Ultrasound transducers, methods of manufacturing the same, and tissue treatment methods

Abstract

Ultrasound transducer assemblies comprising a ultrasound producing material, a plurality of actuation regions on a surface of the ultrasound producing material, and at least one non-actuation region on the surface of the ultrasound producing material separating the first actuation region from the second actuation region. Each actuation region is operable to produce a propagating acoustic wave. Also provided are ultrasound treatment systems comprising a transducer assembly and an applicator for applying ultrasound energy to a patient using the transducer assembly. Skin treatment methods are provided, comprising placing an applicator in contact with or adjacent to a first region of interest on the skin of a subject, and applying ultrasound energy to the first region of interest using the applicator, wherein the applicator comprises a plurality of actuation regions and at least one non-actuation region on a surface of a ultrasound producing material.

Description

ULTRASOUND TRANSDUCERS, METHODS OF MANUFACTURING THE SAME, AND TISSUE TREATMENT METHODSRELATED APPLICATION DATA

[0001] This application claims priority pursuant to 35 U.S.C. §119(e) to U.S. Provisional Patent Application Ser. No. 63 / 571,792, filed on March 29, 2024, which is incorporated herein by reference in its entirety.FIELD

[0002] The technology described herein generally relates to the treatment of biological tissue (e g., skin, muscle, fat, nerves, and / or glands), and more specifically to treatment of tissue using ultrasound.BACKGROUND

[0003] Current ultrasound therapy approaches for the treatment of biological tissue include radiofrequency microneedling (RFMN) and high intensity focused ultrasound (HIFU). In RFMN, ultra-fine needles are used to penetrate the skin, and the needles release radiofrequency energy which heats the skin and stimulates a healing response within the body. In HIFU, ultrasonic energy is employed to target the skin and create coagulation zones therein.

[0004] However, current systems and methods for ultrasound therapy can suffer from one or more disadvantages, including for clinical applications. For example, RFMN requires puncturing the tissue of a patient. HIFU is time-consuming and has a high cost. Accordingly, there exists a therapeutic need for improved systems and methods of treatment using ultrasound therapy that can provide improved efficacy, improvement in clinical results, faster treatment, improved ease-of-use, improved ability to treat large tissue areas, and / or reduction in risk of adverse events.SUMMARY

[0005] This summary is provided to introduce a selection of concepts in a simplified form that are further described below in the detailed description. This summary is not intended toidentify key features or essential features of the claimed subject matter, nor is it intended to be used in isolation as an aid in determining the scope of the claimed subject matter.

[0006] Embodiments of the technology described herein are directed towards treatment of biological tissue, for instance that of a patient in need thereof, which can achieve improved efficacy and / or clinical results, improved speed of treatment, improved ease-of-treatment, improved ability to treat large areas of tissue, and / or reduced risk of adverse results. The disclosed technology can be used to treat various types of biological tissue of a patient (such as a human or animal patient) in need thereof, including, for instance, skin tissue, muscle tissue, fat tissue, nerve tissue, cartilage, other connective tissue, and / or glands, and / or components of skin, muscle, fat, nerves, glands, and / or other tissue on or within a patient.

[0007] A broad aspect of some embodiments herein relates to ultrasound transducer assemblies and methods of manufacturing the same. Additionally, ultrasound treatment systems are disclosed. Furthermore, in another aspect, methods of treating tissue and skin treatment methods using ultrasound are disclosed.

[0008] In one aspect, an ultrasound transducer assembly is provided, comprising an ultrasound producing material (such as a piezoelectric material or capacitive micromachined ultrasonic transducer (CMUT) structure or material), a plurality of actuation regions on a surface of the ultrasound producing material, wherein the plurality of actuation regions comprises at least a first actuation region and a second actuation region, and at least one non-actuation region on the surface of the ultrasound producing material separating the first actuation region from the second actuation region. In some embodiments, the first actuation region is operable to produce a first propagating acoustic wave in a direction perpendicular to a top surface of the first actuation region. In some embodiments, the second actuation region is operable to produce a second propagating acoustic wave in a direction perpendicular to a top surface of the second actuation region. Moreover, in some embodiments herein, a main beam or lobe of the first propagating acoustic wave and a main beam or lobe of the second propagating acoustic wave do not overlap each other by more than 30% at a distance Z away from the surface of the ultrasound producing material in the direction of the first propagating acoustic wave and / or in the direction of the second propagating acoustic wave, wherein the distance Z is a therapeutic distance of the ultrasound transducer assembly. The distance Z, in some embodiments, corresponds to a distance from the surface of the ultrasound producing material to a transition point of the ultrasoundtransducer assembly or of an individual actuation region of the assembly. In some embodiments, the plurality of actuation regions on the surface of the ultrasound producing material comprises n individual actuation regions, and the assembly comprises (1 to m) non-actuation regions on the surface of the ultrasound producing material separating the n individual actuation regions from one another, wherein n is an integer ranging from 2 to 65,536, and m is an integer ranging from 2 to 65,536. In some embodiments, the n individual actuation regions are operable to produce, respectively, n propagating acoustic waves in n directions perpendicular to n top surfaces of the n individual actuation regions, and n main beams or lobes of the n propagating acoustic waves, respectively, do not overlap each other by more than 30% at the distance Z away from the surface of the ultrasound producing material in the n directions of the n propagating acoustic waves.

[0009] In another aspect, an ultrasound treatment system is provided, comprising an ultrasound transducer assembly as described in this disclosure, and an applicator for applying ultrasound energy to a subject using the transducer assembly.

[0010] In yet another aspect, a method for treating skin of a subject is provided, the method comprising placing an applicator in contact with or adjacent to a first region of interest (ROI) on the skin, and applying ultrasound energy to the first ROI using the applicator. In some embodiments, the applicator comprises a plurality of actuation regions on a surface of an ultrasound producing (such as a piezoelectric material or CMUT structure or material), and the plurality of actuation regions comprises at least a first actuation region and a second actuation region. In some embodiments, the applicator comprises at least one non-actuation region on the surface of the ultrasound producing material separating the first actuation region from the second actuation region. In embodiments herein, the first actuation region is operable to produce a first propagating acoustic wave in a direction perpendicular to a top surface of the first actuation region, the second actuation region is operable to produce a second propagating acoustic wave in a direction perpendicular to a top surface of the second actuation region, and a main beam or lobe of the first propagating acoustic wave and a main beam or lobe of the second propagating acoustic wave do not overlap each other by more than 30% at a distance Z away from the surface of the ultrasound producing material in the direction of the first propagating acoustic wave and / or in the direction of the second propagating acoustic wave.

[0011] In another aspect, a method of making a transducer assembly is provided, the method comprising providing an ultrasound producing (such as a piezoelectric material or CMUT structure or material) having a first surface and a second surface, wherein the second surface is on an opposite side of the ultrasound producing material from the first surface. The method further comprises defining a metallization pattern on the first surface of the ultrasound producing material, and metallizing the first surface of the ultrasound producing material with a conductive material according to the metallization pattern. In some embodiments, metallizing the first surface of the ultrasound producing material or layer forms a first plurality of strips of the conductive material along a first direction in a lateral plane of the ultrasound producing material according to the metallization pattern, and a second plurality of strips of the conductive material along a second direction in the lateral plane.

[0012] The novel technologies described herein, in some embodiments, utilize the diffraction effects of ultrasound combined with the absorption characteristics of tissue to provide a unique transducer assembly and ultrasound treatment system that may be designed to accommodate any treatment area. Ultrasound transducer assemblies and treatment systems according to embodiments herein can produce pressure waves that do not interact or substantially interact with one another in close proximity to the transducer assembly, such that a natural focus of each actuation region can be achieved at a depth required for coagulation. Ultrasound transducer assemblies described herein, in some cases, can achieve thermal coagulation zones in a fraction of the time as compared to current technologies, with a much higher density, and without a need to puncture tissue.

[0013] Additional objects, advantages, and novel features of the disclosed technology will be set forth in part in the description which follows, and in part will become apparent to those skilled in the art upon examination of the following, or can be learned by practice of the disclosed technology.BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Aspects of the technology presented herein are described in detail below with reference to the accompanying drawing figures, which are not necessarily drawn to scale.

[0015] Figure 1 illustrates a schematic of an actuation surface.

[0016] Figure 2 illustrates a plot of output of a transducer.

[0017] Figure 3 A illustrates a three-dimensional radiation intensity plot from a square transducer.

[0018] Figure 3B illustrates a three-dimensional radiation intensity plot from a square transducer.

[0019] Figure 3C illustrates a three-dimensional radiation intensity plot from a square transducer.

[0020] Figure 4 illustrates a top view of an ultrasound transducer array.

[0021] Figure 5 illustrates a top view of an ultrasound transducer array in accordance with some embodiments described herein.

[0022] Figure 6A illustrates features of a method for manufacturing a transducer assembly in accordance with embodiments described herein.

[0023] Figure 6B illustrates features of a method for manufacturing a transducer assembly in accordance with embodiments described herein.

[0024] Figure 6C illustrates features of a method for manufacturing a transducer assembly in accordance with embodiments described herein.

[0025] Figure 7 illustrates a top view of actuator regions in accordance with some embodiments of a device described herein.

[0026] Figure 8 illustrates the simulated acoustic density in the x-y plane or elevation and azimuth, for the device of Figure 7.

[0027] Figure 9 illustrates a top view of actuator regions in accordance with some embodiments of a device described herein.

[0028] Figure 10 illustrates a side or sectional view of the simulated acoustic density in the y-z plane or elevation and depth, for the device of Figure 9, taken along lines 10—10.

[0029] Figure 11 illustrates a plot of simulated pressure of a transducer in accordance with some embodiments herein.

[0030] Figure 12 illustrates a plot of simulated intensity of a transducer according to some embodiments herein.

[0031] Figure 13 illustrates a plot of simulated on-axis pressure of a transducer in accordance with some embodiments herein.

[0032] Figure 14 illustrates a plot of simulated on-axis intensity of a transducer according to some embodiments herein.

[0033] Figure 15 illustrates a plot of simulated maximum temperature in the y-z plane in tissue treated with a transducer according to some embodiments herein.

[0034] Figure 16 illustrates a plot of simulated temperature in tissue at the spatial peak as a function of time, when treated with a transducer according to some embodiments herein.

[0035] Figure 17 illustrates a plot of simulated thermal dose for a transducer according to some embodiments herein.

[0036] Figure 18 illustrates a plot of simulated maximum temperature in the y-z plane in tissue treated with a transducer according to some embodiments herein.

[0037] Figure 19 illustrates a plot of simulated temperature in tissue at the spatial peak as a function of time, when treated with a transducer according to some embodiments herein.

[0038] Figure 20 illustrates a plot of simulated thermal dose for a transducer according to some embodiments herein.

[0039] Figure 21 illustrates a plot of simulated maximum temperature in the y-z plane in tissue treated with a transducer according to some embodiments herein.

[0040] Figure 22 illustrates a plot of simulated temperature in tissue at the spatial peak as a function of time, when treated with a transducer according to some embodiments herein.

[0041] Figure 23 illustrates a plot of simulated thermal dose for a transducer according to some embodiments herein.

[0042] Figure 24A illustrates electrode patterns in accordance with some embodiments of devices and methods herein.

[0043] Figure 24B illustrates electrode patterns in accordance with some embodiments of devices and methods herein.

[0044] Figure 25A illustrates electrode patterns in accordance with some embodiments herein.

[0045] Figure 25B illustrates electrode patterns in accordance with some embodiments herein.

[0046] Figure 26A illustrates an electrode switch in accordance with some embodiments herein.

[0047] Figure 26B illustrates an electrode switch in accordance with some embodiments herein.

[0048] Figure 27 illustrates a plot of lateral beamwidth for actuation regions according to some embodiments herein.

[0049] Figure 28 illustrates a plot of peak intensity depths for actuation regions according to some embodiments herein.

[0050] Figure 29A illustrates actuators in accordance with embodiments herein.

[0051] Figure 29B illustrates actuators in accordance with embodiments herein.

[0052] Figure 29C illustrates actuators in accordance with embodiments herein.

[0053] Figure 29D illustrates actuators in accordance with embodiments herein.

[0054] Figure 30A illustrates an electrode arrangements in accordance with an embodiment herein.

[0055] Figure 30B illustrates an electrode arrangements in accordance with an embodiment herein.

[0056] Figure 30C illustrates an electrode arrangements in accordance with an embodiment herein.

[0057] Figure 31 A illustrates a device design in accordance with embodiments herein.

[0058] Figure 3 IB illustrates a device design in accordance with embodiments herein.

[0059] Figure 31C illustrates a device design in accordance with embodiments herein.

[0060] Figure 3 ID illustrates a device design in accordance with embodiments herein.

[0061] Figure 3 IE illustrates a device design in accordance with embodiments herein.

[0062] Figure 32A illustrates a device design in accordance with embodiments herein.

[0063] Figure 32B illustrates a device design in accordance with embodiments herein.

[0064] Figure 32C illustrates a device design in accordance with embodiments herein.

[0065] Figure 32D illustrates a device design in accordance with embodiments herein.

[0066] Figure 32E illustrates a device design in accordance with embodiments herein.

[0067] Figure 33 illustrates an actuator design in accordance with some embodiments herein.

[0068] Figure 34A illustrates a device design in accordance with an embodiment described herein.

[0069] Figure 34B illustrates an exploded view of the device of Figure 34A.

[0070] Figure 34C illustrates an exploded view of device design in accordance with an embodiment described herein.DETAILED DESCRIPTION

[0071] The subject matter of aspects of the present disclosure is described with specificity herein to meet statutory requirements. However, the description itself is not intended to limit the scope of this patent. Rather, the inventors have contemplated that the claimed subject matter might also be embodied in other ways, to include different steps or combinations of steps similar to the ones described in this document, in conjunction with other present or future technologies. Moreover, although the term “step” can be used herein to connote different elements of methods employed, the terms should not be interpreted as implying any particular order among or between various steps disclosed herein unless and except when the order of individual steps is explicitly described.

[0072] Accordingly, embodiments described herein can be understood more readily by reference to the following detailed description, examples, and figures. Elements, features, apparatus, and methods described herein, however, are not limited to the specific embodiments presented in the detailed description, examples, and figures. It should be recognized that the exemplary embodiments herein are merely illustrative of the principles of the invention. Numerous modifications and adaptations will be readily apparent to those of skill in the art without departing from the spirit and scope of the invention.

[0073] In addition, all ranges disclosed herein are to be understood to encompass any and all subranges subsumed therein. For example, a stated range of “1.0 to 10.0” should be considered to include any and all subranges beginning with a minimum value of 1.0 or more and ending with a maximum value of 10.0 or less, e.g., 1.0 to 5.3, or 4.7 to 10.0, or 3.6 to 7.9. All ranges disclosed herein are also to be considered to include the end points of the range, unless expressly stated otherwise. For example, a range of “between 5 and 10” or “5 to 10” or “5-10” should generally be considered to include the end points 5 and 10, as well as any and all subranges falling within these values.

[0074] Further, when the phrase “up to” is used in connection with an amount or quantity; it is to be understood that the amount is at least a detectable amount or quantity. For example, a material or feature present in an amount “up to” a specified amount can be present from a detectable or non-zero amount and up to and including the specified amount.

[0075] Additionally, in any disclosed embodiment, the terms “substantially,” “approximately,” and “about” may be substituted with “within [a percentage] of’ what is specified, where the percentage includes 0.1, 1, 5, and 10 percent.

[0076] It is also to be understood that the article “a” or “an” refers to “at least one,” unless the context of a particular use requires otherwise.I. Ultrasound Transducer Assemblies

[0077] In one aspect, an ultrasound transducer assembly (interchangeably referred to in this disclosure as “ultrasound transducer assembly,” “ultrasound assembly,” and “transducer assembly”) is disclosed. Ultrasound transducer assemblies disclosed herein may be configured to generate and deliver ultrasound energy to a target area of a subject. For instance, the ultrasound transducer assembly may deliver ultrasound energy to skin tissue, including deep skin tissue layers.

[0078] In some embodiments, the ultrasound transducer assembly described herein comprises an ultrasound producing material, such as a piezoelectric material or CMUT structure or material. An ultrasound transducer assembly described herein can also comprise one or more actuation region(s) on a surface of the ultrasound producing material, and one or more nonactuation region(s) on a surface of the ultrasound producing material. As described further herein, an “ultrasound producing” (or “ultrasound generating”) material or structure can refer to any substance or structure that is configured to or capable of generating or producing ultrasound, such as occurs in the case of a piezoelectric material through the piezoelectric effect or through what is sometimes described as the “inverse” piezoelectric effect. This effect can be described as vibration of the piezoelectric material in response to an electric signal (e.g., an alternating current or AC electric signal). The piezoelectric material can alternatingly expand and contract, thereby emitting sound (ultrasound) waves. However, other materials or structures in addition to or instead of a piezoelectric material may be used in an ultrasound transducer assembly described herein. For example, in some cases, a CMUT structure or material is used. Such a structure or material is further described hereinbelow. It is to be understood that the ultrasound producing material of a transducer assembly is not particularly limited. In some preferred embodiments, the ultrasound producing material or structure of an assembly described herein generates ultrasound using an electrical stimulus.

[0079] Additionally, in some embodiments, the ultrasound producing material of a device or assembly described herein (e.g., a piezoelectric material) may have a first surface and a second surface. The second surface is in facing opposition or opposite to the first surface. In some cases, the opposite or opposing surfaces can be “top” and “bottom” surfaces, such as top and bottom surfaces of an ultrasound producing layer (e.g., a layer formed by a piezoelectric material “sheet” or by a CMUT structure).

[0080] Turning again to materials and structures of an ultrasound producing material of a device or assembly described herein, any material or structure not inconsistent with the technical objectives of the present disclosure may be used. In some preferred embodiments, an ultrasound producing material comprises a piezoelectric material. Such a piezoelectric material may be any piezoelectric material not inconsistent with the technical objectives of this disclosure. For instance, in some embodiments, the piezoelectric material may be a naturally occurring piezoelectric material, such as quartz (SiCh), tourmaline group minerals, or Rochelle salt. In some cases, a piezoelectric material comprises or is formed from a synthetic organic or polymeric material, such as poly vinylidene fluoride (PVDF). In some implementations, a piezoelectric material comprises or is formed from an inorganic material, such as a piezoceramic material. Non-limiting examples of inorganic piezoelectric materials include lead zirconate titanate (PZT), lead magnesium niobate (PMN), lead magnesium niobate-lead titanate (PMN-PT), barium titanate (BaTiO.i), zinc oxide (ZnO), aluminum nitride (AIN), gallium phosphate (GaPO4), and potassium sodium niobate.

[0081] Moreover, in some embodiments, a piezoelectric material described herein comprise, is, or is formed from a single crystal, a polycrystalline material, or a composite material. Further, in some embodiments, the piezoelectric material may be porous.

[0082] An ultrasound producing material of a transducer assembly described herein may also, in some embodiments, comprise a micromachined structure such as a capacitive micromachined ultrasonic transducer structures (CMUT), a piezoelectric micromachined ultrasound transducer (PMUT) structure, a polymer micromachined ultrasound transducer (polymer MUT) structure, and / or a membrane-based mechanically vibrating structure. As understood by one of ordinary skill in the art, a CMUT does not exhibit piezoelectric behavior. Instead, a CMUT can comprise a parallel-plate capacitor with a fixed electrode at the bottom and a clamped metalized membrane suspended above a cavity. Ultrasound waves are generated whenan AC signal (e g., superimposed on a DC voltage), is applied between both electrodes, causing the membrane to vibrate. Thus, CMUTs use electrostatic forces to generate (and / or detect) ultrasound waves. In some cases, CMUTs can offer one or more advantages over piezoelectric transducers, such as wider bandwidth, better integration with electronics, and ease of fabricating large arrays.

[0083] In some embodiments, the ultrasound producing material of a transducer assembly described herein defines or is disposed on or formed by a single plate. For example, such a plate may be a crystalline piezoelectric plate, polycrystalline piezoelectric plate, or composite piezoelectric plate. The plate, in some embodiments, comprises or is formed from a CMUT, PMUT, polymer MUT, or membrane-based mechanically vibrating structure.

[0084] Additionally, an ultrasound producing plate may have any shape not inconsistent with the technical objectives of this disclosure. For instance, an ultrasound producing material may define or be disposed on or formed by a plano-convex structure, a plano-concave structure, a convex-concave structure, or a cylinder.

[0085] Further, an ultrasound producing plate may have any thickness and / or width not inconsistent with the objectives of the present disclosure. For instance, in some embodiments, a thickness of a plate may be selected so as to define a target or desired resonance frequency. In some embodiments, a width of an ultrasound producing plate may be selected so as to define a target or desired opening angle for an ultrasonic beam (“beam angle”). It is to be understood that ultrasound transducer assemblies described herein are not limited to having only one ultrasound producing material or one ultrasound producing plate, and may comprise a plurality of ultrasound producing materials and / or a plurality of ultrasound producing plates.

[0086] In embodiments herein, an ultrasound assembly described herein comprises one or more actuation region(s) on a surface of the ultrasound producing material. It is to be understood that an actuation region is a region that can be selectively “actuated,” “activated,” or “turned on.” In some embodiments, selectively actuating, activating or turning on an actuation region results in formation of an individual transducer element or transducer region. In some embodiments, actuation may refer to the use of energy, such as electrical energy, to mechanically vibrate a region or area.

[0087] In some embodiments, only one surface (e.g., the top or the bottom) of the ultrasound producing material is patterned. In other embodiments, both the top and bottom of the ultrasoundproducing material are patterned. In some embodiments, an actuation region is a region formed by the overlap of a top patterned region and a bottom patterned region.

[0088] In some embodiments, a plurality of actuation regions is present on a surface of the ultrasound producing material. In some embodiments, each of the actuation regions comprises or forms an individual, non-interfering transducer element or region. In some embodiments, each of the actuation regions is independently operable.

[0089] In one aspect, the ultrasound assembly comprises a first actuation region and a second actuation region on a surface of the ultrasound producing material. In some embodiments, the first actuation region is separated from the second actuation region by one or more non-actuation regions. That is, in some embodiments herein, the ultrasound assembly comprises a first actuation region, a second actuation region, and at least one non-actuation region on a surface of the ultrasound producing material, separating the first actuation region from the second actuation region. It is to be understood that a non-actuation region is a region that is not designed to be (or cannot be) “actuated,” “activated,” or “turned on” like an actuation region can be actuated, activated, or turned on.

[0090] In some embodiments, the actuation regions are formed of an electrically conductive material. Any electrically conductive material not inconsistent with the technical objectives of this disclosure may be employed. In some embodiments, the electrically conductive material comprises or is formed from one or more metals. For instance, in some embodiments, the electrically conductive material comprises gold, nickel, chrome, copper, or an alloy, combination, or mixture thereof. In some embodiments, the actuation regions comprise or are formed from an electrically conductive film or tape.

[0091] The actuation region(s) may have any shape not inconsistent with the objectives of this disclosure. For instance, in some embodiments, the actuation region(s) are in the shape of a square. In other embodiments, the actuation regions may have shapes other than a square (such as, for example, rectangles, circles, etc.).

[0092] In some embodiments, the non-actuation regions are formed from an electrically insulating material. Any insulating material not inconsistent with the technical objectives herein may be employed. In some embodiments, the electrically insulating material comprises or is formed from the ultrasound producing material. Other insulating materials may also be used.

[0093] In some embodiments, the non-actuation regions consist of the ultrasound producing material. That is, in some embodiments, the actuation regions may be disposed directly on the ultrasound producing material, and the ultrasound producing material may act as the nonactuation region(s) that separate(s) the actuation regions from each other. In some such embodiments, an ultrasound transducer assembly described herein is a kerfless ultrasound transducer, such that it is not necessary to create mechanical separations or kerfs in the ultrasound transducer assembly and / or add kerf filling materials to the assembly. In some embodiments, the non-actuation regions are determined by additional passive material placed above (i.e., on top) or below (i.e., behind) the ultrasound producing material. Moreover, the passive materials, in some cases, can be used to block or transmit acoustic waves. Such an embodiment is illustrated in Figure 34 below, for instance.

[0094] It is to be understood that actuation and / or non-actuation regions may also be created passively (i.e., outside the ultrasound producing material without electrodes). For instance, in some embodiments, front and / or back layers of an ultrasound producing material (e.g., a piezoelectric material), comprising actuation and / or non-actuation regions, may be independently created. These layers are then attached to an ultrasound producing plate (e.g., a piezoelectric plate) or ultrasound producing material (e.g., a piezoelectric material). For instance, in some embodiments, the ultrasound producing plate has continuous top and bottom electrodes. In some embodiments, a matching layer is attached to a front layer of the ultrasound producing plate. The matching layer comprises “open” regions, which allow acoustic energy to pass through, and “closed” regions, which block acoustic energy from passing through. Similarly, in some embodiments, a backing layer is attached to a back layer of the ultrasound producing plate. The backing layer comprises “absorbing” regions, which “absorb” acoustic energy, and “nonabsorbing” regions, which do not “absorb” acoustic energy. In some embodiments, an ultrasound producing plate may comprise backing layers and matching layers.

[0095] In some cases, the distance between the first actuation region and the second actuation region is selected to achieve one or more therapeutic objectives herein. In conventional ultrasound imaging and most therapy devices, the separation distance between actuation regions is kept at a minimum to enable superior electronic focusing and steering (see square regions 40 in Figure 4, which are actuation regions separated by “kerfs” or “streets” 42). In “transmit” mode, actuation regions which are independently controlled work together to enable theconstructive interference of the ultrasound waves at specific spatial locations by placing the appropriate time delays on each region. In “receive” mode, the actuation regions receive sound waves from the field and use appropriate time delays to listen or focus on specific spatial locations by adding all the received signals together. In contrast, in embodiments herein, the actuation regions can work independently of one another to create a therapeutic effect. This is achieved by creating a sufficient separation distance between actuation regions (see, e.g., Figure 5, which shows individual actuation regions 50 separated by kerfs / streets 52), and / or choosing appropriate operational parameters (such as, for example, frequency) such that ultrasound energy propagating away from the actuation regions does not constructively interfere to create unwanted therapeutic effects. For clarity, Figure 4 and Figure 5 each illustrate a top view of a two- dimensional ultrasound transducer array, with “rows” of the arrays labeled with numerals 1-8 and “columns” labeled with letters A-H for convenience. In some embodiments herein, actuation regions have sizes larger than a wavelength of a propagating acoustic wave produced by the actuation regions (e.g., at an operating frequency of 10 MHz), whereas conventional devices used for diagnostic imaging and therapy have sizes of less than a wavelength of a propagating acoustic wave produced by the actuation regions (e.g., at an operating frequency of 10 MHz).

[0096] In some embodiments, a first non-actuation region separates the first actuation region from the second actuation region by a distance greater than 25 microns, greater than 50 microns, greater than 75 microns, greater than 100 microns, greater than 150 microns, greater than 200 microns, greater than 250 microns, greater than 300 microns, greater than 350 microns, greater than 400 microns, or greater than 450 microns. In some embodiments, a first non-actuation region separates the first actuation region from the second actuation region by a distance of at least 0.5 millimeters, at least 0.55 mm, at least 0.6 mm, at least 0.7 mm, at least 0.8 mm, at least 0.9 mm, or at least 1 mm. In some embodiments, a first non-actuation region separates the first actuation region from the second actuation region by a distance of up to 5 mm, up to 10 mm, or up to 15 mm.

[0097] In some embodiments, the first actuation region is operable to produce a first propagating acoustic wave in a direction perpendicular to a top surface of the first actuation region. Additionally, in some embodiments, the second actuation region is operable to produce asecond propagating acoustic wave in a direction perpendicular to a top surface of the second actuation region.

[0098] As noted above, the distance between the first actuation region and the second actuation region is selected to achieve one or more therapeutic objectives. In some embodiments, the distance between the first actuation region and the second actuation region is selected such that a main beam or lobe of the first propagating acoustic wave and a main beam or lobe of the second propagating acoustic wave do not overlap each other by more than 75%, more than 60%, more than 50%, more than 45%, more than 40%, more than 35%, more than 30%, more than 25%, more than 20%, more than 15%, more than 10%, or more than 5% at a distance “Z” away from the surface of the ultrasound producing material in the direction of the first propagating acoustic wave and / or in the direction of the second propagating acoustic wave.

[0099] The distance Z, in some embodiments, can be associated with a therapeutic distance of the ultrasound transducer assembly. For example, in some instances, the distance Z, corresponds to a distance from a surface of the ultrasound producing material to a transition point of the ultrasound transducer assembly or of an individual actuation region of the assembly. Moreover, it is to be understood that such a transition point of an ultrasound assembly or actuation region can be the point at which a relevant propagating acoustic wave makes a transition from a near-field regime (or Fresnel region) to a far-field regime (or Fraunhofer region). Such transition points and distances are described, for example, in Douglas A. Christensen, Ultrasonic Bioinstrumentation, John Wiley & Sons, 1988 (hereinafter, “Christensen”).

[0100] Figure 1 shows an actuation surface in the shape of a circular disc with radius a, diameter D, and pressure p as described by Christensen. The distance to an observation point (10) from the actuation surface is described as r’. This axis is normal to the actuator surface and goes through the disc center. Figure 2 shows the solution of the on-axis pressure from the circular disc shown in Figure 1 as diagrammed by Christensen. The two main pressure regions, i.e., the near field and the far field, have been identified, where the transition distance between the two regions is related to the disc diameter squared and the sound wavelength. This distance is sometimes called the diffractional focus or natural focus of an aperture (actuator) and is identified in Figure 2 as dashed line 22. The transducer face is denoted in Figure 20 as element 20. Each of Figures 3 A, 3B, and 3C shows three-dimensional intensity plots at three differentdepths, as provided by Christensen, which demonstrate the reduction in complexity of the sound field the farther the distance from the actuator. In Figure 3A, z = 20 cm. In Figure 3B, z = 50 cm. In Figure 3C, z = 100 cm. In all of Figures 3A-3C, the actuator surface is 5 cm by 5 cm and operates at 3 MHz. Embodiments described herein leverage this performance attribute of the actuator on a smaller scale.

[0101] In some embodiments of assemblies described herein, the distance Z is defined according to Equation 1 :Z = D2 / 4X (Equation 1), where D is the diameter (or equivalent cross-sectional dimension) of a top surface of a single actuation region (or an average diameter or equivalent cross-sectional dimension of top surfaces of a plurality of actuation regions), and where is the wavelength of a propagating acoustic wave in water, such as the propagating wave produced by a single actuation region.

[0102] With reference to Equation 1 above, it is to be understood that the diameter or equivalent cross-sectional dimension is in the plane of the relevant actuation region (as indicated, for instance, by Christensen). In addition, as described herein and as indicated by Equation 1, the therapeutic distance Z (which may also be called a therapeutic depth) can be varied as desired by selecting or changing the size (that is, the diameter or equivalent cross-sectional dimension) of the relevant actuation region and / or by selecting or changing the wavelength of the propagating acoustic wave produced by the relevant actuation region (that is, by selecting the frequency of operation of the actuation region).

[0103] It is further to be understood that, in some implementations, a majority of the actuation regions of an assembly described herein have the same Z value as one another, or similar Z values to one another (e.g., within 10% of one another), when Z is defined according to Equation 1 above. In some instances, all or substantially all of the actuation regions of an assembly (e.g., at least 90% or at least 95% of the actuation regions of the assembly) have the same Z value as one another, or a Z value within 10% of an average Z value of the assembly. Thus, in some cases, an assembly described herein can be considered to have an “overall” or “average” Z value (that is, a desired or pre-selected therapeutic distance), and that “overall” or “average” Z value (or therapeutic distance) can be the same as or similar to the Z value of a given actuation region or group of actuation regions, calculated according to Equation 1.

[0104] Any Z value or therapeutic distance not inconsistent with the technical objectives of the present disclosure can be used. For example, in some cases, an assembly described herein has a Z value or therapeutic distance of at least 1 mm, at least 2 mm, at least 3 mm, at least 5 mm, or at least 10 mm. In some instances, an assembly described herein has a Z value or therapeutic distance of 1-50 mm, 1-40 mm, 1-30 mm, 1-20 mm, 1-10 mm, 2-50 mm, 2-40 mm, 2-30 mm, 2-20 mm, 2-10 mm, 3-50 mm, 3-40 mm, 3-30 mm, 3-20 mm, 3-10 mm, 5-50 mm, 5- 40 mm, 5-30 mm, 5-20 mm, 5-10 mm, 10-50 mm, 10-40 mm, 10-30 mm, or 10-20 mm. In some embodiments, a Z value or therapeutic distance or depth in a range indicated above can place a therapeutic zone within, or provide clinically effective therapy to, the dermis of a subject, or to the junction of the dermis and the subcutaneous layer (or hypodermis) of a subject, or within fat or muscle of a subject. In some embodiments, when pressures are combined, a peak thereof is approximately +2.5 dB above the trough.

[0105] It is to be understood that ultrasound transducer assemblies described herein are not necessarily limited to having only two individual actuation regions separated by one or more non-actuation regions. Instead, in some instances, more than two individual actuation regions are present. For instance, in some embodiments, the plurality of actuation regions comprises at least a third actuation region. When the plurality of actuation regions includes a third actuation region, the ultrasound assembly comprises at least one non-actuation region on the surface of the ultrasound producing material that separates the third actuation region from the first actuation region and / or from the second actuation region. In one aspect, the third actuation region is operable to produce a third propagating acoustic wave in a direction perpendicular to a top surface of the third actuation region. In some embodiments, a main beam or lobe of the third propagating acoustic wave does not overlap with the main beam or lobe of the first propagating acoustic wave by more than 75%, more than 60%, more than 50%, more than 45%, more than 40%, more than 35%, more than 30%, more than 25%, more than 20%, more than 15%, more than 10%, or more than 5% at a distance Z away from the surface of the ultrasound producing material in the direction of the first propagating acoustic wave and / or in the direction of the third propagating acoustic wave, and / or does not overlap with the main beam or lobe of the second propagating acoustic wave by more than 75%, more than 60%, more than 50%, more than 45%, more than 40%, more than 35%, more than 30%, more than 25%, more than 20%, more than 15%, more than 10%, or more than 5% at a distance Z away from the surface of the ultrasoundproducing material in the direction of the second propagating acoustic wave and / or in the direction of the third propagating acoustic wave.

[0106] Moreover, ultrasound transducer assemblies described herein are not necessarily limited to three individual actuation regions separated from one another by one or more nonactuation regions. Instead, the basic structure and operating principles described above can be extended to provide an ultrasound transducer assembly comprising virtually any number of individual actuation regions. Moreover, the individual actuation regions can be separated by any number of non-actuation regions.

[0107] Thus, in some embodiments, an ultrasound transducer assembly described herein may comprise a plurality of actuation regions on a surface of the ultrasound producing material, wherein the plurality of actuation regions comprises n individual actuation regions, where n is an integer between 2 and 65,536 (i.e., n is an integer between 21and 216). Additionally, it is to be understood that ultrasound transducer assemblies are not limited to having only one nonactuation region, and may comprise a plurality of non-actuation regions m separating the n individual actuation regions from each other, wherein m is an integer from 2 to 65,536 (i.e., m is an integer between 21and 216). For clarity and convenience, when an actuation region or a plurality of actuation regions is described in the present disclosure, it is to be understood that the actuation region can be a first, second, or nth actuation region, unless the context requires otherwise. Similarly, when a non-actuation region or plurality of non-actuation regions is described in the present disclosure, it is to be understood that the non-actuation region can be a first, second, or / nth non-actuation region, unless the context requires otherwise.

[0108] Furthermore, when the ultrasound assembly described herein comprises n individual actuation regions, the n individual actuation regions are operable to produce, respectively, n propagating acoustic waves in n directions perpendicular to n top surfaces of the n individual actuation regions. Additionally, n main beams or lobes of the n propagating acoustic waves, respectively, do not overlap each other by more than 75%, more than 60%, more than 50%, more than 45%, more than 40%, more than 35%, more than 30%, more than 25%, more than 20%, more than 15%, more than 10%, or more than 5% at the distance Z away from the surface of the ultrasound producing material in the n directions of the n propagating acoustic waves. In this manner, an ultrasound transducer assembly described herein can provide virtually any number of individual actuation regions, and such individual actuation regions can be individually andindependently addressable, controlled, actuated, activated, turned on, and / or usable for providing ultrasound treatment.

[0109] In one aspect, the plurality of actuation regions forms or defines an array of actuation regions. In some embodiments, the array is a two-dimensional (2D) array. In some embodiments, the array is a side-by-side array, in which actuation regions are arranged side by side on the same plane. In some embodiments, the actuation regions are orthogonally opposed to each other or on opposite sides of the ultrasound producing material in a row-column pattern. Other configurations are also possible, such as linear arrays, curved arrays, annular arrays, or circular arrays. In some embodiments, the array is periodic. It should be understood that a periodic array is an array in which a distance between adjacent actuation regions is constant or similar throughout the entirety of the array. In other embodiments, the array is aperiodic, such that distances between adjacent actuation regions in the array are dissimilar and vary throughout the array. Aperiodic arrays allow for a plurality of differing depths of treatment to be achieved simultaneously and / or with the same device.

[0110] In some embodiments, each of the actuation regions in an array may be activated using different energy parameters, such as different frequencies, different intensities, different durations, and / or different powers. In some embodiments, the n actuation regions in an array may be activated to reach the same depth of treatment. In other embodiments, the n actuation regions in the array may be independently activated to reach different depths of treatment from each other, such that a plurality of target regions or volumes may be treated simultaneously and / or from the same assembly or device (such as, for example, with an aperiodic array).

[0111] In one aspect, ultrasound transducer assemblies described herein comprise a first set of electrodes extending in a first direction parallel to the surface of the ultrasound producing material. In some embodiments, ultrasound transducer assemblies described herein further comprise a second set of electrodes extending in a second direction parallel to the surface of the ultrasound producing material. The first direction and the second direction may each be selected to achieve one or more therapeutic objectives herein.

[0112] For instance, in some embodiments, the first direction and the second direction are orthogonal or substantially orthogonal to one another. In some embodiments, the plurality of actuation regions is formed by the overlap of the first set of electrodes with the second set of electrodes.

[0113] In some embodiments, the first set of electrodes and the second set of electrodes are positioned on the same side of the ultrasound producing material. In another aspect, the first set of electrodes and the second set of electrodes are positioned on different sides of the ultrasound producing material. For example, in some embodiments, the first set of electrodes and the second set of electrodes are positioned on the bottom of the ultrasound producing material. In some embodiments, the first set of electrodes and the second set of electrodes are positioned on the top of the ultrasound producing material. In yet other embodiments, a first set of electrodes is position on the top of the ultrasound producing material, and a second set of electrodes is positioned on the bottom of the ultrasound producing material. In some embodiments, the first set of electrodes and the second set of electrodes are connected to an electrical-mechanical switch or multiplexer.

[0114] The first set of electrodes and / or the second set of electrodes may be formed of an electrically conductive material. In some embodiments, the electrically conductive material comprises one or more metals. For instance, in some embodiments, the electrically conductive material comprises or is formed from gold, nickel, chrome, copper, or an alloy, combination, or mixture thereof. In some embodiments, the first set of electrodes and / or the second set of electrodes comprises or is formed from an electrically conductive film or tape.

[0115] Figure 6A, Figure 6B, and Figure 6C illustrate some exemplary transducer assembly designs. As shown in this figure, the transducer design does not need to be ‘square’ when using a row-column pattern of electrodes. Moreover, the number of column electrodes does not have to equal the number of row electrodes. In the exemplary embodiment of Figures 6A-B, 60 actuation regions are provided (denoted as 66 in Figure 6C), with six row electrodes and 10 column electrodes. Figure 6A shows the top of an ultrasound producing plate (60), including an HV bus (61) and “row” like electrodes (62) and an isolation cut (67). Figure 6B shows the bottom of the ultrasound producing plate (60), including a GND bus (61) and “column” like electrodes (64) and an isolation cut (68). The overlap of the row and column electrodes (62, 64) provide the individual actuation regions (66).

[0116] In some embodiments, an ultrasound transducer assembly described herein includes electrical wiring. In one aspect, the ultrasound assembly further comprises a controller configured to receive an indication regarding interference of propagating acoustic waves from the transducer assembly.

[0117] Ultrasound transducer assemblies described herein, in some cases, can also comprise or be characterized by certain additional components or features (or a combination of additional components and features) that can provide one or more advantages compared to other transducer assemblies.II. Ultrasound Treatment Systems

[0118] Ultrasound treatment systems are also provided herein.

[0119] In some embodiments, an ultrasound treatment system described herein comprises an ultrasound transducer assembly such as described in Section I above. For example, in some cases, the ultrasound transducer assembly comprises an ultrasound producing material or layer (e.g., a piezoelectric material), one or more actuation region(s) on a surface of the ultrasound producing material, and one or more non-actuation region(s) on a surface of the ultrasound producing material. Any ultrasound transducer assembly described hereinabove in Section I may be used in a system described herein.

[0120] Moreover, any ultrasound producing material(s), actuation region material(s), and non-actuation region material(s) described elsewhere in this disclosure (for example, in Section I above) may be employed as the ultrasound producing material(s), actuation region material(s), and non-actuation region material(s), respectively, in the ultrasound treatment systems described herein. Additionally, the ultrasound transducer assembly, ultrasound producing material(s), actuation region(s), and non-actuation region(s) may have any of the characteristics and / or features respectively described hereinabove in Section I for these components.

[0121] In some embodiments, an ultrasound treatment system described herein further includes an applicator for applying ultrasound energy to a subject using the transducer assembly. In some instances, the applicator comprises a distal face configured to contact a skin surface of the subject. The ultrasound transducer assembly is positioned on the distal face of the applicator so as to contact the skin surface of the subject.

[0122] Further, in some embodiments, an ultrasound treatment system described herein does not include a motor or equivalent device for movement. In other embodiments, an ultrasound treatment described system herein includes a motor to move the device over the skin of a subject. In some embodiments, an ultrasound system herein may also include a tracking component to track movement of the device over the skin of a subject.

[0123] It should be understood that each actuation region on the surface of the ultrasound producing material of the ultrasound treatment systems herein (as well as each actuation region of the ultrasound transducer assemblies described in Section I hereinabove) can be individually and independently addressable, controlled, actuated, activated, turned on, and / or usable for providing ultrasound treatment. In some embodiments, each of the actuation regions may be activated to reach the same depth of treatment. In other embodiments, one or more (e.g., all) actuation regions may be independently activated to reach a different depth of treatment as compared to the other actuation regions in the assembly and / or in the system, such that a plurality of target regions of a subject may be treated simultaneously and / or from the same assembly and / or from the same system. For instance, in some embodiments, each of the actuation regions may be activated using different energy parameters, such as different frequencies, different intensities, different durations, and / or different powers.

[0124] Without being bound by theory, it is believed that an novel ultrasound treatment system described herein and an ultrasound transducer assembly described above provide sufficient distance between the actuation regions therein such that pressure waves do not interact in close proximity to the ultrasound transducer assembly and, as a result, the natural focus of each actuation region is achieved at a depth required for coagulation. In some cases, a system, assembly, or method described herein prevents thermal coagulation within tissue that is ‘before’ or closer to the transducer assembly than the distance Z (the therapeutic distance), such as epidermis tissue. However, a system, assembly, or method described herein, in some cases, can still allow coagulation zones (caused by each transducer assembly in the ultrasound treatment system) to be formed within the target tissue that is at or ‘deeper’ than the distance Z (e.g., dermis tissue), in a direction directly in front of the respective transducer assembly. That is, a novel system described herein, in some instances, can eliminate or reduce undesired or “shallow” tissue damage (e.g., epidermal damage), while still achieving desired coagulation within the target or “deep” tissue (e.g., dermis). It is to be understood that such “shallow” and “deep” regions or tissue are relative to one another (i.e., relatively shallow or relatively deep) or, preferably, at distance less than Z (“shallow”) or at a distance of Z or greater than Z (“deep’). Moreover, in some embodiments of novel systems herein, variations in frequency (for instance, utilizing a high frequency) can minimize diffraction and interactions between actuation regions, eliminating downstream effects in tissue due to ultrasound absorption.

[0125] Ultrasound treatment systems described herein, in some cases, can also comprise or be characterized by certain additional components or features (or a combination of additional components and features) that can provide one or more advantages compared to other ultrasound treatment systems.III. Skin Treatment Methods

[0126] A method for treating skin (interchangeably referred to as “method for treating skin” and “skin treatment method” in this disclosure) of a subject is also provided herein.

[0127] In one aspect, a skin treatment method herein comprises placing an applicator in contact with or adjacent to a first region of interest (ROI) on the skin of a subject, and applying ultrasound energy to the first ROI using the applicator.

[0128] In some embodiments, the applicator comprises an ultrasound transducer assembly. Any ultrasound transducer assembly described in Section I hereinabove or elsewhere in this disclosure may be employed as the ultrasound transducer assembly of the applicator used in the methods herein.

[0129] In one aspect, the transducer assembly of the applicator used in methods herein comprises one or more actuation region(s) on a surface of an ultrasound producing material, and one or more non-actuation region(s) on a surface of the ultrasound producing material.

[0130] The ultrasound producing material may be any ultrasound producing material described hereinabove in Sections I and / or II, such as, for example, a single crystal, a polycrystalline material, a composite material, a piezoelectric ceramic material, and / or any material exhibiting piezoelectric behavior. The ultrasound producing material may have any composition, properties, features, characteristics, shape, and / or dimensions as discussed in Section I or elsewhere in this disclosure.

[0131] In some embodiments herein, a plurality of actuation regions is present on a surface of the ultrasound producing material. In one aspect, the plurality of actuation regions comprises a first actuation region and a second actuation region on a surface of the ultrasound producing material. In some embodiments, the first actuation region is separated from the second actuation region by one or more non-actuation regions. That is, in some embodiments herein, the applicator comprises a first actuation region, a second actuation region, and at least one non- actuation region on a surface of the ultrasound producing material, separating the first actuationregion from the second actuation region. The actuation region(s) and the non-actuation region(s) may have any composition, properties, features, characteristics, shape, and / or dimensions as discussed in Section I above or elsewhere in this disclosure. For instance, in some embodiments, each of the actuation regions comprises or forms an individual, non-interfering transducer element or region. In some embodiments, each of the actuation regions is independently operable. That is, each of the actuation regions is individually and independently addressable, controlled, actuated, activated, turned on, and / or usable for providing ultrasound treatment.

[0132] In some embodiments, the actuation regions are formed from an electrically conductive material. In some embodiments, the non-actuation regions are formed from an electrically insulating material. Any electrically conductive material and / or electrically insulating material discussed hereinabove in Section I or elsewhere in this disclosure may be employed.

[0133] In some embodiments, the first actuation region is operable to produce a first propagating acoustic wave in a direction perpendicular to a top surface of the first actuation region. In some embodiments, the second actuation region is operable to produce a second propagating acoustic wave in a direction perpendicular to a top surface of the second actuation region.

[0134] The distance between the first actuation region and the second actuation region, in some cases, can be selected to achieve one or more therapeutic objectives herein. For instance, in some embodiments, the distance between the first actuation region and the second actuation region is selected such that a main beam or lobe of the first propagating acoustic wave and a main beam or lobe of the second propagating acoustic wave do not overlap each other by more than 75%, more than 60%, more than 50%, more than 45%, more than 40%, more than 35%, more than 30%, more than 25%, more than 20%, more than 15%, more than 10%, or more than 5% at a distance Z away from the surface of the ultrasound producing material in the direction of the first propagating acoustic wave and / or in the direction of the second propagating acoustic wave. The distance Z is the therapeutic distance of the ultrasound transducer assembly, as described in detail hereinabove in Section I. As was discussed in Section I, in some embodiments, the distance Z is defined according to Equation 1 (Z = D2 / 4X, where D is the diameter (or equivalent cross-sectional dimension) of a top surface of a single actuation region (or an average diameter or equivalent cross-sectional dimension of top surfaces of a plurality of actuation regions), and X is the wavelength of a propagating acoustic wave in water, such as thepropagating wave produced by a single actuation region). Any Z value or therapeutic distance not inconsistent with the technical objectives of the present disclosure can be used. For example, in some cases, the therapeutic distance Z is at least 1 mm, at least 2 mm, at least 3 mm, at least 5 mm, or at least 10 mm. In some instances, the therapeutic distance Z is 1-50 mm, 1-40 mm, 1-30 mm, 1-20 mm, 1-10 mm, 2-50 mm, 2-40 mm, 2-30 mm, 2-20 mm, 2-10 mm, 3-50 mm, 3-40 mm, 3-30 mm, 3-20 mm, 3-10 mm, 5-50 mm, 5-40 mm, 5-30 mm, 5-20 mm, 5-10 mm, 10-50 mm, 10-40 mm, 10-30 mm, or 10-20 mm.

[0135] It is to be understood that applicators and / or ultrasound transducer assemblies described herein are not necessarily limited to having only two individual actuation regions separated by one or more non-actuation regions. Instead, the basic structure and operating principles described above can be extended to provide an applicator comprising virtually any number of individual actuation regions. Moreover, the individual actuation regions can be separated by any number of non-actuation regions. For example, in some embodiments, an applicator as described herein may comprise a plurality of actuation regions on a surface of the ultrasound producing material, wherein the plurality of actuation regions comprises n individual actuation regions, where n is an integer between 2 and 65,536. Additionally, it is to be understood that applicators and / or ultrasound transducer assemblies are not limited to having only one non-actuation region, and may comprise a plurality of non-actuation regions m separating the n individual actuation regions from each other, wherein m is an integer from 2 to 65,536. Furthermore, when the applicator described herein comprises n individual actuation regions, the n individual actuation regions are operable to produce, respectively, n propagating acoustic waves in n directions perpendicular to n top surfaces of the n individual actuation regions. Additionally, n main beams or lobes of the n propagating acoustic waves, respectively, do not overlap each other by more than 75%, more than 60%, more than 50%, more than 45%, more than 40%, more than 35%, more than 30%, more than 25%, more than 20%, more than 15%, more than 10%, or more than 5% at the distance Z away from the surface of the ultrasound producing material in the n directions of the n propagating acoustic waves. In this manner and as described further herein, applicators used in the methods described herein can provide virtually any number of individual actuation regions. Such individual actuation regions can be individually and independently addressable, controlled, actuated, activated, turned on, and / or usable for providing ultrasound treatment.

[0136] In one aspect, a skin treatment method herein comprises placing the ultrasound treatment system disclosed in Section II above in contact with or adjacent to a first region of interest on the skin of a subject, and applying ultrasound energy to the first ROI using the ultrasound treatment system.

[0137] The ultrasound energy can have any properties and be provided in any manner not inconsistent with the technical objectives of the present disclosure. In some cases, for instance, the ultrasound energy has a frequency of at least 20 kHz, at least 50 kHz, at least 100 kHz, at least 500 kHz, or at least 1000 kHz. In some embodiments, the ultrasound energy has a frequency of up to 15 MHz, up to 20 MHz. or up to 25 MHz. For instance, in some embodiments, the ultrasound energy is in a range of 100 kHz to 25 MHz, 500 kHz to 25 MHz, 1000 kHz to 25 MHz, 100 kHz to 20 MHz, 500 kHz to 20 MHz, 1000 kHz to 20 MHz, 100 kHz to 15 MHz, 500 kHz to 15 MHz, or 1000 kHz to 15 MHz.

[0138] In one aspect of the methods herein, applying ultrasound energy to the first ROI causes thermal damage to a tissue layer beneath an epidermis of the skin (or other “shallow” tissue of skin, shallower than the distance Z). The thermal damage, in some embodiments, corresponds to the actuation regions on the applicator. In other words, in some embodiments, thermal damage comprising a plurality of thermally damaged zones corresponding to the plurality of actuation regions of the applicator is caused by the application of ultrasound energy to the first ROI. In some embodiments, the plurality of thermally damaged zones corresponds in a 1 : 1 manner to the plurality of actuation regions of the applicator.

[0139] Without intending to be bound by theory, it is believed that the novel methods herein, in some cases, provide sufficient distance between the actuation regions in the applicator employed, such that pressure waves do not interact with one another in close proximity to the applicator and, as a result, the natural focus of each actuation region is achieved at a depth required for coagulation. Methods, systems, and assemblies described herein, in some instances, prevent thermal coagulation on or within shallow tissue (such as the epidermis, in some cases), while still allowing coagulation zones (caused by each transducer assembly) to be formed within target or deep tissue (e.g., the dermis), in a direction directly in front of the respective transducer assembly. As a result, the novel methods described herein can eliminate or reduce epidermal or other shallow tissue damage, while still achieving desired coagulation within the target or deep tissue, such as the dermis.

[0140] It is to be understood that skin treatment methods as disclosed herein are not limited to treatment of only one ROI. Instead, the basic steps and principles described herein can be extended to treat virtually any number of regions of interest (i.e., n or “x” regions of interest). For instance, in some embodiments, a method as described herein comprises placing an applicator in contact with a first ROI on the skin of a subject, applying ultrasound energy to the first ROI using the applicator, placing the applicator in contact with n additional regions of interest, and applying ultrasound energy to each of the n additional regions of interest. The n additional regions of interest differ from one another and from the first region of interest, and n can be any integer not inconsistent with the technical objectives of the present disclosure, such as an integer from 2 to 1,000,000.

[0141] It is further to be understood that each region of interest can denote or correspond to a different treatment location, and, in some cases, the applicator can be moved from one location to another as the method of treatment is carried out. For instance, in some embodiments, a method herein further comprises an optional step of moving the applicator from contact with or from being adjacent to the first ROI to place the applicator in contact with or adjacent to a second ROI differing from the first ROI, and applying ultrasound energy to the second ROI using the applicator.

[0142] In some embodiments, applying ultrasound energy to the second ROI causes thermal damage to a tissue layer beneath a shallow or untargeted layer of tissue (e.g., an epidermis of the skin), differing from or in addition to any thermal damage caused by applying ultrasound energy to the first ROI. The thermal damage caused by applying ultrasound energy to the second ROI may comprise a plurality of thermally damaged zones corresponding to the plurality of actuation regions of the applicator. In some embodiments, the plurality of thermally damaged zones caused by applying ultrasound energy to the second ROI correspond in a 1 :1 manner to the plurality of actuation regions of the applicator. In one aspect, applying ultrasound energy to the first ROI does not cause thermal damage or coagulation to an undesired or untargeted tissue type (such as the epidermis of the skin, in some cases).

[0143] In some embodiments, the applicator is moved from contact with or from being adjacent to the first ROI before applying the ultrasound energy to the second ROI. In other embodiments, the applicator is not substantially moved from contact with or from being adjacent to the first ROI before applying the ultrasound energy to the second ROI.

[0144] For instance, in some embodiments, a method herein comprises scanning the applicator across an overall treatment area, and applying ultrasound energy to a plurality of ROI’s (e.g., n or x ROI’s). It should be understood, however, that it is also possible to treat multiple ROI’s without moving or scanning the applicator across an overall treatment area. For instance, in some embodiments, the actuation regions of the applicator can be individually and independently addressable, controlled, actuated, activated, turned on, and / or usable for providing an ultrasound treatment, and / or a distance between adjacent activation regions can be varied throughout the applicator surface, such that a plurality of differing depths of treatment to be achieved simultaneously and / or with the same applicator without moving the same from one region of treatment to another. In some embodiments, each of the actuation regions may be activated using different energy parameters, such as different frequencies, different intensities, different durations, and / or different powers.

[0145] In one aspect, a method as described herein further comprises reconfiguring electrical-mechanical switches or multiplexers after applying the ultrasound energy to the first ROI and before applying the ultrasound energy to the second ROI, thereby targeting the second ROI instead of the first ROI without substantially moving the applicator.

[0146] Skin treatment method disclosed herein can be for aesthetic, medical, or other purposes. That is, in some embodiments, a method described herein provides an aesthetic effect, a medical effect, a therapeutic effect, or a combination of the foregoing. In some instances, a method described herein provides an aesthetic effect but not a medical or therapeutic effect. As understood by one of ordinary skill in the art, an aesthetic effect is an effect related primarily to a subject’s appearance, with no benefit or minimal benefit to the physical health of the subject, or without treating a disease or ailment of the subject. A medical or therapeutic effect, in contrast, is an effect related primarily to treatment of a disease, ailment, or other condition of a subject that is not necessarily associated with the subject’s appearance but is instead primarily related to physical health.

[0147] Methods described herein, in some cases, can also comprise or be characterized by certain additional steps or features (or a combination of additional steps and features) that can provide one or more advantages compared to other methods.IV. Additional Treatment Methods

[0148] Methods of treating a human or animal subject or biological tissue of a human or animal subject using ultrasound are also described herein. In some embodiments, such a method comprises positioning an ultrasound transducer assembly or ultrasound treatment system described hereinabove in Section I or Section II on a region of biological tissue to be treated, and treating a region of biological tissue of interest with an ultrasound beam or pressure wave emitted from the ultrasound transducer assembly or treatment system. Moreover, the foregoing process can be repeated a desired number of times to treat a region of biological tissue. That is, multiple regions of biological tissue, target volumes, and / or target depths differing from one another can be treated with an ultrasound transducer assembly or treatment system as described herein.

[0149] Thus, in some cases, a method described herein further comprises positioning an ultrasound transducer array or treatment system (or portion thereof, such an applicator thereof) on x additional target volumes of a region of biological tissue for x additional time periods. It is to be understood that the n additional target volumes differ from one another and from the first target volume, and x can be any integer not inconsistent with the technical objectives of the present disclosure, such as an integer from 2 to 1,000,000. It is further to be understood that each target volume can denote or correspond to a different treatment location.

[0150] Additionally, it is to be understood that, when an ultrasound treatment system described in Section II is employed in the treatment methods herein, n propagating acoustic waves may be generated, and n main beams or lobes of the n propagating acoustic waves, respectively, do not overlap each other by more than 75%, more than 60%, more than 50%, more than 45%, more than 40%, more than 35%, more than 30%, more than 25%, more than 20%, more than 15%, more than 10%, or more than 5% at the distance Z described above.

[0151] The ultrasound energy can have any properties and be provided in any manner not inconsistent with the technical objectives of the present disclosure. In some cases, for instance, the ultrasound energy is provided as pulsed ultrasound beams. Such beams, in some instances, can be provided by one or more ultrasound treatment systems as described hereinabove in Section II. In addition, in some embodiments described herein, a focus of one or more ultrasound beams is positioned in a target volume (or a plurality or series of target volumes). Moreover, the focus of an ultrasound beam described herein can have any size and shape not inconsistent withthe technical objectives of the present disclosure, including the characteristics described in Section III above.

[0152] Moreover, a method described herein can be used to treat any type of biological tissue not inconsistent with the objectives of the present disclosure. Treatment can be for aesthetic, medical, or other purposes. For example, in some cases, the biological tissue comprises skin tissue, adipose tissue, connective tissue, muscle tissue, nerve tissue, cartilage, and / or gland tissue. Further, in some embodiments, a method described herein is used to target fat cells and / or other causes of cellulite. In other cases, a method described herein is used to target tissue components causing skin laxity. In some embodiments, a method described herein is used to target lentigo or “port wine stain” tissues; tissue components causing rhytids or wrinkles; tissue containing inks from tattoos for tattoo removal purposes; glands or other tissue causing hyperhidrosis; tissue causing incontinence; glands or other tissue causing sialorrhea; scar tissue; and / or seborrheic keratosis. In some embodiments, a method described herein provides an aesthetic effect, a medical or therapeutic effect, or a combination of the foregoing.

[0153] Methods described herein, in some cases, can also comprise or be characterized by certain additional steps or features (or a combination of additional steps and features) that can provide one or more advantages compared to other methods. It is further to be understood that the treated region of biological tissue generally does not refer to the entire treated organism (e.g., to the entire human subject or to the human subject’s body in its entirety), but instead to a specific treated area of the organism, such as an area or volume of the skin, muscle, fat, nerves, or glands of the subject having an area or volume of no greater than about 1000 cm2or 1000 cm3.V. Methods of Making Ultrasound Transducer Assemblies

[0154] In another aspect, a method of making an ultrasound transducer assembly is provided. In some embodiments, the ultrasound transducer assemblies described hereinabove in Section I may be manufactured by a method as disclosed herein.

[0155] A method of making a transducer assembly comprises providing an ultrasound producing material or layer (e.g., a piezoelectric material) having a first surface and a second surface, wherein the second surface is on an opposite side of the ultrasound producing material from the first surface, defining a metallization pattern on the first surface of the ultrasoundproducing material, and metallizing the first surface of the ultrasound producing material according to the metallization pattern.

[0156] Any ultrasound producing material described in Section I hereinabove or elsewhere in this disclosure may be employed in methods herein. For instance, in some embodiments, the ultrasound producing material may be a single crystal, a polycrystalline material, a composite material, a piezoelectric ceramic material, and / or any material exhibiting piezoelectric behavior or capable of producing ultrasound waves from an electrical stimulus (e.g., a CMUT structure). In some embodiments, the ultrasound producing material may be porous. Specific examples of ultrasound producing materials include, for example, piezoelectric materials such as lead zirconate titanate (PZT), lead magnesium niobate (PMN), lead magnesium niobate-lead titanate (PMN-PT), barium titanate (BaTiCh), zinc oxide (ZnO), aluminum nitride (AIN), gallium phosphate (GaPCri), and potassium sodium niobate. Other examples of ultrasound producing materials include CMUT, PMUT, and / or polymer MUT structures.

[0157] In some embodiments, the ultrasound producing material defines or is disposed on or formed by a single plate. For example, such an ultrasound producing plate may be a crystalline piezoelectric plate, polycrystalline piezoelectric plate, or composite piezoelectric plate. The ultrasound producing plate, in some embodiments, comprises or is formed from a CMUT, PMUT, polymer MUT, or other membrane-based mechanically vibrating structure.

[0158] The ultrasound producing plate may have any shape not inconsistent with the objectives of this disclosure. For instance, the ultrasound producing material may define or be disposed on or formed by a plano-convex structure, a plano-concave structure, a convex-concave structure, or a cylinder.

[0159] In embodiments herein, an ultrasound producing plate may have any thickness and / or width not inconsistent with the objectives of the present disclosure. For instance, in some embodiments, a thickness of an ultrasound producing plate may be selected so as to define a target or desired resonance frequency. In some embodiments, a width of an ultrasound producing plate may be selected so as to define a target or desired opening angle for an ultrasonic beam (“beam angle”). It is to be understood that ultrasound transducer assemblies described herein are not limited to having only one ultrasound producing material or one ultrasound producing plate, and may comprise a plurality of ultrasound producing materials and / or a plurality of ultrasound producing plates.

[0160] In some embodiments of methods described herein, the first surface of the ultrasound producing material is metalized with a conductive material. In some embodiments, the conductive material is one or more of gold, nickel, chrome, copper, or an alloy, combination, or mixture thereof. In other words, in some embodiments, the metallization pattern is formed from or defined by gold, nickel, chrome, copper, or an alloy, combination, or mixture thereof.

[0161] In one aspect, the metallization pattern is formed from or defined by an electrically conductive film or tape. In some embodiments, the metallization pattern may be defined using photolithography, a dicing saw, a water saw, or a laser.

[0162] In one aspect, metallizing the first surface of the ultrasound producing layer forms a first plurality of strips of the conductive material along a first direction in a lateral plane of the ultrasound producing material according to the metallization pattern, and a second plurality of strips of the conductive material along a second direction in the lateral plane. In some embodiments, the first plurality of strips and the second plurality of strips intersect to form one or more overlapping regions in the lateral plane. In embodiments herein, the one or more overlapping regions form or define one or more actuation regions. In some embodiments, a plurality of overlapping regions is formed. When a plurality of overlapping regions is formed, the overlapping regions may define an array of coherent actuation regions. It should be understood that the one or more actuation regions may be similar to each other in terms of size, shape, and / or distance therebetween, or may differ from each other in terms of size, shape, and / or distance therebetween.

[0163] It is also to be understood that ultrasound transducer assemblies manufactured by a method herein may comprise a plurality of actuation regions, wherein the plurality of actuation regions comprises n individual actuation regions, where n is an integer between 2 and 65,536. Furthermore, when the ultrasound assembly described herein comprises n individual actuation regions, the n individual actuation regions are each designed to be operable to produce, respectively, n propagating acoustic waves in n directions perpendicular to n top surfaces of the n individual actuation regions. Additionally, in some cases, the n individual actuation regions are each designed such that n main beams or lobes of the n propagating acoustic waves, respectively, do not overlap each other by more than 50%, more than 45%, more than 40%, more than 35%, more than 30%, more than 25%, more than 20%, more than 15%, more than 10%, or more than 5% at the distance Z away from the surface of the ultrasound producing material in the ndirections of the n propagating acoustic waves. In this manner and as described further herein, an ultrasound transducer assembly manufactured by the methods described herein can provide virtually any number of individual actuation regions. Such individual actuation regions can be individually and independently addressable, controlled, activated, and / or usable for providing an ultrasound treatment. Each of the n actuation regions may have any properties, features, characteristics, shapes, and / or dimensions as discussed in Section I hereinabove or elsewhere in this disclosure.

[0164] In one aspect, the plurality of actuation regions forms or defines a two-dimensional (2D) array. In some embodiments, the actuation regions are orthogonally opposed to each other, and define a row-column pattern. Other configurations are also possible, such as linear arrays, curved arrays, annular arrays, or circular arrays. In some embodiments, an array of actuation regions is periodic, such that a distance between adjacent actuation regions is constant or similar throughout the entirety of the array. In other embodiments, the array is aperiodic, such that distances between adjacent actuation regions are dissimilar and vary throughout the array. Aperiodic arrays allow for a plurality of differing depths of treatment to be achieved simultaneously and / or with the same device.

[0165] In some embodiments, a distance between adjacent actuation regions in an array is greater than 25 microns, greater than 50 microns, greater than 75 microns, greater than 100 microns, greater than 150 microns, greater than 200 microns, greater than 250 microns, greater than 300 microns, greater than 350 microns, greater than 400 microns, or greater than 450 microns. In some embodiments, a distance between adjacent actuation regions is at least 0.5 mm, at least 0.55 mm, at least 0.6 mm, at least 0.7 mm, at least 0.8 mm, at least 0.9 mm, or at least 1 mm. In some embodiments, a distance between adjacent actuation regions is up to 5 mm, up to 10 mm, or up to 15 mm.

[0166] In one aspect, a method herein further comprises attaching a matching layer to the first surface of the ultrasound producing material. In another aspect, a method herein further comprises attaching a backing layer to the second surface of the ultrasound producing material.

[0167] Figure 6 shows an exemplary method of fabricating an ultrasound transducer assembly in accordance with an embodiment herein. In the exemplary embodiment of Figure 6, a flat ultrasound producing plate (60) is patterned on the top (Figure 6A) and bottom (Figure 6B) with row (62) and column electrodes (64). Since control of the delay is not required, theelectrodes (62, 64) oriented in the x-direction and y-direction can be electrically connected using a bus (shown connecting the rows 62 in Figure 6A or the columns 64 in Figure 6B). An isolation cut (67, 68) may be used to eliminate the possibility of electro-mechanical crosstalk between the top surface and bottom surfaces of the plate. The overlap of the top and bottom electrodes (as shown in Figure 6C) define the actuation regions (66) on the plate (60).

[0168] It is possible in some cases for row and column electrodes on the top and bottom surfaces of the ultrasound producing plate to be used to generate independent actuation regions (the ‘net active area’ is denoted as 3000C in Figure 30C). However, as shown in Figure 30, other ways to obtain the same or similar actuation regions may also be employed, and electrodes do not necessarily need to be row and column strips. For example, in some embodiments, a plate can be patterned with individual actuation regions, and then the actuation regions (the squares 3014 in area 3000A) can be electrically connected to each other (as shown by the vertical lines 3016 connecting squares 3014 in area 3000A) as shown in Figure 30A (‘top’). In other embodiments, columns (the vertically oriented rectangles 3014 in Figure 30B) can be electrically connected together (Figure 30B, ‘bottom’, where the horizontal lines 3016 show the electrical connections between columns 3014).

[0169] Methods described herein, in some cases, can also comprise or be characterized by certain additional steps or features (or a combination of additional steps and features) that can provide one or more advantages compared to other methods.VI. Examples

[0170] Figures 7 and 9 show exemplary actuation regions (squares 70 in Figure 7, and squares 90 in Figure 9) of an assembly in accordance with embodiments herein. In this exemplary embodiment, the separation distance (kerfs or streets 72 in Figure 7, and kerfs or streets 92 in Figure 9) between adjacent actuation regions is 1 mm, and the size of each actuation region (70, 90) is 1 mm by 1 mm. This device has a total of 49 actuation regions (7 by 7, with rows labeled 1-7 and columns labeled A-G).

[0171] Figure 8 shows the simulated acoustic intensity from the device described in Figure 7 when operating at 10 MHz. The acoustic intensity is measured 2 mm away in a plane parallel to the transducer surface described in Figure 7. The intensity pattern shows that each actuation region creates an independent intensity pattern, and there is no noticeable acoustic intensity inthe gaps (72) between actuation regions (70). Finally, the intensity pattern from each actuation region is identical. Figure 10 shows the simulated acoustic intensity from the device described in Figure 9 (which is similar to the device in Figure 7) when operating at 10 MHz. The acoustic intensity is measured in a plane normal to the transducer surface described in Figure 9, as indicated by lines 10—10. The intensity pattern shows that each actuation region creates an independent intensity pattern in depth and there is no noticeable acoustic intensity in the gaps (92) between actuation regions (90). Again, the intensity pattern in depth is uniform.

[0172] Figure 11 shows the simulated pressure on a 1 mm diameter transducer operating at 10 MHz as a function of radial distance when the total power is 1.5 W, with an on-time of 1 second and an off-time of 3 seconds. Figure 12 shows the simulated intensity on a 1 mm diameter transducer operating at 10 MHz as a function of radial distance when the total power is 1.5 W, with an on-time of 1 second and an off-time of 3 seconds.

[0173] Figure 13 shows the simulated on-axis pressure from a 1 mm diameter transducer operating at 10 MHz with 1.5 W as a function of depth, with an on-time of 1 second and an off- time of 3 seconds. The near field to far field transition point is clearly identified at approximately 1.5 mm (dashed line 1322). Figure 14 shows the simulated on-axis intensity from a 1 mm diameter transducer operating at 10 MHz with 1.5 W as a function of depth, with an on- time of 1 second and an off-time of 3 seconds. The near field to far field transition point is clearly identified at approximately 1.5 mm (dashed line 1422).

[0174] Figure 15 shows the simulated maximum temperature in tissue from a 1 mm diameter transducer operating at 10 MHz with 1.5 W, and an on-time of 1 second and an off-time of 3 seconds. The thermal simulation shows that coagulative temperatures are achieved.

[0175] Figure 16 shows the simulated temperature in tissue at the spatial peak as a function of time from a 1 mm diameter transducer operating at 10 MHz with 1.5 W, an on-time of 1 second, and an off-time of 3 seconds. The dashed vertical line in Figure 16 shows the division between on-time and off-time.

[0176] Figure 17 shows the simulated thermal dose as a function of radial distance and depth from a 1 mm diameter transducer operating at 10 MHz with 1.5 W, an on-time of 1 second, and an off-time of 3 seconds. The coagulation region is identified as the area within the 240 equivalent minute contour, based on the concept of cumulative equivalent minutes at 43°C (CEM43°C), which is a standard metric used to quantify thermal dose in hyperthermiatreatments and thermal damage studies. This model converts any time-temperature history to an equivalent number of minutes of heating at 43°C (see, e.g., van Rhoon et al., “CEM43°C thermal dose thresholds: a potential guide for magnetic resonance radiofrequency exposure levels?” Eur Radiol. 2013 Apr 4;23(8):2215-2227. doi: 10.1007 / s00330-013-2825-y).

[0177] Figure 18 shows the simulated maximum temperature in tissue from a 1 mm diameter transducer operating at 10 MHz with 1.5 W, and an on-time of 0.6 second and an off-time of 3.4 seconds. The thermal simulation shows that coagulative temperatures are achieved.

[0178] Figure 19 shows the simulated temperature in tissue at the spatial peak as a function of time from a 1 mm diameter transducer operating at 10 MHz with 1.5 W, an on-time of 0.6 second, and an off-time of 3.4 seconds. The energy applied to tissue is reduced by 40% when compared to Figure 16.

[0179] Figure 20 shows the simulated thermal dose as a function of radial distance and depth from a 1 mm diameter transducer operating at 10 MHz with 1.5 W, an on-time of 0.6 second, and an off-time of 3.4 seconds. The coagulation region is identified as the area within the 240 equivalent minutes at 43 °C contour. Although the energy was reduced by 40% when compared to Figure 17, a coagulation region is still achieved with 0.9 J.

[0180] Figure 21 shows the simulated maximum temperature in tissue from a 1.69 mm diameter transducer operating at 7 MHz with 2.5 W, and an on-time of 0.8 second. The thermal simulation shows that coagulative temperatures are achieved.

[0181] Figure 22 shows the simulated temperature in tissue at the spatial peak as a function of time from a 1.69 mm diameter transducer operating at 7 MHz with 2.5 W, with an on-time of 0.8 second, and an off-time of 3.2 seconds. The energy applied to tissue is increased by 33% when compared to Figure 16.

[0182] Figure 23 shows the simulated thermal dose as a function of radial distance and depth from a 1.69 mm diameter transducer operating at 7 MHz with 2.5 W, with an on-time of 0.8 second, and an off-time of 3.2 seconds. The coagulation region is identified as the area within the 240 equivalent minute at 43°C contour. Although the energy is increased by 33% when compared to Figure 17, a coagulation region is still achieved with the less absorptive 7 MHz frequency.

[0183] Figure 24 shows exemplary top (Figure 24A) and bottom (Figure 24B) electrode patterns (2400 and 2400’) in accordance with embodiments herein. The top and bottom electrodepatterns (2400 and 2400’) in Figure 24A and 24B interdigitated designs for both sides. Figure 24A shows electrodes (2410 and 2412) that run vertically and are interdigitated with one another, whereas Figure 24B shows electrodes (2420 and 2422) that run horizontally and are interdigitated with one another. In this exemplary embodiment, the thinner electrodes (2410 in Figure 24A and 2420 in Figure 24B) have an electrode width of 1 mm, and the thicker electrodes (2412 in Figure 24A and 2422 in Figure 24B) have an electrode width of 1.8 mm. It should be noted that in Figure 24 (and in other similar figures described below) the electrodes (2410, 2412, 2420, 2422) are illustrated along with any associated buses, for convenience of illustration (similar to Figure 6A, except the bus 61 in Figure 6A is separately labeled).

[0184] Another exemplary embodiment is shown in Figure 25. In Figure 25A, the electrodes that run vertically (2510 and 2512) are depicted with distinct hatching patterns (rather than different colors, such as green and blue) to identify regions that are electrically connected. The electrical busses for the first set of vertical electrodes (2510) and for the second set of vertical electrodes (2512) are on opposite sides of the device surface (2500, 2500’) to enable connection. In Figure 25B, the electrodes that run horizontally (2520 and 2522) are depicted with distinct hatching patterns (rather than different colors such as red and orange) to identify regions that are electrically connected.

[0185] In both Figure 24 and Figure 25, the ultrasound producing material is a PZT plate (20.0 mm by 20.0 mm; polycrystalline or composite), and metallization is either gold or silver or other solder appropriate metal (e.g., copper). The bus is 1.5 mm wide. There are eight strips on the front and back of the PZT plate. The overlap of strips define 1 mm square elements (actuation regions). Thus, the 2D array defines 64 potential heating sites, with 1.0 W to 3.0 W acoustic power per element. At 50% efficiency, this would correspond to an electric power of 128 W to 384 W.

[0186] Figure 26A is an electrical schematic that shows a switch (2600 or 2610) to either connect the “green” electrodes (depicted as 2510 in Figure 25 A) or the “blue” electrodes (depicted as 2512) to ground. Figure 26B is an electrical schematic that shows a switch to either connect the “orange” electrodes (2412 in Figure 24A or 2422 in Figure 24B, the thicker electrodes) or the “red” electrodes (2420 or 2422 in Figure 24B) to the excitation source. The ground for the voltage source in Figure 26B is not shown.

[0187] As shown in Figure 29 A, when one electrical switch is connected to the “green” electrodes (2910) and the other electrical switch is connected to the “orange” electrodes (2920), then the highlighted “purple” regions (2914a) are the active actuation regions (overlap of the “green” and “orange” regions). Each actuator region is 1 mm by 1 mm. This is configuration 2900a.

[0188] As shown in Figure 29B, if one electrical switch is connected to “green” electrodes (2910) and the other electrical switch is connected to the “red” electrodes (2922), then the highlighted “purple” regions (2914b) are the active actuation regions (overlap of the “green” and “red” regions). This is configuration 2900b.

[0189] Figure 29C shows that, if one electrical switch is connected to the “blue” electrodes (2912) and the other electrical switch is connected to the “red” electrodes (2922), then the highlighted “purple” regions (2914c) are the active actuators (overlap of the “blue” and “red” regions). This is configuration 2900c.

[0190] Figure 29D illustrates that, if one electrical switch is connected to the “blue” electrodes (2912) and the other electrical switch is connected to the “orange” electrodes (2920), then the highlighted “purple” regions (2914d) are the active actuators (overlap of the “blue” and “orange” regions). This is configuration 2900d.

[0191] Figure 27 shows the lateral beamwidth for different actuation region sizes when operating at 10 MHz. If the region size is 1 mm (as in the case of Figure 29A), then the width of the beam at the depth of peak intensity is 0.35 mm. If the actuation region size is 1.8 mm (as in the case of Figure 29C), then the width of the beam at the depth of peak intensity is 0.6 mm.

[0192] Figure 28 illustrates the depth of peak intensity for different actuation region sizes when operating at 10 MHz. If the region size is 1 mm, then the depth of peak intensity is approximately 2 mm. If the region size is 1.8 mm, then the depth of peak intensity is approximately 7 mm.

[0193] Figure 31 illustrates an exemplary device design, wherein the electrode width is 1 mm and the separation distance between electrodes is 1.2 mm. In this exemplary embodiment, the plate size is 29.2 mm by 29.2 mm. Figure 31 A shows the electrode pattern (3110) on the top (3100A) of the ultrasound producing plate. Figure 3 IB shows the electrode pattern (3112) on the bottom (3100B) of the ultrasound producing plate. Figure 31C shows the overlap regions (view 3100C) between the top electrodes (3120) and the bottom electrodes (3122). In Figure 3 ID, it ispossible to identify the actuation regions, which are the overlapping regions (3114) of the top and bottom electrodes (3120, 3122). Fig. 3 IE shows the resulting 144 actuation regions (3114) for this exemplary design, without depicting the electrodes themselves (view 3100E rather than view 3100D).

[0194] Figure 32 illustrates an exemplary device design, wherein the electrode width is 1 mm and the separation distance between electrodes is 1.2 mm. When compared to Figure 31, it is evident that the novel designs and methods herein are scalable (since the plate size is 20 mm by 20 mm). Figure 32A shows the electrode pattern (3210) on the top (3200 A) of the ultrasound producing plate. Figure 32B shows the electrode pattern (3220) on the bottom (3200B) of the ultrasound producing plate. Figure 32C shows the overlap regions (view 3200C) between the top electrode (3220) and the bottom electrode (3222). In Figure 32D, the overlapping regions (3214) of the top and bottom electrodes (3220, 3222) identify the actuation regions. Figure 32E shows the resulting 64 actuation regions (3214) for this exemplary design.

[0195] Figure 33 shows an exemplary actuator design that enables two different treatment depths simultaneously. In one case, the actuator size is SI with a separation distance of Pl and a therapeutic depth of DI. In another case, the effective actuator size is S2 with a separation distance of P2, which has a therapeutic treatment depth of D2. In the first case, 48 therapeutic regions (3314) at a depth DI are created. In the second case, 12 therapeutic regions (two of which are labeled as 3317 and 3319) at a depth D2 are created. In this embodiment, an ultrasound transducer assembly comprises a plurality of sets (3317, 3319) of actuation regions (3314, 3314A, 3314B), such as the groups of four square actuation regions defining the distance S2 as depicted in Figure 33. Each set of actuation regions itself comprises a plurality of actuation regions (e.g., 3314, 3314A, or 3314B as depicted in Figure 33) separated by a plurality of non-actuation regions (e.g., the kerfs or streets 3321 defining distance Pl, or the orthogonal kerfs or streets 3320 in the embodiment depicted in Figure 33). The actuation regions and nonactuation regions within each set can have any structure and composition of any ultrasound transducer array described herein. Moreover, each set of actuation regions (e.g., where each set consists of a group of four more closely spaced actuation regions in Figure 33, such as shown by the dashed lines in Figure 33) can together define a virtual actuator (e.g., denoted as 3317 or 3319 in Figure 33), having an effective actuator size of S2 (as depicted in Figure 33) andseparated from other virtual actuators by a distance P2 (e.g., by broader kerfs or streets 3322 or 3323, as depicted in Figure 33).

[0196] Thus, in some embodiments described herein, an ultrasound transducer assembly described herein comprises an ultrasound producing material and a plurality of virtual actuators (e g., 3317 and 3319 in Figure 33) on a surface of the ultrasound producing material, wherein the virtual actuators (e.g., 3317 and 3319) each comprise a plurality of actuation regions (e.g., 3314A and 3314B) on a surface of the ultrasound producing material separated by at least one non-actuation region on the surface of the ultrasound producing material, by an average first separation distance (Pl). Additionally, the virtual actuators are separated from one another by at least one non-actuation region on the surface of the ultrasound producing material, by an average first separation distance (P2). Moreover, P2 is larger than Pl. In some cases, P2 is at least twice as large as Pl. In some instances, P2 is 2-10 or 2-20 times the size of Pl. Further, in some cases, the plurality of actuation regions forming a single virtual actuator have an average size in two dimensions (SI) that differs from and is smaller than the average size in two dimensions of the virtual actuator itself (S2). In some instances, S2 is more than 2 times the size of SI. In some cases, S2 is 2.5-50, 2.5-20, or 2.5-10 times the size of SI.

[0197] Moreover, in some instances, each of the actuation regions within a specific virtual actuator can have the same properties with respect to the production of a propagating acoustic wave. For example, each actuation region within the same virtual actuator (e.g., each of the four 3314A elements within 3317 in Figure 33) can have the same or substantially the same size, composition, and / or focal depth. Further, in some cases, differing virtual actuators (e.g., 3317 and 3319 in Figure 33) in the assembly can comprise individual actuation regions that differ from one another (such as in size, composition, and / or focal depth) (e.g., the actuation regions denoted as 3314A may be formed from a different material than the actuation regions denoted as 3314B in Figure 33). In this manner, differing virtual actuators can provide ultrasound treatment at different depths or at different powers, as compared to one another. Yet, in some cases, all of the virtual actuators (or at least multiple of the virtual actuators of an assembly) can be operated at the same time to provide propagating acoustic waves in a manner described herein, with the result that a single assembly formed from a plurality of virtual actuators can provide complex treatment to a patient (e.g., at varying depths) at the same time.

[0198] Figure 34 A, Figure 34B, and Figure 34C illustrate ultrasound transducer embodiments in which passive materials are used to block or transmit acoustic waves. Figure 34A is an “assembled” view of one such embodiment. Figure 34B is an “exploded” view of the device of Figure 34A, for illustration purposes. Figure 34C is an exploded view of an alternative device, as compared to the device of Figure 34A and 34B. It is to be understood that a depiction of the device of Figure 34C in an “assembled” view rather than an “exploded” view would be analogous to Figure 34A.

[0199] With reference to Figure 34A and Figure 34B, an ultrasound producing material (a piezoelectric plate, 3410) comprises an electrode (3420) on a first side (3411) of the plate (3410). An acoustic backing layer (3430) can be disposed on a second side (3412) of the plate (3410). The acoustic backing layer (3430) can comprise acoustic reflective regions (3432), which in some cases may be or be formed from air, or a low acoustic impedance “kerf fill” material, a much harder material than the piezoelectric plate (e.g., a metal), or an appropriate defined acoustic transmission line of the appropriate thickness and acoustic impedance. The acoustic reflective regions (3432) can propel acoustic waves forward, in the direction of sound propagation arrow (3440). The acoustic backing layer (3430) can also comprise acoustic matching regions (3431) to allow absorption of sound into the backing layer (3430). The combination of absorption regions (3431) and reflective regions (3432) define the individual actuator regions of this device.

[0200] Figure 34C depicts an alternative embodiment. In Figure 34B, an ultrasound producing material (a piezoelectric plate, 3410) comprises an electrode (3420) on a first side (3411) of the plate (3410). An acoustic matching layer (3430) can be disposed on a second side (3412) of the plate (3410). The acoustic matching layer (3430) can comprise or be formed from either regions such as air, a low acoustic impedance “kerf fill,” a much harder material than the piezoelectric plate (e.g., a metal), a highly absorptive material, or an acoustic transmission line with the appropriate thickness and acoustic impedance in acoustic loss regions (3432). The acoustic loss regions (3432) prevent ultrasound from propagating in the direction of the sound propagation arrow (3440) either through absorption or reflection. The acoustic matching layer (3430) can also comprise acoustic matching regions (3431) to allow ultrasound energy to pass through when designed at the correct thickness and acoustic impedance to enable sound to propagate in the direction of sound propagation arrow (3440). The combination of acoustic lossregions (3432) and the acoustic matching regions (3431) define the actuator regions in this nonlimiting example structure.

[0201] Additionally, a plate with an acoustic backing layer and an acoustic matching layer may also be used to further define the actuator regions from the piezoelectric plate.VII. Additional Assemblies, Systems, and Methods

[0202] Some additional exemplary, non-limiting embodiments of assemblies, systems, and methods are provided below.

[0203] Embodiment 1. An ultrasound transducer assembly, comprising a ultrasound producing material; a plurality of actuation regions on a surface of the ultrasound producing material, wherein the plurality of actuation regions comprises at least a first actuation region and a second actuation region; and at least one non-actuation region on the surface of the ultrasound producing material separating the first actuation region from the second actuation region, wherein the first actuation region is operable to produce a first propagating acoustic wave in a direction perpendicular to a top surface of the first actuation region; wherein the second actuation region is operable to produce a second propagating acoustic wave in a direction perpendicular to a top surface of the second actuation region; wherein a main beam or lobe of the first propagating acoustic wave and a main beam or lobe of the second propagating acoustic wave do not overlap each other by more than 30% at a distance Z away from the surface of the ultrasound producing material in the direction of the first propagating acoustic wave and / or in the direction of the second propagating acoustic wave; and wherein the distance Z is a therapeutic distance of the ultrasound transducer assembly.

[0204] Embodiment 2. The ultrasound transducer assembly of Embodiment 1, wherein the plurality of actuation regions comprises at least a third actuation region; at least one nonactuation region on the surface of the ultrasound producing material separates the third actuation region from the first actuation region and / or from the second actuation region, the third actuation region is operable to produce a third propagating acoustic wave in a direction perpendicular to a top surface of the third actuation region; a main beam or lobe of the third propagating acoustic wave does not overlap with the main beam or lobe of the first propagating acoustic wave by more than 30% at a distance Z away from the surface of the ultrasound producing material in the direction of the first propagating acoustic wave and / or in the direction of the third propagatingacoustic wave, and / or does not overlap with the main beam or lobe of the second propagating acoustic wave by more than 30% at a distance Z away from the surface of the ultrasound producing material in the direction of the second propagating acoustic wave and / or in the direction of the third propagating acoustic wave.

[0205] Embodiment 3. The ultrasound transducer assembly of any of the preceding Embodiments, wherein the plurality of actuation regions on the surface of the ultrasound producing material comprises n individual actuation regions; the assembly comprises (1 to m) non-actuation regions on the surface of the ultrasound producing material separating the n individual actuation regions from one another; the n individual actuation regions are operable to produce, respectively, n propagating acoustic waves in n directions perpendicular to n top surfaces of the n individual actuation regions; n main beams or lobes of the n propagating acoustic waves, respectively, do not overlap each other by more than 30% at the distance Z away from the surface of the ultrasound producing material in the n directions of the n propagating acoustic waves; n is an integer ranging from 2 to 65,536; and m is an integer ranging from 2 to 65,536.

[0206] Embodiment 4. The ultrasound transducer assembly of any of the preceding Embodiments, wherein the plurality of actuation regions forms or defines an array of actuation regions.

[0207] Embodiment 5. The ultrasound transducer assembly of any of the preceding Embodiments, wherein the assembly comprises a first set of electrodes extending in a first direction parallel to the surface of the ultrasound producing material; the assembly comprises a second set of electrodes extending in a second direction parallel to the surface of the ultrasound producing material; the first direction and the second direction are orthogonal or substantially orthogonal to one another; and the plurality of actuation regions is formed by the overlap of the first set of electrodes with the second set of electrodes.

[0208] Embodiment 6. The transducer assembly of Embodiment 5, wherein the first set of electrodes and / or the second set of electrodes comprises or is formed from gold, nickel, chrome, copper, or an alloy, combination, or mixture thereof.

[0209] Embodiment 7. The transducer assembly of Embodiment 5 or Embodiment 6, wherein the first set of electrodes and / or the second set of electrodes comprises or is formed from an electrically conductive film or tape.

[0210] Embodiment 8. The ultrasound transducer assembly of any of the preceding Embodiments, wherein the non-actuation region separates the first actuation region from the second actuation region by a distance greater than 50 microns.

[0211] Embodiment 9. The ultrasound transducer assembly of any of the preceding Embodiments, wherein the non-actuation region separates the first actuation region from the second actuation region by a distance of at least 1 mm.

[0212] Embodiment 10. The ultrasound transducer assembly of any of the preceding Embodiments, wherein the at least one non-actuation region is formed from an electrically insulating material.

[0213] Embodiment 11. The ultrasound transducer assembly of any of the preceding Embodiments, wherein the at least one non-actuation region comprises, consists of, or is formed from the ultrasound producing material of the array.

[0214] Embodiment 12. The transducer assembly of any of the preceding Embodiments, wherein the ultrasound producing material defines or is disposed on or formed by a single plate.

[0215] Embodiment 13. The transducer assembly of Embodiment 12, wherein the ultrasound producing plate is a polycrystalline ultrasound producing plate or a composite ultrasound producing plate.

[0216] Embodiment 14. The transducer assembly of Embodiment 12 or 13, wherein the ultrasound producing plate comprises or is formed from: a piezoelectric material, wherein the piezoelectric material optionally comprises zirconate titanate (PZT), lead magnesium niobate (PMN), lead magnesium niobate-lead titanate (PMN-PT), barium titanate (BaTiCh), zinc oxide (ZnO), aluminum nitride (AIN), gallium phosphate (GaPCE), or potassium sodium niobate; or a capacitive micromachined ultrasonic transducer (CMUT) structure, a piezoelectric micromachined ultrasound transducer (PMUT) structure, and / or a polymer micromachined ultrasound transducer (polymer MUT) structure.

[0217] Embodiment 15. The transducer assembly of any of the preceding Embodiments, wherein the ultrasound producing material defines or is disposed on or formed by a plano-convex structure.

[0218] Embodiment 16. The transducer assembly of any of Embodiments 1-14, wherein the ultrasound producing material defines or is disposed on or formed by a plano-concave structure.

[0219] Embodiment 17. The transducer assembly of any of Embodiments 1-14, wherein the ultrasound producing material defines or is disposed on or formed by a convex-concave structure.

[0220] Embodiment 18. The transducer assembly of any of Embodiments 1-14, wherein the ultrasound producing material defines or is disposed on or formed by a cylinder.

[0221] Embodiments 19. The transducer assembly of any of the preceding Embodiments, further comprising a controller configured to receive an indication regarding interference of propagating acoustic waves from the transducer assembly.

[0222] Embodiment 20. The transducer assembly of any of Embodiments 5-19, wherein the first set of electrodes and the second set of electrodes are positioned on the same side of the ultrasound producing material.

[0223] Embodiment 21. The transducer assembly of any of Embodiments 5-20, wherein the first set of electrodes and the second set of electrodes are connected to an electrical-mechanical switch or multiplexer.

[0224] Embodiment 22. An ultrasound treatment system comprising the transducer assembly according to any of Embodiments 1-21, and an applicator for applying ultrasound energy to a subject using the transducer assembly.

[0225] Embodiment 23. The system of Embodiment 22, wherein the applicator comprises a distal face configured to contact a skin surface of the subject, and the ultrasound transducer assembly is positioned on the distal face of the applicator.

[0226] Embodiment 24. The system of any of Embodiments 1-23, wherein the plurality of actuation regions define one or more virtual actuators on the surface of the ultrasound generating material.

[0227] Embodiment 25. A method for treating skin of a subject in need thereof, the method comprising placing an applicator in contact with or adjacent to a first region of interest (RO I) on the skin, and applying ultrasound energy to the first ROI using the applicator, wherein the applicator comprises a plurality of actuation regions on a surface of a ultrasound producing material, wherein the plurality of actuation regions comprises at least a first actuation region and a second actuation region, wherein the applicator comprises at least one non-actuation region on the surface of the ultrasound producing material separating the first actuation region from the second actuation region, wherein the first actuation region is operable to produce a firstpropagating acoustic wave in a direction perpendicular to a top surface of the first actuation region, wherein the second actuation region is operable to produce a second propagating acoustic wave in a direction perpendicular to a top surface of the second actuation region, wherein a main beam or lobe of the first propagating acoustic wave and a main beam or lobe of the second propagating acoustic wave do not overlap each other by more than 30% at a distance Z away from the surface of the ultrasound producing material in the direction of the first propagating acoustic wave and / or in the direction of the second propagating acoustic wave, and wherein the distance Z is a therapeutic distance of the ultrasound transducer assembly.

[0228] Embodiment 26. The method according to Embodiment 25, wherein the ultrasound energy has a frequency of 100 kHz to 20 MHz.

[0229] Embodiment 27. The method according to Embodiment 25 or Embodiment 26, wherein applying ultrasound energy to the first ROI causes thermal damage to a tissue layer beneath a shallow or untargeted layer of skin (e.g., an epidermis of the skin).

[0230] Embodiment 28. The method according to Embodiment 27, wherein the thermal damage comprises a plurality of thermally damaged zones corresponding to the plurality of actuation regions of the applicator.

[0231] Embodiment 29. The method according to Embodiment 27 or Embodiment 28, wherein the plurality of thermally damaged zones correspond in a 1 : 1 manner to the plurality of actuation regions of the applicator.

[0232] Embodiment 30. The method according to any of Embodiments 25-29, wherein applying ultrasound energy to the first ROI does not cause thermal damage or coagulation to the shallow or untargeted layer of the skin (e.g., epidermis of the skin).

[0233] Embodiment 31. The method according to any of Embodiments 25-30, further comprising optionally moving the applicator from contact with or adjacent to the first ROI to place the applicator in contact with or adjacent to a second ROI differing from the first ROI; and applying ultrasound energy to the second ROI using the applicator.

[0234] Embodiment 32. The method of Embodiment 31, wherein applying ultrasound energy to the second ROI causes thermal damage to a tissue layer beneath an epidermis of the skin, differing from or in addition to thermal damage caused by applying ultrasound energy to the first ROI.

[0235] Embodiment 33. The method of Embodiment 32, wherein the thermal damage caused by applying ultrasound energy to the second ROI comprises a plurality of thermally damaged zones corresponding to the plurality of actuation regions of the applicator.

[0236] Embodiment 34. The method of Embodiment 33, wherein the plurality of thermally damaged zones caused by applying ultrasound energy to the second ROI correspond in a 1 : 1 manner to the plurality of actuation regions of the applicator.

[0237] Embodiment 35. The method according to any one of Embodiments 25-34, wherein applying ultrasound energy to the first ROI does not cause thermal damage or coagulation to the shallow or untargeted tissue (e.g., epidermis of the skin).

[0238] Embodiment 36. The method according to any one of Embodiments 25-35, wherein the applicator is moved from contact with or adjacent to the first ROI before applying the ultrasound energy to the second ROI.

[0239] Embodiment 37. The method according to any one of Embodiments 25-35, wherein the applicator is not substantially moved from contact with or adjacent to the first ROI before applying the ultrasound energy to the second ROI.

[0240] Embodiment 38. The method according to any one of Embodiments 25-37, further comprising reconfiguring electrical-mechanical switches or multiplexers after applying the ultrasound energy to the first ROI and before applying the ultrasound energy to the second ROI, thereby targeting the second ROI instead of the first ROI without substantially moving the applicator.

[0241] Embodiment 39. A method of making a transducer assembly, the method comprising providing a ultrasound producing material having a first surface and a second surface, wherein the second surface is on an opposite side of the ultrasound producing material from the first surface, defining a metallization pattern on the first surface of the ultrasound producing material, and metallizing the first surface of the ultrasound producing material with a conductive material according to the metallization pattern, wherein metallizing the first surface of the ultrasound producing layer forms a first plurality of strips of the conductive material along a first direction in a lateral plane of the ultrasound producing material according to the metallization pattern, and a second plurality of strips of the conductive material along a second direction in the lateral plane.

[0242] Embodiment 40. The method of Embodiment 39, wherein the first plurality of strips and the second plurality of strips intersect to form one or more overlapping regions in the lateral plane.

[0243] Embodiment 4E The method of any one of Embodiments 39 and 40, wherein the one or more overlapping regions form or define one or more actuation regions.

[0244] Embodiment 42. The method of any one of Embodiments 39-41, wherein a plurality of overlapping regions is formed, and the overlapping regions define an array of coherent actuation regions.

[0245] Embodiment 43. The method of any one of Embodiments 41-42, wherein the plurality of actuation regions defines a row-column pattern.

[0246] Embodiment 44. The method of any one of Embodiments 41-43, wherein a distance between adjacent actuation regions in the array is greater than 50 microns.

[0247] Embodiment 45. The method of any one of Embodiments 41-44, wherein the distance between adjacent actuation regions is at least 1 mm.

[0248] Embodiment 46. The method of any one of Embodiments 39-45, wherein the metallization pattern is formed from or defined by gold, nickel, chrome, copper, or an alloy, combination, or mixture thereof.

[0249] Embodiment 47. The method of any one of Embodiments 39-46, wherein the metallization pattern is formed from or defined by an electrically conductive film or tape.

[0250] Embodiment 48. The method of any one of Embodiments 39-47, wherein the metallization pattern is defined using photolithography.

[0251] Embodiment 49. The method of any one of Embodiments 39-48, wherein the metallization pattern is defined using a dicing saw.

[0252] Embodiment 50. The method of any one of Embodiments 39-49, wherein the metallization pattern is defined using a water saw.

[0253] Embodiment 51. The method of any one of Embodiments 39-50, wherein the metallization pattern is defined using a laser.

[0254] Embodiment 52. The method any one of Embodiments 39-51, wherein the ultrasound producing material defines or is disposed on or formed by a single plate.

[0255] Embodiment 53. The method of Embodiment 52, wherein the ultrasound producing plate is a polycrystalline ultrasound producing plate or a composite ultrasound producing plate.

[0256] Embodiment 54. The method of any one of Embodiments 52 or 53, wherein the ultrasound producing plate comprises or is formed from a CMUT, PMUT, polymer MUT, or membrane-based mechanically vibrating structure.

[0257] Embodiment 55. The method of any one of Embodiments 39-54, wherein the ultrasound producing material defines or is disposed on or formed by a plano-convex structure.

[0258] Embodiment 56. The method of any one of Embodiments 39-54, wherein the ultrasound producing material defines or is disposed on or formed by a plano-concave structure.

[0259] Embodiment 57. The method of any one of Embodiments 39-54, wherein the ultrasound producing material defines or is disposed on or formed by a convex-concave structure.

[0260] Embodiment 58. The method of any one of Embodiments 39-54, wherein the ultrasound producing material defines or is disposed on or formed by a cylinder.

[0261] Embodiment 59. The method of any one of Embodiments 39-58, further comprising attaching a matching layer to the first surface of the ultrasound producing material.

[0262] Embodiment 60. The method of any one of Embodiments 39-59, further comprising attaching a backing layer to the second surface of the ultrasound producing material.

Claims

CLAIMS1. An ultrasound transducer assembly comprising: an ultrasound producing material; a plurality of actuation regions on a surface of the ultrasound producing material, wherein the plurality of actuation regions comprises at least a first actuation region and a second actuation region; and at least one non-actuation region on the surface of the ultrasound producing material separating the first actuation region from the second actuation region, wherein the first actuation region is operable to produce a first propagating acoustic wave in a direction perpendicular to a top surface of the first actuation region; wherein the second actuation region is operable to produce a second propagating acoustic wave in a direction perpendicular to a top surface of the second actuation region; wherein a main beam or lobe of the first propagating acoustic wave and a main beam or lobe of the second propagating acoustic wave do not overlap each other by more than 30% at a distance Z away from the surface of the ultrasound producing material in the direction of the first propagating acoustic wave and / or in the direction of the second propagating acoustic wave; and wherein the distance Z is a therapeutic distance of the ultrasound transducer assembly.

2. The ultrasound transducer assembly of claim 1, wherein: the plurality of actuation regions comprises at least a third actuation region; at least one non-actuation region on the surface of the ultrasound producing material separates the third actuation region from the first actuation region and / or from the second actuation region, the third actuation region is operable to produce a third propagating acoustic wave in a direction perpendicular to a top surface of the third actuation region; a main beam or lobe of the third propagating acoustic wave does not overlap with the main beam or lobe of the first propagating acoustic wave by more than 30% at a distance Z away from the surface of the ultrasound producing material in the direction of the first propagating acoustic wave and / or in the direction of the third propagating acoustic wave, and / or does not overlap with the main beam or lobe of the second propagating acoustic wave by more than 30%at a distance Z away from the surface of the ultrasound producing material in the direction of the second propagating acoustic wave and / or in the direction of the third propagating acoustic wave.

3. The ultrasound transducer assembly of claim 1, wherein: the plurality of actuation regions on the surface of the ultrasound producing material comprises n individual actuation regions; the assembly comprises (1 to m) non-actuation regions on the surface of the ultrasound producing material separating the n individual actuation regions from one another; the n individual actuation regions are operable to produce, respectively, n propagating acoustic waves in n directions perpendicular to n top surfaces of the n individual actuation regions; n main beams or lobes of the n propagating acoustic waves, respectively, do not overlap each other by more than 30% at the distance Z away from the surface of the ultrasound producing material in the n directions of the n propagating acoustic waves; n is an integer ranging from 2 to 65,536; and m is an integer ranging from 2 to 65,536.

4. The ultrasound transducer assembly of claim 1, wherein the plurality of actuation regions forms or defines an array of actuation regions.

5. The ultrasound transducer assembly of claim 1, wherein: the assembly comprises a first set of electrodes extending in a first direction parallel to the surface of the ultrasound producing material; the assembly comprises a second set of electrodes extending in a second direction parallel to the surface of the ultrasound producing material; the first direction and the second direction are orthogonal or substantially orthogonal to one another; and the plurality of actuation regions is formed by the overlap of the first set of electrodes with the second set of electrodes.

6. The transducer assembly of claim 5, wherein the first set of electrodes and / or the second set of electrodes is formed from gold, nickel, chrome, copper, or an alloy, combination, or mixture thereof.

7. The transducer assembly of claim 5, wherein the first set of electrodes and / or the second set of electrodes is formed from an electrically conductive film or tape.

8. The ultrasound transducer assembly of claim 1, wherein the non-actuation region separates the first actuation region from the second actuation region by a distance greater than 50 microns.

9. The ultrasound transducer assembly of claim 1, wherein the non-actuation region separates the first actuation region from the second actuation region by a distance of at least 1 mm.

10. The ultrasound transducer assembly of claim 1, wherein the at least one non-actuation region is formed from an electrically insulating material.

11. The ultrasound transducer assembly of claim 1, wherein the at least one non-actuation region comprises, consists of, or is formed from the ultrasound producing material of the array.

12. The transducer assembly of claim 1, wherein the ultrasound producing material defines or is disposed on or formed by a single plate.

13. The transducer assembly of claim 12, wherein the ultrasound producing plate is a polycrystalline ultrasound producing plate or a composite ultrasound producing plate.

14. The transducer assembly of claim 1, wherein the ultrasound producing material is formed from a piezoelectric material.

15. The transducer assembly of claim 14, wherein the piezoelectric material comprises zirconate titanate (PZT), lead magnesium niobate (PMN), lead magnesium niobate-lead titanate (PMN-PT), barium titanate (BaTiCh), zinc oxide (ZnO), aluminum nitride (AIN), gallium phosphate (GaPO i), or potassium sodium niobate.

16. The transducer assembly of claim 1, wherein the ultrasound producing material comprises a capacitive micromachined ultrasonic transducer (CMUT) structure, a piezoelectric micromachined ultrasound transducer (PMUT) structure, and / or a polymer micromachined ultrasound transducer (polymer MUT) structure.

17. The transducer assembly of claim 1, wherein the ultrasound producing material defines or is disposed on or formed by a plano-convex structure.

18. The transducer assembly of claim 1, wherein the ultrasound producing material defines or is disposed on or formed by a plano-concave structure.

19. The transducer assembly of claim 1, wherein the ultrasound producing material defines or is disposed on or formed by a convex-concave structure.

20. The transducer assembly of claim 1, wherein the ultrasound producing material defines or is disposed on or formed by a cylinder.

21. The transducer assembly of claim 1, further comprising a controller configured to receive an indication regarding interference of propagating acoustic waves from the transducer assembly.

22. The transducer assembly of claim 5, wherein the first set of electrodes and the second set of electrodes are positioned on the same side of the ultrasound producing material.

23. The transducer assembly of claim 5, wherein the first set of electrodes and the second set of electrodes are connected to an electrical-mechanical switch or multiplexer.

24. An ultrasound treatment system comprising: the transducer assembly according to any of claims 1-23; and an applicator for applying ultrasound energy to a patient using the transducer assembly.

25. The system of claim 24, wherein: the applicator comprises a distal face configured to contact a skin surface of the patient; the ultrasound transducer assembly is positioned on the distal face of the applicator.

26. A method for treating skin of a subject in need thereof, the method comprising: placing an applicator in contact with or adjacent to a first region of interest (ROI) on the skin; and applying ultrasound energy to the first ROI using the applicator, wherein the applicator comprises a plurality of actuation regions on a surface of a ultrasound producing material; wherein the plurality of actuation regions comprises at least a first actuation region and a second actuation region; wherein the applicator comprises at least one non-actuation region on the surface of the ultrasound producing material separating the first actuation region from the second actuation region; wherein the first actuation region is operable to produce a first propagating acoustic wave in a direction perpendicular to a top surface of the first actuation region; wherein the second actuation region is operable to produce a second propagating acoustic wave in a direction perpendicular to a top surface of the second actuation region; wherein a main beam or lobe of the first propagating acoustic wave and a main beam or lobe of the second propagating acoustic wave do not overlap each other by more than 30% at a distance Z away from the surface of the ultrasound producing material in the direction of the first propagating acoustic wave and / or in the direction of the second propagating acoustic wave; and wherein the distance Z is a therapeutic distance of the ultrasound transducer assembly.

27. The method of claim 26, wherein the ultrasound energy has a frequency of 100 kHz to 20MHz.

28. The method of claim 26, wherein applying ultrasound energy to the first ROI causes thermal damage to a tissue layer beneath an epidermis of the skin.

29. The method of claim 28, wherein the thermal damage comprises a plurality of thermally damaged zones corresponding to the plurality of actuation regions of the applicator.

30. The method of claim 29, wherein the plurality of thermally damaged zones correspond in a 1 : 1 manner to the plurality of actuation regions of the applicator.

31. The method of claim 28, wherein applying ultrasound energy to the first ROI does not cause thermal damage or coagulation to the epidermis of the skin.

32. The method of claim 30, further comprising: optionally moving the applicator from contact with or adjacent to the first ROI to place the applicator in contact with or adjacent to a second ROI differing from the first ROI; and applying ultrasound energy to the second ROI using the applicator.

33. The method of claim 32, wherein applying ultrasound energy to the second ROI causes thermal damage to a tissue layer beneath an epidermis of the skin, differing from or in addition to thermal damage caused by applying ultrasound energy to the first ROI.

34. The method of claim 33, wherein the thermal damage caused by applying ultrasound energy to the second ROI comprises a plurality of thermally damaged zones corresponding to the plurality of actuation regions of the applicator.

35. The method of claim 34, wherein the plurality of thermally damaged zones caused by applying ultrasound energy to the second ROI correspond in a 1 : 1 manner to the plurality of actuation regions of the applicator.

36. The method of claim 33, wherein applying ultrasound energy to the first ROI does not cause thermal damage or coagulation to the epidermis of the skin.

37. The method of claim 32, wherein: the applicator is moved from contact with or adjacent to the first ROI before applying the ultrasound energy to the second ROI.

38. The method of claim 32, wherein: the applicator is not substantially moved from contact with or adjacent to the first ROI before applying the ultrasound energy to the second ROI.

39. The method of claim 38, further comprising: reconfiguring electrical-mechanical switches or multiplexers after applying the ultrasound energy to the first ROI and before applying the ultrasound energy to the second ROI, thereby targeting the second ROI instead of the first ROI without substantially moving the applicator.

40. A method of making a transducer assembly, the method comprising: providing a ultrasound producing material having a first surface and a second surface, wherein the second surface is on an opposite side of the ultrasound producing material from the first surface; defining a metallization pattern on the first surface of the ultrasound producing material; and metallizing the first surface of the ultrasound producing material with a conductive material according to the metallization pattern, wherein metallizing the first surface of the ultrasound producing layer forms a first plurality of strips of the conductive material along a first direction in a lateral plane of the ultrasound producing material according to the metallization pattern, and a second plurality of strips of the conductive material along a second direction in the lateral plane.41 . The method of claim 40, wherein the first plurality of strips and the second plurality of strips intersect to form one or more overlapping regions in the lateral plane.

42. The method of claim 41, wherein the one or more overlapping regions form or define one or more actuation regions.

43. The method of claim 41, wherein: a plurality of overlapping regions is formed; and the overlapping regions define an array of coherent actuation regions.

44. The method of claim 43, wherein the plurality of actuation regions defines a row-column pattern.

45. The method of claim 44, wherein a distance between adjacent actuation regions in the array is greater than 50 microns.

46. The method of claim 45, wherein the distance between adjacent actuation regions is at least 1 mm.

47. The method of claim 40, wherein the metallization pattern is formed from or defined by gold, nickel, chrome, copper, or an alloy, combination, or mixture thereof.

48. The method of claim 40, wherein the metallization pattern is formed from or defined by an electrically conductive film or tape.

49. The method of claim 40, wherein the metallization pattern is defined using photolithography .

50. The method of claim 40, wherein the metallization pattern is defined using a dicing saw.

51. The method of claim 40, wherein the metallization pattern is defined using a water saw.

52. The method of claim 40, wherein the metallization pattern is defined using a laser.

53. The method of claim 40, wherein the ultrasound producing material defines or is disposed on or formed by a single plate.

54. The method of claim 53, wherein the ultrasound producing plate is a polycrystalline ultrasound producing plate or a composite ultrasound producing plate.

55. The method of claim 53, wherein the ultrasound producing plate comprises or is formed from a CMUT, PMUT, polymer MUT, or membrane-based mechanically vibrating structure.

56. The method of claim 40, wherein the ultrasound producing material defines or is disposed on or formed by a plano-convex structure.

57. The method of claim 40, wherein the ultrasound producing material defines or is disposed on or formed by a plano-concave structure.

58. The method of claim 40, wherein the ultrasound producing material defines or is disposed on or formed by a convex-concave structure.

59. The method of claim 40, wherein the ultrasound producing material defines or is disposed on or formed by a cylinder.

60. The method of claim 40, further comprising attaching a matching layer to the first surface of the ultrasound producing material.

61. The method of claim 40, further comprising attaching a backing layer to the second surface of the ultrasound producing material.

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