A high bandwidth fiber optic ultrasonic transducer device

Abstract

The application belongs to the technical field of ultrasonic detection, and particularly relates to a high-bandwidth fibrous ultrasonic transducer device. The fibrous ultrasonic transducer device is composed of a flexible matching layer, a conductive path, a piezoelectric layer and a flexible backing layer. The piezoelectric layer comprises piezoelectric units and a flexible encapsulating material, the piezoelectric units are arranged at intervals, and the flexible encapsulating material is filled between the piezoelectric units, and the piezoelectric layer has a soft-hard block structure. The flexible matching layer and the flexible backing layer are both composed of a composite material prepared from resin and nanoparticles. The conductive path is a patterned circuit prepared by a metal film deposition process. The fibrous ultrasonic transducer device has high sensitivity and bandwidth, can emit ultrasonic waves under the excitation of an electric signal, and can be used as an ultrasonic emitter. The fibrous ultrasonic transducer device can also collect ultrasonic wave signals and convert the ultrasonic wave signals into electric signals, and can be used as an ultrasonic receiver. The fibrous ultrasonic transducer device has good flexibility, can withstand multiple bending and twisting, can be well attached to human skin, and can be used for wearable health monitoring.

Description

Technical Field

[0001] This invention belongs to the field of ultrasonic testing technology, and specifically relates to a high-bandwidth fiber-shaped ultrasonic transducer. Background Technology

[0002] Ultrasound technology possesses the ability to monitor deep tissues or organs. In recent years, wearable ultrasound devices have become a research hotspot in this field. Among them, ultrasound transducers, as core components, are developing towards miniaturization and flexibility to achieve long-term stable medical monitoring and treatment. On the other hand, in recent years, smart electronic fabrics have flourished, possessing unique advantages such as breathability, moisture wicking, and close contact with the human body surface, becoming an important development direction in the field of wearable electronics. Designing planar or bulk traditional ultrasound transducers into soft, fibrous ultrasound transducers and combining them with fabric weaving techniques can bring a more comfortable wearing experience and help achieve long-term stable monitoring.

[0003] An effective strategy for constructing ultrasound fabrics capable of long-term monitoring or disease diagnosis of deep tissues or organs is to construct fibrous ultrasound transducers with good flexibility. However, the size of the piezoelectric units will be limited, leading to a decrease in the signal-to-noise ratio of the ultrasound transducer, which is not conducive to the collection of effective signals.

[0004] To improve the sensitivity and bandwidth of fiber-reinforced ultrasonic transducers without sacrificing their flexibility, it is necessary to rationally design the structure of the fiber-reinforced ultrasonic transducers and screen their functional materials, thereby realizing a fiber-reinforced ultrasonic transducer with high sensitivity and high bandwidth.

[0005] This invention achieves a flexible, highly sensitive, and high-bandwidth fiber-shaped ultrasonic transducer by rationally designing the device structure and selecting appropriate functional materials. There are currently no related literature or patent reports. Summary of the Invention

[0006] The purpose of this invention is to provide a high-bandwidth fiber-shaped ultrasonic transducer with good flexibility and high sensitivity.

[0007] The high-bandwidth fiber-shaped ultrasonic transducer provided by this invention comprises a flexible matching layer, a conductive path, a piezoelectric layer, and a flexible backing layer stacked sequentially. The conductive path is located on both sides of the piezoelectric layer and is fabricated in the flexible matching layer and the flexible backing layer, respectively. The piezoelectric layer is the core of the fiber-shaped ultrasonic transducer. By applying a certain voltage to both ends of the piezoelectric layer through the conductive path connected to an external circuit, the piezoelectric layer can emit ultrasonic signals. Conversely, when the piezoelectric layer receives an external ultrasonic signal, it can output a specific electrical signal to the external circuit through the conductive path. During operation, the flexible matching layer directly contacts human skin. The flexible matching layer reduces ultrasonic energy loss caused by interface reflection between the piezoelectric layer and human skin, thereby improving the sensitivity and bandwidth of the ultrasonic transducer. The flexible backing layer is used to suppress the back vibration of the fiber-shaped ultrasonic transducer, further improving its bandwidth.

[0008] Furthermore:

[0009] The piezoelectric layer comprises piezoelectric units and a flexible encapsulation material, wherein the number of piezoelectric units is at least two; the length and width of each piezoelectric unit are between 200μm and 2000μm, and the height of each piezoelectric unit is between 200μm and 700μm. The piezoelectric units in the piezoelectric layer are arranged at intervals between 200μm and 2000μm, and the flexible encapsulation material fills the gaps between adjacent piezoelectric units.

[0010] The piezoelectric unit includes a piezoelectric material and an electrode; the piezoelectric material is one of PZT-5A piezoelectric ceramic, PZT-5H piezoelectric ceramic, PMN-PT piezoelectric single crystal, or type 1-3 composite piezoelectric material based on PZT-5A or PZT-5H; the electrode is one of copper, silver, gold, or other conductors.

[0011] The flexible encapsulation material is one of the polymer materials such as polydimethylsiloxane, polyurethane, epoxy resin, and styrene block copolymer.

[0012] The flexible matching layer has a thickness between 0.2 and 0.3 times the wavelength of the ultrasonic wave emitted by the piezoelectric unit; a density between 1.0 g / cm³ and 2.5 g / cm³; a sound velocity of ultrasonic waves in the flexible matching layer between 2000 m / s and 3000 m / s; an acoustic impedance between 2.6 MRayl and 7.5 MRayl; and a tensile modulus between 1 MPa and 20 MPa.

[0013] The flexible matching layer and flexible backing layer are prepared from raw materials such as epoxy resin, oxide nanoparticles, and coupling agents. The epoxy resin is obtained by reacting bisphenol A type epoxy monomers or oligomers with a curing agent, polyetheramine; the oxide nanoparticles are one or a mixture of several of nano-alumina, nano-titanium oxide, nano-silica, nano-zirconium oxide, and nano-cerium oxide; the coupling agent is one of γ-aminopropyltriethoxysilane, γ-glycidoxypropyltrimethoxysilane, γ-(methacryloyloxy)propyltrimethoxysilane, N-aminoethyl-γ-aminopropyltrimethoxysilane, and isopropyl dioleoyloxy(dioctylphosphoyloxy)titanate.

[0014] The conductive path is prepared by depositing a metal film on a flexible matching layer or flexible backing layer through a metal thin film deposition process. The deposited metal is one of gold, silver, copper, platinum, chromium, and aluminum.

[0015] The specific steps of the fabrication method of the aforementioned fibrous ultrasonic transducer are as follows:

[0016] (1) Using a mask, a thin metal film is deposited on the surface of the flexible matching layer and the flexible backing layer to form a patterned conductive path.

[0017] (2) Using conductive silver paste as an adhesive, apply conductive silver paste to the flexible matching layer with patterned conductive paths using a needle. Place the piezoelectric units at the application points using a template and wait for the conductive silver paste to cure, thus bonding the piezoelectric units to the flexible matching layer. Apply conductive silver paste to the flexible backing layer with patterned conductive paths using a needle and align it with the arranged piezoelectric units for bonding. Finally, bond the conductive paths to the external circuit.

[0018] (3) Add flexible encapsulation material between the flexible matching layer and the flexible backing layer to fill the gap, and wait for the flexible encapsulation material to cure to obtain multiple parallel ultrasonic transducers.

[0019] (4) Use diamond wire cutting to cut multiple parallel ultrasonic transducers to a specific width to obtain a fiber-shaped ultrasonic transducer.

[0020] The fiber-shaped ultrasound transducer designed in this invention emits ultrasound waves when excited by an external circuit with applied voltage. These waves enter human tissue and are reflected at different interfaces. By analyzing the time difference in the received reflected signals, the depth of the interfaces between different tissues can be determined. The fiber-shaped ultrasound transducer can identify the depth of the anterior and posterior walls of the carotid artery, thus determining the diameter of the carotid artery. When the blood vessel dilates and constricts, its diameter changes; based on this change, blood pressure changes can be calculated, thereby enabling health monitoring.

[0021] The fibrous ultrasound transducer in this invention also features high sensitivity and high bandwidth, excellent detection depth and resolution, and can monitor vascular blood pressure. When the size of the fibrous ultrasound transducer is further reduced and its integration is further improved, it can be further developed into ultrasound fabric, potentially enabling tissue or organ imaging for long-term monitoring of human tissue and organ conditions, which is of great significance for disease prevention and diagnosis. Attached Figure Description

[0022] Figure 1 This is a schematic diagram of the structure of the fibrous ultrasonic transducer of the present invention.

[0023] Figure 2 The results are pulse test results of the fibrous ultrasonic transducer in an embodiment of the present invention.

[0024] Figure 3 The test results of measuring the diameter of the carotid artery using a fibrous ultrasound transducer are presented in this invention. Detailed Implementation

[0025] (1) Preparation of flexible matching layer and flexible backing layer by spin coating: 0.35g of γ-aminopropyltriethoxysilane was added to 3.0g of ethanol and stirred for 10 minutes. Then, 1.2g of zirconia particles with a particle size of 30nm was added and stirred for 30 minutes. 1.8g of bisphenol A epoxy monomer was added and stirred for 2 hours. The mixture was then placed in an 80℃ oven for several hours to remove 2.3g of ethanol. After cooling, 0.6g of curing agent polyetheramine was added and stirred thoroughly. The mixture was dropped onto a silicon wafer and the spin coater was operated at 2000rpm for 30s. The spin-coated sample was cured at 60℃ and then repeatedly spin-coated to obtain the flexible matching layer. The preparation method of the flexible backing layer was the same, but the formulation was different.

[0026] (2) Deposition of conductive pathways: A mask for conductive pathways was prepared using an ultraviolet laser marking machine. The pattern of the conductive pathway mask was drawn using EZCAD software. A 50 μm thick tungsten plate was laser-marked to obtain the mask. A PCD 400 high-vacuum multifunctional three-target magnetron sputtering deposition system was used to deposit a metal thin film on the surface of the flexible matching layer and the flexible backing layer to form patterned conductive pathways until the metal film thickness reached more than 100 nm.

[0027] (3) Electrical connection of the fiber-shaped ultrasonic transducer: Using conductive silver paste as an adhesive, conductive silver paste is applied to the flexible matching layer with patterned conductive paths using a needle. Piezoelectric units are then placed at the applied locations using a template. The conductive silver paste is allowed to cure, bonding the piezoelectric units to the flexible matching layer (in this case, each fiber-shaped ultrasonic transducer contains two piezoelectric units, which are type 1-3 composite piezoelectric materials with copper electrodes). Conductive silver paste is then applied to the flexible matching layer with patterned conductive paths using a needle and aligned with the arranged piezoelectric units for bonding. Finally, the conductive paths are bonded to the external circuitry.

[0028] (4) Encapsulation of fibrous ultrasonic transducers: Flexible epoxy resin is dropped between the flexible matching layer and the flexible backing layer to fill the gaps, and the flexible epoxy resin is allowed to cure to obtain multiple parallel ultrasonic transducers.

[0029] (5) Cutting of fibrous ultrasonic transducers: Multiple parallel ultrasonic transducers were cut to a width of 1 mm using diamond wire cutting to obtain fibrous ultrasonic transducers. The final fibrous ultrasonic transducer was 5 cm long, 1 mm wide, and 700 μm high.

[0030] (6) Ultrasonic Pulse Test: The conductive path of the fiber ultrasonic transducer was connected to a pulse transmitter / receiver 5900PR. The pulse transmitter / receiver 5900PR transmitted the received signal to a computer via an oscilloscope. The fiber ultrasonic transducer was immersed in a water tank, and a copper plate was placed at a certain distance in front of it. The pulse transmitter / receiver applied an excitation voltage to the fiber ultrasonic transducer to make it emit ultrasonic waves. The echoes reflected from the copper plate were received by the fiber ultrasonic transducer, and the signals were transmitted to the computer. The computer software was used to analyze the sensitivity, bandwidth, and other parameters of the ultrasonic signal. The results are shown below. Figure 2 As shown, the fiber-optic ultrasound transducer has a large signal amplitude and a very short tail, indicating high sensitivity and bandwidth. Analysis shows that its -6dB bandwidth is 84.16%, which is close to the performance of transducers in current medical ultrasound probes.

[0031] (7) Carotid Artery Diameter Test: The conductive path of the fiber optic ultrasound transducer is connected to the pulse transmitter / receiver 5900PR. The pulse transmitter / receiver 5900PR transmits the received signal to a computer via an oscilloscope. The fiber optic ultrasound transducer is attached to the outer skin of the carotid artery. The transducer emits pulse signals, which are reflected at the tissue interface. The depth of the tissue can be determined based on the time it takes for the transducer to receive the reflected signal. Figure 3The principle and results of using a fiber optic ultrasound transducer to test the diameter of the carotid artery are as follows: Ultrasound signals are reflected at the anterior and posterior walls of the carotid artery. The fiber optic ultrasound transducer can accurately detect the reflected signals from the anterior and posterior walls of the carotid artery. Based on the time of signal reception, the diameter of the carotid artery can be calculated to be approximately 8 mm, which is consistent with clinical results.

Claims

1. A high-bandwidth fiber-optic ultrasonic transducer, characterized in that, The device is composed of a flexible matching layer, a conductive path, a piezoelectric layer, and a flexible backing layer stacked sequentially. The conductive path is located on both sides of the piezoelectric layer and is fabricated in the flexible matching layer and the flexible backing layer, respectively. A certain voltage is applied to both ends of the piezoelectric layer through the conductive path connected to an external circuit, causing the piezoelectric layer to emit ultrasonic signals. Conversely, when the piezoelectric layer receives an external ultrasonic signal, it outputs a specific electrical signal to the external circuit through the conductive path. The piezoelectric layer consists of piezoelectric units and a flexible encapsulation material. The flexible encapsulation material fills the gaps between adjacent piezoelectric units. The piezoelectric units are arranged using a template. Flexible encapsulation material is dropped between the flexible matching layer and the flexible backing layer to fill the gaps, resulting in multiple parallel-arranged ultrasonic transducers. When the fiber-shaped ultrasonic transducer is working, its flexible matching layer is in direct contact with human skin. The flexible matching layer is used to reduce the ultrasonic energy loss caused by interface reflection between the piezoelectric layer and human skin, thereby improving the sensitivity and bandwidth of the ultrasonic transducer. The flexible backing layer is used to suppress the back vibration of the fiber-shaped ultrasonic transducer, thereby improving the bandwidth of the ultrasonic transducer.

2. The high-bandwidth fiber-shaped ultrasonic transducer according to claim 1, characterized in that, The number of piezoelectric units is at least two; each piezoelectric unit has a length and width of 200 μm - 2000 μm and a thickness of 200 μm - 700 μm; The piezoelectric units are arranged at intervals of 200 μm to 2000 μm.

3. The high-bandwidth fiber-shaped ultrasonic transducer according to claim 2, characterized in that, The piezoelectric unit includes a piezoelectric material and an electrode; the piezoelectric material is selected from PZT-5A piezoelectric ceramic, PZT-5H piezoelectric ceramic, PMN-PT piezoelectric single crystal, and type 1-3 composite piezoelectric materials based on PZT-5A or PZT-5H; the electrode is selected from copper, silver, and gold.

4. The high-bandwidth fiber-shaped ultrasonic transducer according to claim 2, characterized in that, The flexible encapsulation material is selected from polymer materials such as polydimethylsiloxane, polyurethane, epoxy resin, and styrene block copolymer.

5. The high-bandwidth fiber-shaped ultrasonic transducer according to claim 2, characterized in that, The thickness of the flexible matching layer is 0.2-0.3 times the wavelength of the ultrasonic wave emitted by the piezoelectric unit; the density of the flexible matching layer is 1.0 g / cm³. 3 - 2.5g / cm 3 The ultrasonic velocity in the flexible matching layer is 2000 m / s - 3000 m / s; the acoustic impedance of the flexible matching layer is 2.6 MRayl - 7.5 MRayl; and the tensile modulus of the flexible matching layer is 1 MPa - 20 MPa.

6. The high-bandwidth fiber-shaped ultrasonic transducer according to claim 2, characterized in that, The flexible matching layer and flexible backing layer are prepared from epoxy resin, oxide nanoparticles, and coupling agent raw materials. The epoxy resin is obtained by reacting bisphenol A type epoxy monomers or oligomers with curing agent polyetheramine. The oxide nanoparticles are selected from nano alumina, nano titanium dioxide, nano silicon dioxide, nano zirconium oxide, and nano cerium oxide. The coupling agent is selected from γ-aminopropyltriethoxysilane, γ-glycidoxypropyltrimethoxysilane, γ-(methacryloyloxy)propyltrimethoxysilane, N-aminoethyl-γ-aminopropyltrimethoxysilane, and isopropyl dioleoyloxy(dioctylphosphoyloxy)titanate.

7. The high-bandwidth fiber-shaped ultrasonic transducer according to claim 2, characterized in that, The conductive path is prepared by depositing a metal film on a flexible matching layer or a flexible backing layer using a metal thin film deposition process. The deposited metal is one of gold, silver, copper, platinum, chromium, or aluminum.

8. A method for fabricating a high-bandwidth fiber-shaped ultrasonic transducer as described in any one of claims 1-7, characterized in that, The specific steps are as follows: (1) Using a mask, a metal thin film is deposited on the surface of the flexible matching layer and the flexible backing layer to form a patterned conductive path; (2) Using conductive silver paste as an adhesive, the conductive silver paste is dropped onto the flexible matching layer with patterned conductive paths using a needle. The piezoelectric unit is placed at the location where the conductive silver paste is dropped by arranging the template. The conductive silver paste is then cured to bond the piezoelectric unit to the flexible matching layer. Use a needle to drop conductive silver paste onto a flexible backing layer with patterned conductive pathways, and then align and bond it to the arranged piezoelectric units; finally, bond the conductive pathways to the external circuit. (3) Add flexible encapsulation material between the flexible matching layer and the flexible backing layer to fill the gap, wait for the flexible encapsulation material to cure, and obtain multiple parallel ultrasonic transducers. (4) Use diamond wire cutting to cut multiple parallel ultrasonic transducers to a specific width to obtain a fiber-shaped ultrasonic transducer.

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