A passive sensor for real-time cardiac monitoring and its applications

Abstract

The present invention belongs to the technical field related to cardiac monitoring, and discloses a passive sensor for real-time cardiac monitoring and its application. The passive sensor includes a monitoring unit, a flexible substrate, and a signal receiving unit, wherein: the monitoring unit is a thin film composed of a material with an electric double layer effect. Thus, cations and anions in the interstitial fluid around the heart are adsorbed on the surface of the monitoring unit to form an electric double layer structure. When the cardiac muscle relaxes and contracts or the blood flow signal is transmitted, the change in pressure will further cause the change in the effective charge adsorption area, resulting in the change of the current signal; the flexible substrate is used to isolate the monitoring unit and the signal receiving unit; the signal receiving unit is connected to the monitoring unit for receiving the charge change on the surface of the monitoring unit, and serves as a counter electrode to form a closed loop with the monitoring unit. This application can realize the real-time monitoring and signal acquisition of cardiac mechanical signals, with high sensitivity and high accuracy.

Description

Technical Field

[0001] The present invention belongs to the technical field related to cardiac monitoring, and more specifically, relates to a passive sensor for real-time cardiac monitoring and its application. Background Art

[0002] The heart is one of the most important organs in the human body. As the power of the circulatory system, it maintains the basic vital signs of the human body. In the 21st century, cardiovascular diseases such as myocardial infarction, arrhythmia or atrial fibrillation are highly prevalent, seriously threatening people's lives. Therefore, detecting the physiological state of the heart is one of the key directions in modern life science.

[0003] Currently, detecting cardiac information mainly relies on electrocardiogram and ultrasound equipment. For example, the detection principle of electrocardiogram is based on the change in the permeability of the myocardial cell membrane, which causes a large number of cations to rush into the membrane, reversing the membrane potential. This process is called depolarization, and the depolarization process is recorded, which is the P wave of the atrium and the QRS wave of the ventricle on the surface electrocardiogram. After the depolarization process, the cell membrane expels cations and the potential returns to the original polarized state, which is called the repolarization process. This process is also recorded. The repolarization process of the ventricle is manifested as the T wave in the electrocardiogram. Electrocardiogram can detect arrhythmias, diagnose myocardial ischemia, myocardial infarction and its location, and diagnose cardiac enlargement and hypertrophy. However, the electrocardiogram detects electrical signals, and the accuracy is not as high as that of mechanical signals, and there are limitations in exploring the pathogenesis of some heart diseases. For example, when diagnosing atrial and ventricular hypertrophy, since the electrocardiogram detects comprehensive electrical activities, the electrocardiogram may not show after vector cancellation; when diagnosing myocardial ischemia, the changes in the ST-T band lack specificity and other detection methods must be combined for judgment. Echocardiography is a technical means for detecting the heart through ultrasound. Ultrasonic examination is a technical means that uses the reflection of sound waves in the human body and receives information by a machine to derive images. Ultrasound can detect the location of heart lesions and whether the heart function is normal. However, the image clarity and resolution of ultrasonic detection are low, relying on the skills of the operating doctor, and different doctors may have different conclusions. Ultrasound cannot detect the coronary artery, and the accuracy is low. Therefore, there is still room for improvement in the current cardiac data acquisition, and there is an urgent need to design a more accurate and precise cardiac data detection device. Summary of the Invention

[0004] In view of the above defects or improvement requirements of the prior art, the present invention provides a passive sensor for real-time cardiac monitoring and its application, which can realize real-time monitoring and signal acquisition of cardiac mechanical signals, with high sensitivity and high precision.

[0005] To achieve the above object, according to one aspect of the present invention, a passive sensor for real-time cardiac detection is provided. The passive sensor includes a monitoring unit, a flexible substrate, and a signal receiving unit, wherein: the monitoring unit is a thin film composed of a material with a double-layer capacitance effect. Thus, cations and anions in the interstitial fluid around the heart are adsorbed on the surface of the monitoring unit to form a double-layer structure. When the heart muscle relaxes and contracts or the blood flow signal is transmitted, the change in pressure will further cause the change in the effective charge adsorption area, resulting in the change of the current signal; the flexible substrate is used to isolate the monitoring unit and the signal receiving unit; the signal receiving unit is connected to the monitoring unit for receiving the charge change on the surface of the monitoring unit, and forms a closed loop with the monitoring unit as a counter electrode.

[0006] Preferably, the elastic modulus of the monitoring unit is 6 to 30 times that of the heart.

[0007] Preferably, the monitoring unit is a patterned and hollowed-out structure.

[0008] Preferably, the monitoring unit is a circular micropore lattice pattern. Further preferably, the porosity of the monitoring unit is greater than or equal to 0.3.

[0009] Preferably, the number of holes K distributed in a single row on the surface of the monitoring unit is greater than or equal to 3, and the range of the hole diameter d is 0 < d ≤ l / K, where l is the side length of the monitoring unit.

[0010] Preferably, the monitoring unit is carbon nanotubes, graphene, or a porous carbon film.

[0011] Preferably, the thickness of the passive sensor is 300 to 1200 μm.

[0012] Preferably, the material of the flexible substrate is medical-grade PVC, polyethylene, PEEK, or polycarbonate.

[0013] Preferably, the material of the signal receiving unit is carbon nanotubes or graphene.

[0014] On the other hand, the present application provides an application of the above passive sensor for real-time cardiac monitoring. When in use, the monitoring unit is adhered to the surface of the heart by means of a biological glue or suture.

[0015] Generally speaking, compared with the prior art by the above technical solutions conceived by the present invention, the passive sensor for real-time cardiac monitoring provided by the present invention and its application mainly have the following beneficial effects:

[0016] 1. This application uses a monitoring unit with an electric double layer effect. Consequently, cations and anions in the interstitial fluid around the heart are adsorbed on the surface of the monitoring unit, forming an electric double layer structure. When the heart muscle relaxes and contracts or the blood flow signal is transmitted, the change in pressure will further cause the change in the effective charge adsorption area, resulting in the change of the current signal, which is significantly higher than the electrocardiogram electrical signal in terms of information validity and accuracy, and the sensitivity and accuracy are significantly improved.

[0017] 2. The detection unit of this application adopts a patterned and hollowed-out design. Firstly, the patterning process can achieve the mechanical monitoring of complex deformations. Since the heartbeat is a very complex periodic mechanical movement, the activities on the surface of the heart tissue include stretching, compression, torsion, and bending. Commonly used pressure sensors cannot accurately identify this process, while the material after patterning can perform synchronous stretching, compression, torsion, and bending movements with the heart tissue to achieve the monitoring of the mechanical signals of the entire cardiac cycle. Secondly, the patterning process improves the sensitivity of the device. Since the working mechanism of this device relies on the movement of charges on the surface of the monitoring unit, after patterning, on the one hand, the wettability of the interstitial fluid in the monitoring unit is improved, thereby increasing the charge adsorption amount. On the other hand, the pattern provides a more accurate transfer path for the charges on the surface of the monitoring unit. When the heart contracts and relaxes, the monitoring unit regionalizes different movement types and degrees in different positions, and the rapid transfer of charges enables rapid response. Thirdly, this design reduces the elastic modulus of the material so that it has a matching elastic modulus with the heart tissue, avoiding the influence of the introduction of the device on the original myocardial function.

[0018] 3. The hollowed-out part of the monitoring unit of this application is a circular fine pore dot matrix pattern. Compared with patterns such as squares and rhombuses, this pattern can make the deformation of the entire monitoring unit more uniform.

[0019] 4. The porosity and pore diameter design of the hollowed-out part of the monitoring unit of this application can ensure that the elastic modulus of the monitoring unit is coordinated with the heart, that is, within 6 - 30 times of the heart elastic modulus. When the elastic modulus of the monitoring unit is lower than 6 times of the heart elastic modulus, the contact area between the monitoring unit and the heart is small, and the sensitivity of the monitoring unit drops rapidly, resulting in poor monitoring performance. When the elastic modulus of the monitoring unit is higher than 30 times of the heart elastic modulus, the foreign body sensation in the human body is strong, greatly reducing the user experience and aggravating the discomfort of the patient.

[0020] 5. The passive sensor driven by interstitial fluid can collect information without an external power supply, with a simple structure and a small volume.

[0021] 6. This passive sensor is small in size and can be implanted into the human body by various means such as adhesion, puncture, and integration with other implants. It has strong usability and small trauma during implantation, and can be widely used in the health status tracking of patients. Brief Description of the Drawings

[0022] Figure 1 Schematically shows a schematic structural diagram of a passive cardiac sensor for real-time cardiac monitoring according to this embodiment;

[0023] Figure 2 Schematically shows the shape, size, and distribution pattern of the pattern during patterning;

[0024] Figure 3 Schematically shows an enlarged view of the carbon nanotubes of the passive sensor according to this embodiment;

[0025] Figure 4 Schematically shows the biocompatibility of the passive sensor of the embodiment of the present application in a mouse body;

[0026] Figure 5 Schematically shows the peak current change of the passive sensor of the embodiment of the present application under different pressures;

[0027] Figure 6 Schematically shows the graph of the power of the passive sensor of the embodiment of the present application changing with time.

[0028] In all the drawings, the same reference numerals are used to represent the same elements or structures, where:

[0029] 1 - Monitoring unit; 2 - Flexible substrate; 3 - Signal receiving unit. Detailed implementation manners

[0030] In order to make the objectives, technical solutions, and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention. In addition, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0031] The present invention provides a passive sensor for real-time cardiac monitoring, as Figure 1 shown, the passive sensor includes a monitoring unit 1, a flexible substrate 2, and a signal receiving unit 3, and the specific structure is as follows.

[0032] The material of the monitoring unit 1 is a material with a double-layer effect. Thus, the cations and anions in the tissue fluid around the heart are adsorbed on the surface of the monitoring unit 1 to form a double-layer structure. When the heart muscle relaxes and contracts or the blood flow signal is transmitted, the change in pressure will further cause the change in the effective charge adsorption area, resulting in the change in the current signal. In a further preferred solution, the monitoring unit 1 is carbon nanotubes, graphene, or a porous carbon film.

[0033] In a further preferred embodiment, the elastic modulus of the monitoring unit is 6 to 30 times that of the heart. Within this range, both good monitoring performance of the monitoring unit and better user experience can be maintained.

[0034] In a further preferred embodiment, the monitoring unit 1 is a patterned and hollowed-out thin film. After being patterned and hollowed out, its elastic modulus is 6 to 30 times that of the heart.

[0035] In a further preferred embodiment, the monitoring unit 1 is a circular fine-hole lattice pattern. Compared with patterns such as square and rhombus, this pattern can make the deformation of the entire monitoring unit 1 more uniform.

[0036] In a further preferred embodiment, the porosity of the monitoring unit 1 (i.e., the ratio of the pore area to the overall area of the sample) is greater than or equal to 0.3. At this ratio, the patterned treatment makes the elastic modulus of the monitoring unit close to that of the heart while having the most uniform distribution.

[0037] In a further preferred embodiment, the number K of holes distributed in a single row on the surface of the monitoring unit 1 is greater than or equal to 3, and the range of the hole diameter d is 0 < d ≤ l / K, where l is the side length of the monitoring unit 1.

[0038] For example, as Figure 2 shown, it is a specific structure of the monitoring unit 1. The side length of this structure is 6 mm, the diameter of the circular pattern is 1 mm, the number K of holes distributed in a single row on the surface is 3, and the total number of holes is 9, which are evenly distributed.

[0039] The material of the flexible substrate 2 is a thin film with good biocompatibility and elasticity such as medical-grade PVC, polyethylene, PEEK, polycarbonate, etc., and is used to isolate the monitoring unit and the signal receiving unit. The elastic material can change with the contraction or relaxation of the heart, further reducing human discomfort. The flexible substrate 2 can be adhered to the outer surface of the monitoring unit 1 by means of biological glue, suture, etc.

[0040] The signal receiving unit 3 is connected to the monitoring unit 1 for receiving the charge change on the surface of the monitoring unit 1, and serves as a counter electrode to form a closed circuit with the monitoring unit 1. In a further preferred embodiment, the material of the signal receiving unit 3 is carbon nanotube or graphene. The signal receiving unit 3 can also emit signals outward.

[0041] The thickness of the passive sensor is preferably 300 to 1200 μm. If it is less than 300 μm, it is easy to break during the implantation process and the surgical operability is poor. If it is higher than 1200 μm, it will cause poor flexibility.

[0042] On the other hand, the present application provides an application of the above-mentioned passive sensor for real-time cardiac monitoring. When in use, the monitoring unit is adhered to the cardiac surface by means of biological glue or suture. Of course, it is not limited to the above methods, and it can also be integrally implanted into other implants such as stents, as Figure 3 shown.

[0043] In order to characterize the performance of the passive sensor, the following performance tests are carried out on the passive sensor:

[0044] As Figure 4 shown, this experiment is a hemolysis experiment. The material used for the passive sensor will not cause red blood cell rupture, effectively indicating that the material has good biocompatibility.

[0045] Please refer to Figure 5 . The passive sensor is connected into a closed loop, and the PBS solution is used to simulate the in-vivo environment to obtain the current-time images under different pressures. The experiment proves that as the pressure increases, the signal received by the passive sensor also becomes larger and larger, indicating that the passive sensor has an obvious positive feedback to pressure. Moreover, observing each group of data, they are all stable peaks, indicating that the signal can be stably monitored. In summary, the passive sensor can stably receive pressure signals.

[0046] Please refer to Figure 6 . At different frequencies, the pressure signals received by the passive sensor do not change significantly, indicating that the frequency does not interfere with the monitoring of the pressure signal by the passive sensor.

[0047] The passive sensor provided by the present application realizes the adaptation to cardiac systole and diastole through the flexible substrate and the monitoring unit, reducing the discomfort of the human body. The monitoring unit is composed of a material with good biocompatibility and driven by tissue fluid. The monitoring unit can adsorb tissue fluid ions to form a double-layer structure. When the heart contracts, relaxes, and blood flows, it changes the effective area of charge adsorption, thereby changing the current signal, with higher sensitivity and the ability to collect more effective information, and can be widely applied to the field of cardiac monitoring.

[0048] It is easy for those skilled in the art to understand that the above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, and improvements made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A passive sensor for real-time cardiac detection, characterized in that, The passive sensor includes a monitoring unit (1), a flexible substrate (2), and a signal receiving unit (3), where: The monitoring unit (1) is a thin film composed of a material with an electric double layer effect. The thin film adheres to the surface of the heart, and thus cations and anions in the interstitial fluid around the heart are adsorbed on the surface of the monitoring unit (1) to form an electric double layer structure. When the heart muscle relaxes and contracts or a blood flow signal is transmitted, the change in pressure will further cause a change in the effective charge adsorption area, resulting in a change in the current signal; The flexible substrate (2) is used to isolate the monitoring unit (1) and the signal receiving unit (3); The signal receiving unit (3) is connected to the monitoring unit (1) for receiving the charge change on the surface of the monitoring unit (1), and serves as a counter electrode to form a closed loop with the monitoring unit (1).

2. The passive sensor according to claim 1, characterized in that, The elastic modulus of the monitoring unit (1) is 6 to 30 times that of the heart elastic modulus.

3. The passive sensor according to claim 1, characterized in that, The monitoring unit (1) has a patterned and hollowed-out structure.

4. The passive sensor according to any one of claims 1 to 3, characterized in that, The monitoring unit (1) has a circular fine pore lattice pattern, and the porosity of the monitoring unit (1) is greater than or equal to 0.

3.

5. The passive sensor according to any one of claims 1 to 3, characterized in that The number K of holes distributed in a single row on the surface of the monitoring unit (1) is greater than or equal to 3, and the hole diameter d ranges from 0 < d ≤ l / K, l where l is the side length of the monitoring unit (1).

6. The passive sensor according to claim 1, characterized in that, The monitoring unit (1) is made of carbon nanotubes, graphene, or porous carbon film.

7. The passive sensor according to claim 1, wherein The thickness of the passive sensor is 300 to 1200 μm.

8. The passive sensor according to claim 1, wherein The material of the flexible substrate (2) is medical-grade PVC, polyethylene, PEEK, or polycarbonate.

9. The passive sensor according to claim 1, characterized in that, The material of the signal receiving unit (3) is carbon nanotubes or graphene.

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