A piezoresistive sensor and methods of forming and operating the same

Abstract

A piezoresistive sensor and a forming method and an operating method thereof, the piezoresistive sensor comprising: a substrate; a micro tube located on a surface of the substrate, two ends of the micro tube being sealed and containing a conductive liquid inside, wherein the micro tube is in a double helix shape and extends from both ends, or the micro tube is in a wavy line shape and extends from both ends; and a pair of wires, each pair of wires being drawn from both ends of the micro tube and being electrically connected with the conductive liquid. The piezoresistive sensor can precisely fit the detection site during detection, which helps to improve the sensitivity of detection and the accuracy of detection results.

Description

Technical Field

[0001] This invention relates to the field of sensor technology, and in particular to a piezoresistive sensor and its manufacturing and operating methods. Background Technology

[0002] In recent years, with the continuous development and research of flexible sensors, the acquisition and monitoring of human physiological signals has gradually become an important research topic.

[0003] Most existing flexible piezoresistive sensors are typically made from a single elastic polymer microtube, and during detection, the linear sensor is directly attached to the detection site or encapsulated within a continuous, planar flexible polymer substrate (e.g., in a sandwich structure). Because pressure in a linear or planar continuous substrate causes deformation outside the contact surface, substrate deformation coupling occurs between multiple adjacent pressure sources. Sensors encapsulated in a planar continuous substrate have low measurement resolution for pressure sources that are close together. Furthermore, sensors encapsulated within a planar substrate have poor conformability to the complex shapes of the human body, making it difficult to apply precise pressure, resulting in significant measurement drift and insufficient accuracy and stability.

[0004] Therefore, there is an urgent need for a piezoresistive sensor that can be made into a spiral or wavy shape by simulating a human finger and placed directly on the surface of the substrate. This can improve the sensitivity and resolution of the sensor, and because it can fit closely and precisely to the detection area during detection, it can help improve the sensitivity, stability and accuracy of the detection results. Summary of the Invention

[0005] The technical problem solved by this invention is that existing piezoresistive sensors, due to design flaws, are difficult to fit tightly and accurately to the detection area, resulting in low detection sensitivity, insufficient accuracy of detection results, and inadequate detection stability.

[0006] To address the aforementioned technical problems, this invention provides a piezoresistive sensor, comprising: a substrate; a microtube located on the surface of the substrate, the microtube being sealed at both ends and containing a conductive liquid, wherein the microtube is in a double helix shape with both ends extending out, or the microtube is in a wavy shape with both ends extending out; and pairs of wires, each pair of wires being led out from both ends of the microtube and electrically connected to the conductive liquid.

[0007] Optionally, the surface of the substrate has one or more protrusions; wherein one or more of the microtubes are respectively placed on the protrusions of the surface of the substrate in a one-to-one correspondence.

[0008] Optionally, the shape of one or more protrusions on the substrate surface is selected from one or more of the following: arc-shaped, cylindrical, or spherical.

[0009] Optionally, the substrate may be composed of silicone materials.

[0010] Optionally, the microtube is in a double helix shape, and from the center point of the helix, the two parts of the microtube respectively form a nested outer helix and an inner helix; wherein, the center point of the helix is ​​the dividing point between the two parts of the microtube.

[0011] Optionally, the thread pitch of the outer spiral ring and the thread pitch of the inner spiral ring are both less than or equal to a first threshold; and / or, the distance between the position with the largest thread curvature closest to the spiral center point in the outer spiral ring and the position with the largest thread curvature closest to the spiral center point in the inner spiral ring is less than or equal to a second threshold.

[0012] Optionally, the microtube is wavy, and the distance between two adjacent peaks in the wavy line is less than or equal to a third threshold; and / or, the microtube is wavy, and the difference between adjacent peaks and troughs in the wavy line is greater than or equal to a fourth threshold.

[0013] Optionally, the conductive liquid is selected from: liquid metal, conductive gel, ionic liquid and salt solution.

[0014] Optionally, the piezoresistive sensor has a pressure loading device for applying variable pressure from the back side of the substrate to the microtube.

[0015] Optionally, the pressure loading device includes an air bladder and provides pressure by inflating the air bladder; wherein different air pressures in the air bladder result in different pressures supplied to the microtube.

[0016] This invention also provides a method for forming the piezoresistive sensor, comprising: adding the conductive liquid into the microtube and sealing and connecting the wires to both ends of the microtube; determining the dividing point of the two parts of the microtube as the helical center point, rotating the two parts of the microtube around the helical center point to obtain a planar double helix structure, or bending the microtube into a wavy structure; and placing one or more of the microtubes on the surface of the substrate.

[0017] Optionally, before placing one or more of the microtubes on the surface of the substrate, the method further includes: forming a substrate having one or more protrusions on its surface; and subjecting the substrate to a heat curing process; wherein the one or more microtubes are respectively placed on the protrusions on the surface of the substrate in a one-to-one correspondence.

[0018] This invention also provides a method for operating the piezoresistive sensor, comprising: attaching one or more microtubes of the piezoresistive sensor to the detection site of the subject; and measuring the electrical signal transmitted by the wires of the piezoresistive sensor to determine the pulse wave signal of the detection site.

[0019] Optionally, attaching one or more microtubes of the piezoresistive sensor to the detection sites of the subject includes attaching one or more microtubes of the piezoresistive sensor to the three detection sites of the cun, guan, and chi pulses on the wrist of the subject.

[0020] Optionally, the piezoresistive sensor has a pressure loading device for providing variable pressure from the back of the substrate to the microtube; during the measurement of the electrical signal transmitted by the piezoresistive sensor, the pressure provided by the pressure loading device is changed to determine the pulse wave signal corresponding to different pressures.

[0021] Optionally, attaching the microtubes of one or more piezoresistive sensors to the detection sites of the subject includes attaching the microtubes of at least two of the piezoresistive sensors to the first detection site of the brachial artery and the second detection site of the radial artery of the subject.

[0022] This invention also provides a method for processing pulse wave signals obtained based on the operation method of the piezoresistive sensor, comprising: determining the average resistance value of the piezoresistive sensor within a preset time period based on the pulse wave signal; wherein the average resistance value is used to determine the temperature value of the detection site.

[0023] This invention also provides a method for processing pulse wave signals obtained based on the operation method of the piezoresistive sensor, comprising: using a denoising algorithm to denoise the pulse wave signal to obtain a denoised pulse wave signal; and using a heart rate extraction algorithm to determine the heart rate of the subject based on the denoised pulse wave signal.

[0024] Optionally, a denoising algorithm is used to denoise the pulse wave signal to obtain a denoised pulse wave signal, including: using the Mallat algorithm to perform wavelet decomposition of the pulse wave signal at a preset level to obtain multiple pulse wave components; setting the pulse wave components with frequency values ​​higher than a first frequency threshold and the pulse wave components with frequency values ​​lower than a second frequency threshold to zero in the time domain to obtain the denoised pulse wave signal.

[0025] Optionally, a heart rate extraction algorithm is used to determine the heart rate of the subject based on the denoised pulse wave signal, including: performing a fast Fourier transform on the denoised pulse wave signal to obtain the spectrum of the denoised pulse wave signal; and taking the frequency peaks in the spectrum of the denoised pulse wave signal as the heart rate of the subject.

[0026] Optionally, after obtaining the denoised pulse wave signal, the method further includes: using a Butterworth filter to filter the denoised pulse wave signal to obtain a filtered pulse wave signal; performing a fast Fourier transform on the filtered pulse wave signal to obtain the spectrum of the filtered pulse wave signal; and using the frequency peaks in the spectrum of the filtered pulse wave signal as the resting respiratory rate of the subject.

[0027] This invention also provides a method for processing pulse wave signals obtained based on the operation method of the piezoresistive sensor, comprising: using a neural network algorithm to input the pulse wave signal into a neural network model, and using the output of the neural network model as the blood pressure value of the subject to be tested.

[0028] This invention also provides a method for processing pulse wave signals obtained based on the operation method of the piezoresistive sensor, wherein the detection site is the blood vessels of the subject, including a third detection position and a fourth detection position; the method includes: taking the difference between the first time corresponding to the peak of the pulse wave signal at the third detection position and the second time corresponding to the peak of the pulse wave signal at the fourth detection position as the pulse wave signal propagation duration at the third and fourth detection positions; determining the pulse wave signal propagation velocity based on the distance between the third and fourth detection positions and the pulse wave signal propagation duration; wherein the pulse wave signal propagation velocity is used to determine the vascular elasticity value of the subject.

[0029] This invention also provides an operating method for the piezoresistive sensor, comprising: attaching one or more of the piezoresistive sensors to the detection portion of the test piece; and measuring the electrical signal transmitted through the wires of the piezoresistive sensor to determine the pressure on the detection portion.

[0030] Optionally, the test component is selected from one or more of the following: aircraft wings, propellers, engine fans, ship hulls, submersibles, and marine structures.

[0031] Optionally, the detection area of ​​the test piece is the surface of an aircraft wing; measuring the electrical signal transmitted through the wires of the piezoresistive sensor to determine the pressure on the detection area includes: measuring the electrical signal transmitted through the wires of the piezoresistive sensor to determine the airflow pressure on the surface of the aircraft wing.

[0032] Optionally, the detection area of ​​the test piece is the surface of the propeller blades; measuring the electrical signal transmitted through the wires of the piezoresistive sensor to determine the pressure on the detection area includes: measuring the electrical signal transmitted through the wires of the piezoresistive sensor to determine the fluid pressure on the surface of the propeller blades.

[0033] Optionally, the test piece is a ship hull; attaching one or more of the piezoresistive sensors to the detection area of ​​the test piece includes: attaching the back of the substrate of one or more of the piezoresistive sensors to the surface of the waterline portion of the side of the ship hull.

[0034] Optionally, the detection area of ​​the test piece is the surface of the hull below the waterline; measuring the electrical signal transmitted by the wire of the piezoresistive sensor to determine the pressure on the detection area includes: measuring the electrical signal transmitted by the wire of the piezoresistive sensor to determine the water flow pressure on the surface of the hull below the waterline.

[0035] Optionally, the piezoresistive sensor has a temperature measuring device for measuring the temperature value of the piezoresistive sensor; measuring the electrical signal transmitted through the wires of the piezoresistive sensor to determine the pressure on the detection part includes: measuring the electrical signal transmitted through the wires of the piezoresistive sensor and the temperature value of the piezoresistive sensor to determine the pressure on the detection part.

[0036] This invention also provides a processing device for pulse wave signals obtained based on the operation method of the piezoresistive sensor, comprising: a resistance value determination module, used to determine the average resistance value of the piezoresistive sensor within a preset time period based on the pulse wave signal; wherein the average resistance value is used to determine the temperature value of the detection site.

[0037] This invention also provides a processing device for pulse wave signals obtained based on the operation method of the piezoresistive sensor, comprising: a signal denoising module for denoising the pulse wave signal to obtain a denoised pulse wave signal; and a heart rate detection module for determining the heart rate of the subject based on the denoised pulse wave signal using a heart rate extraction algorithm.

[0038] This invention also provides a processing device for pulse wave signals obtained based on the operation method of the piezoresistive sensor, comprising: a blood pressure value determination module, used to input the pulse wave signal into a neural network model using a neural network algorithm, and to use the output of the neural network model as the blood pressure value of the subject to be tested.

[0039] This invention also provides a processing device for pulse wave signals obtained based on the operation method of the piezoresistive sensor, wherein the detection site is a blood vessel of the subject, including a third detection position and a fourth detection position, comprising: a signal transmission duration determination module, used to take the difference between the first moment corresponding to the peak of the pulse wave signal at the third detection position and the second moment corresponding to the peak of the pulse wave signal at the fourth detection position as the pulse wave signal transmission duration at the third detection position and the fourth detection position; and a signal transmission velocity determination module, used to determine the pulse wave signal transmission velocity based on the distance between the third detection position and the fourth detection position and the pulse wave signal transmission duration; wherein the pulse wave signal transmission velocity is used to determine the vascular elasticity value of the subject.

[0040] This invention also provides a computer-readable storage medium storing a computer program thereon, wherein the computer program, when run by a processor, executes the steps of the above-described processing method for the pulse wave signal obtained based on the operation method of the piezoresistive sensor.

[0041] This invention also provides a terminal, including a memory and a processor. The memory stores a computer program that can run on the processor. When the processor runs the computer program, it executes the steps of the above-described processing method for pulse wave signals obtained based on the operation method of the piezoresistive sensor.

[0042] Compared with the prior art, the technical solution of the embodiments of the present invention has the following beneficial effects:

[0043] This invention provides a piezoresistive sensor, comprising a substrate; a microtube located on the surface of the substrate, the microtube being sealed at both ends and containing a conductive liquid, wherein the microtube is either double-helical with both ends extending out, or wavy with both ends extending out; and pairs of wires, each pair of wires extending from both ends of the microtube and electrically connected to the conductive liquid. Compared to existing flexible piezoresistive sensors, which are often linearly attached to the detection site or encapsulated within a continuous flexible polymer substrate (e.g., using a sandwich structure), resulting in low detection sensitivity, and furthermore, linear sensors or sensors encapsulated within large-size continuous planar substrates have poor adhesion to the complex shapes of the human body, making it difficult to apply precise pressure and leading to insufficient detection sensitivity, accuracy, and stability, this invention simulates a human finger by using a substrate and a flexible microtube (one-dimensional linear) containing conductive liquid to create a two-dimensional double-helical or wavy sensor. Furthermore, the double-helical or wavy piezoresistive sensor is directly located on the surface of the substrate rather than encapsulated within it, thus allowing for close contact during detection. By applying precise pressure to the affected area, the sensitivity, stability, and accuracy of the piezoresistive sensor are improved. Furthermore, compared to many existing large-size and rigid piezoresistive sensors that can only perform single-point detection at a time and cannot be used to detect pulse wave signal arrays in small areas or at multiple detection sites, the piezoresistive sensor provided in this invention is lightweight and compact, allowing for simultaneous multi-point detection within a small area (detecting multiple detection locations of the same area) or detection of multiple sites using one or more sensors. Moreover, because the electrical signals of each piezoresistive sensor can be arranged at multiple points and acquired through multiple channels during the detection process, coupling between electrical signals at different detection locations is avoided, improving the resolution between electrical signals and thus enhancing detection accuracy.

[0044] Furthermore, the surface of the substrate has one or more protrusions; wherein, one or more microtubes are respectively placed on the protrusions of the substrate surface in a one-to-one correspondence, and the shape of each protrusion can be selected from arc shape, cylindrical shape, spherical shape, etc. In the embodiments of the present invention, by placing the fabricated spiral or wavy microtubes on the protrusions of the substrate surface, for example by laying and pasting them to fix them on the protrusions of the substrate surface, a special three-dimensional shape is formed. During detection, the protrusions can be pressed against the detection point of a certain detection area to apply precise pressure, thereby improving the stability and accuracy of the detection. In addition, the thickness value of the protrusions or the pressing force of the protrusions can be adjusted according to the needs of different application scenarios to obtain the corresponding detection results under different pressures.

[0045] Furthermore, the microtube is double-helical, and the thread pitch of both the outer and inner spiral rings is less than or equal to a first threshold; and / or, the distance between the position with the largest thread curvature closest to the helical center point in the outer spiral ring and the position with the largest thread curvature closest to the helical center point in the inner spiral ring is less than or equal to a second threshold. In this embodiment of the invention, since the smaller the spacing between the threads in the outer or inner spiral rings (the higher the thread density), and / or the smaller the distance between the position with the largest thread curvature closest to the helical center point in the outer spiral ring and the position with the largest thread curvature closest to the helical center point in the inner spiral ring, the greater the signal strength of the piezoresistive sensor per unit area, and the higher the detection sensitivity and accuracy. Therefore, in different application scenarios, the detection sensitivity and accuracy can be improved as much as possible by adjusting the first threshold and / or the second threshold to an appropriate degree (wherein, the minimum values ​​of the first threshold and the second threshold are determined by the bending characteristics of the microtube itself).

[0046] Furthermore, the microtube is wavy, and the distance between two adjacent peaks in the wavy line is less than or equal to a third threshold; and / or, the microtube is wavy, and the distance between adjacent peaks and troughs in the wavy line is greater than or equal to a fourth threshold. In this embodiment of the invention, since the smaller the distance between two adjacent peaks in the wavy line (the higher the stripe density), and / or the larger the distance between adjacent peaks and troughs in the wavy line, the greater the signal strength of the piezoresistive sensor per unit area, and the higher the detection sensitivity and accuracy. Therefore, in different application scenarios, the detection sensitivity and accuracy can be improved as much as possible by adjusting the third threshold and / or the fourth threshold to an appropriate level (wherein, the minimum values ​​of the third threshold and the fourth threshold are determined by the bending characteristics of the microtube itself).

[0047] Furthermore, the piezoresistive sensor includes a pressure loading device for providing variable pressure from the back side of the substrate to the microtube. This pressure loading device comprises an air bladder, and pressure is provided by inflating the air bladder; different air pressures result in different pressures applied to the microtube. By employing this technical solution, for the same detection site, different detection results can be obtained under different pressures by changing the applied pressure. Attached Figure Description

[0048] Figure 1 This is a schematic diagram of the structure of a double-helix piezoresistive sensor according to an embodiment of the present invention;

[0049] Figure 2 yes Figure 1 Top view;

[0050] Figure 3 yes Figure 1 Side view;

[0051] Figure 4 This is a schematic diagram of the structure of a planar double-helix microtube in an embodiment of the present invention;

[0052] Figure 5 This is a schematic diagram of the structure of a wavy linear piezoresistive sensor according to an embodiment of the present invention;

[0053] Figure 6 yes Figure 5 Top view;

[0054] Figure 7 yes Figure 5 Side view;

[0055] Figure 8 This is a schematic diagram of the structure of a wavy linear microtube in an embodiment of the present invention;

[0056] Figure 9 This is a flowchart of a method for forming a piezoresistive sensor according to an embodiment of the present invention;

[0057] Figure 10 This is a flowchart of the first operation method of the piezoresistive sensor in this embodiment of the invention;

[0058] Figure 11 This is a schematic diagram of the structure of a wristband containing a double-helix piezoresistive sensor according to an embodiment of the present invention;

[0059] Figure 12 This is a schematic diagram of a pulse wave detection system based on a piezoresistive sensor in an embodiment of the present invention;

[0060] Figure 13 This is a flowchart of the second operation method of the piezoresistive sensor in this embodiment of the invention;

[0061] Figure 14 This is a flowchart of the third operation method of the piezoresistive sensor in the embodiments of the present invention;

[0062] Figure 15 This is a flowchart of the fourth operation method of the piezoresistive sensor in this embodiment of the invention;

[0063] Figure 16 This is a schematic diagram of the structure of a double-helix piezoresistive sensor with a temperature measuring device in an embodiment of the present invention;

[0064] Figure 17 Based on Figure 10 A flowchart of a method for processing pulse wave signals obtained in the process;

[0065] Figure 18Based on Figure 10 A schematic diagram of a processing device for pulse wave signals obtained in the process.

[0066] Explanation of reference numerals in the attached figures:

[0067] Double-helix piezoresistive sensor-10; substrate-11; microtube-12; helix center point-123; wire-13; wavy linear piezoresistive sensor-20; wristband-30; flexible band-31; data acquisition and processing system-32; airbag-33; pulse wave detection system based on piezoresistive sensor-40; sensing module-41; electrical signal acquisition and processing module-42; electrical signal transmission module-43; electrical signal receiving module-44; temperature measurement device-50. Detailed Implementation

[0068] As mentioned earlier, with the continuous development and research of flexible sensors, the acquisition and monitoring of human physiological signals has gradually become an important research topic.

[0069] In existing technologies, most flexible piezoresistive sensors are typically made from a single elastic polymer microtube, and during detection, the linear sensor is directly attached to the detection site or encapsulated within a continuous, planar flexible polymer substrate. The inventors of this invention have discovered that pressure in a linear or planar continuous substrate causes deformation outside the contact surface, leading to substrate deformation coupling between multiple adjacent pressure sources. Sensors encapsulated in a planar continuous substrate have low measurement resolution for pressure sources that are close together. Furthermore, planar sensors have poor conformability to the complex shapes of the human body, making it difficult to apply precise pressure, resulting in significant measurement drift and insufficient accuracy and stability.

[0070] This invention provides a piezoresistive sensor, including a substrate; a microtube located on the surface of the substrate, the microtube being sealed at both ends and containing a conductive liquid, wherein the microtube is in a double helix shape with both ends extending out, or the microtube is in a wavy shape with both ends extending out; and pairs of wires, each pair of wires extending from both ends of the microtube and electrically connected to the conductive liquid. Compared to existing flexible piezoresistive sensors, which are often linearly attached to the detection site during detection, or encapsulated within a continuous flexible polymer substrate (e.g., using a sandwich structure), resulting in low detection sensitivity; furthermore, linear sensors or sensors encapsulated within large-size continuous substrates have poor adhesion to the complex shapes of the human body, making it difficult to apply precise pressure, leading to insufficient detection sensitivity, accuracy, and stability; this invention simulates a human finger, using a substrate and a flexible microtube containing conductive liquid to create a two-dimensional double helix or wavy line sensor, and the double helix or wavy line piezoresistive sensor is directly located on the surface of the substrate rather than encapsulated within it, thereby allowing for close contact with the detection site during detection. Applying precise pressure improves the sensitivity, detection stability, and accuracy of the piezoresistive sensor. Furthermore, compared to many existing large-size and rigid piezoresistive sensors that can only perform single-point detection at a time and cannot be used to detect pulse wave signal arrays in small areas or multiple detection sites, the piezoresistive sensor provided in this invention is lightweight and compact, allowing for simultaneous multi-point detection within a small area (detection at multiple detection locations within the same area) or detection at multiple sites using one or more sensors. Moreover, since the electrical signals of each piezoresistive sensor can be arranged at multiple points and acquired through multiple channels during the detection process, coupling between electrical signals at different detection locations is avoided, improving the resolution between electrical signals and thus enhancing detection accuracy.

[0071] To make the above-mentioned objectives, features and beneficial effects of the present invention more apparent and understandable, specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

[0072] Reference Figures 1 to 3 , Figure 1 This is a schematic diagram of the structure of a double-helix piezoresistive sensor according to an embodiment of the present invention. Figure 2 yes Figure 1 Top view, Figure 3 yes Figure 1 The side view. Below, combined with... Figures 1 to 3 The specific structure of the double-helix piezoresistive sensor is described below.

[0073] The double-helix piezoresistive sensor 10 may include a substrate 11, a microtube 12, and a wire 13.

[0074] The surface of the substrate 11 may have one or more protrusions, and one or more microtubes 12 are respectively placed on the protrusions on the surface of the substrate 11.

[0075] In some non-limiting embodiments, the shape of one or more protrusions on the surface of the substrate 11 may be selected from one or more of the following: arc-shaped, cylindrical, spherical; in addition to the above shapes, in specific implementations, the protrusions may also be designed as other regular or irregular three-dimensional shapes according to the needs of different application scenarios.

[0076] Furthermore, the constituent materials of the substrate 11 may include organosilicon materials, such as polydimethylsiloxane (PDMS).

[0077] In specific implementation, the substrate 11 can be made in the following way: (1) First, a sheet-like flexible substrate is made using PDMS. The shape of the flexible substrate can be selected from rectangle, circle, ellipse and other regular or irregular polygons (as a non-limiting embodiment, the sheet-like flexible substrate is rectangular, with a length of 10cm, a width of 5cm and a thickness of 0.2cm). (2) Then, PDMS is dripped onto the above flexible substrate again. The amount of PDMS dripped can be controlled according to the needs of the specific application scenario to obtain one or more protrusions with the same or different thickness / height values; if there are multiple protrusions, the distance between each protrusion can also be controlled according to the needs of the specific application scenario. (3) Then, the entire substrate is heated and cured.

[0078] Understandably, in pulse wave signal detection scenarios, the amount of PDMS dripped can be controlled based on the shape of an adult's index, middle, and ring fingers, and the spacing of each protrusion can be controlled based on the positional spacing of the adult's chi, cun, and guan pulses.

[0079] In this embodiment of the invention, by placing the prepared spiral or wavy microtubes on the protrusions on the surface of the substrate, for example by laying and pasting them onto the protrusions on the surface of the substrate, precise pressure can be applied by pressing the protrusions on a detection point of a certain detection area during detection, thereby improving the stability and accuracy of the detection. In addition, the thickness of the protrusions or the pressing force of the protrusions can be adjusted according to the needs of different application scenarios to obtain different electrical signals.

[0080] The microtube 12 is located on the surface of the substrate 11, and the microtube 12 is double-helixed with both ends extending out. The two ends of the microtube 12 can be sealed with sealant, which can be a two-component epoxy resin sealant. The interior of the microtube 12 contains a conductive liquid.

[0081] In some non-limiting embodiments, the microtube 12 may be a flexible microtube made of an elastic polymer, including but not limited to silicone rubber, PDMS or Ecoflex copolymer; the conductive liquid filling the inside of the microtube 12 may be selected from liquid metal, conductive gel, ionic liquid and salt solution, but is not limited thereto.

[0082] Pairs of wires 13 are led out from both ends of the microtube 12 and electrically connected to the conductive liquid. The materials used to make the wires 13 include copper, gold, silver, etc.

[0083] In this embodiment of the invention, compared to existing flexible piezoresistive sensors that are often linearly attached to the detection site or encapsulated within a continuous flexible polymer substrate (e.g., using a sandwich structure), resulting in low detection sensitivity, linear sensors or sensors encapsulated within a large-size continuous planar substrate have poor adhesion to the complex shapes of the human body, making it difficult to apply precise pressure and leading to insufficient detection sensitivity, accuracy, and stability, this embodiment of the invention simulates a human finger by using a substrate and a flexible microtube containing conductive fluid to fabricate a two-dimensional double-helix piezoresistive sensor. Located directly on the surface of the substrate rather than encapsulated within it, the piezoresistive sensor can closely adhere to the detection area and apply precise pressure during detection, thereby improving detection sensitivity, stability, and accuracy. Furthermore, compared to many existing large-size and rigid piezoresistive sensors that can only perform single-point detection at a time and cannot be used to detect pressure signals in small areas, the piezoresistive sensor provided in this invention is lightweight and compact. It can be used with a single piezoresistive sensor with multiple protrusions to perform multi-point detection within a small area (detecting multiple detection positions in the same area) or multiple piezoresistive sensors to detect multiple areas simultaneously.

[0084] Reference Figure 4 , Figure 4 This is a schematic diagram of a planar double-helix microtube in an embodiment of the present invention.

[0085] Specifically, the two parts of the microtube 12 can be rotated around the helical center point 123 to form nested outer helical coils 124 and inner helical coils 125, respectively, and a planar double helix microtube can be obtained.

[0086] In the planar double-helix microtube, the threads in the outer helical ring 124 and the threads in the inner helical ring 125 are evenly arranged. The thread pitch of the outer helical ring 124 or the thread pitch of the inner helical ring 125 is S. The distance between the position with the largest thread curvature closest to the helical center point 123 in the outer helical ring 124 and the position with the largest thread curvature closest to the helical center point 123 in the inner helical ring 125 is D.

[0087] Specifically, the thread pitch S of the outer spiral ring 124 or the thread pitch S of the inner spiral ring 125 is less than or equal to a first threshold; and / or, the distance D between the position with the largest thread curvature closest to the spiral center point 123 in the outer spiral ring 124 and the position with the largest thread curvature closest to the spiral center point 123 in the inner spiral ring 125 is less than or equal to a second threshold. The minimum values ​​of both the first and second thresholds are determined by the bending characteristics of the microtube itself.

[0088] In specific implementation, if the threads of the outer spiral ring 124 or the threads of the inner spiral ring 125 are not uniformly arranged, the thread pitch of the outer spiral ring 124 or the thread pitch of the inner spiral ring 125 can be the average thread pitch of each spiral ring.

[0089] In this embodiment of the invention, the smaller the spacing between the threads in the outer or inner spiral ring, and / or the smaller the distance between the position with the largest thread curvature closest to the spiral center point in the outer spiral ring and the position with the largest thread curvature closest to the spiral center point in the inner spiral ring, the higher the detection sensitivity and accuracy of the double-spiral piezoresistive sensor. Therefore, in different application scenarios, by adjusting the first threshold and / or the second threshold to an appropriate level, the detection sensitivity and accuracy can be improved as much as possible.

[0090] In practical implementation, the double-helix piezoresistive sensor 10 can be fabricated using the following steps:

[0091] (1) First, prepare a linear piezoresistive sensor: Cut a flexible microtube with an outer diameter of 200 μm and an inner diameter of 100 μm to the required length, insert a 100 μm silver-plated copper wire into one end, and seal it with epoxy resin two-component sealant; use a syringe to inject gallium indium eutectic as a conductive liquid into the flexible microtube; pull out the syringe needle, insert a 100 μm silver-plated copper wire, ensure that the silver-plated copper wire is in contact with the conductive liquid, and seal the other end with epoxy resin two-component sealant.

[0092] (2) Select a point in the middle of the flexible microtube (containing conductive liquid and connected to wires at both ends) as the dividing point / helix center point, and clamp the dividing point / helix center point in the groove at the bottom of a rotating shaft. Then place the clamped flexible microtube on a quartz plate and slowly rotate the rotating shaft to obtain a planar double helix microtube laid flat on the quartz.

[0093] (3) Then, uncured liquid PDMS is injected into the outer surface and thread gap of the planar double helix microtube laid on the quartz to solidify it. After vacuuming (extracting excess air bubbles from the liquid PDMS), the planar double helix microtube is placed in an oven for 2-3 hours. After curing, the planar double helix microtube is taken out.

[0094] (4) Place one or more of the planar double helix microtubes on the protrusions on the surface of the prepared substrate 11 (which can be laid and glued) respectively, thus completing the fabrication of the double helix piezoresistive sensor 10.

[0095] Furthermore, the microtube 12 can also be wavy. Specifically, the microtube 12 can be bent into a wavy shape.

[0096] Reference Figures 5 to 7 , Figure 5 This is a schematic diagram of the structure of a wavy linear piezoresistive sensor according to an embodiment of the present invention. Figure 6 yes Figure 5 Top view, Figure 7 yes Figure 5 The side view. Below, combined with... Figures 5 to 7 The specific structure of the wavy linear piezoresistive sensor is described below.

[0097] The wavy linear piezoresistive sensor 20 may include a substrate 11, a microtube 12, and a wire 13.

[0098] In the wavy piezoresistive sensor 20, the microtubes 12 are uniformly distributed in a wavy shape, and the substrate 11 is semi-cylindrical. Compared to Figure 1 The double-helix piezoresistive sensor 10 differs from the microtube 12 and substrate 11 in shape, but the connection and positional relationships between the substrate 11, microtube 12, and wire 13 are similar. Figure 1 The double-helix piezoresistive sensor 10 is basically the same. In addition, in specific implementations, if the microtube 12 is double-helix, the shape of the protrusion of the substrate 11 is usually made into an arc or spherical shape with a preset bottom area and thickness value; if the microtube 12 is wavy, the shape of the protrusion of the substrate 11 is usually made into a semi-cylindrical shape with a preset bottom area and thickness value.

[0099] Therefore, in specific implementation, the fabrication method of the wavy linear piezoresistive sensor 20 can refer to steps (1), (3), and (4) in the fabrication method of the double-helix piezoresistive sensor 10 described above, and will not be repeated here. The difference from step (2) in the fabrication method of the double-helix piezoresistive sensor 10 is that the linear piezoresistive sensor fabricated in step (1) is not rotated into a planar double-helix structure, but rather the linear piezoresistive sensor is bent into a wavy line structure manually or using specific equipment.

[0100] Reference Figure 8 , Figure 8 This is a schematic diagram of the structure of a wavy linear microtube in an embodiment of the present invention.

[0101] The wavy microtube is U-shaped with parallel wavy lines, and the strips in the wavy lines are evenly arranged. The distance between the first strip and the last strip is L, the distance between two adjacent peaks is m, the distance between two adjacent strips is s, and the distance between adjacent peaks and troughs in the wavy lines is h.

[0102] Wherein, the distance m between two adjacent peaks is less than or equal to a third threshold; and / or, the distance h between adjacent peaks and troughs in the wave line is greater than or equal to a fourth threshold.

[0103] In specific implementation, if the individual strips in the wavy microtube are not uniformly arranged, the distance between two adjacent peaks is the average of the distances between all two adjacent strips, and the difference between adjacent peaks and troughs in the wavy line is the average of the distances between all two adjacent peaks and troughs.

[0104] In this embodiment of the invention, the smaller the spacing between two adjacent peaks in the wavy line (the higher the strip density), and / or the larger the spacing between adjacent peaks and troughs in the wavy line, the greater the signal strength of the piezoresistive sensor per unit area, and the higher the detection sensitivity and accuracy. Therefore, in different application scenarios, the detection sensitivity and accuracy can be improved as much as possible by adjusting the third threshold and / or the fourth threshold to an appropriate degree (wherein, the minimum values ​​of the third threshold and the fourth threshold are determined by the bending characteristics of the microtube itself, and the maximum value of the fourth threshold is usually not greater than the arc length of the substrate protrusion).

[0105] It should be noted that, Figure 8 The wavy microtubes shown are only a non-limiting embodiment. In specific implementations, the arrangement of the wavy lines can be adjusted according to the needs of different application scenarios. This embodiment of the invention does not limit this.

[0106] Reference Figure 9 , Figure 9This is a flowchart of a method for forming a piezoresistive sensor according to an embodiment of the present invention. The method may include steps S91 to S93, which are described below.

[0107] In step S91, the conductive liquid is added into the microtube, and the two ends of the microtube are sealed and connected to the wire.

[0108] In step S92, the dividing point between the two parts of the microtube is determined as the helical center point, and the two parts of the microtube are rotated around the helical center point to obtain a planar double helix structure, or the microtube is bent into a wavy line structure.

[0109] In step S93, one or more of the microtubes are placed on the surface of the substrate.

[0110] Furthermore, before placing one or more of the microtubes on the surface of the substrate, the method further includes: forming a substrate having one or more protrusions on its surface; and subjecting the substrate to a heat curing process; wherein the one or more microtubes are respectively placed on the protrusions on the surface of the substrate in a one-to-one correspondence.

[0111] In a preferred embodiment, the microtubes are planar double helical in shape, the protrusions of the substrate are spherical, and one or more planar double helical microtubes are respectively laid and adhered to the protrusions on the surface of the substrate.

[0112] In another preferred embodiment, the microtubes are wavy, the protrusions of the substrate are semi-cylindrical, and one or more wavy microtubes are laid and adhered to the protrusions on the surface of the substrate in a corresponding manner.

[0113] In specific implementation, please refer to the preceding text for more detailed information regarding steps S91 to S93. Figures 1 to 8 The relevant descriptions of the double-helix piezoresistive sensor and the wavy linear piezoresistive sensor in the document will be executed, and will not be repeated here.

[0114] Reference Figure 10 , Figure 10 This is a flowchart illustrating the first operating method of the piezoresistive sensor in this embodiment of the invention. The piezoresistive sensor can be... Figure 1 The double-helix piezoresistive sensor shown in the image can also be... Figure 5 The wave-shaped piezoresistive sensor shown in the figure, the first operation method may include steps S101 to S102, and each step is described below.

[0115] In step S101, one or more microtubes of the piezoresistive sensor are respectively attached to the detection site of the subject.

[0116] In specific implementation, the method of attaching the piezoresistive sensor to the detection area of ​​the subject can be by adhesive fixation; or by fixing the piezoresistive sensor to the inner surface of the wristband, and the subject wearing the wristband to make the piezoresistive sensor adhere to the detection area; or, depending on the specific application scenario, other suitable methods can be used to attach the piezoresistive sensor to the detection area of ​​the subject to achieve the most secure and accurate fit possible.

[0117] Reference Figure 11 , Figure 11 This is a schematic diagram of the structure of a wristband containing a double-helix piezoresistive sensor according to an embodiment of the present invention.

[0118] The wristband 30 mainly consists of a flexible band 31, three double-helix piezoresistive sensors 10, a data acquisition and processing system 32, and three airbags 33.

[0119] Three double-helix piezoresistive sensors 10 are fixed on the upper surface of three raised air bladders 33 on the inner surface of the wristband 30 (each air bladder 33 is a small hexahedron). Each double-helix piezoresistive sensor 10 consists of a double-helix microtube, a substrate (the raised part of the substrate is spherical), and a pair of wires.

[0120] The thickness of each protrusion on the base is determined based on the pressure caused by the specific pulse of the cun, guan, and chi pulses in the human wrist. The distance between the protrusions on each base is the same as or similar to the distance between the cun, guan, and chi pulses in the human wrist.

[0121] The data acquisition and processing system 32 is fixed directly above the wristband 30 and is used for acquiring and processing electrical signals.

[0122] The flexible band 31 is mainly used to connect the three double-helix piezoresistive sensors 10 and the data acquisition and processing system 32, as well as to wrap and fix them. Specifically, the pairs of wires in each double-helix piezoresistive sensor 10 are hidden inside the wristband 30; the ends of each pair of wires can be connected to the data acquisition and processing system 32 directly above the wristband 30.

[0123] When using the wristband 30 to detect the pulse wave signal of the wrist: (1) The person to be tested first wears the wristband 30 so that the three double-helix piezoresistive sensors 10 located on the inner surface of the wristband 30 are closely fitted to the cun, guan, and chi pulses of the wrist of the person to be tested; (2) The three air bladders 33 are inflated and apply pressure to the three double-helix piezoresistive sensors 10 one by one. When subjected to the pressure caused by the pulse pulsation at each detection point, the microtubes in each double-helix piezoresistive sensor 10 deform, resulting in a change in resistance value. The electrical signal reflecting the change in resistance value can be transmitted to the data acquisition and processing system 32 directly above the wristband 30 through the paired wires in each double-helix piezoresistive sensor 10.

[0124] In practical implementation, the data acquisition and processing system 32 located directly above the wristband 30 can determine the pulse wave signals of the cun, guan, and chi pulses based on the received electrical signals. Furthermore, after determining the pulse wave signals at each detection point, the pulse wave waveform and related information can be directly displayed to the user via a screen mounted on the wristband 30; alternatively, the pulse wave signals can be transmitted to an external signal receiving device via a wired network or a wireless network (WiFi).

[0125] Continue to refer to Figure 10 In step S102, the electrical signal transmitted through the wires of the piezoresistive sensor is measured to determine the pulse wave signal at the detection site.

[0126] In specific implementation, the electrical signal transmitted by the wire can be selected from current signal, voltage signal, and resistance signal. Based on the electrical signal transmitted by the wire, the resistance value of the piezoresistive sensor can be determined. The waveform curve of the pulse wave signal can be plotted by continuously measuring the resistance value of the piezoresistive sensor and plotting the relationship between resistance value and time.

[0127] Furthermore, the piezoresistive sensor has a pressure loading device for providing variable pressure from the back side of the substrate to the microtube; during the measurement of the electrical signal transmitted by the piezoresistive sensor, the pressure provided by the pressure loading device is changed to determine the pulse wave signal corresponding to different pressures.

[0128] Furthermore, the pressure loading device may include an air bladder, and pressure is provided by inflating the air bladder; wherein different air pressures in the air bladder result in different pressures being provided to the microtube.

[0129] In this embodiment of the invention, by adopting the above technical solution, the detection results corresponding to different pressures can be obtained according to the needs of the application scenario. For example, for the same detection part, the pressure applied by the pressure loading device can be changed.

[0130] Reference Figure 12 , Figure 12 This is a schematic diagram of a pulse wave detection system based on a piezoresistive sensor according to an embodiment of the present invention. The piezoresistive sensor can be... Figure 1 The double-helix piezoresistive sensor shown in the image can also be... Figure 5 The image shows a wavy linear piezoresistive sensor.

[0131] The pulse wave detection system 40 based on a piezoresistive sensor includes a sensing module 41, an electrical signal acquisition and processing module 42, an electrical signal transmission module 43, and an electrical signal receiving module 44.

[0132] In a specific implementation, the sensing module 41 mainly includes the piezoresistive sensor, and the ends of the wires of the piezoresistive sensor are sequentially connected to the electrical signal acquisition and processing module 42, the electrical signal transmission module 43, and the electrical signal receiving module 44.

[0133] In the application scenario of pulse wave detection using a pulse wave detection system 40 based on a piezoresistive sensor, the specific operation and data transmission process can be roughly as follows: (1) In the sensing module 41, the piezoresistive sensor is attached to the detection site to be detected; when subjected to pressure caused by the pulse pulsation, the microtube in the piezoresistive sensor deforms, causing the diameter of the microtube to change, which in turn causes the resistance value of the piezoresistive sensor to change. (2) The electrical signal acquisition and processing module 42 acquires and processes the electrical signals transmitted by the wire (the electrical signals mainly include voltage signals, current signals, resistance signals, etc.). (3) The electrical signal sending module 43 can use a wireless network WiFi to send the electrical signals to the electrical signal receiving module 44. (4) The electrical signal receiving module 44 receives the electrical signals and determines the data of the resistance value changing with time, and determines the real-time and accurate pulse wave waveform.

[0134] Reference Figure 13 , Figure 13 This is a flowchart illustrating a second operating method of the piezoresistive sensor in an embodiment of the present invention. The piezoresistive sensor can be... Figure 1 The double-helix piezoresistive sensor shown in the image can also be... Figure 5 The image shows a wavy linear piezoresistive sensor. The second operating method may include steps S131 to S132, which are described below.

[0135] In step S131, one or more microtubes of the piezoresistive sensor are respectively attached to the three detection positions of the wrist of the person to be tested: the cun pulse, guan pulse, and chi pulse.

[0136] In step S132, the electrical signal transmitted through the wires of the piezoresistive sensor is measured to determine the pulse wave signals at the three detection locations of the wrist of the subject to be tested: the cun, guan, and chi pulses.

[0137] Reference Figure 14 , Figure 14 This is a flowchart of the third operation method of the piezoresistive sensor in this embodiment of the invention. The third operation method may include steps S141 to S142, which are described below.

[0138] In step S141, the microtubes of at least two of the piezoresistive sensors are respectively attached to the first detection position of the brachial artery and the second detection position of the radial artery of the subject to be tested.

[0139] In step S142, the electrical signal transmitted through the wires of the piezoresistive sensor is measured to determine the pulse wave signals at the first detection position and the second detection position.

[0140] In this embodiment of the invention, based on Figure 13 or Figure 14 The operation method of the piezoresistive sensor shown herein allows each piezoresistive sensor to have an independent electrical signal transmission port, connected to an electrical signal receiving and processing element, thereby forming a multi-point pulse wave detection system. Compared to many existing large-size and rigid piezoresistive sensors, which can only perform single-point detection at a time and cannot be used to detect pulse wave signal arrays in small areas or multiple detection sites, the piezoresistive sensor provided in this embodiment is lightweight and compact. It can use a single piezoresistive sensor with multiple protrusions to simultaneously perform multi-point detection within a small area (detecting multiple detection positions of the same location) or use multiple piezoresistive sensors to simultaneously detect multiple locations. Furthermore, compared to existing technologies where electrical signals between different detection positions are prone to coupling and have low resolution, this embodiment uses multiple channels to simultaneously acquire electrical signals, effectively improving the resolution between electrical signals and thus improving detection accuracy.

[0141] Reference Figure 15 , Figure 15 This is a flowchart illustrating the fourth operating method of the piezoresistive sensor in this embodiment of the invention. The piezoresistive sensor can be... Figure 1 The double-helix piezoresistive sensor shown in the image can also be... Figure 5 The image shows a wavy linear piezoresistive sensor. The fourth operating method may include steps S151 to S152, which are described below.

[0142] In step S151, one or more of the piezoresistive sensors are respectively attached to the detection area of ​​the test piece.

[0143] In some non-limiting embodiments, the test piece may be an aircraft wing (including the wings of civil aircraft and drones), a propeller (including drone propellers, ship propellers, submarine propellers, etc.), a hull, a submersible, a marine structure (including: drilling platforms, subsea oil pipelines, offshore oil storage tanks, etc.), and other types of machines or machine components that are easily subjected to mechanical stress during operation.

[0144] In step S152, the electrical signal transmitted through the wires of the piezoresistive sensor is measured to determine the pressure on the detection site.

[0145] The pressure applied to the detection area can be mechanical pressure, the source of which includes, but is not limited to, airflow pressure, liquid fluid pressure, pressure exerted directly by an object, etc.

[0146] In practical implementation, a pressure calibration experiment can be performed on the piezoresistive sensor first, measuring the resistance value of the piezoresistive sensor under different pressure values, thereby obtaining the pressure-resistance relationship curve or pressure-resistance correspondence table of the piezoresistive sensor; then, after attaching one or more piezoresistive sensors to the detection part of the test piece, the resistance value of the piezoresistive sensor can be determined based on the electrical signal transmitted by the wire of the piezoresistive sensor; then, based on the resistance value of the piezoresistive sensor, the pressure value corresponding to the resistance value can be found from the pressure-resistance relationship curve or pressure-resistance correspondence table, which is taken as the pressure applied to the detection part.

[0147] Furthermore, the detection location of the test piece is the surface of an aircraft wing; measuring the electrical signal transmitted through the wires of the piezoresistive sensor to determine the pressure on the detection location includes: measuring the electrical signal transmitted through the wires of the piezoresistive sensor to determine the airflow pressure on the surface of the aircraft wing.

[0148] Furthermore, the detection location of the test piece is the surface of the propeller blades; measuring the electrical signal transmitted through the wires of the piezoresistive sensor to determine the pressure on the detection location includes: measuring the electrical signal transmitted through the wires of the piezoresistive sensor to determine the fluid pressure on the surface of the propeller blades.

[0149] Furthermore, the detection area of ​​the test piece is the surface of the underwater section of the side of the hull; measuring the electrical signal transmitted by the wire of the piezoresistive sensor to determine the pressure on the detection area includes: measuring the electrical signal transmitted by the wire of the piezoresistive sensor to determine the water flow pressure on the surface of the underwater section of the side of the hull.

[0150] In this embodiment of the invention, by attaching one or more of the piezoresistive sensors (which may be the aforementioned double-helix piezoresistive sensors or the aforementioned wavy-line piezoresistive sensors) to the detection area of ​​the test piece listed above (including the surface of an aircraft wing, the surface of a propeller blade, and the surface of the lower part of a ship's hull below the waterline), the airflow pressure received by the aircraft wing during flight, the airflow pressure received by the propeller blade during UAV flight, or the water flow pressure received by the surface of the lower part of a ship's hull below the waterline during navigation, etc., can be accurately, sensitively, and in real time acquired. This helps to detect and judge dangers in a timely manner and to plan flight / navigation routes.

[0151] It should be noted that the above-described method for measuring the pressure on the detection area of ​​the test piece using the piezoresistive sensor is only a non-limiting embodiment. In specific implementations, the above method can also be used to measure the water flow pressure on the detection areas such as the surface of the drilling platform below the waterline, the outer surface of the subsea oil pipeline, and the surface of the offshore / subsea oil storage tank below the waterline, so as to promptly determine whether there is a risk of rupture in the test piece; it can also measure the interface stress between the contents and the shell of the container (in the case of contraction or expansion of the contents), which helps to prevent the expansion of the contents from causing excessive pressure on the shell, leading to shell rupture, or the contraction of the contents causing the contents to detach from the shell or vibrate / slide inside the container; it can also measure the pressure between the contact surfaces / mating surfaces of two contacting parts, which helps to promptly monitor the gap changes between the two contacting parts, ensuring that the two contacting parts have good and controllable positioning and mating gaps during operation.

[0152] It should be noted that, with Figure 10 or Figure 13 or Figure 14 The operating methods shown are different. When measuring the pressure on the detection part of the test piece, the back of the substrate of the piezoresistive sensor is usually attached (e.g., glued) to the outer surface of the detection part of the test piece. The double helical microtube or wavy microtube in the piezoresistive sensor is usually facing the fluid (exposed to the airflow or liquid fluid) or the object applying pressure (e.g., the contents of a container).

[0153] In this embodiment of the invention, since the piezoresistive sensor can be designed to be very lightweight and compact, and its substrate is often made of flexible material, it can closely fit the detection part of the test object during operation. Furthermore, the microtube of the piezoresistive sensor can be directly exposed to airflow or liquid fluid or directly attached to the object under pressure, thereby effectively improving the sensitivity and accuracy of measurement in various application scenarios.

[0154] Furthermore, the piezoresistive sensor has a temperature measuring device for measuring the temperature value of the piezoresistive sensor; measuring the electrical signal transmitted through the wires of the piezoresistive sensor to determine the pressure value of the detection part includes: measuring the electrical signal transmitted through the wires of the piezoresistive sensor and the temperature value of the piezoresistive sensor to determine the pressure value of the detection part.

[0155] It is understandable that in application scenarios where the temperature of the measurement environment or the measured object itself is unstable or even prone to drastic changes (e.g., when measuring the airflow pressure on the fuselage or wing skin of an aircraft during flight, where the ambient temperature drops drastically with altitude), the resistance value of the piezoresistive sensor will change significantly due to temperature variations. Therefore, to minimize the interference of temperature changes on the measured pressure value, a temperature measuring device (e.g., thermocouple, electronic thermometer, temperature sensor, etc.) can be fixed on the surface or inside the substrate of the piezoresistive sensor during measurement. When calculating the resistance change caused by pressure, the resistance change caused by temperature is removed, i.e.: resistance change caused by pressure = total resistance change - resistance change caused by temperature.

[0156] Reference Figure 16 , Figure 16 This is a schematic diagram of a double-helix piezoresistive sensor with a temperature measuring device according to an embodiment of the present invention. The temperature measuring device 50 can be a thermocouple, which can be embedded inside the substrate 11 of the double-helix piezoresistive sensor. Pairs of wires 13 extend from both ends of the temperature measuring device, and the wires 13 can be connected to a temperature signal acquisition and processing device.

[0157] In specific implementation, the following can be done: (1) First, a temperature calibration experiment is performed on the double-helix piezoresistive sensor to measure the resistance value under different temperature conditions, thereby obtaining the temperature-resistance relationship curve or temperature-resistance correspondence table of the double-helix piezoresistive sensor; (2) Then, multiple double-helix piezoresistive sensors with temperature measuring devices are attached to the detection part of the test piece according to the N×M regular arrangement or irregular arrangement; (3) Based on the electrical signal transmitted by the wire of the double-helix piezoresistive sensor, the change in the total resistance value of the sensor is determined, and based on the temperature signal transmitted by the wire of the temperature measuring device 50, the change in resistance value caused by temperature is determined; then, by calculating the difference between the change in total resistance value and the change in resistance value caused by temperature, the change in resistance value caused by pressure is obtained (the resistance value under a certain pressure can be determined); (4) The pressure value corresponding to the resistance value is found from the pressure-resistance relationship curve or pressure-resistance correspondence table, and is used as the pressure on the detection part.

[0158] In specific implementations, depending on the needs of the specific application scenario, the temperature measuring device can also be other existing components capable of temperature sensing or measurement. This embodiment of the invention does not limit the type of temperature measuring device or its connection relationship with the double-helix piezoresistive sensor.

[0159] Reference Figure 17 , Figure 17 Based on Figure 10 The flowchart illustrates a method for processing pulse wave signals obtained in [the process]. The method may include steps S171 to S172, which are described below.

[0160] In step S171, a denoising algorithm is used to denoise the pulse wave signal to obtain a denoised pulse wave signal.

[0161] Furthermore, a denoising algorithm is used to denoise the pulse wave signal to obtain a denoised pulse wave signal, including: using the Mallat algorithm to perform wavelet decomposition of the pulse wave signal at a preset level to obtain multiple pulse wave components; setting the pulse wave components with frequency values ​​higher than a first frequency threshold and the pulse wave components with frequency values ​​lower than a second frequency threshold to zero in the time domain to obtain the denoised pulse wave signal.

[0162] Further, after obtaining the denoised pulse wave signal, the method further includes: using a Butterworth filter to filter the denoised pulse wave signal to obtain a filtered pulse wave signal; performing a fast Fourier transform on the filtered pulse wave signal to obtain the spectrum of the filtered pulse wave signal; and using the frequency peaks in the spectrum of the filtered pulse wave signal as the resting respiratory rate of the subject to be tested.

[0163] In step S172, a heart rate extraction algorithm is used to determine the heart rate of the subject based on the denoised pulse wave signal.

[0164] Furthermore, the heart rate extraction algorithm is used to determine the heart rate of the subject based on the denoised pulse wave signal, which includes: performing a fast Fourier transform on the denoised pulse wave signal to obtain the spectrum of the denoised pulse wave signal; and taking the frequency peaks in the spectrum of the denoised pulse wave signal as the heart rate of the subject.

[0165] Furthermore, the method further includes: determining the average resistance of the piezoresistive sensor over a preset time period based on the pulse wave signal. The average resistance can be used to determine the temperature value of the detection site.

[0166] Furthermore, the method also includes: using a neural network algorithm to input the pulse wave signal into a neural network model, and using the output of the neural network model as the blood pressure value of the subject to be tested.

[0167] Furthermore, the detection site is the blood vessel of the subject, including a third detection position and a fourth detection position; the method further includes: using the difference between the first moment corresponding to the peak of the pulse wave signal at the third detection position and the second moment corresponding to the peak of the pulse wave signal at the fourth detection position as the pulse wave signal propagation duration at the third and fourth detection positions; determining the pulse wave signal propagation velocity based on the distance between the third and fourth detection positions and the pulse wave signal propagation duration. The pulse wave signal propagation velocity can be used to determine the vascular elasticity value of the subject.

[0168] Reference Figure 18 , Figure 18 Based on Figure 10 A schematic diagram of a processing device for pulse wave signals obtained in [the image / process]. The device may include:

[0169] The signal denoising module 181 is used to perform denoising processing on the pulse wave signal using a denoising algorithm to obtain a denoised pulse wave signal.

[0170] The heart rate detection module 182 is used to determine the heart rate of the subject based on the denoised pulse wave signal using a heart rate extraction algorithm.

[0171] For the principles, specific implementation, and beneficial effects of the pulse wave signal processing device, please refer to the preceding text and... Figure 10 The description of the operation method of the piezoresistive sensor shown in the figure, and Figure 17 The description of the pulse wave signal processing method obtained from the operation method of the piezoresistive sensor shown in the figure will not be repeated here.

[0172] This invention also provides a computer-readable storage medium storing a computer program. When the computer program is run by a processor, it executes the steps of the pulse wave signal processing method obtained by the above-described piezoresistive sensor operation method. The computer-readable storage medium may include non-volatile or non-transitory memory, and may also include optical discs, hard disk drives, solid-state drives, etc.

[0173] Specifically, in this embodiment of the invention, the processor can be a central processing unit (CPU), or it can be other general-purpose processors, digital signal processors (DSPs), application-specific integrated circuits (ASICs), field-programmable gate arrays (FPGAs), or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc. The general-purpose processor can be a microprocessor or any conventional processor.

[0174] It should also be understood that the memory in the embodiments of this application can be volatile memory or non-volatile memory, or may include both volatile and non-volatile memory. The non-volatile memory can be read-only memory (ROM), programmable read-only memory (PROM), erasable programmable read-only memory (EPROM), electrically erasable programmable read-only memory (EEPROM), or flash memory. The volatile memory can be random access memory (RAM), which is used as an external cache. By way of example, but not limitation, many forms of random access memory (RAM) are available, such as static RAM (SRAM), dynamic RAM (DRAM), synchronous DRAM (SDRAM), double data rate synchronous DRAM (DDR SDRAM), enhanced synchronous DRAM (ESDRAM), synchronous linked DRAM (SLDRAM), and direct rambus RAM (DR RAM).

[0175] This invention also provides a terminal, including a memory and a processor. The memory stores a computer program that can run on the processor. When the processor runs the computer program, it executes the steps of the pulse wave signal processing method obtained by the above-described piezoresistive sensor operation method. The terminal may include, but is not limited to, mobile phones, computers, tablets, and other terminal devices, and may also be servers, cloud platforms, etc.

[0176] It should be understood that the term "and / or" in this article is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, or B existing alone. Additionally, the character " / " in this article indicates that the preceding and following related objects have an "or" relationship.

[0177] In this application's embodiments, "multiple" refers to two or more. The descriptions of "first," "second," etc., appearing in this application's embodiments are merely illustrative and for distinguishing the objects being described; they do not indicate any order and do not imply a specific limitation on the number of devices in this application's embodiments, nor do they constitute any limitation on the embodiments of this application. It should be noted that the sequence numbers of each step in this embodiment do not represent a limitation on the execution order of the steps.

[0178] While the present invention has been disclosed above, it is not limited thereto. Any person skilled in the art can make various modifications and alterations without departing from the spirit and scope of the invention; therefore, the scope of protection of the present invention should be determined by the scope defined in the claims.

Claims

1. A piezoresistive sensor, characterized in that, include: Base; A microtube is located on the surface of the substrate, the two ends of the microtube are sealed and the interior contains a conductive liquid, wherein the microtube is in a double helix shape with both ends extending out, or the microtube is in a wavy shape with both ends extending out; the surface of the substrate has one or more protrusions; wherein one or more of the microtubes are respectively placed on the protrusions of the surface of the substrate in a one-to-one correspondence. Pairs of wires, each pair of wires extending from both ends of the microtube and electrically connected to the conductive liquid.

2. The piezoresistive sensor according to claim 1, characterized in that, The shape of one or more protrusions on the surface of the substrate is selected from one or more of the following: Arc-shaped, cylindrical, spherical.

3. The piezoresistive sensor according to claim 1, characterized in that, The substrate is composed of organosilicon materials.

4. The piezoresistive sensor according to claim 1, characterized in that, The microtube is double-helical, and from the center point of the helix, the two parts of the microtube respectively form a nested outer helix and an inner helix. The center point of the spiral is the dividing point between the two parts of the microtube.

5. The piezoresistive sensor according to claim 4, characterized in that, The thread pitch of the outer spiral ring and the thread pitch of the inner spiral ring are both less than or equal to the first threshold. And / or, The distance between the position with the largest thread curvature closest to the helical center point in the outer spiral and the position with the largest thread curvature closest to the helical center point in the inner spiral is less than or equal to the second threshold.

6. The piezoresistive sensor according to claim 1, characterized in that, The microtube is wavy, and the distance between two adjacent peaks in the wavy line is less than or equal to the third threshold. And / or, The microtube is wavy, and the distance between adjacent peaks and troughs in the wavy line is greater than or equal to the fourth threshold.

7. The piezoresistive sensor according to claim 1, characterized in that, The conductive liquid is selected from: Liquid metals, conductive gels, ionic liquids, and salt solutions.

8. The piezoresistive sensor according to claim 1, characterized in that, The piezoresistive sensor has a pressure loading device for applying variable pressure from the back side of the substrate to the microtube.

9. The piezoresistive sensor according to claim 8, characterized in that, The pressure loading device includes an air bladder and provides pressure by inflating the air bladder; The air pressure of the airbag varies, resulting in different pressures supplied to the microtube.

10. A method for forming a piezoresistive sensor as described in any one of claims 1 to 9, characterized in that, include: The conductive liquid is added into the microtube, and both ends of the microtube are sealed and connected to the wires. The dividing point between the two parts of the microtube is determined as the helical center point. The two parts of the microtube are rotated around the helical center point to obtain a planar double helix structure, or the microtube is bent into a wavy line structure. Place one or more of the microtubes on the surface of the substrate; Before placing one or more of the microtubes on the surface of the substrate, the method further includes: A substrate is formed, the surface of which has one or more protrusions; The substrate is subjected to heat curing treatment; The one or more microtubes are respectively placed on the protrusions on the surface of the substrate.

11. A method for operating a piezoresistive sensor according to any one of claims 1 to 9, characterized in that, include: One or more microtubes of the piezoresistive sensor are respectively attached to the detection site of the subject; The electrical signal transmitted through the wires of the piezoresistive sensor is measured to determine the pulse wave signal at the detection site.

12. The method of operating the piezoresistive sensor according to claim 11, characterized in that, The process of attaching one or more microtubes of the piezoresistive sensor to the detection site of the subject includes: One or more of the microtubes of the piezoresistive sensor are respectively attached to the three detection positions of the wrist of the person being tested: the cun pulse, guan pulse, and chi pulse.

13. The method of operating the piezoresistive sensor according to claim 11, characterized in that, The piezoresistive sensor has a pressure loading device for applying variable pressure from the back side of the substrate to the microtube; During the measurement of the electrical signal transmitted by the piezoresistive sensor, the pressure provided by the pressure loading device is changed to determine the pulse wave signal corresponding to different pressures.

14. The method of operating the piezoresistive sensor according to claim 11, characterized in that, The process involves attaching microtubes of one or more piezoresistive sensors to the detection sites of the subject, including: The microtubes of at least two of the piezoresistive sensors are respectively attached to the first detection location of the brachial artery and the second detection location of the radial artery of the subject.

15. A method for processing pulse wave signals obtained based on the operation method of the piezoresistive sensor according to any one of claims 11 to 14, characterized in that, include: Based on the pulse wave signal, determine the average resistance of the piezoresistive sensor over a preset time period; The average resistance value is used to determine the temperature value of the detection site.

16. A method for processing pulse wave signals obtained based on the operation method of the piezoresistive sensor according to any one of claims 11 to 14, characterized in that, include: A denoising algorithm is used to denoise the pulse wave signal to obtain a denoised pulse wave signal. A heart rate extraction algorithm is used to determine the heart rate of the subject based on the denoised pulse wave signal.

17. The method for processing the pulse wave signal obtained by the operation method of the piezoresistive sensor according to claim 16, characterized in that, A denoising algorithm is used to denoise the pulse wave signal, resulting in a denoised pulse wave signal including: The Mallat algorithm is used to perform wavelet decomposition of the pulse wave signal at a preset level to obtain multiple pulse wave components; The pulse wave components with frequency values ​​higher than a first frequency threshold and those with frequency values ​​lower than a second frequency threshold are set to zero in the time domain to obtain the denoised pulse wave signal.

18. The method for processing the pulse wave signal obtained by the operation method of the piezoresistive sensor according to claim 17, characterized in that, The heart rate of the subject is determined using a heart rate extraction algorithm based on the denoised pulse wave signal, including: The denoised pulse wave signal is subjected to a fast Fourier transform to obtain the spectrum of the denoised pulse wave signal. The peak frequency in the spectrum of the denoised pulse wave signal is taken as the heart rate of the subject.

19. The method for processing the pulse wave signal obtained by the operation method of the piezoresistive sensor according to claim 16, characterized in that, After obtaining the denoised pulse wave signal, the method further includes: A Butterworth filter is used to filter the denoised pulse wave signal to obtain a filtered pulse wave signal. The filtered pulse wave signal is subjected to a fast Fourier transform to obtain the spectrum of the filtered pulse wave signal; The peak frequency in the filtered pulse wave signal spectrum is taken as the resting respiratory rate of the subject.

20. A method for processing pulse wave signals obtained based on the operation method of the piezoresistive sensor according to any one of claims 11 to 14, characterized in that, The method further includes: A neural network algorithm is used to input the pulse wave signal into a neural network model, and the output of the neural network model is used as the blood pressure value of the subject.

21. A method for processing pulse wave signals obtained based on the operation method of the piezoresistive sensor according to any one of claims 11 to 14, characterized in that, The detection site is the blood vessels of the person being tested, including a third detection location and a fourth detection location; The method includes: The difference between the first moment corresponding to the peak of the pulse wave signal at the third detection position and the second moment corresponding to the peak of the pulse wave signal at the fourth detection position is taken as the pulse wave signal propagation time at the third and fourth detection positions. The pulse wave signal propagation velocity is determined based on the distance between the third and fourth detection positions and the duration of the pulse wave signal propagation. The pulse wave signal transmission velocity is used to determine the vascular elasticity value of the subject being tested.

22. An operating method for a piezoresistive sensor based on any one of claims 1 to 9, characterized in that, include: One or more of the piezoresistive sensors are respectively attached to the detection area of ​​the test piece; The electrical signal transmitted through the wires of the piezoresistive sensor is measured to determine the pressure applied to the detection site.

23. The method of operating the piezoresistive sensor according to claim 22, characterized in that, The test piece is selected from one or more of the following: Aircraft wings, propellers, engine fans, ship hulls, submarines, and marine structures.

24. The method of operating the piezoresistive sensor according to claim 22, characterized in that, The testing area of ​​the test piece is the surface of the aircraft wing; Measuring the electrical signal transmitted through the wires of the piezoresistive sensor to determine the pressure on the detection site includes: The electrical signal transmitted through the wires of the piezoresistive sensor is measured to determine the airflow pressure on the surface of the aircraft wing.

25. The method of operating the piezoresistive sensor according to claim 22, characterized in that, The testing area of ​​the test piece is the surface of the propeller blades; Measuring the electrical signal transmitted through the wires of the piezoresistive sensor to determine the pressure on the detection site includes: The electrical signal transmitted through the wires of the piezoresistive sensor is measured to determine the fluid pressure on the surface of the propeller blades.

26. The method of operating the piezoresistive sensor according to claim 22, characterized in that, The testing area of ​​the component to be tested is the surface of the side of the ship below the waterline; Measuring the electrical signal transmitted through the wires of the piezoresistive sensor to determine the pressure on the detection site includes: The electrical signal transmitted through the wires of the piezoresistive sensor is measured to determine the water pressure on the surface of the underwater section of the hull.

27. The method of operating the piezoresistive sensor according to claim 22, characterized in that, The piezoresistive sensor has a temperature measuring device for measuring the temperature value of the piezoresistive sensor. Measuring the electrical signal transmitted through the wires of the piezoresistive sensor to determine the pressure on the detection site includes: The pressure on the detection site is determined by measuring the electrical signal transmitted through the wires of the piezoresistive sensor and the temperature value of the piezoresistive sensor.

28. A processing apparatus for pulse wave signals obtained based on the operation method of the piezoresistive sensor according to any one of claims 11 to 14, characterized in that, include: The resistance value determination module is used to determine the average resistance of the piezoresistive sensor within a preset time period based on the pulse wave signal. The average resistance value is used to determine the temperature value of the detection site.

29. A processing apparatus for pulse wave signals obtained based on the operation method of the piezoresistive sensor according to any one of claims 11 to 14, characterized in that, include: The signal denoising module performs denoising processing on the pulse wave signal to obtain a denoised pulse wave signal. The heart rate detection module is used to determine the heart rate of the subject based on the denoised pulse wave signal using a heart rate extraction algorithm.

30. A processing apparatus for pulse wave signals obtained based on the operation method of the piezoresistive sensor according to any one of claims 11 to 14, characterized in that, include: The blood pressure value determination module is used to input the pulse wave signal into a neural network model using a neural network algorithm, and use the output of the neural network model as the blood pressure value of the subject to be tested.

31. A processing apparatus for pulse wave signals obtained based on the operation method of the piezoresistive sensor according to any one of claims 11 to 14, characterized in that, The detection site is the blood vessels of the person being tested, including a third detection location and a fourth detection location, including: The signal propagation duration determination module is used to take the difference between the first moment corresponding to the peak of the pulse wave signal at the third detection position and the second moment corresponding to the peak of the pulse wave signal at the fourth detection position as the pulse wave signal propagation duration at the third detection position and the fourth detection position. The signal transmission velocity determination module is used to determine the pulse wave signal transmission velocity based on the distance between the third and fourth detection positions and the pulse wave signal transmission duration. The pulse wave signal transmission velocity is used to determine the vascular elasticity value of the subject being tested.

32. A computer-readable storage medium having a computer program stored thereon, characterized in that, When the computer program is run by the processor, it executes the steps of the pulse wave signal processing method obtained by the piezoresistive sensor operation method according to claim 15, or the steps of the pulse wave signal processing method obtained by the piezoresistive sensor operation method according to any one of claims 16 to 19, or the steps of the pulse wave signal processing method obtained by the piezoresistive sensor operation method according to claim 20, or the steps of the pulse wave signal processing method obtained by the piezoresistive sensor operation method according to claim 21.

33. A terminal comprising a memory and a processor, wherein the memory stores a computer program capable of running on the processor, characterized in that, When the processor runs the computer program, it executes the steps of the pulse wave signal processing method obtained by the piezoresistive sensor operation method according to claim 15, or executes the steps of the pulse wave signal processing method obtained by the piezoresistive sensor operation method according to any one of claims 16 to 19, or executes the steps of the pulse wave signal processing method obtained by the piezoresistive sensor operation method according to claim 20, or executes the steps of the pulse wave signal processing method obtained by the piezoresistive sensor operation method according to claim 21.

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