Flexible friction electric sensor pulse monitoring system based on intelligent prediction regression network

Abstract

The invention discloses a flexible friction electric sensor pulse monitoring system based on an intelligent prediction regression network, and belongs to the technical field of flexible friction electric sensors. The flexible friction electric sensor comprises a PU thin film layer, an upper friction layer PVA fiber layer, a rubber separation layer, a lower friction layer electrode layer with a corrugated structure, a modified PET substrate layer and a Cu metal shielding layer which are sequentially arranged in an attached mode, the rubber separation layer and the PVA fiber layer are located on the same plane, and the rubber separation layer is provided with a rectangular through hole with the same size as the PVA fiber layer. The PVA fiber layer is located on the inner side of the rectangular through hole. The electrode layer with the corrugated structure and the friction layer with high performance can improve the precision, sensitivity and response speed of the flexible triboelectric sensor, have the characteristics of self power supply, non-invasive monitoring and high stability, can accurately detect human pulse waves, and can process and analyze output data of the flexible triboelectric sensor, so that the flexible triboelectric sensor has good application prospects. The pulse of the human body is monitored.

Description

Technical Field

[0001] This application relates to the technical field of flexible triboelectric sensors, and particularly to a flexible triboelectric sensor pulse monitoring system based on an intelligent prediction regression network. Background Art

[0002] Wearable flexible electronic devices have developed rapidly in aspects such as motion monitoring and human-computer interaction due to their own advantages in flexibility and portability. Such devices can be directly attached to the skin surface or fixed on the body through force rings or straps to collect various body information for determining different body motion states and health conditions. The key component of wearable flexible electronic devices is the flexible sensor. The flexible triboelectric sensor is a converter that directly converts pulsating mechanical signals into corresponding electrical pulse signals. Because of its characteristics of obtaining the physiological information contained in the pulse signal based on the strength of the electrical signal and the characteristic peaks, it has become a popular candidate for the key component of wearable flexible electronic devices.

[0003] CN104779832A discloses a method of using a fluorocarbon plasma treatment process to form micro-nano structures on the polymer surface to increase the roughness of the friction material, thereby improving the electrical output performance of the triboelectric sensor. CN104167949A discloses a heating and embossing treatment technology to obtain a polymer thin film layer with an embossed structure.

[0004] However, the single electrode design and low performance of the friction layer of the above sensors result in low accuracy, poor sensitivity, and slow response speed of the flexible triboelectric sensor. Moreover, the above technical solutions lack the processing and analysis of output data, which is not conducive to their application in the field of pulse monitoring. Summary of the Invention

[0005] In view of this, this application provides a flexible triboelectric sensor pulse monitoring system based on an intelligent prediction regression network, which has a delicate electrode structure and a high-performance friction layer, can improve the accuracy, sensitivity, and response speed of the flexible triboelectric sensor, and processes and analyzes the output data of the flexible triboelectric sensor to monitor the pulse of the user.

[0006] Specifically, the technical solutions include the following: In a first aspect, the present application provides a flexible triboelectric sensor, which includes a PU film layer, a PVA fiber layer, a rubber isolation layer, an electrode layer, a modified PET base layer, and a Cu metal shielding layer that are sequentially attached. The electrode layer has a corrugated structure. The PVA fiber layer is the upper friction layer of the flexible triboelectric sensor, and the electrode layer is the lower friction layer of the flexible triboelectric sensor and also the output electrode of the flexible triboelectric sensor. The rubber isolation layer is in the same plane as the electrode layer and has a rectangular through-hole, and the size of the rectangular through-hole is the same as the size of the PVA fiber layer. The PVA fiber layer is located inside the rectangular through-hole.

[0007] In some embodiments, the PVA fiber layer is prepared by electrospinning. The length of the PVA fiber layer is 1 cm, the width is 1 cm, and the thickness is 50 - 60 μm.

[0008] In some embodiments, the electrode layer is printed on the modified PET base layer by a microelectronic printer. The structure of the electrode layer is a plurality of concentric rings, and the interval between every two concentric rings is 0.6 mm. The width of the concentric rings is 0.4 mm. There is a circle concentric with it in the middle of the innermost concentric ring, and the diameter of the circle is 2 mm. The center of the circle is extended outward along the length direction of the PVA fiber layer from one side, and the plurality of concentric rings and the circle are connected. The width of the extension line is 1 mm, and an electrode layer with a corrugated structure is obtained.

[0009] In some embodiments, the material of the electrode layer is any one of Au, Ag, and Cu, and the thickness of the electrode layer is 6 - 10 μm.

[0010] In some embodiments, the length of the PU film layer is 2 cm and the width is 2 cm; The length of the rubber isolation layer is 2 cm and the width is 2 cm, and the length of the rectangular through-hole is 1 cm and the width is 1 cm; The modified PET base layer has two parts. The length of the first part of the modified PET base layer is 2 m and the width is 2 cm. The length of the second part of the modified PET base layer is 4 cm and the width is 1 cm; The Cu metal shielding layer has two parts. The length of the first part of the Cu metal shielding layer is 2 cm and the width is 2 cm. The length of the second part of the Cu metal shielding layer is 4 cm and the width is 1 cm.

[0011] In some embodiments, the flexible triboelectric sensor further includes a first PI waterproof layer and a second PI waterproof layer; The first PI waterproof layer is adhesively disposed above the extension line portion of the electrode layer. The length of the first PI waterproof layer is 4 cm and the width is 1 cm. The second PI waterproof layer is adhesively disposed between the modified PET base layer and the Cu metal shielding layer. The second PI waterproof layer has two parts. The length of the first part of the second PI waterproof layer is 2 cm and the width is 2 cm. The length of the second part of the second PI waterproof layer is 4 cm and the width is 1 cm.

[0012] In some embodiments, the centers of the PU thin film layer, the PVA fiber layer, the center of the circular shape of the electrode layer, the center of the second part of the modified PET base layer, the center of the second part of the Cu metal shielding layer, and the center of the second part of the second PI waterproof layer are all on the same straight line.

[0013] In some embodiments, the flexible triboelectric sensor has a sensitivity of 6.875 V / kPa and a response time of 7.9 ms. In a second aspect, the present application provides a method for preparing a flexible triboelectric sensor as described above. The method includes the following steps: Step 1: Irradiate one side of the PET film that has been ultrasonically cleaned, rinsed, and dried with ultraviolet light for 5 - 10 min, and then trim it to obtain a modified PET base layer. Step 2: Print an electrode layer on the modified PET base layer with a metal nanoparticle ink having a surface tension of 26 - 29 mN / m, and then perform a drying treatment to obtain a modified PET base layer with an electrode layer. Step 3: Electrospinning is carried out with a PVA solution of 2 - 4 g / mL. After electrospinning is completed, a drying treatment is performed to obtain a PVA fiber layer. Among them, the syringe for electrospinning is 5 mL, the nominal value of the needle tip diameter is 20G, the environmental humidity is 30 - 40%RH, the electrospinning voltage is 15 - 18 kV, the electrospinning time is 3 - 4 h, and the environmental temperature is 25 - 30 °C. Step 4: The PU thin film layer, the PVA fiber layer, the rubber isolation layer, the first PI waterproof layer, the electrode layer, the modified PET base layer, the Cu metal shielding layer, and the second PI waterproof layer are sequentially adhered. The end of the electrode layer extending outward and one end of the DuPont wire are connected with conductive silver glue. In a third aspect, the present application provides a flexible triboelectric sensor pulse monitoring system based on an intelligent prediction regression network. The flexible triboelectric sensor pulse monitoring system based on the intelligent prediction regression network includes the above flexible triboelectric sensor, an amplification and filtering circuit, a control main board, a communication module, a signal processing and analysis module, and a terminal. The flexible triboelectric sensor and the amplification and filtering circuit are connected in sequence. The control main board is connected to the filtering circuit, the communication module, and the terminal. The signal processing and analysis module is installed on the terminal; The flexible triboelectric sensor is used to collect user pulse signals including the user's heart rate, blood pressure, augmentation index, and reflection index; The amplification and filtering circuit is used to amplify the user pulse signal obtained by the flexible triboelectric sensor to obtain an amplified pulse signal, and filter the amplified pulse signal to obtain a filtered pulse signal; The control main board is used to convert the filtered pulse signal in the form of an analog signal into a filtered pulse signal in the form of a digital signal to obtain a digital pulse signal, and send the digital pulse signal to the signal processing and analysis module; The communication module is used to enable the signal processing and analysis module installed on the terminal to communicate with the control main board to send the digital pulse signal to the signal processing and analysis module; The signal processing and analysis module is used to process and analyze the digital pulse signal to determine the user's cardiovascular information; The terminal is used to display the user's cardiovascular information. The beneficial effects of the technical solution provided by the present application at least include: The present application provides a flexible triboelectric sensor pulse monitoring system based on an intelligent prediction regression network. The flexible triboelectric sensor includes a PU film layer, a PVA fiber layer, a rubber isolation layer, an electrode layer, a modified PET base layer, and a Cu metal shielding layer that are sequentially laminated. The electrode layer has a corrugated structure. The PVA fiber layer is the upper friction layer of the flexible triboelectric sensor. The electrode layer is the lower friction layer of the flexible triboelectric sensor and also the output electrode of the flexible triboelectric sensor. The rubber isolation layer is on the same plane as the PVA fiber layer and has a rectangular through hole. The size of the rectangular through hole is the same as the size of the PVA fiber layer. The PVA fiber layer is located inside the rectangular through hole. By setting a delicate electrode structure and a high-performance friction layer, the accuracy, sensitivity, and response speed of the flexible triboelectric sensor can be improved. It has the characteristics of self-power supply, non-invasive monitoring, and high stability, and can accurately detect the pulse wave under the user's superficial skin. The constructed flexible triboelectric sensor pulse monitoring system based on the intelligent prediction regression network can process and analyze the output data of the flexible triboelectric sensor to monitor the user's pulse. Description of the Drawings

[0014] To more clearly illustrate the technical solutions in the embodiments of the present application, the following will briefly introduce the accompanying drawings required for the description of the embodiments. Obviously, the accompanying drawings in the following description are only some embodiments of the present application. For those of ordinary skill in the art, without creative efforts, other accompanying drawings can also be obtained based on these drawings.

[0015] Figure 1 Schematic structural diagram of the flexible triboelectric sensor provided by the embodiment of the present application; Figure 2 Schematic structural diagram of the electrode layer of the flexible triboelectric sensor provided by the embodiment of the present application; Figure 3(a) is a schematic diagram of the electrical and mechanical characteristics of the flexible triboelectric sensor provided by the embodiment of the present application; Figure 3(b) is a schematic diagram of the open-circuit voltage curve of the flexible triboelectric sensor provided by the embodiment of the present application at different operating frequencies; Figure 3(c) is a schematic diagram of the response and recovery time of the flexible triboelectric sensor provided by the embodiment of the present application; Figure 3(d) is a schematic diagram of the change curve of the open-circuit voltage of the flexible triboelectric sensor provided by the embodiment of the present application with different spacings between the upper and lower friction layers; Figure 3(e) is a schematic diagram of the open-circuit voltage curve of the flexible triboelectric sensor provided by the embodiment of the present application under different pressures; Figure 3(f) is a schematic diagram of the linearity test result of the flexible triboelectric sensor provided by the embodiment of the present application; Figure 3(g) is a schematic diagram of the stability test result of the flexible triboelectric sensor provided by the embodiment of the present application; Figure 4(a) is a schematic diagram of the 30s radial artery pulse signal monitored by the flexible triboelectric sensor provided by the embodiment of the present application: Figure 4(b) is a partial enlarged schematic diagram of the 30s radial artery pulse signal monitored by the flexible triboelectric sensor provided by the embodiment of the present application: Figure 4(c) is a superimposed effect diagram of each complete pulse wave in the 30s radial artery pulse signal monitored by the flexible triboelectric sensor provided by the embodiment of the present application; Figure 5(a) is a schematic diagram of the 30s radial artery pulse signal monitored by the commercial flexible pulse sensor provided by the embodiment of the present application: Figure 5(b) is a partial enlarged schematic diagram of the 30s radial artery pulse signal monitored by the commercial flexible pulse sensor provided by the embodiment of the present application: Figure 5(c) is a superimposed effect diagram of each complete pulse wave in the 30s radial artery pulse signal monitored by the commercial flexible pulse sensor provided by the embodiment of the present application; Figure 6(a) is the effect diagram of the stability test of the flexible triboelectric sensor provided by the embodiment of the present application; Figure 6(b) is the schematic diagram of the average heart rate of the radial artery pulse signal monitored by the flexible triboelectric sensor provided by the embodiment of the present application for 90s; Figure 6(c) is the schematic diagram of the average augmentation index of the radial artery pulse signal monitored by the flexible triboelectric sensor provided by the embodiment of the present application for 90s; Figure 6(d) is the schematic diagram of the average time difference of the radial artery pulse signal monitored by the flexible triboelectric sensor provided by the embodiment of the present application for 90s; Figure 6(e) is the schematic diagram of the average reflection index of the radial artery pulse signal monitored by the flexible triboelectric sensor provided by the embodiment of the present application for 90s; Figure 6(f) is the schematic diagram of the average systolic upstroke time of the radial artery pulse signal monitored by the flexible triboelectric sensor provided by the embodiment of the present application for 90s; Figure 7(a) is the schematic diagram of the internal elbow pulse signal monitored by the flexible triboelectric sensor provided by the embodiment of the present application; Figure 7(b) is the schematic diagram of the neck pulse signal monitored by the flexible triboelectric sensor provided by the embodiment of the present application; Figure 8(a) is the schematic diagram of the measurement method for monitoring the pulse by the flexible triboelectric sensor provided by the embodiment of the present application; Figure 8(b) is the curve of the pressure change during cuff inflation and the corresponding user pulse change when the flexible triboelectric sensor provided by the embodiment of the present application monitors the pulse; Figure 9(a) is the schematic diagram of the pulse signal of the user monitored by the flexible triboelectric sensor provided by the embodiment of the present application at 8:00 in the morning; Figure 9(b) is the schematic diagram of the pulse signal of the user monitored by the flexible triboelectric sensor provided by the embodiment of the present application at 10:00 in the morning; Figure 9(c) is the schematic diagram of the pulse signal of the user monitored by the flexible triboelectric sensor provided by the embodiment of the present application at 12:00 noon; Figure 9(d) is the schematic diagram of the pulse signal of the user monitored by the flexible triboelectric sensor provided by the embodiment of the present application at 2:00 in the afternoon; Figure 9(e) is the schematic diagram of the pulse signal of the user monitored by the flexible triboelectric sensor provided by the embodiment of the present application at 4:00 in the afternoon; Figure 9(f) is the schematic diagram of the pulse signal of the user monitored by the flexible triboelectric sensor provided by the embodiment of the present application at 6:00 in the afternoon; Figure 9(g) is the schematic diagram of the heart rate curve obtained based on the pulse signal of the user monitored by the flexible triboelectric sensor provided by the embodiment of the present application; Figure 9(h) is a schematic diagram of the systolic upstroke time curve obtained from the user's pulse signal monitored by the flexible triboelectric sensor provided in the embodiment of the present application; Figure 9(i) is the P obtained from the user's pulse signal monitored by the flexible triboelectric sensor provided in the embodiment of the present application 1 and P 3 schematic diagram of the time difference curve; Figure 10 is a scanning electron microscope (SEM) schematic diagram of the PVA fiber layer in the preparation method of the flexible triboelectric sensor provided in the embodiment of the present application; Figure 11(a) is a schematic diagram of the structure of the flexible triboelectric sensor pulse monitoring system based on the intelligent prediction regression network provided in the embodiment of the present application; Figure 11(b) is a schematic diagram of the structure of the physiological information prediction regression network of the flexible triboelectric sensor pulse monitoring system based on the intelligent prediction regression network provided in the embodiment of the present application; Figure 12(a) is a schematic diagram of the prediction accuracy of the heart rate HR by the physiological information prediction regression network of the flexible triboelectric sensor pulse monitoring system based on the intelligent prediction regression network provided in the embodiment of the present application; Figure 12(b) is the P of the physiological information prediction regression network of the flexible triboelectric sensor pulse monitoring system based on the intelligent prediction regression network provided in the embodiment of the present application 1 and P 3 schematic diagram of the prediction accuracy of the time difference PPT between; Figure 12(c) is a schematic diagram of the prediction accuracy of the reflection index RI by the physiological information prediction regression network of the flexible triboelectric sensor pulse monitoring system based on the intelligent prediction regression network provided in the embodiment of the present application; Figure 12(d) is a schematic diagram of the prediction accuracy of the systolic upstroke time UT by the physiological information prediction regression network of the flexible triboelectric sensor pulse monitoring system based on the intelligent prediction regression network provided in the embodiment of the present application; Figure 13 is a schematic diagram of the user pulse monitoring process of the flexible triboelectric sensor pulse monitoring system based on the intelligent prediction regression network provided in the embodiment of the present application. The reference numerals in the figure are respectively indicated as.

[0016] 1 - PU film layer, 2 - PVA fiber layer, 3 - rubber isolation layer, 4 - electrode layer, 5 - modified PET base layer, 6 - Cu metal shielding layer, 7 - Cu metal shielding layer, 7 - first PI waterproof layer, 8 - second PI waterproof layer. Detailed implementation manners

[0017] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present application. Obviously, the described embodiments are some, but not all, of the embodiments of the present application. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present application without creative efforts shall fall within the protection scope of the present application.

[0018] To make the technical solutions and advantages of the present application clearer, the embodiments of the present application will be further described in detail below with reference to the accompanying drawings.

[0019] As Figure 1 shown, in the first aspect of the present application, a flexible triboelectric sensor is provided. The flexible triboelectric sensor includes a PU film layer 1, a PVA fiber layer 2, a rubber isolation layer 3, a waterproof layer 7, an electrode layer 4, a modified PET base layer 5, and a Cu metal shielding layer 6 that are sequentially attached. The electrode layer 4 has a corrugated structure. The PVA fiber layer 2 is the upper friction layer of the flexible triboelectric sensor, and the electrode layer 4 is the lower friction layer of the flexible triboelectric sensor and also the output electrode of the flexible triboelectric sensor. The rubber isolation layer 3 is on the same plane as the PVA fiber layer and has a rectangular through-hole. The size of the rectangular through-hole is the same as the size of the PVA fiber layer, and the PVA fiber layer is located inside the rectangular through-hole.

[0020] The PU film layer 1 has the characteristics of being ultra-thin, flexible, and skin-friendly, facilitating the direct close contact between the flexible friction sensor and the user's skin through the PU film, enhancing the detection accuracy, and improving the user experience.

[0021] The rubber isolation layer 3 surrounding the outside of the PVA fiber layer plays a protective role for the electrode layer 4 and makes the PVA fiber layer 2 closely adhere to the first PI waterproof layer 7 and the electrode layer 4, thus better demonstrating the friction effect.

[0022] In some embodiments, the PVA fiber layer 2 is prepared by electrospinning. The length of the PVA fiber layer 2 is 1 cm, the width is 1 cm, and the thickness is 50 - 60 μm.

[0023] The PVA fiber layer 2 located below the PU film layer 1 is prepared by electrospinning and has the characteristics of being ultra-thin, homogeneous, and dense, and has a stronger triboelectric effect compared to the PVA film in film form.

[0024] The modified PET film has high transparency and excellent mechanical properties, which is beneficial to the triboelectric performance of the flexible triboelectric sensor.

[0025] An electrode layer 4 with a corrugated structure is arranged on the modified PET film, which serves as the lower friction layer of the flexible triboelectric sensor and also acts as the output electrode of the flexible triboelectric sensor. The exquisite corrugated structure improves the triboelectric performance, facilitates the subsequent monitoring of the user's health status, and captures tiny signal fluctuations, such as the user's pulse.

[0026] By providing the Cu metal shielding layer 6, the flexible triboelectric sensor can be made resistant to electromagnetic interference, thereby ensuring stable operation of the flexible triboelectric sensor.

[0027] like Figure 2 As shown, in the above-mentioned flexible triboelectric sensor, the electrode layer 4 can be printed on the modified PET base layer 5 by a microelectronic printer, and the structure of the electrode layer 4 has multiple concentric rings, the interval between each two concentric rings is 0.6mm, the width of the concentric rings is 0.4mm, and there is a circle concentric with the innermost concentric ring in the middle, the diameter of the circle is 2mm, and the center of the circle is extended outward from one side along the length direction of the PVA fiber layer 2, and multiple concentric rings and the circle are connected, and the width of the extension line is 1mm, so as to obtain an electrode layer 4 with a corrugated structure.

[0028] In some embodiments, Figure 2 As shown, the number of concentric circles can be four.

[0029] In the above-mentioned flexible triboelectric sensor, the material of the electrode layer 4 is any one of Au, Ag and Cu, and the thickness of the electrode layer 4 can be 6-10 μm.

[0030] It should be noted that Ag material has the best conductivity as the material of the electrode layer 4 and can reduce the loss of weak signals during the sensing process.

[0031] In some embodiments, the PU film layer 1 has a length of 2 cm and a width of 2 cm; the rubber partition layer 3 has a length of 2 cm and a width of 2 cm, and the rectangular through hole has a length of 1 cm and a width of 1 cm; the modified PET base layer 5 has two parts, the first part of the modified PET base layer 5 has a length of 2 cm and a width of 2 cm, and the second part of the modified PET base layer 5 has a length of 4 cm and a width of 1 cm; the Cu metal shielding layer 6 has two parts, the first part of the Cu metal shielding layer 6 has a length of 2 cm and a width of 2 cm, and the second part of the Cu metal shielding layer 6 has a length of 4 cm and a width of 1 cm.

[0032] In some embodiments, the flexible triboelectric sensor further includes a first PI waterproof layer 7 and a second PI waterproof layer 8; the first PI waterproof layer 7 is disposed in a fitting manner above the extension line portion of the electrode layer 4, the length of the first PI waterproof layer 7 is 4 cm, and the width is 1 cm; the second PI waterproof layer 8 is disposed in a fitting manner between the modified PET base layer 5 and the Cu metal shielding layer 6, the second PI waterproof layer 8 has two parts, the length of the first part of the second PI waterproof layer 8 is 2 cm, the width is 2 cm, and the length of the second part of the second PI waterproof layer 8 is 4 cm, the width is 1 cm.

[0033] By providing the first PI waterproof layer 7 and the second PI waterproof layer 8, the flexible triboelectric sensor has a waterproof function. When the user sweats or is exposed to environments such as humidity or rainy days, the flexible triboelectric sensor can also perform high-performance detection.

[0034] In some embodiments, the centers of the PU film layer 1, the PVA fiber layer 2, the center of the circular shape of the electrode layer 4, the center of the second part of the modified PET base layer 5, the center of the second part of the Cu metal shielding layer 6, and the center of the second part of the second PI waterproof layer 8 are all on the same straight line.

[0035] In some embodiments, the flexible triboelectric sensor has a sensitivity of 6.875 V / kPa and a response time of 7.9 ms.

[0036] With such a setting, the structure of the flexible triboelectric sensor is small and compact. By utilizing the friction between the electrode layer 4 with a corrugated structure and the PVA fiber layer 2, and through the cooperation of the various layers of the flexible triboelectric sensor, the flexible triboelectric sensor has high precision, high sensitivity, and fast response speed, and has the characteristics of self-power supply, skin-friendly, waterproof, and anti-wear.

[0037] During the test, the flexible triboelectric sensor is divided into two parts. The PU film layer 1, the PVA fiber layer 2, and the rubber isolation layer 3 are the first part, and the electrode layer 4, the modified PET base layer, and the Cu metal shielding layer 6 are the second part. The first part is slapped on the second part at a certain frequency and pressure, so that the PVA fiber layer 2 as the upper friction layer generates electricity by friction with the electrode layer 4 as the lower friction layer. Figure 3(a) is a schematic diagram of the electrical and mechanical characteristics of the flexible triboelectric sensor provided by the embodiment of the present application. Taking the material of the electrode layer 4 as Ag as an example, the atomic-level electron cloud potential well model between the Ag electrode and the PVA fiber layer 2 can well explain the process of electricity generation by friction of the flexible triboelectric sensor, and d is the distance between the electrode layer 4 and the PVA fiber layer 2. As shown in Figure 3(b), under a pressure of 100 Pa, the open-circuit voltage of the flexible triboelectric sensor is detected at working frequencies of 1 Hz, 2 Hz, 3 Hz, 4 Hz, and 5 Hz respectively. The results show that the working frequency has little effect on the open-circuit voltage of the flexible triboelectric sensor. As shown in Figure 3(c), in the above case, the response and recovery times of the flexible triboelectric sensor are both 7.9 ms. Due to the change in the distance between the upper and lower friction layers during slapping friction, the flexible triboelectric sensor will exhibit different output capabilities. As can be seen from Figure 3(d), when the distance is 10 mm, the open-circuit voltage of the flexible triboelectric sensor is the largest. As shown in Figure 3(e), when the working frequency is set to 5 Hz, the open-circuit voltage of the flexible triboelectric sensor is tested under pressures of 20 Pa, 40 Pa, 60 Pa, 80 Pa, and 100 Pa respectively. As the pressure increases, the open-circuit voltage of the flexible triboelectric sensor gradually increases. Figure 3(f) proves that the flexible triboelectric sensor has an extremely high linear working range under low-amplitude pulse pressure, and the correlation coefficient R 2 is as high as 0.99, and it also proves that the sensitivity in this pressure range reaches 6.875 V / kPa. To prove the long-term working stability of the flexible triboelectric sensor, 3000 cyclic tests were carried out on it. As shown in Figure 3(g), the open-circuit voltage and short-circuit current of the flexible triboelectric sensor show extremely strong stability during 3000 cyclic tests.

[0038] In some embodiments, the flexible triboelectric sensor can be used to monitor the pulse signal of a user.

[0039] To demonstrate the potential and accuracy of the flexible triboelectric sensor in monitoring pulse signals, as shown in Figure 4(a), the radial artery pulse wave of a 31-year-old tester is monitored through the flexible triboelectric sensor for 30 s, and it can be seen that the flexible triboelectric sensor can capture the pulse beats of the tester. As shown in Figure 4(b), one pulse beat of the tester within these 30 s has three typical characteristic peaks: the forward wave (P 1 ), the reflected wave (P 2 ), and the dicrotic wave (P3 ), and these three typical characteristic peaks are accurately monitored by the flexible triboelectric sensor. To study the consistency between each waveform during the same measurement process, each complete pulse wave is superimposed in the same time period, and the superimposed result is shown in Fig. 4(c). The average Pearson correlation coefficient P between each period is 0.951, indicating that each period waveform obtained by the flexible triboelectric sensor has a high degree of consistency. To prove the good monitoring effect of the flexible triboelectric sensor, a commercially available flexible pulse sensor (NANO POLIS CP301) was purchased and compared and tested according to the above principle. As shown in Fig. 5(a), the radial artery pulse wave of a 31-year-old tester was monitored by the flexible triboelectric sensor for 30 s, and the pulse beats of this tester captured by the commercially available flexible pulse sensor can be seen. As shown in Fig. 5(b), one pulse beat of this tester within these 30 s has three typical characteristic peaks: the forward wave (P 1 ), the reflected wave (P 2 ), and the dicrotic wave (P 3 ). Fig. 5(c) shows the result of superimposing each complete pulse wave in the same time period, and the average Pearson correlation coefficient P between each period is 0.961. By comparing the flexible triboelectric sensor and the purchased commercially available flexible pulse sensor, it can be found that the performance of this flexible triboelectric sensor is very close to that of the commercially available flexible pulse sensor and can be self-powered without an external power supply.

[0040] To test the sufficient stability of the flexible triboelectric sensor during continuous pulse monitoring, the radial artery pulse wave of a 31-year-old tester was monitored for 90 s. As shown in Fig. 6(a), the flexible triboelectric sensor has good stability. The heart rate (HR), augmentation index (AIr), P 1 and P 3 time difference (PPT), reflection index (RI), and systolic upstroke time (UT) can be obtained from the pulse signal. As shown in Figs. 6(b) to 6(f), based on the above 90-s pulse signal, the average heart rate of this tester is 62 beats / min, the average AIr is 0.84, the average PPT is 0.53 s, the average RI is 3.22 m / s, and the average UT is 0.14 s.

[0041] Since the source of the pulse is the periodic pulsation of the heart, in addition to the wrist, the superficial pulses at other positions of the human body can also be detected. Figs. 7(a) and 7(b) respectively show the pulse waveforms of the inner elbow and neck monitored by the flexible triboelectric sensor, and obvious characteristic peaks can be seen.

[0042] To clarify the impact of the upper artery on the anterior artery of the extremities under compression, the pulse waveforms of the arm artery from fully open to fully closed and then to fully open states were tested using a flexible triboelectric sensor and a sphygmomanometer. The measurement method is shown in Fig. 8(a). During the measurement, the upper part of the arm was first tied with a cuff, and then the triboelectric sensor was placed on the radial artery. The sphygmomanometer was used to monitor the real-time changes in blood pressure. Before inflating the cuff, the blood vessels were in a fully open state. After starting to inflate the cuff, the sphygmomanometer detected the blood pressure, and the arm artery gradually closed under the cuff pressure until it opened again after the detection was completed. Fig. 8(b) shows the pressure change of the cuff inflation and the corresponding pulse change curve of the tester. When the cuff pressure reached 56 mmHg, the pulse peak changed. When the cuff pressure reached 106 mmHg, the flexible triboelectric sensor could no longer detect the pulse beat. As the cuff pressure reached the peak and gradually decreased, the pulse gradually recovered. When the cuff pressure decreased to 83 mmHg, the flexible triboelectric sensor could detect a weak pulse. When the cuff pressure decreased to 63 mmHg, the arm artery was fully open, and the flexible triboelectric sensor could detect a perfect pulse signal. Therefore, the flexible triboelectric sensor can sense the changes in arterial pulse in real time.

[0043] The change of pulse over time also reflects the user's health status and makes an important contribution to the prevention of cardiovascular diseases. Figs. 9(a) to 9(f) show the pulse signals of a 23-year-old male tester monitored by the flexible triboelectric sensor. The pulse was measured every two hours from 8 am to 6 pm. It can be seen that the amplitude of the pulse signal of this tester increased slightly during the period close to noon and then decreased in the afternoon. This is in line with traditional Chinese medicine theory. Traditional Chinese medicine believes that the period from 11 am to 1 pm is the time when the heart meridian flows, and the pulse will be strengthened during this period. Figs. 9(g) to 9(i) successively give the corresponding heart rate (HR), systolic up time (UI), and the time difference (PPT) between P 1 and P 3 . The heart rate of this tester was the highest at 8 am, and there was not much difference in the heart rate at other times. The UI reached the maximum at 2 pm, and the minimum value of PPT appeared at 12 noon.

[0044] In summary, the present application provides a flexible triboelectric sensor. By setting a delicate electrode structure and a high-performance friction layer, the accuracy, sensitivity, and response speed of the flexible triboelectric sensor can be improved. It has the characteristics of self-power supply, non-invasive monitoring, and high stability, and has the potential for long-term monitoring of pulse signals. In a second aspect, an embodiment of the present application provides a preparation method for the flexible triboelectric sensor described in the first aspect of the present application. The method includes the following steps: Step 1: Unidirectionally irradiate the PET film that has been ultrasonically cleaned, rinsed, and dried with ultraviolet light for 5 - 10 min, and then trim it to obtain the modified PET base layer 5.

[0045] It should be noted that unidirectional ultraviolet irradiation can modify the PET film. The modified PET base layer 5 obtained in Step 1 has high transparency and excellent mechanical properties, which is beneficial to the triboelectric performance of the flexible triboelectric sensor.

[0046] In some embodiments, the specific implementation of Step 1 can be as follows: Take a 100 - μm - thick PET film in the shape of a 5 cm×10 cm rectangle, curl it and place it in a beaker, and pour an appropriate amount of ethanol solution; Seal the beaker with plastic wrap and place it in an ultrasonic cleaner to ultrasonically clean the surface of the PET film for 30 min; Take out the cleaned PET film from the beaker, rinse it repeatedly with deionized water 3 times, and put it in a vacuum drying oven to dry at 60 °C for 1 h; Lay the obtained PET film flat in the chamber of an ultraviolet light cleaner, unidirectionally irradiate and modify one side of the PET film with ultraviolet light for 5 min, and then cut it to obtain the modified PET base layer 5.

[0047] Step 2: Print the electrode layer 4 on the modified PET base layer 5 with a metal nanoparticle ink having a surface tension of 26 - 29 mN / m, and then perform a drying treatment to obtain the modified PET base layer 5 with the electrode layer 4.

[0048] The electrode layer 4 printed with a metal nanoparticle ink having a surface tension of 26 - 29 mN / m has good tensile properties.

[0049] Preferably, in the above - mentioned preparation method, the metal nanoparticle ink in Step 2 can be Ag nanoparticle ink.

[0050] In some embodiments, the specific implementation of Step 2 can be as follows: Use a metal nanoparticle ink having a surface tension of 26 - 29 mN / m and a DP500 micro - printer (model: Sigma - Aldrich 901083 - 25ML) to first print an electrode layer 4 having a plurality of concentric rings and a circle on the modified PET base layer 5. After completion, place the modified PET base layer 5 with the electrode layer 4 in a 60 °C vacuum drying oven for 1 h; Place the above - obtained product back at the original position on the DP500 printing table, and print an electrode from the center of the circle along the length direction of the PVA fiber layer 2 from one side outward, so that the electrode connects the plurality of concentric rings and the circle, and then place it in a 60 °C vacuum drying oven for 1 h to obtain the modified PET base layer 5 with the electrode layer 4.

[0051] In some embodiments, for the convenience of detection or connection with other devices and instruments, a Dupont wire is connected to the end of the strip-shaped electrode of the electrode layer 4 with conductive silver glue, thereby leading out the detection end.

[0052] Step 3: Electrospinning is carried out with a PVA solution of 2 - 4 g / mL. After electrospinning is completed, drying treatment is carried out to obtain the PVA fiber layer 2. Among them, the syringe for electrospinning is 5 mL, the nominal value of the needle head diameter is 20G, the environmental humidity is 30 - 40%RH, the electrospinning voltage is 15 - 18 kV, the electrospinning time is 3 - 4 h, and the environmental temperature is 25 - 30 °C.

[0053] By setting the relevant parameters of electrospinning in this way, the obtained PVA fiber layer 2 can be ultrathin, homogeneous and dense, and has a more triboelectric effect compared with the PVA film in the form of a film. As Figure 10 shown, the fiber diameter of the PVA fiber layer 2 is 200 - 500 nm.

[0054] In the above preparation method, the specific implementation manner of step 3 can be: adding 2 g of PVA particles into 20 mL of deionized water, placing the mixture in a water bath at 90 °C and magnetically stirring for 3 h. After completion, take out the beaker and wait for the temperature to drop to 36 °C and keep it; take 5 mL of the obtained viscous solution into the syringe, the nominal value of the needle head diameter is 20G, the environmental humidity is 30%RH, the electrospinning voltage is 18 kV, the electrospinning time is set to 4 h, and the environmental temperature is 25 °C; place the obtained product in a vacuum drying oven at 60 °C for 1 h to obtain the PVA fiber layer 2.

[0055] It should be noted that the above PVA particles are from Shanghai Macklin Biochemical Technology Co., Ltd.

[0056] Step 4: The PU film layer 1, the PVA fiber layer 2, the rubber isolation layer 3, the first PI waterproof layer 7, the electrode layer 4, the modified PET base layer 5, the Cu metal shielding layer 6 and the second PI waterproof layer 8 are sequentially laminated, and the end of the electrode layer 4 extending outward and one end of the Dupont wire are connected with conductive silver glue.

[0057] In the above preparation method, the specific implementation manner of step 4 can be: using the rubber isolation layer 3 to isolate the periphery of the electrode layer 4; coating a layer of the first PI waterproof layer 7 on the upper surface of the rubber isolation layer 3; laminating the PVA fiber layer 2 with the rubber isolation layer 3, and pasting the PU film layer 1 on the upper surface of the PVA fiber layer 2; pasting the modified PET base layer 5 with the electrode layer 4 on the first PI waterproof layer 7 so that the electrode layer 4 is closely attached to the first PI waterproof layer 7; pasting a Cu metal shielding layer 6 with the same size specification on the lower surface of the modified PET base layer 5 to resist electromagnetic interference; pasting the second PI waterproof layer 8 on the lower surface of the Cu metal shielding layer 6.

[0058] In some embodiments, the first PI waterproof layer 7 and the second PI waterproof layer 8 may be waterproof sealants.

[0059] In some embodiments, the Cu metal shielding layer 6 may be a copper foil.

[0060] In summary, the PVA fiber layer 2 obtained by the preparation method of the flexible triboelectric sensor provided by the embodiments of the present application has the characteristics of being ultra-thin, homogeneous, dense, and having a good triboelectric effect. The prepared flexible triboelectric sensor can capture the user's pulse beat and reflect the user's physical state. In a third aspect, the embodiments of the present application provide a flexible triboelectric sensor pulse monitoring system based on an intelligent prediction regression network. As shown in FIG. 11(a), the flexible triboelectric sensor pulse monitoring system based on an intelligent prediction regression network includes a flexible triboelectric sensor, an amplification and filtering circuit, a control main board, a communication module, a signal processing and analysis module, and a terminal. The flexible triboelectric sensor and the amplification and filtering circuit are connected in sequence. The control main board is connected to the filtering circuit, the communication module, and the terminal. The signal processing and analysis module is loaded on the terminal. The flexible triboelectric sensor is used to collect user pulse signals including the user's heart rate, blood pressure, augmentation index, and reflection index. The amplification and filtering circuit is used to amplify the user pulse signals obtained by the flexible triboelectric sensor to obtain amplified pulse signals, and filter the amplified pulse signals to obtain filtered pulse signals. The control main board is used to convert the filtered pulse signals in analog signal form into filtered pulse signals in digital signal form to obtain digital pulse signals, and send the digital pulse signals to the signal processing module. The communication module is used to enable the signal processing and analysis module loaded on the terminal to communicate with the control main board to send the digital pulse signals to the signal processing and analysis module. The signal processing and analysis module is used to process and analyze the digital pulse signals to determine the user's cardiovascular information. The terminal is used to display the user's cardiovascular information.

[0061] In some embodiments, the amplification and filtering circuit may include an LM358 amplifier to amplify the user pulse signals obtained by the flexible triboelectric sensor to obtain amplified pulse signals, and may also include an OP07 filter to filter the amplified pulse signals to obtain filtered pulse signals.

[0062] In some embodiments, the cut-off frequency of the amplification and filtering circuit may be as low as 6 Hz to meet the amplification and filtering of low-frequency pulse signals.

[0063] It should be noted that the user's pulse signals are low-frequency signals and have low-frequency requirements for the cut-off frequency of the amplification and filtering circuit. Being as low as 6 Hz can ensure the amplification and filtering of the user's pulse signals.

[0064] In some embodiments, the control main board may be an STM32F407 single-chip microcomputer.

[0065] In some embodiments, a signal processing and analysis module programmed with Labview can be installed on the terminal to communicate with the control main board.

[0066] In some embodiments, the signal processing and analysis module may include a deep learning CNN model programmed with Python within the TensorFlow system to process and analyze digital pulse signals, thereby determining user cardiovascular information.

[0067] In some embodiments, there is a feature peak search algorithm and a physiological information prediction regression network in the signal processing and analysis module. When the digital pulse signal is transmitted to the signal processing and analysis module through the communication module, the feature peak search algorithm will cut and mark the feature peaks of the pulse, and then store these data as an Excel file and send it to the physiological information prediction regression network. This network can extract four physiological information, namely heart rate (HR), the time difference (PPT) between P 1 and P 3 , reflection index (RI), and systolic upslope time (UT) from these information.

[0068] Figure 11(b) shows the structure of the physiological information prediction regression network, which has six convolutional layers, two fully connected layers, three max pooling layers, and one linear regression layer Linear. The specific training process of the physiological information prediction regression network is as follows: First, prepare the pulse data of three users, with a total of 300 complete pulse data; these data are divided into a training set, a validation set, and a test set, and the proportions of the three data sets are 60%, 20%, and 20% respectively. The training set is used to train the network; after 200 rounds of training, the loss function value of the network reaches a very low level; the validation set and the test set are used to validate and test the network. When the convergence speed of the loss function meets the requirements, the final physiological information prediction regression network is obtained.

[0069] Figures 12(a) to 12(d) show the prediction accuracies of the physiological information prediction regression network for HR, PPT, RI, and UT respectively. All data points are closely distributed around the line X = Y. MAE represents the mean absolute error, and RMSE represents the root mean square error. Except that the error of HR is greater than 1, the errors of the other three parameters are less than 0.5. It can be seen that the physiological information prediction regression network is very effective in deeply mining cardiovascular information.

[0070] In some embodiments, the communication module can be integrated on the control main board.

[0071] Figure 13 This is a schematic diagram of the user pulse monitoring process of the flexible triboelectric sensor pulse monitoring system based on the intelligent prediction regression network provided by the embodiments of this application. AsFigure 13 As shown, the flexible triboelectric sensor amplifies and filters the collected user pulse signal through an amplification and filtering circuit, and then the control main board integrated with a communication module receives it and converts it into a digital pulse signal. The control main board sends the digital pulse signal to the signal processing and analysis module on the terminal, and the terminal finally displays the cardiovascular information of the user.

[0072] The flexible triboelectric sensor pulse monitoring system based on the intelligent prediction regression network provided by the embodiments of the present application can monitor the user's pulse, process and analyze the user's pulse data, thereby providing a reliable means for the user's cardiovascular care and effectively realizing the mining and analysis of cardiovascular information.

[0073] In the present application, the terms "first" and "second" are only used for descriptive purposes and cannot be construed as indicating or implying relative importance. The term "plurality" refers to two or more, unless otherwise clearly defined.

[0074] After considering the specification and practicing the present application disclosed herein, those skilled in the art will readily think of other embodiments of the present application. The present application is intended to cover any variations, uses, or adaptations of the present application, which follow the general principles of the present application and include common general knowledge or conventional technical means in the technical field not disclosed in the present application. The specification and examples are only regarded as exemplary.

[0075] It should be understood that the present application is not limited to the exact structure already described and shown in the drawings, and various modifications and changes can be made without departing from its scope. The scope of the present application is only limited by the appended claims.

Claims

1. A flexible triboelectric sensor, characterized in that, the flexible triboelectric sensor comprises a PU film layer (1), a PVA fiber layer (2), a rubber isolation layer (3), an electrode layer (4), a modified PET base layer (5) and a Cu metal shielding layer (6) which are sequentially laminated. The electrode layer (4) has a corrugated structure. The PVA fiber layer (2) is the upper friction layer of the flexible triboelectric sensor. The electrode layer (4) is the lower friction layer of the flexible triboelectric sensor and also the output electrode of the flexible triboelectric sensor. The rubber isolation layer (3) is in the same plane as the PVA fiber layer (2) and has a rectangular through-hole. The size of the rectangular through-hole is the same as the size of the PVA fiber layer (2). The PVA fiber layer (2) is located inside the rectangular through-hole.

2. The flexible triboelectric sensor according to claim 1, characterized in that, the PVA fiber layer (2) is prepared by electrospinning. The length of the PVA fiber layer (2) is 1 cm, the width is 1 cm, and the thickness is 50 - 60 μm.

3. The flexible triboelectric sensor according to claim 2, characterized in that, the electrode layer (4) is printed on the modified PET base layer (5) by a microelectronic printer. The electrode layer (4) has a plurality of concentric rings. The interval between every two concentric rings is 0.6 mm. The width of the concentric rings is 0.4 mm. There is a circle concentric with it in the middle of the innermost concentric ring. The diameter of the circle is 2 mm. The center of the circle is extended outward along the length direction of the PVA fiber layer (2) from one side, and the plurality of concentric rings and the circle are connected. The width of the extension line is 1 mm, obtaining the electrode layer 4 with a corrugated structure.

4. The flexible triboelectric sensor according to claim 3, characterized in that, the material of the electrode layer (4) is any one of Au, Ag and Cu. The thickness of the electrode layer (4) is 6 - 10 μm.

5. The flexible triboelectric sensor according to claim 3, characterized in that, the length of the PU film layer (1) is 2 cm and the width is 2 cm; the length of the rubber isolation layer (3) is 2 cm and the width is 2 cm. The length of the rectangular through-hole is 1 cm and the width is 1 cm; the modified PET base layer (5) has two parts. The length of the first part of the modified PET base layer (5) is 2 cm and the width is 2 cm. The length of the second part of the modified PET base layer (5) is 4 cm and the width is 1 cm; the Cu metal shielding layer (6) has two parts. The length of the first part of the Cu metal shielding layer (6) is 2 cm and the width is 2 cm. The length of the second part of the Cu metal shielding layer (6) is 4 cm and the width is 1 cm.

6. The flexible triboelectric sensor according to claim 5, characterized in that, the flexible triboelectric sensor further comprises a first PI waterproof layer (7) and a second PI waterproof layer (8); The first PI waterproof layer (7) is adhesively disposed above the extension line portion of the electrode layer (4). The first PI waterproof layer (7) has a length of 4 cm and a width of 1 cm. The second PI waterproof layer (8) is adhesively disposed between the modified PET base layer (5) and the Cu metal shielding layer (6). The second PI waterproof layer (8) has two parts. The first part of the second PI waterproof layer (8) has a length of 2 cm and a width of 2 cm. The second part of the second PI waterproof layer (8) has a length of 4 cm and a width of 1 cm.

7. The flexible triboelectric sensor according to claim 6, characterized in that the center of the PU thin film layer (1), the center of the PVA fiber layer (2), the center of the circle of the electrode layer (4), the center of the second part of the modified PET base layer (5), the center of the second part of the Cu metal shielding layer (6), and the center of the second part of the second PI waterproof layer (8) are all on the same straight line.

8. The flexible triboelectric sensor according to claim 1, characterized in that the flexible triboelectric sensor has a sensitivity of 6.875 V / kPa and a response time of 7.9 ms.

9. A method for preparing a flexible triboelectric sensor according to any one of claims 1-8, characterized in that the method comprises the following steps: Step 1: Unidirectionally irradiate the PET thin film that has been ultrasonically cleaned, rinsed, and dried with ultraviolet light for 5-10 min, and trim it to obtain the modified PET base layer (5); Step 2: Print the electrode layer (4) on the modified PET base layer (5) with a metal nanoparticle ink having a surface tension of 26-29 mN / m, and perform a drying treatment to obtain the modified PET base layer (5) with the electrode layer (4); Step 3: Perform electrospinning with a PVA solution of 2-4 g / mL. After the electrospinning is completed, perform a drying treatment to obtain the PVA fiber layer (2). Among them, the syringe for electrospinning is 5 mL, the nominal value of the needle tip diameter is 20G, the ambient humidity is 30-40%RH, the electrospinning voltage is 15-18 kV, the electrospinning time is 3-4 h, and the ambient temperature is 25-30 °C; Step 4: Adhesively bond the PU thin film layer (1), the PVA fiber layer (2), the rubber isolation layer (3), the first PI waterproof layer (7), the electrode layer (4), the modified PET base layer (5), the Cu metal shielding layer (6), and the second PI waterproof layer (8) in sequence, and connect the end of the electrode layer (4) extending outward and one end of the Dupont wire with conductive silver glue.

10. A flexible triboelectric sensor pulse monitoring system based on an intelligent prediction regression network, characterized in that The flexible triboelectric sensor pulse monitoring system based on the intelligent prediction regression network includes the flexible triboelectric sensor as described in any one of claims 1-5, an amplifying and filtering circuit, a control main board, a communication module, a signal processing and analysis module, and a terminal. The flexible triboelectric sensor and the amplifying and filtering circuit are connected in sequence. The control main board is connected to the filtering circuit, the communication module, and the terminal. The signal processing and analysis module is loaded on the terminal; The flexible triboelectric sensor is used to collect user pulse signals including the user's heart rate, blood pressure, augmentation index, and reflection index; The amplifying and filtering circuit is used to amplify the user pulse signal obtained by the flexible triboelectric sensor to obtain an amplified pulse signal, and filter the amplified pulse signal to obtain a filtered pulse signal; The control main board is used to convert the filtered pulse signal in the form of an analog signal into a filtered pulse signal in the form of a digital signal to obtain a digital pulse signal, and send the digital pulse signal to the signal processing and analysis module; The communication module is used to enable the signal processing and analysis module loaded on the terminal to communicate with the control main board to send the digital pulse signal to the signal processing and analysis module; The signal processing and analysis module is used to process and analyze the digital pulse signal to determine the user's cardiovascular information. The signal processing and analysis module includes a physiological information prediction regression network. The physiological information prediction regression network includes six convolutional layers, two fully connected layers, three max pooling layers, and one linear regression layer Linear; The terminal is used to display the user's cardiovascular information.

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