Stretchable and adhesive microneedle electrodes capable of measuring high-quality electrophysiological signals without skin preparation

Abstract

To provide a stretchable and adhesive microneedle adhesive patch, a stretchable and adhesive microneedle adhesive patch system, and an operation method thereof, capable of measuring a high-quality electrophysiological signal without skin pretreatment such as removal of keratin or sweat.SOLUTION: A stretchable and adhesive microneedle adhesive patch capable of measuring a high-quality electrophysiological signal without skin pretreatment, proposed by the present invention, includes an electrically conductive adhesive (ECA) layer attached to the skin of a user to acquire an electrophysiological signal regardless of the skin condition of the user, a microneedle sensor including a microneedle array passing through the electrically conductive adhesive layer to penetrate the stratum corneum and directly contacting the epidermis of the user to reduce skin contact impedance, and a stretchable interconnect based on a stretchable conductive line electrically and mechanically connected to the microneedle sensor and having a meandering structure to dynamically adapt to the skin deformation of the user.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a stretchable and adhesive microneedle electrode and method of operation that is capable of measuring high quality electrophysiological signals without skin preparation. [Background technology]

[0002] With the increasing elderly population, there is a growing demand for digital healthcare that can accurately monitor one's physical condition and provide appropriate feedback. This has led to a demand for wearable sensors that are easy to install, comfortable to wear for long periods of time, and capable of measuring high-quality electrophysiological signals regardless of skin condition.

[0003] The development of high-quality electrophysiological signal sensor devices is expected to be useful in a variety of industrial fields, as they can be applied to a variety of healthcare applications, such as medical diagnosis, human-machine interfaces, and rehabilitation engineering.

[0004] Wearable electrophysiological signal sensors are used for a variety of purposes (e.g., electrocardiograms, electromyograms, brain conduction measurements, etc.) and are essential elements in human-machine interfaces, digital healthcare, and medical diagnosis. Conventional wearable electrophysiological signal sensors mainly use wet electrodes, which are inexpensive and can acquire signals of appropriate quality. However, problems such as a decrease in signal quality due to the evaporation of the gel over long periods of use have frequently occurred, leading to the development of dry sensors in recent years.

[0005] In order to ensure long-term use without causing a foreign sensation on the skin, the sensor must have a low stiffness similar to that of skin tissue, adequate adhesiveness, breathability, etc. Furthermore, it must have low skin contact impedance to measure high-quality biosignals with a high signal-to-noise ratio.

[0006] Previously widely used wet / dry clinical electrodes were unsuitable for long-term monitoring because signal quality deteriorates as the moisture in the gel decreases and they can even cause allergic skin reactions.

[0007] Recently developed thin-film epidermal electronic devices are dry electrodes that maintain conformal contact according to the curvature of the skin, significantly improving long-term wearability. However, these electrodes have significant variations in signal quality depending on the condition of the skin (e.g., hair, dead skin cells, sweat), and because they often lack self-adhesiveness and adhere to the skin through van der Waals forces, signal acquisition can become unstable during strenuous exercise or sweating.

[0008] To address these shortcomings, flexible microneedle electrodes have been developed that penetrate the stratum corneum of the skin and directly contact the epidermal layer, improving signal quality. However, they are not suitable for long-term comfortable wear due to the large difference in stiffness between the electrode substrate and the skin tissue and the lack of appropriate elasticity and adhesiveness. [Prior art documents] [Patent documents]

[0009] [Patent Document 1] Korean Patent No. 10-1689769 (December 20, 2016) [Patent Document 2] Korean Patent Registration No. 10-1785287 (September 29, 2017) Summary of the Invention [Problem to be solved by the invention]

[0010] The technical problem to be solved by the present invention is to provide a microneedle array sensor with excellent stretchability, adhesiveness, and electrical conductivity, which can measure high-quality bioelectrical signals over a long period of time without skin pretreatment such as removing dead skin cells or sweat, and an operating method thereof. According to an embodiment of the present invention, a stretchable and adhesive wearable microneedle sensor patch can stably measure high-quality bioelectrical signals over a long period of time, regardless of the user's skin condition or movement. [Means for solving the problem]

[0011] In one aspect, the present invention proposes a stretchable and adhesive microneedle adhesive patch capable of measuring high-quality electrophysiological signals without skin pretreatment such as removal of dead skin cells or sweat. The patch comprises an electrically conductive adhesive (ECA) layer that is attached to a user's skin to acquire electrophysiological signals regardless of the user's skin condition, a microneedle sensor including a microneedle array that passes through the electrically conductive adhesive layer, penetrates the stratum corneum, and directly contacts the user's epidermis to reduce skin contact impedance, and an extensible conductive wire-based stretchable interconnect that is electrically and mechanically connected to the microneedle sensor and has a serpentine-like structure to dynamically adapt to the user's skin deformation.

[0012] The electrically conductive adhesive layer enhances the electrical interface between the microneedle sensor and the user's skin by providing an additional electrical conduction path to the user's skin around the microneedle sensor and reducing the skin contact impedance between the microneedle sensor and the user's skin.

[0013] The electrically conductive adhesive layer simultaneously provides electrical conductivity and skin adhesion through the stretchable interconnects based on the extensible conductive wires and the electrically conductive adhesive based on silver flakes and silicone polymer that coats the microneedle sensor, thereby achieving low impedance between the microneedle sensor and the user's skin.

[0014] The microneedle sensor integrates a gold-coated silicone microneedle array beneath a stretchable interconnect on a stretchable conductive wire base, allowing the gold-coated silicone microneedle array to pass through the user's stratum corneum and directly contact the epidermal layer without reaching the nociceptors.

[0015] The microneedle sensor is produced by forming a microneedle array by dicing a portion of a silicon (Si) wafer and isotropic wet etching, evaporating titanium (Ti) and gold (Au), coating an electrically conductive adhesive on the front surface of the gold-coated silicone microneedle array, creating individually isolated microneedles by wet etching while protecting the bottom of the microneedle array with the evaporated gold and wax applied to the sides of the microneedles, integrating the isolated microneedle array with stretchable interconnects based on an extended conductive line having an electrically and mechanically connected serpentine structure using conductive epoxy, and then removing the wax.

[0016] The stretchable interconnection portion of the stretchable conductive wire base is in the form of a stretchable substrate with stretchable conductive wires integrated thereon, and is electrically connected to the microneedle sensor to transmit the acquired electrophysiological signals to a circuit portion for analyzing the electrophysiological signals.

[0017] The stretchable interconnection of the stretchable conductive wire base is formed by integrating stretchable conductive wires on a stretchable substrate, and its serpentine structure allows it to dynamically accommodate the deformation of the user's skin, providing stretchability and comfort for long-term wear.

[0018] The stretchable microneedle adhesive patch provides adhesion through the microneedle sensor and the electrically conductive adhesive layer, which have a stiffness similar to that of the user's skin tissue, and provides stretchability through the stretchable interconnection of the extensible conductive wire base, thereby preventing the stretchable microneedle adhesive patch from peeling off, reducing stress on the user's skin tissue, preventing rashes and irritation, and enabling electrophysiological signals to be measured without deterioration in quality even with long-term attachment.

[0019] In yet another aspect, the present invention proposes a stretchable and adhesive microneedle adhesive patch system capable of measuring high-quality electrophysiological signals without skin pretreatment, comprising: a stretchable microneedle adhesive patch attached to a user's skin and surrounded by a stretchable substrate that acquires electrophysiological signals; a stretchable electronic circuit electrically connected to the stretchable microneedle adhesive patch to receive the acquired electrophysiological signals and to analyze the acquired electrophysiological signals, and surrounded by the stretchable substrate; chip components including a BLE SoC and an amplifier for performing real-time multi-channel electrophysiological signal monitoring of the electrophysiological signals received by the stretchable electronic circuit using a user interface application program; and a modular lithium polymer (LiPo) battery connected to the stretchable electronic circuit by a metal pin connector and providing power for the stretchable microneedle adhesive patch system.

[0020] A metal opening on the lower end surface of the stretchable electronic circuit provides electrical connection to the stretchable microneedle adhesive patch system via an anisotropic conductive film cable and a magnetic connector, allowing for semi-permanent use of the circuit and replacement of the stretchable microneedle adhesive patch.

[0021] The stretchable substrate surrounds the stretchable microneedle adhesive patch and stretchable electronic circuit of the stretchable microneedle adhesive patch system, thereby providing dynamic compliance to bending and stretching during movement of the user's skin tissue during the process of attaching to the user's skin and acquiring electrophysiological signals.

[0022] The chip components, including the BLE SoC and amplifier, utilize Bluetooth®-based wireless communication to support real-time multi-channel electrophysiological signal monitoring using a user interface application program and closed-loop control of the exoskeleton robot by communicating with a control unit. [Effects of the Invention]

[0023] According to embodiments of the present invention, the stretchable and adhesive wearable microneedle sensor patch eliminates the need for skin preparation to reduce electrode skin contact impedance, thereby reducing the time and labor required to install a wearable sensor system and improving productivity. Furthermore, by minimizing the effects of skin conditions and dynamic noise, the patch enables high-quality electrophysiological signal measurement, significantly contributing to human-machine interface applications where high-fidelity biosignal measurement is essential for accurate operation. The patch is capable of stable operation over long periods of time regardless of skin conditions, and its comfortable fit prevents rashes and irritation, making it suitable for wearable digital healthcare technologies that require high-quality wearability. [Brief explanation of the drawings]

[0024] [Figure 1] FIG. 1 is a diagram illustrating the configuration of a stretchable microneedle adhesive patch (SNAP) in one embodiment of the present invention. [Figures 2a-2c] FIG. 1 illustrates the main mechanical features of the SNAP for reliable wearable EP signal monitoring in one embodiment of the present invention. [Figure 3] FIG. 1 is a diagram illustrating the manufacturing process and materials of SNAP in one embodiment of the present invention. [Figures 4a-4h] FIG. 1 illustrates the configuration and mechanical properties of a stretchable, adhesive microneedle sensor in accordance with one embodiment of the present invention. [Figure 5] 1 is an equivalent circuit illustrating the electrical characteristics of a SNAP attached to the skin in one embodiment of the present invention. [Figures 6a-6i] FIG. 2 is a diagram illustrating the electrical characteristics of a SNAP attached to the skin in one embodiment of the present invention. [Figure 7] 1 is a diagram showing the configuration of a wireless SNAP system according to an embodiment of the present invention. [Figure 8] FIG. 1 illustrates the mechanical durability of a wireless SNAP system in accordance with one embodiment of the present invention. [Figure 9] 1 is a flowchart illustrating a method of operation of a wireless SNAP system in accordance with an embodiment of the present invention. [Figure 10] 1A-1C are diagrams illustrating EMG monitoring performance of a wireless SNAP system during various walking movements in accordance with an embodiment of the present invention. [Figure 11] 10 is a graph illustrating EMG signal quality for a wireless SNAP system in accordance with an embodiment of the present invention. [Figures 12a-12d] 10 is a diagram showing experimental results of a wireless SNAP system as an HMI according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0025] Highly accurate and convenient recording of electrophysiological (EP) signals is essential for healthcare and human-machine interfaces (HMIs). Microneedle electrodes directly contact the epidermis, eliminating the need for tedious skin preparation and enabling instant setup. However, conventional microneedle electrodes lack the stretchability and reliability required for a strong skin interface, making it difficult to detect high-quality EP signals over long periods of time during physical activity. Here, we propose a stretchable microneedle adhesive patch (SNAP) that provides excellent skin penetration and a robust electromechanical skin interface for long-term, reliable EP monitoring under diverse skin conditions. According to an embodiment of the present invention, the SNAP significantly reduces skin contact impedance even under skin contamination, improving wearing comfort during activity and outperforming gel and flexible microneedle electrodes. A demonstration of the wireless SNAP for controlling an exoskeleton robot confirmed its potential for reliable HMIs, even with time-dynamic skin conditions. The SNAP according to the embodiment of the present invention is expected to provide versatility for wearable EP detection and practical application programs of HMI. Hereinafter, the embodiment of the present invention will be described in detail with reference to the accompanying drawings.

[0026] Reliable and accurate recording of electrophysiological (EP) signals from the skin is a key issue in clinical diagnosis, rehabilitation, and human-machine interfaces (HMIs). An EP sensor that requires no preparation process and maintains excellent recording quality over long periods of time, regardless of skin condition, would have practical impact on a variety of wearable real-world applications. Traditionally, medical metal electrodes, together with conductive gels or hydrogels, have been widely used to achieve cost-effective and satisfactory EP detection. However, these electrodes require preparation steps, such as applying gel and disinfecting the skin with alcohol swabs. Over time, the gel may dry out, resulting in signal loss. Furthermore, the smooth interface of the gel can generate dynamic noise. Furthermore, the conductive gel can cause skin allergies and irritation, limiting the long-term use of the electrodes.

[0027] To overcome these limitations, advances in materials and microfabrication technologies have led to the development of flexible dry-skin electrodes that are convenient, do not require conductive gel, and provide long-term EP signal monitoring. Despite this, when these dry electrodes are attached to the skin surface without skin preparation such as hair removal or exfoliation, they tend to exhibit high and unstable skin contact impedance due to factors such as hair, keratin, and skin secretions. Furthermore, epidermal electrodes, which maintain contact with the skin solely through van der Waals forces, can result in unstable electrode-skin interfaces during sweating or strenuous activity. In some cases, tattoo-like electrodes require additional equipment, such as stencil masks or spray printers, to attach the devices, hindering their convenience.

[0028] Microneedle electrodes offer a solution to address the vulnerability of electrophysiological (EP) sensors to skin conditions. Microneedle electrodes provide a stable electrical interface without the need for skin preparation and can access the epidermis layer via microneedle penetration. Previously, flexible microneedle electrodes (FMEs) constructed on polymer substrates such as polyimide (PI), polystyrene, and parylene were developed. However, while these FMEs are biocompatible, their mechanical incompatibility with skin tissue can lead to interface defects and discomfort during long-term wear. Recently, the development of stretchable microneedle electrodes using a polydimethylsiloxane (PDMS) substrate has alleviated some of the issues of substrate incompatibility. However, these electrodes have difficulty adapting to changes in skin tissue due to their higher elastic modulus than skin tissue and poor adhesion to the skin surface. Furthermore, the EP signal recording performance of conventional stretchable microneedle electrodes has been little studied due to the difficulty of electrical connection and the lack of electrical reliability during mechanical stretching.

[0029] This invention proposes a stretchable microneedle adhesive patch (SNAP) as a solution for long-term EP signal monitoring, regardless of skin condition, with high reliability and without the need for skin preparation. The SNAP's stretchable platform, composed of serpentine interconnects, accommodates dynamic changes in skin tissue and enhances comfort during long-term wear. By integrating a silicone (Si) microneedle array under the stretchable interconnect, it penetrates the stratum corneum and makes direct contact with the epidermis without reaching nociceptors. This allows for painless, easy acquisition of high-quality EP signals without the need for skin preparation. Furthermore, an electrically conductive adhesive (ECA) consisting of silver (Ag) particles and high-tack silicone provides an additional conductive path, enhancing the electrode-skin interface while still allowing for safe attachment to the skin during use. A series of studies comprehensively investigated the physical, mechanical, and electrical properties of the SNAP and confirmed its high reliability in a variety of conditions. Finite element analysis (FEA) results and experimental comparisons with other EP sensors (e.g., FMEs and gel electrodes) demonstrated that SNAP significantly reduced tissue stress during skin deformation and exhibited superior performance due to its elastic and permeable properties, which enhanced the signal-to-noise ratio (SNR). A proof-of-concept demonstration in closed-loop operation of an exoskeleton robot highlighted the reliability of the wireless SNAP system, which requires no skin preparation, and demonstrated its potential for HMI application programming, allowing users to move quickly and freely. In this study, SNAP is expected to have a significant impact on diverse applications requiring reliable EP detection, such as continuous health monitoring, neuroscience research, and wearable HMIs.

[0030] FIG. 1 is a diagram illustrating the configuration of a stretchable microneedle adhesive patch (SNAP) in one embodiment of the present invention.

[0031] A patch-type device incorporating a SNAP according to one embodiment of the present invention allows stable and long-term EP signal monitoring regardless of skin conditions. Figure 1 shows a close-up of a flexible, tissue-adaptable SNAP that penetrates the stratum corneum using microneedles (Au / Si microneedles) to directly contact the epidermis.

[0032] SNAPs according to embodiments of the present invention are engineered to have softness, adhesive properties, and tissue conformability, ensuring stable and reliable recording of EP signals over long periods of time.

[0033] 1, a stretchable microneedle adhesive patch (SNAP) according to one embodiment of the present invention includes stretchable conductive line-based stretchable interconnects 110, a microneedle sensor (Au / Si microneedle) 120 consisting of an Au-coated Si microneedle array, and an electrically conductive adhesive (ECA) 130 made of Ag flakes and silicone polymer. The Ag flakes can be replaced with other electrically conductive fillers such as carbon nanotubes, graphene, carbon black, silver nanowires, and liquid metals.

[0034] The SNAP according to one embodiment of the present invention can stably measure high-quality biosignals over a long period of time, regardless of the user's skin condition or movements.

[0035] In accordance with one embodiment of the present invention, the stretchable conductive line-based stretchable interconnect (i.e., stretchable substrate) 110 is designed in a serpentine shape (e.g., a 5 μm / 200 nm / 5 μm PI / Au / PI structure) and serves as the electrical and mechanical foundation for the microneedle array.

[0036] This serpentine design provides the SNAP with overall elasticity, allowing it to dynamically adapt to skin deformation. Strong Si microneedles (e.g., with an elastic modulus of 130 GPa) 120 integrated under the serpentine stretchable interconnect 110 easily penetrate the stratum corneum and reach the epidermis. This structure reduces contact impedance and improves electrode performance. Microneedles according to embodiments of the present invention are designed to be 200 μm high and have a tip diameter of less than 5 μm, ensuring painless insertion because nociceptors within the skin are located 200 μm below the skin surface.

[0037] The ECA (e.g., 45 μm thick) 130 around the microneedles according to embodiments of the present invention provides an additional electrical conduction path to the skin, enhancing the electrical interface between the electrode and the skin. The ECA 130 according to embodiments of the present invention is composed of a high-tack silver flake-silicone polymer, providing strong adhesion to the skin. The silver flakes can be replaced with other conductive fillers, such as carbon nanotubes, graphene, carbon black, silver nanowires, and liquid metals.

[0038] FIG. 2 illustrates the main mechanical features of the SNAP for reliable wearable EP signal monitoring in one embodiment of the present invention.

[0039] FIG. 2(a) is a diagram illustrating the features of SNAP for adapting the stretching of skin tissue.

[0040] Referring to Figure 2(a), the softness and stretchability of SNAP allows it to accept dynamic deformation of the skin with minimal mechanical stress, forming a strong interface between the microneedles and the skin.

[0041] Figure 2(b) is a graph showing the relative resistance change of the SNAP as a function of tensile strain. The SNAP, according to an embodiment of the present invention, exhibits negligible resistance change when subjected to a 30% stretch, which corresponds to the maximum stretch range of human skin. This highlights its ability to maintain stable electrical measurements under tensile strain.

[0042] Figure 2(c) shows optical images demonstrating the high mechanical compliance of SNAP in its original state 211, 30% stretched state 212, and 10% stretched state with 180° twist 213, respectively, along with finite element modeling of SNAP for each deformed configuration.

[0043] Experimental and FEA simulation results (see FIG. 2) according to embodiments of the present invention showed that SNAP stretches with negligible relative conductivity change (<5%; (FIG. 2(b)) when subjected to the maximum tensile deformation range of human skin (approximately 30%), and only 1.8% maximum principal deformation of the gold material (see FIG. 2(c) 212, where the bending deformation of Au is approximately 2%). Notably, most trace regions exhibited significantly lower deformation rates (<0.5%) compared to the maximum deformation. Furthermore, even at high deformations (e.g., 180° twist and 10° twist), the SNAP stretches with only 1.8% maximum principal deformation of the gold material (see FIG. 2(c) 212). % stretching), providing high mechanical durability, with the gold material undergoing only a 0.097% major deformation (see Figure 2(c)213). These results confirm that SNAP exhibits excellent electrical and mechanical reliability, even at deformation levels exceeding the typical durability limits of human skin (10-20%). Overall, the design integrating the microneedle array with tissue-adaptable elastic electrodes can provide comfortable and highly reliable EP signal monitoring with minimized interference across a variety of skin conditions.

[0044] FIG. 3 is a diagram illustrating the manufacturing process and materials of SNAP in one embodiment of the present invention.

[0045] Figure 3 illustrates the fabrication steps for integrating a rigid microneedle array onto a stretchable electrode. First, the microneedle array is formed by partial dicing and isotropic wet etching of a silicon (Si) wafer, followed by titanium (Ti) / gold (Au) (20 / 200 nm) deposition (310). After this, an uncured, low-viscosity electrically conductive adhesive (ECA) is applied to the front of the Au-coated Si microneedle array (320). Next, while the bottom of the Si microneedle array is protected by a laminated Au layer and wax applied to the microneedle sides, wet etching is performed to create individual, isolated microneedles (330). Finally, the isolated microneedle array is integrated into electrically and mechanically connected serpentine interconnects using conductive epoxy (340), and the resulting structure is completed by removing the wax (350).

[0046] FIG. 4 is a diagram illustrating the configuration and mechanical properties of a stretchable and adhesive microneedle sensor according to one embodiment of the present invention.

[0047] The stretchable interconnection portion (i.e., stretchable substrate) of the stretchable conductive wire base according to an embodiment of the present invention is a low-stiffness silicone elastomer having stretchable conductive wires integrated therein, and can freely adapt to dynamic deformation of the skin and electrically connect to the microneedle array to transmit electrophysiological signals to the circuit portion. Here, the low-stiffness silicone elastomer is merely an example, and various other stretchable substrates may be used.

[0048] According to an embodiment of the present invention, a microneedle sensor consisting of an Au-coated Si microneedle array is electrically and mechanically connected to a stretchable interconnect, penetrating the highly resistive stratum corneum of the skin to directly contact the epidermis layer, effectively reducing skin contact impedance. The silver flake-silicone polymer-based electrically conductive adhesive coating the stretchable interconnect and microneedle array provides both high electrical conductivity and skin adhesion, resulting in a robust electrode-skin impedance.

[0049] Figure 4(a) shows an optical image of the completed stretchable and adhesive microneedle sensor (scale bar, 5 mm). The image on the right shows the completed SNAP, which consists of a stretchable serpentine interconnect (top image, backside of the device) and an ECA-layer-coated microneedle array (bottom image, front side of the device). The key factors for achieving high-quality skin signal recording are epidermal accessibility and electrical and mechanical interface with the skin.

[0050] FIG. 4(b) is a scanning electron microscope (SEM) image of a single microneedle showing the Au-coated tip protruding from the ECA layer in an embodiment of the present invention (scale bar, 50 μm).

[0051] SNAP ensures direct, biocompatible contact from the protruding gold-coated microneedle tips to the epidermis, while maintaining strong adhesion, high stretchability, and low contact impedance through an ECA layer. This ECA layer is a polymer composite consisting of surface-modified silver particles and an optimized ratio of highly adhesive silicone (Silbione (5 kPa):Ecoflex GEL (33 kPa) = 1:3 (Silbione RT Gel 4717, Bluestar Silicones; Ecoflex GEL, Smooth-On Inc. (53-55))). Silbione enhances ECA adhesion, while Ecoflex GEL enhances tensile strength.

[0052] The top of Figure 4(c) is an SEM image of an ECA layer showing a mixture of Ag flakes and silicone gel (Silbione:Ecoflex GEL = 1:3) according to an embodiment of the present invention (scale bar, 10 μm). The bottom of Figure 4(c) shows Ag flakes with a roughened surface according to an embodiment of the present invention (scale bar, 1 μm).

[0053] The surface-modified Ag particles play an important role in enhancing the electrical conductivity of ECA. The iodination process roughens the Ag particle surface, forming Ag / AgI nanoislands and exposing the silver. This promotes sintering between Ag particles, increasing the intrinsic conductivity of ECA. Furthermore, the two-dimensionally surface-modified Ag particle morphology enhances the stretching stability of ECA by stacking adjacent particles in parallel along the substrate plane during the curing of the low-viscosity electrically conductive polymer. Therefore, the mutual distance between adjacent particles is maintained within a certain range, providing a reliable electrical conduction path that is not sensitive to stretching. This indicates that the relative conductivity of ECA changes little when subjected to the maximum allowable tensile deformation, which corresponds to the maximum allowable stretching of human skin.

[0054] Figure 4(d) is a graph comparing the cell viability of a control group (without SNAP) and an experimental group (immersed in SNAP) cultured in cell culture medium on day 3 according to an embodiment of the present invention. The image on the right shows live / dead staining of 3T3 cells after 3 days of culture for the SNAP-immersed group (i) and the control group (ii) (scale bar, 100 μm).

[0055] Referring to Figure 4(d), the experimental results demonstrated the skin biocompatibility of the SNAP and confirmed that no unnecessary damage occurred during long-term use of the SNAP according to an embodiment of the present invention. To evaluate the biocompatibility of the SNAP, a cytotoxicity experiment was conducted with 3T3 cells (a mouse embryonic fibroblast cell line). In this experiment, the SNAP was completely immersed in cell culture medium and cultured with the 3T3 cells. The cells cultured in the cell culture medium completely immersed in the SNAP showed comparable cell viability to the control group using complete cell culture medium for 3 and 7 days. Fluorescent live / dead staining clearly showed no difference between the control group and the SNAP-immersed group, demonstrating the excellent biocompatibility of the SNAP. In addition to the device's biocompatibility, another important aspect to consider is ensuring sufficient breathability to provide comfortable, non-irritating wearability while maintaining stable EP signal measurement performance. Based on the permeability test according to the ASTM E96-95 standard, SNAP showed excellent water vapor permeability, which was within the range of skin water permeability observed in human skin (5-10 g hour-1 m-2), reaffirming the skin breathability of SNAP.

[0056] Figure 4(e) shows an optical image of human skin stained with blue dye coated onto a microneedle array in accordance with an embodiment of the present invention, and illustrates the experimental setup for skin penetration by SNAP (scale bar, 1 cm).

[0057] One of the key design requirements for SNAPs according to embodiments of the present invention is to achieve uniform skin penetration with low penetration forces despite the soft substrate.

[0058] FIG. 4(f) is a graph comparing the skin penetration power of FME and SNAP in an embodiment of the present invention.

[0059] Referring to Figure 4(f), SNAP demonstrated the ability to penetrate human skin with an insertion force comparable to that of conventional FMEs based on a PI substrate common to human skin. The insertion force obtained by SNAP (≒4.8 N) was clearly lower than the force required to press an elevator button or stick a postage stamp (≒20 N). Furthermore, the required insertion force decreased with increasing loading speed. These results suggest that SNAP can easily impart strong skin penetration to skin with minimal force, even with strong finger pressure.

[0060] Figure 4(g) is an optical image of a SNAP attached to skin, intentionally partially separated using tweezers, to show that the device is firmly adhered to the skin, in accordance with an embodiment of the present invention.

[0061] FIG. 4(h) is a graph showing the skin adhesion strength of a SNAP according to an embodiment of the present invention compared to commercially available medical films and silicone adhesives (e.g., Silbione, 20:1 PDMS) according to an embodiment of the present invention.

[0062] After rapid application, SNAP according to embodiments of the present invention provides strong adhesion through the adhesive ECA layer, ensuring a stable device interface to the skin (0.24 N / cm), which is within the typical adhesion range of commercially available medical adhesive tapes (0.16-1.2 N / cm). Overall, the biocompatibility, breathability, and mechanical properties of SNAP demonstrate its ability to maintain excellent device-skin contact while providing a comfortable and skin-friendly interface for the user.

[0063] FIG. 5 is an equivalent circuit illustrating the electrical characteristics of a SNAP attached to the skin in one embodiment of the present invention.

[0064] Figure 5 shows schematic diagrams of the electrode-skin interface for various types of electrodes along with the corresponding equivalent circuit models: Figure 5(a) shows the gel electrode, Figure 5(b) shows the ECA electrode, Figure 5(c) shows the FME, and Figure 5(d) shows the SNAP electrode-skin interface and their respective equivalent circuits.

[0065] FME is produced by sputtering Ti / Au (20 / 200 nm thick) onto a PI-based microneedle electrode, but unlike SNAP, it does not contain an ECA layer. Unlike surface electrodes, microneedle electrodes (FME and SNAP) generate a double layer charge (C d ) and charge transfer resistance (R d ) effect. This is due to the high resistance of the epidermal layer (>10 5 This is achieved by direct access to the epidermis via the ohm.

[0066] FIG. 6 is a diagram illustrating the electrical characteristics of a SNAP attached to the skin in one embodiment of the present invention.

[0067] Referring to Figure 6(a), a plot of electrode-skin contact impedance as a function of frequency is shown. The skin is prepared by cleaning with water-moistened gauze and then cleaning again with an alcohol swab for disinfection.

[0068] Figure 6(b) shows optical images illustrating various skin conditions, including sweat, dead skin cells, hair, and dirty skin, and Figure 6(c) shows the standard deviation of the skin contact impedance measured with various EP sensors under these various skin conditions.

[0069] In the case of SNAP, the ECA layer surrounding the microneedle array reduces contact impedance, further enhancing the electrode-tissue interface. Specifically, at 100 Hz, SNAP reduces contact impedance by 25% compared to FME (Figure 6(a)). SNAP also exhibits low and consistent skin contact impedance regardless of skin condition (21 ± 5 kΩ cm at 100 Hz). 2 Mean ± standard deviation), maintaining a stable skin contact impedance compared to other electrode types (Figure 6(a) and Figure 6(c)). In multiple sample tests (n=5), the direct epidermal approach provided by SNAP resulted in a stable and significantly lower standard deviation of skin contact impedance (σSNAP and σFME ~5 kΩ cm). 2 ) which is the epidermal contact impedance of conventional gel and ECA electrodes (σ gel and σ ECA ~ 150 kohm cm 2 ) (Figure 6(c)). These features enable SNAP to provide superior electrical performance, eliminating the need for skin preparation such as hair removal or exfoliation.

[0070] Figure 6(d) shows a visual comparison of the mechanical compliance between the SNAP and FME attached to the skin when the skin is compressed and stretched.

[0071] The elastic properties of SNAP allow for stable and consistent skin contact in response to dynamic skin deformation, allowing SNAP to adapt to dynamic skin deformation and maintain stable contact. On the other hand, FMEs are prone to peeling off from the skin due to mechanical mismatch at the device-skin interface.

[0072] The stretchable and adhesive microneedle electrodes according to embodiments of the present invention have a stiffness modulus similar to that of skin tissue (e.g., 60-850 kPa) and excellent stretchability (>50%), allowing them to dynamically adapt to the stretching of the skin and prevent the electrodes from peeling off (Figure 6(d)).

[0073] The FEA results in Figure 6(e) showed significantly less stress in the tissue around the SNAP (0.22 MPa) compared to the FME (0.57 MPa), confirming that the SNAP can adapt to tissue deformation and minimize tissue damage during dynamic motion.

[0074] Furthermore, the excellent elasticity and adaptability of this device reduced the stress on the skin tissue compared to conventional non-elastic, flexible microneedle electrodes, preventing rashes and irritation (Figure 6(e)). It was also possible to measure electrophysiological signals without any degradation in quality even after wearing the device for more than 7 days.

[0075] Figure 6(f) shows the measured skin contact impedance of SNAP and FME under various tensile deformation rates. The experimental results of skin contact impedance under skin deformation showed that the adaptation of SNAP and dense tissue interface reduced the possibility of physical gaps between the electrode and the skin, contributing to maintaining a stable skin contact impedance (an increase in contact impedance of <5 kΩ cm at 30% applied deformation). 2 ).

[0076] Figure 6(g) is a graph comparing the baseline noise levels of EMG signals measured using SNAP and FME during cyclic stretch and release.

[0077] To ensure the electrical performance and mechanical compatibility of the SNAP for long-term use, we monitored the EMG baseline noise while repeatedly subjecting the electrodes to cyclic deformation while they were attached to the skin. Figure 6(g) shows that the SNAP maintains consistent EMG baseline noise even after 100 repeated 30% stretches and compressions at the site where the SNAP was attached. This confirms the strong interface of the SNAP with the skin during dynamic movement.

[0078] Figure 6(h) shows optical images of the skin surface after cyclic stretching (left side after 50 cycles, right side after 150 cycles) using SNAP and FME.

[0079] When the skin was stretched 30% repeatedly 150 times, the SNAP skin-tissue interface did not develop a significant red rash, in contrast to the skin interface to which FME was applied under the same conditions (Figure 6(h)).

[0080] Figure 6(i) is a graph comparing the baseline noise levels of resting EMG signals measured over an 8-day period using SNAP, ECA, and commercially available gel electrodes.

[0081] To evaluate the long-term wearability of the SNAP, we attached it to an arm muscle (target muscle: flexor carpi radialis) and monitored changes in EMG baseline noise over an 8-day period. These results were compared with those using ECA electrodes and commercially available gel electrodes (TYH-WF25RP, Skyforever). Over the 8-day measurement period, the output signals from the SNAP and ECA electrodes were stable, with baseline noise values ​​remaining largely unchanged (<10%). In contrast, the commercially available gel electrodes showed a significant increase in baseline noise due to electrode drying (a 69% increase from days 1 to 8). While we recommend skin preparation using water or alcohol wipes before initial application of the SNAP, these results collectively demonstrate the SNAP's ability to enable robust, long-term monitoring of EP signals regardless of skin condition or deformation.

[0082] FIG. 7 is a diagram showing the configuration of a wireless SNAP system according to one embodiment of the present invention.

[0083] A wireless SNAP system according to an embodiment of the present invention includes a SNAP 710 surrounded by a silicone elastomer 720, a stretchable circuit 730 surrounded by the silicone elastomer 720, a chip component (e.g., a BLE SoC, an amplifier, etc.) 740, and a modular battery 750. Note that the low stiffness silicone elastomer is merely an example, and various other stretchable substrates may be used.

[0084] The wireless SNAP system according to an embodiment of the present invention acquires EP signals by attaching a SNAP 710 surrounded by a silicone elastomer 720 to the user's skin. The acquired EP signals are transmitted to a stretchable electronic circuit 730 surrounded by the silicone elastomer 720. The EP signals received by the stretchable electronic circuit 730 are then monitored in real time by a BLE SoC 740 using a user interface application program.

[0085] 7 illustrates a wireless SNAP system that integrates SNAP with a stretchable wireless EP signal processing circuit 730 to enable stable EMG detection during a user's dynamic movements. The flexible nature of the wireless SNAP system allows for stable EP signal recording in targeted curvilinear muscle regions, such as the upper and lower limbs. Additionally, the device's wireless functionality eliminates the need for the inconvenient wired setup of conventional devices.

[0086] In SNAP devices according to embodiments of the present invention, the serpentine structure of the interconnect (e.g., 50 μm / 36 μm / 50 μm PI / Cu / PI structure) along with integrated components 740 including a BLE SoC and amplifier chip enable the device's stretchability. The BLE SoC facilitates wireless communication with portable electronic devices (e.g., smartphones) and allows real-time multi-channel EP signal monitoring via a user-friendly interface application program. To ensure optimal comfort and practicality, the wireless SNAP system is surrounded by a silicone elastomer capsule (e.g., 750 μm thick; 69 kPa; Ecoflex 00-30) 720, providing skin-like softness and high compliance during tissue movement (e.g., bending and stretching). Power for devices according to embodiments of the present invention is provided by a modular lithium polymer (LiPo) battery 750, which connects to the wireless SNAP system's stretchable electronics 730 via a metal pin connector. Here, the modular lithium polymer battery is merely an example, and various other small batteries such as coin cell batteries and other types of lithium batteries may be used.

[0087] Additionally, a metal opening on the bottom surface of the stretchable electronic circuit 730 of the wireless SNAP system provides electrical connection to the SNAP via an anisotropic conductive film cable and magnetic connector, allowing for semi-permanent use of the circuit and easy replacement of the SNAP.

[0088] FIG. 8 illustrates the mechanical durability of a wireless SNAP system in accordance with one embodiment of the present invention.

[0089] Figure 8 shows photographs of the device taken during stretching (ε=30%) 810 and torsion (90° twist) 820. Figure 8 shows actual images of the completed wireless SNAP system, demonstrating the mechanical compliance of the SNAP system during dynamic deformation.

[0090] FIG. 9 is a flowchart illustrating a method of operation of a wireless SNAP system in accordance with an embodiment of the present invention.

[0091] A method of operating a wireless SNAP system according to one embodiment of the present invention includes step 910 of acquiring electrophysiological signals by attaching a stretchable microneedle adhesive patch surrounded by a silicone elastomer to a user's skin, step 920 of transmitting the acquired electrophysiological signals to a stretchable electronic circuit electrically connected to the elastic microneedle adhesive patch and surrounded by a silicone elastomer for analysis, and step 930 of performing real-time multi-channel electrophysiological signal monitoring of the electrophysiological signals received by the stretchable electronic circuit using a user interface application program by chip components including a BLE SoC and an amplifier.

[0092] According to one embodiment of the present invention, power for the stretchable microneedle adhesive patch system is provided by a modular lithium polymer (LiPo) battery connected to the stretchable electronic circuitry via a metal pin connector.

[0093] According to one embodiment of the present invention, a metal opening on the lower end surface of the stretchable electronic circuit provides electrical connection to the stretchable microneedle adhesive patch system via an anisotropic conductive film cable and a magnetic connector, allowing for semi-permanent use of the circuit and replacement of the stretchable microneedle adhesive patch.

[0094] According to one embodiment of the present invention, the stretchable microneedle adhesive patch and stretchable electronic circuit of the stretchable microneedle adhesive patch system are surrounded by a silicone elastomer, thereby providing dynamic compliance to bending and stretching during movement of the user's skin tissue during the process of attaching the system to the user's skin and acquiring electrophysiological signals.

[0095] According to one embodiment of the present invention, the chip components including the BLE SoC and amplifier can support closed-loop control of an exoskeleton robot by using Bluetooth®-based wireless communication to monitor multi-channel electrophysiological signals in real time using a user interface application program and communicating with a control unit.

[0096] FIG. 10 illustrates the EMG monitoring performance of the wireless SNAP system during various walking movements in accordance with an embodiment of the present invention.

[0097] The FEA simulations presented in Figure 10 confirm the ability of the wireless SNAP system to maintain the maximum major deformation rate of the Cu interconnect traces (3.3%) below the fracture limit (fracture deformation rate of Cu ≈ 5%) in all regions where the component deforms. It is noteworthy that most regions exhibited significantly lower deformation rates (<0.3%) relative to the maximum deformation rate. This confirms the wireless SNAP system's ability to maintain structural integrity during operation.

[0098] To evaluate the potential utility of EP recording with the wireless SNAP system during high-intensity physical activity, we attached a device to a human thigh muscle (target muscle: Vastus medialis) to monitor EMG signals during exercise. To simulate the dynamic conditions caused by skin deformation and sebum secretion during exercise, oil and baby powder were applied to the EP signal monitoring site. We then compared measurements obtained from the wireless device with those obtained from a conventional wireless device integrated with gel electrodes.

[0099] FIG. 10 illustrates EMG measurements taken during outdoor exercise, including various locomotion activities such as walking 1010, running 1020, jumping 1030, and squatting 1040. During mild physical activity such as walking 1010, the effects of motion artifacts were not evident, and no significant differences were observed between EMG signals measured with the SNAP and gel electrodes. However, during vigorous exercise such as running 1020 and jumping 1030, leg movements result in significant acceleration, shaking, and tissue deformation in the attached wireless device (integrated with the SNAP and gel electrodes). The running 1020 and jumping 1030 measurements confirmed that the wireless SNAP system caused minimal reference orientation and motion artifacts during running or jumping, while the gel electrode system caused significant fluctuations in the EMG signal.

[0100] FIG. 11 is a graph illustrating EMG signal quality for a wireless SNAP system in accordance with one embodiment of the present invention.

[0101] Figure 11(a) shows the baseline noise amplitude for the pretreated and contaminated skin conditions, Figure 11(b) shows the SNR values, and Figure 11(c) shows the EMG signal quality graphs recording the baseline noise amplitude for the four types of walking movements.

[0102] The EMG signal quality of the wireless SNAP system according to embodiments of the present invention demonstrated high performance regardless of skin condition, due to significant reductions in baseline noise (47% reduction compared to gel electrodes and 73% reduction compared to ECA electrodes), demonstrating its ability to overcome skin contamination. This trend was consistent not only for EMG but also for other EP signals, such as EEG, where the signal size is significantly smaller. This demonstrates the wireless SNAP system's ability to provide high-quality EP signal measurements during dynamic motion, suggesting potential applications in healthcare, athletic training, musculoskeletal rehabilitation, HMI, and more.

[0103] FIG. 12 is a diagram showing experimental results using a wireless SNAP system as an HMI in one embodiment of the present invention.

[0104] EMG-based exoskeleton robot technology according to embodiments of the present invention offers the advantage of rapid recognition of user movements, operating 30-100 ms faster than conventional kinematic-based exoskeleton robots. It also enables integration of user input and feedback through neuromuscular coupling. However, signal instability due to user movements and skin secretions presents challenges in practical application of EMG-based assistive robot control. Furthermore, cumbersome wired sensor systems require extensive setup time, limit the user's natural range of motion, and limit the application of exoskeleton robots to laboratory environments.

[0105] In an embodiment of the present invention, we propose an exoskeleton robot control using a low-profile wireless SNAP system that operates out of the box for applications in intelligent neural network assistance, physical movement assistance, and other HMI fields.

[0106] In an embodiment of the present invention, the SNAP system is used to demonstrate wireless EMG-triggered closed-loop control of a back-assist robot used in lifting loads. Referring to Figures 12(a) and (b), the robot assistance strategy and system configuration using the wireless SNAP system are shown.

[0107] Figure 12(a) shows the system architecture and control strategy of the exoskeleton robot. The SNAP system attached to the lower limb muscles wirelessly transmits EMG signals to the exoskeleton robot controller to stimulate assistive movements. Another SNAP system attached to the back muscles monitors muscle activity to evaluate the robot's assistive performance.

[0108] Figure 12(b) shows the hardware configuration of the pneumatic backpack exoskeleton system. The linear movement of the pneumatic cylinders allowed the device to push the trunk, generating auxiliary hip torque to lift heavy external loads.

[0109] FIG. 12(c) shows real-time measurements of TKEO-EMG signals from trigger muscles during a single cycle of squat lifting (squat) and stoop lifting (stoop).

[0110] Referring to Figure 12(a), EMG signals are monitored by a SNAP system attached to the lower limb muscles (target muscles: GM (Gluteus Maximus) for squat lifting, BF (Biceps femoris) for stoop lifting), and the assistive robot is activated when this signal exceeds a preset threshold.

[0111] The SNAP system provides a powerful sensing interface during dynamic HMI tasks, offering greater resistance to sweating and skin deformation than typical gel electrodes (1210). The collected EMG signals are sent to a finite state machine in the microcontroller unit and rectified by a Teager-Kaiser Energy Operator (TKEO), which determines the current state of the exoskeleton robot and determines whether it is in assist mode (1211). This process generates a corresponding torque profile (1212). The assist torque is transmitted to the user's hip joint by a closed-loop pneumatic controller, which uses the desired air pressure obtained from an actuator inverse model (1213). This assistance strategy reduces muscle overuse and fatigue resulting from repetitive lifting of heavy loads, preventing musculoskeletal injuries. Furthermore, an additional wireless SNAP system is attached to the back muscles where the target muscles are located. This system communicates with a smartphone and analyzes the reduction in RMS EMG to evaluate the exoskeleton robot's performance (1220).

[0112] Figure 12(c) provides a proof-of-concept demonstration proving the assistive capabilities of the exoskeleton robot integrated with closed-loop control using the wireless SNAP system, showing it lifting a 10 kg load. This experiment was conducted in both prepared and unprepared sweating skin conditions to evaluate the performance of the SNAP system in a situation that does not require prior preparation.

[0113] Figure 12(d) is a graph comparing the RMS EMG with and without robot assistance.

[0114] The RMS EMG results measured in the L1 muscle showed a significant decrease in muscle activation compared to without robotic assistance (on average, 18.1% decrease in the prepared and unprepared sweating skin conditions, respectively). These results demonstrate that the SNAP system effectively overcomes the challenges of unstable EMG recordings due to user movement and skin secretions, resolving issues that have hindered traditional EMG-based exoskeleton robot control. Furthermore, the exoskeleton robot equipped with the SNAP system had a positive effect on muscle fatigue, highlighting its potential to enhance the functional mobility of individuals who require assistance with lifting heavy loads. In summary, integrating a preparation-free wireless EP signal monitoring system into an assistive exoskeleton robot represents a promising solution in the field of wireless assistive device control, particularly contributing to physical human augmentation in the field of wireless assistive systems.

[0115] In this way, the SNAP according to the embodiment of the present invention is applicable to healthcare applications that stably measure and analyze human electrophysiological signals over a long period of time and provide feedback.

[0116] In addition, the SNAP according to the embodiment of the present invention can be applied to human-machine interfaces to minimize noise caused by the user's skin condition and movements, and is ideal for applications that require accurate signal acquisition and movement recognition functions.

[0117] Furthermore, the SNAP according to the embodiment of the present invention does not cause skin irritation even with long-term use, and can be used for various transdermal treatments such as electrical stimulation.

[0118] Furthermore, the SNAP according to an embodiment of the present invention can be applied not only to wearable devices but also to measuring and stimulating various bioimplant multi-channel electrical signals such as cerebral cortical conduction and nerve conduction, and can be used in bioimplantable devices.

[0119] The SNAP according to the embodiment of the present invention can measure high-quality electrophysiological signals while effectively reducing the time required for complex skin preparation, such as removing hair and dead skin cells and applying conductive gel. Therefore, considerable demand is expected in the field of wearable robots based on various medical, rehabilitation, and industrial electrophysiological signals, which require short preparation times and high-quality wearability.

[0120] The SNAP according to the embodiment of the present invention is capable of stably measuring high-quality electrophysiological signals for more than one week and is highly compatible with biological tissues. Therefore, it is expected to be highly competitive in the fields of digital healthcare and medicine, which require the acquisition of accurate biosignals over a long period of time without causing discomfort to the user.

[0121] The present invention is expected to create significant industrial added value by proposing electrophysiological signal sensor technology, which is important for feedback linkage with wearable robots and prosthetics in medical rehabilitation, amid growing demand for rehabilitation engineering due to the aging population. Furthermore, the present invention is expected to be highly sought after in industries requiring high practicality and time savings, as it enables high-quality biosignal measurement with simple installation without any additional preparation processes. When applied to wearable devices, the technology is expected to have a bright future in the medical device industry, as it can operate stably for a long period of time and is highly biocompatible, enabling electrophysiological signal monitoring.

[0122] The above-described devices may be implemented using hardware components, software components, and / or a combination of hardware and software components. For example, the devices and components described in the embodiments may be implemented using one or more general-purpose or special-purpose computers, such as a processor, a controller, an arithmetic logic unit (ALU), a digital signal processor, a microcomputer, a field programmable gate array (FPGA), a programmable logic unit (PLU), a microprocessor, or various devices capable of executing and responding to instructions. The processing device may execute an operating system (OS) and one or more software applications running on the OS. The processing device may also access, record, manipulate, process, and generate data in response to the execution of the software. For ease of understanding, a single processing device may be described. However, those skilled in the art will understand that a processing device may include multiple processing elements and / or multiple types of processing elements. For example, a processing device may include multiple processors or one processor and one controller. Other processing configurations, such as parallel processors, are also possible.

[0123] Software may include computer programs, codes, instructions, or a combination of one or more of these, and may configure a processing device to operate as desired or may independently or collectively instruct the processing device. The software and / or data may be embodied in any type of machine, component, physical device, virtual device, computer storage medium, or device to be interpreted by the processing device or to provide instructions or data to the processing device. The software may be distributed and stored and executed in a distributed manner on computer systems connected by a network. The software and data may be stored on one or more computer-readable storage media.

[0124] Methods according to embodiments may be embodied in the form of program instructions executable by various computer means and stored on a computer-readable medium. The computer-readable medium may include, alone or in combination, program instructions, data files, data structures, and the like. The program instructions stored on the medium may be specially designed for the embodiments or may be readily available to those skilled in the art of computer software. Examples of computer-readable storage media include magnetic media such as hard disks, floppy disks, and magnetic tape; optical media such as CD-ROMs and DVDs; magneto-optical media such as floptical disks; and hardware devices specially configured to store and execute program instructions, such as ROM, RAM, flash memory, and the like. Examples of program instructions include not only machine language code, such as that generated by a compiler, but also high-level language code executed by a computer using an interpreter, for example.

[0125] Although the embodiments have been described above based on limited examples and drawings, those skilled in the art will appreciate that various modifications and variations may be made from the above description. For example, the described techniques may be performed in an order different from that described, and / or the described system, structure, device, circuit, or other element may be coupled or combined in a manner different from that described, or may be substituted or replaced by other elements or equivalents, and still achieve suitable results.

[0126] Therefore, different embodiments are within the scope of the appended claims, provided that they are equivalent to the claims.

Claims

1. an electrically conductive adhesive (ECA) layer attached to the user's skin to acquire electrophysiological signals regardless of the user's skin condition; a microneedle sensor including a microneedle array that passes through the electrically conductive adhesive layer, penetrates the stratum corneum, and directly contacts the user's epidermis to reduce skin contact impedance; a stretchable interconnection based on extensible conductive wires, electrically and mechanically connected to the microneedle sensor and having a serpentine structure to dynamically adapt to the user's skin deformation; Stretchable Microneedle Adhesive Patch (SNAP) comprising

2. The electrically conductive adhesive layer is enhancing the electrical interface between the microneedle sensor and the user's skin by providing an additional electrical conduction path to the user's skin around the microneedle sensor to reduce skin contact impedance between the microneedle sensor and the user's skin; The stretchable microneedle adhesive patch of claim 1.

3. The electrically conductive adhesive layer is an electrically conductive adhesive formed from a silicone polymer coating the stretchable interconnect and the microneedle sensor simultaneously provides electrical conductivity and skin adhesion, achieving low impedance between the microneedle sensor and the user's skin; The stretchable microneedle adhesive patch of claim 2.

4. The microneedle sensor comprises: The microneedle array of gold-coated silicone material is integrated under the stretchable interconnect, so that the microneedle array penetrates the stratum corneum of the user and directly contacts the epidermal layer without reaching the nociceptors. The stretchable microneedle adhesive patch of claim 1.

5. The microneedle sensor comprises: The microneedle array is formed by partially dicing a silicon (Si) wafer and isotropic wet etching, and then titanium (Ti) and gold (Au) are deposited on the silicon (Si) wafer. After an electrically conductive adhesive is coated on the front surface of the microneedle array, the bottom of the microneedle array is protected by the evaporated gold and wax applied to the side surfaces of the microneedles in the microneedle array, and the separated microneedles are produced by wet etching. The separated microneedle array is integrated with the stretchable interconnection having a serpentine structure that is electrically and mechanically connected using conductive epoxy, and the wax is removed. The stretchable microneedle adhesive patch of claim 2.

6. The stretchable interconnect comprises: A form in which extensible conductive wires are integrated on a stretchable substrate, and the wires are electrically connected to the microneedle sensor to transmit the acquired electrophysiological signals to a circuit unit for analyzing the electrophysiological signals. The stretchable microneedle adhesive patch of claim 1.

7. The stretchable interconnect comprises: The device has a structure in which extensible conductive lines are integrated on a stretchable substrate, and its serpentine structure allows it to dynamically accommodate the deformation of the user's skin, providing stretchability and comfort for long-term wear. The stretchable microneedle adhesive patch of claim 1.

8. The stretchable microneedle adhesive patch comprises: By providing adhesiveness through the microneedle sensor and the electrically conductive adhesive layer, which have a stiffness modulus similar to that of the user's skin tissue, and providing elasticity through the elastic interconnection, the elastic microneedle adhesive patch can be prevented from peeling off, reducing stress on the user's skin tissue and preventing rashes and irritation, while enabling electrophysiological signals to be measured without deterioration in quality even when worn for a long period of time. The stretchable microneedle adhesive patch of claim 1.

9. A Stretchable Microneedle Adhesive Patch (SNAP) system comprising: a stretchable microneedle adhesive patch attached to the skin of a user and surrounded by a stretchable substrate for acquiring electrophysiological signals; a stretchable electronic circuit electrically connected to the stretchable microneedle adhesive patch to receive the electrophysiological signals, the stretchable electronic circuit being surrounded by a stretchable substrate, for analyzing the acquired electrophysiological signals; a chip component including a BLE SoC and an amplifier for performing real-time multi-channel electrophysiological signal monitoring of the electrophysiological signals received by the stretchable electronic circuit using a user interface application program; Including, The stretchable microneedle adhesive patch comprises: an electrically conductive adhesive (ECA) layer attached to the user's skin to acquire electrophysiological signals regardless of the user's skin condition; a microneedle sensor including a microneedle array that passes through the electrically conductive adhesive layer, penetrates the stratum corneum, and directly contacts the user's epidermis to reduce skin contact impedance; a stretchable interconnect based on extensible conductive wires, electrically and mechanically connected to the microneedle sensor and having a serpentine structure to dynamically adapt to the user's skin deformation; A stretchable microneedle adhesive patch system comprising:

10. a battery connected to the stretchable electronic circuit via a metal pin connector and providing a power source for the stretchable microneedle adhesive patch system; A metal opening on the lower end surface of the stretchable electronic circuit provides electrical connection to the stretchable microneedle adhesive patch system via an anisotropic conductive film cable and a magnetic connector, allowing for semi-permanent use of the circuit and replacement of the stretchable microneedle adhesive patch. The stretchable microneedle adhesive patch system of claim 9.

11. The stretchable substrate is The stretchable microneedle adhesive patch system includes a stretchable microneedle adhesive patch and a stretchable electronic circuit, which provide dynamic compliance to bending and stretching during movement of the user's skin tissue during attachment to the user's skin to acquire electrophysiological signals. The stretchable microneedle adhesive patch system of claim 9.

12. The electrically conductive adhesive layer is providing an additional electrical conduction path to the user's skin around the microneedle sensor to reduce skin contact impedance between the microneedle sensor and the user's skin, thereby enhancing the electrical interface between the microneedle sensor and the user's skin; an electrically conductive adhesive formed from a silicone polymer coating the stretchable interconnect and the microneedle sensor simultaneously provides electrical conductivity and skin adhesion, achieving low impedance between the microneedle sensor and the user's skin; The stretchable microneedle adhesive patch system of claim 9.

13. The microneedle sensor comprises: The microneedle array of gold-coated silicone material is integrated under the stretchable interconnect, so that the microneedle array penetrates the stratum corneum of the user and directly contacts the epidermal layer without reaching the nociceptors. The stretchable microneedle adhesive patch system of claim 9.

14. The stretchable interconnect comprises: A stretchable conductive wire is integrated on a stretchable substrate, and the stretchable conductive wire is electrically connected to the microneedle sensor to transmit an acquired electrophysiological signal to a stretchable electronic circuit for analyzing the electrophysiological signal; The serpentine structure allows for dynamic adaptation to the user's skin deformation, providing stretchability and long-term comfort. The stretchable microneedle adhesive patch system of claim 9.

15. The chip components including the BLE SoC and amplifier include: Supporting closed-loop control of exoskeleton robots through real-time multi-channel electrophysiological signal monitoring using a user interface application program and communication with a control unit using Bluetooth®-based wireless communication. The stretchable microneedle adhesive patch system of claim 9.

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