Passive dual-mode haptic sensor and method of manufacturing the same

Abstract

The application discloses a passive dual-mode tactile sensor and a preparation method thereof, and belongs to the technical field of optical sensing and flexible tactile sensing. The sensor comprises a flexible support substrate, an elastic composite film containing long-afterglow light-emitting particles, micro-nano optical fibers embedded or attached to the surface of the elastic composite film, a flexible packaging layer, and an optical signal detection unit. When an external target approaches, the target surface reflects the scattered light, changes the output light intensity of the micro-nano optical fiber, and realizes non-contact sensing. When the external target contacts or presses, the composite film produces stress-induced luminescence enhancement and interface coupling change under the action of stress, and realizes contact force tactile sensing. The preparation method comprises light-emitting composite layer forming, micro-nano optical fiber taper preparation, interface coupling integration and packaging curing. The application has the advantages of no need for continuous light supply, compact structure, anti-electromagnetic interference, easy flexible integration, and suitability for human-computer interaction application.

Description

Technical Field

[0001] This invention belongs to the field of optical sensing and flexible tactile sensing technology, specifically relating to a passive dual-modal tactile sensor and its fabrication method. Background Technology

[0002] With the rapid development of intelligent robots, flexible electronic skin, virtual reality / augmented reality, human-computer collaboration systems, and intelligent interactive terminals, flexible tactile sensors capable of continuously sensing external stimuli, simulating human skin, have attracted widespread attention. In practical applications, an ideal tactile sensor not only needs to identify pressure, contact state, or operational behavior after contact with a target, but also needs to sense the approach process before contact, thereby improving the safety, continuity, and naturalness of the interaction process. Therefore, dual-modal tactile sensors that combine non-contact proximity sensing and contact force sensing capabilities are gradually becoming an important research direction in this field.

[0003] Most existing flexible tactile sensors rely on electrical signals for detection, with common technologies including resistive, capacitive, piezoelectric, triboelectric, ion-electronic, and magnetoelectric sensors. While these sensors can achieve functions such as pressure detection, slip recognition, vibration sensing, and proximity detection to some extent, they typically suffer from the following drawbacks: First, they rely on complex circuits and continuous power supply, resulting in high system integration complexity. Second, electrical signals are susceptible to interference from the external electromagnetic environment, affecting signal stability. Third, achieving dual-modal sensing (non-contact and contact) often requires multiple independent sensing units or multi-channel collaborative processing, leading to complex structures, severe signal coupling, and hindering flexible and miniaturized integration.

[0004] In contrast, optical signal-based tactile sensors offer advantages such as strong resistance to electromagnetic interference, high signal stability, convenient long-distance transmission, and suitability for flexible packaging, and have gradually become an important development direction for flexible tactile sensing in recent years. In particular, micro- and nano-fibers, due to their subwavelength-scale lateral dimensions, strong evanescent field distribution, and high sensitivity to local optical field disturbances, can effectively sense changes in the optical field near the interface, thus showing great application potential in flexible optical sensing, weak disturbance detection, and human-computer interaction interfaces.

[0005] However, existing flexible optical tactile sensors based on micro / nano fibers typically rely on lasers, LEDs, or other external continuous light sources to provide input light signals. Their system architecture often requires additional light-supply modules, coupling modules, and stabilizing optical paths, resulting in high overall system power consumption and complex structure, which is detrimental to passive, low-power, and wearable applications. Furthermore, most existing optical tactile sensors primarily detect single contact modes, lacking a unified sensing mechanism for the continuous interaction process of target approach and contact, making it difficult to simultaneously achieve the coordinated acquisition of non-contact and contact dual-modal tactile information within a single device structure.

[0006] On the other hand, long-afterglow luminescent materials can continue to emit light after a short period of external photoexcitation and produce an enhanced luminescence response under mechanical stress, possessing both continuous afterglow luminescence and mechanoluminescence response characteristics. These materials can serve as internal passive photon sources, reducing dependence on continuous external light supply; furthermore, they can generate stress-related additional optical signals under contact or pressure conditions, providing a new approach to constructing passive optical sensors with both non-contact and contact sensing capabilities.

[0007] However, the existing technology lacks a flexible passive dual-modal tactile sensor that can effectively combine a long-afterglow luminescent composite layer with a micro / nano fiber near-field coupling structure, and utilize the reflection back-coupling light modulation mechanism when the target approaches and the mechanoluminescence enhancement mechanism when the target contacts, to simultaneously realize non-contact proximity sensing and contact force sensing in a single optical output channel.

[0008] Therefore, there is an urgent need to provide a passive dual-modal tactile sensor with a simple structure, no need for continuous external light supply, good flexibility and stability, and its fabrication method, in order to overcome the above-mentioned shortcomings of the existing technology. Summary of the Invention

[0009] This invention provides a passive dual-modal tactile sensor based on near-field coupling of long-persistent materials and micro / nano optical fibers, and its fabrication method, for achieving coordinated detection of non-contact proximity sensing and contact force sensing. By constructing a heterogeneous integrated structure consisting of a long-persistent luminescent composite layer, a micro / nano optical fiber signal transduction layer, and a flexible encapsulation layer, this invention utilizes the continuous luminescence and force-induced luminescence characteristics of long-persistent materials to achieve stable output and distinguishable recognition of dual-modal tactile information in a single optical channel without the need for a continuous external light source and complex electrical acquisition units. This provides a low-power, highly integrated optical tactile sensing solution for intelligent robotic arms, flexible electronic skin, human-computer interfaces, and secure collaborative systems.

[0010] The technical solution provided by this invention is: a passive dual-modal tactile sensor comprising: a long afterglow luminescence composite layer, a micro-nano fiber optic signal transduction layer, a flexible encapsulation layer, and an optical signal output and detection unit;

[0011] The long-afterglow luminescent composite layer is used to continuously release afterglow light after pre-excitation and generate mechanoluminescence signal under stress; the thickness of the long-afterglow luminescent composite layer is 0.2 mm.

[0012] The micro / nano fiber optical signal transduction layer is disposed on the surface of the long-persistent light-emitting composite layer and forms a near-field coupling interface with the long-persistent light-emitting composite layer. It is used to capture and transduce the local light field generated by the long-persistent light-emitting composite layer into an output optical signal that propagates along the optical fiber.

[0013] The flexible encapsulation layer covers the outside of the long afterglow luminescent composite layer and the micro-nano fiber optical signal transduction layer, and is used to fix the near-field coupling interface and provide flexible mechanical protection.

[0014] The optical signal output and detection unit is connected to the micro / nano fiber optical signal transduction layer and is used to collect the output optical signal; the optical signal output and detection unit includes one or more of a photomultiplier tube (PMT) and a photon counter.

[0015] The passive dual-modal tactile sensor, in a non-contact state, alters the local light field distribution at the near-field coupling interface through the reflection and rescattering of stray light by the target object, thereby generating a non-contact proximity response signal; in a contact state, the output light signal is modulated by the mechanoluminescence signal generated by the long-afterglow luminescent composite layer, thereby generating a contact force response signal.

[0016] The non-contact proximity response signal and the contact force response signal are output and identified through the same micro-nano fiber optical signal transduction layer and the same optical signal output and detection unit.

[0017] The basic afterglow photon flux of the aforementioned long-afterglow luminescent composite layer decays over time after pre-excitation, and its basic optical signal can be expressed as:

[0018] (Equation 1);

[0019] in, For a moment and wavelength The long afterglow photon flux, This represents the initial photon flux. These represent the lifetime constants corresponding to different trap energy levels. These are the corresponding weighting coefficients;

[0020] The effective output fundamental optical signal formed by the long-afterglow luminescent composite layer at the near-field coupling interface of micro / nano optical fiber can be expressed as:

[0021] (Equation 2);

[0022] in, The basic output optical signal is generated by the long-afterglow luminescent composite layer and captured by micro / nano optical fibers. The coupling coefficient is determined by the micro / nano fiber structure parameters, burial depth, and interface coupling efficiency.

[0023] In a non-contact state, when the target object is located at a distance above the sensor surface... At this point, the additional optical signal increment caused by the reflection and rescattering of stray photons by the target object can be expressed as:

[0024] (Equation 3);

[0025] in, This is an additional output optical signal in contactless mode. The modulation coefficient of the reflected light. Distance to target Related return optical coupling enhancement functions;

[0026] Therefore, the total output optical signal in non-contact mode can be expressed as:

[0027] (Equation 4);

[0028] In the contact state, when the target object comes into contact with the sensor surface and mechanical stress is applied... At that time, the trapped charge carriers inside the long-afterglow luminescent composite layer are released under localized stress, generating an additional mechanoluminescence signal. This additional output can be expressed as:

[0029] (Equation 5);

[0030] in, For additional output optical signals in contact mode, The mechanoluminescence response coefficient, To be in relation to mechanical stress The relevant response function, For the time modulation function related to the afterglow working interval;

[0031] Therefore, the total output optical signal in contact mode can be expressed as:

[0032] (Formula 6);

[0033] The passive dual-modal tactile sensor's unified output optical signal during the proximity-contact continuous interaction process can be expressed as:

[0034] (Equation 7);

[0035] Therefore, the target distance With mechanical stress The output light signal is modulated by a reflected light modulation mechanism and a mechanoluminescence modulation mechanism, respectively, so that the present invention has non-contact proximity sensing and contact force sensing capabilities in the same device and a single optical channel.

[0036] The aforementioned micro / nano fiber optical signal transduction layer consists of an input cone region, a waist region, and an output cone region, wherein the waist region is the main optical signal capture and coupling region; the micro / nano fiber waist region is disposed on the surface of the long afterglow luminescence composite layer; the diameter of the micro / nano fiber waist region is 11 μm, the waist region length is 5 mm, and the cone region length is 30 mm.

[0037] The aforementioned flexible encapsulation layer is a transparent elastic polymer layer, used to maintain the relative positional stability between the micro / nano fiber optical signal transduction layer and the long afterglow luminescent composite layer under external force loading, bending, or repeated use conditions.

[0038] The aforementioned passive dual-modal tactile sensor also includes a signal processing and control module connected to the optical signal output and detection unit. The signal processing and control module is used to amplify, filter, perform baseline correction, analog-to-digital conversion, feature extraction, motion state discrimination, and control command generation on the output signal.

[0039] The above-mentioned action state discrimination includes the identification of at least four types of actions: non-contact slow sweep, non-contact fast sweep, non-contact approach and stay, and contact press release.

[0040] The aforementioned control commands generate control signals that map the identified motion states to the opening, swinging, gripping, holding, releasing, or standby control signals of the robotic arm.

[0041] The above-mentioned method for preparing a passive dual-modal tactile sensor includes the following steps: (1) mixing long-afterglow luminescent particles with an elastic polymer matrix to prepare a luminescent composite precursor liquid; (2) injecting the luminescent composite precursor liquid into a mold and curing it to form a long-afterglow luminescent composite layer; (3) preparing a micro-nano fiber by tapering a standard optical fiber; (4) placing the micro-nano fiber on the surface of the long-afterglow luminescent composite layer to form a near-field coupling interface; (5) flexibly encapsulating the long-afterglow luminescent composite layer and the micro-nano fiber to obtain the passive dual-modal tactile sensor.

[0042] The above-mentioned passive dual-modal tactile sensors are used in intelligent robotic arms, flexible electronic skin, human-computer interaction interfaces, or safe collaborative systems.

[0043] The human-computer interaction control system using the aforementioned tactile sensor includes the tactile sensor and a robotic arm execution unit; wherein, the signal processing and control module in the tactile sensor is used to convert the raw optical signal output by the tactile sensor into motion recognition results, and further output corresponding robotic arm control commands.

[0044] In this application, during use, in a non-contact state, the sensor is first pre-excited with 365nm ultraviolet light, causing the long-afterglow luminescent composite layer to enter an afterglow luminescence state. After pre-excitation, the long-afterglow luminescent composite layer continuously releases afterglow photons, forming a localized light field that can be captured in the neighborhood of the micro / nano fiber. When an external target object approaches the sensor surface but does not make contact, the target surface reflects and rescatters the emitted photons, causing some photons to return to the neighborhood of the micro / nano fiber, thereby increasing the intensity of the output light signal and achieving non-contact recognition of approach behavior. This improves the capture efficiency of the localized light field by the micro / nano fiber, outputting a non-contact proximity response signal for sensing the approach behavior of a target object.

[0045] In this application, when a target object contacts the sensor surface and mechanical stress is applied, the trapped charge carriers inside the long-afterglow luminescent composite layer are released under localized stress and undergo radiative recombination at the luminescence center, generating an additional mechanoluminescent signal. This signal is output via micro / nano fiber coupling, forming a contact force response signal for detecting the contact and force state. The output signal enhancement amplitude in contact mode is greater than in non-contact mode, and it exhibits significant transient enhancement characteristics, which can be used to detect and identify actions such as contact, pressing, and release.

[0046] The beneficial effects of this invention are as follows: 1. This invention utilizes the continuous luminescence characteristics of long-afterglow materials after pre-excitation as a passive photon source, enabling sensing output without the need for a continuous external light source, thus reducing system energy consumption and simplifying the optical path structure; 2. This invention can simultaneously achieve non-contact proximity sensing and contact force sensing through a single device structure, eliminating the need for multiple independent sensing units to work together, resulting in high system integration; 3. In this invention, the non-contact signal and the contact signal originate from two different mechanisms: reflected light modulation and mechanoluminescence modulation, respectively, which facilitates the differentiation and identification of the two types of signals in a single optical channel; 4. This invention employs an optical readout method, which has relatively high efficiency and reliability. 5. Strong anti-electromagnetic interference capability, making it more suitable for human-computer interaction and flexible tactile sensing applications in complex environments; 6. This invention adopts flexible polymer packaging and heterogeneous integration structure, and the device can still maintain good response stability under bending, loading and cyclic use conditions; 7. This invention can be widely used in intelligent robotic arms, flexible electronic skin, human-computer interaction interfaces, proximity warning systems and safe collaborative robots, etc., and has good application prospects; 8. This sensor can work stably for more than 20 hours without the continuous action of an external light source, achieve non-contact sensing at a distance of about 1.5cm, a response bandwidth of about 2kHz, and maintain a stable response in 500 cycles. Attached Figure Description

[0047] Appendix Figure 1 This is a schematic diagram of the overall structure of the passive dual-modal tactile sensor of the present invention;

[0048] Appendix Figure 2 This is the present invention. Scanning electron microscope image of a long afterglow material particle sample;

[0049] Appendix Figure 3 This is the present invention. Scanning electron microscope image of a long afterglow material / PDMS composite thin film sample;

[0050] Appendix Figure 4 This is the present invention. Elemental energy spectrum mapping of long afterglow material / PDMS composite thin film sample;

[0051] Appendix Figure 5 This is the present invention. XPS analysis images of long afterglow material / PDMS composite thin film samples;

[0052] Appendix Figure 6 This is the present invention. XRD patterns of thin film samples prepared by PDMS with long afterglow material;

[0053] Appendix Figure 7 This is a schematic diagram of the energy storage, afterglow luminescence, and mechanoluminescence mechanism of the long afterglow material of this invention;

[0054] Appendix Figure 8 This is a schematic diagram of the near-field coupling between the micro / nano optical fiber and the long afterglow luminescent composite layer of the present invention;

[0055] Appendix Figure 9 This is a simulation diagram of the light field enhancement of reflected light in the non-contact proximity sensing mode of the present invention;

[0056] Appendix Figure 10 This is a schematic diagram of the fabrication process of the passive dual-modal tactile sensor of the present invention;

[0057] Appendix Figure 11 This is a diagram of the test platform for the passive dual-modal tactile sensor of the present invention;

[0058] Appendix Figure 12 This is a schematic diagram illustrating the output response characteristics of the present invention in non-contact and contact modes. (Attached) Figure 12 (a): Output waveform diagram of non-contact slow lateral sweep; Appendix Figure 12 (b): Output waveform diagram of non-contact rapid lateral sweep; Appendix Figure 12 (c): Output waveform diagram where the normal direction approaches and remains stationary; Appendix Figure 12 (d): Output waveform diagram of the contact-press-release process.

[0059] Appendix Figure 13 This is a schematic diagram of the stability test results of the present invention under cyclic loading conditions;

[0060] Appendix Figure 14 This is a diagram of a human-computer interaction platform device integrating a passive dual-modal tactile sensor and a robotic arm, as described in this invention.

[0061] Appendix Figure 15 This is a flowchart illustrating how the original optical output signal is processed and mapped into robotic arm control commands in this invention.

[0062] Appendix Figure 16 This is a schematic diagram of the timing response characteristics of the present invention under different human-computer interaction actions. Detailed Implementation

[0063] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments, but the scope of protection of the present invention is not limited to the following embodiments. All equivalent substitutions, improvements and modifications made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

[0064] Example 1: The overall structure and composition of the passive dual-modal tactile sensor are shown in the attached figure. Figure 1 As shown:

[0065] (1) This embodiment provides a passive dual-mode tactile sensor based on near-field coupling of long-persistent material and micro / nano fiber, including a long-persistent light-emitting composite layer, a micro / nano fiber optical signal transduction layer, a flexible encapsulation layer, and an optical signal output and detection unit.

[0066] The long-afterglow luminescent composite layer serves as the core luminescent functional layer, continuously releasing afterglow light after pre-excitation and generating additional mechanoluminescence signals under mechanical stress. The micro / nano fiber optical signal transduction layer is disposed on the surface of the long-afterglow luminescent composite layer, capturing and transducing the local light field formed near the interface of the luminescent layer into an output optical signal propagating along the optical fiber. The flexible encapsulation layer is disposed on the outside of the device, fixing the relative positions between the functional layers and providing mechanical protection. The optical signal output and detection unit is connected to the micro / nano fiber, used for acquiring, recording, and analyzing the output optical signal.

[0067] In this embodiment, the sensor adopts a flexible heterogeneous integrated structure. A stable near-field coupling interface is formed between the long afterglow luminescent composite layer and the micro-nano fiber optical signal transduction layer, enabling the device to achieve coordinated detection of non-contact proximity sensing and contact force sensing without the need for continuous external light source.

[0068] (2) The material composition and structural characterization of the long afterglow luminescent composite layer are shown in the attached figure. Figure 2 As shown, the method used The long-afterglow luminescent particles exhibit irregular blocky and sheet-like micromorphological features, with obvious particle boundaries and rough surface characteristics, which is conducive to the formation of multiple scattering interfaces in the composite system.

[0069] After mixing and curing the long-afterglow luminescent particles with an elastic polymer matrix PDMS, a flexible long-afterglow luminescent composite film can be formed. The composite film has a relatively uniform particle distribution, as shown in the attached image. Figure 3 As shown, the luminescent particles are embedded in the polymer matrix, which retains the luminescent function of the long-afterglow material while also possessing the mechanical compliance of the flexible matrix.

[0070] The elemental energy spectrum mapping results of the long-afterglow luminescent composite thin film sample are attached. Figure 4 As shown, the results indicate that elements such as Eu, Dy, Al, and O are uniformly distributed in the composite layer, suggesting that the long-afterglow luminescent particles have good dispersion in the PDMS matrix, which is beneficial to the overall luminescence uniformity and mechanical response consistency of the device.

[0071] XPS analysis results of the long-afterglow luminescent composite thin film sample are attached. Figure 5 As shown, this indicates that the sample contains and The presence of characteristic valence states indicates the effective existence of luminescent and trap centers, thus ensuring the material's ability to produce continuous afterglow luminescence and stress-triggered luminescence.

[0072] XRD patterns of long-afterglow luminescent composite thin film samples and Corresponding characteristic peaks of the crystal phase, as shown in the attached figure. Figure 6 As shown, the composite and encapsulation process did not damage the crystal structure of the long afterglow material, thus ensuring its stable luminescence performance.

[0073] (3) Working mechanism of long afterglow luminescent composite layer and near-field coupling:

[0074] As attached Figure 7 As shown, the Long-afterglow materials can store energy after short-term photoexcitation and achieve continuous afterglow luminescence through the stepwise release of trapped charge carriers. Under the action of external mechanical stress, the local stress field can reduce the trap release barrier, causing the trapped charge carriers to be released rapidly and undergo radiative recombination at the luminescence center, thereby triggering an additional mechanoluminescence process.

[0075] In the basic afterglow stage following pre-excitation, the basic photon flux of the long afterglow luminescent composite layer can be expressed as: (Equation 1);

[0076] in, For a moment and wavelength The long afterglow photon flux, This represents the initial photon flux. These represent the lifetime constants corresponding to different trap energy levels. These are the corresponding weighting coefficients.

[0077] As attached Figure 8 As shown, when the long afterglow luminescent composite layer and the micro / nano optical fiber form a heterogeneous integrated structure, the afterglow photons generated by the spontaneous emission of the material will undergo multiple scattering and near-field interaction near the interface, and be captured by the spatial and momentum selective portion of the local optical field by the micro / nano optical fiber, thereby being transduced into an effective output signal propagating along the optical fiber.

[0078] At this near-field coupling interface, the basic output optical signal can be expressed as:

[0079] (Equation 2);

[0080] in, The basic output optical signal is captured by micro / nano optical fibers. The coupling coefficient is determined by the size of the micro / nano fiber, the embedment depth, and the interface coupling efficiency.

[0081] As attached Figure 9As shown, in the non-contact proximity sensing mode, when an external target object is located above the sensor surface, the target surface reflects and rescatters the long-afterglow scattering photons, causing some photons to return to the micro-nano fiber neighborhood, thereby changing the local light field distribution and enhancing the photon capture probability.

[0082] In this mode, the target distance is determined by... The resulting increase in the output optical signal can be expressed as:

[0083] (Equation 3);

[0084] in, This is an additional output optical signal in contactless mode. The modulation coefficient of the reflected light. Distance to target Related return optical coupling enhancement functions.

[0085] Therefore, the total output optical signal in non-contact mode can be expressed as:

[0086] (Equation 4);

[0087] Therefore, it can be seen that the essence of the non-contact proximity response in this invention lies in the process of light field redistribution and return light enhancement caused by the target object.

[0088] Example 2: Sensor fabrication method and testing platform:

[0089] This embodiment provides a method for fabricating the above-mentioned passive dual-modal tactile sensor, as shown in the attached figure. Figure 10 As shown, it includes the following steps:

[0090] Step S1, will Long-afterglow luminescent particles are mixed with PDMS prepolymer and curing agent at a mass ratio of 1:2 to form a luminescent mixture. The luminescent mixture is injected into a mold and cured by heating to form a flexible long-afterglow luminescent composite layer.

[0091] Step S2: Standard multimode fiber is fabricated into micro / nano fiber through a heating tapering process, forming an input tapered region, a waist region, and an output tapered region; preferably, the waist region of the micro / nano fiber has a diameter of about 11 μm, a waist region length of about 30 mm, and a tapered region length of about 5 mm.

[0092] Step S3: Position the micro-nano fiber on the surface of the long afterglow luminescent composite layer, so that the waist region of the micro-nano fiber and the luminescent composite layer form a stable near-field coupling interface.

[0093] Step S4: A transparent flexible encapsulation layer is covered on the outside of the micro / nano optical fiber and long afterglow luminescence composite layer, and then thermosetting is performed to obtain the passive dual-modal tactile sensor. Through the thermosetting process, the film is in a gel state before thermosetting. After embedding the optical fiber into the film, heating the sensing unit causes the gel-state prepolymer to solidify, thus fixing the micro / nano optical fiber in place.

[0094] As attached Figure 11 As shown, a test platform can be constructed to perform performance testing on this invention, including a pre-excitation light source, a displacement control unit, a loading unit, an optical signal output and detection unit, and a data acquisition system. The pre-excitation light source is used to pre-excite the long-afterglow luminescent composite layer; the displacement control unit is used to adjust the distance between the target object and the sensor; the loading unit is used to apply contact and pressure; and the optical signal output and detection unit is used to acquire the optical signal output through the micro / nano optical fiber.

[0095] Example 3: Verification of Output Characteristics and Stability of Passive Dual-Modal Tactile Sensor

[0096] The passive dual-modal tactile sensor of this invention exhibits significantly different waveform characteristics in the time domain in its output optical signal under different external motion stimuli, as shown in the attached figure. Figure 12 As shown, this enables the differentiation and recognition of various action states.

[0097] In non-contact mode, as the target object gradually approaches the sensor surface, the reflection and rescattering of the light emitted by the long-afterglow luminescent composite layer by the target continuously increase, improving the coupling efficiency of the returned light in the near-field region of the micro / nano fiber. This results in a continuous and smooth increase in the output optical signal as the target distance decreases. (See attached image) Figure 12 As shown in (a), the output signal in this stage has typical monotonic response characteristics: the light intensity continues to rise over time and gradually enters a saturated state, where the duration of saturation reflects the hovering behavior of the target object; the signal change process is smooth and without abrupt changes, and its rising slope is correlated with the target's approach speed.

[0098] When the target object moves laterally along the sensor surface in a non-contact state, the reflected back-coupling light is modulated in the time domain, causing the output optical signal to exhibit fluctuating characteristics. (See attached image) Figure 12 (b) and appendix Figure 12 (c) is divided into: low-frequency slow fluctuation characteristics: corresponding to the slow sweep of the target, characterized by a large gap between the peaks and a low rate of change; high-frequency fast fluctuation characteristics: corresponding to the fast sweep of the target, characterized by dense peaks and a significantly increased signal oscillation frequency.

[0099] In contact mode, when the target object comes into contact with the sensor surface and mechanical stress is applied, the trapped charge carriers inside the long afterglow luminescent composite layer are released under the action of local stress and undergo radiative recombination at the luminescence center, generating an additional mechanoluminescent signal, which significantly enhances the output light signal on the original afterglow background.

[0100] This additional output can be represented as:

[0101] (Equation 5);

[0102] in, For additional output optical signals in contact mode, The mechanoluminescence response coefficient, To be in relation to mechanical stress The relevant response function, This is the time modulation function related to the afterglow working interval.

[0103] Therefore, the total output optical signal in contact mode can be expressed as:

[0104] (Formula 6);

[0105] During the approach-contact continuous interaction process, the output optical signal exhibits a typical phased evolution behavior in the time domain: the initial contact instant corresponds to a sudden signal change or slope transition; the sustained force stage corresponds to signal enhancement and the formation of a quasi-steady plateau; and the release stage is characterized by a signal decline back to the background level. (See attached image) Figure 12 (d) The above dynamic processes together constitute a characteristic “M”-shaped waveform.

[0106] During the continuous change from approach to contact, the sensor's uniform output optical signal can be represented as:

[0107] (Equation 7);

[0108] Therefore, the target distance With mechanical stress The output optical signal is modulated by a reflection-backlight modulation mechanism and a mechanoluminescence modulation mechanism, respectively, so that the output signal forms a set of distinguishable characteristic patterns in the time domain, including: continuous smooth enhancement feature; low-frequency fluctuation feature; high-frequency fluctuation feature; and abrupt-enhancement-fallback composite feature.

[0109] Based on the above features, the present invention can distinguish and identify different external action states through a single optical output signal without the need for multiple sensing units or multiple signal channels, thereby achieving effective discrimination between non-contact proximity state and contact force state.

[0110] As attached Figure 13As shown, under cyclic loading conditions, the sensor of the present invention can maintain good output repeatability and response stability, indicating that the long afterglow luminescence composite layer and the micro-nano fiber heterostructure interface can still maintain a stable coupling state during multiple loading processes.

[0111] Example 4: Human-computer interaction application method:

[0112] As attached Figure 14 As shown, the passive dual-modal tactile sensor of the present invention is installed in the end of a mechanical finger, a flexible tactile interface, or an interactive control unit, and connected to a signal acquisition and detection unit, a photoelectric conversion and amplification circuit, a signal processing and control module, and a robotic arm execution unit, thereby forming a complete human-computer interaction system.

[0113] In this system, the original optical signal output by the sensor is converted into a corresponding electrical signal by the optical signal output and detection unit. Then, after amplification, filtering and baseline correction, it is input into the analog-to-digital conversion module, converted into a digital timing signal, and transmitted to the signal processing and control module for subsequent analysis.

[0114] As attached Figure 15 As shown, the signal processing and control module extracts features from the digital timing signal. These features include signal amplitude, rise slope, duration, fluctuation frequency, plateau length, and peak-valley distribution. Based on these features, it establishes action discrimination rules to distinguish and identify different interaction states. Specifically:

[0115] (1) When the signal shows low frequency and smooth change characteristics, it should be swept slowly (control action I - mechanical finger opens); (2) When the signal shows high frequency and dense oscillation characteristics, it should be swept quickly (control action II - mechanical arm swings); (3) When the signal shows monotonous rise and forms a platform structure, it should approach and stay (control action III - mechanical arm holds or releases); (4) When the signal shows periodic "M" wave or significantly enhanced oscillation characteristics, it should be contacted and interacted or acted continuously (control action IV - mechanical arm grasps).

[0116] By establishing the correspondence between the waveform features and the action state, we can intuitively distinguish between different interactive behaviors without adding extra sensing channels or complex structures.

[0117] After identifying the corresponding action state, the signal processing and control module maps the action recognition result into the corresponding control command and sends it to the robot arm execution unit to drive the robot arm to complete preset actions such as opening, swinging, grasping, holding or releasing.

[0118] As attached Figure 16As shown, in actual human-computer interaction, the sensor of this invention can generate time-series response signals with significant differences for various typical operations such as slow scanning, fast scanning, approaching and stopping, and contact action, and realize a continuous conversion process from "physical stimulus - optical response - action recognition - control output".

[0119] Therefore, this invention realizes dual-modal tactile perception and motion recognition based on a single optical signal, allowing users to obtain clear and intuitive interactive feedback through the system output without directly analyzing the original signal waveform, and has good application readability and engineering practical value.

Claims

1. A passive dual-modal tactile sensor, characterized in that: include: Long afterglow luminescence composite layer, micro-nano fiber optical signal transduction layer, flexible encapsulation layer, and optical signal output and detection unit; The long-afterglow luminescent composite layer is used to continuously release afterglow light after pre-excitation and generate mechanoluminescence signal under stress; the thickness of the long-afterglow luminescent composite layer is 0.2 mm. The micro / nano fiber optical signal transduction layer is disposed on the surface of the long-persistent light-emitting composite layer and forms a near-field coupling interface with the long-persistent light-emitting composite layer. It is used to capture and transduce the local light field generated by the long-persistent light-emitting composite layer into an output optical signal that propagates along the optical fiber. The flexible encapsulation layer covers the outside of the long afterglow luminescent composite layer and the micro-nano fiber optical signal transduction layer, and is used to fix the near-field coupling interface and provide flexible mechanical protection. The optical signal output and detection unit is connected to the micro / nano fiber optical signal transduction layer and is used to collect the output optical signal; the optical signal output and detection unit includes one or more of a photomultiplier tube (PMT) and a photon counter; The passive dual-modal tactile sensor, in a non-contact state, alters the local light field distribution at the near-field coupling interface through the reflection and rescattering of stray light by the target object, thereby generating a non-contact proximity response signal; in a contact state, the output light signal is modulated by the mechanoluminescence signal generated by the long-afterglow luminescent composite layer, thereby generating a contact force response signal. The non-contact proximity response signal and the contact force response signal are output and identified through the same micro-nano fiber optical signal transduction layer and the same optical signal output and detection unit.

2. The passive dual-modal tactile sensor according to claim 1, characterized in that, The basic afterglow photon flux of the long-afterglow luminescent composite layer decreases over time after pre-excitation, and its basic optical signal can be expressed as: (Equation 1); in, For a moment and wavelength The long afterglow photon flux, This represents the initial photon flux. These represent the lifetime constants corresponding to different trap energy levels. These are the corresponding weighting coefficients; The effective output fundamental optical signal formed by the long-afterglow luminescent composite layer at the near-field coupling interface of micro / nano optical fiber can be expressed as: (Equation 2); in, The basic output optical signal is generated by the long-afterglow luminescent composite layer and captured by micro / nano optical fibers. The coupling coefficient is determined by the micro / nano fiber structure parameters, burial depth, and interface coupling efficiency. In a non-contact state, when the target object is located at a distance above the sensor surface... At this point, the additional optical signal increment caused by the reflection and rescattering of stray photons by the target object can be expressed as: (Equation 3); in, This is an additional output optical signal in contactless mode. The modulation coefficient of the reflected light. Distance to target Related return optical coupling enhancement functions; Therefore, the total output optical signal in non-contact mode can be expressed as: (Equation 4); In the contact state, when the target object comes into contact with the sensor surface and mechanical stress is applied... At that time, the trapped charge carriers inside the long-afterglow luminescent composite layer are released under localized stress, generating an additional mechanoluminescence signal. This additional output can be expressed as: (Equation 5); in, For additional output optical signals in contact mode, The mechanoluminescence response coefficient, To be in relation to mechanical stress The relevant response function, For the time modulation function related to the afterglow working interval; Therefore, the total output optical signal in contact mode can be expressed as: (Formula 6); During the continuous interaction between proximity and contact, the unified output optical signal of the passive dual-modal tactile sensor can be expressed as: (Equation 7); Therefore, the target distance With mechanical stress The output light signal is modulated by a reflected light modulation mechanism and a mechanoluminescence modulation mechanism, respectively, so that the present invention has non-contact proximity sensing and contact force sensing capabilities in the same device and a single optical channel.

3. The passive dual-modal tactile sensor according to claim 1, characterized in that, The micro / nano fiber optical signal transduction layer consists of an input cone region, a waist region, and an output cone region, wherein the waist region is the main optical signal capture and coupling region; the micro / nano fiber waist region is disposed on the surface of the long afterglow luminescent composite layer; the diameter of the micro / nano fiber waist region is 11 μm, the waist region length is 5 mm, and the cone region length is 30 mm.

4. The passive dual-modal tactile sensor according to claim 1, characterized in that, The flexible encapsulation layer is a transparent elastic polymer layer used to maintain the relative positional stability between the micro / nano fiber optical signal transduction layer and the long afterglow luminescent composite layer under external force loading, bending, or repeated use conditions.

5. The passive dual-modal tactile sensor according to claim 1, characterized in that, The optical signal output and detection unit is connected to a signal processing and control module, which is used to amplify, filter, perform baseline correction, analog-to-digital conversion, feature extraction, action state discrimination, and control command generation on the output signal.

6. The passive dual-modal tactile sensor according to claim 5, characterized in that, The action state discrimination includes the identification of at least four types of actions: non-contact slow sweeping, non-contact fast sweeping, non-contact approaching and stopping in the normal direction, and contact pressing and releasing.

7. The passive dual-modal tactile sensor according to claim 5, characterized in that, The control commands are generated to map the identified motion states into control signals for the robotic arm to open, swing, grasp, hold, release, or standby.

8. A method for fabricating a passive dual-modal tactile sensor as described in any one of claims 1 to 7, characterized in that, The process includes the following steps: (1) mixing long-afterglow luminescent particles with an elastic polymer matrix to prepare a luminescent composite precursor liquid; (2) injecting the luminescent composite precursor liquid into a mold and curing it to form a long-afterglow luminescent composite layer; (3) preparing a micro-nano fiber by tapering a standard optical fiber; (4) placing the micro-nano fiber on the surface of the long-afterglow luminescent composite layer to form a near-field coupling interface; (5) flexibly encapsulating the long-afterglow luminescent composite layer and the micro-nano fiber to obtain the passive dual-modal tactile sensor.

9. A passive dual-modal tactile sensor as described in any one of claims 1 to 7, characterized in that: Applications of passive dual-modal tactile sensors in intelligent robotic arms, flexible electronic skin, human-computer interaction interfaces, or safe collaborative systems.

10. A human-computer interaction control system based on the tactile sensor according to any one of claims 1 to 7, characterized in that, It includes the tactile sensor and the robotic arm execution unit; wherein, the signal processing and control module in the tactile sensor is used to convert the raw optical signal output by the tactile sensor into motion recognition results, and further output the corresponding robotic arm control commands.

Images