A three-dimensional strain terahertz sensor, a preparation method, a detection system and a method

Abstract

The application discloses a three-dimensional strain terahertz sensor, which comprises at least one flexible substrate and a terahertz metasurface unit array constructed on the flexible substrate, and each layer of the flexible substrate forms a laminated structure. The geometric structures of units in the terahertz metasurface unit arrays of different layers are different. The unit structure of the terahertz metasurface unit array comprises one of a circular complementary open resonant ring, a square complementary open resonant ring, a quarter circular ring and a rectangular block or any combination. On the flexible substrate, the terahertz metasurface unit array is constructed through a photolithography or etching process. Based on the cooperative design of the flexible substrate and the terahertz metasurface unit array, the application realizes accurate detection of micro-strain of a biological sample through a strong coupling mechanism of structural deformation and electromagnetic response.

Description

Technical Field

[0001] This invention belongs to the field of biological detection technology, and specifically relates to a three-dimensional strain terahertz sensor, its preparation method, detection system, and method. Background Technology

[0002] With the development of biomedical detection technology towards the microscale and precision, the study of the mechanical properties of biological tissues and the dynamic detection of cellular-scale mechanical responses have become urgent needs in fields such as tissue testing and disease prevention. In the terahertz band, due to its unique physical properties, such as sensitivity to water molecules, high penetrability, and low damage to biological tissues, terahertz detection technology has broad application prospects in the biomedical field. However, traditional resistive and capacitive strain sensors rely on the detection principle of resistance changes caused by the deformation of conductive materials. These sensors suffer from insufficient sensitivity and high signal-to-noise ratio in detecting minute deformations. Furthermore, rigid substrate materials such as silicon are difficult to conform to the complex curved shapes of biological tissues, limiting detection accuracy and making it difficult to meet the demands for high-precision, multi-dimensional detection. Summary of the Invention

[0003] In one aspect of this disclosure, a three-dimensional strain terahertz sensor includes:

[0004] At least one flexible substrate, and an array of terahertz metasurface units constructed on the substrate.

[0005] The sensor comprises a multi-layered stacked structure, namely,

[0006] The first sensing layer is stacked on the bottom flexible substrate to form a metasurface unit array with the first resonant characteristics;

[0007] The second sensing layer is stacked on top of the first sensing layer through an intermediate flexible substrate to form a metasurface unit array with second resonant characteristics.

[0008] The third sensing layer is stacked on top of the second sensing layer through an upper flexible substrate to form a metasurface unit array with third resonant characteristics.

[0009] The multilayer metasurface unit array, with its differentiated geometric structure corresponding to strain responses in different directions, collectively achieves three-dimensional strain detection.

[0010] Preferably, a flexible polymer material is selected as the substrate, exemplarily selected from polydimethylsiloxane (PDMS), Dragon Skin thermoplastic elastomer, or styrene-ethylene-butene-styrene copolymer (SEBS) and other hyperelastic materials; the conductive layer material of the metasurface unit array is selected from a high conductivity material, exemplarily silver nanowires, graphene, or metal thin films; the processing technology includes one or a combination of photolithography etching, blade coating, or 3D printing additive manufacturing.

[0011] In one aspect of this disclosure, a three-dimensional strain terahertz sensor includes:

[0012] At least one PDMS flexible substrate, and an array of terahertz metasurface units constructed on the substrate.

[0013] One aspect of this disclosure is a method for fabricating a three-dimensional strain terahertz sensor, the method comprising:

[0014] PDMS with a thickness of 100-200 μm was selected as the substrate.

[0015] A terahertz metasurface array is constructed on the substrate using a high-conductivity metal as the material and photolithography or etching processes.

[0016] One aspect of this disclosure is a three-dimensional strain terahertz sensor detection system, which includes a terahertz transmitting module, a three-dimensional strain loading module, a terahertz signal receiving module, and a data acquisition and analysis module.

[0017] The terahertz signal generation module is used to generate terahertz waves, which are then incident on the biological tissue sample to be tested.

[0018] A three-dimensional strain terahertz sensor is mounted on the biological tissue sample. This sensor responds to terahertz waves and generates a resonance effect.

[0019] The three-dimensional strain loading module applies strain along the x, y, and z axes to the biological tissue sample.

[0020] The terahertz signal receiving module receives the reflection loss, phase, and frequency signals of the terahertz wave.

[0021] The data acquisition and analysis module parses the data received from the terahertz signal receiving module and calculates and outputs the three-dimensional strain components and critical strain threshold response of the biological tissue sample.

[0022] When the unit structure of the terahertz metasurface array is a circular complementary open resonant ring, and the complementary open resonant ring is configured as a strain-responsive reconstruction structure, when the z-axis compressive strain does not reach a critical value, the resonant rings remain physically isolated, and the surface current path does not change significantly; when the critical value is exceeded, adjacent resonant rings contact, the current path becomes continuous, and a step change in the resonant frequency is triggered. The critical strain value is jointly determined by the initial spacing of the metasurface units and the elastic modulus of the material.

[0023] One aspect of this disclosure is a method for detecting a three-dimensional strain terahertz sensor, the method comprising: placing a three-dimensional strain terahertz sensor on a biological tissue sample to be tested;

[0024] The surface of the three-dimensional strain terahertz sensor is irradiated by terahertz waves emitted by the terahertz emission module.

[0025] The terahertz signal receiving module is used to detect the changes in terahertz wave signal caused by the deformation of the biological tissue sample under test.

[0026] Using a data acquisition and analysis module, the detected signal is compared with the signal when the biological tissue is undeformed, and the three-dimensional strain of the biological tissue sample is calculated.

[0027] This disclosure is based on the collaborative design of a flexible substrate and a terahertz metasurface unit array, which achieves accurate detection of micro-strain in biological samples through a strong coupling mechanism of structural deformation and electromagnetic response. Attached Figure Description

[0028] The above and other objects, features, and advantages of exemplary embodiments of the present invention will become readily apparent from the following detailed description taken in conjunction with the accompanying drawings. Several embodiments of the invention are illustrated in the drawings by way of example and not limitation, wherein:

[0029] Figure 1 A schematic diagram of the overall structure of a three-dimensional strain terahertz sensor according to one embodiment of the present invention.

[0030] Figure 2 A schematic diagram illustrating the strain detection principle of a three-dimensional strain terahertz sensor in the x and y horizontal directions according to one embodiment of the present invention.

[0031] Figure 3 A schematic diagram of the current on the surface of the resonant ring near the threshold is shown in the z-normal direction critical strain threshold detection of a three-dimensional strain terahertz sensor according to one embodiment of the present invention.

[0032] Figure 4 A schematic diagram of a three-dimensional strain terahertz sensor system according to one embodiment of the present invention. Detailed Implementation

[0033] Researching existing terahertz sensors reveals the following shortcomings:

[0034] 1. Limited Dimensional Detection: Most strain sensor designs rely on the resonant frequency shift characteristics of metasurface unit arrays, which can only reflect planar uniaxial strain, i.e., in the x and y directions. They lack the ability to simultaneously analyze three-dimensional strain (especially normal z-axis compressive / tensile strain), making it difficult to accurately characterize the multi-directional mechanical coupling effects of biological tissues.

[0035] 2. Insufficient compatibility between substrate materials and devices: The design of rigid substrates is difficult to accurately fit the tissue surface, while the existing flexible substrates have high dielectric loss and imperfect impedance matching design with terahertz metasurface unit arrays, resulting in severe signal attenuation and low accuracy of micro-strain electromagnetic response.

[0036] 3. Limitation of Strain Detection Threshold: Existing terahertz sensors rely on the resonant frequency shift mechanism for strain detection, which manifests as a correlation between strain and resonant frequency. However, the continuously changing response mode lacks abrupt threshold characteristics. When the strain exceeds a certain critical value, the sensor's resonant frequency does not exhibit a step change, limiting its application in critical strain scenarios (e.g., sudden cell rupture).

[0037] To address these limitations, this disclosure proposes an innovative three-dimensional strain terahertz sensor and its application method, specifically targeting the current technical bottlenecks of terahertz sensors, such as single-dimensional detection, insufficient substrate and device compatibility, and strain detection threshold restrictions. By selecting appropriate flexible substrate materials, designing a multilayer metasurface unit array structure, and constructing a signal processing system, high sensitivity, a wide strain adaptation range, and simultaneous three-dimensional strain detection capabilities are achieved.

[0038] According to one or more embodiments, a three-dimensional strain terahertz sensor is specifically implemented with the following characteristics:

[0039] 1. Flexible Substrate Material and Structure Optimization: Single-layer or multi-layer polydimethylsiloxane (PDMS) is used as the flexible substrate for the sensor, with a thickness controlled between 100-200 μm to achieve matching with the terahertz band. For multi-layer structures, good interfacial fusion is achieved through interlayer stacking bonding processes (such as interface modification or layer-by-layer curing), ensuring interlayer bonding strength and controlling thickness uniformity errors to avoid stress transfer distortion caused by delamination. PDMS combines low dielectric loss (tanδ < 0.01), high flexibility (elastic modulus E: 0.5-2 MPa), and good biocompatibility, effectively conforming to the complex curved shapes of biological tissues and effectively characterizing micron-level strain. Simultaneously, by rationally designing the substrate thickness, impedance matching with the metasurface unit array structure is achieved, improving the strain-electromagnetic response coupling effect and reducing interfacial reflection loss.

[0040] 2. Equivalent Circuit Design of Terahertz Metasurface Unit Array Structure: A terahertz metasurface unit array is integrated on the surface of each flexible substrate. The unit material is a highly conductive metal, such as gold (Au). Its structure includes, but is not limited to:

[0041] A circular complementary split ring resonator (CSRR) has ring openings parallel to the polarization direction. By adjusting the spacing between the ring openings, the capacitance (C) of the equivalent circuit is changed, thus enabling horizontal strain detection.

[0042] The Square Complementary Split Ring Resonator (SSRR) mainly achieves horizontal strain detection by adjusting the inductance (L) of the equivalent circuit through adjusting the side length.

[0043] The above structural design is mainly based on the equivalent circuit model of LC capacitor and inductor. The equivalent capacitance is mainly determined by the ring width and its spacing, while the equivalent inductance is determined by the length of the metasurface unit array structure. On the same substrate, the metasurface adopts a periodic array arrangement, consisting of identical unit structures repeatedly extending along the x / y directions in the plane.

[0044] 3. Three-dimensional strain synchronous detection mechanism: Under the premise of horizontal polarization, i.e., the electric field direction is parallel to the x-axis, the strain in the x-direction directly affects the equivalent capacitance of the circuit, causing a shift in the resonant frequency; while the change in the array spacing in the y-direction directly affects the equivalent inductance of the circuit, leading to secondary modulation of the resonant frequency; for strain detection in the z-direction, for a single-layer structure, z-axis compression leads to uniform expansion of the metasurface unit array, and the resonant frequency shift is dominated by the product of capacitance C and inductance L; for a multilayer structure, z-axis compression enhances the near-field coupling between layers, and the increase in equivalent capacitance causes a leftward shift in the resonant frequency.

[0045] 4. Strain Threshold Abrupt Change Detection Mechanism: The three-dimensional strain detection mechanism of the sensor is based on the deformation-electromagnetic coupling effect of the metasurface unit array. When the compressive strain applied in the z-axis direction does not reach the critical threshold, each resonant ring unit remains physically isolated, and the surface current is confined within a single resonant unit. At this time, the sensor corresponds to a resonant frequency. When the z-axis strain exceeds the critical threshold, the metal structure of adjacent resonant rings expands laterally due to the Poisson effect, resulting in physical contact and forming a continuous conductive network. The surface current path changes from a localized resonant mode to a global resonant mode, and the magnetic field distribution evolves from discrete eddy currents to large-scale eddy currents. This structure-electromagnetic coupling effect induces a step change in the resonant mode, manifested as a nonlinear abrupt change in the resonant frequency. By detecting the mapping relationship between the frequency jump point and its strain threshold, accurate detection of strain in the z-axis direction is achieved.

[0046] According to one or more embodiments, the fabrication of a three-dimensional strain terahertz sensor includes the following:

[0047] (1) Sensor fabrication: PDMS with a thickness of 100-200μm is selected as the substrate. Subsequently, a terahertz metasurface unit array structure is constructed on the substrate using a high conductivity metal (such as gold, Au) with the aid of photolithography or etching processes. Specific structural forms include circular complementary open-ring resonators, square complementary open-ring resonators, and quarter-ring structures.

[0048] (2) Strain detection system setup: Install a signal transmitting unit (such as a rectangular horn antenna) to transmit terahertz waves; install a signal detection unit (such as a vector network analyzer) to receive reflected or transmitted terahertz wave signals; and equip a signal processing unit to analyze the detected signals to determine the three-dimensional strain state. (3) Strain detection operation: Place the biological tissue or cell to be tested on the sensor. Irradiate the sensor surface with terahertz waves emitted by the signal transmitting unit, and use the signal detection unit to detect the changes in terahertz wave signals caused by tissue or cell deformation. Finally, with the help of the signal processing unit, compare the detected signal with the signal when there is no deformation to calculate the three-dimensional strain of the biological tissue or cell.

[0049] like Figure 1 The diagram shows the overall structure of the sensor disclosed herein, including a PDMS substrate and a terahertz metasurface unit array structure. Figure 1 The English terms in the text include:

[0050] 1. Horizontal Polarization

[0051] 2.x(E)——x(electric field)

[0052] 3. y(H)——y(magnetic field)

[0053] 4. z(k) — z (wave vector)

[0054] 5. Quarter-SRR – a quarter-resonant ring

[0055] 6. Square-SRR – Square Resonant Ring

[0056] 7. Circular-SRR – Circular Resonant Ring

[0057] 8. x-direction strain

[0058] 9. y-direction strain

[0059] 10. z-direction strain

[0060] 11. PDMS – Polydimethylsiloxane

[0061] 12. metal — metal

[0062] 13. Layer 1, Layer 2, Layer 3 — Layer 1, Layer 2, Layer 3

[0063] Figure 1 This paper describes a three-dimensional strain sensor structure based on a terahertz metasurface unit array (TSU). This sensor utilizes the resonant characteristics of terahertz waves to detect minute deformations and can be applied to three-dimensional strain analysis of biological tissues or cells. In the TSU structure, the sensor substrate is composed of polydimethylsiloxane (PDMS) with a thickness of 100-200 μm. The TSU array structure is constructed on the PDMS substrate using a highly conductive metal (such as gold or silver) through photolithography or etching. These structures include circular complementary split-ring resonators (SRR), square complementary split-ring resonators (SRR), and quarter-circular ring resonators (SRR). The described three-layer stack is only an exemplary embodiment of the metasurface spatial arrangement; the actual number of layers and the arrangement order can be dynamically adjusted according to detection requirements, and its technical effect does not depend on a specific layer sequence relationship. The sensor structure features include:

[0064] 1. The directions of the horizontally polarized electric and magnetic fields;

[0065] 2. A three-layer strain sensor structure based on a segmented resonant ring;

[0066] 3. A multilayer sensor structure made of polydimethylsiloxane (PDMS) and gold (Au) materials.

[0067] Therefore, this sensor is a multilayer sensor structure made of PDMS and gold (Au) materials, wherein:

[0068] 1. Horizontal polarization describes the directions of horizontally polarized electric and magnetic fields, where the electric field is in the x-direction (E), the magnetic field is in the y-direction (H), and the propagation direction is in the z-direction (k).

[0069] 2. Three-layer strain sensor structure: Based on a segmented resonant ring, this three-layer strain sensor structure is used to detect plane strain in the x and y directions and vertical strain in the z direction.

[0070] 3. Multi-layer sensor structure, including multi-layer sensor structures made of PDMS and metal materials, which include quarter-circular resonant rings (Quarter-SRR), square resonant rings (SRR), and circular resonant rings (Circular-SRR).

[0071] The three-dimensional strain detection system disclosed herein includes a signal transmitting unit (such as a rectangular horn antenna) for transmitting terahertz waves; a signal detection unit (such as a vector network analyzer) for receiving reflected or transmitted terahertz wave signals; and a signal processing unit for analyzing the detected signals to determine the three-dimensional strain state. The strain detection operation includes the following steps:

[0072] Place the biological tissue or cells to be tested onto the sensor;

[0073] Terahertz waves are emitted by the signal transmitting unit to irradiate the sensor surface;

[0074] The signal detection unit is used to detect changes in terahertz wave signals caused by tissue or cell deformation;

[0075] Finally, with the help of the signal processing unit, the detected signal is compared with the signal when it is not deformed, and the three-dimensional strain of the biological tissue or cell is calculated.

[0076] Therefore, the terahertz metasurface unit array-based sensor disclosed herein can provide highly sensitive strain detection, suitable for applications requiring precise measurement of minute deformations, such as the analysis of cellular mechanical properties in biomedical research. Through the interaction between terahertz waves and the sensor structure, the strain of biological tissues or cells in different directions can be accurately measured.

[0077] like Figure 2 As shown, the principle of strain detection in the x and y horizontal directions of the sensor is explained, and the changes in the array structure in different directions are shown to affect the equivalent capacitance and inductance, and thus the resonant frequency. Figure 2 The following English terms are included:

[0078] S-Parameters [Magnitude] — S-parameters [magnitude]

[0079] Frequency / GHz — Frequency / Gigahertz

[0080] x-direction strain

[0081] ΔC→Δf — Capacitance change → Frequency change

[0082] y-direction strain

[0083] ΔL→Δf — Inductance change → Frequency change

[0084] Figure 2 This illustrates the effect of strain in the x and y directions on the resonant frequency. The left figure shows the effect of strain in the x direction on the equivalent capacitance of the circuit, and the right figure shows the effect of strain in the y direction on the equivalent inductance of the circuit. It includes the following content.

[0085] Strain detection in the x-direction: When the sensor is subjected to strain in the x-direction, it affects the equivalent capacitance of the circuit. The red curve in the figure represents the change in reflection loss S11 after strain is applied in the x-direction. As the strain increases, the equivalent capacitance of the circuit changes, causing a shift in the resonant frequency, thereby affecting the amplitude of reflection loss S11.

[0086] Strain detection in the y-direction: When the sensor is subjected to strain in the y-direction, it affects the equivalent inductance of the circuit. The red curve in the figure represents the change in reflection loss S11 after strain is applied in the y-direction. Similarly, as the strain increases, the equivalent inductance of the circuit changes, causing a shift in the resonant frequency, which in turn affects the amplitude of reflection loss S11.

[0087] Strain in either the x- or y-direction will alter the resonant frequency of the resonant ring. This frequency change can be detected by measuring the amplitude change of the reflection loss S11. By comparing the frequency response before and after applying strain, the three-dimensional strain of biological tissue or cells can be accurately calculated.

[0088] Here, strain detection is based on the frequency response of a terahertz metasurface resonator. When the sensor is subjected to strain, the geometry of the resonator changes, altering the circuit's equivalent capacitance or inductance, resulting in a shift in the resonant frequency. By monitoring this frequency change, highly sensitive detection of minute strains can be achieved.

[0089] like Figure 3 The diagram shows the critical strain threshold detection along the z-normal direction and the current distribution on the surface of the resonant ring near the threshold. The structure features a uniformly extended rectangular metal contact. The current distribution indicates that the two originally independent metal rings are now connected, leading to an increased current path, a significant increase in equivalent inductance, and consequently, a sudden decrease in the resonant frequency. After contact, the equivalent inductance increases by approximately 2.5 times. Figure 3 The English terms in the text include:

[0090] Surface current

[0091] Frequency

[0092] Phase

[0093] Maximum Plot

[0094] S-Parameters [Magnitude] — S-parameters [magnitude]

[0095] Figure 3 The diagram shows the longitudinal compressive strain test results: (1) When the critical threshold is not reached, the electric field of the resonant ring is distributed in a ring shape; (2) When the critical threshold is exceeded, the electric field of the resonant ring exhibits a longitudinal distribution; (3) The resonant frequency changes significantly before and after the abrupt change. The left diagram shows that when the critical strain threshold is not reached, the surface current distribution of the resonant ring is ring-shaped. At this time, the two metal rings are independent, and the current circulates in each ring. The middle diagram shows that when the critical strain threshold is exceeded, the surface current distribution of the resonant ring exhibits a longitudinal distribution. At this time, the two originally independent metal rings are connected due to the strain, resulting in an increase in the current path. Due to the increase in the current path, the equivalent inductance suddenly increases, which leads to a sudden decrease in the resonant frequency. After contact, the equivalent inductance increases by about 2.5 times, which shows that the structural change has a significant impact on the resonant characteristics. The right diagram shows the change of S-parameters with frequency under different conditions. The red curve in the figure represents the change in the amplitude of the S-parameters of the resonant ring near the critical strain threshold. It can be seen that the resonant frequency changes significantly after the critical strain threshold is exceeded. This frequency change can be used to detect the strain threshold, because when the strain exceeds the threshold, the resonant frequency of the resonant ring will decrease significantly.

[0096] like Figure 4 The image shows a three-dimensional strain terahertz sensor detection system. This system consists of a terahertz emission module, a flexible sample holder, a three-dimensional strain loading module, a signal receiving module, and an analysis module. When a terahertz wave is incident on the sample, the metasurface structure responds to the signal and generates a resonance effect. The loading module applies strain along the x / y / z axes, the receiving module acquires the amplitude, phase, and frequency signals, and the analysis module decouples the signals and outputs the three-dimensional strain components and the critical strain threshold response. Figure 4 The Chinese and English terms include:

[0097] Terahertz wave

[0098] Terahertz signal generator

[0099] Biological tissue sample to be tested

[0100] 3-dimensional strain sensor

[0101] Strain applying device

[0102] Terahertz signal receiver

[0103] Reflection Loss

[0104] Resonant frequency 1

[0105] Resonant frequency 2

[0106] Frequency

[0107] Figure 4 The three-dimensional strain detection system includes a terahertz emission and absorption device, a strain application device, and a data acquisition and analysis module. The terahertz wave emission and absorption device includes a terahertz signal generator, such as a rectangular horn antenna, which generates terahertz waves that are incident on the surface of the biological tissue sample to be tested. The three-dimensional strain sensor structure on the sample responds to the terahertz waves and generates a resonance effect. During three-dimensional strain detection, the three-dimensional strain sensor is tightly attached to the surface of the biological tissue or cell (such as skin, myocardial tissue, or in vitro cell culture layer). The strain application device applies strain along the x, y, and z axes to the sample, simulating the mechanical environment under physiological or pathological conditions. The terahertz signal receiver collects reflection loss, phase, and frequency signals. The data acquisition and analysis module analyzes the received signals and outputs the three-dimensional strain components of the sample and the critical strain threshold response. The three-dimensional strain detection system emits terahertz waves to the biological tissue sample via the terahertz signal generator, and the three-dimensional strain sensor on the sample responds to these waves and generates a resonance effect. Then, the strain application device applies strain to the sample in different directions, the terahertz signal receiver collects the signal changes, and finally the analysis module processes these signals to obtain the three-dimensional strain information of the sample and the critical strain threshold response. This system can be used to accurately measure and analyze the strain characteristics of biological tissues or materials in different directions.

[0108] Figure 4 The example shown illustrates a clinical application scenario where the sensor is attached to the surface of myocardial tissue. A flexible PDMS substrate (100-200 μm thick) is bonded to the tissue surface using a bio-adhesive. The multilayer metasurface unit array sensor undergoes a change in resonance response as the tissue deforms. When the z-axis compressive strain exceeds a critical threshold, the resonant rings come into contact, causing a sudden change in the resonant frequency, providing a real-time early warning of tissue mechanical failure.

[0109] Therefore, the beneficial effects of the three-dimensional strain sensor disclosed herein include:

[0110] (1) It has ultra-high detection sensitivity:

[0111] Based on the synergistic design of a flexible polydimethylsiloxane (PDMS) substrate (dielectric loss tanδ < 0.01) and a terahertz metasurface unit array, precise detection of micro-strain (<0.1%) is achieved through a strong coupling mechanism between structural deformation and electromagnetic response. The low elastic modulus of PDMS (0.5-2 MPa) effectively conducts minute displacements (micrometer-level) at the biological tissue / cell scale, while the equivalent circuit model (LC resonance) of the metasurface unit converts mechanical strain into resonant frequency shift, significantly outperforming traditional piezoresistive sensors.

[0112] (2) Possesses three-dimensional strain analysis capability:

[0113] In this disclosure, a multi-physics decoupling design is adopted, which independently modulates the equivalent capacitance (C) and inductance (L) by changing the array spacing in the x / y directions, and combines the interlayer coupling capacitance increment caused by z-axis compression to achieve synchronous detection of triaxial strain components.

[0114] The threshold mutation response mechanism causes the metasurface unit spacing to shrink to λ / 10 (λ is the terahertz wavelength) when the z-axis compressive strain exceeds the critical value (ε_z>ε_critical), resulting in a step change in the resonant frequency, which provides a high signal-to-noise ratio early warning signal for the mechanical failure point of biotissue.

[0115] (3) It has biocompatibility and broad strain compatibility:

[0116] The flexibility and biocompatibility of the PDMS substrate allow it to closely conform to the curved surfaces of complex biological tissues, avoiding interfacial stress distortion. Through mutation threshold detection algorithms and in vivo-compatible design, it can monitor pathological phenomena such as cell membrane rupture in real time, providing high-precision mechanical characterization for disease detection, intraoperative navigation and other scenarios.

[0117] It is worth noting that although the spirit and principles of this invention have been described with reference to several specific embodiments, it should be understood that this invention is not limited to the disclosed specific embodiments, and the division of aspects does not imply that the features in these aspects cannot be combined; such division is merely for the convenience of description. This invention is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims.

Claims

1. A three-dimensional strain terahertz sensor, characterized in that, The sensor includes: At least one flexible substrate, and Terahertz metasurface unit array constructed on the flexible substrate The flexible substrates form a stacked structure.

2. The sensor according to claim 1, characterized in that, The geometric structures of the cells in the terahertz metasurface arrays of different layers are different.

3. The sensor according to claim 2, characterized in that, The unit structure of the terahertz metasurface array includes one or any combination of circular complementary open-ring resonators, square complementary open-ring resonators, quarter-circular rings, and rectangular blocks.

4. The sensor according to claim 2, characterized in that, A terahertz metasurface unit array is constructed on the flexible substrate using photolithography or etching processes.

5. A method for fabricating a three-dimensional strain terahertz sensor, characterized in that, The method includes: A terahertz metasurface unit array is constructed on a flexible polymer substrate.

6. The method according to claim 5, characterized in that, The flexible polymer material is polydimethylsiloxane (PDMS), Dragon Skin thermoplastic elastomer, or a superelastic material. Preferably, the superelastic material is a styrene-ethylene-butene-styrene copolymer (SEBS); preferably, the conductive layer material of the metasurface unit array is a high conductivity material. Preferably, the high conductivity material is silver nanowires, graphene, or a metal thin film; Preferably, the fabrication process for constructing the terahertz metasurface unit array on the flexible substrate includes one or any combination of photolithography etching, blade coating, or 3D printing additive manufacturing.

7. A three-dimensional strain terahertz sensor detection system, characterized in that, The system includes, but is not limited to: a terahertz emission module, a three-dimensional strain loading module, a terahertz signal receiving module, and a data acquisition and analysis module. The terahertz signal generation module is used to generate terahertz waves, which are incident on the biological tissue or cell sample to be tested. The biological tissue sample is equipped with a three-dimensional strain terahertz sensor as described in claim 1, which responds to terahertz waves and generates a resonance effect. The three-dimensional strain loading module applies strain along the x, y, and z axes to the biological tissue sample. The terahertz signal receiving module receives the reflection loss, phase, and frequency signals of the terahertz wave. The data acquisition and analysis module parses the data received from the terahertz signal receiving module and calculates and outputs the three-dimensional strain components and critical strain threshold response of the biological tissue sample.

8. The detection system according to claim 7, characterized in that, When the unit structure of the terahertz metasurface array is a circular complementary open resonant ring, and the complementary open resonant ring is configured as a strain-responsive reconstruction structure, when the z-axis compressive strain does not reach the critical value, the resonant ring remains physically isolated and the surface current path does not change significantly; when the critical value is exceeded, adjacent resonant rings come into contact, the current path becomes continuous, and a step change in the resonant frequency is triggered.

9. A method for detecting three-dimensional strain terahertz sensors, characterized in that, The method includes: The three-dimensional strain terahertz sensor as described in claim 1 is placed on the biological sample to be tested; The surface of the three-dimensional strain terahertz sensor is irradiated by terahertz waves emitted by the terahertz emission module. The terahertz signal receiving module is used to detect the changes in terahertz wave signal caused by the deformation of the biological tissue sample under test. Using a data acquisition and analysis module, the detected signal is compared with the signal when the biological tissue is undeformed, and the three-dimensional strain of the biological tissue sample is calculated.

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