Balloon catheter micro-cone array transducer based on barium titanate piezoelectric ceramics and preparation method

Abstract

The invention discloses a balloon catheter micro-cone array transducer based on barium titanate piezoelectric ceramics and a preparation method. The balloon catheter micro-cone array transducer comprises a balloon dilatation catheter and a transducer body installed on the outer surface of the balloon dilatation catheter. The transducer body comprises a flexible packaging layer and electrode layers installed on the upper surface and the lower surface of the flexible packaging layer, a plurality of conical barium titanate piezoelectric ceramic micro-cone array elements are arranged in the flexible packaging layer, and the upper ends and the lower ends of the barium titanate piezoelectric ceramic micro-cone array elements are communicated with the electrode layers on the upper surface and the lower surface respectively. According to the invention, the piezoelectric transducer with the micro-cone structure is adopted to carry out hardness testing, so that the signal sensitivity and the detection range are obviously improved, the elasticity modulus difference of vascular tissues can be distinguished in real time, and the method has repeatability and relatively high testing accuracy.

Description

TECHNICAL FIELD

[0001] The application relates to the technical field of medical detection equipment, and in particular to a balloon catheter micro-cone array transducer based on barium titanate piezoelectric ceramics and a preparation method. BACKGROUND

[0002] In clinical medicine, measuring blood vessel hardness is of great significance in medical treatment and health management. By measuring blood vessel hardness, doctors can identify problems such as atherosclerosis and hypertension at an early stage, and intervene early to reduce the incidence of cardiovascular diseases. At present, the following methods are used to measure blood vessel hardness: acoustic resonance, magnetic resonance elastography (MRE), ultrasonic elastography, CT scanning and MRI. These technologies can be used to evaluate the hardness and tissue structure of blood vessels, but they have problems such as large volume, complex operation, limited measurement scene, and may be affected by factors such as the skill level of the operator and the measurement environment, and have certain errors.

[0003] In recent years, the development of flexible piezoelectric composite materials has provided a new idea for intravascular sensors. By attaching a flexible sensor to a balloon catheter, the hardness of the blood vessel can be directly measured through interventional detection. However, the existing flexible sensors have low resolution and insufficient signal sensitivity. Therefore, there is an urgent need to develop a high-sensitivity sensor to realize direct characterization and accurate measurement of blood vessel hardness. SUMMARY

[0004] The application provides a balloon catheter micro-cone array transducer based on barium titanate piezoelectric ceramics and a preparation method.

[0005] Technical scheme: To solve the above problems, the application adopts a balloon catheter micro-cone array transducer based on barium titanate piezoelectric ceramics, which comprises a balloon dilatation catheter and a transducer main body mounted on the outer surface of the balloon dilatation catheter. The transducer main body comprises a flexible packaging layer, an electrode layer mounted on the upper and lower surfaces of the flexible packaging layer, and a plurality of barium titanate piezoelectric ceramic micro-cone array elements in the form of a pyramid are arranged in the flexible packaging layer, and the upper and lower ends of the barium titanate piezoelectric ceramic micro-cone array elements are respectively in conductive communication with the electrode layers on the upper and lower surfaces.

[0006] Further, the barium titanate piezoelectric ceramic micro-cone array element is a four-sided pyramid, and a plurality of barium titanate piezoelectric ceramic micro-cone array elements are uniformly arranged in an array.

[0007] Further, the size of the four edges of the bottom surface of the barium titanate piezoelectric ceramic micro-cone array element is 300 mu m x 300 mu m, the height of the barium titanate piezoelectric ceramic micro-cone array element is 400 mu m, and the distance between adjacent barium titanate piezoelectric ceramic micro-cone array elements is 200 mu m.

[0008] Furthermore, the electrode layer includes a copper foil and a PI film stacked together, with the copper foil closely attached to the surface of the flexible encapsulation layer.

[0009] Furthermore, the copper foil has a thickness of 50 μm, and the PI film has a thickness of 100 μm.

[0010] Furthermore, the flexible encapsulation layer is made of polydimethylsiloxane.

[0011] This invention also provides a method for fabricating the above-mentioned balloon catheter microcone array transducer, characterized in that it provides a barium titanate piezoelectric ceramic microcone array mold, comprising the following steps:

[0012] Step 1: Pour barium titanate ceramic slurry into the mold, vacuum stir the slurry and solidify it at room temperature. After demolding, obtain barium titanate piezoelectric ceramic microcone array green blank. Perform debinding, sintering and polarization treatment on the barium titanate piezoelectric ceramic microcone array green blank to obtain barium titanate piezoelectric ceramic microcone array element.

[0013] Step 2: Use flexible encapsulation material to encapsulate the barium titanate piezoelectric ceramic microcone array to form a flexible encapsulation layer;

[0014] Step 3: Install electrode layers on the upper and lower surfaces of the flexible encapsulation layer to obtain the transducer body;

[0015] Step 4: Install the transducer body onto the outer surface of the balloon dilation catheter.

[0016] Furthermore, the slurry is prepared by mixing 10g barium titanate powder, 7g ethanol, 3g n-butanol, 0.5g polyvinyl butyral, 0.5g dibutyl phthalate and 0.3g corn oil.

[0017] Furthermore, the temperature change during the sintering process is as follows: first, the temperature is increased to 600℃ at a rate of 0.5℃ / s and held for 4 hours, then the temperature is increased to 1250℃ at a rate of 5℃ / s and held for 4 hours.

[0018] Furthermore, the polarization specifically refers to polarizing at a voltage of 1.5kV for 1 hour.

[0019] Beneficial effects: Compared with the prior art, the significant advantage of this invention is that it uses a piezoelectric transducer with a microcone structure for hardness testing, which significantly improves signal sensitivity and detection range, can distinguish the elastic modulus differences of vascular tissues in real time, and has repeatability and high testing accuracy. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of the overall structure of the balloon catheter microcone array transducer of the present invention;

[0021] Figure 2 This is a schematic diagram of the main structure of the transducer of the present invention;

[0022] Figure 3 A simulation model of the piezoelectric properties of a cuboid piezoelectric ceramic;

[0023] Figure 4 The figure shows the simulation results of the piezoelectric properties of the cuboid piezoelectric ceramic.

[0024] Figure 5 A simulation model of the piezoelectric properties of a conical piezoelectric ceramic;

[0025] Figure 6 The figure shows the simulation results of the piezoelectric properties of the conical piezoelectric ceramic.

[0026] Figure 7 A simulation model of the piezoelectric properties of a pyramidal piezoelectric ceramic;

[0027] Figure 8 The figure shows the simulation results of the piezoelectric properties of the square pyramidal piezoelectric ceramic.

[0028] Figure 9 These are multiple test results of the two sizes of balloon catheter microcone array transducers of the present invention;

[0029] Figure 10 This is a schematic diagram of the fabrication process of the balloon catheter microcone array transducer of the present invention;

[0030] Figure 11 The heat treatment temperature curve of the barium titanate piezoelectric ceramic microcone structure of this invention;

[0031] Figure 12 These are comparative images of the morphology of the barium titanate piezoelectric ceramic microconical structure green body and its morphology after heat treatment, as shown in the figure.

[0032] Figure 13 This is the test hysteresis loop of the sintered barium titanate piezoelectric ceramic of the present invention;

[0033] Figure 14 This is a schematic diagram of the microstructure of the sintered barium titanate piezoelectric ceramic of the present invention. Detailed Implementation

[0034] Example 1

[0035] like Figure 1 and Figure 2As shown, this embodiment of a balloon catheter microcone array transducer based on barium titanate piezoelectric ceramics includes a balloon dilation catheter 1 and a transducer body 2 mounted on the outer surface of the balloon dilation catheter 1. The transducer body 2 includes a flexible encapsulation layer 21 and electrode layers mounted on the upper and lower surfaces of the flexible encapsulation layer 21. The flexible encapsulation layer 21 is made of polydimethylsiloxane (PDMS). The flexible encapsulation layer 21 contains a total of 12 barium titanate piezoelectric ceramic microcone array elements 22 arranged in a 3×4 array. Each barium titanate piezoelectric ceramic microcone array element 22 is a square pyramid with a base quadrilateral dimension of 300μm×300μm, a height of 400μm, and a spacing of 200μm between adjacent barium titanate piezoelectric ceramic microcone array elements 22.

[0036] In applications measuring blood vessel wall stiffness, the transducer must possess a certain degree of flexibility to ensure close contact with the vessel wall during measurement. Therefore, sufficient gaps need to be left between each array element to fill with the flexible encapsulation material PDMS. Simultaneously, under the same force, the voltage generated by a piezoelectric ceramic is directly proportional to its surface area; the larger the area, the greater the voltage generated. Combining these two points, in a two-dimensional planar array, using a pyramidal piezoelectric structure can both ensure sufficient gaps between array elements and maximize the surface area of ​​the piezoelectric elements.

[0037] The barium titanate piezoelectric ceramic microcone array 22 has a pointed upper end and a rectangular lower end. Both ends of the barium titanate piezoelectric ceramic microcone array 22 are connected to the electrode layers on the upper and lower surfaces, respectively, to ensure that the barium titanate piezoelectric ceramic microcone array 22 is electrically connected to the upper and lower surfaces for voltage signal acquisition. The electrode layer includes a copper foil 23 and a PI film 24 stacked together, wherein the copper foil 23 is 50 μm thick and the PI film 24 is 100 μm thick. The copper foil 23 is tightly attached to the surface of the flexible encapsulation layer 21.

[0038] Balloon dilation catheter 1 is a PTCA balloon, i.e., a balloon dilation catheter used for percutaneous endovascular coronary angioplasty. Balloon dilation catheter 1 is available in two sizes, with standard diameters of 2.25 mm and 4.00 mm at 6 atm.

[0039] The specific operating principle of this invention is as follows: The entire assembly is inserted into the blood vessel 3 via interventional surgery and delivered to the vascular lesion site 4. At the lesion site, pressure is applied to the blood vessel wall using a balloon dilation catheter 1. The pressure signal from the blood vessel wall is converted into an electrical signal by the piezoelectric effect of the transducer body 2, thereby directly characterizing the blood vessel wall stiffness. During detection, the tip structure of the barium titanate piezoelectric ceramic microcone array 22 can produce a large deformation under the same force, amplifying the deformation of the piezoelectric body in the inverse piezoelectric effect, and thus amplifying the generated voltage value. Therefore, in applications measuring blood vessel wall stiffness, when the force is relatively small, the barium titanate piezoelectric ceramic microcone array 22 can amplify the generated voltage signal, thereby improving the detection sensitivity.

[0040] To verify the effectiveness of the square pyramid piezoelectric array element, COMSOL was used to simulate piezoelectric array elements of three shapes: cuboid, cone, and square pyramid. The results are as follows. Figures 3 to 8 As shown, the same force was applied to piezoelectric structures of different shapes, and the displacement and voltage magnitude of each element were simulated and calculated. The displacement of the cuboid piezoelectric element was 2.7 × 10⁻⁶. -5 The voltage is 4.8 × 10 -5 The displacement generated by the conical piezoelectric array element is 8.2 × 10⁻⁶. -4 The voltage is 4.9 × 10 -5 The displacement generated by the square pyramidal piezoelectric array element is 1.6 × 10⁻⁶. -3 The voltage is 5.6 × 10 -5 Multiple sets of data comparisons show that the square pyramidal piezoelectric array structure has the best displacement and voltage amplification effect, which can amplify displacement by more than 80% and voltage by 30%, proving that this structure effectively improves the detection sensitivity.

[0041] This embodiment uses the following experiments to test the hardness measurement performance of the balloon catheter microcone array transducer.

[0042] (I) Customized Vascular Phantom Testing: Customized vascular phantoms made of resins with different hardness were used. The inner diameters of the phantoms used for testing were 2.25 mm and 4.00 mm, with elastic moduli of approximately 1.5 MPa and 20 MPa, respectively. A balloon catheter microcone array transducer was inserted into the vascular model. Periodic pressure was applied by inflating the balloon dilation catheter 1, and voltage signals were collected using an oscilloscope. The pressure inside the balloon dilation catheter 1 was slowly increased to 4 atm using a pressure injector to inflate the balloon. The pressure was then uniformly increased to 8 atm for 2 seconds and maintained for 4 seconds, followed by a uniform decrease to 4 atm for 4 seconds. This process was repeated four times, and the peak voltage value generated each time was recorded, thus completing one measurement. Multiple sets of tests were performed on normal and sclerotic blood vessels using balloon catheter microcone array transducers of two different sizes. The results are as follows: Figure 9As shown, the microcone array transducer can accurately identify blood vessel phantoms of different hardness in multiple sets of tests of both sizes, verifying the repeatability and accuracy of the transducer's blood vessel hardness measurement function, which meets the design expectations.

[0043] (II) Isolated Porcine Blood Vessel Testing: Treated isolated porcine blood vessels were used to replace the blood vessel phantoms in the above experiments. Immersion in formaldehyde solution increased the hardness of the isolated blood vessels to achieve the experimental objective. Measurement and analysis showed that the elastic modulus of the isolated porcine blood vessels before immersion was approximately 1.5 MPa, while the elastic modulus after immersion in formaldehyde solution was approximately 15-20 MPa. The measurement process was the same as the customized blood vessel phantom testing. The microcone array transducer could accurately identify the porcine blood vessels before and after immersion, meeting the design expectations.

[0044] Example 2

[0045] like Figure 10 As shown, this embodiment provides a method for fabricating the aforementioned balloon catheter microcone array transducer. The fabrication process involves providing a barium titanate piezoelectric ceramic microcone array element 22 mold. Specifically, the mold is fabricated by designing and 3D printing a rigid mold using photosensitive resin ST1400 Resin with a printing precision of 10 μm. Subsequently, a flexible mold is obtained by casting the mold using 3140 adhesive and allowing it to cure. The flexible mold ensures the integrity of the microcone structure during demolding while maintaining the same casting precision, facilitating the demolding of the green body.

[0046] The fabrication of the balloon catheter microcone array transducer includes the following steps:

[0047] Step 1: Prepare barium titanate ceramic slurry. Mill 10g barium titanate powder, 7g ethanol, 3g n-butanol, 0.5g polyvinyl butyral, 0.5g dibutyl phthalate, and 0.3g corn oil in a planetary ball mill for 6 hours, followed by vacuum stirring to remove bubbles. Pour the barium titanate ceramic slurry into a mold and vacuum stir to ensure it flows fully within the mold. Cur at room temperature for 24 hours, then demold to obtain a barium titanate piezoelectric ceramic microcone array green body. Perform debinding, sintering, and polarization treatments on the barium titanate piezoelectric ceramic microcone array green body to obtain barium titanate piezoelectric ceramic microcone array element 22. Figure 11 As shown, the sintering process follows the temperature curve illustrated: first, the temperature is increased to 600℃ at a rate of 0.5℃ / s and held for 4 hours, then increased to 1250℃ at a rate of 5℃ / s and held for 4 hours. Polarization specifically involves polarizing at 1.5kV for 1 hour to improve the piezoelectric properties of the barium titanate piezoelectric ceramic microcone array. After polarization, the piezoelectric constant (d33) of the barium titanate piezoelectric ceramic can reach 150-200 pC / N.

[0048] like Figure 12As shown, the left side displays an image of the green barium titanate piezoelectric ceramic microconical array element, while the right side displays an image of the barium titanate piezoelectric ceramic microconical array element after heat treatment. The electrical properties of the prepared barium titanate piezoelectric ceramic material were tested, and the results are as follows: Figure 13 As shown, the hysteresis loops of the material demonstrate that the sintered barium titanate ceramic possesses excellent ferroelectric properties. Specifically, the PE hysteresis loop exhibits a "butterfly-shaped" hysteresis loop, directly proving that the material is ferroelectric and possesses a domain structure; under an external electric field, the domains will flip and align. The SE hysteresis loop reflects the inverse piezoelectric effect (electric field → strain), indicating that the material possesses piezoelectric properties, with electromechanical properties coupled. The combination of these two factors proves that the sintered barium titanate ceramic material exhibits a piezoelectric effect and can be used as a piezoelectric transducer. Figure 14 As shown, the electron microscopy images of the microconical structure reveal the density of the material's microstructure and the integrity of the microconical structure after heat treatment.

[0049] Step 2: Use polydimethylsiloxane (PDMS) to encapsulate the barium titanate piezoelectric ceramic microcone array 22 to form a flexible encapsulation layer 21, so that the transducer as a whole is flexible and the relative positions between the microcone array elements remain fixed.

[0050] Step 3: Electrode layers are installed on the upper and lower surfaces of the flexible encapsulation layer 21 to obtain the transducer body 2. A 50μm thick copper foil and a 100μm thick PI film are connected using adhesive, and then cut using an LPKF ProtoLaser U3 laser cutter. Afterwards, conductive silver paste is used to connect wires, which are then cured by spin-coating a 5μm thick layer of PDMS and connected to the flexible encapsulation layer 21 to ensure the microcone array elements are conductive at both ends for voltage signal acquisition.

[0051] Step 4: The transducer body 2 is mounted on the outer surface of the balloon dilation catheter 1 by spin coating with PDMS with a thickness of 5μm, thus obtaining the balloon catheter microcone array transducer.

Claims

1. A balloon catheter microcone array transducer based on barium titanate piezoelectric ceramic, characterized in that, The device includes a balloon dilation catheter (1) and a transducer body (2) mounted on the outer surface of the balloon dilation catheter (1). The transducer body (2) includes a flexible encapsulation layer (21) and an electrode layer mounted on the upper and lower surfaces of the flexible encapsulation layer (21). The flexible encapsulation layer (21) contains a plurality of cone-shaped barium titanate piezoelectric ceramic microcone array elements (22), and the upper and lower ends of the barium titanate piezoelectric ceramic microcone array elements (22) are respectively connected to the electrode layers on the upper and lower surfaces.

2. The balloon catheter microcone array transducer as described in claim 1, characterized in that, The barium titanate piezoelectric ceramic microcone array (22) is a quadrangular pyramid, and multiple barium titanate piezoelectric ceramic microcone array elements (22) are arranged in an array uniformly.

3. The balloon catheter microcone array transducer as described in claim 2, characterized in that, The barium titanate piezoelectric ceramic microcone array element (22) has a bottom quadrilateral size of 300μm×300μm, a height of 400μm, and a spacing of 200μm between adjacent barium titanate piezoelectric ceramic microcone array elements (22).

4. The balloon catheter microcone array transducer as described in claim 1, characterized in that, The electrode layer includes a copper foil (23) and a PI film (24) stacked together, with the copper foil (23) closely attached to the surface of the flexible encapsulation layer (21).

5. The balloon catheter microcone array transducer as described in claim 4, characterized in that, The copper foil (23) has a thickness of 50 μm, and the PI film (24) has a thickness of 100 μm.

6. The balloon catheter microcone array transducer as described in claim 1, characterized in that, The flexible encapsulation layer (21) is made of polydimethylsiloxane.

7. A method for fabricating a balloon catheter microcone array transducer according to any one of claims 1-6, characterized in that, Providing a mold for a barium titanate piezoelectric ceramic microcone array (22) includes the following steps: Step 1: Pour barium titanate ceramic slurry into the mold, vacuum stir and solidify the slurry at room temperature, and obtain barium titanate piezoelectric ceramic microcone array green blank after demolding. Degumming, sintering and polarization treatment of barium titanate piezoelectric ceramic microcone array green blank are performed to obtain barium titanate piezoelectric ceramic microcone array element (22). Step 2: Use flexible encapsulation material to encapsulate the barium titanate piezoelectric ceramic microcone array (22) to form a flexible encapsulation layer (21); Step 3: Install electrode layers on the upper and lower surfaces of the flexible encapsulation layer (21) to obtain the transducer body (2); Step 4: Install the transducer body (2) onto the outer surface of the balloon dilation catheter (1).

8. The preparation method according to claim 7, characterized in that, The slurry is made by mixing 10g barium titanate powder, 7g ethanol, 3g n-butanol, 0.5g polyvinyl butyral, 0.5g dibutyl phthalate and 0.3g corn oil.

9. The preparation method according to claim 7, characterized in that, The temperature change during the sintering process is as follows: first, the temperature is increased to 600℃ at a rate of 0.5℃ / s and held for 4 hours, then the temperature is increased to 1250℃ at a rate of 5℃ / s and held for 4 hours.

10. The preparation method according to claim 7, characterized in that, The polarization specifically refers to polarizing at a voltage of 1.5kV for 1 hour.

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