A piezoelectric thin film-based heart and pulse sensor and a method of manufacturing the same

Abstract

The application provides a heart and pulse sensor based on a piezoelectric film and a preparation method thereof, which comprises a sensing element (2) which is a poly-L-lactic acid film or a poly-D-lactic acid film, and upper and lower surfaces of the sensing element (2) are respectively provided with an upper electrode (1) and a lower electrode (3); a metal shell (7) which covers the lower electrode (3) and forms a cavity (6) between the lower electrode (3) and the metal shell (7); an insulating pad (5) which is arranged on a contact part of the metal shell (7) and the lower electrode (3); and a metal pressing ring (4) which is arranged on an edge of the sensing element (2) and fixes the sensing element (2) on the metal shell (7), so that when the heart sensor is subjected to the pressure of heartbeat, the poly-L-lactic acid film or the poly-D-lactic acid film as a detection element converts the heart sound signal into an electric signal and outputs the electric signal, and meanwhile, the interference of a temperature signal can be shielded. The piezoelectric material of the application is renewable and has good biocompatibility, can accurately reflect the vital signs and health information of a detected person, and avoids the harm and limitation to the human body.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of biosensors, in particular to a heart and pulse sensor based on piezoelectric film and a preparation method thereof. BACKGROUND

[0002] Heart sound is a reflection of the mechanical movement of the heart and cardiovascular system, which contains physiological and pathological information of each part of the heart itself and the interaction between them. The identification and classification of heart sound signals are of great significance for the diagnosis of cardiovascular diseases, and the accuracy and reliability determine the effect of diagnosing and treating heart disease patients. The stethoscope used for heart sound identification and classification in the early stage mainly consists of a sound pickup part, a transmission part and a sound listening part. The sound signals collected need to be analyzed by professional doctors with rich experience. Due to the influence of ambient noise, doctors are prone to misdiagnosis when diagnosing, and non-professionals cannot use it.

[0003] With the efforts of scientists in various countries, air conduction and contact conduction sensors have become common heart sound sensors on the market. Air conduction sensors use electromagnetic coils as acoustic-electric transducers, which have good stability but low sensitivity and are easily affected by external electromagnetic fields. The detection elements of contact conduction sensors are mostly made of polyvinylidene fluoride (PVDF). The advantage of this kind of sensor is high sensitivity, but the output is unstable and easily disturbed by temperature signals (PVDF has pyroelectricity).

[0004] Therefore, there is an urgent need for a wearable auscultation device with high accuracy, simple use, low cost, small size, real-time display, which allows clinicians to see the corresponding signal waveform graph and record while listening to the heart, so as to make more accurate analysis of the patient's pathology. SUMMARY

[0005] (I) Technical problems to be solved

[0006] In view of the above problems, the present application provides a heart and pulse sensor based on piezoelectric film and a preparation method thereof, which at least partially solves the technical problems that traditional sensors are easily affected by body temperature signals, environmental electromagnetic field noise and the like when detecting heart sound.

[0007] (II) Technical solutions

[0008] The heart sensor based on piezoelectric film comprises a sensing element 2, which is a poly-L-lactic acid film or a poly-D-lactic acid film, and upper and lower surfaces of the sensing element 2 are respectively provided with an upper electrode 1 and a lower electrode 3; a metal shell 7, which covers the lower electrode 3 and forms a cavity 6 between the lower electrode 3 and the metal shell 7; an insulating pad 5, which is arranged on a contact part of the metal shell 7 and the lower electrode 3; and a metal compression ring 4, which is arranged at an edge of the sensing element 2 and fixes the sensing element 2 on the metal shell 7, so that when the heart sensor is subjected to the pressure of heartbeat, the poly-L-lactic acid film or the poly-D-lactic acid film as a detection element converts the heart sound signal into an electric signal and outputs the electric signal, and meanwhile, the poly-L-lactic acid film or the poly-D-lactic acid film can shield the interference of the temperature signal.

[0009] Further, the heart sensor further comprises a terminal post 8, which is arranged on a side surface of the metal shell 7, and a positive electrode of the terminal post 8 is connected with the lower electrode 3 through a wire penetrating through the cavity 6, and a negative electrode of the terminal post 8 is connected with the upper electrode 1 through the metal shell 7.

[0010] Further, the heart sensor further comprises a screw rod 9, which penetrates through the metal compression ring 4, the sensing element 2 and the metal shell 7 in sequence to fix them.

[0011] Further, the insulating pad 5 is a ring structure with a middle protrusion, and an interface of the insulating pad 5 is L-shaped.

[0012] Further, the sensing element 2 is a thin film structure with at least one layer.

[0013] The pulse sensor based on piezoelectric film comprises at least one sensing element 12, which is a poly-L-lactic acid film or a poly-D-lactic acid film, and upper and lower surfaces of the sensing element 12 are respectively provided with an upper electrode 11 and a lower electrode 13; a flexible substrate 15, which covers the lower electrode 13 of each sensing element 12 and forms a cavity 14 between the lower electrode 13 and the flexible substrate 15; each lower electrode 13 is connected with a positive electrode of a terminal post 16 through an inside of the flexible substrate 15, and the upper electrode 11 is connected with a shell of the terminal post 16 through a metal electrode covering a whole surface of the device; and the pulse sensor is wearable, so that when the pulse sensor is subjected to the pressure of pulse, the poly-L-lactic acid film or the poly-D-lactic acid film as a detection element converts the pulse signal into an electric signal and outputs the electric signal, and meanwhile, the poly-L-lactic acid film or the poly-D-lactic acid film can shield the interference of the temperature signal.

[0014] Further, the sensing element 12 is a thin film structure with at least one layer.

[0015] The application further provides a preparation method of the heart sensor based on the piezoelectric film, comprising the following steps: S21, preparing a sensing element 2 film by solution casting, which is a poly-L-lactic acid film or a poly-D-lactic acid film; S22, sputtering an upper electrode 1 and a lower electrode 3 on the upper and lower surfaces of the sensing element 2 film respectively; S23, covering the lower electrode 3 with a metal shell 7 to form a cavity 6 therebetween, and fixing the metal shell 7 with an insulating pad 5, the sensing element 2 and a metal compression ring 4 in sequence; when the heart sensor is subjected to the pressure of heartbeat, the poly-L-lactic acid film or the poly-D-lactic acid film as the detection element converts the heart sound signal into an electric signal and outputs, and meanwhile can shield the interference of the temperature signal.

[0016] Further, after S3, the method further comprises installing a terminal post 8 in a through hole reserved on the side of the metal shell 7, and the positive electrode of the terminal post 8 is connected with the lower electrode 3 through a wire penetrating through the cavity 6, and the negative electrode is connected with the upper electrode 1 through the metal shell 7.

[0017] The application further provides a preparation method of the pulse sensor based on the piezoelectric film, comprising the following steps: S21, preparing at least one sensing element 12 film by solution casting, which is a poly-L-lactic acid film or a poly-D-lactic acid film; S22, sputtering an upper electrode 11 and a lower electrode 13 on the upper and lower surfaces of the sensing element 12 film respectively; S23, covering the lower electrode 13 of each sensing element 12 with a flexible substrate 15 to form a cavity 14 therebetween; each lower electrode 13 is connected with the positive electrode of a terminal post 16 through the inside of the flexible substrate 14, and the upper electrode 11 is connected with the shell of the terminal post 16 through a metal electrode coated on the surface of the whole device; the pulse sensor is wearable, when subjected to the pressure of pulse, the poly-L-lactic acid film or the poly-D-lactic acid film as the detection element converts the pulse signal into an electric signal and outputs, and meanwhile can shield the interference of the temperature signal.

[0018] (III) Beneficial Effects

[0019] The heart and pulse sensors based on the piezoelectric film and the preparation methods thereof provided by the application can convert the heart sound signal into an electric signal through the poly-L-lactic acid film or the poly-D-lactic acid film as the detection element, fundamentally avoid the defect that the traditional sensor is easily affected by the body temperature signal when detecting the heart sound, and adopt the renewable biocompatible material to avoid the harm to the human body and the limitation; and the reasonable electrode structure design avoids the noise of the environmental electromagnetic field. BRIEF DESCRIPTION OF DRAWINGS

[0020] Figure 1 Fig. 1 schematically shows the structure of the heart sensor based on the piezoelectric film according to the embodiment of the application;

[0021] Figure 2A physical diagram of a heart sensor based on a piezoelectric film according to an embodiment of the present application is shown schematically;

[0022] Figure 3 A structure diagram of an insulating pad in a heart sensor based on a piezoelectric film according to an embodiment of the present application is shown schematically;

[0023] Figure 4 A structure diagram of a pulse sensor based on a piezoelectric film according to an embodiment of the present application is shown schematically;

[0024] Figure 5 A physical diagram of a pulse sensor based on a piezoelectric film according to an embodiment of the present application is shown schematically;

[0025] Figure 6 A flowchart of a preparation method of a heart sensor based on a piezoelectric film according to an embodiment of the present application is shown schematically;

[0026] Figure 7 A flowchart of a preparation method of a pulse sensor based on a piezoelectric film according to an embodiment of the present application is shown schematically;

[0027] Figure 8 A filtered heart rhythm data diagram of a heart sensor based on a piezoelectric film according to an embodiment of the present application is shown schematically;

[0028] Figure 9 A direct output diagram of heart rhythm data of a heart sensor based on a piezoelectric film according to an embodiment of the present application is shown schematically;

[0029] Figure 10 A heart rate signal change in a heart rate cycle according to an embodiment of the present application is shown schematically;

[0030] Figure 11 A filtered pulse data diagram of a pulse sensor based on a piezoelectric film according to an embodiment of the present application is shown schematically;

[0031] Figure 12 A direct output diagram of pulse data of a pulse sensor based on a piezoelectric film according to an embodiment of the present application is shown schematically;

[0032] Figure 13 A test result of a PLLA piezoelectric coefficient d 14 according to an embodiment of the present application is shown schematically.

[0033] DETAILED DESCRIPTION

[0034] In order to make the objectives, technical solutions, and advantages of the present application clearer, the present application is further described in detail below with reference to specific embodiments and drawings.

[0035] The embodiment of the present application provides a heart sensor based on a piezoelectric film, which comprises a sensing element 2, which is a poly-L-lactic acid film or a poly-D-lactic acid film, and upper and lower surfaces of the sensing element 2 are respectively provided with an upper electrode 1 and a lower electrode 3; a metal shell 7, which covers the lower electrode 3 and forms a cavity 6 between the lower electrode 3 and the metal shell 7; an insulating pad 5, which is arranged on a contact part of the metal shell 7 and the lower electrode 3; and a metal compression ring 4, which is arranged at an edge of the sensing element 2 and fixes the sensing element 2 on the metal shell 7, so that when the heart sensor is subjected to the pressure of heartbeat, the poly-L-lactic acid film or the poly-D-lactic acid film as a detection element converts the heart sound signal into an electric signal and outputs the electric signal, and meanwhile, the heart sensor can shield the interference of the temperature signal. Figure 1

[0036] The biosensor comprises a poly-L-lactic acid (PLLA) film or a poly-D-lactic acid (PDLA) film with an electrode, a metal compression ring, an insulating pad and a metal shell with a cavity. The degradable poly-L-lactic acid film or the poly-D-lactic acid film is prepared by a solution casting method; after preliminary treatment such as stretching and annealing, when the film is subjected to bending deformation, the film is subjected to stress in a shearing direction, internal polarization occurs and corresponding electric charges are generated on the surface electrode, the electric charges are redistributed through an external circuit between the electrodes, and the electric charges are transferred between the two electrodes through the external circuit to generate an electric current, so that a mechanical signal is converted into an electric signal. By measuring the corresponding electric signal, the intensity and frequency of the micro-movement of a living body can be obtained, for example, by measuring and recording the electric signal, an electrocardiogram of a detected person can be obtained, and then health information can be judged, and the heart sound and pulse can be monitored.

[0037] ​Specifically, the roles of the upper and lower electrodes 1, 3 are to change the surface charge density of the dipole moment inside the sensing element when the dipole moment is subjected to pressure or tension, i.e. the charges flow between the two electrodes to output an electrical signal. The role of the sensing element 2 is to convert a mechanical signal into an electrical signal when the sensing element 2 is deformed by an external force; the reason for selecting PLLA or PDLA as the material of the sensing element 2 is that they have a high piezoelectric coefficient, which can improve the sensitivity, and they are biodegradable and renewable, environmentally friendly materials, and most importantly, the piezoelectricity is derived from the special structure and ordered arrangement of the molecular chain, and is not due to the orientation of the dipole caused by polarization, so it does not have pyroelectric effect, avoiding the interference of temperature signals. The purpose of using the metal compression ring 4 is to fix the edges of the PLLA or PDLA film, so that it can be converted into tensile stress along the shear direction when subjected to pressure perpendicular to the surface of the film. The role of the insulating pad 5 is to prevent the lower electrode from contacting the metal shell, avoiding short circuit between the two electrodes. The role of the cavity 6 is to provide a certain space for the sensing element 2 to deform after being subjected to pressure; the area is equal to that of the sensing element, and the thickness is generally a few millimeters, which meets the needs and is not strictly required. The purpose of the metal shell 7 is to serve as a carrier for the entire device, and more importantly, the metal shell 7 covers the lower electrode 3 in a closed structure, which shields external noise; the metal shell 7 is made of aluminum, and other metals or other conductive materials can also be used; the structure is circular, and other shapes can also be used.

[0038] The negative electrode is necessary as a shielding cover to eliminate noise. The positive and negative electrodes are generally metal electrodes with good conductivity, such as gold, silver, copper, aluminum, etc. Other conductive materials such as conductive polymers can also be used, but the resistance will reduce the sensitivity.

[0039] The piezoelectricity of PLLA is slightly larger than that of PDLA, but it has little effect on the output result.

[0040] On the basis of the above embodiment, it further includes a terminal post 8 provided on the side of the metal shell 7, the positive electrode of the terminal post 8 is connected with the lower electrode 3 through a wire passing through the cavity 6, and the negative electrode is connected with the upper electrode 1 through the metal shell 7.

[0041] The metal shell 7 is connected with the metal shell of the negative electrode terminal post of the upper electrode 1 and the metal compression ring 4, and forms a closed structure to cover the lower electrode 3 in the closed structure, which shields external noise; at the same time, the lower electrode can be connected with the positive electrode of the terminal post 8 (the inner electrode of the terminal post) through a wire passing through the cavity 6, and finally the terminal post 8 transmits the collected signal to the recording and display device through a shielding signal line matched therewith.

[0042] On the basis of the above embodiment, it further includes a screw 9 which successively penetrates the metal compression ring 4, the sensing element 2 and the metal shell 7 to fix them.

[0043] Screw rod 9, for example, can be four, the role of the sensor element 2 with the upper electrode 1 and the lower electrode 3, metal compression ring 4, insulating pad 5, metal shell 7 fixed together to form a complete sensor, please see Figure 2 The physical diagram.

[0044] On the basis of the above embodiment, the insulating pad 5 is a ring structure with a middle protrusion, and the interface is L-shaped.

[0045] Please see Figure 3 , the insulating pad 5 adopts the middle protrusion mode, so that the metal compression ring 4 is fixed after the sensor element 2, the sensor element 2 is at the outermost end of the whole device, which helps the sensor to collect heart sound signal more conveniently.

[0046] On the basis of the above embodiment, the sensor element 2 is a thin film structure of at least one layer.

[0047] The piezoelectric film can be solution casting, electrospinning film or other piezoelectric film prepared by other methods; single layer piezoelectric film can be used, and multi-layer piezoelectric film can also be used to enhance sensitivity; if it is a multi-layer piezoelectric film, the connection mode between the piezoelectric films is parallel.

[0048] The sensitivity is reduced if the piezoelectric film is too thick, and the piezoelectric film is easy to break if it is too thin. The thickness of the piezoelectric film is 5-30 microns, preferably 10-20 microns.

[0049] Another embodiment of the present application provides a piezoelectric film-based pulse sensor, characterized in that it comprises: at least one sensor element 12, which is a poly-L-lactic acid film or a poly-D-lactic acid film, and the upper and lower surfaces of the sensor element 12 are respectively provided with an upper electrode 11 and a lower electrode 13; a flexible substrate 15, which covers the lower electrode 13 of each sensor element 12 and forms a cavity 14 between the lower electrode 13 and the flexible substrate 15; each lower electrode 13 is connected to the positive electrode of a terminal post 16 through the inside of the flexible substrate 15, and the upper electrode 11 is connected to the shell of the terminal post 16 through the metal electrode covering the surface of the whole device; the pulse sensor is wearable, and when it is subjected to the pressure of the pulse, the poly-L-lactic acid film or the poly-D-lactic acid film as a detection element converts the pulse signal into an electric signal and outputs, while shielding the interference of the temperature signal.

[0050] The material of the sensor element is selected from PLLA or PDLA and the electrode is the same as that of the heart sensor. Here, the difference between the pulse sensor is mainly introduced.

[0051] Here, a sensing unit is taken as an example to illustrate, and a plurality of sensing units can also be used to form an array. According to the need, a flexible sensor can also be designed by using a flexible material. For example, a flexible substrate is arranged at the bottom of the sensor element 12, and the flexible substrate is provided with an array composed of a plurality of sensing units, please see Figure 4 ,Figure 5 The substrate can adopt flexible materials such as PDMS, PET, PI, etc., the lower electrode of the transducing element is connected with the positive pole of the connecting post through the inside of the substrate, and the upper electrode of the sensing element is connected with the shell of the connecting post through the metal electrode coated on the surface of the whole device.

[0052] On the basis of the above embodiment, the sensing element 12 is a thin film structure of at least one layer.

[0053] The piezoelectric film can be solution casting, electrospinning film or piezoelectric film prepared by other methods; a single layer of piezoelectric film can be adopted, and a multi-layer piezoelectric film can also be adopted to enhance the sensitivity; if the piezoelectric film is a multi-layer piezoelectric film, the connection mode between the piezoelectric films is in parallel.

[0054] If the piezoelectric film is too thick, the sensitivity is reduced, and if the piezoelectric film is too thin, it is easy to break; the thickness of the piezoelectric film is 5-30 microns, and preferably 10-20 microns.

[0055] The heart and pulse sensor provided by the application fundamentally solves the interference of the body temperature signal on the heart sound signal because PLLA or PDLA only has strong piezoelectricity and no thermoelectricity, and the interference of the external electromagnetic field is shielded due to the design of the negative pole coating type structure, so it is a new type of sensor with good stability and high sensitivity. In addition, the signal is digitized, which can directly output the graph through the display device, improving the accuracy of clinical diagnosis. At the same time, the result can be compared with the standard data to obtain the diagnosis result, which is convenient for non-professionals to use, and makes the medical equipment home-based. Compared with the traditional other heart sound stethoscope, the application has the advantages of high precision, high reliability, simple use and environment-friendly, and has good application prospect in future clinical diagnosis, home medical treatment and Internet of Things development.

[0056] Another embodiment of the application provides a preparation method of a heart sensor based on a piezoelectric film, please see Figure 6 , comprising: S11, solution casting to prepare a sensing element 2 film, which is a poly-L-lactic acid film or a poly-D-lactic acid film; S12, sputtering an upper electrode 1 and a lower electrode 3 on the upper and lower surfaces of the sensing element 2 film respectively; S13, coating the lower electrode 3 with a metal shell 7 and forming a cavity 6 between the two, and fixing the metal shell 7 with the insulating pad 5, the sensing element 2 and the metal compression ring 4 in sequence; when the heart sensor is subjected to the pressure of heartbeat, the poly-L-lactic acid film or the poly-D-lactic acid film as a detection element converts the heart sound signal into an electric signal and outputs, and can shield the interference of the temperature signal at the same time.

[0057] Here, taking the PLLA film as an example, during the preparation process, the PLLA film obtained by solution casting is subjected to uniaxial stretching, annealing and other preliminary treatments, so that the molecular chains in the film are arranged in order, and thus have d 14The piezoelectricity of the PLLA film is used in the application. The processed PLLA film is cut into a suitable size along a direction 45° to the stretching direction. When the piezoelectric PLLA film is subjected to a slight pressure of heartbeat or pulse, the film is deformed in a corresponding bending form. Since the edges of the PLLA film are fixed, the film is subjected to a tensile stress when being bent. Due to the piezoelectricity of the PLLA film, corresponding induced charges are generated on the electrodes on both sides of the piezoelectric film, that is, an electric current is formed in an external circuit, and the conversion of the heart sound signal into an electric signal is realized.

[0058] S11 specifically comprises: S111, dissolving poly-L-lactic acid or poly-D-lactic acid in dichloromethane, casting on a steel plate, drying at room temperature, and completely volatilizing the solvent to obtain a film; S112, uniaxially stretching the film, annealing, and cutting into a shape.

[0059] The piezoelectric film prepared by the solution casting method has the advantages of low cost, high efficiency, and easy industrial production.

[0060] On the basis of the above embodiment, S13 further comprises mounting the terminal post 8 in the through hole reserved on the side of the metal shell 7, connecting the positive electrode of the terminal post 8 with the lower electrode 3 through a wire passing through the cavity 6, and connecting the negative electrode of the terminal post 8 with the upper electrode 1 through the metal shell 7.

[0061] The positive electrode of the terminal post 8 is connected with the lower electrode 3 of the sensing element 2, and the negative electrode is connected with the upper electrode 1 of the sensing element 2. Finally, the terminal post 8 transmits the collected signal to a recording and display device through a shielded signal line matched therewith.

[0062] Another embodiment of the present application provides a preparation method of a pulse sensor based on a piezoelectric film, as shown in Figure 7 , comprising: S21, preparing at least one sensing element 12 film by solution casting, which is a poly-L-lactic acid film or a poly-D-lactic acid film; S22, sputtering an upper electrode 11 and a lower electrode 13 on the upper and lower surfaces of the sensing element 12 film, respectively; S23, wrapping a flexible substrate 15 around the lower electrode 13 of each sensing element 12 and forming a cavity 14 therebetween; each lower electrode 13 is connected with the positive electrode of a terminal post 16 through the inside of the flexible substrate 15, and the upper electrode 11 is connected with the shell of the terminal post 16 through a metal electrode wrapped on the surface of the entire device; the pulse sensor is wearable, and when subjected to the pressure of a pulse, the poly-L-lactic acid film or the poly-D-lactic acid film as a detection element converts the pulse signal into an electric signal and outputs, while shielding the interference of a temperature signal.

[0063] The preparation method of the pulse sensor is the same as the method of S21-S22 in the preparation method of the heart sensor, and the difference is that S23 is different from S13, and the flexible substrate 15 is used to cover the lower electrode in S23, so that the pulse sensor can be worn, and when the pulse sensor is subjected to the pressure of the pulse, the poly-L-lactic acid film or the poly-D-lactic acid film as the detection element converts the pulse signal into an electrical signal and outputs, and at the same time, the temperature signal interference can be shielded. And S13 adopts the metal shell 7 to cover the lower electrode, which can directly and closely contact the skin near the human heart, and the poly-L-lactic acid film or the poly-D-lactic acid film as the detection element converts the heart sound signal into an electrical signal and outputs, and at the same time, the temperature signal interference can be shielded.

[0064] The application will be further described below with reference to the drawings.

[0065] At present, in the heart sound detection equipment used in the clinic, the traditional stethoscope needs professional personnel to judge the sound information heard by relying on rich experience to obtain a diagnosis result, and this diagnosis method needs professional personnel to operate, and the heart sound detection equipment based on the electromagnetic coil and the PVDF is also easy to be disturbed by the electromagnetic field and the heat signal in the environment. Therefore, the application discloses a new type of sensor, which accurately outputs the detected heart sound signal to avoid misjudgment, adopts PLLA with good piezoelectricity as a sensing element to realize high sensitivity, avoids the interference of the heat signal due to the heat stability of the PLLA, and shields the influence of environmental noise through the structure design of the negative electrode covering the positive electrode.

[0066] The embodiment of the application proposes a heart sensor based on a piezoelectric film and a preparation method thereof, which comprises an upper electrode 1, a transducer element 2, a lower electrode 3, a metal compression ring 4, an insulating pad 5, a cavity 6, a metal shell 7, a terminal post 8 and four screw rods 9, as shown in the figure. Figure 1

[0067] The specific processing flow is as follows:

[0068] S11: A piezoelectric film (this embodiment takes PLLA as an example) is prepared by using a solution casting method (other methods can also be used).

[0069] ​Specifically, a PLLA solution is prepared by dissolving PLLA (MW=260000, polydispersity index≤1, Sigma-Aldrich Corp., USA) powder in dichloromethane and then stirring at room temperature for 4-10 hours. The prepared uniform solution is cast on a clean steel plate, dried at room temperature for 10-24 hours to completely evaporate the solvent. The dried PLLA film with a thickness of 10-100 microns is removed from the steel plate and uniaxially stretched by 2-8 times, and the stretched film is annealed in an oven at 110-140°C for 2-6 hours. Then the PLLA film is cut into a suitable size circle.

[0070] S12: sputtering electrodes on the upper and lower surfaces of the PLLA film.

[0071] S13: designing and drawing the patterns of the metal compression ring 4, the insulating pad 5 and the metal shell 7 using CAD drawing software. The patterns are processed using a numerical control machine.

[0072] The terminal post 8 is installed in the reserved through hole of the metal shell 7, wherein the negative electrode of the terminal post is in conduction with the metal shell.

[0073] A conductive adhesive tape is pasted on the upper side of the insulating pad 5, and a wire with insulating rubber is used to connect the conductive adhesive tape and the positive electrode of the terminal post 8.

[0074] The insulating pad 5, the sensing element 2 and the metal compression ring 4 are sequentially placed on the metal shell 7, and the reserved screw hole is sequentially aligned.

[0075] The parts of the sensor are fixed together by the screw 9, and the metal screw is ensured not to contact the lower electrode 3. In this way, the lower electrode 3 is connected to the positive electrode of the terminal post 8 through the wire, the upper electrode 1 is connected to the negative electrode of the terminal post 8 through the metal shell 7, and the positive electrode is completely wrapped in the shielding cover formed by the negative electrode, which can play a shielding effect.

[0076] In the present application, the function of the shell 7 is to shield noise, and it is only necessary to completely wrap the positive electrode with the negative electrode. If an insulating material is used, the inner surface or the outer surface should be coated with a continuous metal electrode, and the metal electrode and the upper electrode of the transducer element should be in conduction. If only part of the shell or part of the inner surface is made of metal material, the remaining part should have a continuous conductive material to form a closed negative shield.

[0077] The piezoelectric-based biosensor prepared above is tested, for example, Figure 8 and Figure 9 The data shows that the heart rate of the detected person is 75 times per minute, which is within the normal range of adult heart rate, indicating that the signal output by the sensor is indeed an accurate heart rate signal.

[0078] For example,Figure 10 The variation pattern of the heartbeat signal in a heart rhythm cycle reflects the activity of the heart of the detected person in a cycle, and each peak of the curve in the figure corresponds to the beating of the left and right atrium and ventricle.

[0079] The transducer element prepared according to the above preparation method is also used to prepare a pulse sensor, such as Figure 11 and Figure 12 The data shows that the pulse of the detected person is 75 times per minute, which is within the normal range of adult pulse. It shows that the signal output by the sensor is indeed an accurate pulse signal. The pulse signal is smaller than the heartbeat signal, because the beating amplitude of the pulse is smaller than the heartbeat amplitude.

[0080] As shown in Figure 13 , the output charge density of PLLA increases with the increase of strain, and the slope of the increase is the piezoelectric coefficient of the PLLA material. The piezoelectric coefficient d 14 of the PLLA used here is 9.8 pC / N, which shows that the PLLA has good piezoelectric performance, which guarantees the high sensitivity of the sensor.

[0081] The PLLA or PDLA film provided by the application as a new type of sensor of a sensing element has high conversion efficiency and avoids the interference of thermal signals on electrical signals due to its thermal stability and relatively high piezoelectric coefficient, and at the same time, the structure of the negative electrode coating shields the interference of environmental noise, so that the detected heart sound signal can be directly output as an electrical signal, improving the accuracy of diagnosis. It has very high application value in future wearable clinical diagnosis, home medical care, human-computer interaction, Internet of Things and other aspects.

[0082] The structure and preparation method provided by the application are not only used on biosensors, but also can be applied to other aspects. The following provides three application examples in other aspects.

[0083] 1. Clinical diagnosis

[0084] Compared with the traditional stethoscope, the sensor provided by the application can directly output the collected information as accurate data, and is convenient for archiving and recording, avoiding misdiagnosis caused by human experience. Compared with sensors based on electromagnetic coils and PVDF, it has better stability, higher sensitivity and signal-to-noise ratio. Therefore, in the aspect of clinical diagnosis, such as detection of heart rhythm, pulse, respiration, blood pressure and judgment of the internal condition of thoracic cavity and abdominal cavity, the application example has greater application potential compared with the commonly used detection equipment at present.

[0085] First, the sensor element of the sensor is tightly attached to the left chest or wrist, and when the heart and pulse beat, the sensor element is squeezed, the sensor converts the stress signal of the squeezing into an electrical signal and outputs to the display device, and according to the frequency and waveform of the electrical signal, the beating condition of the heart and pulse can be accurately judged. Secondly, the sensor element of the sensor is tightly attached to the chest cavity or placed near the mouth and nose, and when breathing, the fluctuation of the chest cavity and the impact of the mouth and nose airflow on the sensor element produce stress and output an electrical signal. The strength and frequency of the electrical signal reflect the information of the breathing. Thirdly, the sensor cooperates with the pressure detector, which can replace the traditional stethoscope to measure blood pressure. Finally, when the internal organs move, they will make corresponding sounds, and the sensor element of the sensor can be tightly attached to the chest cavity or abdominal cavity, and the health condition of the internal organs of the human body can be judged by recording the sound of the internal organs and comparing it with the standard data.

[0086] 2、Microphone sensor

[0087] When sound propagates through a medium, the sound wave is manifested as the vibration of the medium, so the surface of the sensor to which the sound propagates will also cause the vibration of the transducer element, and the transducer element converts the vibration of the sound wave into an electrical signal output, that is, the sensor of the present application can be used as a microphone.

[0088] 3、Network medical treatment

[0089] The example of the present application can output the detected health information in a data form, and further, the data can be uploaded to a network, and medical personnel can view the detected data online and judge the illness. Therefore, the sensor of the present application is expected to realize online medical treatment, and especially, people who are inconvenient to move can go to a hospital without going out. Further, a flexible substrate can be selected to manufacture the sensor into a flexible wearable sensor array, and after the old or sick person wears the sensor array, the health information of the human body can be collected in real time, and the collected information can be uploaded to the network through a wireless transmission device. The analysis device can find abnormalities by analyzing the received information, and can send an alarm to relevant personnel and institutions, and according to the IP of the sensor, the position of the patient can be determined, so that timely treatment is realized, and certain dangers are avoided.

[0090] The above-described specific embodiments further illustrate the purpose, technical solutions and beneficial effects of the present application, and it should be understood that the above-described only the specific embodiments of the present application, and not for limiting the present application, any modification, equivalent replacement, improvement, etc. made within the spirit and principles of the present application, should be included in the protection scope of the present application.

Claims

1. A heart sensor based on a piezoelectric thin film, characterized in that, include: The sensing element (2) is a poly(L-lactic acid) film or a poly(D-lactic acid) film, with an upper electrode (1) and a lower electrode (3) respectively on its upper and lower surfaces. A metal casing (7) covers the lower electrode (3) and forms a cavity (6) between them; an insulating pad (5) is provided at the contact portion between the metal casing (7) and the lower electrode (3). A metal pressure ring (4) is provided on the edge of the sensing element (2) and the sensing element (2) is fixed on the metal shell (7) so that when the heart sensor is subjected to the pressure of the heartbeat, the poly-L-lactic acid film or poly-D-lactic acid film acts as a detection element to convert the heart sound signal into an electrical signal and output it, while shielding the interference of temperature signal. A terminal block (8) is located on the side of the metal casing (7). The positive electrode of the terminal block (8) is connected to the lower electrode (3) through a wire passing through the cavity (6), and the negative electrode is connected to the upper electrode (1) through the metal casing (7).

2. The heart sensor based on a piezoelectric thin film according to claim 1, characterized in that, Also includes: The screw (9) passes through the metal pressure ring (4), the sensing element (2), and the metal shell (7) in sequence to fix them.

3. The piezoelectric-based biosensor according to claim 1, characterized in that, The insulating pad (5) is a ring-shaped structure with a raised center and an L-shaped interface.

4. The piezoelectric-based biosensor according to claim 1, characterized in that, The sensing element (2) is a thin film structure with at least one layer.

5. A pulse sensor based on a piezoelectric thin film, characterized in that, include: At least one sensing element (12) is a poly-L-lactic acid film or a poly-D-lactic acid film, with an upper electrode (11) and a lower electrode (13) respectively on its upper and lower surfaces. A flexible substrate (15) covers the lower electrode (13) of each sensing element (12) and forms a cavity (14) between them; each lower electrode (13) is connected to the positive terminal of the terminal (16) through the interior of the flexible substrate (15), and the upper electrode (11) is connected to the outer shell of the terminal (16) through a metal electrode covering the entire surface of the device; the pulse sensor is wearable, and when subjected to pulse pressure, the poly-L-lactic acid film or poly-D-lactic acid film acts as a detection element to convert the pulse signal into an electrical signal and output it, while shielding the interference of temperature signals.

6. The piezoelectric-based biosensor according to claim 5, characterized in that, The sensing element (12) is a thin film structure with at least one layer.

7. A method for fabricating a cardiac sensor based on a piezoelectric thin film, characterized in that, include: S11, solution casting is used to prepare the sensing element (2) thin film, which is a poly-L-lactic acid film or a poly-D-lactic acid film; S12, the upper electrode (1) and the lower electrode (3) are sputtered on the upper and lower surfaces of the thin film of the sensing element (2), respectively. S13, the metal shell (7) covers the lower electrode (3) and forms a cavity (6) between them, and the metal shell (7) is fixed in sequence with the insulating pad (5), the sensing element (2) and the metal pressure ring (4); when the heart sensor is subjected to the pressure of the heartbeat, the poly-L-lactic acid film or poly-D-lactic acid film acts as a detection element to convert the heart sound signal into an electrical signal and output it, while shielding the interference of the temperature signal; S13 and thereafter includes installing the terminal (8) in a through hole reserved on the side of the metal housing (7), wherein the positive electrode of the terminal (8) is connected to the lower electrode (3) through a wire passing through the cavity (6), and the negative electrode is connected to the upper electrode (1) through the metal housing (7).

8. A method for fabricating a pulse sensor based on a piezoelectric thin film, characterized in that, include: S21, at least one sensing element (12) thin film is prepared by solution casting, which is a poly-L-lactic acid film or a poly-D-lactic acid film; S22, an upper electrode (11) and a lower electrode (13) are sputtered onto the upper and lower surfaces of the thin film of the sensing element (12), respectively. S23, the flexible substrate (15) covers the lower electrode (13) of each sensing element (12) and forms a cavity (14) between them; each lower electrode (13) is connected to the positive terminal of the terminal (16) through the interior of the flexible substrate (15), and the upper electrode (11) is connected to the outer shell of the terminal (16) through a metal electrode covering the entire surface of the device; the pulse sensor is wearable, and when subjected to the pressure of the pulse, the poly-L-lactic acid film or poly-D-lactic acid film acts as a detection element to convert the pulse signal into an electrical signal and output it, while shielding the interference of temperature signals.

Images