Ultrasound transducers, arrays including same, systems, and methods of making same

Abstract

In some embodiments, an ultrasonic transducer is provided, the ultrasonic transducer comprising: a membrane configured to generate an ultrasonic vibration; a resonance enhancer configured to be disposed on the membrane; and optionally, a substrate configured to support the membrane wherein the resonance enhancer is made of a material having a natural frequency substantially equal to or close to an activation frequency of the membrane. Other example embodiments are described herein. In some embodiments, the ultrasound transducer provides improved energy conversion efficiency and reduces crosstalk.

Description

Technical Field

[0001] This application relates to ultrasonic transducers, arrays, systems, and methods of manufacturing the same. More particularly, this application relates to micromachined ultrasonic transducers or millimeter ultrasonic transducers, arrays, systems, and methods of manufacturing the same. Background Art

[0002] Ultrasonic transducers (such as micromachined ultrasonic transducers or millimeter ultrasonic transducers) have a wide range of applications in various fields such as medical imaging and sensing (such as ultrasonic imaging and microscopy), therapeutic ultrasound treatment, non-destructive testing, flow measurement, underwater communication, gesture recognition, proximity sensing, obstacle avoidance and distance measurement, tactile devices, industrial inspection, automotive and consumer electronics, etc.

[0003] Currently, there are two main types of micromachined ultrasonic transducers: capacitive micromachined ultrasonic transducers (CMUT) and piezoelectric micromachined ultrasonic transducers (PMUT). CMUT is a type of ultrasonic transducer that uses capacitance-based excitation to convert electrical signals into ultrasonic waves and vice versa.

[0004] PMUT is another type of micromachined ultrasonic transducer that uses the piezoelectric effect to convert electrical signals into ultrasonic waves and vice versa.

[0005] PMUT technology has received significant attention in applications of ultrasonic imaging including medical imaging, industrial inspection, and consumer electronics. Ongoing research focuses on improving PMUT performance, including sensitivity, bandwidth, and integration capabilities.

[0006] Both CMUT technology and PMUT technology represent exciting advancements in ultrasonic transducer design that offer potential improvements in imaging resolution, portability, and integration with electronic systems.

[0007] However, there are some bottleneck problems in the state-of-the-art ultrasonic transducer technology that need to be addressed. For example, in the case of limited ultrasonic energy, traditional ultrasonic transducers can only detect a limited depth with high resolution, or detect a long distance with low resolution. In other words, traditional ultrasonic transducers with limited ultrasonic energy face a dilemma: they can either achieve high resolution but have a limited detection depth, or achieve long-distance detection but with reduced resolution. This trade-off presents a challenge that needs to be solved. For example, in an array of micromachined ultrasonic transducers (MUT), the crosstalk problem seriously affects the performance of the array. This usually results in a complex and expensive manufacturing process for isolating the elements within the array. These problems are common in both capacitive micromachined ultrasonic transducers (CMUT) and piezoelectric micromachined ultrasonic transducers (PMUT).

[0008] Accordingly, there is a pressing need for new or improved components, devices, arrays, and systems, as well as methods for manufacturing components, devices, arrays, and systems for ultrasonic transducers. Summary of the Invention

[0009] In view of the foregoing background, in certain embodiments, the object is to provide improved ultrasonic transducers, arrays, systems, and their components, as well as methods for manufacturing them.

[0010] To solve this problem, in certain embodiments, a novel metamaterial-based resonance enhancer component or element, and an ultrasonic transducer including the resonance enhancer component or element that can be applied to both CMUT and PMUT devices. In certain embodiments, the provided ultrasonic transducer is a type of MUT and can be named XMUT. In certain embodiments, micromachined ultrasonic transducers are described, but similar principles and design methods also apply to other types of ultrasonic transducers, such as millimeter ultrasonic transducers.

[0011] Accordingly, in one aspect, there is provided an ultrasonic transducer including: a membrane configured to generate ultrasonic vibrations; a resonance enhancer configured to be disposed on the membrane; and optionally, a substrate configured to support the membrane, wherein the resonance enhancer is made of a material having an inherent frequency substantially equal to or close to the activation frequency of the membrane.

[0012] In another aspect, there is provided an ultrasonic transducer including: a membrane configured to generate ultrasonic vibrations; a resonance enhancer configured to be disposed on the membrane; and optionally, a substrate configured to support the membrane, wherein the resonance enhancer is made of a material having an inherent frequency substantially equal to or close to the activation frequency of the membrane, and wherein the resonance enhancer includes six columns arranged in a hexagonal pattern to form a membrane vibration region within the six columns.

[0013] In another aspect, there is provided an ultrasonic transducer system including at least one of the above ultrasonic transducers or at least one of the above ultrasonic transducer arrays.

[0014] In another aspect, there is provided a resonance enhancer for an ultrasonic transducer including a membrane configured to generate ultrasonic vibrations, a resonance enhancer configured to be disposed on the membrane, and optionally a substrate configured to support the membrane, wherein the resonance enhancer is made of a material having an inherent frequency substantially equal to or close to the activation frequency of the membrane.

[0015] On the other hand, a method for configuring the above-mentioned resonance enhancer is provided, the method comprising the following steps: (a) determining the operating frequency of the ultrasonic transducer based on one or more of the following parameters: selection of a material for the resonance enhancer, wherein the material has a natural vibration frequency substantially equal to or close to the operating frequency; a height of a column; and / or a diameter of a column, (b) synchronizing the plurality of columns at the operating frequency so as to obtain an amplified mechanical displacement at a membrane vibration region defined by the plurality of columns based on one or more of the following parameters: a geometric arrangement of the plurality of columns; and / or a distance between two adjacent columns; and (c) optimizing the thickness of the membrane to adjust the elastic energy constraint at the membrane vibration region so that the mechanical displacement of the resonance enhancer is maximized.

[0016] On the other hand, a method for manufacturing the above-mentioned ultrasonic transducer is provided, the method comprising the following steps: providing a membrane configured to generate ultrasonic vibrations; providing a resonance enhancer configured to be disposed on the membrane; and optionally, providing a substrate configured to support the membrane, wherein the resonance enhancer is made of a material having a natural frequency substantially equal to or close to an activation frequency of the membrane.

[0017] Other example embodiments will be described below.

[0018] The present disclosure has many advantages. In some embodiments, resonant metamaterials or resonant enhancer components are included in the provided ultrasonic transducers (such as XUTs) to improve energy conversion efficiency and isolate units to reduce crosstalk. In some embodiments, the provided systems include the aforementioned micromachined ultrasonic transducers or arrays connected to a processing chip to achieve parallel signal readout and processing.

[0019] In some embodiments, for the provided methods and apparatus, a resonance enhancer is included in the ultrasonic transducer to improve energy conversion efficiency and isolate the unit to reduce crosstalk. In some embodiments, the provided system includes an array as described in the present disclosure and is connected to a processing chip using through silicon via (TSV) technology. This enables parallel readout and processing, further enhancing the overall performance of the system.

[0020] In some embodiments, at the membrane level, the XMUT achieves high spatial confinement of elastic density energy, with total elastic displacement causing high mechanical vibration amplitude. This results in significant improvements in sound pressure level (SPL) and total sound pressure in the propagation medium (air or liquid). In some embodiments, the provided devices, systems, arrays, and methods provide outstanding levels of improvement times X, where X exceeds 1, 10, or 100 or more.

[0021] This disclosure generally relates to the field of micromachined ultrasonic transducers and / or millimeter ultrasonic transducers, arrays, and systems. More particularly, this disclosure relates to the structure of micromachined ultrasonic transducers and / or millimeter ultrasonic transducers, arrays, and systems. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1A is a schematic diagram of an exemplary ultrasonic transducer with a scalable unit cell resonance enhancer according to an example embodiment, the scalable unit cell resonance enhancer having exemplary pillars arranged in a hexagonal pattern.

[0023] Figure 1B is according to Figure 1A an example embodiment of a cross-sectional schematic diagram of an exemplary ultrasonic transducer.

[0024] Figures 2A to 2C is a schematic diagram of a perspective view, a top view, and a bottom view of an exemplary ultrasonic transducer (or scalable XMUT unit cell) according to the same example embodiment of FIG. 1.

[0025] Figure 3 is a schematic diagram of a side view of an exemplary XMUT including a CMUT and a resonance enhancer having pillars arranged in a hexagonal pattern according to an example embodiment.

[0026] Figure 4 is a schematic diagram of a side view of an exemplary XMUT including a PMUT and a resonance enhancer having pillars arranged in a hexagonal pattern according to an example embodiment.

[0027] Figures 5A to 5B are schematic diagrams of an exemplary XMUT unit cell and a unit cell of a PMUT device (for comparison), respectively.

[0028] Figure 5C shows the variation of the comparison of the absolute total acoustic pressure (Pa) in water with the reduced frequency (f*a) expressed in m / s; wherein, for an exemplary XMUT unit cell and an exemplary PMUT unit cell according to the same example embodiment as shown in Figure 5A and Figure 5B respectively, f is the frequency, and 'a' is the pitch of the pillars.

[0029] Figure 5D shows Figure 6A an enlarged vertical axis, showing the first vibration mode of an exemplary XMUT unit cell and an exemplary PMUT unit cell according to the same example embodiment as shown in Figure 5A and Figure 5B respectively, within the range of f*a = 249 m / s.

[0030] Figure 5E shows, respectively, as in Figure 5A and Figure 5BVariation of the total sound pressure level (SPL) (expressed in dB) of an exemplary XMUT unit cell and an exemplary PMUT unit cell according to the same exemplary embodiment with the reduced frequency (f*a) expressed in m / s.

[0031] Figure 6A The relationship between the reduced frequency and the aspect ratio (height / diameter of the pillar) of the first four vibration modes of an exemplary XMUT with platinum cylindrical pillars is shown.

[0032] Figure 6B The variation of the average value of the total displacement inside the cavity with frequency and the thickness of the membrane is shown.

[0033] Figure 7A The variation of the average value of the total displacement expressed in nm with the reduced frequency (f*a) expressed in m / s is shown; for the inside and outside of the cavity of a scalable XMUT unit cell with pillars.

[0034] Figure 7B The variation of the total displacement expressed in nm with the reduced frequency (f*a) expressed in m / s is shown; for the same device (simulated in Figure 7A ) but without pillars.

[0035] Figure 7C The variation of the stored elastic energy density expressed in J / m 3 with the reduced frequency (f*a) expressed in m / s is shown; for the inside and outside of the cavity of a scalable XMUT unit cell.

[0036] Figure 7D The variation of the stored elastic energy density expressed in J / m 3 with the reduced frequency (f*a) expressed in m / s is shown; for the same device (simulated in Figure 7C ) but without pillars.

[0037] Figure 8 The variation of the average value of the total displacement (nm) with the reduced frequency (f*a) expressed in m / s is shown; for an XMUT array. In this particular case, the unit cells are periodically repeated in a 2D plane, resulting in an m x n array.

[0038] Figure 9A The basic structure for simulating a PMUT unit cell with rigid peripheral conditions to (by design) eliminate crosstalk is schematically shown.

[0039] Figure 9B The simulation results of the Figure 9A cells are shown, presenting the variation of the average value of the total displacement expressed in nm with the reduced frequency (f*a) expressed in m / s for a PMUT.

[0040] Figure 9C shows the average total displacement of an XMUT (with pillars) having conditions identical to those of the device in Figure 9A but without any rigid peripheral conditions. DETAILED DESCRIPTION

[0041] Definitions

[0042] As used herein and in the claims, the term "comprising" (or any related form, such as "comprise" and "comprises"), "including" (or any related form, such as "include" or "includes"), or "containing" (or any related form, such as "contain" or "contains") means including the following elements but not excluding other elements. It should be understood that for each embodiment in which the term "comprising" (or any related form, such as "comprise" and "comprises"), "including" (or any related form, such as "include" or "includes"), or "containing" (or any related form, such as "contain" or "contains") is used, this disclosure / application also includes alternative embodiments in which the term "comprising", "including", or "containing" is replaced by "consisting essentially of" or "consisting of". These alternative embodiments using "consisting of" or "consisting essentially of" are understood to be embodiments of a smaller scope of the "comprising", "including", or "containing" embodiments.

[0043] For clarity, "comprising", "including", "containing", and "having" and any related forms are open terms that allow additional elements or features in addition to the specified essential elements, while "consisting of" is a closed term that is limited to the elements recited in the claim and does not include any elements, steps, or components not specified in the claim.

[0044] For the sake of clarity, "characterized by" or "characterized in that" (along with their related forms as described above) do not limit or change whether the list of terms following them is open or closed in nature. For example, in a claim reciting "an apparatus comprising A, B, C and characterized by D, E and F", the elements D, E and F remain open-ended terms, and since the word "comprising" is used in front of the claim, the claim is intended to cover other elements.

[0045] "Consisting essentially of" limits the scope of the claim to specific materials, components or steps ("basic elements") that do not materially affect the (one or more) essential features of the claimed invention. In some embodiments, the essential features are the (one or more) basic and novel features of the claimed invention.

[0046] As used herein, the singular forms "a / an" and "the" are intended to also include the plural forms unless the context clearly indicates otherwise. When a range is recited in the specification, the range is understood to include each discrete point within the recited range. For example, 1 to 7 means 1, 2, 3, 4, 5, 6, and 7.

[0047] As used herein, the term "about" is understood to be within the normal tolerances of the art and not exceeding ±10% of the stated value. By way of example only, about 50 means from 45 to 55, including all values therebetween. As used herein, the phrase "about" a particular value also includes the particular value, e.g., about 50 includes 50.

[0048] As used herein and in the claims, the terms "substantially" or "substantially" or "essentially" or "basically" mean that the recited characteristics, angles, shapes, states, structures or values need not be precisely achieved, but that deviations or variations (including, for example, tolerances, measurement errors, measurement precision limitations and other factors known to those skilled in the art) may occur in an amount that does not exclude the effect expected from the recited characteristics. For example, an object having a "substantially" cylindrical shape means that the object has an exact cylindrical shape or nearly an exact cylindrical shape. In another example, an object "substantially" perpendicular to a surface means that the object is exactly perpendicular to the surface or nearly exactly perpendicular to the surface, e.g., having a 5% deviation.

[0049] As used herein and in the claims, the terms "close (to)" or "closely (to)" mean that the recited features, angles, shapes, states, structures, or values need not be achieved precisely, but may have deviations or variations. For example, a material having a natural frequency close to the activation frequency will mean that the material has a natural frequency that is either exactly the same as the activation frequency or has a deviation, such tolerance being defined according to actual needs. For example, it has a deviation of 1%, 2%, 3%, 5%, 5%, 6%, 7%, 8%, 9%, 10%, 15%, 30%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70% or more.

[0050] It should be understood that terms such as "top", "bottom", "middle", "side", "length", "inner", "outer", "interior", "exterior", "outer side", "vertical", "horizontal", etc., which may be used herein, merely describe reference points and do not limit the present invention to any particular orientation or configuration. Further, terms such as "first", "second", "third", etc., merely identify one of the multiple parts, components, and / or reference points disclosed herein, and likewise do not limit the present invention to any particular configuration or orientation.

[0051] As used herein and in the claims, the term "ultrasonic transducer" is a device or unit that converts electrical energy (e.g., AC current) into high-frequency sound waves and vice versa. In some examples, the ultrasonic transducer is a micromachined ultrasonic transducer. In some examples, the ultrasonic transducer is a millimeter ultrasonic transducer. In some examples, the ultrasonic transducer is also referred to as an XMUT.

[0052] As used herein and in the claims, the term "membrane" refers to a sheet-like structure, component, or element that includes at least a flexible or deformable region that can vibrate to generate ultrasound or ultrasonic waves.

[0053] As used herein and in the claims, the term "membrane vibration region" refers to the region of the membrane that is configured to vibrate and generate ultrasonic waves. In some examples, if a substrate is present and defines a space with a perimeter, the membrane vibration region may be substantially the same as the region of the membrane covered by the perimeter (i.e., the membrane-covered region). In some examples, columns are arranged around a center to form or define a membrane vibration region therein.

[0054] As used herein and in the claims, the terms "substrate", "support substrate" are meant to refer to a support body for the membrane. In some examples, the substrate includes a defined space with a perimeter.

[0055] As used herein and in the claims, the term "resonant metamaterial" or "resonance enhancer" refers to a structure, element, or component disposed on a membrane and configured to enhance the resonance of an ultrasonic transducer. In some examples, the resonance enhancer is made of a material having an inherent frequency that is substantially equal to or close to the activation frequency of the membrane. In some examples, the resonance enhancer is a plurality of posts or includes a plurality of posts. In some examples, the resonance enhancer is disposed on either side of the membrane. In some examples, the resonance enhancer is a separate component connected to the membrane. In other examples, the resonance enhancer is formed from or extends from the membrane as part of an integral piece with the membrane.

[0056] As used herein and in the claims, the term "post" is a part of the body or structure of a resonance enhancer that is attached to or extends from the membrane. For clarity, the post can have any size and shape.

[0057] As used herein and in the claims, the term "inherent frequency" is the eigenfrequency of a material, and the term "activation frequency" is the specific frequency at which an ultrasonic transducer is driven or excited to generate or detect ultrasonic waves. In some examples, the activation frequency is obtained from experimental data.

[0058] As used herein and in the claims, the term "connect" refers to a direct or indirect joining or linking to other elements. Indirect joining or linking means that one or more additional elements can be present between two elements.

[0059] As used herein, the phrase "operatively connected to" or "operably connected" indicates that two or more elements are connected in a functional manner such that they can cooperate or interact with each other. Such a connection can be a direct connection or an indirect connection, and can be or can not be a physical connection and / or an electrical connection.

[0060] As used herein, the term "electrically communicate" or "electrically connected to" refers to the transmission of information or signals by electrical means. Electrical communication can take various forms, such as a wired connection (e.g., a cable) or a wireless transmission (e.g., Wi-Fi, Bluetooth).

[0061] As used herein, the phrase "electrically connected" or "electrically connected to" refers to an electrical link between two or more electrical components, parts, or devices.

[0062] In certain embodiments, the present disclosure describes a novel micromechanical ultrasonic transducer with a resonance enhancer that can be applied to both capacitive micromechanical ultrasonic transducers (CMUTs) and piezoelectric micromechanical ultrasonic transducers (PMUTs). In certain embodiments, the ultrasonic transducer is referred to as an XMUT. In certain embodiments, for an XMUT, a resonance enhancer is included in the transducer to improve energy conversion efficiency and isolate the unit to reduce crosstalk with a gain exceeding two orders of magnitude. In addition, in certain embodiments, the present disclosure encompasses an array including the aforementioned micromechanical ultrasonic unit cell or composed of the aforementioned micromechanical ultrasonic unit cells. In addition, in certain embodiments, the present disclosure includes a system in which the aforementioned micromechanical ultrasonic transducer or array is connected to a processing chip to achieve parallel signal readout and processing.

[0063] Although the description refers to specific embodiments, this disclosure should not be construed as being limited to the embodiments set forth herein.

[0064] Numbered embodiments

[0065] 1. An ultrasonic transducer comprising: a membrane configured to generate ultrasonic vibrations; a resonance enhancer configured to be disposed on the membrane; and optionally, a substrate configured to support the membrane, wherein the resonance enhancer is made of a material having a natural frequency substantially equal to or close to an activation frequency of the membrane.

[0066] 2. An ultrasonic transducer as described in Example 1, wherein the substrate, if present, defines a space having a perimeter, and wherein the membrane is configured to cover at least the perimeter to form a membrane coverage area.

[0067] 3. The ultrasonic transducer as described in any of the preceding embodiments further comprises: an activation element configured to provide power to generate vibrations on the membrane; and / or a reading element configured to read the vibrations generated on the membrane.

[0068] 4. An ultrasonic transducer as described in any one of Examples 2 to 3, wherein the resonance enhancer includes a plurality of columns.

[0069] 5. An ultrasonic transducer as described in any of the preceding embodiments, wherein the membrane includes an upper surface and an opposite lower surface, and wherein the plurality of pillars are arranged on the upper surface and / or the lower surface.

[0070] 6. An ultrasonic transducer as described in Example 5, wherein the plurality of pillars are arranged around a center at the upper surface or the lower surface so as to form a membrane vibration area within the upper surface or the lower surface.

[0071] 7. The ultrasonic transducer according to any one of Embodiments 5 to 6, wherein the plurality of columns are spaced apart from each other at equal intervals.

[0072] 8. The ultrasonic transducer according to any one of Embodiments 5 to 7, wherein six columns are provided and the six columns are arranged in a hexagonal pattern.

[0073] 9. The ultrasonic transducer according to any one of Embodiments 5 to 8, wherein each column has a transverse cross-section in a shape selected from irregular, rectangular, circular, oval, triangular, hexagonal, or trapezoidal.

[0074] 10. The ultrasonic transducer according to any one of Embodiments 5 to 9, wherein each column has a vertical cross-section in a shape selected from irregular, rectangular, circular, oval, triangular, hexagonal, trapezoidal.

[0075] 11. The ultrasonic transducer according to any one of Embodiments 5 to 10, wherein each column is substantially cylindrical in shape.

[0076] 12. The ultrasonic transducer according to any one of the foregoing embodiments, wherein the material is a metal or an alloy or includes a metal or an alloy.

[0077] 13. The ultrasonic transducer according to any one of the foregoing embodiments, wherein the material is platinum or includes platinum.

[0078] 14. The ultrasonic transducer according to any one of the foregoing embodiments, wherein the ultrasonic transducer is a millimeter ultrasonic transducer or a micromachined ultrasonic transducer.

[0079] 15. The ultrasonic transducer according to Embodiment 14, wherein the ultrasonic transducer is a micromachined ultrasonic transducer selected from the group consisting of a capacitive micromachined ultrasonic transducer (CMUT) and a piezoelectric micromachined ultrasonic transducer (PMUT).

[0080] 16. The ultrasonic transducer according to any one of the foregoing embodiments, wherein the ultrasonic transducer does not include a substrate.

[0081] 17. An ultrasonic transducer, comprising: a membrane configured to generate ultrasonic vibrations; a resonance enhancer configured to be disposed on the membrane; and optionally, a substrate configured to support the membrane, wherein the resonance enhancer is made of a material having an inherent frequency substantially equal to or close to the activation frequency of the membrane, and wherein the resonance enhancer includes six columns arranged in a hexagonal pattern to form a membrane vibration region within the six columns.

[0082] 18. An ultrasonic transducer array, comprising a plurality of ultrasonic transducers according to any one of Embodiments 1 to 17.

[0083] 19. An ultrasonic transducer system further includes an array processing chip, which is configured to be operatively connected to at least one ultrasonic transducer as described in Embodiments 1 to 17 or at least one ultrasonic transducer array as described in Embodiment 18 through through-silicon vias (TSVs) to perform parallel readout and processing.

[0084] 20. A resonance enhancer for an ultrasonic transducer, the ultrasonic transducer including a membrane configured to generate ultrasonic vibrations, a resonance enhancer configured to be disposed on the membrane, and optionally a substrate configured to support the membrane, wherein the resonance enhancer is made of a material having an inherent frequency substantially equal to or close to the activation frequency of the membrane.

[0085] 21. The resonance enhancer as described in Embodiment 20, wherein the resonance enhancer includes a plurality of columns.

[0086] 22. The resonance enhancer as described in Embodiment 21, wherein the plurality of columns are disposed on the upper surface and / or the opposite lower surface of the ultrasonic transducer.

[0087] 23. The resonance enhancer as described in Embodiment 22, wherein the plurality of columns are arranged around a center at the upper surface or the lower surface so as to form a membrane vibration region within the upper surface or the lower surface.

[0088] 24. The resonance enhancer as described in any one of Embodiments 21 to 23, wherein the plurality of columns are spaced apart from each other at equal intervals.

[0089] 25. The resonance enhancer as described in any one of Embodiments 21 to 24, wherein six columns are provided and the six columns are arranged in a hexagonal pattern.

[0090] 26. The resonance enhancer as described in any one of Embodiments 21 to 25, wherein each column has a transverse cross-section in a shape of irregular, rectangular, circular, oval, triangular, hexagonal or trapezoidal.

[0091] 27. The resonance enhancer as described in any one of Embodiments 21 to 26, wherein each column has a vertical cross-section in a shape selected from irregular, rectangular, circular, oval, triangular, hexagonal, trapezoidal.

[0092] 28. The resonance enhancer as described in any one of Embodiments 21 to 27, wherein each column is substantially in a cylindrical shape.

[0093] 29. The resonance enhancer as described in any one of Embodiments 20 to 28, wherein the material is a metal or an alloy or includes a metal or an alloy.

[0094] 30. The resonance enhancer as described in any one of Embodiments 20 to 29, the material is platinum or contains platinum.

[0095] 31. A method of configuring a resonance enhancer as described in any one of Embodiments 20 to 30, the method comprising the steps of: (a) determining the operating frequency of the ultrasonic transducer based on one or more of the following parameters: the selection of the material for the resonance enhancer, wherein the material has a natural vibration frequency that is substantially equal to or close to the operating frequency; the height of the column; and / or the diameter of the column, (b) synchronizing the plurality of columns at the operating frequency based on one or more of the following parameters so as to obtain an amplified mechanical displacement at the membrane vibration region defined by the plurality of columns: the geometric arrangement of the plurality of columns; and / or the distance between two adjacent columns; and (c) optimizing the thickness of the membrane to adjust the elastic energy constraint at the membrane vibration region such that the mechanical displacement of the resonance enhancer is maximized.

[0096] 32. The method as described in Embodiment 31, wherein one or more steps are performed by a numerical study based on finite element simulation (FEM).

[0097] 33. A method of manufacturing an ultrasonic transducer as described in any one of Embodiments 1 to 17, the method comprising the steps of: providing a membrane configured to generate ultrasonic vibrations; providing a resonance enhancer configured to be disposed on the membrane; and optionally, providing a substrate configured to support the membrane, wherein the resonance enhancer is made of a material having a natural frequency that is substantially equal to or close to the activation frequency of the membrane.

[0098] 34. The method as described in Embodiment 33, wherein the method further comprises the steps of: providing an activation element configured to provide power to generate vibrations on the membrane; and / or providing a reading element configured to read the vibrations generated on the membrane. Examples

[0099] Examples are provided herein that more particularly describe certain embodiments of the present disclosure. The examples provided herein are for illustrative purposes only and are not meant to limit the scope of the invention in any way. All references given below and elsewhere in this application are incorporated herein by reference.

[0100] To enable those skilled in the art to better understand the present disclosure, the subject matter of the present disclosure is further illustrated in conjunction with the accompanying drawings and embodiments.

[0101] This disclosure relates to a novel micromachined ultrasonic transducer with an additional resonance enhancer for increasing the transducer efficiency by two orders of magnitude, isolating units, and reducing crosstalk. Further, this disclosure encompasses an array consisting of the aforementioned micromachined ultrasonic transducer with an additional resonance enhancer. Additionally, this disclosure includes a system in which the aforementioned micromachined ultrasonic transducer or array is connected to a processing chip to enable parallel signal readout and processing. XMUT – Example device of an ultrasonic transducer

[0102] In some embodiments, a novel micromachined ultrasonic transducer incorporating an additional resonance enhancer is provided. In some embodiments, such a novel micromachined ultrasonic transducer or its unit cell is designated as an "XMUT". In some embodiments, the natural frequency of the resonance enhancer structure is substantially equal to or close to the vibration frequency of the membrane. At the membrane level, the XMUT achieves a high spatial confinement of elastic density energy, with the total elastic displacement causing a high mechanical vibration amplitude. This results in a significant improvement in the sound pressure level (SPL) and total sound pressure in the propagation medium (such as air or liquid). It is demonstrated in this disclosure that the improvement level reaches X times, where X exceeds 100. Example 1

[0103] Figure 1A and Figure 1B An exemplary ultrasonic transducer (XMUT) 100 using six cylindrical posts 111 is depicted in [reference]. In this example, each of the posts has a circular cross-section over its entire length. The XMUT 100 generally includes a membrane 120 and a resonance enhancer 110 that includes six posts 111 connected to the top surface of the membrane 120. In this example, the six posts 111 have the same size and shape, are substantially cylindrical in shape, and are equally spaced around a central point to form a hexagonal arrangement. The central region defined by the six posts is a membrane vibration region 121 with a cavity displacement portion 112 where ultrasonic vibrations occur. For illustrative purposes, 113 indicates the top surface of the cavity displacement portion 112, and 114 indicates the bottom surface of the cavity displacement portion 112 of the membrane 120. The cavity displacement portion 112 is a temporary deformation of the membrane 120 at the membrane vibration region 121, thereby creating a cavity 115 within it. In this example, the total displacement at the operating frequency is approximately f*a = 250 m / s. Figure 1B A cross-sectional view of the XMUT 100 is shown in [reference]. Example 2

[0104] Figures 2A to 2CThe top view, bottom view, and perspective view of another example XMUT are shown respectively. In this example, the XMUT 200 includes a membrane 220, a resonance enhancer 210, and an optional substrate 240. The resonance enhancer 210 contains a group of columns 211 that are arranged around the center on the upper surface of the membrane, are equally spaced from each other to form a hexagonal arrangement, and form a membrane vibration region 221. This group of columns 211 is also named the "unit cell" of the XMUT device. In this example, six columns 211 are provided, and each column is in the form of a rod, forming the membrane vibration region 221 and the cavity 212. This unit cell can be implemented in various types of ultrasonic transducers, including but not limited to CMUT and PMUT devices. The XMUT can rely on capacitance changes (such as in CMUT) that cause mechanical vibrations (which will be described in more detail in Example 3 and Figure 3 will be described in more detail) or utilize the piezoelectric effect (such as in PMUT) to convert electrical energy into mechanical vibrations and vice versa (which will be described in more detail in Example 4 and Figure 4 will be described in more detail). Then, the unit cell configuration forms the basic element of an array that can be used for different applications.

[0105] Figure 2C Certain parameters of different components are further indicated. For example, the membrane 220 has a thickness indicated as "th"; each of the columns 211 has a diameter indicated as "d"; the distance between two adjacent columns is indicated as "a"; and the height of each column is indicated as "hp". Example 3

[0106] Now turn to Figure 3, another example of an ultrasonic transducer (XMUT) 300 is shown. In this example, the XMUT 300 relies on capacitance changes that cause mechanical vibrations on a membrane 320. In this example, the XMUT 300 generally includes a membrane 320, a support substrate 340, an electrode 350, and a resonance enhancer 310 that includes six posts 311 equally spaced from each other to form a hexagonal arrangement. The six posts 311 are attached to the upper surface of the membrane 320 and create a membrane vibration region 321 at the membrane 320, thus forming a cavity 312. The substrate 340 includes a disk-shaped (or cylindrical) space 341 with an open end on the upper side. The substrate 340 is connected or attached to the membrane 320 to provide support to the membrane 320. The space 341 has a perimeter, an orifice diameter 342, and a depth 343. In this example, the size and shape of the membrane 320 are determined to be large enough to at least cover the open end (perimeter) of the space 341. The membrane 320 is configured to cover the perimeter and enclose the space 341 that houses air. The region above the upper surface of the membrane 320 can be filled with other media, such as water. In this example, the depth 343 is also referred to as an air gap, and this air gap creates a capacitive structure that allows the XMUT 300 to operate based on capacitance changes. In some examples, the membrane is made of a flexible material, such as silicon or polymer material. In this example, the membrane is made of silicon. In some examples, the substrate is made of silicon or glass. 312 indicates a cavity displacement portion (with a top surface 313 and a bottom surface 314 of the membrane 320) that creates a cavity 315 in the medium. In this example, the membrane 320 is electrically connected to the substrate 340 through a series of a power supply 360 (AC power supply) and a voltage controller 370 (bias voltage). When an electrical signal is applied, the membrane vibrates, thus generating ultrasonic waves in both air and liquid that can be used for imaging, sensing, or other applications. The capacitance changes with the movement of the membrane, thus allowing the detection of the reflected ultrasonic waves. Example 4

[0107] Now turning to Figure 4, shows another example ultrasonic transducer XMUT 400. In this example, the XMUT 400 utilizes the piezoelectric effect to convert electrical energy into mechanical vibrations on the membrane 420 or vice versa. In this example, the XMUT 400 generally includes a membrane 420, a support substrate 440, electrodes 450, and a resonance enhancer 410, which includes six columns 411 that are equally spaced from each other to form a hexagonal arrangement. In this example, the six columns 411 are disposed (e.g., attached) on the lower surface of the membrane 420 and define a membrane vibration region 421 therein, thereby creating a cavity 415 and a cavity displacement portion 412 on the opposite upper surface 421 of the membrane 420. The cavity displacement portion 412 has a top surface 313 and a bottom surface 314. The substrate 440 includes a space 441 having an open end at least on the upper side. The space 441 has a perimeter and an orifice diameter 442. In this example, the size and shape of the membrane 420 are determined to be large enough to at least cover the open end (perimeter) on the upper side of the space. The membrane 420 is configured to cover the perimeter and enclose the air-containing space. In this example, the membrane is a piezoelectric layer made of one of a variety of piezoelectric materials. The region above the upper surface of the membrane 420 may be filled with other media, such as water. In some examples, the membrane is made of a flexible material (such as silicon or polymer material). In this example, the membrane 420 is made of silicon. In some examples, the substrate 440 is made of silicon or glass. 413 indicates the cavity displacement portion (having the top surface 413 and the bottom surface 414 of the membrane 420) within the cavity 415 in the medium. In this example, the upper and lower surfaces of the membrane 420 are electrically connected to a power source 460 (AC power source). The power source 460 is configured to apply an electric potential to the XUMT so as to generate charges when subjected to mechanical stress or when the membrane deforms under the applied electric field. When an electrical signal is applied, the piezoelectric material of the membrane deforms, thereby generating ultrasonic waves that can be used for various applications. Example 5

[0108] In this example, the performance between a comparative example ultrasonic transducer XMUT 500 and an example PMUT device 501 will be compared. Figure 5A Schematically shows the basic structure of a classical unit cell of a PMUT device 501 including a membrane 502, a substrate 503, and a vibration region 521. Figure 5B Shows a schematic diagram of an example unit cell of an XMUT similarly including a membrane 520, a substrate 530, and a vibration region 521. Additionally, the XMUT 500 includes a resonance enhancer 510 having columns 511 arranged in a hexagonal pattern disposed on the lower surface of the membrane 520 and surrounding the vibration region 521. Other parameters remain the same. The two unit cells are immersed in a liquid (such as water) as the medium. Then, a finite element method (FEM) simulation is performed for comparison. In this example, the commercially available software COMSOL is used for FEM. The simulation is carried out under the same conditions.

[0109] In one embodiment, an external source in the form of a voltage is applied to the cavity surface, and the voltage varies with frequency. This voltage (electric power) undergoes a conversion process: in the example of a piezoelectric material, the voltage is converted into mechanical vibration by the piezoelectric principle; in the example of a silicon substrate, it depends on capacitance. These vibrations then generate ultrasonic waves in air or water. The acoustic module within FEM COMSOL calculates the resulting sound pressure or sound pressure level for each individual unit cell. The unit cell includes a solid membrane accompanied by six cylindrical posts arranged in a hexagonal configuration. Depending on the application, these posts can be located on the top or the bottom. However, regardless of their placement, the vibrations of the cavity remain consistent. The unit cell has the potential to be replicated periodically in the horizontal plane, thus forming an array.

[0110] Figure 5C The comparison results of the absolute total sound pressure (Pa) in water are shown as a function of the reduced frequency (f*a) expressed in m / s; where, for example XMUT unit cell 500 and example PMUT unit cell 501, f is the frequency and a is the pitch of the posts. Figure 5D Shows Figure 5C the magnified vertical axis of, showing XMUT and PMUT and the first vibration mode in the range of f*a = 250 m / s. Analysis of the simulation results shows that the absolute total sound pressure of the example XMUT unit cell increases by more than two orders of magnitude and twice respectively for the second mode (approximately f*a = 570 m / s) and the first mode (approximately f*a = 250 m / s). In addition, Figure 5E the variation of the total sound pressure level (SPL) (expressed in dB) with the reduced frequency (f*a) expressed in m / s is shown. For example XMUT unit cell 500 and example PMUT unit cell. The results show that when compared with the example PMUT device, example XMUT achieves excellent performance improvement in terms of SPL, corresponding to 6 dB and 40 dB respectively for the first mode and the second mode. It shows that example XMUT unit cell 500 operates using the same size to cover multiple frequencies including low and high frequencies (in this example, 2 operating modes). In this example, two operating frequencies are provided: 250 m / s and 570 m / s. At f*a = 250 m / s, which is close to the operating frequency of example PMUT 501, a 6 dB gain is observed. However, at f*a equal to 570 m / s, another additional operating frequency with a 40 dB gain is provided. The results also show that the excellent improvements of 6 dB and 40 dB correspond to a 2-fold increase in distance and 2^7 = 128-fold respectively. In addition, the results show that example ultrasonic transducer XMUT exhibits a significantly higher quality factor, indicating unexpectedly improved frequency resolution. XMUT - Design and configuration method In Examples 6 to 9 below, unless otherwise specified, the following exemplary ultrasonic transducers with the following parameters will be used: The exemplary ultrasonic transducer generally includes a solid film and six columns as resonance enhancers. The solid film material is lithium niobate with a Y-cut at 128°. The thickness of the solid film (denoted as th) is set to be 0.3 times the center-to-center spacing between two columns represented by 'a'. The six columns are uniform and constructed of platinum. They have a height (hp) of 1.1 times 'a' and a diameter (d) of 0.66 times 'a'. To determine the actual operating frequency, the value of 'a' representing the distance between the centers of the columns is required. For example, if 'a' is selected to be 10 μm, the corresponding parameters will be: th = 3 μm, hp = 11 μm, and D = 6.6 μm. Thus, the initial operating frequency is calculated as f*a = 250, resulting in an operating frequency of f = 25 MHz. Example 6

[0111] In previous examples, it was shown that in the case where the exemplary ultrasonic transducer uses columns in a hexagonal arrangement with a cylindrical shape (having a fixed radius along the length), the exemplary ultrasonic transducer XMUT has improved performance compared to a standard PMUT device. In some examples, various features including geometric features constitute the main design parameters to be considered regarding the performance of the ultrasonic transducer, and these main design parameters include but are not limited to (as shown in Figure 2): The selected materials of the columns, the film, and the substrate (if any); The thickness (th) of the film; The diameter (d) of the columns; The height (hp) of the columns; The distance (a) between two adjacent columns; and / or The placement shape or geometric arrangement of the columns.

[0112] In some embodiments, the selected material of the resonant metamaterial is a metal or alloy or includes a metal or alloy. In one example, the metal is platinum (Pt).

[0113] In some embodiments, the film material is lithium niobate. In one embodiment, the material is lithium niobate with a Y-cut at 128°.

[0114] In some embodiments, the thickness (th) of the film is about 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1.0, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, 2.0, 2.1, 2.2, 2.3, 2.4, 2.5, 2.6, 2.7, 2.8, 2.9, 3.0, 3.1, 3.2, 3.3, 3.4, 3.5, 3.6, 3.7, 3.8, 3.9, 4.0, 4.1, 4.2, 4.3, 4.4, 4.5, 4.6, 4.7, 4.8, 4.9, 5.0, 5.1, 5.2, 5.3, 5.4, 5.5, 5.6, 5.7, 5.8, 5.9, 6.0, 6.1, 6.2, 6.3, 6.4, 6.5, 6.6, 6.7, 6.8, 6.9, 7.0, 7.1, 7.2, 7.3, 7.4, 7.5, 7.6, 7.7, 7.8, 7.9, 8.0, 8.1, 8.2, 8.3, 8.4, 8.5, 8.6, 8.7, 8.8, 8.9, 9.0, 9.1, 9.2, 9.3, 9.4, 9.5, 9.6, 9.7, 9.8, 9.9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30 μm or more. In one example, th is about 0.3 μm.

[0115] In some embodiments, the diameter (d) of the column is about 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1.0, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, 2.0, 2.1, 2.2, 2.3, 2.4, 2.5, 2.6, 2.7, 2.8, 2.9, 3.0, 3.1, 3.2, 3.3, 3.4, 3.5, 3.6, 3.7, 3.8, 3.9, 4.0, 4.1, 4.2, 4.3, 4.4, 4.5, 4.6, 4.7, 4.8, 4.9, 5.0, 5.1, 5.2, 5.3, 5.4, 5.5, 5.6, 5.7, 5.8, 5.9, 6.0, 6.1, 6.2, 6.3, 6.4, 6.5, 6.6, 6.7, 6.8, 6.9, 7.0, 7.1, 7.2, 7.3, 7.4, 7.5, 7.6, 7.7, 7.8, 7.9, 8.0, 8.1, 8.2, 8.3, 8.4, 8.5, 8.6, 8.7, 8.8, 8.9, 9.0, 9.1, 9.2, 9.3, 9.4, 9.5, 9.6, 9.7, 9.8, 9.9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30 μm or more. In one example, d is about 6.6 μm.

[0116] In some embodiments, the height (hp) of the pillar is about 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1.0, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, 2.0, 2.1, 2.2, 2.3, 2.4, 2.5, 2.6, 2.7, 2.8, 2.9, 3.0, 3.1, 3.2, 3.3, 3.4, 3.5, 3.6, 3.7, 3.8, 3.9, 4.0, 4.1, 4.2, 4.3, 4.4, 4.5, 4.6, 4.7, 4.8, 4.9, 5.0, 5.1, 5.2, 5.3, 5.4, 5.5, 5.6, 5.7, 5.8, 5.9, 6.0, 6.1, 6.2, 6.3, 6.4, 6.5, 6.6, 6.7, 6.8, 6.9, 7.0, 7.1, 7.2, 7.3, 7.4, 7.5, 7.6, 7.7, 7.8, 7.9, 8.0, 8.1, 8.2, 8.3, 8.4, 8.5, 8.6, 8.7, 8.8, 8.9, 9.0, 9.1, 9.2, 9.3, 9.4, 9.5, 9.6, 9.7, 9.8, 9.9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30 μm or more. In one example, a is about 11 μm. In some embodiments, the distance (a) between two pillars is about 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1.0, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, 2.0, 2.1, 2.2, 2.3, 2.4, 2.5, 2.6, 2.7, 2.8, 2.9, 3.0, 3.1, 3.2, 3.3, 3.4, 3.5, 3.6, 3.7, 3.8, 3.9, 4.0, 4.1, 4.2, 4.3, 4.4, 4.5, 4.6, 4.7, 4.8, 4.9, 5.0, 5.1, 5.2, 5.3, 5.4, 5.5, 5.6, 5.7, 5.8, 5.9, 6.0, 6.1, 6.2, 6.3, 6.4, 6.5, 6.6, 6.7, 6.8, 6.9, 7.0, 7.1, 7.2, 7.3, 7.4, 7.5, 7.6, 7.7, 7.8, 7.9, 8.0, 8.1, 8.2, 8.3, 8.4, 8.5, 8.6, 8.7, 8.8, 8.9, 9.0, 9.1, 9.2, 9.3, 9.4, 9.5, 9.6, 9.7, 9.8, 9.9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30 μm or more. In one example, a is about 10 μm.In some embodiments, the geometric arrangement of the pillars is pentagonal, hexagonal, irregular, etc.

[0117] In some examples, the selection of the materials and geometric features used are some of the main design parameters of the ultrasonic transducer. In this example, a design method is provided that aims to adjust the design parameters in order to obtain a desired operating mode of the ultrasonic transducer. For a given material used, the "hp" and "d" parameters are used to define the operating frequency of the mechanical mode of the pillars. The parameter "a" is used to adjust the mechanical coupling between adjacent pillars in order to obtain a synchronization effect. The membrane thickness "th" is used to adjust the elastic energy confinement inside the cavity. Thus, in this example, the design process follows the following method:

[0118] Step 1: The first step of the design method involves determining the mechanical vibration frequencies of the device. These operating frequencies are associated with the natural vibration modes of the individual pillars, as Figure 6A shown. This figure shows the variation of the operating frequency with the aspect ratio of the pillars. For example, an isolated cylindrical pillar exhibits several vibration modes, where the bending mode is typically the lowest of the frequencies adjusted using the "d" and "hp" parameters. This optimization is carried out through a numerical study based on finite element simulation (FEM).

[0119] Step 2: In order to obtain an amplified mechanical displacement at the center of the cavity, synchronization is required between the pillars at a given frequency set by Step 1. In the case of pillars arranged in a hexagonal pattern, the shape of the placement of these pillars around the cavity is another design parameter shown in parameter "a" of Figure 2. This synchronization enables the generation of an extraordinarily amplified mechanical displacement at the center (cavity) of the hexagon that is several orders of magnitude greater than the typical displacement of the membrane. This phenomenon causes a significant confinement of the elastic energy within the cavity. This optimization is carried out through a numerical study based on finite element simulation (FEM).

[0120] Step 3: The third step of the design method involves optimizing the thickness of the membrane that supports the pillars in order to achieve the maximum mechanical displacement at the given frequency set by Steps 1 to 2, as Figure 6B shown. This optimization is carried out through a numerical study based on finite element simulation (FEM).

[0121] Figure 6A Shows how the reduced frequencies of the first four vibration modes of an exemplary platinum cylindrical pillar vary with respect to its relative height. The results show the scaled frequencies of the various vibration eigenmodes with respect to the scaled height of the exemplary platinum pillar. For a height-to-diameter ratio of 1, the initial branch represents the bending mode, followed by the extensional mode, the compression mode, and finally the second harmonic of the bending mode. In this example, the FEM of COMSOL software is used to calculate the eigenfrequency modes of an individual platinum cylinder. This analysis involves varying the height and diameter of the pillar to obtain the results.

[0122] Figure 6B Shows the variation of the average value of the total displacement inside the cavity with frequency and the thickness of the membrane. XMUT cell isolation and crosstalk Example 7

[0123] To analyze the unit isolation of an ultrasonic transducer, the performance of the unit cells of an exemplary ultrasonic transducer XMUT and an exemplary PMUT in terms of their internal and external cavity characteristics was studied. In one example, a resonance enhancer is located on the lower surface of the membrane of the unit cell, and the inside of the cavity refers to the region inside the resonance enhancer, similar to those described in Example 5.

[0124] Figure 7A Presents a graph showing the variation of the average value of the total displacement expressed in nm with the reduced frequency (f*a) expressed in m / s; for the inside and outside of the cavity of an exemplary XMUT unit cell. In the case of the first vibration mode, the average displacement inside the cavity was measured as 45x10 -9 m, while the average displacement outside the cavity was 40x10 -11 m. This significant reduction in displacement by two orders of magnitude inside and outside the cavity demonstrates the unexpectedly effective isolation of the unit cell achieved by the resonance enhancer. To further demonstrate the role of the pillars in the spatial confinement of mechanical displacement in the XMUT device, Figure 7B Shows the variation of the average value of the total displacement expressed in nm with the reduced frequency (f*a) expressed in m / s; for Figure 7A a similar ultrasonic transducer as in -9 but without pillars. The average displacement inside the cavity was measured as 3x10 -10 m, while the average displacement outside the cavity was measured as 2x10

[0125] To demonstrate the role of the pillars in the spatial confinement of the stored energy density (including all mechanical vibrations of the structure) in the XMUT device, Figure 7C Shows the variation of the stored elastic energy density expressed in J / m 3 with the reduced frequency (f*a) expressed in m / s; for the inside and outside of the cavity of a scalable XMUT unit cell. The results show a significant enhancement of two orders of magnitude in the stored elastic energy for the exemplary ultrasonic transducer XMUT. Figure 7D Shows the variation of the stored elastic energy density expressed in J / m 3 with the reduced frequency (f*a) expressed in m / s; for Figure 7CThe device in [description] but without pillars. Additionally, the internal energy ratio of the cavity of the exemplary XMUT and PMUT (without pillars) with resonance enhancers exceeds 100. These results indicate that the resonance enhancer significantly increases the elastic energy inside the cavity by isolating the unit and reducing crosstalk. XMUT array

[0126] The results from the previous examples indicate that the exemplary XMUT has the ability to isolate the unit and reduce crosstalk. In some examples, the exemplary XMUT array including multiple XMUT unit cells provides the benefits of enhanced spatial resolution and reduced crosstalk. Additionally, each unit cell within the array can be individually excited or read out, resulting in array-based applications.

[0127] In conventional PMUT and CMUT structures, the cavity of each unit is defined by the open holes in the supporting substrate. In contrast, in some examples, the cavity of the provided ultrasonic transducer is defined by the pillar array boundary (e.g., the membrane vibration region) without the need for any supporting substrate. In other words, in some examples, the ultrasonic transducer does not require and thus does not include a supporting substrate but can still generate ultrasonic waves. This will result in a simplified manufacturing process for the ultrasonic transducer and a lower production cost for the single-layer system. Example 8

[0128] Figure 8 Shows the out-of-plane displacement (nm) as a function of the reduced frequency (f*a) in m / s; for the exemplary XMUT array. In this example, the unit cells are periodically repeated in the 2D plane, resulting in an m x n array. Figure 8 The results depicted in [description] indicate that the array induces additional coupling modes between the units, but the energy levels are not significant compared to the first mode. Examples of the additional coupling modes are Figure 8 shown in [description] at the characteristic frequencies of f*a = 340 m / s and f*a = 460 m / s, while the first mode corresponds to approximately f*a = 370. 810, 830, and 820 respectively show the corresponding states of the exemplary ultrasonic transducer at the characteristic frequencies of f*a = 340 m / s, f*a = 460 m / s, and f*a = 370. Example 9

[0129] Now refer to Figure 9A and Figure 9B , in this example, the exemplary structure of the exemplary PMUT 900 has a rigid peripheral feature to eliminate crosstalk (by design). In this example, the diameter of the PMUT 900 is 4*a / 3, the thickness is a / 15, and it is made of the material lithium niobate. Figure 9B Shows Figure 9AThe simulation results of the unit cells show the variation of the average total displacement in nm with the reduced frequency (f*a) in m / s. The results indicate that for a 1V excitation, the maximum value of the average total displacement is 3.5*10 -11 m( Figure 9B ). To compare this result with the example ultrasonic transducer XMUT device, Figure 9C the out-of-plane displacement of the example XMUT is shown, which has exactly the same conditions as the device in Figure 9A but without any rigid peripheral conditions. For the example XMUT device, for a 1V excitation, the maximum value of the average out-of-plane displacement obtained is 45*10 -9 m, resulting in an improvement of more than two orders of magnitude.

[0130] In summary, the provided example XMUT array can effectively reduce crosstalk, isolate the units, and enhance the spatial resolution. All these unexpected improvements in performance have been demonstrated using an exemplary combination of an array of cylindrical pillars in a hexagonal arrangement on a piezoelectric membrane.

[0131] The ultrasonic transducer has a cavity defined by the boundaries of the pillar array without any support substrate. This results in a simplified manufacturing process for a single-layer system. The ultrasonic transducer array is formed by at least one ultrasonic transducer.

[0132] The resonant metamaterial structure of the array is placed in a way that isolates the unit cells and reduces crosstalk between the ultrasonic transducers through high spatial confinement of elastic energy.

[0133] The activation device on each unit cell can generate a signal independently of the other units in the array; and the readout device on each unit can read the vibration on the membrane independently of the other units in the array.

[0134] The exemplary embodiments of the present invention have thus been fully described. Although the description refers to specific embodiments, it will be apparent to those skilled in the art that the present invention can be practiced with variations of these specific details. Therefore, the present invention should not be construed as limited to the embodiments set forth herein.

[0135] The devices / methods discussed in different figures can be added to the methods in other figures or exchanged with the methods in other figures. Further, data values of specific numerical values (such as specific quantities, numbers, categories, etc.) or other specific information should be interpreted as illustrative for discussing the example embodiments. Such specific information is not provided to limit the example embodiments.

[0136] For example, in some embodiments, the pattern or geometric arrangement of the positions of the pillars is hexagonal, but it can also take different arrangements, such as rectangular (square), pentagonal, heptagonal, octagonal, decagonal, polygonal, irregular, etc.

[0137] For example, the lateral / vertical cross-section of each pillar of the ultrasonic intensifier can take different shapes, including but not limited to circular, oval, square, hexagonal, irregular (with or without rounded corners). For example, a pillar in the shape of a rod or cylinder can be a non-uniform structure with different cross-sectional sizes along the vertical axis / horizontal axis (the base and the top of the pillar). This can achieve additional design freedoms to define different vibration modes. For example, if the shape of the pillar changes from circular to oval, the first bending vibration frequency can degenerate into two frequencies. This can achieve additional design freedoms to define different vibration modes.

[0138] For example, the sizes of the ultrasonic intensifier and the ultrasonic transducer can be scaled to a larger or smaller size according to actual needs (such as according to the user-defined response time and resonance frequency).

[0139] For example, the resonance enhancer of the ultrasonic transducer is arranged such that different pillar shapes and placement patterns (geometric arrangements) are used to isolate / define unit cells and reduce crosstalk between different unit cells, as described in some examples. In some examples, multiple ultrasonic transducers with different sizes, shapes, and arrangements can be used to form an array or a system.

[0140] For example, in some embodiments, the resonance enhancer is fabricated on one side (the upper surface or the lower surface) of the membrane, where the cavity displacement part is on the same side, but in other examples, the cavity displacement part (for inducing wave propagation) is obtained on both sides or opposite sides of the membrane.

[0141] For example, in some embodiments, the ultrasonic intensifier includes six identical cylindrical pillars, but different types, other numbers (e.g., two, three, four, five, six, seven, eight, nine, ten or more), sizes (e.g., extra-large), and shapes (irregular, rectangular, circular, oval, triangular, hexagonal, or trapezoidal) with different arrangements can be used.

[0142] A variety of manufacturing methods can be utilized to construct the XMUT device. The method selected for connecting the pillars to the membrane depends on the scale of the XMUT determined by its operating frequency. For nano- and micro-sized pillars, dedicated MEMS cleanroom facilities are necessary for the manufacturing process. Techniques such as physical vapor deposition, chemical vapor deposition, spin coating, electroplating, and electrochemical deposition can be combined with etching to construct the pillar structure. For pillars larger than sub-millimeter size, techniques such as additive manufacturing and methods such as adhesive bonding or ultrasonic welding become viable options.

[0143] For example, in some embodiments, a substrate is provided to support the membrane, but in other embodiments, the ultrasonic transducer does not include a substrate.

Claims

1. An ultrasonic transducer, comprising: a membrane configured to generate ultrasonic vibrations; a resonance enhancer configured to be disposed on the membrane; and optionally, a substrate configured to support the membrane, wherein the resonance enhancer is made of a material having an inherent frequency substantially equal to or close to the activation frequency of the membrane.

2. The ultrasonic transducer according to claim 1, wherein, The substrate, if present, defines a space having a perimeter, wherein the membrane is configured to at least cover the perimeter to form a membrane-covered region.

3. The ultrasonic transducer according to any one of the preceding claims, further comprising: an activation element configured to provide power to generate vibrations on the membrane; and / or a reading element configured to read the vibrations generated on the membrane.

4. The ultrasonic transducer according to any one of claims 2 to 3, wherein The resonance enhancer includes a plurality of columns.

5. The ultrasonic transducer according to any one of the preceding claims, wherein, The membrane includes an upper surface and an opposite lower surface, and wherein the plurality of columns are disposed on the upper surface and / or the lower surface.

6. The ultrasonic transducer according to claim 5, wherein, The plurality of columns are disposed around a center at the upper surface or the lower surface so as to form a membrane vibration region within the upper surface or the lower surface.

7. The ultrasonic transducer according to any one of claims 5 to 6, wherein, The plurality of columns are equally spaced from each other.

8. The ultrasonic transducer according to any one of claims 5 to 7, wherein, Six columns are provided, and the six columns are arranged in a hexagonal pattern.

9. The ultrasonic transducer according to any one of claims 5 to 8, wherein, Each column has a transverse cross-section having a shape selected from irregular, rectangular, circular, oval, triangular, hexagonal, or trapezoidal.

10. The ultrasonic transducer according to any one of claims 5 to 9, wherein Each column has a vertical cross-section having a shape selected from irregular, rectangular, circular, oval, triangular, hexagonal, trapezoidal.

11. The ultrasonic transducer according to any one of claims 5 to 10, wherein, Each column is substantially cylindrical in shape.

12. The ultrasonic transducer according to any one of the preceding claims, wherein, The material is a metal or an alloy or includes a metal or an alloy.

13. The ultrasonic transducer according to any one of the preceding claims, wherein, The material is platinum or includes platinum.

14. The ultrasonic transducer according to any one of the preceding claims, wherein, The ultrasonic transducer is a millimeter ultrasonic transducer or a micromachined ultrasonic transducer.

15. The ultrasonic transducer according to claim 14, wherein, The ultrasonic transducer is a micromachined ultrasonic transducer selected from the group consisting of a capacitive micromachined ultrasonic transducer (CMUT) and a piezoelectric micromachined ultrasonic transducer (PMUT).

16. The ultrasonic transducer according to any one of the preceding claims, wherein, The ultrasonic transducer does not include a substrate.

17. An ultrasonic transducer, comprising: a membrane configured to generate ultrasonic vibrations; a resonance enhancer configured to be disposed on the membrane; and optionally, a substrate configured to support the membrane, wherein the resonance enhancer is made of a material having an inherent frequency substantially equal to or close to the activation frequency of the membrane, and wherein the resonance enhancer includes six columns arranged in a hexagonal pattern to form a membrane vibration region within the six columns.

18. An ultrasonic transducer array, comprising a plurality of ultrasonic transducers according to any one of claims 1 to 17.

19. An ultrasonic transducer system, further comprising an array processing chip configured to be operatively connected to at least one ultrasonic transducer according to claims 1 to 17 or at least one ultrasonic transducer array according to claim 18 through through-silicon vias (TSVs) for performing parallel readout and processing.

20. A resonance enhancer for an ultrasonic transducer, the ultrasonic transducer including a membrane configured to generate ultrasonic vibrations, a resonance enhancer configured to be disposed on the membrane, and optionally a substrate configured to support the membrane, Among them, The resonance enhancer is made of a material having an inherent frequency substantially equal to or close to the activation frequency of the membrane.

21. The resonance enhancer according to claim 20, wherein, The resonance enhancer includes a plurality of pillars.

22. The resonance enhancer according to claim 21, wherein, The plurality of pillars are provided on the upper surface and / or the opposite lower surface of the ultrasonic transducer.

23. The resonance enhancer according to claim 22, wherein, The plurality of pillars are arranged around a center at the upper surface or the lower surface so as to form a membrane vibration region within the upper surface or the lower surface.

24. The resonance enhancer according to any one of claims 21 to 23, wherein, The plurality of pillars are spaced equidistantly from each other.

25. The resonance enhancer according to any one of claims 21 to 24, wherein, Six pillars are provided and the six pillars are arranged in a hexagonal pattern.

26. The resonance enhancer according to any one of claims 21 to 25, wherein, Each pillar has a transverse cross-section having a shape selected from irregular, rectangular, circular, oval, triangular, hexagonal, or trapezoidal.

27. The resonance enhancer according to any one of claims 21 to 26, wherein, Each pillar has a vertical cross-section having a shape selected from irregular, rectangular, circular, oval, triangular, hexagonal, trapezoidal.

28. The resonance enhancer according to any one of claims 21 to 27, wherein, Each pillar is substantially cylindrical in shape.

29. The resonance enhancer according to any one of claims 20 to 28, wherein, The material is a metal or an alloy or includes a metal or an alloy.

30. The resonance enhancer according to any one of claims 20 to 29, wherein the material is platinum or includes platinum.

31. A method of configuring a resonance enhancer according to any one of claims 20 to 30, the method comprising the steps of: (a) determining an operating frequency of the ultrasonic transducer based on one or more of the following parameters: selection of a material for the resonance enhancer, wherein the material has an inherent vibration frequency substantially equal to or close to the operating frequency; height of the pillars; and / or diameter of the pillars, (b) synchronizing the plurality of pillars at the operating frequency based on one or more of the following parameters so as to obtain an amplified mechanical displacement at a membrane vibration region defined by the plurality of pillars: geometric arrangement of the plurality of pillars; and / or distance between two adjacent pillars; and (c) optimizing a thickness of the membrane to adjust an elastic energy confinement at the membrane vibration region, such that a mechanical displacement of the resonance enhancer is maximized.

32. The method according to claim 31, wherein, One or more steps are performed by a numerical study based on finite element simulation (FEM).

33. A method of manufacturing an ultrasonic transducer according to any one of claims 1 to 17, the method comprising the steps of: providing a membrane configured to generate ultrasonic vibrations; providing a resonance enhancer configured to be disposed on the membrane; and optionally, providing a substrate configured to support the membrane, wherein the resonance enhancer is made of a material having an inherent frequency substantially equal to or close to the activation frequency of the membrane.

34. The method according to claim 33, wherein, Further comprising the steps of: providing an activation element configured to provide electrical power to generate vibrations on the membrane; and / or providing a reading element configured to read vibrations generated on the membrane.

Images