In some aspects, the ultrasonic transducer array further comprises a switch or multiplexer coupled to the first electrical connection, the switch or multiplexer configured to activate the group of ultrasonic transducer elements.

[0014] In some aspects, the first electrical connection is configured to be deactivated by grounding the first electrical connection via the switch or the multiplexer.

[0015] In some aspects, each of the plurality of sub-apertures is identical in shape, identical in size, identical in an arrangement of ultrasonic transducer elements, or combinations thereof.

[0016] In some aspects, at least two of the plurality of sub-apertures are different in shape, different in size, different in an arrangement of ultrasonic transducer elements, or combinations thereof.

[0017] In some aspects, ultrasonic transducer elements arranged at a same position in each respective sub-aperture are electrically connected.

[0018] In some aspects, the group of ultrasonic transducer elements comprises all ultrasonic transducer elements in the respective sub-aperture.

[0019] In some aspects, the group of ultrasonic transducer elements comprises a subset of the plurality of ultrasonic transducer elements in the respective subaperture.

[0020] In some aspects, the ultrasonic transducer array comprises a plurality of groups of ultrasonic transducer elements within the respective sub-aperture, each of the plurality of groups of ultrasonic transducer elements within the respective subaperture are identical in shape, identical in size, identical in an arrangement of ultrasonic transducer elements, or combinations thereof.

[0021] In some aspects, the ultrasonic transducer array comprises a plurality of groups of ultrasonic transducer elements within the respective sub-aperture, each of the plurality of groups of ultrasonic transducer elements within the respective subaperture are different in shape, different in size, different in an arrangement of ultrasonic transducer elements, or combinations thereof.

[0022] In some aspects, a number of ultrasonic transducer elements in a first group of ultrasonic transducer elements is different from a number of ultrasonic transducer elements in a second group of ultrasonic transducer elements.

[0023] In some aspects, the first and the second electrical connections are electrodes activatable via a DC and / or AC signal.

[0024] In some aspects, the first electrical connection is arranged at a first side of each ultrasonic transducer element and wherein the second electrical connection is arranged at a second side of each ultrasonic transducer element.

[0025] In some aspects, the ultrasonic transducer array comprises a plurality of layers; electrical connections between the ultrasonic transducer elements in each respective sub-aperture is arranged on the plurality of layers; and the electrical connections between the ultrasonic transducer elements arranged on adjacent layers are arranged at an angle with respect to one another.

[0026] In some aspects, the ultrasonic transducer array further comprises conductive fillers arranged between the electrical connections between the ultrasonic transducer elements arranged at the same position relative to the respective sub-aperture within the same layer, the conductive fillers configured for electrical connection to a ground.

[0027] In some aspects, the ultrasonic transducer array further comprises an electrically-conductive grounding material arranged between adjacent layers.

[0028] In some aspects, the arrangement of ultrasonic transducer elements in a respective sub-aperture is a square array, a rectangular array, or a non-orthogonal repeating array.

[0029] In some aspects, ultrasonic transducer element is a capacitive micromachined ultrasonic transducer (CMUT) or a piezoelectric micromachined ultrasonic transducer (PMUT) or a piezoelectric-based ultrasound transducer or other similar ultrasound transducers that requires two or more electrical connections for its operation.

[0030] In accordance with another aspect of the present disclosure, a sensor is disclosed, comprising: a printed circuit board (PCB); and the ultrasonic transducer array of any one of the above aspects, the ultrasonic transducer array is electrically coupled to the printed circuit board; and the second electrical connection is activatable via the PCB and signals from a surface for sensing.

[0031] In some aspects, the PCB is a routing PCB configured to connect second electrical connections between different sub-apertures or different groups of ultrasonic transducer elements. In some aspects, the first electrical connection is routed using the PCB and is activatable via the PCB.

[0032] In some aspects, the ultrasonic transducer array comprises a first side thereof proximal to the first electrical connection and a second side thereof proximal to the second electrical connection; the PCB is arranged between the surface for sensing and the ultrasonic transducer array; and the PCB is arranged more proximal to the second side of the ultrasonic transducer array than the first side of the ultrasonic transducer array.

[0033] In some aspects, the PCB comprises a first side proximal to the ultrasonic transducer array, wherein the second electrical connection of each ultrasonic transducer element is arranged at or below a second side of the PCB opposite the first side.

[0034] In some aspects, the second electrical connection is activatable via a trace embedded in the PCB; and the trace is electrically connected to the second electrical connection.

[0035] In some aspects, the first electrical connection and / or the second electrical connection is electrically coupled to an ASIC using a via.

[0036] In some aspects, the PCB is arranged between the ASIC and the surface for sensing.

[0037] In some aspects, the first connection and / or the second connection is electrically coupled to the ASIC using a plurality of vias arranged between the ultrasonic transducer elements.

[0038] In some aspects, one ultrasonic transducer element within each sub-aperture is configured to function as the via configured to electrically couple the first electrical connection to the ASIC.

[0039] In some aspects, the sensor further comprises: an integrated circuit; the integrated circuit is configured to activate each ultrasonic transducer element of a respective sub-aperture by activating the second electrical connection; and the integrated circuit is configured to activate each group of ultrasonic transducer elements by activating the first electrical connection.

[0040] In some aspects, the ultrasonic transducer array is directly fabricated on the PCB comprising a plurality of layers configured for electrical connections; and individual layers of the plurality of layers are electrically connectable using vias.

[0041] In some aspects, the ultrasonic transducer array is fabricated on a substrate for mounting on the PCB; and the substrate comprises vias configured for electrical connections to and from the ultrasonic transducer array.

[0042] In accordance with another aspect of the present disclosure, a method of operating the ultrasonic transducer array or the sensor of any one of the above aspects is disclosed, comprising: activating one or more ultrasonic transducer elements in a first sub-aperture by: activating one or more first electrical connections corresponding to the one or more groups of ultrasonic transducer elements in the first sub-aperture; and activating one or more second electrical connections of respective ultrasonic transducer elements in the one or more groups of ultrasonic transducer elements in the first sub-aperture.

[0043] In some aspects, the method further comprises: activating one or more ultrasonic transducer elements in a second sub-aperture by: activating one or more first electrical connections corresponding to the one or more groups of ultrasonic transducer elements in the second sub-aperture; and activating one or more second electrical connections of respective ultrasonic transducer elements in the one or more groups of ultrasonic transducer elements in the second sub-aperture.BRIEF DESCRIPTION OF THE DRAWINGS

[0044] Further features and advantages of the present disclosure will become apparent from the following detailed description, taken in combination with the appended drawings, in which:

[0045] FIG. 1A depicts a diagram of a CMUT cell, according to an example embodiment.

[0046] FIG. 1 B depicts a diagram of a polymer-based CMUT, according to an example embodiment.

[0047] FIG. 2 depicts a diagram of an ultrasound transducer element and an ultrasound element array, according to an example embodiment.

[0048] FIG. 3 depicts a diagram of a large matrix array, according to an example embodiment.

[0049] FIGS. 4A, 4B, and 5 depict examples of a cardiac patch using the ultrasound transducer array of FIG. 2 or 3, according to example embodiments.

[0050] FIGS. 6A and 6B depict electrical connections for a plurality of elements in a plurality of sub-apertures of the ultrasound transducer array of FIG. 2 or 3, according to example embodiments.

[0051] FIGS. 6C-6I depict activation of elements in a plurality of sub-apertures in an implementation of the ultrasound transducer array of FIG. 2 or 3, according to an example embodiment.

[0052] FIGS. 7 A and 7B depict electrical connections for routing sub-apertures of the ultrasound transducer array of FIG. 2 or 3, according to example embodiments.

[0053] FIGS. 8A to 8D depict PCB connections for routing sub-apertures of the ultrasound transducer array of FIG. 2 or 3, according to example embodiments.

[0054] FIGS. 9A to 9H depict routing PCBs of the ultrasound transducer array of FIG. 2 or 3, according to example embodiments.

[0055] FIGS. 10A to 11 B depict electrical connections and routing for a routing PCB, according to example embodiments.

[0056] FIGS. 12A and 12B depict a routing PCB with connected to readout electronics boards, according to example embodiments.

[0057] FIG. 13 depicts layers of the ultrasound transducer array of FIGs. 2 or 3, according to an example embodiment.

[0058] FIG. 14 depicts an ultrasound transducer array with overlapping sub-apertures, according to an example embodiment.

[0059] FIG. 15 depicts a signal path for the ultrasound transducer array of FIG. 14, according to an example embodiment.

[0060] FIGS. 16A to 16C depict ultrasound transducer arrays with multi-linear arrays, according to example embodiments.

[0061] FIG. 17 depicts use of the ultrasound transducer arrays in FIGS. 16A to 16C to generate quasi-volumetric images, according to an example embodiment.

[0062] FIG. 18, 19A, and 19B depict the ultrasound transducer array of FIG. 2, 3, 14, or 16A to 16C fabricated directly on PCB substrates, according to an example embodiment.

[0063] FIGS. 20A and 20B depict characterizations of the ultrasound transducer arrays of FIGS. 20B and 20C.

[0064] FIG. 21A depicts an ultrasound transducer on a substrate having vias, according to an example embodiment.

[0065] FIG. 21 B depicts the ultrasound transducer array of FIG. 2, 3, 14, or 16A to 16C mounted on an interposer PCB, according to an example embodiment.

[0066] FIGS. 22A and 22B depict circuit diagrams for the ultrasound transducer array of FIG. 2, 3, 14, or 16A to 16C, according to example embodiments.

[0067] FIGS. 23A to 23D depict ultrasound transducer array patches on a PCB wafer, according to example embodiments.

[0068] FIGS. 24A to 24D depict characterizations of an ultrasound transducer array patch in FIGS. 23A to 23D, according to example embodiments.

[0069] FIG. 25A depicts an ultrasound transducer array patch of FIGS. 23A to 23D mounted on a routing PCB, according to an example embodiment.

[0070] FIG. 25B depicts an ultrasound transducer array patch of FIGS. 23A to 23D mounted on a nosecone, according to an example embodiment.

[0071] FIGS. 26A and 26B depict 3D renders of a probe head and electrical components thereof for use with an ultrasound transducer array patch of FIGS. 23A to 23D, according to example embodiments.

[0072] FIG. 27 depicts an ultrasound transducer array patch of FIGS. 26A and 26B as assembled, according to an example embodiment.

[0073] FIG. 28 depicts a system for using an ultrasound transducer array patch of FIGS. 23A to 23D, according to an example embodiment.

[0074] FIGS. 29A to 29E depict examples of visual images generated using the system of FIG. 28.

[0075] It will be noted that throughout the appended drawings, like features are identified by like reference numerals.DETAILED DESCRIPTION

[0076] The present disclosure describes an ultrasonic transducer array, a sensor comprising an ultrasonic transducer array, and a method of operating the ultrasonic transducer array and / or sensor. In particular, the present disclosure describes a configuration of an ultrasonic transducer array and a subaperture data acquisition scheme that can be used to provide large-area ultrasonic transducer arrays with a reduced number of electrical cables.

[0077] United States patent nos. 10,509,013, 10,564,132, and 10,598,632, the entireties of all of which are hereby incorporated by reference herein, describe the microfabrication of ultrasonic transducers using polymer membranes. These polymer- based CMUTs (polyCMUTs) can in at least some cases operate using lower operating voltages than piezoelectric transducers or silicon-based CMUTs.

[0078] United States patent nos. 10,509,013, 10,564,132, and 10,598,632, the entireties of all of which are hereby incorporated by reference herein, collectively describe two ways of microfabricating polyCMUT arrays: surface micromachining and wafer-bonding. In surface micromachining, the cavity underneath the membrane is created by depositing or growing a sacrificial layer on the carrier substrate. After membrane deposition, the sacrificial layer is removed with an etchant that is specifically chosen to dissolve the sacrificial material via etch channels without damaging the membrane material. In wafer-bonding, the membrane and the cavity can be defined on separate wafers that are bonded together under vacuum conditions. Given that etching channels are not required, the fabrication process can be simplified, and a higher fill factor can be achieved.

[0079] Silicon, silicon nitride and polysilicon are the most popular materials for fabricating CMUT membranes, and chromium and aluminum can be used to pattern electrodes on top of these membranes. These materials are chosen mainly for theirmechanical properties, such that the membranes can be as thin as possible, in order to minimize the effective gap between the bottom and top electrodes. By decreasing the effective gap between electrodes, the electric field can be increased.

[0080] Miniaturized, highly integrated imaging systems using micromachined ultrasound transducers — such as CMUTs — can require advanced interconnect technologies. One such technology is Through Silicon Vias (TSVs), which are vertical electrical interconnects that pass through a silicon wafer or chip. They can offer several advantages, including reduced signal propagation delays, increased bandwidth, and high-density integration and packaging of semiconductor devices. However, traditional TSVs are limited in that they only connect the front and rear of the substrate via a vertical conductive channel. Through Glass Vias (TGVs) work in the same way when glass is used as substrate instead of Silicon, this has the advantage that no electrical insulation layer is required when the vias are created (as opposed to Silicon). TSV or TGV can be used interchangeable throughout this document.

[0081] PolyCMUT arrays can be directly fabricated onto Printed Circuit Boards (PCBs). PCBs facilitate routing in different layers through the use of vias and multilayer construction. Through-hole vias go through the entire thickness of the PCB, connecting all layers. They can be used for components and traces that require strong connections. Blind and buried vias can connect only specific layers of the PCB. Blind vias can connect an outer layer to one or more inner layers, while buried vias connect two or more inner layers. They can allow for more complex routing without affecting the outer layers. Modern PCBs often consist of multiple layers of copper traces separated by insulating material (substrate). The inner layers are sandwiched between the outer layers. Each layer can be used for routing, power planes, or ground planes.

[0082] PCBs can be fabricated using materials such as FR-4 (fiberglass-reinforced epoxy), high-Tg materials for elevated temperatures, flexible materials like polyimide and polyester, rigid-flex materials combining rigidity and flexibility, metal core materials for improved heat dissipation, ceramic materials for high-temperature stability, RF / microwave materials for high-frequency applications, and specializedmaterials like Teflon (PTFE) for specific performance requirements. The choice depends on factors like application, thermal management, frequency, and desired electrical and mechanical properties. PCBs can also contain multiple conductive layers (2 outer layers and a plurality of inner layers); many commercially-available PCBs nowadays can contain as many as 80 conductive layers.

[0083] Low-temperature co-fired ceramic, or LTCC, is a ceramic electronics technology used for ceramic PCB / PCBA fabrication. LTCC, developed from the HTCC (high-temperature co-fired ceramic) technology, is a multilayer low-temperature ceramic PCB manufacturing technology. HTCC is a ceramic based on alumina (AI2O3) and aluminum nitride (AIN). LTCC is a ceramic glass mixed into alumina, and is also called glass ceramics. HTCC substrates can be cured at a temperature of 1500°C or higher. In order to cure at a high temperature, tungsten (W) and molybdenum (Mo), with excellent thermal resistance properties, can be used for the circuit electrodes. For LTCC substrates, the curing temperature can be decreased down to 900°C by mixing glass into the alumina ceramic. Thus, it is possible to use silver or copper, which have low conductivity, for wiring.

[0084] Redistribution layer (RDL) technology can be an integral part of 3D IC integration, especially for 2.5D IC integration with a passive interposer. The RDL can allow for circuitry fan-outs of and allows for lateral communication between the chips attached to the interposer. There are two possible ways to fabricate the RDL, namely (1) polymers to make the passivation and Cu-plating to make the metal layer, and (2) semiconductor back-end-of-line Cu interconnection. It should be noted that the present disclosure can also be generally applicable for RDL technology.

[0085] PCBs fabricated in FR-4 can utilize a composite material of fiberglass and epoxy, offering moderate electrical insulation and mechanical strength, suitable for standard electronics. FR-4 is versatile and cost-effective for general-purpose electronics and can be manufactured by a great number of fabrication facilities around the world. In contrast, PCBs made with LTCC can involve layering ceramic tapes with embedded conductors, resulting in superior electrical properties, high thermal stability, and suitability for high-frequency and high-temperature applications, makingthem ideal for RF modules, microwave devices, and sensors in demanding environments.

[0086] PolyCMUT technology can enable the fabrication of miniaturized 1-D and 2-D transducer arrays directly onto multi-layered PCBs. While 1-D configurations are typically used for linear and phased arrays to produce cross-sectional anatomical scans, 2-D arrays enable volumetric imaging. This can be advantageous because it provides a comprehensive 3-D view of anatomical structures, thereby enhancing spatial and orientational context. This improved visualization can enable more accurate volumetric and distance measurements and enhances diagnostic and prognostic outcomes while reducing reliance on operator expertise.

[0087] Common transducer configurations for 3-D sonography can include full matrix, sparse matrix, wobbler or mechanical-sweep and row-column-addressed (RCA) arrays.

[0088] In conventional matrix arrays, each transducer element can be individually and directly accessible by the backend electronics. This configuration enables full control over the steering and focusing of ultrasound beams in both the azimuthal and elevational directions. However, implementing such a system is highly complex, primarily due to the extensive wiring requirements. For example, a matrix array with 128 elements per dimension would require 16,384 isolated electrical connections guided to the backend, which can be both impractical and cost prohibitive. Additionally, these matrix arrays can be challenging and expensive to fabricate, as the elements can only be accessed from the backside with precise alignment. Consequently, alternative methods are desirable to achieve volumetric imaging while minimizing the required number of channels.

[0089] Sparse matrix arrays use a reduced subset of elements, typically 256 — as supported by most ultrasound systems. These elements can be selected either deterministically or stochastically for both transmission and reception. Although some sparse arrays can maintain a narrow main lobe width similar to that of full matrix arrays, higher side lobe levels may degrade image quality. The reduction in active channels can reduce penetration depth, particularly given the generally small elementsizes in matrix arrays. Optimizing the layout of active elements and managing their switching presents further challenges [3],

[0090] The Row-Column Addressing (RCA) scheme, designed for an N x N matrix array, can reduce the number of required channels by a factor of N / 2. In this approach, all elements in a given row or column can be connected, forming two orthogonal, overlaid linear arrays with large aspect ratio elements. While this allows for focusing and steering in orthogonal directions during both transmission and reception, RCA configurations can be limited by edge artifacts [4] and an inability to achieve two-way focusing or steering, resulting in a limited field of view.

[0091] To achieve high-quality 3-D sonography, it is important to develop a method for fabricating fully addressed matrix arrays in a rapid, cost-effective, and simplified manner, while reducing the channel count to a level manageable by standard ultrasound systems (e.g. < 1024 channels).

[0092] An RCA array, a fully addressed matrix array or other types of 2D arrays can be fabricated in piezoelectric, in CMUTs, and even in PMUTs or other kind of transducers with other materials, like electrostrictive elements, in which a DC and / or AC bias can be used to activate the element.

[0093] There exist in the market some commercially available ultrasound sensors that take advantage of the integrated electronics. For example, the Philips™ X6-1 xMatrix™ ultrasound transducer by Philips™ Inc. has nearly 9,212 piezoelectricbased elements inside its array. Integrating arrays with element-dedicated front-end electronics enables the development of systems with reduced interconnect complexity, enhanced miniaturization, and improved mechanical flexibility, which together facilitate the implementation of micro beamforming. This micro beamforming technique can allow this matrix array to be operated from a standard ultrasound back- end system using fewer wires.

[0094] Another example of high channel number is the Butterfly iQ™ system, which has 8,960 silicon-based CMUT elements fabricated directly on complementary metal- oxide semiconductor (CMOS) structures. This allows the independent operation of theelements to achieve ultrasound beam steering in practically any direction; with the ability to activate and deactivate regions within the transducer area.

[0095] In accordance with the present disclosure, a new manufacturing design of and novel way to operate large-scale ultrasound transducers with a low number of electrical cables is provided. The advantages of this novel approach can be most significantly realized through the CMUT fabrication process, however, it can also be applicable to alternative ultrasound technologies such as bulk piezoelectric / piezoceramic materials, polymer-based CMUTs, PMUTs and electrostrictive materials.

[0096] References are made herein to CMUTs or polyCMUTs; however, CMUTs and polyCMUTs are provided as examples of viable transducer technologies, and other transducer technologies including, but not limited to, piezoceramics, piezocrystals, piezopolymers, piezocomposites, silicon-based CMUTs, other polymer-based CMUTs, PMUTs, and electrostrictive materials are also applicable with regard to the present disclosure.

[0097] The term “Polymer-based Capacitive Micromachined Ultrasonic Transducer” (poly-CMUT or polyCMUT) can refer to a layered ultrasonic device with polymeric membrane containing an embedded upper electrode suspended above a cavity. For example, combined with forming a sufficiently thin CMUT cavity, this structure can permit the CMUT to reach the MHz operative region without requiring unacceptably high operating voltages. PolyCMUT elements may be formed, for example by the methods disclosed in US Patent No. 10,598,632 by Gerardo.

[0098] Some sections of this document describe the manufacturing and operating method of ultrasound arrays fabricated using surface micromachining techniques. The same modes of operation can also hold true if other microfabrication techniques are used, such as wafer bonding, flip chip bonding, among others.

[0099] As used herein, “embedding” an electrode within a polymer layer can refer to completely covering the electrode with the polymer, except for any electrical connections made with that electrode. These connections can be formed before completely embedding the electrode within a polymer layer.

[0100] As used herein, “patterning” a material can refer to selectively remove that material either directly (e.g., if it is photosensitive) or by using a masking layer.

[0101] The sacrificial layer used can be directly deposited onto flat or curved surfaces using spin or spray coating to achieve a highly controllable thickness. This (also polymer-based) sacrificial layer allows for much more flexibility in the fabrication process compared to silicon-based CMUTs, whose sacrificial layers require deposition or growth in high-temperature chambers on specific substrates.

[0102] As used herein, “substrate” can refer to an underlying substance or layer upon which the poly-CMUTs devices are fabricated. Substrates can comprise a range of metallic (e.g., aluminum), non-metallic (e.g., ceramics, composite materials), semiconductors (e.g., silicon) and even polymer-based materials such as polyimide, Kapton™, plexiglass or Lexan™. A substrate can also comprise optically transparent or semitransparent materials such as glass or Indium Tin Oxide (ITO). A substrate can be rigid, semi-rigid or flexible. A substrate can also comprise combinations of the aforementioned options: for example, a piece of glass covered by a layer of indium tin oxide, or a piece of polyimide or FR4 covered by a metallic layer.

[0103] As used herein, “array” can refer to a group of transducer elements aligned side by side in a one-dimensional (1-D) arrangement, multiple linear arrays located side by side (1.5-D) or two-dimensional array (2-D array, often called matrix array) of transducer elements in communication with each other and capable of communication (once connected or active) with user interfaces either by wired communication or wireless signals.

[0104] As used herein “via” can refer to an electrical conductive path created when a hole or opening is plated and / or filled with conductive material. This via hole can connect two or more surfaces in a multi-layer substrate (for example, a printed circuit board (PCB)). These vias can be created mechanically (by using drilling or laser ablation) or chemically (using abrasive materials to etch the substrate in a selective way. These holes can be later electroplated to create the electrically conductive path to form the via. A common material for electroplating is, in some embodiments, copper (Cu). If a hollow via (hole not completely covered by a conductive material) is created,a common filler may be conductive or non-conductive epoxy. This may be done to avoid material contamination and to prevent particles from accumulating in the hollow space. The vias can be plugged-vias, capped vias, through-hole vias, blind vias, buried vias, staggered vias or microvias. Vias can be used in the general PCB industry and can also be applicable to rigid and flexible substrates, including LTCC and HTCC.

[0105] As used herein, “annular ring” can refer to the area of copper pad around a via (either drilled or laser-ablated). All around this via, there should be enough conductive material (such as copper) to form a solid connection between the conductive traces and the via in a multi-layer PCB. Therefore, the main purpose of an annular ring can be to establish a good connection between a via and the conductive trace. In some cases, a via can be created without the need of an annular ring, or the annular ring may be small enough to be comparable to the diameter of a via.

[0106] References are made herein with respect to electrodes, which are provided as examples of electrical connections and are not limited to electrodes. In particular, other suitable electrical connections or contacts for current conductions (e.g. AC and / or DC biasing) and / or signal transmission / reception are viable as well. References are also made herein with respect to matrix arrays, which can be ultrasound transducer arrays or patches. Further, ultrasound and ultrasonic, for example with regard to ultrasound and ultrasonic arrays and elements, may be used interchangeably. References are also made herein with respect to positions and arrangements such as top, bottom, above, or below. It should be noted that positions and arrangements are not restive, and that alternative positions and arrangements are also possible. For example the arrangement of top and bottom electrodes may be reversed, the top and bottom electrodes may be arranged on the same level, etc.

[0107] In accordance with a broad aspect of the present disclosure, an ultrasonic transducer array is disclosed, which can comprise one or more subapertures. Each sub-aperture can comprise a plurality of transducer elements. Each transducer element comprises a first electrical connection and a second electrical connection. The first electrical connection is common to or shared (e.g. shorted) between all transducer elements belonging to a group thereof. Each sub-aperture can comprise a single group (e.g. comprising all of the transducer elements in the sub-aperture) or a plurality of groups each comprising a subset of the transducer elements in the sub-aperture. An electrical signal can be sent and received through the first electrical connection, for example to activate all transducer elements in the group having the shared first electrical connection. The first electrical connection can be activated together or separately via a switch corresponding to each first electrical connection such that individual groups of transducer elements can be activated. The second electrical connection can be unique to each transducer element in the same sub-aperture. That is, each transducer element in the same sub-aperture has different second electrical connections (e.g. each transducer element in the same sub-aperture has its own second electrical connection) such that each transducer element can be individually activated. In some embodiments, the second electrical connection of a transducer element may be common to or shared with a transducer element of a different sub-aperture, for example corresponding to the same position relative to the arrangement of transducer elements in the sub-apertures. This arrangement of second electrical connection may be applied for all transducer elements in all subapertures. For example, element 1 of sub-aperture 1 may share second electrical connection with element 1 of sub-apertures 2, 3, 4... and element 2 of sub-aperture 1 may share second electrical connection with element 2 of sub-apertures 2, 3, 4..., so on and so forth. Specifically, although a number of transducer elements may be activated via the second electrical connection, by activating a particular first electrode corresponding to a particular group (e.g. sub-aperture), only a specific transducer element of the specific sub-aperture is activated.

[0108] Configuring transducer elements in sub-aperture(s) of an ultrasonic transducing array as described herein thus helps to reduce the number of electrical connections required, simplifying the control of the elements and reducing the number of readout channels. The electrical connections may be coupled to a PCB and / or ASIC for signal transmission and activation and may be applied for use as sensors. Singular and groups of transducer elements can be activated by activating the corresponding first and second electrical connections.

[0109] In one embodiment, an ultrasonic transducer array comprises a plurality of sub-apertures, each of the plurality of sub-apertures comprising a plurality ofultrasonic transducer elements. Each ultrasonic transducer element of a respective sub-aperture comprises a first electrical connection common to a group of ultrasonic transducer elements of the plurality of ultrasonic transducer elements within the respective sub-aperture, the first electrical connection configured to electrically connect the ultrasonic transducer elements of the respective group; and a second electrical connection configured to activate the ultrasonic transducer element individually. Each ultrasonic transducer element in the respective sub-aperture is individually activable through the first electrical connection of the respective group and the second electrical connection. In some embodiments, the group of ultrasonic transducer elements comprises all ultrasonic transducer elements in the respective sub-aperture. In other embodiments, the group of ultrasonic transducer elements comprises a subset of the plurality of ultrasonic transducer elements in the respective sub-aperture. There may be a plurality of groups of ultrasonic transducer elements within the respective sub-aperture, which may be identical or different in shape, size, an arrangement of ultrasonic transducer elements, or combinations thereof.

[0110] In some embodiments, the second electrical connection of an ultrasonic transducer element in the respective sub-aperture is common to a second electrical connection of an ultrasonic transducer element of a second sub-aperture; and the second electrical connection is configured to electrically connect the ultrasonic transducer element in the respective sub-aperture and the ultrasonic transducer element of the second sub-aperture.

[0111] As described further herein, each of the plurality of sub-apertures may be identical in shape, identical in size, identical in an arrangement of ultrasonic transducer elements, or combinations thereof. Alternatively, at least two of the plurality of sub-apertures are different in shape, different in size, different in an arrangement of ultrasonic transducer elements, or combinations thereof.

[0112] Embodiments are described below, by way of example only, with reference to FIGS. 1A-29E.

[0113] FIG.1A depicts a Capacitive Micromachined Ultrasound Transducer (CMUT), which can be a microfabricated device used to generate and detect ultrasound waves. The CMUT can comprise a membrane suspended above a cavity,with the bottom of the cavity acting as a fixed electrode 102 and the membrane as a movable electrode 104. When a bias voltage is applied, an electrostatic force can deflect the membrane, and alternating voltage signals can cause the membrane to vibrate, emitting ultrasound waves. Similarly, incoming ultrasound waves can induce vibrations in the membrane, generating electrical signals for detection. The CMUT cell can be fabricated on substrates that are rigid, semi-rigid or flexible. The CMUT cell can also be fabricated on a standard PCB with via holes and electrical contacts on the bottom side

[0114] FIG. 1 B depicts a diagram of a polyCMUT cell, according to an example embodiment. In one embodiment, the CMUT cell can be implemented using a polyCMUT. The CMUT cell can comprise a bottom electrode 102 patterned on a substrate, a cavity area, a first polymer layer (Poly 1), top electrode 104, second polymer layer (Poly 2) and encapsulation layer (parylene).

[0115] FIG. 2 depicts a diagram of an ultrasound transducer element and an ultrasound element array, according to an example embodiment. As shown in FIG. 2, a CMUT element 204 can contain several CMUT cells (202) electrically interconnected by the common (top) electrode 104 (now shown in diagram for clarity). In the case of polyCMUTs, CMUTs and PMUTs in general, a group of cells is the analogy to an element in the piezoelectric world. It is also shown the diagram of an ultrasound element array, also referred to in this document as a “sub-aperture” 206. This sub-aperture 206 can contain a plurality of ultrasound elements 204, arranged in 1 D or 2D.

[0116] FIG. 3 depicts a diagram of a large matrix array of ultrasound transducer elements, according to an example embodiment. A large matrix array 302, for example of an ultrasound transducer array, can also be referred to as a “patch”, containing a plurality of sub-apertures 206 (each containing a plurality of elements), combined to form a large area array. The number of sub-apertures could be as little as 2x2 and as large as 1000x1000. The patch 302 includes electrical connections on the top and bottom electrodes (not shown) described in the subsequent Figures.

[0117] It is worth noting that the materials of the substrate may be capable of withstanding the process conditions for the deposition of silicon, polysilicon, silicon dioxide and silicon nitride layers (above 400°C). The substrate can also be the product of processes like LTCC or HTCC with a plurality of layers.Example Applications

[0118] FIG. 4A depicts an example of a Cardiac patch 402 using the ultrasound Patch of FIG. 3, according to an example embodiment. The advantages of the proposed patch can include, for example, requiring only a fraction of the electrical readout channels to achieve a large scanning area. The patch can also have the capacity to image a large area of a matrix array. It should be noted that the proposed Cardiac patch 402 described requires a minimum number of electrical connections and might include a protective enclosure and additional electronic components (not shown).

[0119] FIG. 4B depicts a similar version of the Cardiac patch aforementioned, according to an example embodiment. In this case, an application-specific integrated circuit (ASIC) 404 can be used to drive all the channels in the Cardiac patch 402. In particular, an ASIC 404 can be fabricated using relatively large process technologies, such as 180nm or 130nm, to reduce costs. The ASIC could be designed to be reusable in such a way that the patch can be replaced for a new one multiple times. The price of these ASIC could be so low that the entire assembly (patch and ASIC) could be considered disposable. The ASIC 404 may also be used for beamforming and data capture, similar to general CMUT applications.

[0120] It will be appreciated that other applications are also possible. For example, the ultrasound transducer array can be used as a cardiac patch or for OB GYN applications, vascular applications, as a bladder scanner, etc.

[0121] Referring to FIG. 5, for simplicity, the term “Patch” 302 refers to the combination of a Routing PCB 408 and a Transducer 406. The transducer 406 of the patch 302 can contain a plurality of sub-apertures 206. The electronic interface is connected externally to the backside of the routing PCB 408. The transducer 406 can be fabricated directly on the Routing PCB 408 or can be fabricated on a separatesubstrate and then soldered to the routing PCB 408. For clarification, the Patch 302 shown in Figure 3 shows the general structure when the transducer 406 and the routing PCB 408 are coupled and are interacting together, but the operational principle is the same. They are shown separately to capture the scenario where the transducer 406 and the routing PCB 408 are manufactured in different substrates. One of the embodiments accounts for the fabrication of the patch directly on the routing PCB 408 (which eliminates the need of a separate transducer component 406).Advantages

[0122] One advantage of the present disclosure is that the number of channels required in the electronic readout circuit is significantly less than the number of electrical channels required to drive a per-element access matrix array.

[0123] Another advantage of the design of the ultrasound transducer array in any of the embodiments can be that a multi-layer PCB fabrication approach can allow the electrical shielding of signal path. For example, individual electrical routing from ultrasound elements can be protected between two grounded planes to minimize electromagnetic interference (EMI).

[0124] The application approach described in any of the embodiments can also be compatible with wafer-bonding fabrication techniques such as those described in US Patents 10,509,013B2, 10,564,132B2 and 10,598,632B1 by Gerardo, Rohling and Cretu. Also, the present disclosure can also be compatible with more traditional chipbonding using solder bumps or similar technologies.EmbodimentsEmbodiment 1 : Fixed sub-aperture ultrasound transducer array

[0125] In embodiments of the present invention, (a capacitive micromachined ultrasound transducer (CMUT) or ultrasound transducer) patch can be implemented on a PCB circuit. The patch can comprise multiple sub-apertures or at least one subaperture, where each sub-aperture (e.g., 206) is a matrix array, such as a 16 x 16 or 32 x 32 or 16 x 32 element (e.g., 204) configuration (element configuration can be anynumber based on the needs). However, the number of elements in the matrix array need not be fixed and can vary based on design specifications.

[0126] In some embodiments of the present invention, the electronic addressing of the capacitive micromachined ultrasound transducer (CM UT) array can be achieved by connecting the signals to the bottom electrodes 102 through traces embedded within the PCB (e.g., a routing PCB). The bottom electrodes 102 of each element may be individually connected to corresponding traces, ensuring separate signal control for each element.

[0127] The routing PCB 408 is the substrate that allows the fixed electrical interconnection of the elements in the patch. The routing PCB can act as an interposer PCB, connecting the transducer and the electronic interface. The routing PCB can also be used as the substrate for direct fabrication of the transducers.

[0128] The top electrode 104 for each sub-aperture 206 can be fabricated on the matrix of elements, and all the top electrodes 104 within a given sub-aperture may be electrically connected (shorted) together. This configuration can allow all elements 204 within a sub-aperture 206 to share a common top electrode 104, while the bottom electrodes 102 remain individually addressable via the PCB, where the connections can be positioned on the opposite side of the PCB. More specifically, a group of elements can share the same top electrode 104 and are all electrically connected such that activating said electrode would activate all elements 204 of the group. The top electrode 104 may be positioned on a first surface or side of the element while the bottom electrode 102 may be positioned on a second surface opposite thereto.

[0129] For a fixed sub-aperture, all elements 204 in the sub-aperture 206 belong to the same group and would all share the same top electrode 104 where the top electrode is unique to each group / sub-aperture. To address each top electrode individually, a switch may be implemented for each top electrode, corresponding to the group of elements as to separate the signal to and from each of the top electrodes. The switch may also be used to ground the respective top electrode and thereby the group of elements corresponding thereto, for example when the group of elements of the top electrode 104 should remain inactive or be deactivated.

[0130] FIGS. 6A and 6B depict electrical connections for a plurality of elements 204 in a plurality of sub-apertures 206, according to example embodiments. For example, each element within a given sub-aperture is connected to its corresponding element in all other sub-apertures, for example via the bottom electrode 102, allowing for a cohesive structure across the entire patch. That is, for different sub-apertures such as those sharing the same general arrangement of elements (e.g. same layout), elements in the same relative position in each sub-aperture may be coupled, for example with the bottom electrode. Other connections via the bottom electrodes are also possible and any element of one sub-aperture may be connected to any element of another sub-aperture. The elements of a given sub-aperture can be individually controlled via top and bottom electrodes 102, 104. In particular, each element 204 in a sub-aperture 206 can have its own bottom electrode 102 such that it is activatable and can send / receive signals individually. The bottom electrode 102 can be shared with elements in different sub-apertures, provided that no elements within the same group or sub-aperture share the bottom electrode. That is, each element may be electrically connected or coupled to a corresponding element in another sub-aperture, repeating for the number of sub-apertures, for example with the number of bottom electrode being the number of elements in each sub-aperture and the number of connected elements for each bottom electrode being the number of sub-apertures.

[0131] Accordingly, each element 204 is individually addressable. For example, to activate a particular element, a signal can be sent to the corresponding bottom electrode as well as the top electrode 104 of the group to which the element belongs to. As such, although the bottom electrodes 102 of elements in other subapertures and top electrodes 104 of other elements in the same group are activated, only the particular element would be activated with all other elements inactive. Similarly, to address a group of elements (e.g. a sub-aperture), a signal can be sent to all the bottom electrodes of each element of the group as well as the top electrode of the group.

[0132] In some embodiments of the present invention, activation of each subaperture may require an AC and / or DC signal for capacitive sensing and measurement. To select and operate a specific sub-aperture 206, a DC (and / or AC)signal can be applied to the top electrode 104, while the signal for measurement or transmission can be addressed through the bottom electrode 102. This approach can allow precise selection and activation of the sub-apertures for signal transmission or reception by controlling the DC (and / or AC) signal on the top electrode 104 in conjunction with the bottom electrode connections. The elements that do not receive any electrical excitation may be considered to be in “idle” mode, a state in which they do not emit or sense any ultrasound waves. The actuation of the electrodes and / or the operations of the switches may be performed using an integrated circuit, such as a microcontroller or FPGA.

[0133] By actuating the top and / or the bottom electrode, an ultrasound wave can be generated for sensing. In sensor applications, the response to the ultrasound sensor wave, for example a response signal or wave, can be perceived by the electronic readout circuit (or ASIC) as a differential signal between the two electrodes. That is, the response signal may be received at the bottom electrode by the electronic readout circuit.

[0134] In some embodiments of the present invention, specific vias within a sub-aperture 206 can be employed to route the top electrodes to the opposite side of the PCB. This design can allow both the top and bottom electrodes of each element to be addressed from the backside of the PCB. The use of vias can ensure that the top electrodes, which are shorted within each sub-aperture, can still be accessed and controlled alongside the individually connected bottom electrodes. This configuration can enable efficient and streamlined electrical addressing of all elements in the patch through a unified backside interface.

[0135] An example implementation is shown in FIGS. 6C to 6I. As shown in FIG. 6C, the ultrasonic transducer array comprises N sub-apertures (206). In this example, each sub-aperture (206) comprises 9 transducer elements (204). The first electrical connection (e.g., top electrode 104) is shared between the 9 elements 204 within the same sub-aperture 206, while the second electrical connection (e.g., bottom electrode 102) is unique for each element 204 in the same sub-aperture 206. However, the second electrical connection for each element is shared with another element in each of the (N) sub-apertures 206. For example, element 1 in sub-aperture1 (A1) shares the same second electrical connection with element 1 in each of the sub-apertures B-N (B1 , ... N1).

[0136] As shown in FIG. 6D, each of the first electrical connection is activable via a switch or multiplexer. Here, each first electrical connection (each sub-aperture) is coupled to and activatable via a switch. In particular, the first electrical connection may comprise two states, an inactive state and an active state. At rest, the first electrical connection may be in the inactive state. In FIG. 6D, the first electrical connection is connected to an “Inactive” connection in the rest or inactive state, in which no power, current, signal, etc. can be received via the first electrical connection (e.g., no circuit completed)_and therefore the corresponding sub-aperture and elements therein. By using the switch, each first electrical connection may be Active (e.g. connected to ground via the switch), thereby completing the circuit and allowing the elements in the sub-aperture to be individually activated via the second electrical connection. In this example, each second electrical connection corresponds to a respective channel. As such, the elements in a sub-aperture are inactive while the first electrical connection is in the inactive state and may be activated while the first electrical connection is in the active state (e.g., grounded using a switch). Other implementations using grounding and DC voltage is as possible, for example as shown in FIGS. 22A and 22B.

[0137] In FIG. 6E, all first electrical connections are inactive and as such no element is active or activatable. FIG. 6F depicts the activation of element 1 in subaperture A (A1 ). To activate this element, the first electrical connection of sub-aperture A in active state (e.g. connected to ground) and the channel for the element (ch. 1 ) is used to individually activate the element. Note that as the circuit is completed at and using the element A1 , it generates a strong acoustic signal during transmission and a large electrical signal during reception. The other elements connected to A1 via the shared second electrical connection (B1 , ... N1) in other sub-apertures will remain inactive or may be slightly actuated (subject to the biasing voltage), they may also generate a very weak acoustic signal during transmission and a very weak electrical signal during reception. However, as the first electrical connections for the other subapertures (B, ... , N) are inactive, the signals that might be generated by the otherelements are negligible in comparison to the one generated by A1 . As such, the other elements can be functionally inactive even though a voltage is applied thereto. The same principle can be applied for the activation of other elements. FIG. 6G depicts the activation of a second element in sub-aperture A (A2). FIG. 6H depicts the activation of a first element in sub-aperture B (B1 ). FIG. 6I depicts the activation of a second element in sub-aperture B (B2).

[0138] FIGS. 7A and 7B depict electrical connections for routing sub-apertures of an ultrasonic transducer array, according to example embodiments. In an embodiment of the present invention, a given sub-aperture can be activated by providing DC bias to its common top electrode 104 via a dedicated electrical routing. In other embodiments, the complexity of the design can be significantly reduced by sacrificing (not connecting) one element within the matrix array of each sub-aperture 402. Instead of using separate routing for the top electrode, this approach can use the selected element’s via to bring the top electrode signal to the backside of the PCB, allowing it to interface with the ASIC or other interface electronics. By doing so, this method can eliminate the need for additional routing paths for the top electrode 104, simplifying the overall layout while still maintaining functionality across the subaperture.

[0139] In the case of MUTs, the interconnection lines (e.g. electrical connections) for each sub-aperture can also be manufactured at the time of microfabrication using, for example, using metal deposition by evaporation or sputtering. For example, a combination of conductive and insulation materials can be used during microfabrication to achieve these interconnections.

[0140] To reduce the complexity of the design without sacrificing an element, an alternative approach can involve introducing additional vias between the matrix elements. These vias can be used to connect the top electrode to the bottom layer, allowing the entire sub-aperture to interface with the ASIC or other electronics on the bottom side. This method can eliminate the need for additional routing paths for the top electrode, simplifying the overall layout while maintaining functionality.

[0141] As depicted in FIG. 7B, a routing strategy designed to reduce the coupling capacitance and crosstalk between the elements by utilizing orthogonal routing between different layers is shown. Specifically, in this method, each routing layer can be oriented orthogonally relative to the layer beneath it, thereby minimizing overlap between the conductive paths of adjacent layers. For example, the connections in the first layer are routed using horizontal lines, while the subsequent layer utilizes vertical lines for the connections. The resulting configuration can minimize signal interference and maintains a compact design within the multilayered structure.

[0142] An example embodiment of electrical connections in a routing PCB is depicted in FIGS. 8A-8D. The “routing PCB” 408 is used with a 2x3 sub-apertures patch. The routing PCB is a substrate where the interconnection between the elements in the patch is made. As described above, this sub-aperture operation is not limited to CMUTs, but it can also be extended to PMUTs and any other ultrasound transducer. Each of the sub-apertures contains a 256 channels (16x16) array. The pitch between the elements in the sub-apertures is 700um.

[0143] FIG. 8A depicts a schematic diagram of the 2x3 routing PCB 408. The common pins in each sub-aperture are connected together. FIG. 8B depicts a schematic diagram of a single sub-aperture 206, there are links to the nodes of other sub-apertures to prevent cluttering in the design. FIG. 8C depicts detailed views of a sub-aperture 206. The pin 1 in sub aperture 1 is connected to pin 1 in the sub apertures 2-6. FIG. 8D depicts PCB layout of the 2x3 sub-aperture patch. The common connection of one of the pins in the 6 sub-apertures is highlighted.

[0144] FIGS. 9Ato 9H depict example routing PCBs. The routing PCB is shown with the footprint to allocate 2 patches (2x3 sub-aperture each) and can be designed in a circular shape. The purpose of this shape is that the same PCB can be used for the direct fabrication of polyCMUT transducers. A diameter of 4in was used for compatibility with the microfabrication equipment in cleanrooms. The routing PCB can be fabricated in a standard PCB house. The current embodiment contains 12 layers and was fabricated in standard FR4 material to reduce costs.

[0145] FIG. 9A depicts 3D rendering of the routing PCB in front view. FIG. 9B depicts 3D rendering of the routing PCB in rearview. FIG. 9C depicts the routing PCB in front view. FIG. 9D depicts the routing PCB in rear view.

[0146] FIGS. 9E and 9F depict the same routing PCB with the internal interconnections. One way to minimize electrical cross-coupling or parasitic capacitance is to extend the interconnection lines to avoid overlapped areas. In such cases, the overall area of the patch is wider than the active area of the transducer (located in the center). FIG. 9E depicts a 3D render of the routing PCB containing space for 2 patches (2x3 sub-apertures each). FIG. 9F depicts routing lines in the routing PCB showing the interconnection of all the sub-apertures.

[0147] The routing PCB can be cut or diced to isolate individual patches, as seen is FIGS. 9G and 9H. The contact pads for only one of the 2x3 sub-apertures is required to interface with the separated (not shown) electronic systems.

[0148] One way to minimize the footprint (area) of the routing PCB is by allowing some overlapping in the interconnection lines. An intermediate ground plane or shield might alleviate the parasitic capacitances or cross-talk. Another option is to fabricate individual shields around the conductor (like a flat coaxial cable), this way the parasitic capacitances and electrical crosstalks can be reduced.

[0149] Another embodiment of a routing PCB is described below with respect to FIGS. 10A and 10B. This embodiment of the routing PCB contains 4x7 subapertures

[0150] FIGS. 10A and 10B depict schematic diagrams of the routing PCB connections. FIG. 10A depicts a schematic diagram of a 4x7 sub-apertures patch and FIG. 10B depicts a schematic diagram of a single sub-aperture and follows a similar connection and nomenclature from the routing board shown on FIGS. 8A and 8B..

[0151] FIGS. 11A and 11 B depict the routing of electrical connections for the PCB. The interconnection lines are implemented in an analogous manner to the embodiment of 2x3 the patch. There is no limit in the number of sub-apertures that can be interconnected. FIG. 11 A depicts a schematic diagram of connection routingin a 4x7 sub-aperture and FIG. 11 B depicts a 3D rendering of a 4x7 sub-aperture patch.

[0152] This routing PCB can allow a direct integration of electronic components mounted at the rear, while the transducer can be fabricated directly on the front face. FIG. 12A depicts a 3D render of a 4x7 sub-aperture routing PCB 1202 in rear view. Headers for the electronic readout can be soldered directly at the rear. FIG. 12B depicts a 3D render of a 4x7 sub-aperture routing PCB 1202 when the readout electronic boards 1204 are assembled at the rear.

[0153] Crosstalk reduction methods in addition to those mentioned above may be implemented. One method to reduce crosstalk between layers can involve introducing polygon copper pours (areas filled with copper) within each layer or between adjacent layers, for example positioned between the routing lines. These copper pours can be connected to a common ground, thereby acting as ground shields. By grounding these polygon pours, the coupling capacitance between the layers can be significantly reduced, as the ground connection effectively breaks down the formation of parasitic capacitors between the routing lines. This configuration can ensure that each layer is connected to the ground, limiting unwanted capacitance and further optimizing the electrical performance.

[0154] Another method for reducing parasitic capacitance between layers can be to insert a ground shield between each routing layer (e.g. adjacent layers), as shown in FIG. 13. In this approach, a routing layer 1302 can be followed by a dedicated ground layer 1303, with the ground shield maintained at zero potential, positioned between the subsequent routing layers 1304. The design and implementation of these ground shields are not restrictive and can effectively minimize parasitic capacitance within the PCB structure, optimizing the overall performance.

[0155] In another embodiment, additional shielding and grounding between the ultrasonic transducer elements can be achieved during the microfabrication process by depositing conductive materials, such as gold, in the spaces between the elements.Embodiment 2: Overlapping sub-aperture ultrasound transducer array

[0156] In some embodiments, the ultrasound transducer array can incorporate overlapping sub-apertures that can sweep freely across the entire array area. This flexibility can allow for the dynamic formation of a moving sub-aperture 302 by selectively activating groups of transducer elements 204 from adjacent fixed subaperture regions 206. Such configuration can increase the sub-aperture density, thereby improving imaging spatial resolution and penetration depth without increasing the overall physical dimensions of the matrix array. As described above, elements 204 within a fixed sub-aperture can share a common top or bottom electrode (e.g. biased for CMUTs, grounded for piezoelectrics), and can be individually excited via pulses applied on opposing electrodes.

[0157] In one embodiment, switches can be implemented on distinct fixed subapertures, with the number of switches corresponding to the number of sub-aperture regions (e.g., Sub. Ap. 1 , Sub. Ap. 2, ... , Sub. Ap. N). This configuration can allow for the direct control of selected elements from different sub-aperture regions for transmitting or receiving signals, provided the total number of active elements does not exceed the number of channels supported by the ultrasound backend system (e.g. equal to the number of elements in a fixed sub-aperture).

[0158] Specifically, each sub-aperture 206 may comprise more than one group of elements 204, for example, via individual switches to control each group of elements comprised therein using the top electrode 104. As such, portions of the subaperture (e.g. elements corresponding thereto) can be activated individually by activating individual group or groups therein. At the same time, other group(s) of elements in other sub-apertures can also be activated using the respective top electrode(s) and switch(es).

[0159] It should also be noted that each group may have the same shape, size, or arrangement of elements therein or have different shape, size, or arrangement of elements therein. Each sub-aperture may comprise groups of the same or different shape, size, or arrangement. For example, a sub-aperture can comprise groups of different size or groups comprising different numbers of elements (e.g. a plurality ofgroups each having at least one element). As another example, a first sub-aperture can comprise a group of 9 elements and a group of 4 elements while a second subaperture can comprise two groups of 4 elements.

[0160] FIG. 14 depicts an ultrasound transducer array with overlapping subapertures, according to an example embodiment. For example, in an 8x8 matrix array with four 4x4 sub-apertures, as illustrated in FIG. 14, each sub-aperture contains 16 elements (E1-E16) that can be activated by biasing / grounding the common electrode and driving the individual elements. However, the active elements are not limited to the same fixed sub-aperture; In the illustrated moving sub-aperture (shown in lighter shade), elements E1 , E2, E3, E5, E6, E7 of Sub. Ap. 4 (1408), E4, E8 of Sub. Ap. 3 (1406), E9, E10, E11 , E13, E14, E15 of Sub. Ap. 2 (1404), and E12 and E16 of Sub. Ap. 1 (1402) are activated while all other elements remain in an idle state e.g. (grounded, floating, or deactivated through other switching methods). The state of float can occur when the contact is electrically isolated, having no defined voltage due to the absence of a low-impedance path to a reference point.

[0161] A signal path diagram for this example is shown in FIG. 15, according to an example embodiment, and can be scaled up to larger systems. The size of the moving sub-aperture can be fixed or variable, depending on the desired operational mode or application.Embodiment 3: Ultrasound transducer array of irregularly shaped of subaperture

[0162] In another embodiment, a transducer system comprises multiple subapertures that can be individually activated to generate a desired acoustic field. The sub-apertures are arranged in a configuration, such as a rectangular or square grid, but can also be activated in non-standard patterns to create custom transducer shapes. This flexibility can allow for the generation of various acoustic field distributions, including diagonal or other specific patterns, tailored to specific applications. By controlling the activation sequence and intensity of the individual subapertures, the transducer can produce a wide range of acoustic outputs.Embodiment 4: Multi-linear ultrasound transducer array

[0163] In another embodiment, multi-linear transducer arrays 1601 can be implemented within sub-apertures 206. The generation of pseudo volumes can be generated by multi-linear arrays located in each of the sub-apertures 206. Instead of having matrix arrays (256ch each) per sub-aperture, a group of small linear arrays 1601 can be used. This can provide further simplification to the overall scheme by: reducing the number of electrical connections needed and reducing needs on the back-end system (126 channels instead of 256 channels).

[0164] A sub-aperture can contain several multi-linear arrays as shown in FIGs. 16A to 16C. Each of the multi-linear arrays 1601 can contain a plurality of elements 204, ranging from 16, 32, 64, etc. the electrical signals for these elements come from the bottom of the array. Examples are shown in FIGS. 16A to 16C, depicting different configurations for multi-linear arrays per sub-aperture. Each sub-aperture can have a plurality of multi-linear arrays.

[0165] Each of the multi-linear arrays can be operated independently from an ultrasound back-end system to obtain individual “slices” (1602). As shown in FIG. 17. Depending on the number of multi-linear arrays per sub-aperture, a simple back-end system can be used to control the entire patch 302 and to be able to generate a volumetric image by using known beamforming and image reconstruction algorithms, such as synthetic aperture techniques.

[0166] These multi-linear arrays can be designed and fabricated on standard PCB wafers containing electrical contact pads at the rear. Each element in the subarrays can have a dedicated contact pad at the rear that allows a simple assembly and connection with readout electronic circuits.

[0167] Several multi-linear arrays (within a sub-aperture) can be excited simultaneously to increase the total acoustic output power during transmission. Time delays can also be added for each multi-linear array to generate a focused wavefront in the elevational direction to mimic the operation of a 1 ,5D or 1 ,7D linear array. This can allow the generation of a 3D ultrasound image. The individual slices 1602 can be post-processed to create compound images using existing reconstruction algorithms. The same ultrasound slices can also be fed to machine learning algorithms toestimate and create a volumetric image, where multiple additional slides can be generated in the interpolated regions at defined angles.

[0168] In particular, each linear array 1601 within a sub-aperture 206 may share the same first electrical connection 104 (e.g., one or more multi-linear arrays activatable via the same switch). The second electrical connection 102 may remain individually addressable. For example, element 1 in the sub-aperture A may be connected to element 1 in sub-aperture B via the second electrical connection. As such, the multi-linear arrays 1601 may require more connections (e.g., wires) than a single linear array, but less wires than a matrix array. Accordingly, each linear array can correspond to a group of elements in a sub-aperture 206.

[0169] Each multi-linear patch may be considered as a matrix patch with “longer” elements. For example, consider a multi-linear array with 2 sub-arrays per sub-aperture 206 (32ch each). For this example, 64 connections are required. The first linear array has elements addressable using Ch1-Ch32, and the second linear array has elements addressable using Ch33-Ch64. Ch1 in sub-aperture A is connected to Ch1 in sub-aperture B-N via the second electrical connection, so on and so forth, with Ch33 in sub-aperture A is connected to Ch33 in sub-aperture B-N.

[0170] As another example, consider a sub-aperture 206 comprising 2 multilinear arrays 1601 (e.g., 64ch each). The first electrical connection 104 forthe 2 multilinear arrays 1601 share the same ground as they are within the same sub-aperture. The elements in the 2 multi-linear arrays 1601 can be controlled by activating or deactivating the channels connected to the second electrical connection 102. In practice, it is possible to energize (e.g., activate) channels 1-64 for the first sub-linear array and t channels 65-128 for the second sub-linear array using the same common ground for the sub-aperture. Advantageously, the linear arrays in the same subaperture can be activated with a time delay in between to slightly steer the beam in the elevational direction (or to do synthetic aperture imaging techniques). In this example, 128 wires are needed per sub-aperture, where a wire is required for each channel (e.g., element). This number is not affected by the number of sub-apertures. For example, for 6 sub-apertures, 128 wires are needed.

[0171] For comparison, consider a single array (64ch) with a sub-aperture 206.All elements share the same first electrical connection 104, which can be activated individually using the second electrical connection 102. However, the beam cannot be steered electronically within the sub-aperture and as such simpler image reconstruction algorithms must be used. In this example, 64 wires are needed per sub-aperture, which is also unaffected by the number of sub-apertures. Therefore, with more multi-linear arrays, more advance image reconstruction techniques are available. However, additional wires may be required.

[0172] The advantage of using multi-linear arrays can be that it requires much less electronic components and computational power than a complete matrix array; reducing the need of heavy computational power and making the development of an ASIC more feasible.Embodiment 5: Direct fabrication of ultrasound transducer arrays on Routing PCBs

[0173] In some embodiments, the ultrasound transducer array 406 can be fabricated directly onto a Routing PCB 408. The PCB design, for example described in embodiment 1 and 2, can be post-processed (e.g. polished) to achieve a planarity and surface roughness similar to a silicon wafer.

[0174] A direct fabrication of the transducer on a routing PCB can provide many benefits to the development, including: faster development cycles and reduced number of steps; no need to solder the transducer to the routing PCB and to the daughterboard; reduced parasitic capacitances; reduced risk of physical damage during soldering; reduced risk of thermal damage to the transducers during soldering; and reduced volume of the assembly.

[0175] WO patent application WO / 2024 / 044853 (CAPACITIVE MICROMACHINED ULTRASONIC TRANSDUCER ARRAYS ON PRINTED CIRCUIT BOARDS), the entire contents of which is incorporated herein by reference, provides examples for the full process of polishing. Any suitable fabrication and polishing techniques, for example as described in WO / 2024 / 044853, could be replicated for the present disclosure. It could be important to have a flat and smooth surface to performmicrofabrication on. The electrical connections of the PCB can be in direct contact with the electrode of the ultrasound transducer.

[0176] FIG. 18 depicts CMUTs 2002 fabricated directly on PCB substrates 2004 after polishing, according to an example embodiment. For example, the inner layers of the PCB can be used for signal distribution, where all the axis (e.g. X, Y and Z) and a plurality of layers (e.g. more than 2) may be used to create the electrical connections. It can also use a combination of via holes 2006, blind via holes for the connection between layers.

[0177] As an example, this proposed scheme of multi-layer design, as depicted in FIG. 20A can highlight the main differences when compared to simple Through- substrate vias (e.g. TSV or TGV), which connect one side of the substrate with the opposite using straight via holes (e.g. along the vertical Y axis).

[0178] One advantage of this proposed methodology can be that no wirebonding or solder-ball bonding is required, which reduces the parasitic resistance and capacitances associated.

[0179] This direct fabrication on PCB methodology can also be applicable for the integration of CMUTs in general, PMUTs and even piezoceramics. In the case of piezoceramic, a conductive adhesive layer might be required to create the bonds between the substrate and the transducer.

[0180] An example embodiment of transducer fabrication on a routing PCB is described below. A routing PCB analogous to those described above can also be used for the direct manufacturing of the patch. An extra 2 layers in the original PCB design can be used to allow a direct fabrication on the top surface and the connection of the headers on the bottom. The top copper layer is polished down to a surface roughness of less than 20nm, similar to the fabrication wafers. FIG. 19A shows a full wafer with 2 patches fabricated in the middle. As depicted, the patch 302 is directly fabricated on a routing PCB, where the substrate is 1 ,2mm thick. There are additional arrays fabricated on the periphery

[0181] Once the microfabrication is complete, the wafer can be diced to isolate the individual patches, the footprint is the same as described above to maintain the compatibility with the electronic back-end circuits. FIG. 19 depicts transducer fabricated directly on a routing PCB after dicing, altogether forming a patch 302.

[0182] The patch was characterized in an impedance analyzer, measuring all the 1536 elements, generating the heat maps (FIGS. 20A and 20B), where only 50 elements were damaged during fabrication and processing. The electrical performance of this transducer may be slightly lower than the one fabricated on PCB wafers. This can be due to the sub-optimal polished surface of the substrate. FIGS. 20A and 20B depict heat maps showing the resonant frequency and the phase angle of the impedance of the transducer fabricated directly on a routing PCB.

[0183] The patch can be assembled to a daughterboard so it can be connected to the readout electronics, for example with an interface for readout electronics. Subsequently, the patch can be connected to an ultrasound back-end system (e.g., Verasonics NXT256) for scanning.Embodiment 6: Ultrasound transducer array with interposer PCB

[0184] In some embodiments, the ultrasound transducer array can be fabricated on other substrates such as (but not limited to) silicon, glass, polymers, or ceramics and then mounted on an interposer PCB having the suitable electrical connections, for example as described in embodiments 1 to 4.

[0185] These substrates on which the ultrasound transducer is fabricated can contain simple through substrate vias (e.g. TSV or TGV) connecting one side of the substrate with the other side of the substrate (e.g. no routing along X-Y axis) as shown in FIG. 21 A, which depicts an ultrasound transducer on a substrate having vias, according to an example embodiment.

[0186] Although FIG. 21 A shows the cross-sectional view of a polyCMUT 2102, it can be replaced by any ultrasound transducer (e.g. CMUTs, PMUTs, piezoceramics, etc.), provided that there is electrical access to the electrode connections on the transducer.

[0187] Once the transducer 2102 is fabricated, it can be mounted on the subaperture matrix array described in embodiment 1 to 4, for example as depicted in FIG. 21 B, which depicts an ultrasound transducer array mounted on an interposer PCB 2104.

[0188] As an example, the interposer PCB 2104 can enable and disable certain regions of the transducer array during operation (e.g. as in embodiments 1 to 4). This approach can be especially useful for those ultrasound transducers that are difficult to be manufactured directly on PCBs, for example as described in embodiment 5.Embodiment 7: Ultrasound transducer array integrated with ASIC

[0189] In some embodiments, it is possible to construct a matrix array (e.g. ultrasound transducer array) with a very high number of elements; however, making electrical connections to all elements can pose significant challenges due to the limited number of channels in conventional imaging systems. This issue can be mitigated by integrating application-specific integrated circuits (ASICs) within the transducer patch, reducing the number of electrical connections required between the probe and the imaging system. A multiplexing strategy can be utilized to reduce cable count, particularly for applications where access is limited. For example, multiplexing can occur between transducer elements and the analog front-end (AFE), where the number of switches can be equal to or greater than the number of elements.

[0190] Several approaches are possible for interfacing large-aperture matrix transducer arrays using fewer cables, including receive sub-array beamforming, programmable high-voltage (HV) pulsers, switch matrices, row-by-row scanning, row- or column-parallel connection schemes, and methods for reducing switching artifacts by creating discharge paths at critical switching moments [5], The ASICs used to interface the matrix array should integrate element-level HV switches or multiplexers in a pitch-matched layout, alongside control logic that can enable selected transducer elements to connect to the transmit (e.g. TX) and receive (e.g. RX) channels of the imaging system. Although this approach is viable, imaging artifacts associated with parasitic transmissions from HV switch actuation during the transitions can be observed [5],

[0191] As a possible solution, the present disclosure can provide a selectable sub-aperture ultrasound system that delivers high-quality imaging while significantly reducing the required channel count. In typical ultrasound imaging system designs, each array element in the active aperture may be associated with a beamforming channel that includes its own analog-to-digital (A / D) converter and beamforming electronics. The "selectability" concept — where array elements are formed by electronically combining smaller transducer elements into sub-apertures — can eliminate redundant beamforming.

[0192] FIG. 22A depicts a circuit diagram for an ultrasound transducer array, according to an example embodiment. As shown in FIG. 22A, the interconnection of nine sub-apertures with nine elements each can be modeled electrically by a single capacitor. The HV control switches for the sub-apertures (e.g. Sub1 , ... , Sub9) can be digitally controlled to activate the desired aperture for imaging. If a sub-aperture is disabled, it can be excluded from imaging, and the corresponding switches either remain open or connected to ground.

[0193] As shown in FIG. 22A, the analog front-end (Amp + ADC) can amplify (e.g. via the voltage or transimpedance amplifiers) and digitize the received echo signals locally, allowing robust transmission to an external imaging system, which can demonstrate the feasibility of in-patch digitization. In accordance with the present disclosure, the number of analog front-end channels and HV transmit / receive switches integrated into the ASIC can be reduced by a factor corresponding to the number of sub-apertures, making the ASIC design more cost-effective and compact. Additionally, the density of wire bonds connecting the ASIC to the PCB can be significantly reduced, improving the reliability and cost-efficiency of the wire bonding process.

[0194] Further, the present disclosure can minimize the impact of non-idealities such as clock feedthrough and charge injection from the HV switches, which generate switching glitches on the transducer element during the transitions, leading to visible imaging artifacts. Addressing these issues can be critical for low-noise detection and high-quality imaging.

[0195] The disclosed ASIC design, which includes local digitization, cablecount reduction, and HV switching optimization, can be equally applicable to other miniature ultrasound patches with varying structures and substrates. This concept can also be applicable to other ultrasound technologies such as CMUTs in general, PMUTs and even piezoelectric transducers.Embodiment 8: Ultrasound transducer array with various biasing options

[0196] In some embodiments, various biasing options can be possible for transducer elements, such as CMUTs. The present disclosure can support both direct and indirect biasing methods. When utilizing the indirect biasing method, for example as shown in FIG. 22A and described above, the sub-aperture switches can be shorted to a biasing circuit to activate the selected sub-aperture, while the remaining subaperture switches can be either floated or shorted to ground.

[0197] For direct biasing, the biasing circuit can be implemented either on-chip or off-chip for each sub-aperture. To activate a selected sub-aperture in this method, the sub-aperture switches can be connected to ground, with the unselected subaperture switches floated, as depicted in FIG. 22B, showing another circuit diagram for an ultrasound transducer array, according to an example embodiment.Embodiment 9: Ultrasound transducer array of different size and shape

[0198] The present disclosure can provide fully addressable matrix arrays, as well as additionally allow for a wide range of transducer configurations to be realized in various embodiments. In one embodiment, traditional linear and phased arrays can be fabricated directly onto the PCB-based substrate. In another embodiment, curvilinear arrays (concave and convex) can be constructed using a thin PCB material. Other embodiments of the present disclosure can support the fabrication of transducer arrays on bendable PCBs. In some embodiments, the transducer arrays may be designed using a row-column addressing scheme or in a sparse array configuration. With the aid of advanced microfabrication techniques, annular or ringshaped arrays can also be readily achievable in certain embodiments.

[0199] The form factor of the transducer arrays and their associated multi-layer interconnection networks can be scalable across various embodiments to accommodate a wide range of applications; from miniaturized devices — on the order of a few millimeters — for example for biomedical applications, such as intravascular or catheter-based ultrasound, to larger monolithic or modular arrays, for example for industrial or aerospace use.Embodiment 10: Ultrasound transducer array with selection options for subapertures and elements

[0200] In some embodiments, the selection of sub apertures may be achieved through methods including, but not limited to, selective biasing (for CMUTs) or grounding (for piezoelectric transducers) of a shared electrode, matrix switch circuits, microelectromechanical switches, diodes, field-effect transistors, or combinations thereof. In some embodiments, optical or mechanical switching may be employed as an alternative to traditional electronic switching. In some embodiments, the selection of sub-apertures may be dynamically controlled by software, firmware, or a combination thereof. This may include the capability to program fixed or variable switching patterns, which can be digitally assigned to the sub-apertures within the transducer array. In other embodiments, the transducer array may determine the appropriate sub-aperture to activate based on a signal voltage threshold defined by specific criteria.

[0201] Similar switching mechanisms can also be applied to transducer elements. I n some cases, groups of transducer elements or individual elements within several sub-apertures may be activated either concurrently or in a controlled sequence-provided that the selected elements do not create channel mapping conflicts, such that the number of activated sub-apertures and elements need not exceed the physical constraints of the hardware, such as the number of available cables and switching mechanisms.Fabrication and testing of an example embodiment of the ultrasound transducer array

[0202] The transducer for a patch (2x3 sub-apertures) was fabricated on a PCB wafer containing electrical vias. The polyCMUT transducers are fabricated on the front side of the wafer and the back-side is fully populated with electrical contact pads. Each element in the transducer is connected to a contact pad by a conductive via. The contact pads will be later soldered to the routing PCB

[0203] FIG. 23A depicts a wafer PCB with 3 patches 2302 (2x3 sub-apertures) fabricated in the center. Additional matrix arrays 2304 (256ch each located on the periphery).

[0204] Once the fabrication is completed, the transducers for the patch 2302 and individual matrix arrays 2304 were diced and separated for processing. FIG. 23B depicts the wafer of FIG. 23A diced into individual arrays including transducers for the 3 patches 2302 and several individual matrix arrays 2304. FIG. 23C depicts patches 2302 being mounted on a holder for post-processing. FIG. 23 D depicts transducer for a 2x3 sub-apertures patch 2302. It contains 1536 individually-addressed polyCMUT elements. Each element can contain a plurality of cells 202.

[0205] Before assembly, each element in the transducers was measured using an impedance analyzer. The graphs in FIGS. 24A and 24B show the measurements results of 256 channels only to avoid overlapping. FIGS. 24A and 24B respectively depict impedance and phase measurements of 256 elements in a patch 2302.

[0206] The entire transducer was characterized using an automated measurement system connected to an impedance analyzer. The plots in FIGS. 24C and 24D show the measurement of the 1536 elements in the (2x3 sub-aperture) transducer patch 2302, which has 256ch per sub-aperture. There were only 16 elements that were damaged during fabrication, this represents 99% of fabrication yield. In FIGS. 24C and 24D, impedance measurements of the patch show a 99% yield and the heat map shows the defective channels.

[0207] The transducers for the patches 2302 were further processed and then soldered to the routing PCB 2504. FIG. 25A depicts a patch 2302 with transducers soldered on a routing PCB 2504. A connector 2506 for the readout electronics was assembled at the rear of the routing board.

[0208] FIG. 25B depicts a nosecone 2508 to house the patch was designed and 3D printed. The front side of the nosecone 2508 has an opening for the active area of the transducer. The routing board and the connector for the readout electronics remain on the inner side. A protective elastomer layer 2510 was cast to prevent mechanical damages to the transducer, this protective layer also prevents water or acoustic gel from going inside the nosecone.

[0209] The patch 2302 with the protective layer 2510 was assembled to a 3D printed housing containing the electronic interface boards. A coaxial cable bundle with 256 cable and sub-aperture control signals come from the back side of the probe. FIGS. 26A and 26B depict 3D renders of the electronic and switching boards 2702 (FIG. 27A) inside the probe head 2704 (FIG. 27B). FIG. 27 depicts a patch 2302 with protective layer assembled with 3D printed body (2704), with electronic interface boards are allocated inside. The entire patch probe and coaxial bundle may be connected to an ultrasound back-end system (e.g. Verasonics NXT2256). This system is capable of driving 256 channels simultaneously. The electronic interface boards are also capable of switching imaging for different sub-apertures in such a way that ultrasound images are acquired sequentially. The setup is shown in FIG. 28.

[0210] FIG. 29A depicts B-mode images from the ultrasound patch (2x3 sub apertures). A quality-assurance ultrasound phantom was used to validate the operation of the ultrasound patch. The ultrasound images were acquired from the top region on the phantom where steel wires are clearly visible in the image. Each of the images were obtained sequentially.

[0211] A single sub aperture (256ch matrix) is capable of generating a volumetric ultrasound image. To test the operation of the patch, a single sub-aperture was excited to obtain a volumetric image of a shallow portion of the same ultrasound phantom in several regions. The volumetric image with cross sectional planes was reconstructed and displayed, where steel wires, hyperechoic and hypoechoic regions in the phantom can be easily visualized.

[0212] The entire patch was used to acquire a large volumetric ultrasound image. FIG. 29B shows how all the 6 sub-apertures from the patch can be used togenerate a large volumetric ultrasound from an ultrasound phantom. Several steel wires and hypoechoic and hyperechoic regions can be observed in a single image, it is worth pointing out the contrast in size with the volumetric images from FIG 29A, the volumetric dataset acquired by the patch is 6 times larger than the acquired by a single matrix array.

[0213] Once the 2D and 3D ultrasound imaging was validated on a clinical phantom, the patch was tested on a volunteer to obtain an image of the carotid artery. The FIGS. 29C and 29D respectively show the 2D short and long axis ultrasound images that the sonographer visualized during the examination. A volumetric image from a single sub-aperture showing the carotid is shown in FIG. 29E. The volume can be easily segmented at arbitrary planes to visualize hidden anatomical structures. In particular, FIG. 29E depicts the reconstructed volumetric image of the carotid artery where a single sub-aperture (1 out of 6) in the patch was used for volume reconstruction.

[0214] It would be appreciated by one of ordinary skill in the art that the system and components shown in the figures may include components not shown in the drawings. For simplicity and clarity of the illustration, elements in the figures are not necessarily to scale and are only schematic. It will be apparent to persons skilled in the art that a number of variations and modifications can be made without departing from the scope of the invention as described herein.

[0215] It is contemplated that any part of any aspect or embodiment discussed in this specification can be implemented or combined with any part of any other aspect or embodiment discussed in this specification, so long as such those parts are not mutually exclusive with each other.

[0216] It should be recognized that features and aspects of the various examples provided above can be combined into further examples that also fall within the scope of the present disclosure.

[0217] When used in this specification and claims, the terms "comprises" and "comprising" and variations thereof mean that the specified features, steps or integers are included. The terms are not to be interpreted to exclude the presence of otherfeatures, steps or components. It will be understood that in embodiments which comprise or may comprise a specified feature or variable or parameter, alternative embodiments may consist, or consist essentially of such features, or variables or parameters. A reference to an element by the indefinite article “a” does not exclude the possibility that more than one of the elements is present, unless the context clearly requires that there be one and only one of the elements.

[0218] Additionally, the term "connect" and variants of it such as "connected", "connects", and "connecting" as used in this description are intended to include indirect and direct connections unless otherwise indicated. For example, if a first device is connected to a second device, that coupling may be through a direct connection or through an indirect connection via other devices and connections. Similarly, if the first device is communicatively connected to the second device, communication may be through a direct connection or through an indirect connection via other devices and connections.

[0219] The invention may also broadly consist in the parts, elements, steps, examples and / or features referred to or indicated in the specification individually or collectively in any and all combinations of two or more said parts, elements, steps, examples, and / or features. In particular, one or more features in any of the embodiments described herein may be combined with one or more features from any other embodiment(s) described herein.

[0220] Use of language such as "at least one of X, Y, and Z," "at least one of X, Y, or Z," "at least one or more of X, Y, and Z," "at least one or more of X, Y, and / or Z," or "at least one of X, Y, and / or Z," is intended to be inclusive of both a single item (e.g., just X, or just Y, or just Z) and multiple items (e.g., {X and Y}, {X and Z}, {Y and Z}, or{X, Y, and Z}). The phrase "at least one of" and similar phrases are not intended to convey a requirement that each possible item must be present, although each possible item may be present.

[0221] In this disclosure term “or” is generally employed in its sense including “and / or” unless the content clearly dictates otherwise.

[0222] In this disclosure the recitation of numerical ranges by endpoints includes all numbers subsumed within that range including all whole numbers, all integers and all fractional intermediates (e.g., 1 to 5 includes 1 , 1.5, 2, 2.75, 3, 3.80, 4, and 5 etc.). In this disclosure the singular forms “an” and “the” include plural referents unless the content clearly dictates otherwise. Thus, for example, reference to a composition containing “a compound” includes a mixture of two or more compounds.References[1] O. Oralkan et al., “Capacitive micromachined ultrasonic transducers: Nextgeneration arrays for acoustic imaging?,” Ultrason. Ferroelectr. Freq. Control IEEE Trans. On, vol. 49, no. 11 , pp. 1596-1610, 2002. [2] A European MEMS Ultrasound Benchmark. White paper published by theECSEL JU project POSITION http: / / position-2.eu / whitepapers / .[3] Ramalli A, Boni E, Roux E, Liebgott H, Tortoli P. Design, Implementation, andMedical Applications of 2-D Ultrasound Sparse Arrays. IEEE Trans Ultrason Ferroelectr Freq Control. 2022 Oct;69(10):2739-2755. doi: 10.1109 / TUFFC.2022.3162419. Epub 2022 Sep 27. PMID: 35333714.[4] Bouzari H, Engholm M, Nikolov SI, Stuart MB, Thomsen EV, Jensen JA. Imaging Performance for Two Row-Column Arrays. IEEE Trans Ultrason Ferroelectr Freq Control. 2019 Jul;66(7): 1209-1221. doi: 10.1109 / TUFFC.2019.2914348. Epub 2019 May 1. PMID: 31056493. [5] Kim, Taehoon, et al. "Design of an ultrasound transceiver ASIC with a switching-artifact reduction technique for 3D carotid artery imaging." Sensors 21.1 (2020): 150.

Claims

CLAIMS:

1. An ultrasonic transducer array, comprising: a plurality of sub-apertures, each of the plurality of sub-apertures comprising a plurality of ultrasonic transducer elements, each ultrasonic transducer element of a respective sub-aperture comprising: a first electrical connection common to a group of ultrasonic transducer elements of the plurality of ultrasonic transducer elements within the respective sub-aperture, the first electrical connection configured to electrically connect the ultrasonic transducer elements of the respective group; and a second electrical connection configured to activate the ultrasonic transducer element individually, wherein each ultrasonic transducer element in the respective subaperture is individually activable through the first electrical connection of the respective group and the second electrical connection.

2. The ultrasonic transducer array of claim 1 , wherein: the second electrical connection of an ultrasonic transducer element in the respective sub-aperture is common to a second electrical connection of an ultrasonic transducer element of a second sub-aperture; and the second electrical connection is configured to electrically connect the ultrasonic transducer element in the respective sub-aperture and the ultrasonic transducer element of the second sub-aperture.

3. The ultrasonic transducer array of claim 1 or claim 2, wherein the first electrical connection is activatable from an inactive state to an active state; wherein, in the inactive state, ultrasonic transducer elements in the group of ultrasonic transducer elements are inactive; andwherein, in the active sate, the ultrasonic transducer elements in the group of ultrasonic transducer elements are activatable.

4. The ultrasound transducer array of claim 3, further comprising: a switch or multiplexer coupled to the first electrical connection, the switch or multiplexer configured to activate the group of ultrasonic transducer elements, wherein the first electrical connection is configured to be activated by grounding the first electrical connection via the switch or the multiplexer.

5. The ultrasonic transducer array of any one of claims 1 to 4, wherein each of the plurality of sub-apertures are identical in shape, identical in size, identical in an arrangement of ultrasonic transducer elements, or combinations thereof.

6. The ultrasonic transducer array of any one of claims 1 to 4, wherein at least two of the plurality of sub-apertures are different in shape, different in size, different in an arrangement of ultrasonic transducer elements, or combinations thereof.

7. The ultrasonic transducer array of any one of claims 1 to 5, wherein ultrasonic transducer elements arranged at a same position in each respective subaperture are electrically connected.

8. The ultrasonic transducer array of any one of claims 1 to 7, wherein the group of ultrasonic transducer elements comprises all ultrasonic transducer elements in the respective sub-aperture.

9. The ultrasonic transducer array of any one of claims 1 to 7, wherein the group of ultrasonic transducer elements comprises a subset of the plurality of ultrasonic transducer elements in the respective sub-aperture.

10. The ultrasonic transducer array of claim 9, comprising a plurality of groups of ultrasonic transducer elements within the respective sub-aperture, wherein each of the plurality of groups of ultrasonic transducer elements within therespective sub-aperture are identical in shape, identical in size, identical in an arrangement of ultrasonic transducer elements, or combinations thereof.11 . The ultrasonic transducer array of claim 9, comprising a plurality of groups of ultrasonic transducer elements within the respective sub-aperture, wherein each of the plurality of groups of ultrasonic transducer elements within the respective sub-aperture are different in shape, different in size, different in an arrangement of ultrasonic transducer elements, or combinations thereof.

12. The ultrasonic transducer array of claim 11 , wherein a number of ultrasonic transducer elements in a first group of ultrasonic transducer elements is different from a number of ultrasonic transducer elements in a second group of ultrasonic transducer elements.

13. The ultrasonic transducer array of any one of claims 1 to 12, wherein the first and the second electrical connections are electrodes activatable via a DC and / or AC signal.

14. The ultrasonic transducer array of any one of claims 1 to 13, wherein the first electrical connection is arranged at a first side of each ultrasonic transducer element and wherein the second electrical connection is arranged at a second side of each ultrasonic transducer element opposite to the first side.

15. The ultrasonic transducer array of claim 14, wherein: the ultrasonic transducer array comprises a plurality of layers; electrical connections between the ultrasonic transducer elements in each respective sub-aperture are arranged on the plurality of layers; and the electrical connections between the ultrasonic transducer elements arranged on adjacent layers are arranged at an angle with respect to one another.

16. The ultrasonic transducer array of claim 15, further comprising conductive fillers arranged between the electrical connections between the ultrasonic transducer elements arranged at the same position relative to the respectivesub-aperture within the same layer, the conductive fillers configured for electrical connection to a ground.

17. The ultrasonic transducer array of claim 15 or claim 16, further comprising an electrically-conductive grounding material arranged between adjacent layers.

18. The ultrasonic transducer array of any one of claims 1 to 17, wherein the arrangement of ultrasonic transducer elements in a respective sub-aperture is a square array, a rectangular array, or a non-orthogonal repeating array.

19. The ultrasonic transducer array of any one of claims 1 to 18, wherein the ultrasonic transducer element is a capacitive micromachined ultrasonic transducer, a piezoelectric micromachined ultrasonic transducer, or a piezoelectric-based ultrasound transducer.

20. A sensor, comprising: a printed circuit board (PCB); and the ultrasonic transducer array of any one of claims 1 to 19, wherein the ultrasonic transducer array is electrically coupled to the printed circuit board; and wherein the second electrical connection is activatable via the PCB and signals from a surface for sensing.

21. The sensor of claim 20, wherein the PCB is a routing PCB configured to connect second electrical connections between different sub-apertures or different groups of ultrasonic transducer elements.

22. The sensor of claim 20 or 21 , wherein the first electrical connection is routed using the PCB and is activatable via the PCB.

23. The sensor of any one of claims 20 to 22, wherein: the ultrasonic transducer array comprises a first side thereof proximal to the first electrical connection and a second side thereof proximal to the second electrical connection;the PCB is arranged between the surface for sensing and the ultrasonic transducer array; and the PCB is arranged more proximal to the second side of the ultrasonic transducer array than the first side of the ultrasonic transducer array.

24. The sensor of any one of claims 20 to 23, wherein the PCB comprises a first side proximal to the ultrasonic transducer array, wherein the second electrical connection of each ultrasonic transducer element is arranged at or below a second side of the PCB opposite the first side.

25. The sensor of any one of claims 20 to 24, wherein: the second electrical connection is activatable via a trace embedded in the PCB; and the trace is electrically connected to the second electrical connection.

26. The sensor of any one of claims 20 to 25, wherein the first electrical connection and / or the second electrical connection is electrically coupled to an ASIC using a via.

27. The sensor of claim 26, wherein the PCB is arranged between the ASIC and the surface for sensing.

28. The sensor of claim 26 or 27, wherein the first electrical connection and / or second connection is electrically coupled to the ASIC using a plurality of vias arranged between the ultrasonic transducer elements.

29. The sensor of claim 28, wherein one ultrasonic transducer element within each sub-aperture is configured to function as the via configured to electrically couple the first electrical connection to the ASIC.

30. The sensor of any one of claims 26 to 28, further comprising an integrated circuit,wherein the integrated circuit is configured to activate each ultrasonic transducer element of a respective sub-aperture by activating the second electrical connection; and wherein the integrated circuit is configured to activate each group of ultrasonic transducer elements by activating the first electrical connection.31 . The sensor of any one of claims 20 to 30, wherein the ultrasonic transducer array is directly fabricated on the PCB comprising a plurality of layers configured for electrical connections; and wherein individual layers of the plurality of layers are electrically connectable using vias.

32. The sensor of any one of claims 20 to 31 , wherein the ultrasonic transducer array is fabricated on a substrate for mounting on the PCB; and wherein the substrate comprises vias configured for electrical connections to and from the ultrasonic transducer array.

33. A method of operating the ultrasonic transducer array of any one claims 1 to 19 or the sensor of any one of claims 20 to 32, comprising: activating one or more ultrasonic transducer elements in a first sub-aperture by: activating one or more first electrical connections corresponding to the one or more groups of ultrasonic transducer elements in the first subaperture; and activating one or more second electrical connections of respective ultrasonic transducer elements in the one or more groups of ultrasonic transducer elements in the first sub-aperture.

34. The method of claim 33, further comprising: activating one or more ultrasonic transducer elements in a second subaperture by:activating one or more first electrical connections corresponding to the one or more groups of ultrasonic transducer elements in the second subaperture; and activating one or more second electrical connections of respective ultrasonic transducer elements in the one or more groups of ultrasonic transducer elements in the second sub-aperture.

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