A distributed multimodal flexible sensor and multimodal sensing method based on fiber Bragg grating

Abstract

A distributed multimodal flexible sensor and multimodal sensing method based on fiber Bragg gratings (FBGs) comprises a dielectric layer for enhancing non-contact electric field response and detecting the proximity of a target object; a fiber sensing layer, disposed beneath the dielectric layer, comprising S-shaped distributed fiber Bragg grating sensors and an elastic silicone layer. The fiber Bragg grating sensors are used to collect distributed tactile force and temperature signals, and the elastic silicone layer covers the fiber Bragg grating sensors to achieve stress transfer; a conductive layer, disposed beneath the fiber sensing layer and made of an array of flexible conductive material, for multimodal electrical signal collection and transmission; and an encapsulation layer. The dielectric layer, fiber sensing layer, and conductive layer collaborate to achieve a multimodal fusion of distributed proximity sensing, distributed force tactile sensing, and non-contact temperature sensing. This multimodal flexible electronic skin can be used to meet the needs of accurate acquisition and real-time feedback of multimodal information in complex environments.

Description

Technical Field

[0001] The present invention relates to flexible intelligent sensing technology, and in particular to a distributed multimodal flexible sensor based on Bragg fiber grating and a multimodal sensing method. Background Art

[0002] With the rapid development of artificial intelligence, flexible electronics, and intelligent sensing technologies, traditional rigid sensors are increasingly unable to meet the demands for high-sensitivity, high-resolution, and real-time sensing of multimodal information in complex environments. Emerging fields such as flexible robotics, biomimetic electronic skin, and human-computer interaction are placing higher demands on sensor flexibility, distributed deployment, and multimodal fusion perception. Flexible electronic skin, a key component that mimics the perceptual capabilities of human skin, is the foundation for achieving refined perception and dexterous control in flexible robots. Its performance directly determines the perception and interaction capabilities of the entire system.

[0003] Existing flexible skin technologies suffer from limited sensing dimensions, insufficient spatial resolution, difficulty in signal decoupling, and a lack of non-contact sensing capabilities. Currently, there are no flexible sensors with distributed proximity, force, tactile, and temperature sensing capabilities. Therefore, there is an urgent need to develop a multimodal flexible electronic skin with a distributed structure that simultaneously provides proximity, force, tactile, and temperature sensing capabilities. This skin should possess excellent flexible structural adaptability, high sensing accuracy, fast response, and strong anti-interference capabilities to meet the urgent needs of flexible robots for accurate acquisition of multimodal information and real-time feedback in complex environments.

[0004] It should be noted that the information disclosed in the above background technology section is only used to understand the background of this application, and therefore may include information that does not constitute prior art known to ordinary technicians in this field. Summary of the Invention

[0005] The main purpose of the present invention is to overcome the defects existing in the above-mentioned background technology and provide a distributed multimodal flexible sensor based on Bragg fiber grating and a multimodal sensing method.

[0006] To achieve the above object, the present invention adopts the following technical solutions:

[0007] A distributed multimodal flexible sensor based on fiber Bragg grating, comprising:

[0008] The dielectric layer is used to enhance the non-contact electric field response and detect the proximity of the target object;

[0009] an optical fiber sensing layer, disposed below the dielectric layer, comprising an S-shaped distributed fiber Bragg grating sensor and an elastic silicone layer, wherein the fiber Bragg grating sensor is used to collect distributed tactile force and temperature signals, and the elastic silicone layer covers the fiber Bragg grating sensor to achieve stress transmission;

[0010] A conductive layer, disposed below the optical fiber sensing layer and made of an array of flexible conductive materials, is used for multimodal electrical signal acquisition and transmission;

[0011] Encapsulation layer, used for flexible encapsulation protection of the overall structure;

[0012] The dielectric layer, optical fiber sensing layer and conductive layer cooperate to realize the multimodal fusion of distributed proximity sensing, distributed force tactile sensing and non-contact temperature sensing.

[0013] Furthermore, the fiber Bragg grating sensor adopts a single-mode optical fiber structure and is continuously arranged in an S-shape along the length direction of the sensor, thereby improving strain sensitivity and spatial resolution through a spatially distributed layout.

[0014] Furthermore, the elastic silicone layer covers the fiber Bragg grating sensor to provide flexible support and evenly transfer the stress generated by the object touching the fiber Bragg grating, thereby realizing distributed detection of the touch position and contact force.

[0015] Furthermore, the dielectric layer is a silicone elastomer with a microstructure on the surface, and non-contact object proximity detection is achieved by sensing electric field disturbances.

[0016] Furthermore, the conductive layer is made of a silver nanowire composite material and is designed as three independent conductive arrays for collecting strain, electric field and thermal signals.

[0017] Furthermore, the encapsulation layer is made of a flexible transparent polymer material so that the sensor can maintain stable signal sensing and transmission capabilities under bending or stretching deformation.

[0018] Furthermore, the size of a single conductive unit of the conductive layer is 25 mm×10 mm, and the total length is 80 mm, and the spatial signal collection efficiency is optimized through the array layout.

[0019] Furthermore, the path of the S-shaped arrangement follows a sine function , , and is equipped with 6 equally spaced Bragg grating sensing nodes with central wavelengths distributed between 1531.143nm and 1550.820nm.

[0020] Furthermore, the fiber Bragg grating sensor decouples temperature and strain signals by wavelength shifting:

[0021]

[0022] in, is the central wavelength of the reflected signal, is the strain optical coefficient, For strain, is the coefficient of thermal expansion, is the thermo-optical coefficient, is the change in temperature.

[0023] A multimodal sensing method using the sensor comprises the following steps:

[0024] S1, Proximity sensing stage: When an object approaches but does not touch the dielectric layer, the dielectric layer senses the electric field disturbance and outputs a proximity signal. At the same time, the wavelength offset of the fiber Bragg grating sensor outputs a temperature signal.

[0025] S2, contact sensing stage: When an object touches the sensor surface, the elastic silicone layer transmits stress to the fiber Bragg grating sensor, and the touch position and contact force are calculated through the wavelength offset;

[0026] S3, the conductive layer collects strain, electric field and thermal signals, and realizes multi-modal signal fusion through back-end processing;

[0027] S4, detachment recovery stage: When the object detaches from the sensor surface, the optical fiber wavelength offset gradually decays to the baseline value as the stress is released, realizing dynamic monitoring of the contact status;

[0028] The method achieves mode switching and signal decoupling through the following mechanisms: (a) synchronous activation of proximity signal and temperature signal output in the non-contact state; (b) dominant force tactile perception in the contact state; and (c) natural decoupling of proximity perception, force tactile perception, and temperature perception signals through physical mechanisms.

[0029] In some embodiments, the distributed multimodal flexible sensor based on Bragg fiber grating of the present invention includes a dielectric layer, a fiber optic sensing layer, a conductive layer and a packaging layer, wherein the fiber optic sensing layer is arranged between the dielectric layer and the conductive layer, and the packaging layer is the bottom layer, wherein: the fiber optic sensing layer includes an S-shaped distributed Bragg fiber grating sensor and an elastic silicone layer, and the fiber grating sensor is used for distributed tactile and temperature signals; the conductive layer is made of 3 array-type flexible conductive materials, which is used to realize electrical signal acquisition and processing; the dielectric layer is used to enhance the distributed non-contact electric field response to realize the detection of the proximity state of the target object; the multimodal flexible electronic skin can realize distributed proximity perception, distributed force tactile perception and non-contact temperature perception.

[0030] In some embodiments, the Bragg fiber grating sensor adopts a single-mode optical fiber structure and is arranged in an S-shape along the length direction of the electronic skin. The S-shaped structure is used to improve spatial resolution and strain sensitivity. The elastic silicone layer covers the fiber grating sensor to provide flexible support and stress transfer, so that when an object touches the skin surface, the stress can be effectively transferred to the fiber grating, thereby realizing the perception of the touch position and contact force. The dielectric layer is a microstructured surface silicone elastomer, which is used to sense electric field disturbances and realize non-contact object proximity detection. The conductive layer is made of a silver nanowire composite conductive material with excellent flexibility and conductivity, and is used to collect strain, electric field or thermal signals and transmit them to the signal processing module. The encapsulation layer is composed of a flexible transparent polymer material, which is used to protect and seal the structure to ensure that the flexible electronic skin still has stable signal perception and transmission capabilities under deformation states such as bending and stretching.

[0031] The present invention has the following beneficial effects:

[0032] The present invention provides a distributed multimodal flexible sensor based on a fiber Bragg grating (FBG), which features distributed proximity sensing, distributed force tactile sensing, and non-contact temperature sensing. The fiber sensing layer comprises an S-shaped distributed fiber Bragg grating (FBG) sensor for distributed tactile and temperature signal acquisition and an elastic silicone layer. The former is used for distributed tactile and temperature signal acquisition, while the latter provides flexible support and transmits stress. The dielectric layer is preferably a silicone elastomer with a microstructured surface, which enhances the non-contact electric field response to detect the proximity of an object. The conductive layer is made of an array of flexible conductive materials and is used for multimodal electrical signal acquisition and transmission. When an object approaches but does not contact the sensor, the dielectric layer senses the electric field perturbation to detect proximity, while the fiber Bragg grating (FBG) sensor achieves non-contact temperature sensing through wavelength offset. When the object contacts the sensor surface, the elastic silicone layer transmits stress to the fiber Bragg grating (FBG) sensor, and the wavelength offset can be used to determine the touch position and contact force. The conductive layer collects strain, electric field, and thermal signals and processes them through back-end processing to achieve multimodal signal fusion. When the object leaves, the fiber wavelength offset gradually returns to its baseline value as stress is released. Through the aforementioned structural design and dynamic interaction mechanism, the sensor achieves highly sensitive distributed detection of multimodal signals, significantly improving its sensing range and sensitivity. Its S-shaped arrangement of fiber Bragg grating sensors improves spatial resolution and strain sensitivity. The elastic silicone layer evenly disperses stress and enhances durability. The dielectric layer enables highly sensitive proximity detection, and the conductive layer ensures efficient acquisition and transmission of multimodal signals. This sensor boasts excellent flexible structural adaptability, high sensing accuracy, fast response, and strong anti-interference capabilities. It can serve as a multimodal flexible electronic skin capable of proximity, force, tactile, and temperature sensing. It is suitable for applications in intelligent robots, wearable devices, and human-computer interaction. It can meet the needs of accurate acquisition and real-time feedback of multimodal information in complex environments, while ensuring signal stability under deformations such as bending and stretching, and has broad application prospects.

[0033] Other beneficial effects of the embodiments of the present invention will be further described below. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 This is an exploded view of a multimodal flexible electronic skin constructed according to a preferred embodiment of the present invention;

[0035] Figure 2 is a dimensional diagram of the conductive layer constructed according to a preferred embodiment of the present invention;

[0036] Figure 3 Schematic diagram of the structure of the reverse mold of the elastic silicone layer constructed according to the preferred embodiment of the present invention;

[0037] Figure 4 Schematic diagram of the reverse mold structure of the encapsulation layer constructed according to the preferred embodiment of the present invention;

[0038] Figure 5 is a schematic diagram of the surface microstructure of a dielectric layer constructed according to a preferred embodiment of the present invention;

[0039] Figure 6 It is a layout and dimension diagram of a fiber Bragg grating sensor constructed according to a preferred embodiment of the present invention. DETAILED DESCRIPTION

[0040] The following is a detailed description of the embodiments of the present invention. It should be emphasized that the following description is only exemplary and is not intended to limit the scope of the present invention and its application.

[0041] It should be noted that when an element is referred to as being "fixed to" or "disposed on" another element, it can be directly on the other element or indirectly on the other element. When an element is referred to as being "connected to" another element, it can be directly connected to the other element or indirectly connected to the other element. In addition, connection can be used for both fixing and coupling or communication.

[0042] It should be understood that the terms "length", "width", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", etc., indicating the orientation or position relationship, are based on the orientation or position relationship shown in the accompanying drawings, and are only for the convenience of describing the embodiments of the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operate in a specific orientation, and therefore cannot be understood as limiting the present invention.

[0043] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be understood to indicate or imply relative importance or implicitly specify the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of such features. In the description of the embodiments of the present invention, "plurality" means two or more, unless otherwise specifically defined.

[0044] Existing flexible electronic skins are mostly based on a single sensing mode, making it difficult to simultaneously meet the multimodal sensing requirements for touch, temperature, and proximity. Furthermore, the limited sensor placement results in insufficient spatial resolution and signal stability, limiting their application performance in complex environments. To address these issues, the present invention proposes a distributed multimodal flexible sensor based on a fiber Bragg grating (FBG). This achieves a multimodal flexible electronic skin with a distributed structure and the capabilities of proximity, force, touch, and temperature sensing. This skin exhibits excellent flexible structural adaptability, high sensing accuracy, fast response, and strong anti-interference capabilities, effectively meeting the needs of flexible robots for accurate acquisition of multimodal information and real-time feedback in complex environments.

[0045] See Figure 1 An embodiment of the present invention provides a distributed multimodal flexible sensor based on Bragg fiber gratings, comprising a dielectric layer 1, a fiber optic sensing layer, a conductive layer 4, and a packaging layer 5. The dielectric layer 1 is used to enhance the non-contact electric field response and realize the detection of the proximity distance of the target object. The fiber optic sensing layer is arranged below the dielectric layer, and includes an S-shaped distributed Bragg fiber grating sensor 2 and an elastic silicone layer 3. The fiber optic grating sensor is used for distributed tactile force signal and temperature signal acquisition. The elastic silicone layer 3 covers the fiber optic grating sensor 2 to realize stress transfer. The conductive layer 4 is arranged below the fiber optic sensing layer, and is made of an array-type flexible conductive material for multimodal electrical signal acquisition and transmission. The packaging layer 5 can be composed of a flexible transparent polymer material for flexible packaging protection of the overall structure. Among them, the dielectric layer, the fiber optic sensing layer, and the conductive layer cooperate to realize the multimodal fusion of distributed proximity perception, distributed force tactile perception, and non-contact temperature perception.

[0046] In some embodiments, the elastic silicone layer 3 covers the fiber Bragg grating sensor 2 to provide flexible support and evenly transfer the stress generated by the object's touch to the fiber Bragg grating, thereby achieving distributed detection of the touch position and contact force.

[0047] See Figure 2 In some embodiments, the conductive layer 4 is made of a silver nanowire composite material and is designed as three independent conductive arrays for collecting strain, electric field, and thermal signals. In some embodiments, the individual conductive units of the conductive layer 4 are rectangular in size, and the array layout optimizes spatial signal collection efficiency.

[0048] See Figure 5 In some embodiments, the dielectric layer 1 is a silicone elastomer with a microstructure on the surface, which can detect the proximity distance of non-contact objects by sensing electric field disturbances.

[0049] In some embodiments, the encapsulation layer 5 is made of a flexible transparent polymer material to ensure that the sensor maintains stable signal sensing and transmission capabilities under bending or stretching deformation.

[0050] See Figure 6 In some embodiments, the fiber Bragg grating sensor 2 adopts a single-mode fiber structure and is continuously arranged in an S-shape along the length of the sensor, thereby improving strain sensitivity and spatial resolution through a spatially distributed layout. According to a preferred embodiment, the path of the S-shaped arrangement follows a sinusoidal function. , , and is equipped with 6 equally spaced Bragg grating sensing nodes with central wavelengths distributed between 1531.143nm and 1550.820nm.

[0051] In some embodiments, the fiber Bragg grating sensor 2 decouples temperature and strain signals by wavelength shifting:

[0052]

[0053] in, is the central wavelength of the reflected signal, is the strain optical coefficient, For strain, is the coefficient of thermal expansion, is the thermo-optical coefficient, is the change in temperature.

[0054] An embodiment of the present invention further provides a multimodal sensing method of the distributed multimodal flexible sensor, comprising the following steps:

[0055] Step S1: When an object approaches but does not touch, the dielectric layer 1 senses the electric field disturbance to achieve proximity detection, and the fiber Bragg grating sensor 2 senses the wavelength offset to achieve non-contact temperature sensing.

[0056] Step S2: When an object contacts the sensor surface, the elastic silicone layer 3 transmits stress to the fiber grating sensor 2, and the touch position and contact force are calculated based on the wavelength offset;

[0057] Step S3: The conductive layer 4 collects strain, electric field and thermal signals, and realizes multi-modal signal fusion through back-end processing;

[0058] Step S4: During the object detachment process, the optical fiber wavelength gradually returns to the baseline value as the stress is released, thereby realizing dynamic monitoring of the contact state;

[0059] Among them, proximity perception, force tactile perception and temperature perception signals are decoupled through physical mechanisms to support independent signal analysis.

[0060] More specifically, the method achieves multimodal signal switching and decoupling through the following dynamic interaction mechanism: (a) Proximity perception stage: When an object approaches but does not touch the dielectric layer 1, the dielectric layer senses the electric field disturbance and generates a proximity signal, while the fiber Bragg grating sensor 2 outputs a temperature signal through the wavelength offset; (b) Contact perception stage: When the object contacts the sensor surface, the elastic silicone layer 3 transfers stress to the fiber Bragg grating sensor 2, and the touch position and contact force are calculated through the wavelength offset; (c) Detachment recovery stage: When the object detaches from the sensor surface, the fiber wavelength offset gradually decays to the baseline value as the stress is released; wherein, the proximity perception, force tactile perception, and temperature perception signals are decoupled through a physical mechanism.

[0061] The distributed multimodal flexible sensor based on Bragg fiber grating of the present invention has the functions of distributed proximity sensing, distributed force tactile sensing, and non-contact temperature sensing through the above-mentioned design, and can be used as a multimodal flexible electronic skin. It includes four parts: a dielectric layer, a fiber optic sensing layer, a conductive layer, and a packaging layer. The fiber optic sensing layer includes an S-shaped distributed Bragg fiber grating sensor and an elastic silicone layer. When objects of different materials approach the flexible electronic skin, the flexible electronic skin can sense the proximity of the object in different areas; when the object touches the flexible electronic skin, the flexible electronic skin can sense the touch position and the magnitude of the contact force; when no object approaches or touches the object, the flexible electronic skin can sense the temperature of the environment. This multimodal flexible electronic skin has distributed proximity sensing, distributed force tactile sensing, and non-contact temperature sensing functions, and experiments with multiple flexible sensing fields to achieve reliable human-computer interaction.

[0062] The following further describes the specific embodiments of the present invention and its working principles and processes.

[0063] See Figure 1 A distributed multimodal flexible sensor based on Bragg fiber grating integrates a dielectric layer 1, an optical fiber sensing layer, a conductive layer 4 and an encapsulation layer 5. It can achieve highly sensitive distributed detection of multimodal signals and is suitable for application fields such as intelligent robots, wearable devices and human-computer interaction.

[0064] The sensor can be used as a distributed multimodal flexible electronic skin, which includes a dielectric layer 1, a fiber optic sensing layer, a conductive layer 4 and an encapsulation layer 5, wherein the fiber optic sensing layer is arranged between the dielectric layer 1 and the conductive layer, and the encapsulation layer 5 is the bottom layer. The fiber optic sensing layer includes a distributed Bragg fiber grating sensor 2 and an elastic silicone layer 3 arranged in an S-shape. The distributed Bragg fiber grating sensor 2 adopts a single-mode fiber Bragg grating sensor and is arranged in an S-shape along the length of the electronic skin. This arrangement improves the spatial resolution and strain sensitivity of the sensor, and cooperates with the coated elastic silicone layer to achieve accurate perception of touch position and contact force. The elastic silicone layer provides flexible support while ensuring efficient stress transmission, ensuring stable operation of the fiber optic sensor in a deformed state. The conductive layer 4 is made of three groups of arrayed flexible conductive materials, and silver nanowire composite conductive materials are selected. It has excellent flexibility and conductivity, can achieve efficient acquisition and transmission of strain, electric field and thermal signals, and cooperates with the back-end signal processing module to complete the fusion and analysis of multimodal information. The dielectric layer 1 is a silicone elastomer with a microstructured surface, designed as an electric field perturbation-sensitive layer. This layer enables contactless detection of approaching objects, enhancing the electronic skin's environmental awareness and secure interaction capabilities. The encapsulation layer 5, made of a flexible, transparent polymer material, offers excellent mechanical flexibility and environmental sealing, ensuring the stability and durability of the entire electronic skin structure and reliable sensing signals under various complex deformation conditions, such as bending and stretching.

[0065] Through the above-mentioned structural design, the present invention realizes the multimodal integration of distributed proximity sensing, distributed tactile force sensing and non-contact temperature sensing, significantly improving the sensing range and sensitivity of flexible electronic skin, and meeting the needs of intelligent robots and intelligent wearable devices for high-precision, multifunctional flexible sensing. The single-mode Bragg fiber grating sensors in the optical fiber sensing layer are laid in an S-shaped arrangement, which can effectively improve the sensing spatial resolution and enhance the response sensitivity to strain changes, which is conducive to accurately locating the touch point and the magnitude of the force. The elastic silicone layer not only serves as a flexible substrate for the sensor, but also can evenly disperse the stress applied to the skin surface, avoid stress concentration damage to the fiber grating sensor, and improve the durability of the system. The conductive layer material used in the present invention has excellent flexibility and electrical conductivity, can maintain stable electrical performance during multiple bending and stretching deformations, ensure high-quality transmission of electrical signals, and further improve the overall performance and service life of the system.

[0066] like Figure 1As shown, in one specific embodiment, a fiber optic sensing layer is disposed between a dielectric layer 1 and a conductive layer 4. The fiber optic sensing layer includes an S-shaped distributed fiber Bragg grating sensor 2 and an elastic silicone layer 3. The fiber grating sensor 2 is used for distributed tactile and temperature signals, and the dielectric layer 1 is used to enhance the distributed non-contact electric field response to detect the proximity of the target object. The encapsulation layer 5 is the bottom layer.

[0067] like Figure 2 As shown, the conductive layer is made of three arrays of flexible conductive materials, which are used to realize the acquisition and processing of three proximity array electrical signals. The overall size of the conductive layer is 80mm long and 10mm wide, and a single conductive layer unit is 25mm.

[0068] like Figure 3 The figure shows a schematic diagram of the reverse mold structure for the elastic silicone layer 3. First, a 3D printer is used to print the reverse mold for the elastic silicone layer using polylactic acid (PLA). Prepared Ecoflex 00-30 elastic material is then poured into the mold. After vacuuming, the mold is placed in a 60°C incubator for one hour to cure. The mold is then removed, resulting in the elastic silicone layer 3. The S-shaped distributed fiber Bragg grating sensor 2 is then placed into the grooves of the elastic silicone layer 3 and secured. The fabricated Ecoflex 00-30 elastic material is then used for bonding. The material is then cured in a natural environment to form the optical fiber sensing layer.

[0069] Figure 4 The figure shows the reverse mold structure for the encapsulation layer 5. First, a 3D printer is used to print the reverse mold for the elastic silicone layer using polylactic acid (PLA). The prepared Ecoflex 00-30 elastic material is then poured into the mold. After vacuuming, the mold is placed in a 60°C incubator for one hour to cure. The mold is then removed to obtain the encapsulation layer 5.

[0070] Figure 5 The figure shows the surface microstructure of dielectric layer 1. A mold is first printed using polylactic acid (PLA) material using a 3D printer. 320-grit sandpaper is then placed at the bottom of the mold to secure it. Prepared Ecoflex 00-30 elastomer is then poured into the mold. After vacuuming, the mold is placed in a 60°C incubator for one hour to cure. The mold is then removed, resulting in dielectric layer 1 with a surface microstructure.

[0071] Figure 6 It is the layout dimension diagram of the fiber Bragg grating sensor 2. The layout of the fiber Bragg grating sensor 2 is a sine function. , The fiber Bragg grating sensor 2 generally comprises six equally spaced fiber Bragg grating sensor nodes FBG_1 through FBG_6, with central wavelengths of 1531.143 nm, 1535.242 nm, 1539.085 nm, 1543.029 nm, 1547.061 nm, 1550.820 nm, and 1539.081 nm, respectively. In this embodiment, a dual-fiber compensation system is employed, with the central wavelength of the compensating fiber Bragg grating being 1539.081 nm.

[0072] In this embodiment, the relationship between the wavelength shift of each fiber Bragg grating (FBG) and the strain and temperature changes can be described as follows:

[0073]

[0074] in, is the central wavelength of the reflected signal, is the strain optical coefficient, For strain, is the coefficient of thermal expansion, is the thermo-optical coefficient, is the change in temperature.

[0075] In this embodiment, for a specific fiber type, the strain optical coefficient is a constant value, which can be obtained by the following formula:

[0076]

[0077] in, and represents the Pockel coefficient of the strain tensor, is Poisson's ratio, is the effective refractive index of the optical fiber.

[0078] In this embodiment, if there is no contact to generate stress changes, the flexible electronic skin can perform distributed perception of temperature changes.

[0079] The sensing mechanism of the distributed multimodal flexible electronic skin provided by an embodiment of the present invention is as follows: (i) In the initial stage, due to the difference in electron affinity between the materials, when the external object is in full contact with the flexible dielectric layer, uniformly distributed positive and negative charges are generated on the interface of the dielectric layer 1; (ii) When the external object approaches the flexible dielectric layer 1 but has not yet made physical contact, free electrons flow from the ground end to the flexible electrode, and the optical fiber is not strained, so there is no wavelength shift; (iii) After the external object comes into contact with the flexible electronic skin, electron transfer is enhanced, and the embedded optical fiber undergoes mechanical deformation, resulting in a measurable wavelength shift; (iv) When full contact is established, charge neutralization occurs, the electron flow stops, and the wavelength shift of the optical fiber reaches a maximum value; (v) In the release stage, as the external pressure is released, free electrons flow back from the flexible electrode to the ground wire, the optical fiber wavelength shift gradually decreases, and the sensing channel gradually returns to its initial state; (vi) When the external object is completely separated from the flexible electronic skin, the electron backflow increases, and the optical fiber wavelength returns to the baseline value. This dynamic interaction mechanism enables the flexible electronic skin to operate in a bimodal manner: when an external object is close but not touching, it functions as a proximity / temperature sensor; when contact occurs, it switches to a tactile sensor. Notably, the multimodal sensing signals are naturally decoupled, enabling smooth and independent signal interpretation.

[0080] In summary, the present invention provides a distributed multimodal flexible sensor and a multimodal sensing method based on fiber Bragg gratings. Compared with the prior art, the above technical solution conceived by the present invention has the following technical advantages:

[0081] This sensor can be used as a perceptual flexible electronic skin with distributed multimodal sensing. The flexible electronic skin features distributed proximity sensing, distributed force tactile sensing, and non-contact temperature sensing. The dielectric layer of the flexible electronic skin, made of a microstructured surface silicone elastomer, enhances non-contact electric field response, enabling highly sensitive proximity detection of target objects. The distributed tactile fiber sensing layer utilizes S-shaped single-mode fiber Bragg grating sensors, significantly improving spatial resolution and strain sensitivity, enabling distributed, high-precision capture of tiny tactile signals. The elastic silicone layer provides flexible support and stress transfer for the fiber sensors, ensuring accurate and stable tactile signal transmission. The distributed conductive layer is made of multiple arrays of flexible conductive materials. Using high-performance conductive materials, the multi-array flexible conductive layers enable efficient acquisition and transmission of multimodal signals, improving the overall response speed and accuracy of the system. This distributed multimodal flexible electronic skin structure not only achieves distributed detection of multimodal signals but also ensures the stability of the sensor system in complex deformation environments, proving promising applications.

[0082] The above description further details the present invention in conjunction with specific / preferred embodiments, and the specific implementation of the present invention should not be construed as being limited to these descriptions. Persons skilled in the art will appreciate that, without departing from the spirit of the present invention, they may make various substitutions or modifications to the described embodiments, and these substitutions or modifications should be considered to fall within the scope of protection of the present invention. Throughout this specification, reference to terms such as "one embodiment," "some embodiments," "preferred embodiments," "examples," "specific examples," or "some examples" indicates that the specific features, structures, materials, or characteristics described in conjunction with such embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of these terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples. Persons skilled in the art may combine and assemble the different embodiments or examples described in this specification, as well as features of different embodiments or examples, without conflicting opinions. Although the embodiments of the present invention and their advantages have been described in detail, it should be understood that various changes, substitutions, and modifications may be made herein without departing from the scope of protection of the patent application.

Claims

1. A distributed multimodal flexible sensor based on fiber Bragg grating, characterized in that: include: The dielectric layer is used to enhance the non-contact electric field response and detect the proximity of the target object; an optical fiber sensing layer, disposed below the dielectric layer, comprising an S-shaped distributed fiber Bragg grating sensor and an elastic silicone layer, wherein the fiber Bragg grating sensor is used to collect distributed tactile force and temperature signals, and the elastic silicone layer covers the fiber Bragg grating sensor to achieve stress transmission; A conductive layer, disposed below the optical fiber sensing layer and made of an array of flexible conductive materials, is used for multimodal electrical signal acquisition and transmission; Encapsulation layer, used for flexible encapsulation protection of the overall structure; The dielectric layer, the optical fiber sensing layer and the conductive layer cooperate to realize multimodal fusion of distributed proximity sensing, distributed force tactile sensing and non-contact temperature sensing; The dielectric layer is a silicone elastomer with a microstructure on the surface, which can detect the proximity of objects without contact by sensing electric field disturbances. The fiber Bragg grating sensor decouples temperature and strain signals through wavelength shift: ； in, is the central wavelength of the reflected signal, is the strain optical coefficient, For strain, is the coefficient of thermal expansion, is the thermo-optical coefficient, is the change in temperature.

2. The sensor according to claim 1, characterized in that The fiber Bragg grating sensor adopts a single-mode optical fiber structure and is continuously arranged in an S-shape along the length of the sensor, thereby improving strain sensitivity and spatial resolution through a spatially distributed layout.

3. The sensor according to claim 1, wherein The elastic silicone layer covers the fiber Bragg grating sensor, and is used to provide flexible support and evenly transfer the stress generated by the object touching the fiber Bragg grating, thereby realizing distributed detection of the touch position and contact force.

4. The sensor according to any one of claims 1 to 3, characterized in that The conductive layer is made of a silver nanowire composite material and is designed as three independent conductive arrays for collecting strain, electric field and thermal signals.

5. The sensor according to claim 4, characterized in that The individual conductive units of the conductive layer are rectangular, and the spatial signal collection efficiency is optimized through an array layout.

6. The sensor according to any one of claims 1 to 3, characterized in that The packaging layer is made of a flexible transparent polymer material so that the sensor can maintain stable signal perception and transmission capabilities under bending or stretching deformation.

7. The sensor according to any one of claims 1 to 3, characterized in that The S-shaped arrangement path follows the sine function y=8sin(0.1(x+14)), x∈[−22.5mm,57.5mm], and is provided with 6 equally spaced Bragg grating sensing nodes with central wavelengths distributed between 1531.143nm and 1550.820nm.

8. A multimodal sensing method using the sensor according to any one of claims 1 to 7, characterized in that: The following steps are involved: S1, Proximity sensing stage: When an object approaches but does not touch the dielectric layer, the dielectric layer senses the electric field disturbance and outputs a proximity signal. At the same time, the wavelength offset of the fiber Bragg grating sensor outputs a temperature signal. S2, contact sensing stage: When an object touches the sensor surface, the elastic silicone layer transmits stress to the fiber Bragg grating sensor, and the touch position and contact force are calculated through the wavelength offset; S3, the conductive layer collects strain, electric field and thermal signals, and realizes multi-modal signal fusion through back-end processing; S4, detachment recovery stage: When the object detaches from the sensor surface, the optical fiber wavelength offset gradually decays to the baseline value as the stress is released, realizing dynamic monitoring of the contact status; The method achieves mode switching and signal decoupling through the following mechanisms: (a) synchronous activation of proximity signal and temperature signal output in the non-contact state; (b) dominant force tactile perception in the contact state; and (c) natural decoupling of proximity perception, force tactile perception, and temperature perception signals through physical mechanisms.

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