A passive wearable identification system based on flexible micro-led and a manufacturing method thereof

Abstract

This application provides a passive wearable identification system based on flexible Micro-LEDs and its manufacturing method, relating to the field of flexible electronics and wearable devices. The system includes: a flexible hydrogel substrate with conductive properties; a Micro-LED display array integrated on or within the flexible hydrogel substrate for displaying text and image information; a Hydrogel-TENG energy harvesting unit integrated with the flexible hydrogel substrate for harvesting mechanical energy and converting it into electrical energy; a flexible conductive circuit connecting the Micro-LED display array and the Hydrogel-TENG energy harvesting unit for transmitting electrical energy to drive the Micro-LED display array; and a packaging structure for integrating the Micro-LED display array and the Hydrogel-TENG energy harvesting unit. This system can effectively capture low-frequency mechanical energy generated by daily human activities (such as walking, arm swinging, and joint bending) and convert it into stable electrical energy to drive the Micro-LED array to emit light, achieving visual information display.

Description

Technical Field

[0001] This application relates to the field of flexible electronics and wearable device technology, and more specifically, to a passive wearable identification system based on flexible Micro-LED and its manufacturing method. Background Technology

[0002] With the rapid development of the Internet of Things, artificial intelligence, and smart wearable technologies, wearable electronic devices have become an important direction for human-computer interaction, health monitoring, and identity recognition. Traditional wearable electronic devices mostly rely on rigid power supplies and rigid circuit boards, which have poor flexibility, low wearing comfort, and cannot operate self-powered for extended periods. This has greatly limited their application expansion in the fields of flexible electronics and smart wearables.

[0003] Micro-LEDs, as a next-generation display technology, possess advantages such as high brightness, high efficiency, low power consumption, long lifespan, and tiny pixel size, making them a key candidate for flexible wearable displays. However, existing Micro-LED display systems typically rely on rigid substrates or external power supplies, making it difficult to achieve tight adhesion with flexible substrates and skin surfaces. Stress concentration and electrode breakage can easily occur during bending or stretching, affecting luminous stability. Furthermore, rigid power modules make the overall structure bulky, which is not conducive to long-term wear and dynamic use.

[0004] To address these issues, researchers have proposed integrating flexible materials with display units. Commonly used flexible materials include polydimethylsiloxane (PDMS), polyurethane (PU) films, conductive elastomers, and conductive hydrogels. Among these, hydrogels, due to their high water content, low Young's modulus, and good biocompatibility, possess mechanical properties similar to skin, enabling a comfortable and conformable fit. By introducing ionic salts or conductive polymers into the hydrogel system, stable ionic conductivity can be achieved, giving it significant advantages in the construction of flexible electrodes and circuits.

[0005] However, achieving efficient and stable integration of rigid Micro-LED arrays on soft, moist hydrogel substrates remains a key challenge in this field. Traditional pick-and-place methods are inefficient, prone to damaging microstructure devices, and struggle to guarantee array integrity and luminescence consistency. Therefore, research into flexible integration methods has become a core direction for overcoming this problem.

[0006] Flexible hydrogels, capable of significant stretching and deformation while maintaining high transparency, are ideal supports and electrode carriers for Micro-LED arrays. However, existing flexible display devices still face the problem of strong energy supply dependence. While traditional lithium batteries or supercapacitors can provide stable energy, their rigid structure and limited lifespan make them difficult to integrate deeply with flexible display systems, while also increasing device thickness and safety risks. The development of triboelectric nanogenerator (TENG) technology offers a new approach to solving this bottleneck. TENGs can efficiently convert widely existing low-frequency mechanical energy in the environment (such as human movement, vibration, wind energy, or water droplet impact) into electrical energy, offering advantages such as strong material versatility, simple structure, low cost, and no need for external power supply. In particular, hydrogel-TENGs, constructed based on hydrogel materials, combine the high energy harvesting capacity of TENGs with the excellent flexibility, stretchability, and skin adaptability of hydrogel materials, becoming an important direction for realizing self-powered flexible wearable systems. Despite significant progress in both flexible Micro-LED displays and Hydrogel-TENG energy harvesting technology, the core challenge remaining to be addressed in this field is how to efficiently integrate the two to construct a fully flexible, stretchable, biocompatible, and self-powered passive signage system that can emit light through human movement.

[0007] Existing technologies suffer from the following shortcomings: Low structural integration: Display units and energy units are typically separate, leading to low energy transfer efficiency and system complexity. Difficulty in balancing flexibility and stability: Flexible substrates are prone to deformation or delamination, affecting the reliability of electrical connections. Complex manufacturing processes and high costs: Some Micro-LED flexible display devices rely on complex transfer and packaging processes, limiting large-scale manufacturing. Therefore, there is an urgent need for a passive wearable identification system that is structurally simple, highly flexible, self-powered, and capable of dynamic light emission, providing new technical solutions for scenarios such as intelligent human-computer interaction, motion monitoring, and identity recognition. Summary of the Invention

[0008] The embodiments of this application provide a passive wearable tagging system based on flexible Micro-LED and its manufacturing method, in order to solve the problems of existing flexible display devices, such as strong dependence on external power supply, poor flexibility, complex structure and insufficient comfort.

[0009] Other features and advantages of this application will become apparent from the following detailed description, or may be learned in part from practice of this application.

[0010] According to a first aspect of the embodiments of this application, a passive wearable identification system based on flexible Micro-LED is provided, comprising: Flexible hydrogel substrate with conductive properties; Micro-LED display arrays are integrated on or within the flexible hydrogel substrate for displaying text and image information; The Hydrogel-TENG energy harvesting unit is integrated with the flexible hydrogel substrate to harvest mechanical energy and convert it into electrical energy. A flexible conductive circuit connects the Micro-LED display array to the Hydrogel-TENG energy harvesting unit, and is used to transmit electrical energy to drive the Micro-LED display array to work; The packaging structure is used to integrate the Micro-LED display array and the Hydrogel-TENG energy harvesting unit into a single package.

[0011] In some embodiments of this application, based on the foregoing scheme, the flexible hydrogel substrate is composed of a polymer network, wherein the polymer network is doped with ionic salts for conducting electricity.

[0012] In some embodiments of this application, based on the foregoing scheme, the surface of the encapsulation structure is covered with a polyvinyl alcohol protective film or a polyurethane elastic layer.

[0013] In some embodiments of this application, based on the foregoing scheme, the Micro-LED display array is integrated onto or within the flexible hydrogel substrate using vapor phase assisted exfoliation and transfer technology.

[0014] In some embodiments of this application, based on the aforementioned scheme, the Hydrogel-TENG energy harvesting unit adopts a single-electrode structure, and its outer surface is covered with a friction layer for generating charge through friction with external objects.

[0015] In some embodiments of this application, based on the foregoing scheme, the flexible conductive circuit is prepared using liquid metal or conductive silver paste as the material and is fabricated using 3D printing or screen printing technology.

[0016] According to a second aspect of the embodiments of this application, a method for manufacturing a passive wearable tagging system based on flexible Micro-LED is provided, comprising: Preparation of flexible hydrogel substrates; Hydrogel-TENG energy harvesting units are integrated on a flexible hydrogel substrate; Micro-LED display arrays were transferred to flexible hydrogel substrates using vapor phase-assisted exfoliation and transfer technology. Construct a flexible conductive circuit to connect the Hydrogel-TENG energy harvesting unit with the Micro-LED display array; The entire system is encapsulated to form a passive wearable identification system.

[0017] In some embodiments of this application, based on the foregoing scheme, the preparation of the flexible hydrogel substrate includes: The hydrogel monomer, crosslinking agent, initiator and conductive ionic salt are mixed evenly in deionized water to form a precursor solution; The solution is injected into a prefabricated mold, and a photo-initiated or thermally-initiated polymerization reaction is carried out to solidify and form a flexible hydrogel substrate with excellent ionic conductivity, high tensile strength and biocompatibility.

[0018] In some embodiments of this application, based on the foregoing scheme, the transfer of the Micro-LED display array to a flexible hydrogel substrate using vapor-phase assisted lift-off and transfer technology includes: The pre-fabricated Micro-LED display array was completely peeled off from its original growth substrate using vapor phase-assisted peeling technology. The Micro-LED display array is bonded to the predetermined display area of ​​the prepared flexible hydrogel substrate using a high-precision alignment transfer device.

[0019] In some embodiments of this application, based on the foregoing scheme, the construction process of the flexible conductive circuit includes: Flexible conductive circuits are obtained by using 3D printing or screen printing technology to print conductive ink on a flexible hydrogel substrate or directly on the surface of the encapsulation layer.

[0020] The technical solution of this application has the following beneficial effects: 1. Completely passive and energy-autonomous: By efficiently integrating TENG, the device can convert the weak mechanical energy wasted in the daily movement of the human body into electrical energy to drive the Micro-LED to emit light, completely getting rid of dependence on external batteries and charging equipment, and achieving true energy autonomy and passive operation.

[0021] 2. Enhanced flexibility and wearing comfort: The core base uses a flexible hydrogel that is highly compatible with the mechanical properties of human skin, making the entire device as soft and stretchable as a "second skin". It can seamlessly conform to human surfaces (such as joints and curved surfaces) and adapt to various dynamic deformations, thus providing unprecedented wearing comfort.

[0022] 3. Excellent biocompatibility and safety: The selected hydrogel base materials (such as polyacrylamide and silk fibroin) are all recognized biocompatible materials that are non-toxic and non-irritating, allowing for safe contact with the skin for extended periods. They are particularly suitable for sensitive scenarios with high biocompatibility requirements, such as medical health monitoring and sports assistance.

[0023] 4. High-performance dynamic display: The integrated Micro-LED array inherits its inherent advantages of high brightness, high contrast, high resolution and fast response. Even in a self-powered low-power mode, it can achieve clear, stable and dynamic graphic or information display, meeting the functional requirements of wearable identification.

[0024] 5. Highly customizable and multifunctionally integrated: The modular design and manufacturing method of this invention is highly flexible, allowing for easy adjustment of the number and layout of TENG units to optimize energy output, changing the arrangement of Micro-LEDs to achieve different display effects, and even integrating other types of micro sensors to build a multifunctional smart wearable platform that integrates power supply, display, and sensing.

[0025] It should be understood that the above general description and the following detailed description are exemplary and explanatory only, and do not limit this application. Attached Figure Description

[0026] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with this application and, together with the description, serve to explain the principles of this application. It is obvious that the drawings described below are merely some embodiments of this application, and those skilled in the art can obtain other drawings based on these drawings without any inventive effort. In the drawings: Figure 1 A schematic diagram of a passive wearable tagging system based on flexible Micro-LED according to an embodiment of this application is shown; Detailed Implementation Exemplary embodiments will now be described more fully with reference to the accompanying drawings. However, these exemplary embodiments can be implemented in many forms and should not be construed as limited to the examples set forth herein; rather, these embodiments are provided to make this application more comprehensive and complete, and to fully convey the concept of the exemplary embodiments to those skilled in the art.

[0027] Furthermore, the described features, structures, or characteristics can be combined in any suitable manner in one or more embodiments. Numerous specific details are provided in the following description to give a thorough understanding of embodiments of this application. However, those skilled in the art will recognize that the technical solutions of this application can be practiced without one or more of the specific details, or other methods, components, apparatuses, steps, etc., can be employed. In other instances, well-known methods, apparatuses, implementations, or operations are not shown or described in detail to avoid obscuring various aspects of this application.

[0028] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of the embodiments of this invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this invention, and not all of them. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0029] The following detailed description of some embodiments of this application will be provided in conjunction with the accompanying drawings. Unless otherwise specified, the following embodiments and features can be combined with each other.

[0030] To address the limitations of existing wearable display devices in terms of flexibility, comfort, and power supply, this invention proposes a passive wearable tagging system that integrates flexible display, a biocompatible substrate, and self-powered functionality. The core idea of ​​this tagging system is to utilize the mechanical energy of human movement to generate electrical energy via a TENG (Temperature Energy Generator), which drives a micro-LED array integrated on a flexible hydrogel substrate, thereby achieving dynamic information display without the need for an external battery.

[0031] Specifically, the following provides a passive wearable identification system based on flexible Micro-LEDs, such as... Figure 1 As shown, the identifier includes: Flexible hydrogel substrate with conductive properties; Micro-LED display arrays are integrated on or within the flexible hydrogel substrate for displaying text and image information; The Hydrogel-TENG energy harvesting unit is integrated with the flexible hydrogel substrate to harvest mechanical energy and convert it into electrical energy. A flexible conductive circuit connects the Micro-LED display array to the Hydrogel-TENG energy harvesting unit, and is used to transmit electrical energy to drive the Micro-LED display array to work; The packaging structure is used to integrate the Micro-LED display array and the Hydrogel-TENG energy harvesting unit into a single package.

[0032] It should be noted that in this embodiment, the flexible hydrogel substrate is the core carrier of the entire label, playing multiple roles of support, encapsulation, and conductivity.

[0033] It should be noted that, in this embodiment, the Micro-LED display array, as an information display unit, is composed of tens of thousands of micron-sized (typically less than 100 μm) light-emitting diode units.

[0034] Micro-LED display arrays are precisely and extensively integrated onto or within a flexible hydrogel substrate using an advanced flexible transfer technology. This array can display preset static or dynamic graphics and text information based on input electrical signals, featuring high brightness, high resolution (up to 254 PPI or higher), and low power consumption.

[0035] It should be noted that in this embodiment, the Hydrogel-TENG energy harvesting unit, as a built-in self-powered module, is integrated with the flexible hydrogel substrate. This unit is used to efficiently harvest low-frequency mechanical energy generated by daily human movements (such as walking, arm swinging, and joint bending) and convert it into electrical energy.

[0036] It should be noted that, in this embodiment, the flexible conductive circuit serves as a bridge connecting the Hydrogel-TENG energy harvesting unit and the Micro-LED display array.

[0037] It should be noted that, in this embodiment, the encapsulation structure is made of the same material as the flexible hydrogel substrate.

[0038] Understandably, in some feasible embodiments, the shape of the flexible hydrogel substrate can be changed to make it serve as an encapsulation structure. In this case, the flexible hydrogel substrate simultaneously serves as a structural support, flexible electrode, and adhesive layer, integrating the Micro-LED display array and the Hydrogel-TENG energy harvesting unit into a soft and transparent overall structure.

[0039] In some feasible embodiments, based on the foregoing scheme, the flexible hydrogel substrate is composed of a polymer network doped with ionic salts for conducting electricity.

[0040] For example, the flexible hydrogel substrate is composed of a polymer network with high tensile strength (elongation at break exceeding 400%), low Young's modulus (similar to human skin), excellent biocompatibility, and high transparency (visible light transmittance greater than 90%). Preferred materials include polyacrylamide (PAM) hydrogel, natural silk fibroin (SF) hydrogel, or composites thereof. To achieve conductivity, ionic salts, such as lithium chloride (LiCl) or calcium chloride (CaCl2), are doped into the hydrogel network, making it an ionic conductor that can serve as both an electrode for the TENG and part of a connecting circuit.

[0041] In some feasible embodiments, based on the aforementioned scheme, the Hydrogel-TENG energy harvesting unit adopts a single-electrode structure, and its outer surface is covered with a friction layer for generating charge through friction with external objects.

[0042] For example, the Hydrogel-TENG energy harvesting unit employs a single-electrode TENG, which has a simple structure and is well-suited for wearable applications. In this mode, the flexible hydrogel substrate simultaneously serves as one electrode and part of the encapsulation layer of the TENG, while the elastomer (such as PDMS) covering its outer surface acts as a friction layer, generating electrical charges through friction with human skin or other external objects, thereby achieving energy harvesting.

[0043] In some feasible embodiments, based on the aforementioned scheme, the flexible conductive circuit is prepared using liquid metal or conductive silver paste as the material and is fabricated using 3D printing or screen printing technology.

[0044] For example, the flexible conductive circuit is made of a highly stretchable conductive material and is used to collect and transmit the weak electrical energy generated by the Hydrogel-TENG energy harvesting unit, ultimately driving the Micro-LED display array to emit light. To ensure circuit stability under large deformations of the device, it is preferable to use 3D printing technology to directly print liquid metal (such as gallium indium alloy) or conductive silver paste on a flexible substrate (such as PDMS) to construct the circuit. This circuit can withstand tensile strain of up to 40% while maintaining its conductive function.

[0045] In some feasible embodiments, based on the foregoing scheme, the surface of the encapsulation structure is covered with a polyvinyl alcohol protective film or a polyurethane elastic layer.

[0046] Understandably, the added polyvinyl alcohol protective film or polyurethane elastic layer enhances water resistance and mechanical durability. The entire device can be directly attached to the skin, fabric, or flexible substrate, enabling reusable and long-term use.

[0047] Based on the same inventive concept, this application also provides a manufacturing method corresponding to the above-mentioned identifier. This method achieves seamless integration of various functional units through modular integration and advanced manufacturing processes, specifically including: Step S100: Prepare a flexible hydrogel substrate; Step S200: Integrate Hydrogel-TENG energy harvesting units on a flexible hydrogel substrate; Step S300: The Micro-LED display array is transferred to a flexible hydrogel substrate using vapor phase assisted peeling and transfer technology; Step S400: Construct a flexible conductive circuit to connect the Hydrogel-TENG energy harvesting unit and the Micro-LED display array; Step S500: Perform overall packaging to form a passive wearable identification system.

[0048] Specifically, the process of step S100 is as follows: A precursor solution is formed by uniformly mixing hydrogel monomers (such as acrylamide or dissolved silk fibroin), crosslinking agents (such as N,N-methylenebisacrylamide (BIS)), initiators (such as ammonium persulfate (APS)), and conductive ionic salts (such as LiCl) in deionized water. The solution is then injected into a pre-made mold, and a photo-initiated or thermally-initiated polymerization reaction is performed to solidify and form a flexible hydrogel substrate with excellent ionic conductivity, high tensile strength, and biocompatibility.

[0049] Specifically, the process of step S200 is as follows: The flexible hydrogel substrate prepared in step S100 is used as the electrode, and it is partially or completely encapsulated using an elastomer with good triboelectric properties (such as PDMS). The outer surface of the elastomer serves as a triboelectric layer, which, together with the hydrogel electrode, constitutes a single-electrode TENG unit.

[0050] Specifically, the process of step S300 is as follows: Using vapor-phase assisted lift-off technology, the pre-prepared Micro-LED display array is completely peeled off from its original growth substrate. Then, using a high-precision alignment transfer device, the Micro-LED display array is precisely bonded to the predetermined display area of ​​the flexible hydrogel substrate prepared in step S100.

[0051] Specifically, the process of step S400 is as follows: Using technologies such as 3D printing or screen printing, a flexible conductive circuit connecting the output of the TENG unit and the input of the Micro-LED display array is printed on a flexible substrate or directly on the surface of the encapsulation layer using conductive ink (such as liquid metal or silver paste).

[0052] Specifically, the process of step S500 is as follows: The composite structure integrating all functional units undergoes final flexible encapsulation to protect internal components and enhance overall durability. The encapsulation material is also selected as flexible, transparent, and biocompatible, such as PDMS. After encapsulation, the device can be cut into specific shapes (such as armbands, badges, etc.) according to specific application requirements, resulting in a complete, stable, and wearable passive identification device.

[0053] The following are some specific examples of the preparation and implementation of the identifier.

[0054] Example 1: Fabrication of a passive wearable tagging system based on PAM hydrogel This implementation case aims to verify the feasibility of achieving light-emitting displays without external power supply during daily human movement by coupling a PAM / LiCl conductive hydrogel substrate with a single-electrode TENG and integrating a VPBT-transferred Micro-LED array with a flexible conductive circuit.

[0055] In this embodiment, PAM is used as the polymer backbone of the hydrogel. The specific preparation process is as follows: Step 1: Preparation of flexible conductive hydrogel substrate 7 g of AAM monomer, 4 mg of BIS as a chemical crosslinking agent, and 0.05 g of APS as a thermal initiator were dissolved sequentially in 25 mL of deionized water, and the solution was stirred thoroughly with a magnetic stirrer until a homogeneous and transparent solution was formed. Then, 2.12 g of LiCl was added to the solution as an ionic conductor, and stirring continued until completely dissolved. The addition of LiCl not only endowed the hydrogel with excellent ionic conductivity but also effectively locked in water through the hydration of lithium ions, improving the hydrogel's water retention and environmental stability. Finally, 60 μL of N,N,N',N'-tetramethylethylenediamine (TEMED) was added dropwise to the mixed solution as a catalyst for the polymerization reaction. After rapid and uniform stirring, the precursor solution was immediately injected into a pre-designed polytetrafluoroethylene (PTFE) mold. Upon standing at room temperature, the solution underwent a free radical polymerization reaction, forming a three-dimensional network structure, and finally solidified. The resulting product possesses high transparency (average visible light transmittance greater than 94%), high tensile strength (elongation at break exceeding 400%), and good ionic conductivity (conductivity approximately 3.8 × 10⁻⁶). - ² S·cm - ¹) PAM / LiCl conductive hydrogel substrate.

[0056] Step 2: Integration of TENG Units This embodiment employs a simple single-electrode triboelectric nanogenerator (TENG), using the PAM / LiCl hydrogel prepared in the previous step as the conductive electrode layer. Then, an elastomer material with good triboelectric negativity, such as polydimethylsiloxane (PDMS), is used to encapsulate the hydrogel. During encapsulation, the PDMS layer is ensured to cover one side of the hydrogel, forming a flat outer surface. This PDMS layer serves as the triboelectric layer of the TENG. When the encapsulated device is worn on the human body, the PDMS triboelectric layer undergoes periodic contact and separation with the skin (or clothing). According to the triboelectric sequence, skin tends to lose electrons and become positively charged, while PDMS tends to gain electrons and become negatively charged. During contact, charge transfer occurs at the interface; during separation, the negative charge accumulated on the PDMS surface creates an electric field, which induces cations (LiCl) in the underlying conductive hydrogel. + ) migrate to the PDMS / hydrogel interface, while anions (Cl) migrate to the PDMS / hydrogel interface. - The ions then gather at the other end, away from the interface. This redistribution of ions drives electron flow in the external circuit connected to the hydrogel electrodes, thereby generating an alternating current signal and converting the mechanical energy of human movement into electrical energy.

[0057] Step 3: Transfer and Integration of Micro-LED Display Array This embodiment employs an advanced, minimally damaging vapor-phase bulk transfer (VPBT) technique to integrate Micro-LEDs. First, a Micro-LED array (e.g., 100x100 pixels, 94μm x 94μm pixel size), already fabricated on a pristine rigid substrate (e.g., silicon) with a sacrificial layer (e.g., SiO2 or In) at the bottom, is placed in a reaction chamber filled with a specific chemical gas (e.g., HF or HCl). The gas undergoes a selective chemical reaction with the sacrificial layer; for example, HF etches the SiO2 layer, causing it to peel off from the substrate. After the reaction, a flexible stamp with low surface adhesion (e.g., a lightly cross-linked PDMS or temporary hydrogel) is used to "lift" the entire peeled Micro-LED array from the pristine substrate. Subsequently, using a high-precision alignment platform, the stamp carrying the Micro-LED array is aligned and bonded to a predetermined area of ​​the PAM / LiCl hydrogel substrate prepared in step one. By utilizing the energy difference between the stamp and the hydrogel surface, a Micro-LED array was successfully transferred onto a hydrogel substrate. This method achieves large-area, high-precision, and high-yield (up to 99%) transfer, and the transfer process is gentle, effectively protecting the photoelectric performance of the Micro-LED device.

[0058] Step 4: Construction of Flexible Conductive Circuit To connect the energy output of the TENG unit to the driving input of the Micro-LED array, a highly flexible conductive path needs to be constructed. This embodiment employs direct 3D printing technology to precisely print conductive ink along specific paths on the surface of the PDMS encapsulation layer or hydrogel substrate. The conductive ink can be a liquid metal such as gallium-indium alloy or a conductive silver paste containing a high concentration of silver nanoparticles. The printed circuit features a stretchable structure design, such as a serpentine or wavy shape, to accommodate bending and stretching during device use. Experiments show that this 3D-printed flexible circuit exhibits extremely low resistance change when subjected to tensile strain up to 40%, ensuring stable and efficient energy transfer from the TENG unit to the Micro-LED array.

[0059] Step 5: Overall Packaging and Application Demonstration The composite structure integrating the TENG unit, Micro-LED array, and flexible circuitry undergoes final flexible encapsulation to improve its mechanical durability and environmental stability. Transparent PDMS is also used as the encapsulation material. After encapsulation, a complete passive wearable tagging system is obtained. This tag is attached to the tester's arm. When the tester performs actions such as walking and arm swinging, the TENG unit continuously collects mechanical energy and generates electrical energy, which is sufficient to drive the Micro-LED array to emit light, stably displaying the preset "BNU" lettering. This demonstrates the feasibility and effectiveness of the design scheme proposed in this invention.

[0060] Example 2: Biocompatible labeling based on silk fibroin hydrogel This implementation case aims to improve skin adhesion and long-term wearing comfort by using silk fibroin (SF) conductive hydrogel, and to verify a biocompatible solution that can securely adhere to the skin and maintain self-powered luminescence without the need for additional adhesives.

[0061] To further enhance the device's overall biocompatibility, skin-friendliness, and long-term wearing comfort, this embodiment uses natural silk fibroin (SF) as the hydrogel base material. Silk fibroin is a natural protein extracted from silkworm silk, possessing excellent biocompatibility, biodegradability, good mechanical properties, and breathability, making it an ideal medical and skin-friendly material.

[0062] The core difference in the manufacturing method lies in the hydrogel preparation in step one. First, natural silk is treated using a standard degumming process to obtain pure silk fibroin fibers. Then, the degummed silk fibroin fibers are dissolved in a formic acid / calcium chloride (FA / CaCl2) mixed solvent system, and a homogeneous, viscous silk fibroin solution is obtained through vigorous stirring. This solution is cast into a flat mold to form a film. The formic acid solvent is slowly evaporated in a fume hood to obtain a dry SF film containing calcium chloride. Finally, this dry film is placed in a high relative humidity environment (e.g., 80% RH) to allow it to fully absorb moisture from the air, thereby spontaneously forming a conductive SF hydrogel containing CaCl2 ions. This SF hydrogel not only possesses good ionic conductivity but also exhibits excellent skin adhesion (shear strength exceeding 20 kPa) and superior breathability (water vapor transmission rate superior to commercial 3M breathable dressings) due to its unique chemical structure.

[0063] The subsequent steps, such as TENG unit integration, Micro-LED transfer, and flexible circuit construction, are essentially the same as in Example 1. Thanks to the natural adhesive properties of SF hydrogel, the final wearable tag can adhere firmly and comfortably to the skin without any additional adhesives, and can be worn continuously for several days without any discomfort or skin irritation. This highly biocompatible characteristic makes it particularly suitable for medical and health fields requiring long-term continuous monitoring, such as as a smart bandage displaying vital sign alerts or a dynamic rehabilitation guidance tag.

[0064] Example 3: Multifunctional Integration and Array Design This implementation case aims to improve the overall voltage / current output and achieve more complex dynamic pattern display and multi-functional integration by arraying TENG units in series and parallel and partitioning display / sensing functions.

[0065] The wearable tag of this invention can achieve multifunctional integration and arraying through structural design extensions. During the fabrication process, patterning techniques such as laser direct writing, photolithography, or high-precision photomasks can be used to precisely divide different functional areas on the same hydrogel substrate. For example, one area can be used for Micro-LED display, and another area can be used for TENG energy harvesting.

[0066] Through array design, larger-scale TENG energy harvesting arrays can be constructed. For example, multiple independent TENG units can be connected in series or parallel via flexible circuitry. Series connection can effectively increase the total output voltage to meet the requirements of driving devices such as blue or white Micro-LEDs that require higher turn-on voltages; parallel connection can increase the total output current, thereby driving larger area or higher brightness Micro-LED displays to display more complex dynamic patterns or animations.

[0067] Furthermore, the inherent sensitivity of hydrogel materials to environmental stimuli makes multifunctional integration possible. By introducing specific functional molecules or nanomaterials during the hydrogel synthesis process, it can be made to respond to temperature, humidity, pH, specific chemical substances, etc., typically manifested as changes in ionic conductivity or volume. For example, temperature-sensitive polymers can be integrated, causing the hydrogel's conductivity to change with temperature, thereby coupling the TENG's output signal with temperature information. By designing a corresponding decoding circuit, the wearer's body temperature or ambient temperature can be sensed while the display is self-powered. This integrated design, which deeply integrates display, power supply, and sensing functions, greatly expands the application scenarios of the passive wearable identification system of this invention, making it a truly intelligent wearable platform.

[0068] Example 4: Enhanced Mechanical Property Labeling Based on Dual-Network Hydrogels This implementation case aims to introduce PAM / SA-Ca² + Dual-network (DN) hydrogels enhance tear resistance and toughness, and their electrical and luminescent stability under conditions of significant tension, bending, and torsion is evaluated.

[0069] To cope with more intense human movement scenarios, such as sports training or heavy physical labor, this embodiment aims to improve the mechanical strength and durability of wearable tags. For this purpose, a double-network (DN) hydrogel is used as the base material. The DN hydrogel consists of two interpenetrating polymer networks with different properties: one network is rigid and fragile, acting as a "sacrificial network"; the other network is flexible and stretchable. When the material is subjected to stress, the rigid network breaks first, effectively dissipating a large amount of energy, thereby protecting the flexible network from damage. This results in the entire material exhibiting toughness and strength far exceeding that of a single-network hydrogel.

[0070] The specific fabrication method is as follows: First, the first-layer network is prepared. Sodium alginate (SA) is dissolved in water, and acrylamide (AAm) monomer, lithium chloride (LiCl), and an initiator are added. This mixed solution is polymerized to form a preliminary network composed of polyacrylamide (PAM) containing sodium alginate chains. Subsequently, this hydrogel is immersed in a solution containing divalent cations (such as Ca²⁺). + In a solution of Ca²⁺. + It undergoes ionic cross-linking with the carboxyl groups on the sodium alginate chain, forming a second rigid network. By adjusting the cross-linking density and ratio of the two networks, the final mechanical properties of the hydrogel can be precisely controlled, resulting in a several-fold increase in tear strength and toughness while maintaining high tensile strength. For example, the prepared DN hydrogel can achieve a tensile stress of up to 2.1 MPa and a toughness as high as 6.5 MJ·m. - ³.

[0071] Using this highly resilient DN hydrogel as a substrate, TENG units and a Micro-LED array were integrated according to the method in Example 1. The resulting passive wearable tagging system exhibits extremely high mechanical robustness, capable of withstanding repeated large-amplitude stretching, bending, and torsion without breakage, while maintaining stable internal conductive pathways and display functions. This enhanced tagging system is particularly suitable for fields with stringent requirements for device durability, such as monitoring the physiological state of athletes and identifying military personnel.

[0072] Example 5: Wearable tag with self-healing function This implementation case aims to construct a structure containing catechol-Fe³ + A self-healing conductive hydrogel with dynamic coordination / reversible hydrogen bonding was developed to verify its ability to restore conductivity and luminescence functions at room temperature after cutting damage.

[0073] During long-term use, wearable devices inevitably encounter mechanical damage such as scratches and tears. To extend the lifespan of the devices and improve their reliability, this embodiment introduces a self-healing function. A hydrogel substrate based on dynamic reversible chemical bonds is designed, enabling it to automatically repair its structure and function after damage.

[0074] This embodiment introduces a dynamic metal-ligand coordination network or a reversible hydrogen bond network into the hydrogel network. For example, in the synthesis system of polyacrylamide (PAM) hydrogels, monomers containing catechol groups (mimicking mussel adhesive proteins) and metal ions (such as Fe³⁺) are introduced. + The catechol groups can form dynamic, reversible coordination bonds with metal ions. When a hydrogel is cut or scratched, the coordination bonds at the fracture interface break. However, when the two fractured surfaces are reattached, the polymer chains at the interface diffuse, and the catechol groups and metal ions reform new coordination bonds, thus "stitching" the two fractured surfaces together and repairing the structure. Simultaneously, because the ionic conductivity pathway is also restored, the electrical properties of the hydrogel are also repaired.

[0075] Experiments have shown that when a hydrogel tag integrating a Micro-LED and powered by a TENG is cut in half, the circuit is broken and the Micro-LED turns off. After placing the two cut surfaces in close contact and leaving them at room temperature for several hours, the mechanical strength and conductivity of the hydrogel recover to near-original levels (e.g., an electrical performance recovery rate of up to 94.4%). At this point, by simulating human movement and driving the TENG again, the Micro-LED is observed to re-illuminate. This self-healing capability significantly enhances the durability and reliability of wearable tags, reduces the risk of device failure due to accidental damage, and opens up new avenues for the design of wearable electronic devices.

[0076] Example 6: Organic hydrogel labeling resistant to extreme environments This implementation case aims to provide antifreeze and moisturizing effects using an ethylene glycol / glycerol-water organic hydrogel system, and to evaluate the stability and durability of TENG and Micro-LED in -30 °C and low humidity environments.

[0077] Traditional hydrogels harden and become brittle at low temperatures due to freezing, and shrink and fail due to water loss in dry environments, limiting their application in cold or arid regions. This embodiment aims to develop a wearable tag that can operate stably over a wide temperature and humidity range, using an organic hydrogel as the substrate.

[0078] Organic hydrogels are a special type of gel system whose solvent is a mixture of water and one or more organic solvents (such as ethylene glycol, glycerol, etc.). The introduction of organic solvents can significantly alter the physicochemical properties of the gel. For example, ethylene glycol, as an excellent antifreeze agent, can form hydrogen bonds with water molecules, effectively disrupting the water crystal network and thus lowering the freezing point of the hydrogel to -30°C or even lower. Meanwhile, high-boiling-point, low-volatility organic solvents such as glycerol can effectively inhibit water evaporation, allowing the hydrogel to remain moist and flexible for extended periods even in dry environments.

[0079] In the specific preparation process, in the PAM / LiCl hydrogel system of Example 1, a binary mixed solvent of ethylene glycol and water was used instead of pure water as the solvent. By adjusting the ratio of ethylene glycol to water, the antifreeze and moisturizing properties of the organic hydrogel can be precisely controlled. This environmentally resistant organic hydrogel was used as a substrate, and a TENG and Micro-LED were integrated. The fabricated wearable tag remained flexible and conductive at a low temperature of -30°C, and the TENG unit functioned normally, driving the Micro-LED to emit light. Furthermore, its performance did not significantly degrade after being placed in a room temperature, low humidity environment for several days. This environmentally resistant characteristic makes the wearable tag of this invention suitable for special scenarios such as polar scientific expeditions, high-altitude operations, and desert exploration, greatly expanding its application range.

[0080] Other embodiments of this application will readily conceive of by those skilled in the art upon consideration of the specification and practice of the embodiments disclosed herein. This application is intended to cover any variations, uses, or adaptations of this application that follow the general principles of this application and include common knowledge or customary techniques in the art not disclosed herein. It should be understood that this application is not limited to the precise structures described above and shown in the accompanying drawings, and various modifications and changes can be made without departing from its scope. The scope of this application is limited only by the appended claims.

Claims

1. A flexible Micro-LED based passive wearable identification system, characterized in that, The application relates to a passive wearable identification system. The application comprises: a flexible hydrogel substrate with electrically conductive function; a Micro-LED display array integrated on or in the flexible hydrogel substrate for displaying text and image information; a Hydrogel-TENG energy harvesting unit integrated with the flexible hydrogel substrate for harvesting mechanical energy and converting the mechanical energy into electrical energy; a flexible conductive circuit connecting the Micro-LED display array and the Hydrogel-TENG energy harvesting unit for transmitting electrical energy to drive the Micro-LED display array to work; 2. The passive wearable identification system of claim 1, wherein, an encapsulation structure for integrally encapsulating the Micro-LED display array and the Hydrogel-TENG energy harvesting unit.

3. The passive wearable identification system of claim 1, wherein, The flexible hydrogel substrate is composed of a polymer network doped with ionic salt for electric conduction.

4. The passive wearable identification system of claim 1, wherein, The surface of the encapsulation structure is covered with a polyvinyl alcohol protective film or a polyurethane elastic layer.

5. The passive wearable identification system of claim 1, wherein, The Micro-LED display array is integrated on or in the flexible hydrogel substrate by a gas-phase assisted exfoliation and transfer printing technology.

6. The passive wearable identification system of claim 1, wherein, The Hydrogel-TENG energy harvesting unit adopts a single-electrode structure, and the outer surface is covered with a friction layer for generating electric charges by rubbing against external objects. 7.A manufacturing method of a passive wearable identification system based on flexible Micro-LEDs, characterized in that, The flexible conductive circuit is prepared by using liquid metal or conductive silver paste as the preparation material and by adopting a 3D printing or screen printing technology. The application relates to a passive wearable identification system. The application comprises: preparing a flexible hydrogel substrate; integrating a Hydrogel-TENG energy harvesting unit on the flexible hydrogel substrate; transferring a Micro-LED display array to the flexible hydrogel substrate by a gas-phase assisted exfoliation and transfer printing technology; 8. The method of manufacturing according to claim 7, wherein, constructing a flexible conductive circuit to connect the Hydrogel-TENG energy harvesting unit and the Micro-LED display array; performing overall encapsulation to form the passive wearable identification system. The preparation of the flexible hydrogel substrate comprises:

9. The method of manufacturing according to claim 7, wherein, mixing hydrogel monomers, a crosslinking agent, an initiator and conductive ionic salt in deionized water to form a precursor solution; injecting the solution into a prefabricated mold, and curing to form a flexible hydrogel substrate with excellent ionic conductivity, high tensile property and biocompatibility by a photo-induced or thermal-induced polymerization reaction. The transferring of the Micro-LED display array to the flexible hydrogel substrate by the gas-phase assisted exfoliation and transfer printing technology comprises:

10. The method of manufacturing according to claim 7, wherein, adopting a gas-phase assisted exfoliation technology to completely exfoliate a prefabricated Micro-LED display array from its original growth substrate; attaching the Micro-LED display array to a predetermined display area of the prepared flexible hydrogel substrate by a high-precision alignment transfer device. The construction process of the flexible conductive circuit comprises: adopting a 3D printing or screen printing technology to print the flexible conductive circuit on the flexible hydrogel substrate or directly on the surface of the encapsulation layer by using conductive ink.

Images