Non-contact physical sign detection flexible sensor based on piezoresistance-double electric layer capacitance collaborative response and sensing method of non-contact physical sign detection flexible sensor

Abstract

The invention discloses a non-contact sign detection flexible sensor based on piezoresistance-double electric layer capacitance collaborative response and a sensing method thereof.The sensor comprises an induction electrode layer and a pressure-sensitive layer which are arranged in a stacked mode, and the upper surface of the induction electrode layer is in direct contact with the lower surface of the pressure-sensitive layer; the upper surface of the pressure-sensitive layer is attached to the surface of the fabric and is not in direct contact with the surface skin of a detected human body; in the measurement process, the working state of the sensor is switched between a relaxed state and a pressed state according to the mounting mode of the pressure-sensitive layer; the induction electrode layer is composed of a first interdigital induction electrode and a second interdigital induction electrode which are distributed in a central symmetry mode, and the induction electrodes are machined on the surface of the PI thin film through chemical deposition and etching technologies. The sensing unit can be attached to the surface of the fabric, the capacitance electrode does not need to be directly and tightly attached to the skin of the human body, high-sensitivity sign signal monitoring is achieved through the edge electric field enhancement effect, and the skin-friendly performance of the wearable device is improved.

Description

Technical Field

[0001] This invention belongs to the field of sensor technology, specifically relating to a non-contact flexible sensor for detecting vital signs based on piezoresistive-double-layer capacitance synergistic response and its sensing method. Background Technology

[0002] In recent years, smart wearable electronic products have attracted widespread attention due to their multifunctional applications in human-computer interfaces, healthcare, and human motion monitoring. As a key component for human-computer interaction and collaboration in wearable electronic products, flexible electronic components can perfectly conform to the human skin, ensuring not only the accuracy of signal acquisition but also greatly improving user comfort. The use of flexible sensors can monitor various motion and vital signs signals in real time, playing an important and irreplaceable role whether monitoring health status in daily life or assisting in judging conditions and mastering patient vital signs parameters during medical diagnosis. However, the following key points and challenges continue to emerge during use: 1) Human physiological signals are very weak compared to common signals. For example, the pressure range of respiratory signals is between 100 Pa and 1 kPa, which is only slightly greater than the pressure change caused by air flow, while the pressure range of pulse signals is usually between 1 and 10 kPa. In order to improve sensitivity, researchers have enhanced the deformation ability or dielectric constant of the dielectric layer by constructing porous structures, surface patterning designs, or doping with fillers with high dielectric constants. They have achieved higher sensitivity in the low pressure range (0-10 kPa), but still cannot meet the high requirements for accurate identification of human vital signs. 2) The breathability and heat dissipation of the device are fundamental conditions for ensuring wearing comfort and skin health. Existing wearable health monitoring sensors usually need to be in close contact with the skin to ensure accurate sensing. However, this design has some limitations. Since most sensing materials have poor breathability, prolonged close contact between the sensor and the skin may cause discomfort, such as itching, allergies, or inflammation, thus affecting the user's wearing experience. Summary of the Invention

[0003] To address the aforementioned problems in the background technology, the present invention aims to provide a non-contact flexible sensor for vital sign detection based on the synergistic response of piezoresistive and double-layer capacitance, and its measurement method. This invention can be installed and attached to the surface of fabrics such as clothing and seat belts, without direct contact with human skin. During measurement, depending on the installation mode, the sensor can operate in a relaxed state and a compressed state. In the relaxed state, the human body, as the measured object, experiences changes in vital signs such as heart rate, pulse, and blood flow rate, causing changes in its equivalent dielectric constant. By establishing a mapping relationship between the non-uniformly distributed divergent electric field under the coplanar electrode structure and the equivalent dielectric constant, real-time monitoring of general vital sign signals in non-contact mode can be achieved. In the compressed state, changes in vital signs are transmitted to the sensor surface through fabrics such as clothing and seat belts. At this time, the sensor fully utilizes the layered structure design of the pressure-sensitive layer, leveraging the synergistic response of the impedance adjustment of the piezoresistive layer and the capacitance characteristics of the ionized double-layer capacitance to achieve a vital sign signal measurement with enhanced sensitivity. Finally, the independent resistance-temperature sensitivity of the ionized layer is used to measure temperature changes, thereby realizing the multimodal tactile sensing function of temperature, proximity, and pressure of this invention.

[0004] The technical solution adopted by this invention to solve its technical problem is: The first aspect of this invention relates to a non-contact flexible sensor for vital sign detection based on piezoresistive-double-layer capacitance synergistic response, characterized in that it comprises a stacked sensing electrode layer and a pressure-sensitive layer, wherein the upper surface of the sensing electrode layer is in direct contact with the lower surface of the pressure-sensitive layer, and the upper surface of the pressure-sensitive layer is mounted on a fabric surface and does not directly contact the surface skin of the human body being measured; during measurement, the sensor's operating state switches between a relaxed state and a compressed state according to the mounting mode of the pressure-sensitive layer; the sensing electrode layer is composed of a first interdigital sensing electrode and a second interdigital sensing electrode distributed in a centrally symmetrical manner, and the sensing electrodes are processed on the surface of a PI thin film through chemical deposition and etching processes.

[0005] Furthermore, the pressure-sensitive layer has a layered structure design, with a piezoresistive layer and an ionization layer arranged sequentially from bottom to top. The upper surface of the piezoresistive layer is in direct contact with the lower surface of the ionization layer, and the lower surface of the piezoresistive layer is in direct contact with the upper surface of the sensing electrode layer. The upper surface of the ionization layer is attached to the fabric surface.

[0006] Furthermore, the piezoresistive layer is a composite material prepared by using polydimethylsiloxane as a flexible substrate and carbon nanotubes as fillers. The composite material is a gradient porous structure with pore sizes ranging from 100μm to 10μm. Micropores at the 10μm level are prepared using perfluorotributylamine as a sacrificial solution, and macropores at the 100μm level are prepared using sugar particles as pore-forming agents.

[0007] Furthermore, the ionized layer is an ion film obtained by mixing and curing polyvinyl alcohol and ionic liquid.

[0008] A second aspect of the present invention relates to a non-contact multimodal vital sign sensing method, characterized in that the sensing method employs the aforementioned non-contact flexible vital sign detection sensor, and the sensing method includes: When the fabric on which the sensor is mounted does not directly contact the human skin surface, the sensor operates in a relaxed state. A portion of the edge electric field lines emitted from the first interdigital sensing electrode of the coplanar electrode structure pass through the layered structure including the piezoresistive layer, the ionization layer, the air, and the human body being tested, and flow to the ground. The remaining electric field lines flow to the second interdigital sensing electrode. Changes in vital signs cause changes in the equivalent dielectric constant of the human body being tested, resulting in a change in the number of electric field lines flowing to the ground through the human body. The number of electric field lines flowing to the second interdigital sensing electrode also changes accordingly, which is reflected in the change of the sensing capacitance value between the two interdigital sensing electrodes. By comparing the change in capacitance value with the calibrated change in sensing capacitance - vital sign signal, real-time detection of general vital sign signals can be achieved, and the occurrence of abnormal signals can be monitored. When the fabric on which the sensor is mounted comes into direct contact with the human skin, the sensor operates under pressure. Changes in vital signs are transmitted through the fabric, transferring pressure to the sensor surface. Under pressure, a double-layer interface capacitance is formed at the interface between the piezoresistive layer and the ionized layer, increasing the capacitance density to the µF / cm² level. Simultaneously, within the piezoresistive layer, an equivalent resistance and equivalent capacitance are formed in parallel between the ionized layer and the first interdigital sensing electrode, considered as one set of equivalent impedances. Similarly, an equivalent resistance and equivalent capacitance are formed in parallel between the ionized layer and the second interdigital sensing electrode, considered as another set of equivalent impedances. These two equivalent impedances are connected in series with the double-layer capacitance. Under external load, the movement of conductive particles inside or on the surface causes a rearrangement of the conduction path, resulting in a decrease in equivalent resistance and an increase in equivalent capacitance. The impedance modulation effect of the piezoresistive layer and the double-layer capacitance characteristics of the ionized layer enable the measurement of vital signs with enhanced sensitivity. By measuring the sensing capacitance between the two interdigital sensing electrodes at this time and comparing it with the calibrated change in sensing capacitance versus the vital sign signal, real-time detection of vital signs with higher sensitivity compared to the relaxed state can be achieved.

[0009] Furthermore, the temperature difference between the surface of the human skin being tested and the fabric interface where the sensor is installed is transmitted to the ionization layer, causing a change in the electromobility of ions within it. This results in a response in the resistance value of the ionization layer to the temperature change. At the same time, the temperature change does not significantly lead to a significant change in the capacitance of the double layer interface. By measuring the sensing resistance between the two interdigital sensing electrodes at this time and comparing it with the calibrated sensing resistance change-temperature curve, the decoupled measurement of human body temperature changes can be achieved.

[0010] The technical concept of this invention is as follows: depending on the installation mode, the sensor can operate in a relaxed state and a compressed state respectively. In the relaxed state, the human body, as the object being measured, experiences changes in vital signs such as heart rate, pulse, and blood flow rate, causing changes in its equivalent dielectric constant. By establishing a mapping relationship between the non-uniformly distributed divergent electric field under the coplanar electrode structure and the equivalent dielectric constant, real-time monitoring of general vital signs signals in a non-contact mode can be achieved. In the compressed state, changes in vital signs are transmitted to the sensor surface through fabrics such as clothing and seat belts. At this time, the sensor fully utilizes the layered structure design of the pressure-sensitive layer, leveraging the synergistic response of the impedance adjustment of the piezoresistive layer and the capacitance characteristics of the ionized double layer to achieve measurement of vital signs signals with enhanced sensitivity. Finally, the independent resistance-temperature sensitivity characteristics of the ionized layer are used to measure changes in human body temperature, thereby realizing the non-contact multimodal vital sign sensing function of this invention.

[0011] Compared with the prior art, the beneficial effects of the present invention are reflected in: 1. This invention can be installed and attached to the surface of fabrics such as clothing and seat belts without directly contacting human skin. During the measurement process, depending on the installation mode, the sensor can work in a relaxed state and a compressed state respectively.

[0012] 2. Establish a non-contact measurement method based on a coplanar electrode structure. The sensing unit can be attached to the fabric surface, and the capacitive electrode does not need to be directly and tightly attached to the human skin. High-sensitivity vital sign signal monitoring is achieved through the edge electric field enhancement effect, which improves the skin-friendliness of wearable devices. 3. Under pressure, an electrical double-layer (EDL) effect is formed at the interface between the piezoresistive layer and the ionized layer, which increases the capacitance density. The synergistic effect of impedance adjustment of the piezoresistive layer and capacitance characteristics of the ionized double layer is used to achieve a stable and enhanced sensitivity of the tactile sensor. Attached Figure Description

[0013] Figure 1 This is an exploded view of the sensor structure of the present invention.

[0014] Figure 2 This is a schematic diagram of the induction electrode layer structure of the present invention.

[0015] Figure 3 This is a schematic diagram illustrating the principle of non-contact vital sign signal measurement by the sensor of this invention in a relaxed state.

[0016] Figure 4 This is a schematic diagram illustrating the principle of contact-type vital sign signal measurement by the sensor of this invention under pressure.

[0017] Figure 5 This is the equivalent circuit diagram of the piezoresistive-double-layer capacitance coordinated response of the sensor of the present invention under pressure.

[0018] In the diagram: 1. Sensing electrode layer, 2. Pressure-sensitive layer, 3. Piezoresistive layer, 4. Ionizing layer, 5. First interdigital sensing electrode, 6. Second interdigital sensing electrode, 7. Fabric, 8. Human body being tested. Detailed Implementation

[0019] The specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are for illustration and explanation only and are not intended to limit the scope of the present invention.

[0020] It should be noted that, unless otherwise specified, the embodiments and features described in the present invention can be combined with each other.

[0021] The present invention will now be described in detail with reference to the accompanying drawings and exemplary embodiments.

[0022] Example 1

[0023] This invention discloses a non-contact flexible sensor for vital sign detection based on piezoresistive-double-layer capacitance synergistic response, such as... Figure 1 As shown, the sensor includes a stacked sensing electrode layer 1 and a pressure-sensitive layer 2, with the upper surface of the pressure-sensitive layer 2 attached to the surface of the fabric 7 such as clothing or seat belt worn by the person being tested 8.

[0024] like Figure 2 As shown, the sensing electrode layer 1 consists of two centrally symmetrically distributed first interdigital sensing electrodes 5 and second interdigital sensing electrodes 6. The sensing electrodes are fabricated on the surface of the PI thin film using chemical deposition and etching processes. The upper surface of the sensing electrode layer 1 is in direct contact with the lower surface of the pressure-sensitive layer 2. Compared to a typical rectangular sensing electrode structure, the interdigital sensing electrode structure significantly increases the edge length of the electrode within the same coverage area, effectively enhancing the intensity and depth of the edge field, and contributing to higher sensitivity detection of vital signs over a wider measurement range. The output terminal of the first interdigital sensing electrode is denoted as S. m The output terminal of the second interdigital sensing electrode is denoted as S. n Simultaneously activate S m Output and S n The output terminal can measure the actual value of the sensing capacitance or sensing resistance between the two sensing electrodes.

[0025] like Figure 1As shown, the pressure-sensitive layer 2 is a layered structure design, consisting of a piezoresistive layer 3 and an ionized layer 4 from bottom to top. The piezoresistive layer 3 is a composite material prepared by using polydimethylsiloxane (PDMS) as a flexible substrate and carbon nanotubes (CNTs) as fillers. The composite material is a gradient porous structure with pore sizes ranging from 100μm to 10μm. Micropores at the 10μm level are prepared using perfluorotributylamine (C12F27N) as a sacrificial solution, and macropores at the 100μm level are prepared using sugar particles as pore-forming agents.

[0026] The ionization layer 4 is an ionized film obtained by mixing and curing polyvinyl alcohol (PVA) and ionic liquid (IL). When the piezoresistive layer 3 comes into contact with the ionization layer 4, in order to maintain charge neutrality, the charge on the surface of the piezoresistive layer 3 interacts with an equal amount of counterions in the ionization layer 4. Under the influence of electrostatic forces and van der Waals forces, they form an EDL effect at the contact interface, thereby significantly increasing the capacitance density to the µF / cm² level.

[0027] Specifically, the preparation method of pressure-sensitive layer 2 includes the following steps: First, a PDMS presol was prepared by mixing the base gel and curing agent at a ratio of 20:1. Then, C12F27N was dispersed into the PDMS presol at a concentration of 40 vol%, and stirred thoroughly for 5 min to prepare a PDMS-C12F27N emulsion. Next, CNTs were added to the PDMS-C12F27N emulsion at a weight percentage of 1.5% and stirred thoroughly. Sugar particles with a particle size of approximately 100 μm were mixed with the prepared PDMS-C12F27N emulsion at a volume ratio of 4:1 and poured into a mold. The mixture was then placed in a vacuum dryer and degassed at 30 °C for 30 min. Afterward, the mixture was cured in a vacuum drying oven at 80 °C for 2 hours. The cured composite material was then ultrasonically cleaned in deionized water for 6 hours to obtain a piezoresistive layer 3 with a gradient porous structure. The ionized layer 4 was prepared by mixing PVA and IL at a volume ratio of 4:1 and then ultrasonically cleaning at 30 °C for 30 min. After a degassing process of min, the film is cured in a vacuum drying oven at 30 ℃ for two hours to obtain an ion exchange membrane. The piezoresistive layer 3 and the ionization layer 4 are fixed by adhesive tape, and after cleaning and drying to remove moisture, the required pressure-sensitive layer 2 can be obtained.

[0028] The pressure-sensitive layer 2 is attached to the surface of fabrics 7 such as clothing and seat belts, and does not directly contact the surface skin of the human body 8 being tested.

[0029] Example 2

[0030] This invention discloses a non-contact multimodal vital sign sensing method. The sensing method employs a non-contact flexible sensor for vital sign detection with a piezoresistive-double-layer capacitive synergistic response. The sensing method and measurement principle include: (1) such as Figure 3 As shown, when the fabric 7, such as clothing or seatbelt, on which the sensor is mounted does not directly contact the skin surface of the human body 8 being tested, the sensor operates in a relaxed state. A portion of the edge electric field lines emitted from the first interdigital sensing electrode 5 of the coplanar electrode structure pass through the layered structure including the piezoresistive layer 3, the ionization layer 4, the air, and the human body 8 being tested, and flow towards the ground. The remaining electric field lines flow towards the second interdigital sensing electrode 6. Since the human body 8 is much larger than the two interdigital sensing electrodes, the first and second interdigital sensing electrodes 5 and 6 can be considered equivalent to two particles relative to the human body 8, and their charge is expressed as... Q m and Q n And without considering the case of the tested human body 8, Q m =- Q n = Q Assuming the human body being tested is a grounded conductor, the potentials on the surfaces of the interdigital induction electrodes 6 and 7 can be expressed as follows: (1) in, d This indicates the distance between the human body being tested (8) and the first and second interdigital sensing electrodes (5 and 6). a This represents half the distance between the two interdigital sensing electrodes. ε 0 is the dielectric constant of vacuum, Φ m and Φ n The initial potentials on the interdigital sensing electrodes 6 and 7 are given. According to equation (1), the change in potential difference between the first interdigital sensing electrode 6 and the second interdigital sensing electrode 7 can be calculated as follows: (2) in, V 0 mn This is the initial potential difference, which is assumed to be 0, and is calculated according to the formula for charge. Q = CV The change in the sensing capacitance can be given by equation (3): (3) In reality, the human body being tested (8) is not a directly grounded conductor. Therefore, the conversion relationship of mirrored charges between the conductor and the insulator is introduced, and the final equation for the change in capacitance can be expressed as: (4) in, ε t is the equivalent dielectric constant of the tested human body 8.

[0031] Changes in vital signs such as heart rate, pulse, and blood flow rate cause changes in the equivalent dielectric constant of the tested human body 8, resulting in a change in the number of electric field lines flowing from the tested human body 8 to the ground. The number of electric field lines flowing to the second interdigital sensing electrode 6 also changes accordingly, which is reflected in the change of the sensing capacitance value between the two interdigital sensing electrodes. By comparing the change in capacitance value with the calibrated change in sensing capacitance - vital sign signal (heart rate, pulse, blood flow, etc.), real-time detection of general vital sign signals can be achieved, and the occurrence of abnormal signals can be monitored.

[0032] (2) For example Figure 4 , Figure 5 As shown, when the fabric 7, such as clothing or seatbelt, on which the sensor is mounted, directly contacts the surface of human skin, the sensor operates under pressure. Changes in vital signs are transmitted through the fabric 7 to the sensor surface. Under pressure, an EDL effect is formed at the interface between the piezoresistive layer 3 and the ionized layer 4, resulting in an equivalent double-layer capacitance. C EDL The density improvement reaches the µF / cm² level, which is 3 to 5 orders of magnitude higher than that of traditional parallel-plate capacitors.

[0033] Meanwhile, due to the coplanar electrode structure design, an equivalent resistance is formed in parallel between the ionization layer 4 and the first interdigital sensing electrode 5 inside the piezoresistive layer 3. R com-1 and equivalent capacitance C air-1 Its equivalent impedance can be expressed as: (5) An equivalent resistance is formed in parallel between the ionization layer 4 and the second interdigital sensing electrode 7. R com-2 and equivalent capacitance C air-2 Its equivalent impedance can be expressed as: (6) Under external load, the movement of conductive particles inside or on the surface causes a rearrangement of the conduction path, resulting in an equivalent resistance. R com-1 and R com-2 Smaller, equivalent capacitance C air-1 and C air-2 Increase, two equivalent impedances and double-layer capacitance C EDL Since they are connected in series, the overall impedance of the sensor can be expressed as: (7) The corresponding sensor reactance is: (8) Therefore, the sensing capacitance between the first interdigital sensing electrode 6 and the second interdigital sensing electrode 7 is calculated as follows: (9) The synergistic response of the impedance adjustment of the piezoresistive layer 3 and the double-layer capacitance characteristics of the ionized layer 4 enables the measurement of vital signs with enhanced sensitivity. By measuring the sensing capacitance between the two interdigital sensing electrodes at this time and comparing it with the calibrated change in sensing capacitance - vital signs (heartbeat, pulse, blood flow, etc.), real-time detection of vital signs with higher sensitivity than in the relaxed state can be achieved.

[0034] (3) The temperature difference at the contact interface causes the ion mobility inside the ion layer to change, resulting in the resistance of the ion layer responding to the temperature change. At the same time, the temperature change does not significantly cause a significant change in the capacitance of the double layer interface. Therefore, by measuring the sensing resistance between the two interdigital sensing electrodes at this time and comparing it with the calibrated sensing resistance change-temperature curve, the decoupled measurement of human body temperature change can be achieved.

[0035] Finally, it should be noted that the above embodiments and descriptions are only used to illustrate the technical solutions of the present invention and not to limit it. Those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the disclosure of the technical solutions of the present invention, and all such modifications and substitutions should be covered within the protection scope of the claims of the present invention.

Claims

1. A non-contact flexible sensor for vital sign detection based on piezoresistive-double-layer capacitance synergistic response, characterized in that, The sensor comprises a stacked sensing electrode layer (1) and a pressure-sensitive layer (2). The upper surface of the sensing electrode layer (1) is in direct contact with the lower surface of the pressure-sensitive layer (2). The upper surface of the pressure-sensitive layer (2) is attached to the surface of a fabric (7) and does not directly contact the surface skin of the human body (8) being measured. During the measurement process, the sensor switches between a relaxed state and a compressed state according to the installation mode of the pressure-sensitive layer (2). The sensing electrode layer (1) is composed of a first interdigital sensing electrode (5) and a second interdigital sensing electrode (6) that are centrally symmetrically distributed. The sensing electrodes are processed on the surface of a PI film by chemical deposition and etching processes.

2. The non-contact flexible sensor for vital sign detection based on piezoresistive-double-layer capacitance synergistic response as described in claim 1, characterized in that, The pressure-sensitive layer (2) is designed with a layered structure, with a piezoresistive layer (3) and an ionization layer (4) arranged sequentially from bottom to top. The upper surface of the piezoresistive layer (3) is in direct contact with the lower surface of the ionization layer (4), and the lower surface of the piezoresistive layer (3) is in direct contact with the upper surface of the sensing electrode layer (1). The upper surface of the ionization layer (4) is attached to the surface of the fabric (7).

3. The non-contact flexible sensor for vital sign detection based on piezoresistive-double-layer capacitance synergistic response according to claim 2, characterized in that, The piezoresistive layer (3) is a composite material prepared by using polydimethylsiloxane as a flexible substrate and carbon nanotubes as fillers. The composite material is a gradient porous structure with a pore size of 100μm-10μm. Micropores of 10μm level are prepared by using perfluorotributylamine as a sacrificial solution and macropores of 100μm level are prepared by using sugar particles as pore-forming agents.

4. A non-contact flexible sensor for vital sign detection based on piezoresistive-double-layer capacitance synergistic response as described in claim 2, characterized in that, The ionized layer (4) is an ionized film obtained by mixing and curing polyvinyl alcohol and ionic liquid.

5. A non-contact, multimodal vital sign sensing method, characterized in that, The sensing method employs the non-contact flexible sensor for vital sign detection as described in claim 1, and the sensing method includes: When the fabric on which the sensor is installed does not directly contact the surface of human skin, the sensor operates in a relaxed state. A portion of the edge electric field lines emitted from the first interdigital sensing electrode (5) of the coplanar electrode structure pass through the layered structure including the piezoresistive layer (3), the ionization layer (4), the air and the human body being tested (8) and flow to the ground. The remaining electric field lines flow to the second interdigital sensing electrode (6). Changes in vital signs cause changes in the equivalent dielectric constant of the human body being tested (8), resulting in a change in the number of electric field lines flowing to the ground through the human body being tested (8). The number of electric field lines flowing to the second interdigital sensing electrode (6) also changes accordingly, which is reflected in the change of the sensing capacitance value between the two interdigital sensing electrodes. By comparing the change in capacitance value with the calibrated change in sensing capacitance - vital sign signal, real-time detection of general vital sign signals can be achieved, and the occurrence of abnormal signals can be monitored. When the fabric on which the sensor is mounted comes into direct contact with the surface of human skin, the sensor operates under pressure. Changes in vital signs are transmitted through the fabric to the sensor surface. Under pressure, a double-layer interface capacitance is formed at the interface between the piezoresistive layer (3) and the ionization layer (4), increasing the capacitance density to the µF / cm² level. Simultaneously, within the piezoresistive layer (3), an equivalent resistance and equivalent capacitance are formed in parallel between the ionization layer (4) and the first interdigital sensing electrode (5). Considered as a set of equivalent impedances, an equivalent resistance is also formed in parallel between the ionization layer (4) and the second interdigital sensing electrode (6). The resistance and equivalent capacitance are regarded as another set of equivalent impedances. The two equivalent impedances are connected in series with the double-layer capacitance. Under the action of external load, the movement of conductive particles inside or on the surface causes the conduction path to rearrange, the equivalent resistance decreases, and the equivalent capacitance increases. The impedance adjustment effect of the piezoresistive layer (3) and the double-layer capacitance characteristics of the ionized layer (4) realize the measurement of vital signs with enhanced sensitivity. The sensing capacitance between the two interdigital sensing electrodes is measured at this time and compared with the calibrated sensing capacitance change - vital signs. Thus, real-time detection of vital signs with higher sensitivity than in the relaxed state can be achieved.

6. The non-contact multimodal vital sign sensing method according to claim 5, characterized in that, The temperature difference between the skin surface of the human body (8) and the fabric (7) where the sensor is installed is transmitted to the ionization layer (4), causing a change in the internal ion mobility. This results in the resistance value of the ionization layer (4) responding to the temperature change. At the same time, the temperature change does not significantly cause a significant change in the capacitance of the double layer interface. By measuring the sensing resistance between the two interdigital sensing electrodes at this time and comparing it with the calibrated sensing resistance change-temperature curve, the decoupled measurement of human body temperature change can be achieved.

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