Flexible electronic skin system based on magnetorheological fluid microneedle structure

Abstract

The invention belongs to the field of flexible electronic devices, and particularly relates to a flexible electronic skin system based on a magnetorheological fluid microneedle structure. According to the system, a micro-needle array filled with magnetorheological fluid is constructed on a flexible substrate, and dynamic adjustment of local rigidity and deformation characteristics of the micro-needle array is achieved under the action of an external magnetic field; a sensing electrode array is integrated below or inside the microneedle array; the microneedle array deforms under the action of stress, the distance or contact state change between the microneedle array and the integrated sensing electrode array is converted into capacitance, resistance or impedance signals, multi-point distributed touch or pressure sensing is achieved, and real-time acquisition and output are completed through the sensing electrode array and the signal processing module. The magnetorheological fluid is encapsulated in the hollow microneedle array structure for the first time, an arrayed flexible arrangement form is constructed, dynamic reversible adjustment of the rigidity of the microneedle unit between a liquid state and a solid-like state under the action of an external magnetic field is achieved, and the micro-needle array structure is suitable for flexible wearable equipment and a bionic interaction interface.

Description

Technical Field

[0001] The present invention belongs to the field of flexible electronic devices and intelligent response materials, and specifically relates to a flexible electronic skin system based on a magnetorheological fluid microneedle structure. Background Art

[0002] Electronic skin is a flexible electronic system that mimics the functions of human skin, capable of sensing external physical stimuli such as pressure, touch, temperature, and humidity. It is widely used in intelligent robots, bionic prostheses, wearable medical devices, and human-computer interaction systems. In recent years, with the advancement of materials science, micro-nanofabrication, and flexible electronics, research on electronic skin has continued to advance. The core of this approach lies in integrating sensor devices onto a flexible substrate, enabling it to achieve a certain degree of stretchability and adherence while maintaining high sensitivity to external signals. Traditional electronic skin implementations typically rely on piezoresistive, piezoelectric, capacitive, or inductive sensing mechanisms. Piezoresistive, for example, involves embedding conductive materials (such as carbon nanotubes, graphene, and silver nanowires) within a flexible substrate. When subjected to external pressure or strain, the contact resistance or path of the conductive network changes, generating a measurable electrical signal. Capacitive structures typically consist of two sensing electrode arrays and a dielectric layer. When pressure is applied, the spacing between the electrodes or the active area changes, resulting in a change in capacitance. Most of these structures use highly elastic polymers such as PDMS and Ecoflex as the substrate, have good flexibility and conformability, and are suitable for skin contact applications.

[0003] In recent years, researchers have introduced a variety of microstructure designs to improve sensitivity and spatial resolution, such as microbumps, microprisms, and microchannels. These structures can generate localized stress concentrations under external forces, thereby amplifying the electrical response. For example, some studies have used microetching molds to create micropattern arrays on PDMS surfaces, enhancing sensing performance by altering the contact area and strain distribution. Furthermore, some studies have incorporated liquid metals or ion gels into microstructures to achieve higher flexibility and biocompatibility, meeting the requirements of medical-grade wearable devices. In addition to passive microstructural enhancements, flexible electronic skins have also incorporated active control mechanisms. For example, temperature-responsive materials (such as PVDF and liquid crystal elastomers) are used to achieve thermally induced deformation, or structural changes are driven by controllable magnetic and electric fields. These approaches primarily focus on the design and enhancement of response mechanisms, aiming to achieve functions such as controllable deformation, active sensing, and multimodal signal output. In some studies, magnetically responsive particles are incorporated into elastic materials, causing the overall structure to deform under an external magnetic field, resulting in applications such as flexible actuators or auxiliary sensing units. The application of magnetically responsive materials in flexible structures has also garnered attention. For example, some researchers have dispersed carbon-based magnetic particles in PDMS to construct magnetically responsive composite films for use in magnetically controlled attachment systems or flexible positioning devices. Other studies have encapsulated magnetic droplets in flexible microcavities, guiding their deformation under the influence of a magnetic field to achieve structural motion control. These approaches primarily focus on material response and actuation, with the core aim being to modulate dynamic behavior by altering material morphology or properties through external magnetic fields. Microneedle structures, due to their unique geometry and application potential, are also being widely explored in flexible electronics. Microneedles are commonly used in biosignal acquisition, drug delivery, and transdermal sensing, offering minimally invasive properties, strong local penetration, and high spatial resolution. Traditional microneedles are mostly made of silicon, metal, or polymer materials, and their mechanical properties are largely fixed after fabrication. Other studies have used injectable or dissolving microneedles for short-term applications, such as sensor patches or disposable biosampling devices. In flexible electronic skin research, microneedle structures are primarily used to enhance the mechanical coupling between the sensor and the skin, improving signal acquisition accuracy.

[0004] Current flexible electronic skin technology has achieved considerable maturity in achieving basic functions such as pressure sensing and tactile detection. However, significant shortcomings remain in areas such as high-sensitivity response, adaptive structural control, and multi-point distributed sensing. First, existing electronic skins are mostly based on conductive polymers, nanocomposites, or static microstructures. Their sensitivity is typically fixed, making it difficult to dynamically adjust to varying external forces or application scenarios. This "single response curve" characteristic limits their adaptability in complex environments, particularly in scenarios requiring adjustable sensing accuracy and recognition of different tactile levels. Second, while some research has attempted to enhance sensing performance by incorporating microstructure arrays, such as microbumps, microchannels, or surface micropatterns, these structures are essentially fixed in shape and stiffness after molding, making it difficult to actively control their response behavior. In practical applications, different scenarios require different mechanical compliance, interference immunity, and response speed for the sensing structure, making fixed-parameter structures inadequate for comprehensive performance. Furthermore, current flexible electronic skin microstructures are mostly two-dimensional or planar, lacking spatial tactile enhancement methods, limiting the accuracy and resolution of signal distribution.

[0005] In the prior art, there is already a certain foundation for research on flexible sensing of magnetorheological fluids. For example, patent CN115201286A discloses a flexible sensor based on magnetorheological fluid, which uses the changes in the rheological properties and conductivity of magnetorheological fluid under the action of a magnetic field to achieve the strain sensing function of the flexible device, providing a material design basis for the application of magnetorheological fluid in flexible sensing systems. In terms of magnetic regulation of microneedle structures, patent CN102755691A discloses a magnetic microneedle array and its preparation method, which uses magnetic materials to construct a microneedle structure and can achieve control and positioning of the array under the drive of an external magnetic field. This scheme introduces magnetic response characteristics into the microscale structure. In terms of the integration of sensing functions of microneedles, patent CN104114224A proposes a microneedle array for biosensing and drug delivery, integrating electrodes in the microneedle structure to achieve real-time detection of biological molecules in body fluids, and providing a path for the fusion of microneedles and sensor devices. Although the above technologies have made certain progress in magnetorheological materials, magnetically controlled microneedle structures and microneedle sensing functions, there is currently no public solution to directly encapsulate magnetorheological fluid inside the microneedle structure and coordinately design it with the electrode array to construct an integrated electronic skin system with dynamic stiffness adjustment capabilities and multi-point tactile perception functions. Summary of the Invention

[0006] In response to the above technical problems, the present invention is proposed on the basis of this technical gap, integrating the adjustable response characteristics of magnetorheological materials, the spatial structural advantages of microneedle arrays and the integrated signal sensing design of flexible electronics, to construct a new, functionally adjustable and responsive flexible electronic skin system based on magnetorheological fluid microneedle structure. By constructing a microneedle array filled with magnetorheological fluid on a flexible substrate, the system can dynamically adjust the local stiffness and deformation characteristics of the microneedles under the action of an external magnetic field, thereby adjusting the response sensitivity according to different tactile needs. At the same time, the three-dimensional morphology of the microneedle structure enhances the spatial resolution of the sensing signal, and cooperates with the integrated electrode array below to achieve multi-point synchronous detection and signal output. The present invention has a simple structure, is easy to integrate, and has both softness, adaptability and high sensitivity. It is suitable for a variety of complex scenarios such as robot skin, wearable devices and human-computer interaction systems.

[0007] The flexible electronic skin system provided by the present invention constructs a microneedle array filled with magnetorheological fluid on a flexible substrate, and dynamically adjusts the local stiffness and deformation characteristics of the microneedle array under the action of an external magnetic field;

[0008] A sensing electrode array is integrated under or inside the microneedle array; the microneedle array deforms under the action of force, and the change in distance or contact state with the integrated sensing electrode array is converted into capacitance, resistance or impedance signals, realizing multi-point distributed tactile or pressure perception, and completing real-time acquisition and output through the flexible sensing electrode array and signal processing module.

[0009] In the technical solution of the present invention, the electronic skin system includes a flexible substrate, multiple microneedle units, a magnetorheological fluid filling structure, an external magnetic control device, a sensing electrode array, and a signal processing module; wherein:

[0010] A plurality of microneedle units form a microneedle array; a flexible substrate is used to support the entire microneedle array;

[0011] The microneedle units are distributed on the upper surface of the flexible substrate. Each microneedle unit has a closed cavity inside, and the cavity is filled with magnetorheological fluid to form a magnetorheological fluid filling structure.

[0012] The external magnetic control device is used to apply an external magnetic field to the microneedle unit to adjust the rheological state of the magnetorheological fluid and realize dynamic reversible regulation of the microneedle stiffness state;

[0013] The sensing electrode array is arranged under the microneedle or embedded in the microneedle structure to collect changes in resistance, capacitance, impedance, current, piezoelectric signals or field effect transmission characteristics, thereby realizing real-time perception and output of tactile or pressure signals.

[0014] The signal processing module is connected to the sensing electrode array and is used to collect, analyze, convert and output tactile or pressure sensing signals to the display or control terminal.

[0015] Furthermore, the flexible substrate is made of polydimethylsiloxane (PDMS) or ecoflex00-50, 00-30, 00-20, dragonskin, etc., which have excellent flexibility, stretchability and biocompatibility, and are suitable for attachment to human skin, flexible mechanical surfaces or non-flat carrier surfaces. The upper surface of the flexible substrate is used to fix the microneedle array, and the lower surface is preset with a conductive electrode layer.

[0016] Furthermore, each microneedle unit is a hollow conical structure, a flat columnar structure, a grooved structure or a multi-cavity composite microneedle structure. The height of the microneedle unit is 5 mm and is prepared by a photocurable resin 3D printing micro-nano manufacturing method.

[0017] Furthermore, the microneedle material of the microneedle unit includes a photocurable resin, one of polyimide, thermoplastic polyurethane, and polycaprolactone flexible polymer materials.

[0018] Furthermore, the sensing mode between the microneedle unit and the sensing electrode array is surface contact, field sensing, electric field modulation or dielectric modulation.

[0019] Furthermore, the magnetorheological fluid is composed of carbonyl iron powder and a silicon-based carrier liquid, and the mass ratio of carbonyl iron powder in the magnetorheological fluid is 35%; the magnetorheological fluid is in a liquid state under non-magnetic field conditions, giving the microneedles good softness; under the condition of applying an external magnetic field, its rheological properties change and turn into a quasi-solid state, which significantly improves the local stiffness of the microneedles, thereby achieving the adjustment of response sensitivity.

[0020] Furthermore, the flexible substrate has a certain degree of elasticity and adherence, adapting to the application requirements of surfaces with different curvatures;

[0021] Furthermore, the sensing electrode array is arranged under the microneedle or in the microneedle structure, and the real-time perception and output of tactile or pressure signals are achieved by monitoring the changes in resistance, capacitance or impedance of the microneedle under the action of external force.

[0022] Furthermore, the magnetic control device adopts an embedded coil, an external permanent magnet or an electromagnetic field system.

[0023] The present invention may further include a signal processing module for collecting, analyzing and converting multi-point sensing signals and outputting them to a display or control terminal to achieve intelligent feedback or closed-loop control.

[0024] The electronic skin system of the present invention has good flexibility, adjustable sensitivity, high spatial resolution and multi-point detection capability, and is suitable for complex and changeable tactile recognition environments such as bionic robots, intelligent prostheses, and wearable health monitoring.

[0025] This invention constructs a flexible electronic skin containing a magnetorheological fluid (MRF)-filled microneedle array. This system dynamically adjusts the microstructure's stiffness under magnetic field control, and combines an electrode array with a signal processing system to achieve multi-point, high-precision acquisition of external tactile and pressure signals. The key lies in introducing the magnetorheological fluid (MRF) as an active response material into the microscale sensing structure, and incorporating it into an externally controlled magnetic field to achieve adaptive sensing behavior. The result is a biomimetic electronic skin system with spatial resolution, adjustable sensitivity, and soft, conformable properties.

[0026] Compared with the prior art, the present invention has the following beneficial effects:

[0027] (1) Structural integration innovation: Based on the flexible structural design and stiffness control mechanism of magnetorheological fluid-filled microneedles, a flexible and adjustable three-dimensional microneedle array is realized:

[0028] This invention, for the first time, encapsulates a magnetorheological fluid (MRF) within a hollow microneedle array structure, creating a flexible array arrangement that dynamically and reversibly adjusts the microneedle unit's stiffness between a liquid and a near-solid state under an applied magnetic field. This flexible integration of three-dimensional microstructures overcomes the limitations of traditional two-dimensional flexible electronic skin and static, rigid microneedles, improving the structure's adaptability and safety on complex surfaces.

[0029] (2) Multi-point collaborative perception: a multi-point tactile perception system constructed by the microneedle structure and the electrode array to improve the spatial resolution and sensitivity of tactile recognition:

[0030] The microneedle array of this invention, combined with an array of sensing electrodes integrated into or within the microneedle, creates a real-time electrical sensing unit capable of converting tactile or pressure stimuli into output signals such as capacitance and resistance. This distributed array enables simultaneous multi-point sensing. Compared to existing single-point or passive detection solutions, this invention offers higher signal accuracy, a wider recognition range, and enhanced multimodal tactile recognition capabilities.

[0031] (3) Introducing a closed-loop magnetic control system to achieve dynamic adjustment of sensing sensitivity and system adaptation:

[0032] The magnetic control device of the present invention utilizes a zoned, embedded array of flexible electromagnetic coils to independently regulate the magnetic field strength of the microneedles in each region, thereby actively adjusting the stiffness and response characteristics of the microneedles. Furthermore, a complete closed-loop sensing and control system is constructed by combining analog-to-digital conversion, a microcontroller unit (MCU), and a communication module, creating a closed-loop "perception-control-feedback" system architecture. This system possesses adaptability, programmability, and environmental adaptability, surpassing existing one-way response or non-adjustable systems and making it suitable for flexible wearable devices and biomimetic interactive interfaces. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 Schematic diagram of the structure of the flexible electronic skin system of the present invention;

[0034] Figure 2 Schematic diagram of flexible electronic skin monitoring of the present invention;

[0035] Figure 3 is a SEM image of the microneedle array of the present invention;

[0036] Figure 4 This is a SEM image of the microneedle array after cutting of the present invention;

[0037] Figure 5 Graph showing the stiffness change of the microneedle array of the present invention under a magnetic field;

[0038] Figure 6 Graph showing capacitance / impedance variation under different pressure conditions (50 Pa to 2 kPa) of Example 1 of the present invention;

[0039] Figure 7 This is a graph showing the change in stiffness of the microneedle array under an external magnetic field (0-500 mT) in Comparative Example 1 of the present invention. DETAILED DESCRIPTION

[0040] The following embodiments are merely some of the embodiments of the present invention, rather than all of them. Therefore, the detailed description of the embodiments of the present invention provided below is not intended to limit the scope of the claimed invention, but rather merely represents selected embodiments of the present invention. All other embodiments derived by those skilled in the art based on the embodiments of the present invention without creative effort are intended to fall within the scope of protection of the present invention.

[0041] In the present invention, unless otherwise specified, all equipment and raw materials can be purchased from the market or are commonly used in the industry. The methods in the following embodiments, unless otherwise specified, are all conventional methods in the art.

[0042] Without departing from the core technical concept of the present invention, in order to adapt to different usage scenarios, manufacturing requirements and material selection, some structures, material compositions and control methods of the present invention can be equivalently replaced or changed, and can also be extended to other application fields with tactile perception requirements to enhance its versatility and patent protection coverage.

[0043] Example 1:

[0044] The electronic skin system of the present invention mainly includes the following modules: a flexible substrate, multiple microneedle units, a magnetorheological fluid filling structure, an external magnetic control device, a sensing electrode array, and a signal processing module;

[0045] Among them, multiple microneedle units form a microneedle array; the flexible substrate is used to support the entire microneedle array;

[0046] The microneedle units are distributed on the upper surface of the flexible substrate. Each microneedle unit has a closed cavity inside, and the cavity is filled with magnetorheological fluid to form a magnetorheological fluid filling structure.

[0047] The external magnetic control device is used to apply an external magnetic field to the microneedle unit to adjust the rheological state of the magnetorheological fluid and achieve dynamic and reversible regulation of the microneedle stiffness state;

[0048] The sensing electrode array is arranged under the microneedle or embedded in the microneedle structure to collect changes in resistance, capacitance, impedance, current, piezoelectric signals or field effect transmission characteristics, thereby realizing real-time perception and output of tactile or pressure signals.

[0049] The signal processing module is connected to the sensing electrode array and is used to collect, analyze, convert and output tactile or pressure sensing signals to the display or control terminal.

[0050] like Figure 1 The figure shows the structural layout of the various components of the electronic skin. Multiple hollow microneedle units are regularly arranged on a flexible substrate, with the base of each microneedle unit corresponding to the sensing electrode array. A flexible coil is embedded in the flexible substrate, and wires are connected to the magnetic field control circuit and signal processing module on the back. The overall structure of the electronic skin forms a flat, attachable electronic sensing device. Figure 2 A schematic diagram showing the flexible electronic skin monitoring of the present invention.

[0051] The flexible substrate, the supporting layer of the electronic skin, is made of polydimethylsiloxane (PDMS), which exhibits excellent flexibility, stretchability, and biocompatibility, making it suitable for attachment to human skin, flexible mechanical surfaces, or uneven support surfaces. The upper surface of the substrate is used to secure the microneedle array, while the lower surface is pre-configured with a conductive electrode layer.

[0052] like Figure 3 The SEM image of the microneedle array is shown. The microneedle array is cylindrical and conical, with a height of generally 5 mm. It is prepared by using a photocurable resin 3D printing micro-nano manufacturing method. The microneedle array is cut and then scanned by SEM. Figure 4 The hollow structure diagram shown. The cavity of each microneedle unit is injected with magnetorheological fluid (MRF), which is composed of carbonyl iron powder and low-viscosity silicone oil carrier liquid. The mass ratio of carbonyl iron powder in the magnetorheological fluid is 35%. When there is no external magnetic field, the magnetorheological fluid is in a low-viscosity liquid state, and the microneedle unit is soft as a whole; under the action of the external magnetic field, the magnetic particles form a chain structure along the direction of the magnetic field, causing it to quickly transform into a solid-like state, significantly improving the stiffness of the microneedle. Figure 5As shown in the figure, the stiffness change of the microneedle unit under the magnetic field reaches about 10000%. This change directly affects the deformation of the microneedle when it is subjected to force, and then affects the contact area or distance between it and the bottom sensing electrode, thereby realizing dynamic response adjustment to touch or pressure.

[0053] The sensing electrode units are located below the corresponding positions of the microneedle array, forming an arrayed impedance / capacitance sensing module. The sensing electrodes are made of silver nanowires, deposited on the substrate surface via a spray coating process. Mechanical stimulation is converted into electrical signals by varying the contact area or spacing between the microneedle base and the electrodes. This module can construct impedance, capacitive, or piezoresistive sensor arrays, with wiring centralized to the peripheral signal processing area.

[0054] The signal processing module includes a signal amplification circuit, an analog-to-digital converter, and an image processing unit, which can support real-time tactile mapping, pressure level classification output, or remote tactile feedback response.

[0055] It should be noted that, first of all, in terms of the structural form of the microneedle unit, although the present invention preferably uses a hollow conical microneedle and encapsulates a magnetorheological fluid, in alternative designs, a flat cylindrical, grooved structure or a multi-cavity composite microneedle structure can also be used to enhance fluid stability or improve the magnetic conductivity of the microneedle in a bent state. In addition, the material of the microneedle is not limited to photocurable resin, but can also be replaced by flexible polymer materials such as polyimide (PI), thermoplastic polyurethane (TPU), polycaprolactone (PCL) with good formability and mechanical properties to adapt to different manufacturing processes such as molding, injection molding, hot pressing, etc.

[0056] In terms of the sensing signal acquisition mechanism, in addition to electrical parameters such as capacitance, resistance, and impedance, it can also be expanded to detect changes in voltage, current, piezoelectric signals, or field-effect transmission characteristics, further constructing the microneedle array of the present invention into a multimodal sensing platform. The sensing method between the microneedles and electrodes can also be expanded from the current surface contact design to field sensing, electric field modulation, or dielectric modulation structures to meet the needs of new applications such as non-contact sensing and dynamic recognition.

[0057] In addition to its application in electronic skin, the structural design of this invention can also be applied to other intelligent devices requiring adjustable stiffness microstructures and multi-point sensing. For example, it can be used to construct tactile interfaces that mimic human fingers and toes in intelligent prosthetic systems; the end-points of rehabilitation robots can be used to monitor the touch pressure distribution of patients' limbs; surgical navigation gloves can be used to provide real-time output of intraoperative micro-contact feedback; smart mattresses and insoles can be used for posture monitoring and motion recognition; virtual reality tactile feedback devices can provide physical feedback and simulated contact sensation; and it can even serve as a stress-adjustable microstructure support layer for flow field regulation and force field manipulation in micro-nanofluidic chips.

[0058] In addition, in terms of methods and solutions, the present invention is not only applicable to the perception process based on externally applied pressure signals, but can also be changed to pre-set the stiffness of different areas to guide user interaction behavior, and construct functional interfaces such as smart interactive buttons and distributed active response surfaces, thereby forming an integrated perception-interaction-control system.

[0059] First, for material verification, a magnetorheological fluid sample composed of carbonyl iron powder and a silicon-based carrier fluid was prepared, and a microneedle array test sample was fabricated using UV-cured 3D printing. An external controllable electromagnetic coil then provided a magnetic field, and the structural response of the microneedle tips as they deformed under varying magnetic field intensities (0–500 mT) was tested. The results showed that in the absence of a magnetic field, the microneedles were soft and flexible. However, when a magnetic field was applied, the microneedles became stiffer and could penetrate a thin layer of silicone under instantaneous pressure, demonstrating that microneedle stiffness can be effectively adjusted through magnetic control.

[0060] In terms of signal acquisition, flexible metal electrodes are placed under the microneedle array and connected to a precision LCR meter to test the capacitance / impedance change curves under different pressure conditions (50Pa~2kPa). Figure 6 As shown in the experimental results, under the influence of a magnetic field, the sensor sensitivity increased by approximately 2.3 times, the linear response range expanded, and the microneedle structural deformation was stable and repeatable, demonstrating reliable mechanical-to-electrical signal conversion capabilities. Furthermore, to verify the regional adjustability and tactile perception resolution of the present invention, an embedded camera was used to capture deformation information of the surface marking layer. Under the same external force, different microneedle regions exhibited different stiffness responses and signal amplitudes, successfully achieving multi-point, zoned, and differentiated tactile recognition capabilities.

[0061] The simulation used finite element analysis software (ANSYS) to model the mechanical response of a single microneedle under varying magnetic field intensities. The model assumed the microneedle's inner cavity was filled with a magnetorheological fluid, whose modulus adjusted according to changes in magnetic induction intensity. The simulation results were consistent with experimental measurements, demonstrating that the design possesses excellent stress distribution control capabilities under actual operating conditions.

[0062] In order to further verify the importance of filling the microneedle unit cavity with magnetorheological fluid in the present invention, the present invention designed the following comparative example.

[0063] Comparative Example 1

[0064] Comparative Example 1 employed the same flexible microneedle array preparation method and microneedle size parameters as Example 1. The difference was that the internal cavities of the microneedle units in this comparative example were not filled with magnetorheological fluid, forming a hollow structure. In other words, no magnetorheological fluid-filled structure was constructed. The two sample groups maintained consistency in preparation materials, substrate flexible materials, and microneedle dimensions to eliminate contamination from other factors.

[0065] During the test, an external magnetic field (0-500 mT) was applied to the sample of Example 1 (filled with magnetorheological fluid) and the sample of Comparative Example 1 (cavity structure), and the stiffness change, maximum deformation and deformation recovery time of the microneedle array were measured and compared.

[0066] The test results show that the stiffness of the microneedles filled with magnetorheological fluid in the embodiment of the present invention is significantly improved after applying a 500mT magnetic field, which is about 10 times higher than that in the state without a magnetic field, showing excellent magnetic response control characteristics. In contrast, the stiffness of the microneedle array of the sample in Comparative Example 1 changes very little under the same magnetic field conditions. Figure 7 As shown, it can be seen that the stiffness of the microneedle array is only slightly improved, and the maximum deformation and deformation recovery time have basically no obvious changes, which is similar to the performance in the state without magnetic field, and fails to show obvious magnetic response performance.

[0067] These experimental results further demonstrate that if the microneedle unit cavity is not filled with magnetorheological fluid, the microneedle's mechanical properties cannot be effectively controlled under the action of an external magnetic field, and thus the intended magnetic field-controlled flexible adjustment and rapid response functions of the present invention cannot be achieved. Therefore, filling the microneedle unit cavity with magnetorheological fluid is a key element in achieving the technical effects of the present invention and is irreplaceable.

[0068] In summary, the flexible electronic skin structure based on magnetorheological fluid microneedles described in the present invention has undergone experimental prototype construction, material performance testing, electrical signal acquisition evaluation and finite element simulation verification, and has structural feasibility, functional feasibility and performance stability, meeting its application requirements as a new multi-point perception flexible sensing platform, and has the foundation for further productization and system integration.

[0069] The above-described embodiments merely illustrate several implementations of the present invention, and while their descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that a person skilled in the art would be able to make numerous variations and improvements without departing from the spirit of the present invention, all of which fall within the scope of protection of the present invention. Therefore, the scope of protection of the present invention shall be determined by the appended claims.

Claims

1. A flexible electronic skin system, characterized in that: The system constructs a microneedle array filled with magnetorheological fluid on a flexible substrate, and dynamically adjusts the local stiffness and deformation characteristics of the microneedle array under the action of an external magnetic field. A sensing electrode array is integrated under or inside the microneedle array; the microneedle array deforms under the action of force, and the change in distance or contact state with the integrated sensing electrode array is converted into capacitance, resistance or impedance signals, realizing multi-point distributed tactile or pressure perception, and completing real-time acquisition and output through the sensing electrode array and signal processing module.

2. The flexible electronic skin system according to claim 1, characterized in that: The electronic skin system includes a flexible substrate, a plurality of microneedle units, a magnetorheological fluid filling structure, an external magnetic control device, a sensing electrode array, and a signal processing module; wherein: The plurality of microneedle units constitute a microneedle array; the flexible substrate is used to support the entire microneedle array; The microneedle units are distributed on the upper surface of the flexible substrate, and a closed cavity is provided inside each microneedle unit, and the cavity is filled with magnetorheological fluid to form a magnetorheological fluid filling structure; The external magnetic control device is used to apply an external magnetic field to the microneedle unit to adjust the rheological state of the magnetorheological fluid and achieve dynamic and reversible regulation of the microneedle stiffness state; The sensing electrode array is arranged below the microneedle array or embedded in the microneedle structure, and is used to collect changes in resistance, capacitance, impedance, current, piezoelectric signals or field effect transmission characteristics to achieve real-time perception and output of tactile or pressure signals; The signal processing module is connected to the sensor electrode array and is used to collect, analyze, convert and output tactile or pressure sensing signals to a display or control terminal.

3. The flexible electronic skin system according to claim 2, characterized in that: The flexible substrate is made of polydimethylsiloxane.

4. The flexible electronic skin system according to claim 2, characterized in that: Each microneedle unit is a hollow conical structure, a flat columnar structure, a grooved structure or a multi-cavity composite microneedle structure.

5. The flexible electronic skin system according to claim 2, characterized in that: The microneedle material of the microneedle unit includes one of light-curing resin, polyimide, thermoplastic polyurethane, and polycaprolactone flexible polymer materials.

6. The flexible electronic skin system according to claim 2, characterized in that: The sensing mode between the microneedle unit and the sensing electrode array is surface contact, field sensing, electric field modulation or dielectric modulation; the material of the sensing electrode array is selected from silver nanowires, gold nanowires, and liquid metal, and is arranged on the surface of the flexible substrate through a spraying preparation process.

7. The flexible electronic skin system according to claim 6, characterized in that: The regional magnetic fields of the microneedle units can be independently controlled, and the external magnetic control device can achieve differentiated adjustment of the stiffness of microneedles in different areas by arranging electromagnetic coils in different areas to adapt to local tactile perception needs.

8. The flexible electronic skin system according to claim 2, characterized in that: The magnetorheological fluid is composed of carbonyl iron powder and silicon-based carrier liquid; the magnetorheological fluid is in a liquid state under the condition of no magnetic field; when an external magnetic field is applied, its rheological properties change and it turns into a solid-like state.

9. The flexible electronic skin system according to claim 8, characterized in that: The mass ratio of the carbonyl iron powder in the magnetorheological fluid is 35%.

10. The flexible electronic skin system according to claim 2, characterized in that: The magnetic control device adopts an embedded coil, an external permanent magnet or an electromagnetic field system.

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