High-ductility film piezoelectric sensor for pulse detection

Abstract

The invention discloses a high-ductility film piezoelectric sensor for pulse detection and a preparation method thereof, and belongs to the technical field of flexible electronic sensing, and the preparation method comprises the following steps: performing surface modification on lead zirconate titanate, introducing shape memory polyurethane to form a composite film, and finally preparing the film piezoelectric sensor. According to the prepared thin film piezoelectric sensor, the key contradiction between flexibility and high-performance cooperation of a traditional piezoelectric sensor is solved, the inorganic / organic phase interface bonding force is remarkably improved, cooperative improvement of low Young modulus and high ductility is achieved, the Young modulus is 52 MPa, the ductility is 177.3%, and the breakthrough of the flexible piezoelectric sensor in ultrahigh ductility is achieved.

Description

Technical Field

[0001] The present invention relates to the field of flexible electronic sensing technology, and particularly to a highly extensible thin-film piezoelectric sensor, which is particularly suitable for wearable human pulse monitoring devices. Background Art

[0002] In recent years, with the popularization of smart wearables and medical health monitoring, the application fields of micro-electromechanical devices such as microsensors, microelectronic devices, and portable electronic devices have been continuously expanding, and they have been widely used in many aspects such as embedded systems and human health detection systems, greatly promoting the detection and evaluation of various health states.

[0003] Nowadays, a large number of sensors for detecting pulse have emerged to help people better understand the physical condition of users. At present, medical devices for measuring pulse mainly adopt optoelectronic sensors, piezoelectric sensors, and capacitive sensors. Optoelectronic sensors are traditional rigid sensors. Due to their high Young's modulus (usually exceeding 60 GPa), it is difficult to adapt to the dynamic deformation of the skin or organs. Low Young's modulus materials can achieve non-invasive fitting and improve the detection accuracy of physiological signals (such as pulse and respiration). As a kind of dynamic strain sensor, flexible piezoelectric thin-film sensors have been widely used in the medical device field due to their light weight, softness, and passive working characteristics.

[0004] Flexible piezoelectric sensors have attracted much attention in the field of wearable monitoring, but the existing technologies still have problems such as mismatch of Young's modulus with the skin, insufficient ductility, and potential biosafety hazards. Therefore, there is an urgent need to develop a piezoelectric sensor that solves the technical contradictions of the above flexible piezoelectric sensors to provide a better solution for wearable medical monitoring. Summary of the Invention

[0005] The present invention aims at the problems of high Young's modulus mismatch with the skin and insufficient ductility existing in the existing flexible piezoelectric sensors, and provides a piezoelectric sensor for detecting pulse with a lower Young's modulus and better elongation rate, as well as a preparation method thereof.

[0006] To solve the above technical problems, the present invention adopts the following technical solutions:

[0007] The first object of the present invention is to provide a preparation method of a highly extensible thin-film piezoelectric sensor for pulse monitoring, which specifically includes the following steps:

[0008] Step (1), surface modification of lead zirconate titanate (PZT) particles: ultrasonic cleaning of PZT particles with a certain particle size in absolute ethanol, then adding them to a mixed solution of acetone and silane coupling agent, ultrasonic dispersing and then uniformly stirring, and drying for standby.

[0009] Step (2): Mix the modified PZT and shape memory polyurethane (SMPT) in proportion and disperse them evenly by ultrasonic treatment: Ultrasonically disperse the modified PZT particles in tetrahydrofuran (THF), add the SMPU pellets according to the proportion, stir, and let stand for 24 h.

[0010] Step (3): Preparation of the PZT / SMPT composite film: Uniformly coat the mixture prepared in step (2) on a glass plate, remove it after forming a film. Finally, hot press the PZT / SMPU film using a flat vulcanizer to complete the preparation of the film.

[0011] Step (4): Preparation of the electrode layer: Fabricate square electrodes on both the front and back sides of the PZT / SMPU film using a magnetron sputtering instrument.

[0012] Step (5): Preparation of the piezoelectric sensor: Apply an electric field to the film prepared in step (4) using a withstand voltage tester for polarization operation, and finally encapsulate it with silicone rubber to complete the preparation of the sensor.

[0013] Preferably, the particle size of the lead zirconate titanate particles in step (1) is 1 - 10 μm.

[0014] Preferably, the silane coupling agent is at least one of γ-aminopropyltriethoxysilane (KH-550) or γ-glycidoxypropyltrimethoxysilane (KH-560).

[0015] Preferably, the ratio of the modified PZT to SMPT in step (2) is 17:3; the ratio of SMPT to THF is 1:4.

[0016] Preferably, the hot pressing conditions of the flat vulcanizer in step (3) are 70 - 90 °C and 6 - 10 MPa.

[0017] Preferably, the electric field in step (5) is 1 - 3 kV / mm and the polarization time is 2 - 4 h.

[0018] The second object of the present invention is a highly extensible thin-film piezoelectric sensor for pulse detection, which is prepared according to the preparation method of the highly extensible thin-film piezoelectric sensor for pulse detection.

[0019] Preferably, the thickness of the thin-film piezoelectric sensor is 50 - 70 μm.

[0020] Preferably, the proportion of lead zirconate titanate in the thin-film piezoelectric sensor is 70 - 90%.

[0021] Beneficial effects

[0022] The present invention provides a highly extensible thin-film piezoelectric sensor for pulse detection. Through material system innovation and process optimization, it solves the key contradiction between flexibility and high performance in traditional piezoelectric sensors, achieving a synergistic improvement in low Young's modulus and high extensibility. The Young's modulus is 52 MPa, which is 93% lower than that of conventional PVDF-based sensors (≥800 MPa), and the matching degree with the modulus of human skin (0.1 - 1 MPa) is significantly improved, effectively reducing the wearing pressure. The elongation rate is 177.3%, achieving a breakthrough in ultra-high extensibility of flexible piezoelectric sensors. The surface of PZT is modified with a silane coupling agent, and the silane coupling agent forms chemical bonds on the surface of PZT, significantly enhancing the interfacial bonding force between the inorganic and organic phases, effectively avoiding particle agglomeration, and avoiding stress concentration under high filling amounts. The results show that the highly extensible thin-film piezoelectric sensor for pulse detection and its preparation method provided by the present invention achieve a synergistic improvement in low Young's modulus and ultra-high elongation rate. Description of the Drawings

[0023] Figure 1 SEM image of PZT particles in SMPU in Comparative Example 1

[0024] Figure 2 SEM image of modified PZT particles in SMPU in Example 1

[0025] Figure 3 Tensile curve and Young's modulus diagram of the thin-film piezoelectric sensor.

[0026] Figure 4 Pulse wave diagram formed by the finger artery of the fingertip obtained by the thin-film piezoelectric sensor.

[0027] Figure 5 Schematic diagram of the thin-film piezoelectric sensor for detecting the finger artery of the fingertip. Detailed Description of the Invention

[0028] The technical solutions in the present invention will be clearly and completely described below in conjunction with the embodiments in the present invention.

[0029] Example 1

[0030] A highly extensible thin-film piezoelectric sensor for pulse detection,

[0031] The specific preparation steps are as follows:

[0032] 1. Surface modification of PZT: PZT particles with a particle size of about 5 μm are first ultrasonically cleaned in absolute ethanol, and then added to a mixed solution of acetone and a silane coupling agent (KH-550) in a certain proportion. After ultrasonic dispersion, it is placed in an environment of 50 - 60 °C and stirred evenly at a speed of 800 r / min. Finally, it is dried in an environment of 60 - 70 °C for standby.

[0033] 2. Use modified PZT particles, add them to tetrahydrofuran (THF), and disperse them ultrasonically at a power of 200 W using a cell disrupter. Add SMPU pellets in a certain proportion and stir at a speed of 800 - 1000 r / min for 48 h, then evaporate at a speed of 500 - 600 r / min until SMPU:THF = 1:4. Let it stand for 24 h.

[0034] 3. Uniformly coat the PZT / SMPU / THF mixture on a glass plate, remove it after forming a film. Finally, hot press the PZT / SMPU film ten times under the conditions of 80 °C and 8 MPa using a flat vulcanizer to complete the preparation of the film.

[0035] 4. Use a magnetron sputtering instrument to fabricate square electrodes with a size of 12 mm * 24 mm on both the front and back sides of the PZT / SMPU film (30 μm).

[0036] 5. Place the film in a silicone oil bath at 80 °C, apply an electric field of 2 kV / mm using a withstand voltage tester for polarization operation for 3 h. Finally, encapsulate it with silicone rubber to complete the preparation of the sensor (the total thickness of the sensor is 60 μm).

[0037] Comparative Example 1

[0038] A highly ductile thin-film piezoelectric sensor for pulse detection

[0039] The difference from Example 1 is that the surface of PZT is not modified. The specific steps are as follows:

[0040] 1. Use PZT particles, add them to tetrahydrofuran (THF), and disperse them ultrasonically at a power of 200 W using a cell disrupter. Add SMPU pellets in a certain proportion and stir at a speed of 800 - 1000 r / min for 48 h, then evaporate at a speed of 500 - 600 r / min until SMPU:THF = 1:4. Let it stand for 24 h.

[0041] 2. Uniformly coat the PZT / SMPU / THF mixture on a glass plate, remove it after forming a film. Finally, hot press the PZT / SMPU film ten times under the conditions of 80 °C and 8 Mpa using a flat vulcanizer to complete the preparation of the film.

[0042] 3. Use a magnetron sputtering instrument to fabricate square electrodes with a size of 12 mm * 24 mm on both the front and back sides of the PZT / SMPU film (30 μm).

[0043] 4. Place the film in a silicone oil bath at 80 °C, apply an electric field of 2 kV / mm using a withstand voltage tester for polarization operation for 3 h. Finally, encapsulate it with silicone rubber to complete the preparation of the sensor (the total thickness of the sensor is 60 μm).

[0044] The performance test was carried out on a tensile testing machine, with a maximum tensile test force of 50 N and a tensile speed of 3 mm / min. The pulse signal was collected by an oscilloscope.

[0045] As can be seen from the above examples and comparative examples, the Young's modulus of the thin-film piezoelectric sensor provided by the present invention is 52 MPa, and its elongation rate is 177.3%. The results show that the thin-film piezoelectric sensor for pulse monitoring with a low Young's modulus described in the present invention is a thin-film piezoelectric sensor with a low Young's modulus and good elongation rate.

[0046] In the description of this specification, the description referring to terms such as "one embodiment", "example", "specific example", etc. means that the specific features, structures, materials or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic expressions of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in a suitable manner in any one or more embodiments or examples.

[0047] The above is only the best implementation mode of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the principle of the present invention, several deformations or equivalent replacements can be made to the technical solution of the present invention, and the technical effects of the present invention can also be achieved, which should also be regarded as belonging to the protection scope of the present invention.

Claims

1. A preparation method of a highly extensible thin-film piezoelectric sensor for pulse detection, characterized in that, It includes the following steps: (1) Surface modification of lead zirconate titanate (PZT) particles: Ultrasonically clean PZT particles with a certain particle size in absolute ethanol, then add them to a mixed solution of acetone and silane coupling agent, ultrasonically disperse and stir evenly, and dry for later use. (2) Mix the modified PZT and shape memory polyurethane (SMPT) in proportion and ultrasonically disperse evenly: Ultrasonically disperse the modified PZT particles in tetrahydrofuran (THF), add SMPU according to the proportion and stir, and let it stand. (3) Preparation of PZT / SMPT composite film: Uniformly coat the mixture prepared in step (2) on a glass plate, remove it after forming a film. Finally, hot press the PZT / SMPU film using a flat vulcanizer to complete the preparation of the film. (4) Preparation of electrode layer: Use a magnetron sputtering instrument to fabricate square electrodes on both the front and back sides of the PZT / SMPU film. (5) Preparation of piezoelectric sensor: Apply an electric field to the film prepared in step (4) using a withstand voltage tester for polarization operation, and finally encapsulate it with silica gel to complete the preparation of the sensor.

2. The preparation method according to claim 1, wherein: The modified lead zirconate titanate in step (1) is surface-modified with a silane coupling agent; the silane coupling agent is at least one of γ-aminopropyltriethoxysilane (KH-550) or γ-glycidoxypropyltrimethoxysilane (KH-560).

3. The preparation method according to claim 1, characterized in that: The particle size of the lead zirconate titanate particles in step (1) is 1 - 10 μm.

4. The preparation method according to claim 1, characterized in that: The ratio of the modified PZT to SMPT in step (2) is: 17:3; the ratio of SMPT to THF is 1:

4.

5. The preparation method according to claim 1, characterized in that: The hot pressing conditions of the flat vulcanizer in step (3) are 70 - 90 °C and 6 - 10 Mpa.

6. The preparation method according to claim 1, characterized in that: The electric field in step (5) is 1 - 3 kV / mm, and the polarization time is 2 - 4 h.

7. The thin-film piezoelectric sensor prepared by the preparation method according to any one of claims 1 to 6, characterized in that: The thickness of the thin-film piezoelectric sensor is 50 - 70 μm; the proportion of lead zirconate titanate in the thin-film piezoelectric sensor is 70 - 90%.

8. Application of the thin-film piezoelectric sensor according to claim 7 in pulse detection.

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