Metamaterial physiological sensor and methods of use

Abstract

The application relates to the technical field of sensors, and provides a metamaterial physiological sensor and a use method, wherein the metamaterial physiological sensor comprises a surface wave sensing structure, which is used for constraining a conventional electromagnetic wave into a surface electromagnetic wave, guiding a wavelength-compressed surface electromagnetic wave to transmit along a preset path, and interacting with human body tissue based on field interaction, and sensing physiological activities. The metamaterial physiological sensor and the use method provided by the application solve the problems of low sensitivity and easy interference of the prior art in dynamic scene physiological signal monitoring, and realize non-invasive, comfortable and high-precision non-contact physiological signal monitoring.

Description

Technical Field

[0001] This invention relates to the field of sensor technology, and more specifically, to a flexible sensor for monitoring physiological signals, and particularly to a metamaterial physiological sensor and its method of use. Background Technology

[0002] Traditional wireless sensors primarily rely on transmitting wireless signals into the surrounding space and capturing reflected signals from the human body to achieve non-contact monitoring. Under ideal conditions, these sensors can function effectively. However, in dynamic environments such as cars or airplane cabins, the relative motion between the body and the sensor, coupled with the weaker reflected signals from the human body compared to background objects, presents significant challenges for traditional wireless sensors.

[0003] Existing research suggests that constructing textile sensors may be a feasible approach to achieving non-contact measurement of human physiological signals. Current studies have demonstrated that advanced textile sensors can detect mechanical stimuli (such as strain and pressure), employing mechanisms such as resistance, capacitance, triboelectricity, or piezoelectric transduction to measure vital signs. Meanwhile, other studies have also confirmed the feasibility of conductive fabrics as electrophysiological sensors.

[0004] However, most traditional textile sensors are based on contact measurement principles, and the various frequency devices they use, such as antennas, waveguides, couplers, and resonators, lack non-contact health sensing capabilities. Furthermore, while some studies have proposed non-contact measurement schemes using textile sensors, these sensors are often designed to be quite rigid, limiting their placement near the body and making them susceptible to vibration and noise interference. Therefore, these sensors are typically only suitable for static environments and struggle to achieve ideal results in dynamic settings. Thus, designing a non-contact physiological sensor capable of stable operation in dynamic environments such as automobiles or airplane cabins remains a pressing challenge. Summary of the Invention

[0005] This invention provides a metamaterial physiological sensor and its usage method to address the shortcomings of existing technologies in monitoring physiological signals in dynamic scenarios, such as low sensitivity and susceptibility to interference.

[0006] This invention provides a metamaterial physiological sensor, comprising:

[0007] A surface wave sensing structure is used to constrain electromagnetic waves into surface electromagnetic waves and guide the surface electromagnetic waves to propagate along a preset path to interact with human tissues, and to sense physiological activities based on the interaction between the two fields.

[0008] The metamaterial physiological sensor provided by the present invention further includes:

[0009] The power conversion structure has one end as an input terminal for connecting to an externally input conventional electromagnetic wave, and the other end connected to the surface wave sensing structure for transmitting the conventional electromagnetic wave to the surface wave sensing structure and outputting the electromagnetic wave after the interaction between the fields.

[0010] The metamaterial physiological sensor provided by the present invention further includes:

[0011] The reflective surface structure is electrically connected to the power conversion structure, and is used to provide a ground plane for the power conversion structure and reflect the surface electromagnetic waves.

[0012] The metamaterial physiological sensor provided by the present invention further includes:

[0013] A flexible substrate is used to support the surface wave sensing structure, the power conversion structure, and the reflective surface structure, so that the metamaterial physiological sensor conformally fits the human body.

[0014] According to the present invention, a metamaterial physiological sensor is provided, wherein the metamaterial physiological sensor has a single-sided structure, and the reflective surface structure and the ground plane of the power conversion structure are integrated into one piece.

[0015] According to the present invention, a metamaterial physiological sensor is provided, wherein the metamaterial physiological sensor has a double-sided structure, and wherein the reflective surface structure is disposed on the side of the flexible substrate opposite to the surface wave sensing structure.

[0016] According to the present invention, a metamaterial physiological sensor is provided, wherein the surface wave sensing structure comprises:

[0017] A periodic conduction unit is used to modulate the wavelength of the conventional electromagnetic wave to confine the conventional electromagnetic wave into a deceptive surface plasmon polariton.

[0018] According to a metamaterial physiological sensor provided by the present invention, the surface wave sensing structure further includes a gradient transition unit disposed between the periodic conduction unit and the power supply conversion structure.

[0019] According to the present invention, a metamaterial physiological sensor is provided, wherein the feeding conversion structure is a coplanar waveguide structure, including a signal input end, a signal output end, a ground plane, and a connecting portion for connecting the surface wave sensing structure, wherein the signal input end and the signal output end are disposed at the edge of the coplanar waveguide structure.

[0020] According to a metamaterial physiological sensor provided by the present invention, a defect structure is provided on the grounding surface to extend the transmission path of the electromagnetic waves on the surface.

[0021] According to the present invention, a metamaterial physiological sensor is provided in which the surface wave sensing structure, the feeding conversion structure and the reflecting surface structure are made of a conductive material, and the conductive material is integrated on the flexible substrate through a predetermined process.

[0022] The present invention also provides a method of using the metamaterial physiological sensor as described above, comprising the following steps:

[0023] A conventional electromagnetic wave signal is transmitted to a surface wave sensing structure, and the conventional electromagnetic wave signal is converted into a surface electromagnetic wave through the surface wave sensing structure.

[0024] The surface wave sensing structure is used to guide the surface electromagnetic waves to propagate along a preset path that is attached to the human body, so as to interact with the human tissue.

[0025] Output target electromagnetic wave signal, wherein the target electromagnetic wave signal is an electromagnetic wave signal that carries target change signal caused by human physiological activity after passing through the interfield interaction, and the target change information includes at least one of phase change, amplitude change, energy change, and frequency shift change;

[0026] Target change information is extracted from the target electromagnetic wave signal to obtain information about human physiological activities.

[0027] The metamaterial physiological sensor and its usage method provided by this invention constrain electromagnetic waves into a highly concentrated surface wave form, allowing them to propagate along a preset path within the sensor. This fundamentally changes the far-field operating mode of traditional wireless sensors, which radiate energy into free space. Specifically, because the energy is effectively confined near the sensor surface, the sensor's resistance to motion artifacts and environmental clutter is greatly enhanced, enabling it to maintain signal stability even in dynamic and complex environments such as vehicle movement. Simultaneously, it ensures that the highly concentrated surface electromagnetic waves can interact efficiently and stably with human tissue, thereby significantly improving the detection sensitivity and signal-to-noise ratio for subtle physiological activities such as respiration and heartbeat. Therefore, this invention successfully solves the problems of low sensitivity and susceptibility to interference in dynamic scenarios, achieving non-invasive, comfortable, and highly accurate non-contact physiological signal monitoring. Attached Figure Description

[0028] To more clearly illustrate the technical solutions in this invention or related technologies, the accompanying drawings used in the description of the embodiments or related technologies will be briefly introduced below. Obviously, the accompanying drawings described below are some embodiments of this invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0029] Figure 1This is one of the structural schematic diagrams of the metamaterial physiological sensor provided by the present invention;

[0030] Figure 2 This is the second schematic diagram of the structure of the metamaterial physiological sensor provided by the present invention;

[0031] Figure 3 This is the third structural schematic diagram of the metamaterial physiological sensor provided by the present invention, wherein (a), (b), and (c) respectively show several pattern examples of a single-sided structure sensor;

[0032] Figure 4 This is the fourth structural schematic diagram of the metamaterial physiological sensor provided by the present invention, wherein (a) and (b) respectively show examples of two different double-sided structure sensors;

[0033] Figure 5 This is a flowchart illustrating the method of using the metamaterial physiological sensor provided by the present invention;

[0034] Figure 6 This is a schematic diagram of the sensor wearing and physiological sensing signal provided by the present invention, wherein (a) shows the sensor wearing diagram and sensing principle, (b) takes digital embroidery as an example to show the sensor integrated manufacturing process and various parts of the sensor structure, (c) shows the sensor usage examples of clothing of different thicknesses and different wearing positions, and (d) shows the sensor data processing principle.

[0035] Figure 7 This is a schematic diagram of the design optimization of the conductor part of the metamaterial physiological sensor provided by the present invention. (a) shows a schematic diagram of a metamaterial waveguide and geometric design parameters. (b) shows the dispersion curves corresponding to different q values. (c) shows the relationship between the wavenumber β of the fabric substrate and the fill factor q for different fabric substrates. (d) and (e) respectively show the schematic diagram of the impedance matching transition section composed of a gradient corrugated hollow strip and a horn-shaped grounding and the improvement effect on the overall sensor performance. (f) shows the relationship between transmission loss and fabric conductivity under different q values. (g) shows the sensing mechanism and system design schematic diagram. (h) and (i) respectively show the waveforms of respiratory and heartbeat signals within one cycle.

[0036] Figure 8 This is a schematic diagram of the design optimization of the dispersive properties of the metamaterial physiological sensor provided by the present invention, wherein (a) shows the influence of parameter h on the dispersive properties, and (b) shows the influence of parameter p on the dispersive properties;

[0037] Figure 9 This is a schematic diagram illustrating the impact of folding and bending on the transmission efficiency of the metamaterial physiological sensor provided by this invention.

[0038] Figure 10This is a schematic diagram of the relevant test results of the metamaterial physiological sensor provided by the present invention during vehicle testing. (a) and (b) show the comparison between the extracted respiratory rate and heart rate and the reference measurement values, respectively. (c) shows the recorded vehicle speed data. (d) shows the recorded triaxial accelerometer data. (e) shows the respiratory interval (RBI) estimation error in the entire experiment. Detailed Implementation

[0039] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this invention. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0040] In recent years, with the increasing demand for health monitoring, sensing technologies that can acquire human physiological signals (such as breathing and heartbeat) in real time and conveniently have received widespread attention, especially showing great application potential in fields such as vehicle safety, sports and health, medical monitoring and smart homes.

[0041] Currently, the main technological approaches to physiological signal monitoring include contact and non-contact measurement. Contact sensors, such as flexible sensors based on piezoelectric, piezoresistive, or capacitive effects, and electrode sensors used to measure electrocardiogram (ECG) signals, can achieve high measurement accuracy, but they generally require the sensor to maintain stable and close physical contact with human skin. This can cause discomfort during use, is unfriendly to people with sensitive skin, and is difficult to achieve or affect the user experience in certain scenarios (such as through clothing or during sleep), limiting the convenience and universality of their applications.

[0042] To overcome the limitations of contact measurement, non-contact sensing technologies have emerged. Among them, wireless sensing based on radio frequency (RF) and microwaves is a mainstream solution. These technologies typically achieve long-distance, non-contact monitoring of physiological activities by emitting electromagnetic waves into space and receiving signals reflected or modulated by the human body. However, traditional far-field wireless sensors face significant technical challenges in practical applications:

[0043] (1) Motion interference sensitivity: In dynamic environments (such as moving vehicles or moving cabins), changes in the relative position between the sensor and the human body, as well as large-scale movements of the body, will produce strong motion artifacts. The signal strength is much greater than that caused by weak physiological activities such as breathing and heartbeat, resulting in a very low signal-to-noise ratio and difficulty in accurately extracting effective physiological information.

[0044] (2) Environmental clutter interference: The electromagnetic waves emitted by the sensor will cover a large spatial range. The reflections from other objects in the environment (such as car seats, passengers, metal parts, etc.) will form strong clutter interference, further drowning out the weak physiological signals from the target human body.

[0045] To combine the fit of flexible sensors with the contactless advantages of wireless sensing, researchers have attempted to fabricate radio frequency (RF) devices (such as antennas and transmission lines) on flexible or fabric substrates to develop flexible contactless RF sensors. While these approaches improve wearing flexibility to some extent, they still have the following inherent drawbacks:

[0046] First, in order to ensure radio frequency performance, some designs still contain rigid or semi-rigid functional structures, which makes it difficult to conformally fit the human body or irregular surfaces. They are also prone to noise in vibration environments, making them mainly suitable for monitoring in static scenarios, but not effective in dynamic scenarios.

[0047] Secondly, traditional flexible radio frequency sensors (such as microstrip line structures) have poor energy confinement of electromagnetic waves, with most of the energy radiating into free space, resulting in insufficient sensitivity to the perception of subtle physiological activities of the human body.

[0048] In response, this invention provides a seatbelt-integrated metamaterial physiological sensor and its usage method. This sensor can achieve non-contact measurement, avoiding the discomfort and limitations of traditional contact sensors, and also has excellent flexibility and conformal capabilities, making it easy to integrate into everyday items such as seatbelts. At the same time, it can effectively suppress motion interference and environmental clutter in dynamic environments, thereby achieving high sensitivity and high stability monitoring of weak physiological activities such as breathing and heartbeat in complex dynamic scenarios such as vehicles, thus overcoming the aforementioned defects.

[0049] Figure 1 This is one of the structural schematic diagrams of the metamaterial physiological sensor provided by the present invention, such as... Figure 1 As shown, this metamaterial physiological sensor includes:

[0050] The surface wave sensing structure 10 is used to constrain conventional electromagnetic waves into surface electromagnetic waves and guide the surface electromagnetic waves to propagate along a preset path to interact with human tissues and sense physiological activities based on the interaction.

[0051] Specifically, the metamaterial physiological sensor provided in this embodiment of the invention may include a surface wave sensing structure, which is the core functional part for realizing physiological signal sensing. Its main function is to convert conventional electromagnetic waves into a special type of electromagnetic wave, namely surface electromagnetic waves, and guide these surface electromagnetic waves to propagate along a pre-defined path on the sensor surface. These surface electromagnetic waves differ from conventional far-field electromagnetic waves that radiate freely into space (such as radio waves radiated by an antenna). They are electromagnetic waves confined to a very small spatial range near the surface of the sensing structure, with their energy highly concentrated on the surface. When a flexible substrate (such as a seatbelt) integrating this sensor is fitted to the human body, the electromagnetic field of the surface electromagnetic waves couples and interacts with adjacent human tissues (such as the skin, fat, and muscle tissue on the surface of the chest and abdomen). Human physiological activities, such as the chest rise and fall caused by breathing and the vibration of human tissues caused by heartbeat, cause periodic, minute changes in the contour of the human body surface and the corresponding tissue dielectric constant. These minute changes modulate the transmission characteristics of the propagating surface electromagnetic waves, such as phase, amplitude, frequency shift, and energy. Therefore, by detecting changes in the electromagnetic waves emitted from this surface (such as phase changes, amplitude changes, frequency shift changes, and energy changes), information about human physiological activities can be reflected. It should be understood that the aforementioned sensing refers to the process of capturing these changes through inter-field interactions.

[0052] The metamaterial physiological sensor provided in this invention uses a surface wave sensing structure to confine electromagnetic waves as highly concentrated surface waves propagating along a preset path on the sensor. This fundamentally changes the far-field operating mode of traditional wireless sensors, which radiate energy into free space. Specifically, because the energy is effectively confined near the sensor surface, the anti-interference capability against motion artifacts and environmental clutter is greatly enhanced, allowing the sensor to maintain signal stability even in dynamic and complex environments such as vehicle movement. Simultaneously, it ensures that the highly concentrated surface electromagnetic waves can interact efficiently and stably with human tissue, thereby significantly improving the detection sensitivity and signal-to-noise ratio for weak physiological activities such as respiration and heartbeat. Therefore, this invention successfully solves the problems of low sensitivity and susceptibility to interference in dynamic scenarios in existing technologies, achieving non-invasive, comfortable, and high-precision non-contact physiological signal monitoring.

[0053] Based on any of the above embodiments Figure 2 This is the second schematic diagram of the structure of the metamaterial physiological sensor provided by the present invention, as shown below. Figure 2 As shown, this metamaterial physiological sensor also includes:

[0054] The power conversion structure 20 has one end as an input terminal for connecting to an externally input conventional electromagnetic wave, and the other end is connected to the surface wave sensing structure for transmitting the conventional electromagnetic wave to the surface wave sensing structure and outputting the electromagnetic wave after the inter-field interaction.

[0055] The reflective surface structure 30 is electrically connected to the feed conversion structure and is used to provide a ground plane for the feed conversion structure and reflect the surface electromagnetic waves.

[0056] A flexible substrate 40 is used to support the surface wave sensing structure, the power conversion structure, and the reflective surface structure, so that the metamaterial physiological sensor conformally fits the human body.

[0057] It should be noted that the metamaterial physiological sensor provided in the embodiments of the present invention may also include a power conversion structure, a reflective surface structure and a flexible substrate. These structures are optional, while the surface wave sensing structure is a necessary core structure for the sensor.

[0058] Specifically, the flexible substrate serves as the platform supporting the entire sensor. Here, flexibility refers to the substrate's physical properties of being bendable, foldable, or conformally fitted onto curved surfaces. This property allows the entire sensor to fit tightly and conformally onto the user's body surface, for example, by integrating it into a car seatbelt or the leather / fabric surface of a car seat. This conformal fit is crucial for achieving high signal-to-noise ratio and motion-interference-resistant monitoring, as it ensures that the relative position between the sensor and the human body remains essentially fixed, effectively suppressing noise introduced by significant body movements (such as changes in driver posture). This is a significant advantage compared to traditional fixed wireless sensors. The material of this flexible substrate can include, but is not limited to, various fabrics (such as canvas, polyester, cotton, etc.) or other flexible materials; this embodiment of the invention does not specifically limit this.

[0059] The surface wave sensing structure, feed conversion structure, and reflector structure are all integrated on a flexible substrate. The feed conversion structure acts as a bridge connecting the external signal source / processing unit and the surface wave sensing structure. It has at least two functions: signal input and signal output. Specifically, the feed conversion structure receives conventional electromagnetic waves generated by an external radio frequency signal source (e.g., a radio generation module or development board). Here, conventional electromagnetic waves can be understood as continuous or pulsed electromagnetic wave signals of a predetermined frequency and modulation method (including unmodulated) propagating in a standard transmission line (such as a coaxial line or other open, semi-open, or closed wire harness or conductive structure capable of conducting electromagnetic waves). One of the key functions of the feed conversion structure is to efficiently transmit this conventional electromagnetic wave to the surface wave sensing structure.

[0060] After receiving a conventional electromagnetic wave transmitted by the feed conversion structure, the surface wave sensing structure confines the conventional electromagnetic wave into a wavelength-compressed surface electromagnetic wave and guides it to propagate along a flexible substrate attached to the human body to interact with the human tissue. Subsequently, the surface electromagnetic wave carrying information about human physiological activities (such as phase, amplitude, frequency modulation, or energy alteration) propagates along the surface wave sensing structure, passes through the feed conversion structure again, and is output by the feed conversion structure to an external signal processing unit for demodulation and analysis.

[0061] The reflector structure is electrically connected to the feed conversion structure, typically serving as its ground plane. It primarily functions in two ways: first, it provides grounding, offering a stable potential reference for the feed conversion structure (e.g., when it's a coplanar waveguide or other transmission line structure), which is fundamental to ensuring stable and controllable electromagnetic wave transmission; second, it reflects electromagnetic waves, confining and guiding energy that might otherwise radiate outwards towards the human body, significantly enhancing the interaction between the electromagnetic waves and the human body. This, in turn, improves the sensor's sensitivity and signal-to-noise ratio, making the detection of weak signals more accurate and reliable.

[0062] The working principle of the metamaterial physiological sensor provided in this invention is as follows: During operation, an external device inputs a continuous wave or pulsed electromagnetic wave signal of a specific frequency through a feeding conversion structure. This signal is converted into a surface electromagnetic wave and guided by a surface wave sensing structure, propagating along a path conforming to the human body. During propagation, the electromagnetic wave interacts with the human body, and its phase (or amplitude, frequency shift, energy, etc.) is modulated by physiological activities such as breathing and heartbeat. The modulated electromagnetic wave signal is finally output through the feeding conversion structure. The external signal processing unit extracts the physiological state signal that changes over time by comparing the differences between the input and output signals, and demodulates and separates physiological signals such as breathing and heartbeat. Ultimately, this can be used to calculate key physiological indicators such as respiratory rate, heart rate, and heart rate variability, achieving non-contact continuous monitoring of the user's health status (such as fatigue driving monitoring).

[0063] The metamaterial physiological sensor provided in this invention uses a surface wave sensing structure to confine electromagnetic waves as highly concentrated surface waves propagating along a preset path on the sensor. This fundamentally changes the far-field operating mode of traditional wireless sensors, which radiates energy into free space. This near-field sensing mechanism brings three major advantages: First, because the energy is effectively confined near the sensor surface, the anti-interference ability against motion artifacts and environmental clutter is greatly enhanced, allowing the sensor to maintain signal stability even in dynamic and complex environments such as vehicle movement. Second, combined with a flexible substrate that conformally fits the human body, it ensures that the highly concentrated surface electromagnetic waves can interact efficiently and stably with human tissue, thereby significantly improving the detection sensitivity and signal-to-noise ratio of weak physiological activities such as breathing and heartbeat. Third, the reflective surface structure, while providing stable grounding for the power conversion structure, further enhances the confinement and reflection of surface electromagnetic waves, ensuring signal integrity and sensing efficiency.

[0064] Based on any of the above embodiments Figure 3 This is the third schematic diagram of the metamaterial physiological sensor provided by the present invention, as shown below. Figure 3 As shown, the metamaterial physiological sensor has a single-sided structure, wherein the reflective surface structure 30 and the ground plane of the power conversion structure 20 are integrated into one unit.

[0065] Specifically, in one embodiment, to simplify the sensor structure and manufacturing process, the metamaterial physiological sensor can be designed as a single-sided structure. Figure 3 (a) Figure 3 (b) Figure 3 (c) shows several pattern examples of single-sided sensor structures. Here, a single-sided structure refers to a structure where all conductive parts of the sensor (i.e., the surface wave sensing structure, the feed conversion structure, and the reflective surface structure) are fabricated on the same surface of a flexible substrate. In this design, the ground plane of the reflective surface structure and the feed conversion structure are physically the same structure; they are integrated as a single unit. It should be understood that in a single-sided structure design, the reflective surface structure primarily serves as a grounding element, and the sensor pattern (i.e., the conductive parts) can be integrated onto the side of the flexible substrate (such as a seatbelt) facing away from the human body.

[0066] For example, such as Figure 3As shown in (a), the feed conversion structure 20 can be in the form of a coplanar waveguide. A typical coplanar waveguide includes a signal transmission strip in the middle (for connecting the signal input terminal 21, the signal output terminal 22, and the surface wave sensing structure 10), and large-area conductors on both sides of the signal transmission strip, i.e., ground planes 23. In this embodiment of the invention, these two or one (the specific shape depends on the design) surround the ground plane 23 of the signal path, and simultaneously serve as a reflective surface structure. When surface electromagnetic waves propagate on the surface wave sensing structure 10, this integrated ground / reflective surface structure can effectively confine the electromagnetic field energy in the area between the sensor and the human body, allowing it to fully interact with the human tissue, thereby realizing the reflection and guidance of surface waves.

[0067] Understandably, with this single-sided integrated structure, all conductor patterns of the sensor can be completed in a single processing step, such as by screen printing (using conductive silver paste), copper foil etching, or digital embroidery on a single side of a flexible substrate.

[0068] In this embodiment of the invention, by integrating the reflective surface structure and the ground plane of the power conversion structure into an integrated single-sided structure, the manufacturing process of the sensor is significantly simplified, the production cost is reduced, and the good flexibility and conformality of the sensor are maintained. At the same time, the functions of grounding and electromagnetic wave reflection are effectively realized, ensuring the performance of physiological sensing.

[0069] Based on any of the above embodiments Figure 4 This is the fourth schematic diagram of the metamaterial physiological sensor provided by the present invention, as shown below. Figure 4 As shown, the metamaterial physiological sensor has a double-sided structure, wherein the reflective surface structure 30 is disposed on the side of the flexible substrate 40 opposite to the surface wave sensing structure 10.

[0070] Specifically, in another embodiment, in order to obtain better shielding performance and signal directionality, the metamaterial physiological sensor can be designed as a double-sided structure. Figure 4 (a) and Figure 4 (b) illustrates two different examples of bifacial sensor structures. Here, bifaciality refers to a sensor whose conductive components are fabricated on two opposing surfaces of a flexible substrate. Specifically, the surface wave sensing structure and the feed conversion structure can be positioned on one surface of the flexible substrate (referred to as the front or sensing surface), while the reflective surface structure is separately positioned on the other surface of the flexible substrate opposite to the surface wave sensing structure (referred to as the back). It should be understood that in a bifacial design, the front of the flexible substrate refers to the side facing (close to) the human body, and the back refers to the side of the flexible substrate away from the human body.

[0071] like Figure 4 As shown in (a) and (b), the front circuit (i.e., the sensing surface) includes a surface wave sensing structure 10 for guiding and sensing, and a feed conversion structure 20 for signal transmission and reception. The other side of the flexible substrate, i.e., the reverse circuit, serves as a reflective surface structure 30. This reflective surface structure 30 can be electrically connected to the ground plane of the feed conversion structure 20 in the front circuit through conductive vias, edge covering, or other electrical connection methods to provide a uniform ground potential.

[0072] When this dual-sided sensor is integrated into a seatbelt and used in close contact with the human body, the front side containing the surface wave sensing structure is close to the human body for inter-field interaction, while the reflective surface structure is located on the side of the seatbelt away from the human body. This ensures that electromagnetic wave energy is concentrated in the contact area between the front of the sensor and the human body, while the back of the seatbelt has almost no electromagnetic waves, thus avoiding the radiation and leakage of electromagnetic waves in the environment.

[0073] Based on any of the above embodiments, the surface wave sensing structure 10 includes:

[0074] The periodic conduction unit 11 is used to control the wavelength of the conventional electromagnetic wave in order to confine the conventional electromagnetic wave into a deceptive surface plasmon polariton.

[0075] A gradual transition unit 12 is disposed between the periodic conduction unit 11 and the power supply conversion structure 20 to achieve impedance matching between the periodic conduction unit 11 and the power supply conversion structure 20.

[0076] Specifically, in order to effectively constrain and guide surface electromagnetic waves and ensure that the signal can be efficiently coupled from the feed conversion structure to the surface wave sensing structure, the surface wave sensing structure may include two parts: a periodic conduction unit and a gradient transition unit. The periodic conduction unit is the core structure of the surface wave sensing structure, while the gradient transition unit is an optional structure.

[0077] like Figure 3 and Figure 4As shown, the periodic conduction unit 11 is the main part of the surface wave sensing structure 10, and its core function is to modulate the wavelength of the electromagnetic wave propagating along it. This unit consists of a series of conductive geometric patterns arranged in a specific periodic repeating pattern. This periodic structure can change the dispersion characteristics of the surface electromagnetic wave it carries, making it exhibit behavior similar to surface plasmon polaritons in the optical frequency band, and therefore is called a deceiving surface plasmon polariton (SPP) in the microwave frequency band. A key characteristic of deceiving surface plasmon polaritons is that their wave vector (or wave number β) is greater than the wave vector (k0) of free space light waves at the same frequency, which means that their wavelength is compressed and the energy is more tightly bound to the surface of the periodic conduction unit.

[0078] To more clearly elucidate the technical principle of using periodic conductive units to achieve deceptive surface plasmon confinement, its physical basis lies in the manipulation of structural dispersion relations. Specifically, this metamaterial structure supports a surface plasmon-like dispersion relation with a wavenumber β, in the form of:

[0079]

[0080] in It is the free space wavenumber. Represents the angular frequency of electromagnetic waves. It is a fundamental physical constant that represents the speed at which electromagnetic waves propagate in free space without any medium. It is the dielectric constant. The dispersion curve lies in the light ray ( To the right of ), at the surface plasma frequency The frequency is asymptotic. In the microwave band, by designing the geometry of periodic conductive units, the equivalent plasma frequency can be simulated. This allows for the deception of surface plasmon polarons. The wavenumber in the dispersion relation... The dispersion relation can be adjusted by changing the geometric parameters of the unit cells (such as the fill factor q), thus obtaining a set of dispersion curves for deceptive surface plasmon polariton structures with different q values. Furthermore, the material properties of the flexible substrate also affect the dispersion relation; to evaluate the influence of the substrate material, the material of the fabric substrate was specified as ε. 毡 =1.22, ε 棉 =1.6, ε 涤纶 =1.9 and ε 帆布 =2.12. Where, ε 毡 ε represents the dielectric constant of felt fabric. 棉 ε represents the dielectric constant of cotton fabric. 涤纶 ε represents the dielectric constant of polyester. 帆布 This represents the dielectric constant of the canvas.

[0081] It is precisely this strong field confinement characteristic achieved through the engineering of periodic structures (i.e., wavelength compression and energy more tightly bound to the surface of the periodic conductive unit) that makes electromagnetic waves extremely sensitive to minute changes in the near-field environment (i.e., the adjacent human tissue) (such as the chest and abdominal cavity fluctuations caused by breathing and heartbeat), thereby achieving highly sensitive physiological sensing. Those skilled in the art will understand that by analyzing the above dispersion relation, the geometric parameters of the periodic conductive unit (such as period p, fill factor q, dimensions a and h, and unit shape, etc., refer to...) can be determined. Figure 7 (a) or Figure 8 (a) and the substrate material are selected and optimized to achieve the desired wavelength compression and field confinement effects in the required operating frequency band (e.g., the 2.4-2.5 GHz ISM band), specifically as follows: Figure 7 (b) and Figure 8 As shown.

[0082] like Figure 3 and Figure 4 As shown, the gradient transition unit 12 acts as a bridge, positioned between the periodic conduction unit 11 and the feed conversion structure 20. Since the feed conversion structure 20 transmits conventional electromagnetic waves with a small wave vector, while the periodic conduction unit 11 supports surface electromagnetic waves with a large wave vector, there is a significant wave vector mismatch and impedance mismatch between the two. Direct connection would result in severe signal reflection and ineffective energy transmission. The gradient transition unit 12, through its gradually changing geometry, achieves a smooth transition from the characteristic impedance of the feed conversion structure 20 to the equivalent impedance of the periodic conduction unit 11, while also achieving a smooth wave vector conversion.

[0083] In this embodiment of the invention, the surface wave sensing structure is designed as a combination of periodic conduction units and gradient transition units. The periodic conduction units generate strong field-confined deceptive surface plasmon polaritons to improve sensing sensitivity, and the gradient transition units solve the problem of low signal coupling efficiency. Together, these technologies ensure that the sensor can efficiently and sensitively perform non-contact sensing of human physiological activities.

[0084] Based on any of the above embodiments, the shape of the periodic conduction unit 11 can be any shape in the metasurface unit structure capable of generating or transmitting surface electromagnetic waves, such as a serpentine structure, a curved structure, a fence structure, or a comb structure, etc. The embodiments of the present invention do not specifically limit this.

[0085] Specifically, the geometry of the periodic conduction unit is a key factor determining its electromagnetic properties, but it is not the only one. To achieve effective excitation and guidance of deceiving surface plasmon polaritons, while considering the feasibility of manufacturing processes and the flexibility of the sensor, the individual periodic shape of the periodic conduction unit can be set to any shape capable of generating or transmitting surface magnetic waves, such as serpentine structures, curved structures, fence structures, or comb structures, etc. Figure 3 or Figure 4 As shown.

[0086] These structures all achieve wave vector amplification by introducing periodic geometric modulation onto simple conductive strips. It should be noted that the shapes listed are not exhaustive. Those skilled in the art can design any other periodic geometric pattern capable of supporting deceiving surface plasmon polariton modes based on dispersion relation analysis theory; all such patterns fall within the scope of this invention. The specific shape chosen can be determined based on a comprehensive consideration of the application scenario, manufacturing process, cost, and performance indicators such as flexibility and sensitivity.

[0087] The embodiments of the present invention provide a variety of feasible specific shapes for the periodic conduction unit, which greatly enhances the flexibility and selectivity of sensor design. This allows for the flexible design and optimization of sensor patterns based on different flexible substrate materials and performance requirements, in order to achieve the best physiological signal sensing effect.

[0088] Based on any of the above embodiments, the power supply conversion structure 20 is a coplanar waveguide structure, including a signal input terminal 21, a signal output terminal 22, a ground plane 23, and a connection portion for connecting the surface wave sensing structure 10. The signal input terminal 21 and the signal output terminal 22 are disposed at the edge of the coplanar waveguide structure.

[0089] Specifically, to facilitate connection with external standard RF devices such as coaxial cables and to achieve efficient signal input and output, the feed conversion structure is preferably a coplanar waveguide structure. For example... Figure 3 (a) Figure 3 (b) Figure 3 As shown in (c), the coplanar waveguide structure includes a signal input terminal 21, a signal output terminal 22, a ground plane 23, and a connection portion (not shown) for connecting to the surface wave sensing structure 10.

[0090] The signal input and signal output terminals are signal transmission ports of the coplanar waveguide, which are mounted on the coplanar waveguide structure (i.e., coplanar with it). The signal input terminal is used to receive conventional electromagnetic wave signals generated by an external radio frequency signal source, while the signal output terminal is used to output electromagnetic wave signals carrying physiological information after the sensing process to the signal receiving and processing unit.

[0091] The ground plane is an important component of the coplanar waveguide. It is located on both sides of the signal input and output terminals or surrounds the signal path, and lies in the same plane as the signal path. The ground plane provides a stable zero-potential reference for the entire feed structure, which is fundamental to ensuring stable electromagnetic wave transmission.

[0092] The connection section is a crucial area in the power supply conversion structure, physically connecting the signal input / output terminals and the surface wave sensing structure.

[0093] Based on any of the above embodiments, a defect structure is provided on the ground plane 23 to extend the transmission path of the surface electromagnetic waves.

[0094] In a preferred embodiment, to extend the effective sensing path of surface electromagnetic waves, thereby accumulating more phase (or amplitude, frequency shift, energy, etc.) changes and improving sensor sensitivity, a defect structure can be introduced on the grounding surface. Here, the defect structure refers to a deliberately created non-conductive region on the originally continuous and flat grounding surface, such as a slot or a portion being removed. By introducing such a defect waveguide structure, the electromagnetic field distribution in the feed conversion structure region can be altered, forcing the surface electromagnetic waves to propagate along a longer, pre-defined meandering path, rather than a simple straight-line propagation. This is equivalent to increasing the effective length of the sensor within a limited physical space, allowing for more sufficient interaction time and space between the surface waves and human tissue, which is particularly advantageous for capturing weak physiological signals (such as heartbeats).

[0095] In this embodiment of the invention, by using a coplanar waveguide with a defective structure as the feed conversion structure, not only is a convenient interface compatible with external standard radio frequency equipment provided, but also the sensing path of surface electromagnetic waves is cleverly extended by introducing a defective structure on the ground plane, thereby effectively improving the detection sensitivity and signal-to-noise ratio of physiological signals without increasing the overall size of the sensor.

[0096] Based on any of the above embodiments, the shape of the feed conversion structure 20 is a common semi-open waveguide structure, such as gradient ripple, hollow strip, horn shape, triangle, etc., and the shape of the reflective surface structure 30 is a common shape that can reflect surface electromagnetic waves, such as rectangle, triangle, strip, etc. The embodiments of the present invention do not specifically limit this.

[0097] Specifically, the shape of the power supply conversion structure can be flexible and diverse, including gradient corrugations, hollow strips, horn shapes, triangles, etc. The selection of these shapes and the optimization of specific dimensions can be precisely calculated and designed using electromagnetic simulation software (such as CSTStudio Suite) to obtain the best transmission characteristics within the target operating frequency band.

[0098] Similarly, the design of the reflective surface structure is also flexible. In sensors with a double-sided structure, the reflective surface structure located on the back of the flexible substrate can be rectangular, triangular, strip-shaped, or any other shape that can effectively cover the sensing circuit area below.

[0099] The embodiments of this invention further highlight the high degree of flexibility and customizability in specific designs by listing various feasible shapes for the feed conversion structure and the reflective surface structure. Designers can freely combine and select the most suitable geometry according to performance requirements, cost, manufacturing process, and application environment to achieve the optimal design of the sensor.

[0100] Based on any of the above embodiments, the surface wave sensing structure 10, the power supply conversion structure 20, and the reflective surface structure 30 are made of conductive material, and the conductive material is integrated onto the flexible substrate 40 through a preset process.

[0101] Specifically, the embodiments of the present invention provide a detailed description of the manufacturing process of the metamaterial physiological sensor described in any of the foregoing embodiments. The surface wave sensing structure, the feed conversion structure, and the reflective surface structure of the sensor are all conductive patterns made of conductive materials. These patterns need to be precisely fabricated and integrated onto a flexible substrate through specific manufacturing processes to form a complete and flexible electronic device.

[0102] The preset process is not singular, but includes a variety of technologies applicable to flexible electronics manufacturing. Designers can choose based on factors such as cost, precision, substrate material, and production scale. For example, the preset process can be at least one or a combination of printing, thermoplastic, etching, embossing, and embroidery processes. This embodiment of the invention does not specifically limit this.

[0103] Printing is a common additive manufacturing method. Specifically, roll-to-roll printing technology is used, where conductive ink (such as conductive silver paste) is continuously printed onto a roll of flexible substrate (such as fabric or plastic film) according to a pre-set sensor pattern using methods such as screen printing or inkjet printing. The ink is then cured to form conductive pathways. This method offers high production efficiency, low cost, and is suitable for large-scale production.

[0104] Thermoplastic processing refers to the process of heating thermoplastic materials to a softened state and then shaping them under pressure or vacuum. This process mainly involves two basic steps: heating and shaping. In the heating stage, the plastic sheet is heated to a suitable temperature and then shaped in a mold, typically using a vacuum or air pressure to generate the necessary force. Thermoplastic materials are characterized by their ability to be repeatedly heated and reshaped, making them suitable for rapid molding and recycling. Common thermoplastic processes include injection molding, extrusion molding, and rotational molding.

[0105] Thermoplastic processes are often used in combination with other processes. For example, a sensor conductor pattern can be first prepared on a thermoplastic film (such as PI film, PVC film, or film made of polystyrene, cellulose acetate butyrate, ABS, acrylic, polypropylene, polyethylene, etc.) using printing or etching processes. This film is then placed on a final flexible substrate (such as seatbelt fabric), and the thermoplastic film is softened and firmly bonded to the substrate by heating and applying pressure. This combined process can effectively transfer intricate circuit patterns to rough fabric surfaces that are not suitable for direct printing or etching.

[0106] Etching is a traditional subtractive manufacturing method. Copper etching integration can be used, where unwanted copper is removed from a flexible substrate covered with copper foil through photolithography, masking, and chemical etching, leaving only the designed sensor conductor pattern. This process can be performed directly on the final substrate, or etching can be completed first on a thin film such as PI, followed by transfer via thermoplastic processing. Etching offers high precision and good conductivity.

[0107] Printing processes (such as 3D printing) can extrude conductive paste or molten conductive material through a specific printhead, directly stacking it layer by layer on a flexible substrate to create a three-dimensional conductive pattern. This method is highly flexible and suitable for rapid prototyping and personalized customization.

[0108] Embroidery is an innovative manufacturing method particularly suitable for textile substrates. Digital embroidery technology can be used to weave patterns onto polyester fabric substrates, such as seat belts, to fabricate the various parts of a metamaterial sensor. Specifically, the sensor pattern is first designed using commercial software (such as PE-DESIGN 10). Then, conductive wires (such as Shieldex conductive wires) are loaded into a computer-controlled sewing or embroidery machine (such as Brother NV 180). The machine automatically and precisely embroiders the conductive wires onto a flexible substrate (such as polyester fabric) according to the design pattern. A conductive epoxy resin adhesive coating is then used to connect the conductive lines to an SMA connector (a sub-miniature coaxial cable connector, named after the Sub-Miniature A connector). The digital control working area of ​​the embroidery machine is 10cm. At a distance of 10cm, a repeated digital embroidery process is performed to assemble a structure by sequentially connecting embroidered fragments. This method seamlessly integrates sensor functionality with textiles, preserving the fabric's original softness and breathability, while offering excellent durability and wearability.

[0109] The various manufacturing processes provided by the embodiments of the present invention endow metamaterial physiological sensors with strong manufacturing flexibility and scenario adaptability, enabling them to be conveniently and reliably integrated into various flexible items (especially textiles such as seat belts).

[0110] Based on any of the above embodiments, the conductor material includes, but is not limited to, at least one of conductive silver paste, copper, and conductive wire, and the material of the flexible substrate 40 includes, but is not limited to, at least one of canvas, felt fabric, polyester, cotton fabric, polyimide film, or thermoplastic plastic.

[0111] Specifically, the conductor material, i.e. the material used to construct the surface wave sensing structure, the power supply conversion structure, and the reflective surface structure, can be any conductive material, such as conductive silver paste, copper, conductive wire, etc., and the embodiments of the present invention do not specifically limit it.

[0112] Conductive silver paste is a commonly used conductive ink in printing processes, possessing excellent conductivity and printability. Copper, usually existing in the form of copper foil, is the preferred material for etching processes due to its superior conductivity and relatively low cost. Conductive thread is a specialized material for digital embroidery, combining conductive metals (such as silver and copper) with fiber materials, achieving both conductivity and the flexibility of thread.

[0113] The materials for the flexible substrate are also widely selectable, including but not limited to common textiles such as canvas, felt fabrics, polyester, and cotton fabrics, as well as polyimide films (PI films) or thermoplastics such as ABS and PVC. Canvas, polyester, and cotton fabrics are commonly used materials in everyday items such as clothing and seat belts. Directly fabricating sensors on these substrates allows for seamless integration. These fabric substrates are particularly suitable for digital embroidery techniques or combined with thermoplastic processes. Polyimide films (PI films) or thermoplastics are themselves excellent flexible circuit board substrates, possessing superior electrical insulation and mechanical properties. They are often used to carry precision circuits manufactured through printing or etching processes and can be attached to the final product through thermoplastic processes.

[0114] It should be noted that the material properties of the flexible substrate will affect the performance of the sensor. For example, different fabrics have different dielectric constants (e.g., polyester has a dielectric constant of ε). 涤纶 =1.9, the dielectric constant of the canvas is ε 帆布 =2.12), which affects the propagation constant β of the surface wave. Furthermore, if the substrate material has a certain degree of conductivity, it will introduce transmission losses. These effects can be compensated for and optimized by adjusting the geometric parameters of the periodic propagation unit (such as the fill factor q).

[0115] Based on any of the above embodiments Figure 5 This is a flowchart illustrating the method of using the metamaterial physiological sensor provided by the present invention, as shown below. Figure 5 As shown, the method specifically includes the following steps:

[0116] Step S1: Input a conventional electromagnetic wave signal into the surface wave sensing structure, and convert the conventional electromagnetic wave signal into a surface electromagnetic wave through the surface wave sensing structure.

[0117] Step S2: The surface electromagnetic wave is guided to propagate along a preset path that is attached to the human body using the surface wave sensing structure, so as to interact with the human tissue.

[0118] Step S3: Output target electromagnetic wave signal. The target electromagnetic wave signal is an electromagnetic wave signal that carries target change information caused by human physiological activities after the inter-field interaction. The target change information includes at least one of phase change, amplitude change, capability change, and frequency shift change.

[0119] Step S4: Extract target change information from the target electromagnetic wave signal to obtain information about the human physiological activity.

[0120] Specifically, embodiments of the present invention provide a method for detecting physiological signals using the metamaterial physiological sensor described in any of the foregoing embodiments. Figure 6 This is a schematic diagram of the sensor wearing and physiological sensing signals provided by the present invention, as shown below. Figure 6 As shown, Figure 6 (a) shows a schematic of sensor wearing and sensing principle, and uses a specific pattern as an example to show the position of input signal and output signal. Figure 6 (b) in the example of digital embroidery illustrates the integrated manufacturing process of sensors and the schematic diagram of each part of the sensor structure. Figure 6 (c) shows examples of sensor usage in clothing of different thicknesses (short sleeves, thick coats) and in different wearing positions. Figure 6 (d) in the diagram illustrates the principle of sensor data processing.

[0121] In use, a radio frequency signal source is first required, such as a radio frequency generator module. This signal source generates a conventional electromagnetic wave signal at a preset frequency (f... RF For example, a continuous sine wave with a frequency of 2.4 GHz. This signal is connected to the signal input terminal of the sensor's feed conversion structure via a transmission medium such as a coaxial cable. After receiving this signal, the feed conversion structure transmits it to the surface wave sensing structure.

[0122] Upon receiving a conventional electromagnetic wave signal, the surface wave sensing structure efficiently converts it into an electromagnetic wave with a larger wave vector, whose energy is confined to the sensor surface (i.e., deceiving surface plasmon polaritons), and guides it to propagate along a flexible substrate conforming to the human body. Because the sensor conformally fits to the user's body via the flexible substrate (e.g., by fastening a seatbelt with integrated sensors, fitting snugly against the chest or abdomen),... Figure 6As shown in (c) of the diagram, when the surface electromagnetic wave propagates along the preset path of the surface wave sensing structure, its electromagnetic field couples with the adjacent human surface tissue, forming an inter-field interaction. Human physiological activities, such as the periodic undulation of the chest and abdominal cavities caused by breathing, and the vibration of human tissues caused by heartbeat, will cause slight changes in the distance between the sensor and the human tissue, as well as local changes in the dielectric constant of the human tissue.

[0123] The minute physical changes caused by the aforementioned physiological activities modulate the effective path length and propagation medium properties of the propagating surface electromagnetic wave, thereby superimposing a small, time-varying Doppler phase shift (f) onto its phase. D The modulated surface electromagnetic wave continues to propagate to the end of the surface wave sensing structure, re-enters the feeding conversion structure, and is output from its signal output terminal, becoming the target electromagnetic wave signal. At this point, the phase (or amplitude, energy, frequency shift, etc.) of the target electromagnetic wave signal carries key information about physiological activities such as breathing and heartbeat.

[0124] The output target electromagnetic wave signal is sent to the signal processing unit. This unit compares the received target signal with the original input reference signal to extract the pure target change signal (i.e., Figure 6 The phase signal shown in (d) is the original signal. This raw signal is typically a mixture of respiratory and heartbeat signals. Subsequently, through digital signal processing techniques (such as filtering, Fourier transform, or wavelet analysis), the lower-frequency respiratory signal component and the higher-frequency, smaller-amplitude heartbeat signal component (i.e., the phase signal shown in (d)) can be separated from the mixed signal. Figure 6 (The virtual signal shown in (d)). Finally, by processing these separated signals using algorithms such as peak detection and spectrum analysis, the user's breathing and heart rate related parameters can be accurately calculated, such as real-time respiratory rate (RR), heart rate (HR), and even more refined parameters such as respiratory interval (RBI) and heart rate interval (IBI), thereby achieving continuous monitoring and analysis of the user's physiological state.

[0125] The method provided in this invention realizes the entire process of non-contact physiological signal detection using metamaterial physiological sensors. The method is simple to operate, directly using personal items as sensor carriers to achieve non-contact monitoring. Based on the near-field sensing principle, it effectively resists macroscopic motion interference such as changes in driving posture, and can stably and accurately acquire high signal-to-noise ratio breathing and heartbeat signals in dynamic and complex environments such as car driving.

[0126] Based on any of the above embodiments Figure 7 This is a schematic diagram illustrating the design optimization of the conductor portion of the metamaterial physiological sensor provided by the present invention, as shown below. Figure 7As shown, the relevant data were obtained through electromagnetic simulations using platforms such as CST Studio Suite 2020.07 (Dassault Systems). The goal is to design a metamaterial physiological sensor conductor that can operate effectively in the 2.4-2.5 GHz frequency band. Figure 7 The dispersion curve of the SSP (spoof surface plasmon) structure was obtained using an eigenmode solver defined by periodic boundary conditions (i.e., the smallest repeating element of the sensor). This curve reveals the propagation characteristics of electromagnetic waves in this material. The field distribution was calculated using finite integration techniques with waveguide port excitation. To evaluate the transmission efficiency and extract the phase change, a metamaterial structure was placed on top of a computational voxel body model, which was represented as a uniform muscular cylinder (dielectric constant ε). r =53.8+i13.9), and concentric (dielectric constant ε) h =59.9+i8.8) and lung (dielectric constant ε) i =36.7+i4.7) voxel models. Cyclic simulations of respiration and heartbeat were performed by introducing periodic geometric changes into the heart and lung voxel models, respectively. Changes in the tissue dielectric constant caused by simulated physiological motion are reflected in the phase changes.

[0127] Figure 7 (a) shows a schematic diagram of a metamaterial waveguide and its geometric design parameters (top), as well as the electric field distribution of the surface mode in the xy plane (bottom), with a scale bar of 1 cm. Figure 7 In (b), dispersion relation analysis was conducted on the unit cell of the designed geometric parameters to obtain the characteristics of the surface mode within the desired 2.4–2.5 GHz operating band.

[0128] Figure 7 Figure (b) shows the dispersion curves for different q values, with other parameters being h=15mm, p=10mm, a=6mm, and the thickness of the substrate polyester fabric being t=1mm. The gray shaded area indicates the 2.4-2.5GHz ISM band. Figure 7 Figure (c) shows the relationship between the substrate wavenumber β and the fill factor q for different fabrics. sub This represents the substrate dielectric constant. As the fill factor q decreases from 8 mm to 1 mm, the wavenumber β at 2.4 GHz increases from 0.48π to 0.65π rad. cm -1 This indicates stronger field confinement and wavelength compression. To achieve efficient wave vector conversion from metamaterial structures to 50Ω coplanar waveguides, a transition section compatible with conventional microwave connectors was designed. Figure 7(c) shows that the fill factor can be adjusted to support 0.49π to 0.59π rad on different textile substrates. cm -1 Surface patterns within the range.

[0129] Figure 7 (d) in Figure 7 Figure (e) illustrates a schematic diagram of the impedance matching transition section consisting of a gradient corrugated hollow strip and a horn-shaped ground plane, and its effect on improving the overall sensor performance. The transmission efficiency is increased by more than 4 dB, and the conversion loss between the metamaterial waveguide and the coplanar waveguide is reduced. On the other hand, the transmission loss of the metamaterial biosensor depends on the conductivity of the fabric, which can be adjusted by changing the fill factor. Figure 7 (as shown in (f)). To ensure compatibility with embroidery production and maintain subwavelength compression, q=2mm can be selected to keep the transmission loss on the polyester fabric substrate below 0.25dB / cm.

[0130] Figure 7 (g) in the diagram illustrates the sensing mechanism and system design: f RF A radar signal at 2.4 GHz was guided along a path by a metamaterial biosensor, and its interaction with the human body resulted in a phase change f captured in the returned signal. D . Figure 7 (h) in Figure 7 (i) shows the breathing and heartbeat signal waveforms over one cycle. Simulated breathing and heartbeat signal waveforms can be obtained by analyzing the phase changes of the transmitted wireless signals. The simulated effects of breathing and heartbeat motion on the propagating surface waves are represented by the demodulation phase changes in the calculated voxel model. Furthermore, compared to microstrip line and notched transmission line sensing structures, the sensor provided by this invention has a higher signal-to-noise ratio, partly due to the ability of the seatbelt integration structure to conform to the contours of the seatbelt and body.

[0131] Figure 8 This is a schematic diagram illustrating the design optimization of the dispersive properties of the metamaterial physiological sensor provided by the present invention, as shown below. Figure 8 As shown, each curve in the figure is called a dispersion curve, which describes the relationship between the frequency of the electromagnetic wave (vertical axis) and the propagation constant (horizontal axis, representing the degree of wave compression). The further the curve shifts to the lower right, the more the electromagnetic wave is compressed (shorter wavelength) at the same frequency, and the more concentrated the energy is on the sensor surface. Figure 8 Figure (a) shows the effect of parameter h on the dispersion characteristics. Figure 8 Figure (b) illustrates the effect of parameter p on the dispersive properties. It should be understood that, as... Figure 8As shown in (a), parameter h represents the length of the meandering metal line in the periodic conductive unit structure, parameter a represents the width of the middle metal strip in the unit structure, and parameter p represents the periodic width of the unit structure.

[0132] Figure 9 This is a schematic diagram illustrating the impact of folding and bending on the transmission efficiency of the metamaterial physiological sensor provided by this invention, as shown in the figure. Figure 9 As shown, the influence of the textile substrate on the sensitivity of the metamaterial biosensor was further investigated. The horizontal axis R represents the bending radius of the sensor. Although the coupling efficiency decreases with increasing substrate thickness t, the biosensor maintains a sufficient phase change of more than 0.01 rad, enabling reliable extraction of respiratory and heartbeat motions from different substrate materials. The robustness of the biosensor to bending and folding was also demonstrated; simulations showed that the transmission loss was less than 2 dB for a U-shaped bend with a curvature radius of 1 mm.

[0133] The safety characteristics were studied by simulating the human torso. The results showed that, at an input power of 10 dBm, the volume-average specific absorption rate and peak specific absorption rate measured on 10 g of tissue were 0.1 mW / kg and 0.05 W / kg, respectively, which are basically below the corresponding thresholds of 0.08 W / kg and 2 W / kg.

[0134] Figure 10 This is a schematic diagram illustrating the relevant test results of the metamaterial physiological sensor provided by this invention during vehicle-mounted testing, as shown below. Figure 10 As shown, Figure 10 (a) Figure 10 (b) shows the comparison between the extracted respiratory rate and heart rate and the reference measurement values. The measurement results of the sensing system of the present invention can closely approximate the true values. Figure 10 (c) in the diagram shows the recorded vehicle speed data; Figure 10 (d) in the figure shows the recorded triaxial accelerometer data; Figure 10 (e) in the figure shows the breathing interval (RBI) estimation error throughout the experiment, to demonstrate the high accuracy of the measurement results of the sensing system of the present invention.

[0135] The above description is merely a selection of preferred embodiments of the present invention and an explanation of the technical principles employed. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that the scope of the invention involved in the embodiments of the present invention is not limited to technical solutions formed by specific combinations of the above-described technical features, but should also cover other technical solutions formed by arbitrary combinations of the above-described technical features or their equivalents without departing from the above-described inventive concept. For example, technical solutions formed by substituting the above-described features with (but not limited to) technical features with similar functions disclosed in the embodiments of the present invention.

Claims

1. A metamaterial physiological sensor, characterized in that, include: A surface wave sensing structure is used to confine conventional electromagnetic waves into surface electromagnetic waves and guide the surface electromagnetic waves to propagate along a preset path to interact with human tissues, and to sense physiological activities based on the interaction between the two fields. The power conversion structure has one end as an input terminal for connecting to an externally input conventional electromagnetic wave, and the other end connected to the surface wave sensing structure for transmitting the conventional electromagnetic wave to the surface wave sensing structure and outputting the electromagnetic wave after the inter-field interaction. The surface wave sensing structure includes: A periodic conduction unit is used to control the wavelength of the conventional electromagnetic wave to constrain the conventional electromagnetic wave into a surface electromagnetic wave. The individual periodic shape of the periodic conduction unit is set to any shape that can generate or transmit surface electromagnetic waves. The power conversion structure is a coplanar waveguide structure, including a signal input terminal, a signal output terminal, a ground plane, and a connection portion for connecting the surface wave sensing structure. The signal input terminal and the signal output terminal are located at the edge of the coplanar waveguide structure. A defect structure is provided on the ground plane to change the electromagnetic field distribution in the region of the power conversion structure, thereby extending the transmission path of the surface electromagnetic wave and allowing the surface electromagnetic wave to have more sufficient interaction time and space with human tissue.

2. The metamaterial physiological sensor according to claim 1, characterized in that, Also includes: The reflective surface structure is electrically connected to the power conversion structure, and is used to provide a ground plane for the power conversion structure and reflect the surface electromagnetic waves.

3. The metamaterial physiological sensor according to claim 2, characterized in that, Also includes: A flexible substrate is used to support the surface wave sensing structure, the power conversion structure, and the reflective surface structure, so that the metamaterial physiological sensor conformally fits the human body.

4. The metamaterial physiological sensor according to claim 3, characterized in that, The metamaterial physiological sensor has a single-sided structure, wherein the reflective surface structure and the ground plane of the power conversion structure are integrated into one unit.

5. The metamaterial physiological sensor according to claim 3, characterized in that, The metamaterial physiological sensor has a double-sided structure, wherein the reflective surface structure is disposed on the side of the flexible substrate opposite to the surface wave sensing structure.

6. The metamaterial physiological sensor according to any one of claims 1 to 5, characterized in that, The surface wave sensing structure further includes a gradient transition unit disposed between the periodic conduction unit and the power supply conversion structure.

7. The metamaterial physiological sensor according to any one of claims 3 to 5, characterized in that, The surface wave sensing structure, the power supply conversion structure, and the reflective surface structure are made of conductive material, which is integrated onto the flexible substrate through a predetermined process.

8. A method of using a metamaterial physiological sensor as described in any one of claims 1 to 7, characterized in that, Includes the following steps: A conventional electromagnetic wave signal is transmitted to a surface wave sensing structure, and the conventional electromagnetic wave signal is converted into a surface electromagnetic wave through the surface wave sensing structure. The surface wave sensing structure is used to guide the surface electromagnetic waves to propagate along a preset path that is attached to the human body, so as to generate inter-field interaction with human tissue. Output target electromagnetic wave signal, wherein the target electromagnetic wave signal is an electromagnetic wave signal that carries target change information caused by human physiological activities after passing through the inter-field interaction, and the target change information includes at least one of phase change, amplitude change, energy change, and frequency shift change; Target change information is extracted from the target electromagnetic wave signal to obtain information about human physiological activities.

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