CN112842305B

CN112842305B - Wearable blood pressure measurement system

Info

Publication number: CN112842305B
Application number: CN202110127033.2A
Authority: CN
Inventors: 董瑛; 韩留洋; 潘律名; 王晓浩
Original assignee: Shenzhen International Graduate School of Tsinghua University
Current assignee: Shenzhen International Graduate School of Tsinghua University
Priority date: 2021-01-29
Filing date: 2021-01-29
Publication date: 2023-03-14
Anticipated expiration: 2041-01-29
Also published as: CN112842305A

Abstract

The utility model provides a wearable blood pressure measurement system includes the micropump, the microvalve, the gasbag, baroceptor, pulse sensor and processing apparatus, processing apparatus and micropump, the microvalve, baroceptor and pulse sensor are connected, the micropump, microvalve and baroceptor all communicate the gasbag, pulse sensor fixes on the gasbag, the gasbag is used for wearing at the wrist, baroceptor is used for detecting the atmospheric pressure in the gasbag, the during operation microvalve is closed, processing apparatus control micropump is aerifyd to the gasbag in, pulse sensor is pressed on the wrist by the gasbag after aerifing the inflation, processing apparatus is at the in-process that the atmospheric pressure changes in through micropump and microvalve control gasbag, measure atmospheric pressure through baroceptor, measure the pulse through pulse sensor, and calculate the blood pressure according to atmospheric pressure and the pulse data that record. The measuring system can conveniently and accurately measure the blood pressure, and has wide application prospect in daily monitoring of the blood pressure and home medical care.

Description

Wearable blood pressure measurement system

Technical Field

The invention relates to a wearable blood pressure measuring system.

Background

Blood pressure is one of the most important and commonly used cardiovascular parameters, is used for measuring the pressure of blood on the blood vessel wall, and is widely applied in clinical treatment and home care. It is generally accepted that the normal range of systolic blood pressure (high pressure) is 90 to 140mmHg; the normal range of diastolic pressure (low pressure) is 60 to 90mmHg. The nervous and exciting mental state, unreasonable living and eating habits, the influence of medicines and diseases and other factors can cause abnormal fluctuation of blood pressure. The blood pressure is too low, which means that the heart has insufficient blood pumping capacity and is easy to cause target organ ischemia; and blood vessel rupture can be caused by overhigh blood pressure, and the abnormity of blood fat and blood sugar is caused. Persistent blood pressure abnormalities can also cause complications such as obnubilation, target organ disease, stroke, and myocardial infarction. Therefore, the method has important medical value for measuring the blood pressure.

The current gold standard for blood pressure measurement is the korotkoff sound method, which is also the method most frequently used by doctors. However, the method depends on the judgment of the doctor on the blood flow sound in the process of reducing the cuff pressure, and subjective factors are easily introduced to cause deviation of results; in addition, the accuracy of the measurement method depends heavily on the experience accumulation of long-term measurement, and common people cannot easily judge the change of blood flow sound, so that larger measurement errors are easily caused by using the method. Moreover, the set of device is not wearable or portable, and cannot realize real-time detection of blood pressure. Some commercial digital sphygmomanometers have been developed to enable automatic real-time measurement of blood pressure. However, most of these sphygmomanometers use a piezoresistive silicon-based chip for measuring the pressure of the air to measure the pulse. The pulse causes the air pressure change in the cuff air bag, and then the pressure change is detected by the piezoresistive chip. This process is indirect, and the mechanical vibration of the pulse needs to be converted into a change in air pressure to be detected by the sensor, so that the pressure transmission process is easily interfered by the external environment. There is a need for a wearable device that can stably measure blood pressure.

It is to be noted that the information disclosed in the above background section is only for understanding the background of the present application and thus may include information that does not constitute prior art known to a person of ordinary skill in the art.

Disclosure of Invention

The main object of the present invention is to overcome the above problems in the background art, and to provide a wearable blood pressure measuring system.

In order to achieve the purpose, the invention adopts the following technical scheme:

the utility model provides a wearable blood pressure measurement system, includes micropump, microvalve, gasbag, baroceptor, pulse sensor and processing apparatus, processing apparatus with the micropump, the baroceptor reaches the pulse sensor is connected, the micropump, the microvalve with the baroceptor all communicates the gasbag, the pulse sensor is fixed on the gasbag, the gasbag is used for wearing at the wrist, the baroceptor is used for detecting atmospheric pressure in the gasbag, the during operation the microvalve is closed, processing apparatus control the micropump to aerify in the gasbag, the pulse sensor by aerify after the inflation the gasbag is pressed on the wrist, processing apparatus is passing through the micropump with the microvalve control the in-process of atmospheric pressure change in the gasbag, through the baroceptor measures atmospheric pressure, through the pulse sensor measures the pulse to calculate the blood pressure according to atmospheric pressure and the pulse data that record.

Further, the method comprises the following steps:

the process of controlling the change of the air pressure in the air bag through the micro pump and the micro valve comprises the following steps: in the initial stage, the micro valve is closed, and the air sac is rapidly pressurized by the micro pump until the blood flow is blocked; gradually reducing the air pressure in the air bag through the micro pump and the micro valve until the air pressure in the air bag is reduced to the atmospheric pressure; the processing device measures the air pressure in real time through the air pressure sensor in the process of air pressure reduction, keeps the air pressure at set pressure values for a period of time, completes the measurement of the pulse amplitude through the pulse sensor at the period of time, generates a curve of the pulse amplitude changing along with the air pressure according to the measurement result, and calculates the blood pressure according to the curve of the pulse amplitude changing along with the air pressure.

The processing device determines the pressure value corresponding to the pulse amplitude value of 0.85 times of the maximum value as diastolic pressure, and determines the pressure value corresponding to the pulse amplitude value of 0.55 times of the maximum value as systolic pressure.

The processing device controls to close the micro pump and open the micro valve when the air pressure in the air bag is detected to exceed a safety threshold value and the blood flow is not blocked.

The processing device also compares the calculated blood pressure with a health threshold value of the blood pressure and generates a detection result reflecting the health condition of the blood pressure according to the comparison result.

The pulse sensor is a flexible pressure sensor and comprises a first metal electrode layer, a first electret layer, a second electret layer and a second metal electrode layer which are sequentially laminated together, wherein an air cavity is formed between the first electret layer and the second electret layer, positive and negative charges ionized by air in the air cavity through corona polarization are respectively captured by the first electret layer and the second electret layer to form a charge dipole, the charge dipole and induced charges on the first and second metal electrode layers form electric field balance in an initial state, when the sensor deforms under pressure, dipole moment changes, induced charge transfer forms current on an external circuit, and when pressure is released, the sensor forms reverse current on the external circuit and recovers the electric field balance due to the elastic recovery of the sensor.

The first electret layer and/or the second electret layer have a groove on an inner surface thereof.

The inner surface of the first electret layer is provided with a plurality of first strip-shaped grooves which are parallel to each other, the inner surface of the second electret layer is provided with a plurality of second strip-shaped grooves which are parallel to each other, and the first strip-shaped grooves and the second strip-shaped grooves are opposite to each other and are preferably vertical to each other.

The material of the first electret layer and/or the second electret layer is selected from fluorinated ethylene propylene copolymer (FEP), polypropylene (PP), polyvinylidene fluoride (PVDF); the material of the first metal electrode layer and/or the second metal electrode layer is selected from gold (Au), silver (Ag), copper (Cu), aluminum (Al) and chromium (Cr).

An enclosed air cavity is formed by the first electret layer and the second electret layer together.

Compared with the prior art, the invention has the following beneficial effects:

the invention provides a wearable blood pressure measuring system, which effectively overcomes the defects that the traditional Korotkoff sound auscultation method cannot measure blood pressure in real time, has strong subjective factors and is difficult for common users to accurately measure. Compared with the existing electronic sphygmomanometer, the wearable blood pressure measuring system determines the blood pressure by measuring the pulse and the air pressure by using the air pressure sensor and the pressure sensor to be matched, overcomes the defects that the measurement result of the pressure sensor is unstable and is easily interfered by the environment, directly measures the pulse beat by fixing the pulse sensor on the air bag, avoids the defects of poor stability and easy interference by the environment in indirect measurement modes such as a piezoresistive chip and the like, and can conveniently and accurately measure the blood pressure. The wearable blood pressure measuring system has wide application prospect in daily monitoring of blood pressure and home medical care. The blood pressure measuring system provided by the invention is also suitable for being combined to wearable equipment such as a watchband, a bracelet structure or a manual pressurizing structure.

The flexible pressure sensor provided by the preferred embodiment has the capability of stably storing electric charges for a long time, so that the sensor can be used for a long time without performance attenuation, namely, the sensor has excellent stability and can stably measure weak pressure signals such as pulse for a long time. In addition, the sensor has high sensitivity, and can measure a pulse in a small area, which is also advantageous for measuring a fingertip pulse and a vein pulse. The sensor disclosed by the invention can be very light and thin, has good flexibility, can be well contacted with the surface of the skin to obtain a clearer pulse signal, has the advantages of light and thin property, flexibility, high precision and good stability, and cannot cause discomfort to a user when being worn for a long time. The sensor is convenient to manufacture a plurality of sensors simultaneously, and the requirements of practical application on mass production and rapid manufacturing and forming are met.

Drawings

Fig. 1 is a schematic structural diagram of a wearable blood pressure measurement system according to an embodiment of the present invention.

Fig. 2 is a schematic diagram illustrating the operation of the wearable blood pressure measurement system of the embodiment of the invention at the wrist.

Fig. 3 is a flowchart of the blood pressure measurement according to the embodiment of the present invention.

Fig. 4 shows the variation of the air pressure (static pressure) in the cuff and the corresponding pulse amplitude with the working time according to the embodiment of the invention.

FIG. 5 is a schematic diagram of an exemplary pulse amplitude-static pressure curve and oscillometric blood pressure calculation according to an embodiment of the present invention.

FIG. 6 is a flowchart of an algorithm for calculating blood pressure from pulse data according to an embodiment of the present invention.

FIG. 7 is a flow chart of a sensor fabrication process according to an embodiment of the present invention.

Fig. 8a is a schematic structural diagram of a sensor according to an embodiment of the present invention.

Fig. 8b is a cross-sectional view of the sensor of fig. 8a taken along line I-I.

Fig. 8c is an exploded view of the sensor shown in fig. 8 a.

Fig. 9 illustrates the operation of the sensor according to an embodiment of the present invention.

Detailed Description

The embodiments of the present invention will be described in detail below. It should be emphasized that the following description is merely exemplary in nature and is not intended to limit the scope of the invention or its application.

It will be understood that when an element is referred to as being "secured to" or "disposed on" another element, it can be directly on the other element or be indirectly on the other element. When an element is referred to as being "connected to" another element, it can be directly connected to the other element or be indirectly connected to the other element. In addition, the connection can be for fixation or for coupling or communication.

It is to be understood that the terms "length," "width," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," and the like are used in an orientation or positional relationship indicated in the drawings for convenience in describing the embodiments of the present invention and to simplify the description, and are not intended to indicate or imply that the referenced device or element must have a particular orientation, be constructed in a particular orientation, and be in any way limiting of the present invention.

Furthermore, the terms "first", "second" and "first" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of the embodiments of the present invention, "a plurality" means two or more unless specifically limited otherwise.

Referring to fig. 1 to 6, in an embodiment, a wearable blood pressure measuring system includes a micro pump, a micro valve, an air bag, an air pressure sensor, a pulse sensor, and a processing device, the processing device is connected to the micro pump, the air pressure sensor, and the pulse sensor, the micro pump, the micro valve, and the air pressure sensor are all connected to the air bag, the pulse sensor is fixed to the air bag, the air bag is used for being worn on a wrist, the air pressure sensor is used for detecting air pressure in the air bag, the micro valve is closed during operation, the processing device controls the micro pump to inflate the air bag, the pulse sensor is pressed on the wrist by the inflated air bag, the processing device measures air pressure through the air pressure sensor during the process of controlling the air pressure change in the air bag through the micro pump and the micro valve, measures pulse through the pulse sensor, and calculates blood pressure according to the measured air pressure and pulse data. The air pressure sensor is communicated with the air bag, can be communicated with the air bag through a pipeline, and can also be arranged in the air bag. The processing means may be a circuit means having a microprocessor as a core.

In a preferred embodiment, the process of controlling the change of the air pressure in the balloon by the micro pump and the micro valve comprises: in the initial stage, the micro valve is closed, and the air sac is rapidly pressurized by the micro pump until the blood flow is blocked; gradually reducing the air pressure in the air bag through the micro pump and the micro valve until the air pressure in the air bag is reduced to the atmospheric pressure; the processing device measures the air pressure in real time through the air pressure sensor in the process of air pressure reduction, keeps the air pressure at set pressure values for a period of time, completes measurement of the pulse amplitude through the pulse sensor at the period of time, generates a curve of the pulse amplitude changing along with the air pressure according to the measurement result, and calculates the blood pressure according to the curve of the pulse amplitude changing along with the air pressure.

The processing device determines the pressure value corresponding to the pulse amplitude value which is 0.85 times of the maximum value as the diastolic pressure, and determines the pressure value corresponding to the pulse amplitude value which is 0.55 times of the maximum value as the systolic pressure.

The processing device may implement the control and processing procedures described above by means of a computer program stored in a computer-readable storage medium.

The embodiment of the invention provides a wearable blood pressure measuring system, which effectively overcomes the defects that the traditional Korotkoff sound auscultation method cannot measure blood pressure in real time, has strong subjective factors and is difficult for common users to accurately measure. Compared with the existing electronic sphygmomanometer, the wearable blood pressure measuring system determines the blood pressure by measuring the pulse and the air pressure by using the air pressure sensor and the pressure sensor to be matched, overcomes the defects that the measurement result of the pressure sensor is unstable and is easily interfered by the environment, directly measures the pulse beat by fixing the pulse sensor on the air bag, avoids the defects of poor stability and easy interference by the environment in indirect measurement modes such as a piezoresistive chip and the like, and can conveniently and accurately measure the blood pressure. The wearable blood pressure measuring system has wide application prospect in daily monitoring of blood pressure and home medical care. The blood pressure measuring system provided by the invention is also suitable for being combined to wearable equipment such as a watchband, a bracelet structure or a manual pressurizing structure.

In a preferred embodiment, the pressure sensor is a flexible pressure sensor.

Referring to fig. 7 to 9, the flexible pressure sensor of the preferred embodiment includes a first metal electrode layer 101, a first electret layer 102, a second electret layer 103, and a second metal electrode layer 104, which are sequentially laminated together, an air cavity 105 is provided between the first electret layer 102 and the second electret layer 103, positive and negative charges ionized by corona polarization of air in the air cavity 105 are respectively captured by the first electret layer 102 and the second electret layer 103 to form a charge dipole, the charge dipole forms an electric field balance with induced charges on the first metal electrode layer 101 and the second metal electrode layer 104 in an initial state, when the sensor is deformed by pressure, a dipole moment changes, the induced charges transfer to form a current on an external circuit, and when the pressure is released, the sensor forms a reverse current on the external circuit due to its elastic recovery and restores the electric field balance.

In a preferred embodiment, the first electret layer 102 and/or the second electret layer 103 have grooves on their inner surfaces. The groove pattern can be a periodic line groove pattern, a triangular pyramid groove pattern, a rectangular parallelepiped groove pattern, or the like, or a non-periodic, irregular groove pattern.

In a particularly preferred embodiment, the first electret layer 102 has a plurality of first strip-shaped grooves on its inner surface parallel to each other, and the second electret layer 103 has a plurality of second strip-shaped grooves on its inner surface parallel to each other, the first and second strip-shaped grooves being opposite to each other, and preferably also perpendicular to each other.

In various embodiments, the material of the first electret layer 102 and/or the second electret layer 103 may be selected from fluorinated ethylene propylene copolymer (FEP), polypropylene (PP), polyvinylidene fluoride (PVDF).

In various embodiments, the material of the first metal electrode layer 101 and/or the second metal electrode layer 104 may be selected from gold (Au), silver (Ag), copper (Cu), aluminum (Al), chromium (Cr).

In various embodiments, the first metal electrode layer 101 and/or the second metal electrode layer 104 may be formed by metal plating (such as metal vapor deposition), screen printing, or metal tape bonding.

In a preferred embodiment, an enclosed air cavity 105 is formed by the first electret layer 102 and the second electret layer 103 together.

Referring to fig. 7 to 9, in another embodiment, a method for manufacturing the high-sensitivity flexible pressure sensor includes the following steps:

manufacturing a first electret layer 102 and a second electret layer 103, and oppositely bonding the first electret layer 102 and the second electret layer 103 together, wherein an air cavity 105 is formed between the first electret layer 102 and the second electret layer 103;

forming a first metal electrode layer 101 on an outer surface of the first electret layer 102, and forming a second metal electrode layer 104 on an outer surface of the second electret layer 103;

wherein positive and negative charges ionized by corona polarization of the air in the air cavity 105 are respectively trapped by the first electret layer 102 and the second electret layer 103 to form a charge dipole.

In a preferred embodiment, said fabricating the first electret layer 102 and the second electret layer 103 comprises: grooves are formed on the opposing surfaces of the first electret layer 102 and/or the second electret layer 103 by laser engraving.

In various embodiments, the first electret layer 102 and the second electret layer 103 may be bonded by thermocompression bonding, chemical bonding, or glue bonding.

Specific embodiments of the present invention are further described below by way of examples.

Fig. 1 shows a specific structural schematic diagram of the measurement system. The system uses a watchband type wearable structure, and the wearable structure is automatically pressurized through a pump valve device; in fact, the blood pressure measuring system proposed by the present invention is also applicable to a bracelet structure, a manual pressurizing structure, or the like, and here, a band structure capable of automatically pressurizing is preferable. The pulse sensor 6 is fixed on the air bag cuff 5 to directly measure the pulse so as to avoid the defects of poor stability and easy environmental interference in indirect measurement modes such as the piezoresistive chip and the like.

Other functional components are concentrated in the case 4 and can be divided into a circuit part 1 and an air circuit part 2. The circuit part comprises a circuit for amplifying and filtering the output signal of the pulse sensor, a circuit for realizing the control of the pump valve and a microprocessor for realizing the functions of data sampling, storage, analysis and calculation and the like. The air circuit part comprises a micropump, a microvalve and an air pressure sensor, and realizes automatic application and control of pressure, wherein the air pressure sensor feeds an air pressure value back to the microprocessor in real time, and the microprocessor controls the opening and closing of the pump and the valve, so that the air pressure in the air bag cuff is controlled and adjusted through the air duct 3. The algorithm part is completed in the microprocessor, and is mainly used for processing and analyzing the sampled pulse data, calculating the blood pressure value and sending the result to a display screen or wirelessly sending the result to terminals such as a mobile phone, a computer and the like; if the blood pressure value exceeds the preset health threshold value, the device also sends out an abnormal early warning.

Fig. 2 shows a schematic diagram of the operation of the wearable device to perform blood pressure measurement at the wrist. The pressurizing air bag sleeve belt 5 is fixed on the periphery of the wrist through a magic tape 7. In fact, the fixing of the watchband can also be realized here by a button structure, a pin structure, a slot structure or a magnet attraction structure.

Fig. 3 shows a flow chart of the operation of the device. At the beginning, the microvalve is closed and the balloon cuff is rapidly pressurized by the micropump until blood flow is blocked. At this time, the air pressure in the air bag is high, which is dangerous for the elderly, infants or people with fragile blood vessels, so a safety threshold should be set. If the air pressure in the air bag exceeds a safety threshold value and the blood flow is not blocked, the micro pump is immediately closed, the continuous pressurization is stopped, and the micro valve is opened to quickly discharge the air. And warning about improper use is given on the display screen to prompt the user to wear the clothes correctly. If the situation that the blood flow is not blocked under the safety threshold value still occurs after the wearing posture is adjusted for many times, the reason is probably that the blood pressure of the user is high, and the device can give out a hypertension early warning.

If the blood flow is blocked before the safety threshold, the device will perform the normal measurement procedure. At the moment, the air pressure in the cuff is gradually reduced through the pump, the valve and the air pressure sensor, and the air pressure is kept for a period of time at certain pressure values to finish the measurement of the pulse. And simultaneously recording the air pressure value and the corresponding pulse until the air pressure in the cuff is reduced to normal atmospheric pressure. And drawing a pulse amplitude-air pressure curve for calculating a blood pressure result. Comparing the result with the health value of the blood pressure value, and if the result does not exceed the health range, displaying the blood pressure result on a display screen in real time or wirelessly transmitting the blood pressure result; if the health range is exceeded, the device can timely send out abnormal early warning.

Fig. 4 shows the variation of the air pressure (static pressure) in the air bag cuff and the corresponding pulse amplitude value with the working time in the whole working time. Measuring the real-time pulse in the pressure reduction stage; through the cooperation of the pump, the valve and the air pressure sensor, a certain pressure value is kept for a certain time to measure the pulse. Calculating the pulse amplitude, and drawing a curve of the pulse amplitude and the static pressure so as to calculate the blood pressure value through the principle of the oscillography.

Fig. 5 shows an exemplary curve of pulse amplitude versus static pressure and a schematic illustration of calculating blood pressure values by oscillography. The pressure in the cuff is high at the beginning, the normal flow of blood is blocked, and the pulse amplitude is small at the moment. With the decrease of the air pressure, the blood flow gradually returns to normal, and the pulse amplitude gradually increases. When the pressure value in the cuff is reduced to the Mean Arterial Pressure (MAP) in the blood vessel, the pressure inside and outside the blood vessel is balanced, and the pulse amplitude reaches the maximum value, namely the Am point in figure 5. After that, the air pressure value is continuously reduced, and the pulse amplitude value is reduced. In the present invention, the blood pressure value is calculated by using an oscillometric method, and a smaller pressure value corresponding to 0.85 with the highest pulse amplitude is considered As the diastolic pressure (low pressure, ad/Am = 0.85), and a larger pressure value corresponding to 0.55 with the highest pulse amplitude is considered As the systolic pressure (high pressure, as/Am = 0.55).

Fig. 6 shows a flow chart of an algorithm for calculating blood pressure by sampling the obtained pulse data, which is implemented in a microprocessor, and is a detailed explanation of the "algorithm part" in fig. 1. And performing pre-processing such as baseline removal, low-pass filtering and the like on the recorded pulse data to acquire smooth and stable pulse data. The pulse has strong periodic rule, and the peak and the trough in each pulse period are extracted through a preset amplitude threshold value and a preset time threshold value so as to calculate the amplitude of the pulse. On the other hand, the microprocessor reads the air pressure value in the air bag fed back by the air pressure sensor, draws a curve of static pressure and pulse amplitude, and calculates the blood pressure result by the method shown in fig. 5. The result is compared with a health threshold and then displayed in real time, wirelessly transmitted, or an abnormal warning is issued.

Flexible pressure sensor

Flexible pressure sensors are preferably employed in the wearable blood pressure measurement system. Referring to fig. 7 to 9, in the flexible pressure sensor according to the preferred embodiment of the present invention, an air cavity 105 is provided between the first electret layer 102 and the second electret layer 103, and air in the air cavity 105 is corona-polarized to ionize positive and negative charges, which are respectively captured by the first electret layer 102 and the second electret layer 103 to form a charge dipole, in an initial state, the charge dipole forms an electric field balance with induced charges on the metal electrode layers 101 and 104, when the sensor is deformed under pressure, a dipole moment changes, the induced charges are transferred to form a current on an external circuit, and when the pressure is released, the sensor elastically restores to its original state, forms a reverse current on the external circuit and restores the electric field balance, thereby the flexible pressure sensor can sense pulses of pulses and output corresponding currents to achieve pulse measurement.

Since the electret material has the ability to stably store electric charges, this allows the sensor to be used for a long period without deterioration in performance, i.e., has excellent stability, and can stably measure a pulse for a long period of time. In addition, the sensor has high sensitivity and can measure a pulse in a small area, which is very advantageous for measuring a fingertip pulse and a vein pulse. The sensor provided by the embodiment of the invention can be very light and thin (50-100 mu m), has good flexibility, can be in good contact with the surface of the skin to obtain a clearer pulse signal, and does not cause discomfort to a user when being worn for a long time. A plurality of sensors can be manufactured simultaneously, and the requirements of practical application on mass production and rapid manufacturing and forming are met. The flexible pressure sensor provided by the embodiment of the invention has wide application prospects in the fields of pulse and other physiological signal measurement, electronic skin, human-computer interaction interfaces and the like.

In one embodiment, the flexible piezoelectric electret sensor is fabricated based on laser engraving and thermocompression bonding processes. Two electret films (FEP films are used as an example) are laser-cut with line grooves, the line grooves on the two FEP films are placed perpendicular to each other, and thermally compression-bonded to form closed air cavities. After a metal electrode is evaporated on one side of the sensor, the sensor is charged in a corona mode through a high-voltage power supply, and finally a metal adhesive tape is attached to the other side of the sensor to serve as an electrode on the other side. In an alternative embodiment, the metal electrode subjected to vapor deposition can be replaced by an attached metal tape, so that the cost can be further reduced, the manufacturing period can be shortened, and the robustness of the sensor in long-term use can be improved.

FIG. 7 illustrates an example of a sensor fabrication flow. 101 denotes a first metal electrode layer; 102 denotes a first electret layer; 103 denotes a second electret layer; and 104 a second metal electrode layer. The material of the electret film used may be fluorinated ethylene propylene copolymer (FEP), polypropylene (PP), polyvinylidene fluoride (PVDF), etc., and here, FEP film is preferable; the metal electrode used may be gold (Au), silver (Ag), copper (Cu), aluminum (Al), chromium (Cr), or the like, and is preferably a Cu electrode. In order to achieve a flexible effect, the thickness of the electret film may be 10 to 100 μm, here preferably 25 μm; the thickness of the metal electrode is 0.1 μm to 10 μm, preferably 10 μm.

Since the electret film is thin, it is placed on a hard substrate in order to make the film flat and convenient for further processing. The selected hard substrate is flat and smooth, the surface energy is low, and the electret film can be torn off smoothly after subsequent treatment. The material of the hard substrate may be a copper plate, preferably 1mm thick. The electret film was laid flat on a hard substrate and wiped several times with a soft paper to remove dust from the electret film and make the electret film adhere to the hard substrate. A groove pattern is then engraved on the electret film. The engraving method used may be manual engraving, laser engraving, chemical agent etching based on a mask (e.g. a photolithography process, a screen mold, etc.), etc., where a laser engraving process is preferred. The groove patterns can be periodic line groove patterns, triangular pyramid groove patterns, rectangular parallelepiped groove patterns and the like, or non-periodic and irregular groove patterns. A line groove pattern is preferred here. Preferably, the depth of the grooves is as deep as possible without punching through the electret film.

Such groove delineation is performed on the two

electret films

102, 103, respectively. Line grooves are preferred here, and are made perpendicular to one another on both films. Such two films are then placed against each other so that they bond together to form a closed air cavity. The bonding method used may be thermocompression bonding, chemical agent bonding, glue bonding, etc., and thermocompression bonding is preferable here. For the preferred FEP electret material, the parameters for thermal compression bonding are thermal compression for 90s at a pressure of 1MPa and a temperature of 250 ℃. After hot pressing, the two electret films form an integral body which can not be divided, and the groove patterns form a sealed air cavity.

A metal electrode layer 101 is then provided on one side of the electret film. The setting mode can be metal coating, screen printing, metal tape bonding and the like. A thinner metal layer can be obtained by metal coating and screen printing so as to obtain better flexible effect; they are expensive and time consuming. The metal tape bonding method is preferred here. Corona polarization was then performed using a dc high voltage power supply, a corona pin and a ground electrode. A specific embodiment is to place the metal electrode layer 101 on the ground electrode and a corona needle above the other side of the sensor (e.g. 3 cm). And applying negative high voltage (18 to 30 kV) to the corona needle to perform corona charging for 2 to 5min. Finally, a metal electrode layer 104 is disposed on the other side of the electret film to complete the fabrication of the sensor. The arrangement mode can still be metal coating, screen printing, metal tape bonding and the like. Still preferred here is the manner of metal tape bonding.

Fig. 8a and 8b show the complete structure and the cross section along the line I-I of the sensor, respectively. Fig. 8c shows an exploded schematic view of the sensor. Fig. 9 shows the working principle of the sensor. During high voltage corona polarization, the air within the sealed cavity 105 will be broken down, ionizing equal amounts of positive and negative charges. Then, under the action of the electric field, the positive and negative charges move to the upper and lower sides respectively, and are finally captured by the inner walls of the

electret films

102 and 103, so that a large number of charge dipoles are formed. In the initial state (fig. 9 (1)), the charge dipoles trapped on the trench walls of the electret film form an electric field equilibrium with the induced charges on the metal electrodes, with no electrical response. When the sensor is compressively deformed by sensing an external pressure ((2) in fig. 9), the dipole moment is changed, the electric field balance is broken, and the induced charge on the metal electrode is transferred to form a current on an external circuit. When the pressure is released, the sensor elastically recovers itself, and an opposite current is generated in the external circuit ((3) in fig. 9). Therefore, the flexible pressure sensor can sense the pulse of the pulse, output corresponding current and realize the measurement of the pulse.

This sensor continues to operate for years due to the ability of electret materials to stably store charge. In addition, the output property of the sensor is similar to that of a piezoelectric sensor, the sensor also has the characteristic of self-driving, an external power supply is not needed during working, and the effect of low power consumption is achieved. In addition, in the provided manufacturing process flow, laser cutting, hot-press bonding, corona polarization and metal tape pasting are very simple low-cost processes, so that the rapid manufacturing and forming are facilitated, and the cost is reduced. In addition, in these processes, multiple sensors can be made simultaneously in the same batch, which facilitates mass production of the sensors; or the sensors with different sizes are produced in the same batch, so that the size can be conveniently adjusted.

The background section of the present invention may contain background information related to the problem or environment of the present invention and does not necessarily describe prior art. Accordingly, the inclusion in this background section is not an admission by the applicant that prior art is available.

The foregoing is a further detailed description of the invention in connection with specific/preferred embodiments and it is not intended to limit the invention to the specific embodiments described. It will be apparent to those skilled in the art that numerous alterations and modifications can be made to the described embodiments without departing from the inventive concepts herein, and such alterations and modifications are to be considered as within the scope of the invention. In the description herein, references to the description of the term "one embodiment," "some embodiments," "preferred embodiments," "an example," "a specific example," or "some examples" or the like are intended to mean that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the invention. In this specification, the schematic representations of the terms used above are not necessarily intended to refer to the same embodiment or example. Furthermore, the particular features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples. Those skilled in the art will be able to combine and combine features of different embodiments or examples and features of different embodiments or examples described in this specification without contradiction. Although embodiments of the present invention and their advantages have been described in detail, it should be understood that various changes, substitutions and alterations can be made herein without departing from the scope of the claims.

Claims

1. A wearable blood pressure measuring system comprising a micro pump, a micro valve, a balloon, a pressure sensor, a pulse sensor and a processing device, wherein the processing device is connected to the micro pump, the micro valve, the pressure sensor and the pulse sensor, the micro pump, the micro valve and the pressure sensor are all communicated with the balloon, the pulse sensor is fixed on the balloon, the balloon is used for being worn on a wrist, the pressure sensor is used for detecting the pressure of the air in the balloon, the micro valve is closed during operation, the processing device controls the micro pump to inflate the balloon, the pulse sensor is pressed on the wrist by the balloon after inflation and inflation, the processing device measures the pressure of the air in the balloon through the pressure sensor during the process of controlling the pressure change in the balloon through the micro pump and the micro valve, measures the pulse through the pulse sensor, calculates the blood pressure according to the measured pressure and pulse data, wherein the processing device simultaneously detects the conditions of the blockage of the pressure and the blockage of the air in the balloon, if the pressure in the balloon is detected to reach a safety threshold, the processing device detects that the blood flow is blocked, and controls the wearing of the balloon to open the micro valve to give a warning that the blood flow is not correctly when the blood flow blocking screen is detected, and the blood flow is not detected, and the user can give a warning that the blood flow is not blocked; the pulse sensor is a flexible pressure sensor and comprises a first metal electrode layer, a first electret layer, a second electret layer and a second metal electrode layer which are sequentially laminated together, an air cavity is formed between the first electret layer and the second electret layer, positive and negative charges ionized by air in the air cavity through corona polarization are respectively captured by the first electret layer and the second electret layer to form a charge dipole, the charge dipole and induced charges on the first metal electrode layer and the second metal electrode layer form electric field balance in an initial state, when the sensor is deformed under pressure, dipole moment is changed, the induced charges are transferred to form current on an external circuit, when pressure is released, the sensor restores the original state due to elasticity of the sensor, opposite current is formed on the external circuit and the electric field balance is restored, a plurality of first strip-shaped grooves which are parallel to each other are formed on the inner surface of the first electret layer, a plurality of second strip-shaped grooves which are parallel to each other are formed on the inner surface of the second electret layer, the first strip-shaped grooves and the second strip-shaped grooves are opposite to each other and perpendicular to each other, and a cross-shaped groove structure based on the grooves is formed.

2. The wearable blood pressure measurement system of claim 1 wherein the process of controlling the change in air pressure within the bladder via the micro pump and the micro valve comprises: in the initial stage, the micro valve is closed, and the air sac is rapidly pressurized by the micro pump until the blood flow is blocked; gradually reducing the air pressure in the air bag through the micro pump and the micro valve until the air pressure in the air bag is reduced to the atmospheric pressure; the processing device measures the air pressure in real time through the air pressure sensor in the process of air pressure reduction, keeps the air pressure at set pressure values for a period of time, completes the measurement of the pulse amplitude through the pulse sensor at the period of time, generates a curve of the pulse amplitude changing along with the air pressure according to the measurement result, and calculates the blood pressure according to the curve of the pulse amplitude changing along with the air pressure.

3. The wearable blood pressure measurement system of claim 2 wherein the processing device determines a pressure value corresponding to a pulse magnitude of 0.85 times the maximum value as the diastolic pressure and determines a pressure value corresponding to a pulse magnitude of 0.55 times the maximum value as the systolic pressure.

4. The wearable blood pressure measurement system of any of claims 1-3 wherein the processing device further compares the calculated blood pressure to a health threshold for the blood pressure and generates a test result reflecting the health of the blood pressure based on the comparison.

5. The wearable blood pressure measurement system of any of claims 1 to 3 wherein the material of the first electret layer and/or the second electret layer is selected from fluorinated ethylene propylene copolymer (FEP), polypropylene (PP), polyvinylidene fluoride (PVDF); the material of the first metal electrode layer and/or the second metal electrode layer is selected from gold (Au), silver (Ag), copper (Cu), aluminum (Al) and chromium (Cr).

6. The wearable blood pressure measurement system of any of claims 1-3 wherein the first electret layer and the second electret layer together form an enclosed air cavity.