Ultrasonic transducer and its preparation method and application

Abstract

The present invention discloses an ultrasonic transducer, a preparation method thereof, and an application thereof. The ultrasonic transducer of the present invention comprises a flexible substrate, a thin film transistor, a piezoelectric tactile sensor, and a capacitive micromachined ultrasonic transducer arranged in sequence. The preparation method of the ultrasonic transducer of the present invention comprises the following steps: preparing a thin film transistor, a piezoelectric tactile sensor, and a capacitive micromachined ultrasonic transducer in sequence on a flexible substrate to obtain an ultrasonic transducer. The ultrasonic transducer of the present invention has both ultrasonic imaging and tactile sensing functions, and has the advantages of low ultrasonic driving voltage, high signal-to-noise ratio, high sensitivity, addressable arraying, flexibility and bendability, etc., and is suitable for large-scale promotion and application.

Description

Technical Field

[0001] The present invention relates to the technical field of ultrasonic detection, and in particular to an ultrasonic transducer and a preparation method and application thereof. Background Art

[0002] An ultrasonic transducer is a device used to realize the mutual conversion between electrical energy and acoustic energy. It can convert electrical signals into ultrasonic waves and vice versa. Probes made of ultrasonic transducer arrays are widely used in medical diagnosis and treatment, non-destructive testing, remote sensing and remote control, underwater communication and detection and other fields.

[0003] An ultrasonic endoscope is a new type of endoscope that combines ultrasonic technology (ultrasonic transducer) with an endoscope, which greatly increases the accuracy of detection. In the medical field, using a medical endoscope to detect damage and abnormalities in the patient's body is a common and efficient inspection method, which can help doctors develop the best treatment plan. However, traditional medical endoscopy examinations can cause pain to patients, and usually require the patient to be anesthetized for examination. The main reason for the pain is that after the endoscope enters the body, it is impossible to visually detect the pressure exerted by the endoscope on the patient's internal organs and tissues. In the industrial field, using industrial endoscopes to characterize the internal damage of instruments and equipment is a common inspection method, which can help engineers evaluate the condition of instruments and equipment. However, existing industrial endoscopes do not have the function of mechanical information feedback. During the detection process, it is easy to damage the instrument or endoscope because the amount of force applied is unknown.

[0004] Therefore, it is of great significance to develop an ultrasonic transducer that has both ultrasonic imaging and tactile sensing functions. Summary of the Invention

[0005] The purpose of the present invention is to provide an ultrasonic transducer and a preparation method and application thereof.

[0006] The technical solution adopted by the present invention is:

[0007] An ultrasonic transducer comprises a flexible substrate, a thin film transistor, a piezoelectric tactile sensor and a capacitive micro-machined ultrasonic transducer which are arranged in sequence.

[0008] Preferably, the flexible substrate is made of a flexible non-conductive polymer.

[0009] Further preferably, the flexible substrate is a polyimide (PI) film.

[0010] Preferably, the thin film transistor comprises a source electrode, a drain electrode, an active layer, a gate dielectric layer, a gate insulating layer and a gate electrode; the source electrode, the drain electrode and the active layer are arranged on the same surface of the flexible substrate and are in contact with the flexible substrate; the active layer partially covers the source electrode and the drain electrode; the gate dielectric layer covers the source electrode, the drain electrode and the active layer; the gate insulating layer and the gate electrode are arranged on the same surface of the gate dielectric layer and are in contact with the gate dielectric layer; and the gate electrode covers the gate insulating layer.

[0011] Preferably, the source electrode is one of a thin film Cu electrode, a thin film Au electrode, and a thin film ITO electrode.

[0012] Preferably, the drain electrode is a thin film Al electrode.

[0013] Preferably, the gate electrode is a thin film Al electrode. The gate electrode also serves as the lower electrode of the capacitive micromachined ultrasonic transducer.

[0014] Preferably, the thickness of the thin-film Cu electrode, the thin-film Au electrode, the thin-film ITO electrode and the thin-film Al electrode are all 100 nm to 200 nm.

[0015] Preferably, the thickness of the active layer is 20 nm to 50 nm.

[0016] Preferably, the active layer is one of a zinc oxide (ZnO) thin film, an indium gallium zinc oxide (IGZO) thin film, and a gallium oxide (Ga2O3) thin film.

[0017] Preferably, the gate dielectric layer has a thickness of 100 nm to 300 nm.

[0018] Preferably, the gate dielectric layer is one of a silicon dioxide (SiO2) film, an aluminum oxide (Al2O3) film, a silicon nitride (Si3N4) film, and an aluminum nitride (AlN) film.

[0019] Preferably, the gate insulating layer has a thickness of 500 nm to 1000 nm.

[0020] Preferably, the gate insulating layer is a polyimide (PI) film.

[0021] Preferably, the piezoelectric tactile sensor comprises a piezoelectric material layer and a tactile sensor electrode.

[0022] Preferably, the piezoelectric material layer has a thickness of 0.5 μm to 2 μm. The piezoelectric material layer also serves as the main support layer of the capacitive micromachined ultrasonic transducer.

[0023] Preferably, the piezoelectric material layer comprises a polymer matrix and ZnO nanomaterials.

[0024] Preferably, the mass ratio of the polymer matrix to the ZnO nanomaterial is 1:0.01 to 0.30.

[0025] Preferably, the polymer matrix is ​​at least one of polyvinylidene fluoride (PVDF), polydimethylsiloxane (PDMS), thermoplastic polyurethane (TPU), and polyurethane (PU).

[0026] Preferably, the ZnO nanomaterial is at least one of ZnO nanoparticles, ZnO nanorods, and ZnO nanobelts.

[0027] Preferably, the capacitive micromachined ultrasonic transducer comprises a main support layer, a micro cavity, a diaphragm and an ultrasonic transducer electrode; the micro cavity is arranged inside the main support layer; the diaphragm covers the main support layer and closes the micro cavity; and the ultrasonic transducer electrode is in contact with the diaphragm.

[0028] Preferably, the thickness of the transducer body is 0.5 μm to 2 μm.

[0029] Preferably, the thickness of the diaphragm is 0.3 μm to 1 μm. The diaphragm also serves as a coupling layer of the piezoelectric tactile sensor.

[0030] Preferably, the thickness of the ultrasonic transducer electrode is 100 nm to 200 nm.

[0031] Preferably, the main support layer in the capacitive micromachined ultrasonic transducer is made of piezoelectric material; the main support layer also serves as the piezoelectric material layer in the piezoelectric tactile sensor.

[0032] Preferably, the microcavity is cylindrical, has a depth of 0.4 μm to 1.8 μm, and a bottom diameter of 5 μm to 100 μm.

[0033] Preferably, the micro cavity is a vacuum cavity or an air cavity.

[0034] Preferably, the diaphragm is a polydimethylsiloxane (PDMS) film.

[0035] A method for preparing the ultrasonic transducer as described above comprises the following steps: sequentially preparing a thin film transistor, a piezoelectric tactile sensor and a capacitive micromachined ultrasonic transducer on a flexible substrate to obtain the ultrasonic transducer.

[0036] Preferably, a method for preparing the ultrasonic transducer as described above comprises the following steps:

[0037] 1) forming a source electrode and a drain electrode on a flexible substrate by metal deposition and etching;

[0038] 2) depositing an active layer and a gate dielectric layer in sequence through a metal deposition process;

[0039] 3) forming a gate insulating layer by coating process and imprinting / etching;

[0040] 4) forming a gate electrode on the gate insulating layer by metal deposition and etching;

[0041] 5) coating the piezoelectric material on the gate electrode and imprinting / etching a groove to form a main support layer (which is also the piezoelectric material layer);

[0042] 6) preparing the diaphragm through a coating process, and then bonding the diaphragm to the main support layer through a bonding process;

[0043] 7) A tactile sensor electrode and an ultrasonic transducer electrode are formed on the diaphragm through a metal deposition process and etching to obtain an ultrasonic transducer.

[0044] An ultrasonic detection device comprises the above-mentioned ultrasonic transducer.

[0045] Preferably, the ultrasonic detection equipment is an ultrasonic endoscope.

[0046] The working principle of the ultrasonic transducer of the present invention is as follows:

[0047] 1) When the ultrasonic transducer is used as an ultrasonic transmitter, a DC bias voltage and an alternating electric signal are simultaneously applied between an ultrasonic transducer electrode in the capacitive micromachined ultrasonic transducer and a gate electrode in the thin film transistor;

[0048] 2) When the ultrasonic transducer is used as an ultrasonic receiver, a current bias voltage is applied between the ultrasonic transducer electrode in the capacitive micromachined ultrasonic transducer and the gate electrode in the thin film transistor. The capacitive micromachined ultrasonic transducer converts the ultrasonic information into an electrical signal, couples it to the gate electrode, and then transmits the signal to the back-end processing circuit through the source / drain terminal after being preamplified by the thin film transistor.

[0049] 3) When the ultrasonic transducer touches the contact object, the piezoelectric tactile sensor converts the force into a charge signal and couples it to the gate electrode. The charge signal is then converted into a voltage signal via the thin film transistor and transmitted to the back-end processing circuit.

[0050] The beneficial effects of the present invention are: the ultrasonic transducer of the present invention has both ultrasonic imaging and tactile sensing functions, and has the advantages of low ultrasonic driving voltage, high signal-to-noise ratio, high sensitivity, addressable array, flexible and bendable, etc., and is suitable for large-scale promotion and application.

[0051] Specifically:

[0052] 1) The ultrasonic transducer of the present invention integrates a thin-film transistor (TFT), a tactile sensor, and a capacitive micromachined ultrasonic transducer (CMUT), combining ultrasonic imaging and tactile sensing functions. It has the advantages of low ultrasonic driving voltage, high signal-to-noise ratio, high sensitivity, addressable array, and flexible bendability. It has broad application prospects in wearable electronic devices, medical health testing, mechanical feedback of surgical robots, industrial flaw detection, and other fields.

[0053] 2) The ultrasonic transducer of the present invention adopts a flexible substrate, which has the advantages of flexibility and bendability, and can detect irregular objects, increasing the flexibility of detection;

[0054] 3) The ultrasonic transducer of the present invention uses a capacitive micro-machined ultrasonic transducer as an ultrasonic wave transmitting and receiving device, which improves the accuracy and bandwidth;

[0055] 4) The ultrasonic transducer of the present invention integrates thin-film transistors, which act as switches and signal amplifiers, reducing parasitic capacitance, improving the signal-to-noise ratio, and enabling addressable arraying;

[0056] 5) The main material of the capacitive micromachined ultrasonic transducer in the ultrasonic transducer of the present invention also serves as the piezoelectric sensitive layer of the tactile sensor, combining the dual functions of ultrasonic imaging and tactile sensing, increasing the integration level and enabling multi-function switching, thus broadening the application field;

[0057] 6) The ultrasonic transducer of the present invention uses a polydimethylsiloxane (PDMS) film as the diaphragm layer, which reduces the driving voltage and improves the bandwidth of the capacitive micromachined ultrasonic transducer;

[0058] 7) The ultrasonic transducer of the present invention uses a polyimide (PI) film to increase the thickness of the extended gate insulation layer, thereby reducing the extended gate capacitance and improving sensitivity;

[0059] 8) The ultrasonic transducer of the present invention uses PVDF / ZnO nanoparticles, nanorods or nanobelts as the piezoelectric sensitive layer of the tactile sensor, which has higher sensitivity and resolution than ordinary tactile sensors and pressure sensors. BRIEF DESCRIPTION OF THE DRAWINGS

[0060] Figure 1 Schematic diagram of the cross-section of the ultrasonic transducer of the present invention.

[0061] Figure 2 Schematic diagram of the three-dimensional structure of the ultrasonic transducer of the present invention.

[0062] Explanation of the accompanying symbols: 10, flexible substrate; 20, source electrode; 30, drain electrode; 40, active layer; 50, gate dielectric layer; 60, gate insulating layer; 70, gate electrode; 80, main support layer; 90, microcavity; 100, diaphragm; 110 ultrasonic transducer electrode; 120, tactile sensor electrode. DETAILED DESCRIPTION

[0063] The present invention will be further explained and illustrated below with reference to specific embodiments.

[0064] Example:

[0065] An ultrasonic transducer (sectional structural diagram as shown Figure 1 As shown, the three-dimensional structure diagram is as follows Figure 2 As shown), the composition includes a flexible substrate 10, a thin film transistor, a piezoelectric tactile sensor and a capacitive micromachined ultrasonic transducer arranged in sequence;

[0066] The thin film transistor comprises a source electrode 20, a drain electrode 30, an active layer 40, a gate dielectric layer 50, a gate insulating layer 60 and a gate electrode 70; the source electrode 20, the drain electrode 30 and the active layer 40 are arranged on the same surface of the flexible substrate 10 and are in contact with the flexible substrate 10; the active layer 40 partially covers the source electrode 20 and the drain electrode 30; the gate dielectric layer 50 covers the source electrode 20, the drain electrode 30 and the active layer 40; the gate insulating layer 60 and the gate electrode 70 are arranged on the same surface of the gate dielectric layer 50 and are in contact with the gate dielectric layer 50; the gate electrode 70 covers the gate insulating layer 60 (the gate electrode 60 also serves as the lower electrode of the capacitive micromachined ultrasonic transducer);

[0067] The piezoelectric tactile sensor comprises a piezoelectric material layer (the piezoelectric material layer also serves as the main support layer 80 of the capacitive micromachined ultrasonic transducer) and a tactile sensor electrode 120;

[0068] The capacitive micromachined ultrasonic transducer is composed of a main support layer 80, a micro cavity 90, a diaphragm 100 and an ultrasonic transducer electrode 110; the micro cavity 90 is arranged inside the main support layer 80; the diaphragm 100 covers the main support layer 80 and closes the micro cavity 90; the ultrasonic transducer electrode 110 is in contact with the diaphragm 100.

[0069] The preparation method of the ultrasonic transducer comprises the following steps:

[0070] 1) depositing an Al film, a thin-film Cu electrode, a thin-film Au electrode, or a thin-film ITO electrode with a thickness of 100 nm to 200 nm on a flexible substrate (flexible non-conductive polymer film, such as a PI film) through a metal deposition process, and then etching to form a source electrode and a drain electrode, respectively;

[0071] 2) depositing a ZnO film, an IGZO film, or a Ga2O3 film with a thickness of 20 nm to 50 nm on the flexible substrate on which the active electrode and the drain electrode are deposited by a metal deposition process to form an active layer;

[0072] 3) depositing a SiO2 film, Al2O3 film, Si3N4 film or AlN film with a thickness of 100 nm to 300 nm on the flexible substrate on which the active electrode, the drain electrode and the active layer are deposited by a metal deposition process to form a gate dielectric layer;

[0073] 4) coating the PI solution on the gate dielectric layer by spin coating, coating, printing, spraying, etc. to form a PI film with a thickness of 500 nm to 1000 nm, and then performing embossing or etching to form a groove in the middle portion until the gate dielectric layer is exposed to form a gate insulating layer;

[0074] 5) depositing an Al film with a thickness of 100 nm to 200 nm on the gate insulating layer and the exposed gate dielectric layer by a metal deposition process to form a gate electrode;

[0075] 6) coating a piezoelectric material (composed of a polymer matrix and a ZnO nanomaterial in a mass ratio of 1:0.01 to 0.30, wherein the polymer matrix is ​​at least one of PVDF, PDMS, TPU, and PU, and the ZnO nanomaterial is at least one of ZnO nanoparticles, ZnO nanorods, and ZnO nanobelts) on the gate electrode by spin coating, coating, printing, spraying, etc. to form a piezoelectric sensitive layer with a thickness of 0.5 μm to 2 μm, and then embossing or etching to form a groove, the groove being cylindrical, with a depth of 0.4 μm to 1.8 μm and a bottom diameter of 5 μm to 100 μm, to form a main support layer (which also serves as the piezoelectric material layer in the piezoelectric tactile sensor);

[0076] 7) Preparing a PDMS film with a thickness of 0.3 μm to 1 μm on a flat substrate such as a silicon wafer or a glass sheet by spin coating, coating, printing, spraying, etc., and then peeling it off from the substrate to obtain a diaphragm;

[0077] 8) The diaphragm is bonded to the main support layer by a bonding method to form a micro cavity, and then an Al thin film with a thickness of 100nm to 200nm is deposited on the diaphragm by a metal deposition process, and then etched to form a tactile sensor electrode and an ultrasonic transducer electrode, thereby obtaining an ultrasonic transducer.

[0078] The ultrasonic transducer of this embodiment integrates a thin-film transistor (TFT), a tactile sensor, and a capacitive micromachined ultrasonic transducer (CMUT), and has both ultrasonic imaging and tactile sensing functions. It has the advantages of low ultrasonic driving voltage, high signal-to-noise ratio, high sensitivity, addressable array, and flexible bendability. It has broad application prospects in wearable electronic devices, medical health testing, surgical robot mechanical feedback, industrial flaw detection, and other fields.

[0079] The above embodiments are preferred implementation modes of the present invention, but the implementation modes of the present invention are not limited to the above embodiments. Any other changes, modifications, substitutions, combinations, and simplifications that do not deviate from the spirit and principles of the present invention should be considered as equivalent replacement methods and are included in the scope of protection of the present invention.

Claims

1. An ultrasonic transducer, characterized in that: The composition includes a flexible substrate, a thin film transistor, a piezoelectric tactile sensor and a capacitive micromachined ultrasonic transducer arranged in sequence; the composition of the piezoelectric tactile sensor includes a piezoelectric material layer and a tactile sensor electrode; the composition of the capacitive micromachined ultrasonic transducer includes a main support layer, a micro cavity, a diaphragm and an ultrasonic transducer electrode; the tactile sensor electrode is in contact with the diaphragm; the micro cavity is arranged inside the main support layer; the diaphragm covers the main support layer and closes the micro cavity; the ultrasonic transducer electrode is in contact with the diaphragm; the main support layer in the capacitive micromachined ultrasonic transducer is made of piezoelectric material; the main support layer also serves as the piezoelectric material layer in the piezoelectric tactile sensor.

2. The ultrasonic transducer according to claim 1, wherein: The thin film transistor comprises a source electrode, a drain electrode, an active layer, a gate dielectric layer, a gate insulating layer and a gate electrode; the source electrode, the drain electrode and the active layer are arranged on the same surface of a flexible substrate and are in contact with the flexible substrate; the active layer partially covers the source electrode and the drain electrode; the gate dielectric layer covers the source electrode, the drain electrode and the active layer; the gate insulating layer and the gate electrode are arranged on the same surface of the gate dielectric layer and are in contact with the gate dielectric layer; and the gate electrode covers the gate insulating layer.

3. The ultrasonic transducer according to claim 1, wherein: The piezoelectric material layer comprises a polymer matrix and ZnO nanomaterials.

4. The ultrasonic transducer according to claim 3, characterized in that: The polymer matrix is ​​at least one of polyvinylidene fluoride, polydimethylsiloxane, thermoplastic polyurethane rubber, and polyurethane; and the ZnO nanomaterial is at least one of ZnO nanoparticles, ZnO nanorods, and ZnO nanobelts.

5. The ultrasonic transducer according to claim 1, wherein: The diaphragm is a polydimethylsiloxane film.

6. A method for preparing an ultrasonic transducer according to any one of claims 1 to 5, characterized in that: The method comprises the following steps: sequentially preparing a thin film transistor, a piezoelectric tactile sensor and a capacitive micro-machined ultrasonic transducer on a flexible substrate to obtain an ultrasonic transducer.

7. An ultrasonic testing device, characterized in that: The composition includes the ultrasonic transducer according to any one of claims 1 to 5.

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