Solid-liquid composites with tunable acoustic impedance for wearable ultrasound patches

Abstract

Wearable ultrasound patches may include a matching layer. The matching layer may include an acoustic impedance which is selected to interface between piezoelectric elements and skin tissue. The matching layer may include an elastomer and a colloidal suspension. The colloidal suspension may form microdroplets or a film within the elastomer. The colloidal suspension may include a liquid and particles.

Description

NUTECH202503602 PATENTSOLID-LIQUID COMPOSITES WITH TUNABLE ACOUSTIC IMPEDANCE FOR WEARABLE ULTRASOUND PATCHESCROSS-REFERENCE

[0001] The present application claims the benefit under 35 U.S.C. § 119 of U.S. Provisional application 63 / 751,672, filed on January 30, 2025, titled “SOLID-LIQUID COMPOSITES WITH TUNABLE ACOUSTIC IMPEDANCE FOR WEARABLE ULTRASOUND PATCHES,” which is incorporated herein by reference in the entirety.GOVERNMENT LICENSE RIGHTS

[0002] This invention was made with government support under Grant No.2050587 awarded by the U.S. National Science Foundation. The government has certain rights in the invention.TECHNICAL FIELD

[0003] The present disclosure generally relates to diagnosis using ultrasound waves, and more particularly to ultrasonic probe attachment by adhesive patches.BACKGROUND

[0004] Ultrasound is a safe, noninvasive diagnostic technique used to measure internal structures such as blood vessels and blood flow velocity in the human body. A mismatch of acoustic impedance at an interface between a piezoelectric transducer and a medium to be probed by the ultrasound may substantially reduce the amount of ultrasound energy being transmitted into the medium, and thus the intensity of the returned signal. The reduction in the intensity of the returned signal may cause low signal-to-noise.

[0005] Acoustic matching layers may improve the transfer of ultrasound energy from the transducer to the imaged medium. The matching layers work to minimize the reflection of an emitted wave by having an impedance equivalent to the geometric mean of the impedances of the ultrasound transducer and the skin. The matching layers may be rigid matching layers made of metal particle-polymer composites. Rigid composites have high impedances but lack flexibility and stretchability. These rigid matching layersNUTECH202503602 PATENTmay not be compatible with flexible and / or stretchable wearable ultrasound patches. Therefore, it would be advantageous to provide a device, system, and method that cures the shortcomings described above.SUMMARY

[0006] A matching layer for a wearable ultrasound patch is described, in accordance with one or more embodiments of the present disclosure. In some aspects, the matching layer may include an elastomer. In some aspects, the matching layer may include a colloidal suspension. In some aspects, the colloidal suspension is disposed within the elastomer. In some aspects, the colloidal suspension is a sol including a liquid and a plurality of particles. In some aspects, the elastomer is lyophobic with the liquid. In some aspects, the plurality of particles are insoluble in the liquid. In some aspects, the plurality of particles are denser than the elastomer and the liquid.

[0007] A wearable ultrasound patch is described, in accordance with one or more embodiments of the present disclosure. In some aspects, the wearable ultrasound patch may include a backing layer. In some aspects, the wearable ultrasound patch may include a transducer layer including an electrical circuit. In some aspects, the electrical circuit may include at least one piezoelectric element configured to generate an emitted ultrasound wave by transducing an input signal and configured to generate an output signal by transducing a received ultrasound wave. In some aspects, the wearable ultrasound patch may include the matching layer. In some aspects, the transducer layer is disposed between the backing layer and the matching layer.

[0008] An ultrasound system is described, in accordance with one or more embodiments of the present disclosure. In some aspects, the ultrasound system may include the wearable ultrasound patch. In some aspects, the ultrasound system may a pulser-receiver configured to transmit the input signal to the piezoelectric element and receive the output signal from the piezoelectric element.

[0009] It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and areNUTECH202503602 PATENTnot necessarily restrictive of the present disclosure. The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate subject matter of the disclosure. Together, the description and drawings serve to explain the principles of the disclosure.BRIEF DESCRIPTION OF THE DRAWINGS

[0010] The numerous advantages of the disclosure may be better understood by those skilled in the art by reference to the accompanying figures in which:

[0011] FIGS. 1A-1C depict a block diagram of an ultrasound system including one or more wearable ultrasound patches, in accordance with one or more embodiments of the present disclosure.

[0012] FIGS. 2A-2B depict perspective views of the wearable ultrasound patch including a matching layer, in accordance with one or more embodiments of the present disclosure.

[0013] FIG. 2C depicts a side view of the wearable ultrasound patch including the matching layer, in accordance with one or more embodiments of the present disclosure.

[0014] FIG. 3A depicts a perspective view of the matching layer with microdroplet colloidal suspensions, in accordance with one or more embodiments of the present disclosure.

[0015] FIG. 3B depicts a perspective view of the matching layer with a film colloidal suspension, in accordance with one or more embodiments of the present disclosure.

[0016] FIGS. 4A-4B depict graphs of experimental results of the matching layer, in accordance with one or more embodiments of the present disclosure.

[0017] FIG. 5 depicts a flow diagram of a method of manufacturing the matching layer with the microdroplet colloidal suspensions, in accordance with one or more embodiments of the present disclosure.NUTECH202503602 PATENT

[0018] FIG. 6 depicts a graph of a percent intensity transmitted as a function of matching layer acoustic impedance, in accordance with one or more embodiments of the present disclosure.

[0019] FIG. 7 depicts a side view of the wearable ultrasound patch including multiple of the matching layers, in accordance with one or more embodiments of the present disclosure.DETAILED DESCRIPTION OF THE INVENTION

[0020] The present disclosure has been particularly shown and described with respect to certain embodiments and specific features thereof. The embodiments set forth herein are taken to be illustrative rather than limiting. It should be readily apparent to those of ordinary skill in the art that various changes and modifications in form and detail may be made without departing from the spirit and scope of the disclosure. Reference will now be made in detail to the subject matter disclosed, which is illustrated in the accompanying drawings.

[0021] Embodiments of the present disclosure are directed to solid-liquid composites with tunable acoustic impedance for wearable ultrasound patches. The wearable ultrasound patches may include a matching layer. The matching layer may include an acoustic impedance which is selected to interface between piezoelectric elements and skin tissue. The matching layer may include an elastomer and a colloidal suspension. The colloidal suspension may form microdroplets or a film within the elastomer. The colloidal suspension may include a liquid and particles.

[0022] U.S. Pat. No. US4557718A, titled “Agent for the separation of dissolved and / or undissolved materials of different buoyancy densities or densities by means of solutions of true metatungstates”; U.S. Pat. No. US11213275B2, titled “Wearable ultrasound patch and application method of such a patch”; U.S. Pat. No. US11627938B2, titled “Imaging device with ultrasound transducer array”; U.S. Pat. Pub. No. US20020161301A1, titled “Matching layer having gradient in impedance for ultrasound transducers”; U.S. Pat. Publ. No. US20180360423A1, titled “Intravascular ultrasound device with impedanceNUTECH202503602 PATENTmatching structure”; U.S. Pat. Publ. No. US20210068785A1 , titled “Ultrasound transducer acoustic coupling”; U.S. Pat. Pub. No. US20220133269A1, titled “’’Integrated wearable ultrasonic phased arrays for monitoring; U.S. Pat. Pub. No. US20220175340A1 , titled “System and method for continuous non-invasive ultrasonic monitoring of blood vessels and central organs”; U.S. Pat. Publ. No. US20220363865A1 , titled “Lightweight liquid metal embedded elastomer composite”; U.S. Pat. Publ. No. US20230277159A1 , titled “Systems and methods for on-person wearable electronic devices”; U.S. Pat. Publ. No. US20240341726A1 , titled “Soft and stretchable composite material with tunable acoustic impedance”; are each incorporated herein by reference in the entirety.

[0023] FIGS. 1A-1C depicts an ultrasound system 100, in accordance with one or more embodiments of the present disclosure. The ultrasound system 100 may include wearable ultrasound patches 102 and / or a pulser-receiver 104.

[0024] The wearable ultrasound patches 102 may be wearable by a patient 101. The wearable ultrasound patches 102 may be adhered to the patient 101. The wearable ultrasound patches 102 may conform to one or more surfaces of the patient 101. For example, the wearable ultrasound patches 102 may conform to a temple and / or neck of the patient 101.

[0025] The wearable ultrasound patches 102 and the pulser-receiver 104 may be coupled by an interface. For example, the wearable ultrasound patches 102 and the pulser-receiver 104 by a wired interface and / or a wireless interface.

[0026] The wearable ultrasound patches 102 may be configured to emit the emitted ultrasound waves 108 and / or generate output signals 110. The wearable ultrasound patches 102 may be configured to receive input signals 106 from the pulser-receiver 104. The wearable ultrasound patches 102 may emit the emitted ultrasound waves 108 in response to receiving the input signals 106. The emitted ultrasound waves 108 may be sent through the skin to tissue of the patient 101 disposed below the skin. The emitted ultrasound waves 108 may reflect from the tissue of the patient 101 as the received ultrasound waves 112. The received ultrasound waves 112 may be theNUTECH202503602 PATENTbackpropagation of the emitted ultrasound waves 108. The wearable ultrasound patches 102 may be configured to receive the received ultrasound waves 112. The wearable ultrasound patches 102 may generate the output signals 110 in response to receiving the received ultrasound waves 112. The output signals 110 may include A-lines. The A-lines may be raw ultrasound data recorded during one or more pulses of the received ultrasound waves 112. The wearable ultrasound patches 102 may be configured to transmit the output signals 110 to the pulser-receiver 104.

[0027] The pulser-receiver 104 may excite the wearable ultrasound patches 102 with the input signals 106 and may receive the output signals 110 from the wearable ultrasound patches 102 in response to exciting the wearable ultrasound patches 102. The pulser-receiver 104 may excite the wearable ultrasound patches 102 with a select voltage, for a select duration, with a select pulse-repetition frequency, a select energy setting, a select damping setting, a select gain, and using one or more filters, and the like.

[0028] The pulser-receiver 104 may cause the wearable ultrasound patches 102 to measure data from the patient 101. The wearable ultrasound patches 102 may measure blood flow velocity, blood pressure, and the like. The data may be measured non-invasively. The wearable ultrasound patches 102 and / or the pulser-receiver 104 may be configured to perform digital signal processing on the output signals 110 to produce real-time blood flow velocity measurements. For example, the output signals 110 may include a Doppler spectrum which may show the increase and decrease in blood flow velocity in the brain as the heart pumps the blood. The pulser-receiver 104 may be configured to detect a change in the blood flow velocity of the patient 101 from the output signals 110. For example, the pulser-receiver 104 may detect the change in the blood flow velocity thereby indicating a symptom of early stroke. The strokes may include ischemic strokes, where blood clots or other particles block normal blood flow to the brain. The pulser-receiver 104 may continuously measure blood flow velocity in major cerebral arteries, such as the middle cerebral artery. In particular, the wearable ultrasound patches 102 may continuously measure blood flow velocity through the middle cerebral arteryNUTECH202503602 PATENT103 (MCA) that can be assessed from the temple of the patient 101. The pulserreceiver 104 may generate an alert in response to detecting the change in the blood flow velocity. For example, the pulser-receiver 104 may generate an alert for a medical professional of a potential abnormality in the brain before the abnormality becomes harmful or fatal.

[0029] The patient 101 may be a post-operation subarachnoid hemorrhage (SAH) patient that is at high-risk for developing a vasospasm, a potentially fatal condition in which there is persistent contraction of the blood vessels thereby decreasing blood flow. After traumatic brain injury or initial stroke, there is a time window in which a secondary stroke could possibly occur with devastating consequences for the patient. This secondary stroke could potentially be predicted and prevented by frequent periodic monitoring of the cerebral blood flow of the patient 101. The ultrasound system 100 may be configured to detect the vasospasm in the patient 101 using the wearable ultrasound patches 102 and / or the pulser-receiver 104. The vasospasm may refer to a constriction of the middle cerebral artery 103. For example, the patient 101 may be at risk for the vasospasm after an aneurysmal subarachnoid hemorrhage (aSAH). The ultrasound system 100 may detect the vasospasm by comparing a mean velocity of blood flow (VMCA) in a middle cerebral artery 103 of a patient 101 with a mean velocity of blood flow (VICA) in the internal carotid artery 105 of the patient 101. A Lindegaard Ratio may be a mean velocity of blood flow (VMCA) in the middle cerebral artery 103 over the mean velocity of blood flow (VICA) in the internal carotid artery 105. A Lindegaard ratio greater than 3 may indicate a vasospasm.

[0030] The wearable ultrasound patches 102 may include a wearable ultrasound patch 102a and a wearable ultrasound patch 102b which may be placed over the temple and / or neck of the patient 101 for measuring a mean velocity of blood flow (VMCA) in the middle cerebral artery 103 and a mean velocity of blood flow (VICA) in the internal carotid artery 105, respectively. The wearable ultrasound patch 102a may be wearable transcranial Doppler ultrasound (TCD) ultrasound patch. The emitted ultrasound waves 108 from the wearable ultrasound patch 102a and the wearable ultrasound patch 102b mayNUTECH202503602 PATENTreflect from the middle cerebral artery 103 and the internal carotid artery 105, respectively, and backpropagate as the received ultrasound waves 112. The output signals 110 may then be measurements of the mean velocity of blood flow (VMCA) in the middle cerebral artery 103 and the mean velocity of blood flow (VICA) in the internal carotid artery 105, respectively.

[0031] The pulser-receiver 104 may calculate the mean velocity of blood flow (VMCA) in the middle cerebral artery 103 and the mean velocity of blood flow (VICA) in the internal carotid artery 105 using the output signals 110 from the wearable ultrasound patches 102. The pulser-receiver 104 may calculate the mean velocity of blood flow (VMCA) in the middle cerebral artery 103 and the mean velocity of blood flow (VICA) in the internal carotid artery 105 by performing one or more steps.

[0032] For example, N-number of consecutive A-lines may be extracted from the output signals 110, where N is an integer. Each of the N-number of consecutive A-lines may be multiplied by a complex exponential of the center frequency of the emitted ultrasound waves 108 to shift the fast-Fourier transform of the A-line so that one of the spectral peaks is centered at 0 Hz. A finite impulse response (FIR) lowpass filter (order = 8) may be applied to each of the N-number of consecutive A-lines to remove the peak that is not at 0 Hz. The passband frequencies (fpass) for the FIR lowpass filter may be the center frequency (fo) divided by twice the sampling frequency (fs). The stopband frequencies (fstop) for the FIR lowpass filter may be the center frequency (fo) divided by the sampling frequency (fs). After lowpass filtering, a section of each of the N-number of consecutive A-lines may be summed to generate a complexvalued number. The complex-valued number may include N-number of the complex numbers. A fast-Fourier transform of the complex-valued number may generate a spectrum representing the motion of the blood in the middle cerebral artery 103 and / or the internal carotid artery 105. A FIR high pass filter, such as a wall filter, may be applied to remove low-frequency vibration of the middle cerebral artery 103 and / or the internal carotid artery 105. For example, the FIR high pass filter may include an order=15, a maximum stopband frequency 5 Hz, and a cutoff frequency of 10 Hz. A N-point Hanning window may then beNUTECH202503602 PATENTapplied. A frequency spectrum F(f) may be estimated by taking the N-point fast-Fourier transform of the Hanning-windowed data. A logarithmic power spectrum P(f) may be calculated from the frequency spectrum F(f) using the following equation:

[0033]

[0034] Where the * may denote the complex conjugate. The Doppler equation may convert the frequency to velocity using the following equation:&

[0035]

[0036] Where v is the velocity of the blood, c is the speed of sound in the medium through which the sound is travelling (c may be 1480 m / s for water at 20 degrees Celsius, may be 1540 m / s for soft tissue in the human body, or the like), 0 is the angle between the direction of sound propagation and the direction of flow, and fo is the center frequency. Thus, the mean velocity of blood flow (VMCA) in the middle cerebral artery 103 and the mean velocity of blood flow (VICA) in the internal carotid artery 105 may be calculated.

[0037] The pulser-receiver 104 may calculate the Lindegaard ratio from the mean velocity of blood flow (VMCA) in the middle cerebral artery 103 and the mean velocity of blood flow (VICA) in the internal carotid artery 105 to detect the vasospasm. Thus, the ultrasound system 100 may be used for detection of vasospasm. The pulser-receiver 104 may generate one or more alerts in response to detecting the vasospasm.

[0038] FIGS. 2A-2C illustrate the wearable ultrasound patches 102, in accordance with one or more embodiments of the present disclosure. The wearable ultrasound patches 102 may include one or more layers. For example, the wearable ultrasound patches 102 may include one or more of an adhesive layer 202, a matching layer 204, a transducer layer 206, and / or a backing layerNUTECH202503602 PATENT208. The matching layer 204 may be a solid-liquid composite with a tunable acoustic impedance for use in the wearable ultrasound patches 102.

[0039] The adhesive layer 202 may be a bottom-most layer of the wearable ultrasound patches 102. The adhesive layer 202 may be disposed below the matching layer 204. The adhesive layer 202 may be abutted to the matching layer 204. The adhesive layer 202 may be adhered to the matching layer 204. The adhesive layer 202 may be a flexible skin adhesive, such as a double-sided medical adhesive.

[0040] The matching layer 204 may be disposed between the transducer layer 206 and the adhesive layer 202. The matching layer 204 may be disposed below the transducer layer 206 and / or above the adhesive layer 202. The matching layer 204 may be abutted to the transducer layer 206 and / or the adhesive layer 202.

[0041] The transducer layer 206 may be disposed between the backing layer 208 and the matching layer 204. The transducer layer 206 may be disposed below the backing layer 208 and / or above the matching layer 204. The transducer layer 206 may be abutted to the backing layer 208 and / or the matching layer 204.

[0042] The backing layer 208 may be a top-most layer of the wearable ultrasound patches 102. The backing layer 208 may be disposed above the transducer layer 206. The backing layer 208 may be abutted to the transducer layer 206. The backing layer 208 may include any suitable backing layer. For example, the backing layer 208 may be a liquid metal backing layer.

[0043] The transducer layer 206 may include an electrical circuit 210. The electrical circuit 210 of the transducer layer 206 may be configured to generate the emitted ultrasound waves 108 and / or receive the received ultrasound waves 112. The electrical circuit 210 may include one or more components, such as feed lines 212, piezoelectric elements 214, and / or ground lines 216. The electrical circuit 210 may be flexible. The feed lines 212 and / or the ground lines 216 may be flexible thereby enabling flexure of the electrical circuit 210. The feed lines 212 and / or the ground lines 216 may include a flat flex-ribbonNUTECH202503602 PATENTcable, serpentine-patterned lines, or the like, by which the feed lines 212 and / or the ground lines 216 may be flexible. The piezoelectric elements 214 may or may not be flexible.

[0044] The feed lines 212 and / or the ground lines 216 may be electrically conductive. The feed lines 212 and / or the ground lines 216 may be made of an electrically conductive material, such as, but not limited to, copper. The piezoelectric elements 214 may be bonded and / or soldered to the feed lines 212 and / or the ground lines 216. The piezoelectric elements 214 may couple the feed lines 212 and the ground lines 216. The feed lines 212 may couple to individual of the piezoelectric elements 214. The feed lines 212 may be separate feed lines by which the piezoelectric elements 214 may be individually fed with current. The feed lines 212 may individually control the piezoelectric elements 214. The ground lines 216 may be a common ground. The feed lines 212 and / or the ground lines 216 may couple the piezoelectric elements 214 to the pulser-receiver 104. Thus, the piezoelectric elements 214 may receive the input signals 106 and / or transmit the output signals 110 to and from the pulserreceiver 104 via the feed lines 212 and / or the ground lines 216.

[0045] The piezoelectric elements 214 may be piezoelectric transducers, piezoelectric transducer elements, ultrasound elements, ultrasound transducers, piezoelectric ultrasound transducer elements, ultrasound generating elements, ultrasound receiving elements, or the like. For example, the piezoelectric elements 214 may be unfocused (flat) transducers. The piezoelectric elements 214 may be flat along a horizontal plane of the transducer layer 206. The piezoelectric elements 214 may include a uniform thickness, such that the piezoelectric elements 214 may be thinner than wide or long. The piezoelectric elements 214 may or may not include any significant curvature along a horizontal plane. The piezoelectric elements 214 may include a shape, such as, but not limited to, a circular shape. The piezoelectric elements 214 may include a select diameter. The diameter of the piezoelectric elements 214 may be between 8 and 25 millimeters. For example, the piezoelectric elements 214 may include a diameter of 12.7 millimeters (0.5 inches). By way of another example, the piezoelectric elements 214 mayNUTECH202503602 PATENTinclude a diameter of 18 millimeters. The piezoelectric elements 214 may include an acoustic impedance. Reducing the acoustic impedance of the piezoelectric elements 214 may be beneficial to provide better matching with the acoustic impedance of the matching layer 204. A fill factor of the piezoelectric elements 214 may be selected to provide a lowest possible acoustic impedance. The acoustic impedance of the piezoelectric elements 214 may be between 12 and 22 MRayl. For example, the acoustic impedance of the piezoelectric elements 214 may be 12 MRayl.

[0046] The piezoelectric elements 214 may emit the emitted ultrasound waves 108 and / or generate the output signals 110. The piezoelectric elements 214 may generate the emitted ultrasound waves 108 by transducing the input signals 106 to the emitted ultrasound waves 108 by vibration. The piezoelectric elements 214 may generate the output signals 110 by transducing the vibration induced by the received ultrasound waves 112 to the output signals 110. Thus, the piezoelectric elements 214 may be both ultrasound transmitters and ultrasound receivers.

[0047] In embodiments, the electrical circuit 210 may include one of the piezoelectric elements 214. For example, the wearable ultrasound patch 102b depicts the electrical circuit 210 with one of the piezoelectric elements 214, although this is not intended to be limiting.

[0048] In embodiments, the electrical circuit 210 may include at least two of the piezoelectric elements 214 arranged in an array. The array may be a planar array. The planar array may include at least two of the piezoelectric elements 214 which are co-planar. For example, the wearable ultrasound patch 102a depicts the electrical circuit 210 with nineteen of the piezoelectric elements 214, although this is not intended to be limiting. The piezoelectric elements 214 may form a lattice in the array. For example, the lattice may be a triangular lattice. The piezoelectric elements 214 may be independently addressable from the pulser-receiver 104 via the feed lines 212. For example, each of the piezoelectric elements 214 may be configured to receive a separate one of the input signals 106 from the feed lines 212 and generate a separate one of the emitted ultrasound waves 108. Independently addressing the piezoelectricNUTECH202503602 PATENTelements 214 may enabling acoustic beamforming of the emitted ultrasound waves 108.

[0049] The adhesive layer 202, the matching layer 204, the transducer layer 206, and / or the backing layer 208 may be conformal. For example, adhesive layer 202, the matching layer 204, the transducer layer 206, and / or the backing layer 208 may be configured to conform to a planar surface and / or a curved surface. The adhesive layer 202, the matching layer 204, the transducer layer 206, and / or the backing layer 208 may not be rigid. The adhesive layer 202, the matching layer 204, the transducer layer 206, and / or the backing layer 208 may be soft and / or stretchable. The adhesive layer 202, the matching layer 204, the transducer layer 206, and / or the backing layer 208 may also exhibit low hysteresis elasticity. The adhesive layer 202, the matching layer 204, the transducer layer 206, and / or the backing layer 208 may be highly stretchable. For example, the elastic modulus of the adhesive layer 202, the matching layer 204, the transducer layer 206, and / or the backing layer 208 may be between 10 kPa and 1 MPa. The matching layer 204 and / or the backing layer 208 may also exhibit low hysteresis elasticity. The matching layer 204 and / or the backing layer 208 may be highly stretchable. For example, the matching layer 204 and / or the backing layer 208 may include greater than 100% strain.

[0050] The matching layer 204, the transducer layer 206, and / or the backing layer 208 may include an elastomer. The elastomer may be a soft material which may be configured to conform to curved surfaces, such as a temple and / or a neck of the patient 101. The elastomer may include any suitable elastomer, such as a thermoset elastomer. The thermoset elastomers may include covalent bonds which crosslink polymer chains, providing thermal stability. The thermoset elastomers may be any suitable thermoset elastomers such as, but not limited to, silicone elastomers, polyurethanes, polyvinyl siloxane, butyl rubber, fluorosilicate, styrene butadiene rubber, acrylonitriles, fluoropolymers, copolymers thereof, blends thereof, or the like. The silicone elastomers may also referred to as a silicone matrix. The silicone elastomer may include any suitable silicone elastomer. For example, the silicone elastomer may include polydimethylsiloxane (PDMS), commercially availableNUTECH202503602 PATENTas SylgardTM184 silicon elastomer. Although the elastomers are described as being thermoset elastomers, this is not intended as a limitation of the present disclosure. For example, the elastomer material may a thermoplastic elastomer. However, the elastomer material being the thermoset elastomers may be advantageous for preventing melting of the elastomer.

[0051] The transducer layer 206 may embed at least a portion of the electrical circuit 210. Embedding may also be referred to as encapsulating, and / or encasing. The elastomer of the transducer layer 206 may be a dielectric. The elastomer may insulate electric current within the electrical circuit 210, thereby preventing electric current flow from the transducer layer 206 to the backing layer 208 and / or the matching layer 204. The elastomer may be adhered to the electrical circuit 210. Air bubbles may be removed from the elastomer before and / or during curing of the elastomer to promote the adhesion of the elastomer to the electrical circuit 210.

[0052] The emitted ultrasound waves 108 may pass from the piezoelectric elements 214 through the transducer layer 206, the matching layer 204 and / or the adhesive layer 202. The received ultrasound waves 112 may pass from the adhesive layer 202 through the matching layer 204 and through a portion of the transducer layer 206 to the piezoelectric elements 214.

[0053] The matching layer 204 may attenuate the emitted ultrasound waves 108 and / or the received ultrasound waves 112. The attenuation may decrease the amplitude of the emitted ultrasound waves 108 and / or the received ultrasound waves 112. The matching layer 204 may attenuate the emitted ultrasound waves 108 and / or the received ultrasound waves 112 based on an acoustic impedance (Zm) of the matching layer 204. The acoustic impedance (Zm) may be a resistance of matching layer 204 to the transmittance of sound waves (e.g., the emitted ultrasound waves 108 and / or the received ultrasound waves 112). Higher acoustic impedance (Zm) may cause more energy of the emitted ultrasound waves 108 and / or the received ultrasound waves 112 to be lost, resulting in a weaker signal. The matching layer 204 may improve the transmittance of the emitted ultrasound waves 108 and / or the received ultrasound waves 112 between the piezoelectric elements 214 and the skin.NUTECH202503602 PATENTThe piezoelectric elements 214 and the skin may have different acoustic impedances. The matching layer 204 may be configured to match the acoustic impedance of the piezoelectric elements 214 with the acoustic impedance of the skin of the patient 101. The optimal acoustic impedance of the matching layer 204 may be found using the geometric mean of the two surrounding materials. The acoustic impedance of the matching layer 204 may being the geometric mean to improve efficiency and resolution of the wearable ultrasound patches 102, enabling more accurate prognosis of health issues in the patient 101.

[0054] The acoustic impedance of the matching layer 204 may be any suitable value. For example, the acoustic impedance (Zm) of the matching layer 204 may be between 1.5 and 12 MRayls, may be between 2 and 8 MRayls, may be between 3 and 6 MRayls, or the like, though it could conceivably be higher or lower. For example, the piezoelectric elements 214 may include an acoustic impedance (Z1) of 12 MRayl and the skin may include an acoustic impedance (Z2) of 1.5 MRayl. For this example, the optimal acoustic impedance of the matching layer 204 (Zm) may be the geometric mean of the piezoelectric material (Z1 = 12 MRayl) and the imaged medium (Z2 = 1.5 MRayl), which is experimentally determined to be 4.24 MRayl. By way of another example, the piezoelectric elements 214 may include an acoustic impedance (Z1 ) of between 12 and 22 MRayl and the acoustic impedance of the matching layer 204 (Zm) may be selected to be between 4.24 - 5.74 MRayl, although an allowable range of values may be wider. These examples are not intended to be limiting and merely provide examples for selecting the acoustic impedance (Zm) based on acoustic impedance (Z1 ) of the piezoelectric elements 214.

[0055] The matching layer 204 may include a select thickness. For example, the thickness of the matching layer 204 may be about one-fourth of the wavelength of the ultrasound waves in the matching layer 204. The thickness of the matching layer 204 being one-fourth of the wavelength may minimize wave reflection. The wavelength of the ultrasound waves in the matching layer 204 may be based on the speed of sound in the matching layer 204 and / or the frequency of the ultrasound waves emitted by the piezoelectric elements 214.NUTECH202503602 PATENTFor example, the thickness of the matching layer 204 may be between 37.5 and 250 micrometers (corresponding to ultrasound frequencies of 5 - 1 MHz, respectively).

[0056] The backing layer 208 may be configured to attenuate one or more backwards-traveling portions of one or more ultrasound waves from the transducer layer 206. The received ultrasound waves 112 may pass through the transducer layer 206 up to the backing layer 208. The backing layer 208 may attenuate the received ultrasound waves 112, thereby preventing the propagation of the received ultrasound waves 112 through the backing layer 208. The backing layer 208 may provide a significant effect on shaping the received ultrasound waves 112. The backing layer 208 may include an acoustic impedance which is larger than the matching layer 204.

[0057] FIGS. 3A-3B depict the matching layer 204, in accordance with one or more embodiments of the present disclosure. In embodiments, the matching layer 204 may be an elastomer composite, as will be described further herein. The elastomer composite may enable the matching layer 204 to be conformal while providing a select acoustic impedance. The matching layer 204 may include an elastomer 302 and a colloidal suspension 304.

[0058] The elastomer 302 may be a base material of the matching layer 204. The elastomer 302 may be stretchable and flexible so that the matching layer 204 is applicable to the wearable ultrasound patches 102 by being able to fit the curvature of the skin. The elastomer 302 may include any suitable elastomer, such as a thermoset elastomer and / or a thermoplastic elastomer, as described above. For example, the elastomer 302 may include a two-part silicone elastomer such as ExSil™ 100 commercially available from Gelest™, Sylgard 184™, or the like. ExSil™ 100 may include a density of 1.12 g / cmA3 as an example.

[0059] The colloidal suspension 304 may be disposed within the elastomer 302. The colloidal suspension 304 may be a multi-phase inclusion disposed within the elastomer 302. The colloidal suspension 304 may include a liquid 306 and / or particles 308. The particles 308 may be solid particles which mayNUTECH202503602 PATENTbe held in the colloidal suspension 304 by the liquid 306. The colloidal suspension 304 may be a sol, in that the particles 308 are a solid dispersed throughout the liquid of the liquid 306. The liquid 306 and the particles 308 may be the continuous phase and the dispersed phase, respectively, of the colloidal suspension 304. The particles 308 may be dispersed (e.g., separated and distributed) throughout the liquid 306. The particles 308 may be monodisperse (e.g., uniform) or polydisperse (e.g., non-uniform) within the liquid 306. The colloidal suspension 304 may be stable, such that sedimentation of the particles 308 does not occur under the influence of gravity.

[0060] The colloidal suspension 304 may form one or more shapes within the elastomer 302. For example, the colloidal suspension 304 may form microdroplet colloidal suspensions 304a and / or a film colloidal suspension 304b within the elastomer 302. The microdroplet colloidal suspensions 304a and the film colloidal suspension 304b may each include the liquid 306 and the particles 308. For example, the microdroplet colloidal suspensions 304a may include microdroplets of the liquid 306 and the particles 308 held in colloidal suspension. By way of another example, the film colloidal suspension 304b may include a film of the liquid 306 and the particles 308 held in colloidal suspension.

[0061] The microdroplet colloidal suspensions 304a may be dispersed within the elastomer 302. The microdroplet colloidal suspensions 304a may be uniformly or non-uniform ly dispersed within the elastomer 302.

[0062] The microdroplet colloidal suspensions 304a may include any suitable aspect ratio. The aspect ratio may define whether the liquid metal microdroplets 114 are spherical or ellipsoidal. The aspect ratio may be defined relative to the median diameter of the microdroplet colloidal suspensions 304a. In this regard, the median diameter of the liquid metal microdroplets 114 may be the smallest principal diameter of the liquid metal microdroplets 114. The microdroplet colloidal suspensions 304a may be spherical or ellipsoidal. For example, the microdroplet colloidal suspensions 304a may be generally spherical with an aspect ratio between 1 and 1.1, and in some embodiments the aspect ratio may be approximately 1. By way of another example, the microdroplet colloidalNUTECH202503602 PATENTsuspensions 304a may be ellipsoidal with the aspect ratio between 1 and 30, between 1 and 10, between 1 and 2, or the like.

[0063] The film colloidal suspension 304b may be an inner volume of the matching layer 204 disposed within a cavity defined by the elastomer 302. The film colloidal suspension 304b may be enclosed on all sides by the elastomer 302. The film colloidal suspension 304b may be a layer which is not mixed with the elastomer 302. The film colloidal suspension 304b may interface with the elastomer 302 around the edges of the film colloidal suspension 304b. The film colloidal suspension 304b may be flat along a horizontal plane when the matching layer 204 is in a relaxed state. The film colloidal suspension 304b may bend with the matching layer 204.

[0064] The colloidal suspension 304 may include a colloidal dimension. The colloidal dimension may be the median size of the microdroplet colloidal suspensions 304a and / or the thickness of the film colloidal suspension 304b. The colloidal dimension (e.g., the median size of the microdroplet colloidal suspensions 304a and / or the thickness of the film colloidal suspension 304b) may be on the order of hundreds of nanometers, micrometers, tens of micrometers, or hundreds of micrometers. For example, the colloidal dimension may be on the order of hundreds of nanometers or micrometers. In embodiments, the colloidal dimension is on the order of micrometers.

[0065] The colloidal dimension (e.g., the median size of the microdroplet colloidal suspensions 304a and / or the thickness of the film colloidal suspension 304b) may be selected based on a wavelength of the ultrasound waves emitted by the piezoelectric elements 214 and / or the thickness of the matching layer 204. For example, the colloidal dimension may be less than the thickness of the matching layer 204 and / or may be within one order of magnitude of the wavelength of the ultrasound waves emitted by the piezoelectric elements 214.

[0066] The microdroplet colloidal suspensions 304a may be advantageous due to ease-of-manufacturing. The microdroplet colloidal suspensions 304a may also be more stable within the elastomer 302. For example, the film colloidal suspension 304b may change thickness due to motion which mayNUTECH202503602 PATENTchange the acoustic impedance of the matching layer 204. The film colloidal suspension 304b may be advantageous to reduce the number of scattering sites for the and / or the received ultrasound waves 112. For example, each of the microdroplet colloidal suspensions 304a may act as a scattering site which may introduce noise into the ultrasound waves. For instance, the interfaces between the microdroplet colloidal suspensions 304a and the elastomer 302 may cause scattering and / or decrease the strength of the signal.

[0067] The matching layer 204 may also include one or more additives. For example, the matching layer 204 may include surfactant. The surfactant may be an emulsifier. The surfactant may include, but are not limited to, a nonionic surface such as sorbitan monooleate, commercially available as Span™ 80 from Croda International PLC. The matching layer 204 may include a select weight percentage of the surfactant in the matching layer 204. For example, the weight percentage of the surfactant may be 0.5 percent. The surfactant may be beneficial to emulsify the colloidal suspension 304 with the elastomer 302 before the elastomer 302 is cured and enable forming the microdroplet colloidal suspensions 304a. The matching layer 204 may or may not include the surfactant where the film colloidal suspension 304b is formed.

[0068] The colloidal suspension 304 (e.g., the liquid 306 and / or the particles 308) may be immiscible with the elastomer 302. The elastomer 302 may be lyophobic with the liquid 306. For example, the elastomer 302 may be a hydrophobic elastomer and the liquid 306 of the colloidal suspension 304 may be an aqueous solution, such that the elastomer 302 may be repelled by water within the liquid 306 as the elastomer 302 is cured. The immiscibility may be beneficial to maintain the shape of the colloidal suspension 304 as the elastomer 302 is cured.

[0069] The colloidal suspension 304 may be denser than the elastomer 302. For example, the liquid 306 and / or particles 308 may be denser than the elastomer 302. The liquid 306 and the particles 308 may be high-density fluids and solids, respectively. In this regard, the specific gravity of the liquid 306 to the elastomer 302 and the specific gravity of the particles 308 to the elastomer 302 may each be greater than one. The addition of the colloidal suspensionNUTECH202503602 PATENT304 to the elastomer 302 may increase the density of the matching layer 204. The particles 308 may also be denser than the liquid 306. The addition of the particles 308 to the liquid 306 may also increase the density of the matching layer 204.

[0070] The liquid 306 may include any fluid with a sufficiently high-density. The liquid 306 may also be non-toxic. The density of the liquid 306 may be at least 0.9 g / cmA3. For example, the density of the liquid 306 may be at least 1.2 g / cmA3. For instance, the density of the liquid 306 may be at least 3 g / cmA3. Increasing the density of the liquid 306 may be beneficial for increasing the density of the colloidal suspension 304 and / or the acoustic impedance of the matching layer 204. The liquid 306 may be an aqueous solution such as an oil-in-water emulsion (O / W). For example, the liquid 306 may include, but is not limited to, a polytungstate solution, glycerol, or the like. The polytungstate solution and / or the glycerol may be the aqueous solution. The glycerol may be advantageous for ease-of-manufacturing but be less dense than the polytungstate solution. For example, the glycerol may have a density of 1.26 g / cmA3. It is contemplated that the liquid 306 (e.g., the glycerol) may or may not be denser than the elastomer 302, depending on the specific type of the elastomer 302 and the liquid 306. The polytungstate solution may be advantageous to provide a highly dense fluid with the density of at least 3 g / cmA3. In embodiments, the liquid 306 may be the polytungstate solution. The polytungstate solution may include, but is not limited to, a sodium polytungstate solution of sodium polytungstate (Na6[H2W12O40]) dissolved in water, commercially available from TC-Tungsten Compounds™ or Geoliquids, Inc™. The sodium polytungstate solution may also be referred to as a sodium metatungstate solution. The sodium polytungstate may be hydrophilic and / or water soluble, such that the sodium polytungstate may be attracted to and dissolved into the solution by the water. In embodiments, the sodium polytungstate solution may be a low-viscosity polytungstate (LVP) solution, commercially available as LVP-1 or LVP-3 from TC-Tungsten Compounds™.

[0071] The particles 308 may be insoluble in the liquid 306. For example, the particles 308 may be insoluble in water, glycerol, a polytungstate solution, orNUTECH202503602 PATENTthe like. Additionally, the particles 308 may not react to form an alloy with the liquid 306, where the particles 308 are metallic. The particles 308 may be lyophilic with the liquid 306. The particles 308 may be attracted into the liquid 306 and not easily precipitated out into the elastomer 302. The particles 308 being lyophilic with the liquid 306 may be beneficial to attract the particles 308 into the liquid 306 without the use of a shell around the particles 308 to trap the particles 308 within the liquid 306. For example, the particles 308 may be hydrophilic with the liquid 306. For instance, the particles 308 may be hygroscopic, such that the particles 308 may be attracted to but not dissolved by the water within the liquid 306. The liquid 306 may encase the particles 308, thereby preventing the particles 308 from interacting with the elastomer 302. Encasing the particles 308 in the liquid 306 may be beneficial to maintain the flexibility and / or stretchability of the elastomer 302 and / or reduce a stiffness caused by the addition of the particles 308.

[0072] The particles 308 may be made of a select material. The material of the particles 308 may be a d-block element, a p-block element, or a compound thereof. The d-block element, the p-block element, and / or the compound thereof may be selected with a density which is higher than the elastomer 302, which is able to form particles, which is insoluble in the liquid 306, and / or which is hygroscopic. The particles 308 may include any suitable density (e.g., true density). The true density is used as the liquid 306 surrounds the particles 308, filling any voids. For example, the density of the particles 308 may be at least 15 g / cmA3. For instance, the density of the particles 308 may be at least 19 g / cmA3. For example, the material may be a group 6 element, a group 10 element, a group 11 element, a group 14 element, a group 15 element, or compound thereof. For instance, the particles 308 may include, but are not limited to, tungsten (W), gold (Au), platinum (Pt), bismuth (Bi), lead (Pb), molybdenum (Mo), copper (Cu), carbon (C) (e.g., diamond particles), aluminum oxide (AI2O3), silver (Ag), tin (Sn), iron (Fe), zinc (Zn), nickel (Ni), cadmium (Cd), chromium (Cr), stainless steel, alloys thereof, compounds thereof, or the like. The tungsten, the diamond particles, aluminum oxide, silver, tin, iron, zinc, nickel, cadmium, chromium, stainless steel, alloys thereof, or compounds thereof may be hygroscopic such that the colloidal suspension 304 may beNUTECH202503602 PATENTformed without an adhesive shell around said particles. In embodiments, the particles 308 are tungsten particles. The tungsten particles may be advantageous to further increase the density of the colloidal suspension 304, as compared to the diamond particles and / or the aluminum oxide. The particles 308 may be made of any tungsten particles, such as, but not limited to, tungsten (W), tungsten carbide (WC), or alloys thereof. It is further contemplated that the particles 308 may include the adhesive shell. The adhesive shell may also be referred to as a capping agent, which may prevent agglomeration of the particles 308. However, the addition of the adhesive shell may complicate the formation of the colloidal suspension 304, by requiring preprocessing of the particles 308 with the adhesive shell.

[0073] The particles 308 may be nanoparticles and / or microparticles. The particles 308 may include a median size. The median size may be on the order of tens of nanometers, hundreds of nanometers, micrometers, and / or tens of micrometers. The median size of the particles 308 which are nanoparticles may be on the order of tens or hundreds of nanometers. For example, the median size of the particles 308 may be on the order of tens of nanometers. The median size of the particles 308 which are microparticles may be on the order of micrometers or tens of micrometers. In embodiments, the particles 308 are nanoparticles with a median size on the order of tens of nanometers or hundreds of nanometers. It is contemplated that the nanoparticles may be beneficial to prevent increasing the stiffness of the matching layer 204, as compared to the microparticles.

[0074] The median size of the particles 308 may be smaller than the colloidal dimension of the colloidal suspension 304. For example, the median size of the particles 308 may be at least one magnitude smaller than the median size of the microdroplet colloidal suspensions 304a and / or the thickness of the film colloidal suspension 304b. For instance, the particles 308 may be the nanoparticles with the median size on the order of tens or hundreds of nanometers and the median size of the microdroplet colloidal suspensions 304a and / or the thickness of the film colloidal suspension 304b may be on the order of micrometers or tens of micrometers.NUTECH202503602 PATENT

[0075] The colloidal suspension 304 may include a select volume loading (4>part) percentage of the particles 308 in the colloidal suspension 304. For example, the volume loading (<|)part) percentage of the particles 308 may be between one and fifty percent, may be between ten and twenty-five percent, or the like. The density of the colloidal suspension 304 may be proportional to the volume loading (<|)part) percentage of the particles 308. As the volume loading (4>part) percentage of the particles 308 increases, the rheology of the colloidal suspension 304 may change and / or the matching layer 204 may become stiffer.

[0076] The matching layer 204 may include a select volume loading (4>susp) percentage of the colloidal suspension 304 in the matching layer 204. For example, the volume loading (4>susp) percentage of the colloidal suspension 304 may be between one and seventy percent, may be between ten and fifty percent, may be between twenty and forty percent, or the like. For instance, the volume loading (4>susp) percentage may be about thirty percent. The volume loading (4>susp) percentage of the colloidal suspension 304 in the matching layer 204 may be up to a saturation limit of the elastomer 302. The saturation limit may refer to the point at which the stretchability of the elastomer 302 is limited due to the non-elastomer inclusions (e.g., the colloidal suspension 304). The colloidal suspension 304 may thereby increase the density of the matching layer 204 without significantly impacting the elastic modulus of the matching layer 204. Furthermore, the film colloidal suspension 304b may enable increasing the volume loading (4>susp) percentage of the colloidal suspension 304 above the saturation limit of the elastomer 302.

[0077] The matching layer 204 may include a select acoustic impedance (Zm). The acoustic impedance (Zm) of the matching layer 204 may be determined by the density (p) and the speed of sound (c) through the matching layer 204, as defined by the following formula:Z — p • c

[0078]

[0079] Wood’s model may be used to predict the speed of sound of through the matching layer 204 based on the compressibility (k) and density (p) of the matching layer 204, as defined by the following formula:NUTECH202503602 PATENT

[0080]

[0081] Thus, the acoustic impedance and / or speed of sound through the matching layer 204 may be based on the density (p) which is based on the volume loading (4>susp) percentage of the colloidal suspension 304 in the matching layer 204 and / or based on the volume loading (<|)part) percentage of the particles 308 in the colloidal suspension 304. The volume loading (4>susp) percentage of the colloidal suspension 304 in the matching layer 204 and / or the volume loading (c part) percentage of the particles 308 in the colloidal suspension 304 may be selected such that the acoustic impedance (Zm) of the matching layer 204 may be between the acoustic impedance of the human skin of the patient 101 and the piezoelectric elements 214 (e.g., the geometric mean between the human skin of the patient 101 and the piezoelectric elements 214), as described above. For example, the acoustic impedance (Zm) of the matching layer 204 may be between 1.5 and 12 MRayls, may be between 2 and 8 MRayls, or the like.

[0082] In embodiments, the liquid 306 and the particles 308 may form a W-LVP colloidal suspension in the elastomer 302, where the particles 308 and the liquid 306 are tungsten (W) and low-viscosity polytungstate (LVP), respectively. The combination of tungsten (W) and a low-viscosity polytungstate (LVP) produces a colloidal suspension with a favorable impedance. The combination of tungsten (W) and the low-viscosity polytungstate (LVP) produces a mixture with a favorable impedance for acoustic imaging for cerebral vasospasm. Examples compositions of the matching layer 204 include 30 volume loading (4>susp) percentage of the colloidal suspension 304 as W-LVP with 10, 15, 20, or 25 volume loading percentage (<|)part) of tungsten (W) remainder LVP, Span 80 0.5 weight percentage, with a remainder of ExSil™ 100.

[0083] FIGS. 4A-4B depict graphs 400 of experimental results of the matching layer 204, in accordance with one or more embodiments of the present disclosure. The graphs 400 were experimentally determined from six samples of the matching layer 204. The samples were prepared with the elastomer 302NUTECH202503602 PATENTbeing Exsil™ 100, with the liquid 306 being the low-viscosity polytungstate (LVP) solution, and with the particles 308 being the tungsten (W) being nanoparticles. The six samples included an Exsil™ only matching layer, an Exsil™-LVP matching layer with 50 percent volume loading (4>susp) of the LVP and without the particles 308 (e.g., Exsil-LVP 50% vol), and four Exsil™ and W-LVP matching layers each with 30 percent volume loading (4>susp) of the W-LVP colloid. The four Exsil™ and W-LVP matching layers included 10, 15, 20, and 25 percent volume loading (4>part), respectively, of the tungsten (W) with remainder LVP in the W-LVP colloid (e.g., Exsil-(W-LVP 10% vol) 30% vol); Exsil-(W-LVP 15% vol) 30% vol); Exsil-(W-LVP 20% vol) 30% vol); and Exsil-(W-LVP 25% vol) 30% vol)). The experimental setup for determining the results included placing the matching layer samples between an emitter and a receiver and measuring the acoustic impedance and attenuation. During testing, an ultrasound wave was sent through the matching layers. The speed of sound was measured from the time it takes for the wave to travel from the emitter through the matching layers to the receiver. The acoustic impedance and attenuation were then calculated from the speed of sound.

[0084] The graphs 400 include a graph 400a and a graph 400b. The graph 400a depicts the acoustic impedance (in MRayl) as a function of the volume loading of the six matching layers. The graph 400b depicts the attenuation (in dB / mm) as a function of the volume loading of the four Exsil™ and W-LVP matching layers.

[0085] The results indicate that the addition of the LVP to the Exsil™-LVP matching layer may increase the acoustic impedance as compared to the Exsil™ only matching layer. The impedance is increased due to the density of the LVP being higher than the density of the Exsil™. The results further indicate that the addition of the tungsten (W) to the W-LVP colloidal suspension in the Exsil™ and W-LVP matching layers may increase the acoustic impedance as compared to the Exsil ™-LVP matching layer, even where less of the LVP is used. The results further indicate that higher volume loading of the tungsten (W) in the W-LVP colloidal suspension may increase the acoustic impedance.NUTECH202503602 PATENTThe impedance is increased due to the density of the tungsten (W) being greater than the density of the LVP.

[0086] Acoustic impedances of the matching layers ranged from 1.92 MRayls to 2.25 MRayls with relatively low attenuations of 6.09 dB / mm to 6.7 dB / mm. The acoustic impedances increased from 1.92 to 2.25 MRayls as the volume loading of tungsten (W) in the W-LVP colloidal suspension was increased from 10% to 25%. This compares well with the Wood’s model, which predicts an acoustic impedance of 1.80 to 2.10 MRayls for the same volume loading. The average error between Wood's model and the experimental results was 7.26%. The attenuation for these volume loadings ranged from 6.09 dB / mm to 6.7 dB / mm. This is relatively low compared to other materials, such as eutectic gallium - indium in a silicone elastomer, which was shown to have an attenuation of approximately 33 dB / mm at a 50% volume loading. Thus, high impedances can be reached from low volume loadings with relatively low attenuation. It is contemplated that acoustic impedances higher than 2.25 MRayls may be achieved by increasing the volume loading (4>susp) of the W-LVP colloid in the elastomer 302 above 30% and / or increasing the volume loading (<|)part) of the tungsten in the W-LVP colloid above 25%.

[0087] FIG. 5 illustrates a flow diagram of a method 500, in accordance with one or more embodiments of the present disclosure. The method may also be referred to as a method of manufacturing the matching layer 204 with the microdroplet colloidal suspensions 304a. The embodiments and the enabling technologies described previously herein in the context of the matching layer 204 should be interpreted to extend to the method 500. It is further noted, however, that the method 500 is not limited to the architecture of the matching layer 204.

[0088] In a step 510, a liquid and particles may be mixed to form a colloidal suspension. For example, the liquid 306 and the particles 308 may be mixed to form the colloidal suspension 304.

[0089] In a step 520, an oligomer, the colloidal suspension, and / or a surfactant may be mixed to form an emulsion. For example, the oligomer, the colloidalNUTECH202503602 PATENTsuspension 304, and / or a surfactant may be mixed to form an emulsion. The emulsion may include microdroplet colloidal suspensions 304a distributed throughout the emulsion. The surfactant may promote mixing the hydrophobic elastomer and hydrophilic high-density fluid.

[0090] In a step 530, the oligomers of the emulsion may be cured to form an elastomer of the matching layer. For example, the oligomers of the emulsion may be cured to form the elastomer 302 of the matching layer 204. The microdroplet colloidal suspensions 304a may remain dispersed throughout the elastomer 302 during curing. The curing may include a duration of time, exposure to ultraviolet light, exposure to temperatures above ambient temperature as in thermoplastics, or evaporation of a solvent, either assisted or unassisted by an externally applied vacuum, as in solution processable elastomers.

[0091] It is further contemplated that each of the embodiments of the method described above may include any other step(s) of any other method(s) described herein. In addition, each of the embodiments of the method described above may be performed by any of the systems described herein.

[0092] FIG. 6 illustrates a graph 600, in accordance with one or more embodiments of the present disclosure. The graph 600 depicts the acoustic impedance (in MRayl) of the matching layer 204 as a function of the percent intensity transmitted (Ti%). The percent intensity transmitted (Ti%) is for a 35% random fiber piezo. The acoustic impedances are acceptable when allowing 90% or higher of sound intensity. In this example, the acoustic impedances were found to be between 2.5 and 7.3 MRayl for the 90 percent of the maximum percent intensity transmitted (Ti%) when the piezoelectric material's acoustic impedance is 12 MRayl, as depicted. A further example may include acoustic impedances were found to be between 3.3 and 10.1 MRayl for the 90 percent of the maximum percent intensity transmitted (Ti%) when the piezoelectric material's acoustic impedance is 22 MRayl.

[0093] FIG. 7 illustrates the wearable ultrasound patch 102 in accordance with one or more embodiments of the present disclosure. The wearable ultrasoundNUTECH202503602 PATENTpatch 102 may include multiple of the matching layers 204. Providing multiple of the matching layers 204 may be beneficial to improve the transmittance of the emitted ultrasound waves 108 and / or the received ultrasound waves 112 between the piezoelectric elements 214 and the skin.

[0094] The matching layers 204 may include a first matching layer 204a, a second matching layer 204b, and the like. The first matching layer 204a may be disposed between the second matching layer 204b and the transducer layer 206. The second matching layer 204b may be disposed between the first matching layer 204a and the adhesive layer 202. The acoustic impedance of the first matching layer 204a may be higher than acoustic impedance of the second matching layer 204b and lower than the acoustic impedance of the piezoelectric elements 214 (e.g., a geometric mean between said impedances). Similarly, the acoustic impedance of the second matching layer 204b may be higher than the acoustic impedance of the skin and lower than the acoustic impedance of the first matching layer 204a (e.g., a geometric mean between said impedances).

[0095] The acoustic impedances of the matching layers 204 may be controlled based on the volume loading (4>susp) percentage of the colloidal suspension 304 and / or the volume loading (<|)part) percentage of the particles 308 in the colloidal suspension 304 in the matching layers. For example, the volume loading (4>susp) percentage of the colloidal suspension 304 in the first matching layer 204a may be higher than the volume loading (4>susp) percentage of the colloidal suspension 304 in the second matching layer 204b. By way of another example, the volume loading (c part) percentage of the particles 308 in the colloidal suspension 304 in the first matching layer 204a may be higher than the volume loading (c part) percentage of the particles 308 in the colloidal suspension 304 in the second matching layer 204b.

[0096] It is further contemplated that the second matching layer 204b may or may not include the colloidal suspension 304 with the liquid 306 and / or the particles 308. For example, the second matching layer 204b may achieve the acoustic impedance which is higher than the skin and lower than the first matching layer 204a without the addition the liquid 306 and / or the particles 308.NUTECH202503602 PATENT

[0097] Referring generally again to the figures. The measurements of the mean velocity of blood flow (VMCA) in the middle cerebral artery 103 and the mean velocity of blood flow (VICA) in the internal carotid artery 105 may be measured at any interval. The interval may be selected to be frequent enough to detect the vasospasm in time for intervention, yet far enough apart and with low enough duty cycle to minimize exposure to acoustic radiation and risk of excessive tissue heating. The interval may include, but is not limited to, every 15 minutes.

[0098] The wearable ultrasound patches 102 may also be configured to measure other vital signs such as body temperature, respiration rate, and the like. For example, the wearable ultrasound patches 102 may include sensors, such as, but not limited to, temperature sensors, respiration sensors, and the like.

[0099] The emitted ultrasound waves 108 may include a near-field limit. The near-field limit may be to a distance from the piezoelectric elements 214 at which the emitted ultrasound waves 108 include an axial acoustic field with a maximum intensity. The near-field limit may be within a selected near-field limit. For example, the near-field limit of the emitted ultrasound waves 108 may be between 15 and 30 millimeters. The near-field limit of the emitted ultrasound waves 108 may be based on a wavelength of the emitted ultrasound waves 108. The emitted ultrasound waves 108 and / or the received ultrasound waves 112 may include a center frequency. The center frequency may be in the ultrasound range of 20 kHz to 18 MHz, or above. For example, the center frequency may between 1 MHz and 5 MHz. For instance, the center frequency may include 1 MHz, 2 MHz, 2.225 MHz, 2.25 MHz, 2.2375 MHz, 2.2625 MHz, 2.275, MHz, 2.75 MHz, or a value therebetween.

[0100] The pulser-receiver 104 may be configured to cause the wearable ultrasound patches 102 to beamform the emitted ultrasound waves 108. The wearable ultrasound patches 102 may be configured to perform the acoustic beamforming of the piezoelectric elements 214 by receiving the input signals 106 at separate phases. The emitted ultrasound waves 108 may then interfere (e.g., constructively and / or destructively interfere). The phase of the inputNUTECH202503602 PATENTsignals 106 may be controlled to control the interference of the emitted ultrasound waves 108 thereby beamforming the emitted ultrasound waves 108. The acoustic beamforming of the emitted ultrasound waves 108 may enable the wearable ultrasound patches 102 to locate the middle cerebral artery 103. For example, the wearable ultrasound patches 102 may locate the middle cerebral artery 103 while the wearable ultrasound patches 102 are adhered to the temple of the patient 101 without the need to manually reposition the wearable ultrasound patches 102 on the temple of the patient 101. The shape of the array of the piezoelectric elements 214 may be selected so that an area covered by the piezoelectric elements 214 may be used for monitoring the middle cerebral artery 103 by beamforming the emitted ultrasound waves 108.

[0101] Although the wearable ultrasound patches 102 are described as including the adhesive layer 202, this is not intended as a limitation of the present disclosure. It is contemplated that the matching layer 204 may be a bottom-most layer of the wearable ultrasound patches 102. The matching layer 204 may perform one or more functions of the adhesive layer 202. For example, the matching layer 204 may include one or more adhesive properties by which the wearable ultrasound patches 102 may adhere to one or more surfaces. In this regard, the matching layer 204 may be a combined matching and adhesive layer.

[0102] The pulser-receiver 104 may include a user interface. The user interface may include, but is not limited to, one or more desktops, laptops, tablets, and the like. The user interface may include a display used to display the output signals 110. The display of the user interface may include any display known in the art. For example, the display may include, but is not limited to, a liquid crystal display (LCD), an organic light-emitting diode (OLED) based display, or a CRT display.

[0103] One skilled in the art will recognize that the herein described components operations, devices, objects, and the discussion accompanying them are used as examples for the sake of conceptual clarity and that various configuration modifications are contemplated. Consequently, as used herein, the specific exemplars set forth and the accompanying discussion are intendedNUTECH202503602 PATENTto be representative of their more general classes. In general, use of any specific exemplar is intended to be representative of its class, and the noninclusion of specific components, operations, devices, and objects should not be taken as limiting.

[0104] As used herein, directional terms such as “top,” “bottom,” “over,” “under,” “upper,” “upward,” “lower,” “down,” and “downward” are intended to provide relative positions for purposes of description, and are not intended to designate an absolute frame of reference. Various modifications to the described embodiments will be apparent to those with skill in the art, and the general principles defined herein may be applied to other embodiments.

[0105] With respect to the use of substantially any plural and / or singular terms herein, those having skill in the art can translate from the plural to the singular and / or from the singular to the plural as is appropriate to the context and / or application. The various singular / plural permutations are not expressly set forth herein for sake of clarity.

[0106] The herein described subject matter sometimes illustrates different components contained within, or connected with, other components. It is to be understood that such depicted architectures are merely exemplary, and that in fact many other architectures can be implemented which achieve the same functionality. In a conceptual sense, any arrangement of components to achieve the same functionality is effectively "associated" such that the desired functionality is achieved. Hence, any two components herein combined to achieve a particular functionality can be seen as "associated with" each other such that the desired functionality is achieved, irrespective of architectures or intermedial components. Likewise, any two components so associated can also be viewed as being "connected," or "coupled," to each other to achieve the desired functionality, and any two components capable of being so associated can also be viewed as being "couplable," to each other to achieve the desired functionality. Specific examples of couplable include but are not limited to physically mixable and / or physically interacting components and / or wirelessly interactable and / or wirelessly interacting components and / or logically interacting and / or logically interactable components.NUTECH202503602 PATENT

[0107] Furthermore, it is to be understood that the invention is defined by the appended claims. It will be understood by those within the art that, in general, terms used herein, and especially in the appended claims (e.g., bodies of the appended claims) are generally intended as “open” terms (e.g., the term “including” should be interpreted as “including but not limited to,” the term “having” should be interpreted as “having at least,” the term “includes” should be interpreted as “includes but is not limited to,” and the like). It will be further understood by those within the art that if a specific number of an introduced claim recitation is intended, such an intent will be explicitly recited in the claim, and in the absence of such recitation no such intent is present. For example, as an aid to understanding, the following appended claims may contain usage of the introductory phrases "at least one" and "one or more" to introduce claim recitations. However, the use of such phrases should not be construed to imply that the introduction of a claim recitation by the indefinite articles "a" or "an" limits any particular claim containing such introduced claim recitation to inventions containing only one such recitation, even when the same claim includes the introductory phrases "one or more" or "at least one" and indefinite articles such as "a" or "an" (e.g., “a” and / or “an” should typically be interpreted to mean “at least one” or “one or more”); the same holds true for the use of definite articles used to introduce claim recitations. In addition, even if a specific number of an introduced claim recitation is explicitly recited, those skilled in the art will recognize that such recitation should typically be interpreted to mean at least the recited number (e.g., the bare recitation of "two recitations," without other modifiers, typically means at least two recitations, or two or more recitations). Furthermore, in those instances where a convention analogous to “at least one of A, B, and C, and the like” is used, in general such a construction is intended in the sense one having skill in the art would understand the convention (e.g., “ a system having at least one of A, B, and C” would include but not be limited to systems that have A alone, B alone, C alone, A and B together, A and C together, B and C together, and / or A, B, and C together, and the like). In those instances where a convention analogous to “at least one of A, B, or C, and the like” is used, in general such a construction is intended in the sense one having skill in the art would understand the convention (e.g., “ a system having at least one of A, B, or C” would include but not be limited toNUTECH202503602 PATENTsystems that have A alone, B alone, C alone, A and B together, A and C together, B and C together, and / or A, B, and C together, and the like). It will be further understood by those within the art that virtually any disjunctive word and / or phrase presenting two or more alternative terms, whether in the description, claims, or drawings, should be understood to contemplate the possibilities of including one of the terms, either of the terms, or both terms. For example, the phrase “A or B” will be understood to include the possibilities of “A” or “B” or “A and B.”

[0108] It is believed that the present disclosure and many of its attendant advantages will be understood by the foregoing description, and it will be apparent that various changes may be made in the form, construction and arrangement of the components without departing from the disclosed subject matter or without sacrificing all of its material advantages. The form described is merely explanatory, and it is the intention of the following claims to encompass and include such changes. Furthermore, it is to be understood that the invention is defined by the appended claims.

Claims

NUTECH202503602 PATENTCLAIMSWhat is claimed:

1. A matching layer for a wearable ultrasound patch, the matching layer comprising:an elastomer; anda colloidal suspension, wherein the colloidal suspension is disposed within the elastomer, wherein the colloidal suspension is a sol comprising a liquid and a plurality of particles, wherein the elastomer is lyophobic with the liquid, wherein the plurality of particles are insoluble in the liquid, wherein the plurality of particles are denser than the elastomer and the liquid.

2. The matching layer of claim 1 , wherein the liquid is an aqueous solution, wherein the elastomer is hydrophobic.

3. The matching layer of claim 2, wherein the liquid comprises a density of at least 0.9 g / cmA3.

4. The matching layer of claim 3, wherein the liquid comprises glycerol.

5. The matching layer of claim 3, wherein the liquid is denser than the elastomer.

6. The matching layer of claim 5, wherein the liquid comprises the density of at least 3 g / cmA3.

7. The matching layer of claim 5, wherein the liquid comprises a polytungstate solution.

8. The matching layer of claim 1 , wherein the plurality of particles comprise at least one of tungsten, gold, platinum, bismuth, lead, molybdenum, copper,NUTECH202503602 PATENTcarbon, aluminum oxide, silver, tin, iron, zinc, nickel, cadmium, chromium, stainless steel, an alloy thereof, or a compound thereof.

9. The matching layer of claim 1, wherein the plurality of particles are lyophilic with the liquid.

10. The matching layer of claim 9, wherein the liquid is an aqueous solution, wherein the plurality of particles are hygroscopic.

11. The matching layer of claim 10, wherein the plurality of particles comprise at least one of tungsten, carbon, aluminum oxide, silver, tin, iron, zinc, nickel, cadmium, chromium, stainless steel, an alloy thereof, or a compound thereof.

12. The matching layer of claim 11, wherein the plurality of particles comprise at least one of tungsten or tungsten carbide.

13. The matching layer of claim 1, wherein the plurality of particles are at least one of nanoparticles or microparticles.

14. The matching layer of claim 13, wherein the plurality of particles are nanoparticles, wherein a median size of the nanoparticles is smaller than a colloidal dimension of the colloidal suspension.

15. The matching layer of claim 1, wherein the colloidal suspension comprises a colloidal dimension, wherein the colloidal dimension is less than a thickness of the matching layer.

16. The matching layer of claim 1 , wherein a thickness of the matching layer is between 37.5 micrometers and 250 micrometers.

17. The matching layer of claim 1 , wherein the colloidal suspension forms a plurality of microdroplet colloidal suspensions dispersed within the elastomer.NUTECH202503602 PATENT18. The matching layer of claim 1 , wherein the colloidal suspension forms a film colloidal suspension disposed within the elastomer.

19. The matching layer of claim 1 , wherein the matching layer comprises an acoustic impedance of between 1.5 MRayls and 12 MRayls.

20. The matching layer of claim 1 , wherein a volume loading percentage (4>part) of the plurality of particles in the colloidal suspension is between one and fifty percent.

21. The matching layer of claim 1, wherein a volume loading percentage (4>susp) of the colloidal suspension in the matching layer is between one and seventy percent.NUTECH202503602 PATENT22. A wearable ultrasound patch comprising:a backing layer;a transducer layer comprising an electrical circuit, wherein the electrical circuit comprises at least one piezoelectric element configured to generate an emitted ultrasound wave by transducing an input signal and configured to generate an output signal by transducing a received ultrasound wave; and a matching layer, wherein the transducer layer is disposed between the backing layer and the matching layer, the matching layer comprising:an elastomer; anda colloidal suspension, wherein the colloidal suspension is disposed within the elastomer, wherein the colloidal suspension is a sol comprising a liquid and a plurality of particles, wherein the elastomer is lyophobic with the liquid, wherein the plurality of particles are insoluble in the liquid, wherein the plurality of particles are denser than the elastomer and the liquid.

23. The wearable ultrasound patch of claim 22, wherein the matching layer is a first matching layer, wherein the wearable ultrasound patch comprises a second matching layer, wherein the first matching layer is disposed between the transducer layer and the second matching layer, wherein an acoustic impedance of the first matching layer is higher than an acoustic impedance of the second matching layer.NUTECH202503602 PATENT24. An ultrasound system comprising:a wearable ultrasound patch comprising:a backing layer;a transducer layer comprising an electrical circuit, wherein the electrical circuit comprises at least one piezoelectric element configured to generate an emitted ultrasound wave by transducing an input signal and configured to generate an output signal by transducing a received ultrasound wave; anda matching layer, wherein the transducer layer is disposed between the backing layer and the matching layer, the matching layer comprising:an elastomer; anda colloidal suspension, wherein the colloidal suspension is disposed within the elastomer, wherein the colloidal suspension is a sol comprising a liquid and a plurality of particles, wherein the elastomer is lyophobic with the liquid, wherein the plurality of particles are insoluble in the liquid, wherein the plurality of particles are denser than the elastomer and the liquid; and a pulser-receiver configured to transmit the input signal to the electrical circuit and receive the output signal from the electrical circuit.

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