Wearable patch, manufacturing method thereof, and wearable device containing same

Abstract

The present invention relates to a wearable patch, a manufacturing method thereof, and a wearable device containing same. The wearable patch according to the present invention comprises a base layer and an electrode layer formed on one side of the base layer, wherein, in the base layer, a variable-stiffness portion including a plurality of segments and a flexible portion including a flexible material are alternately formed, the flexible material being filled between the plurality of segments.

Description

Wearable patch, method of manufacturing the same, and wearable device including the same

[0001] The present invention relates to a wearable patch, a method for manufacturing the same, and a wearable device including the same.

[0002] Wearable devices for measuring biosignals are making significant advancements in various fields, including daily life, sports, medicine, and military applications. However, existing wearable devices face issues such as difficulty in collecting highly reliable biosignals due to inconsistent contact and low stability, while the large and rigid components of the devices also cause discomfort when worn.

[0003] Accordingly, the development of wearable patches and devices capable of precise biosignal measurement by maintaining close adhesion despite skin curvature and movement and offering excellent wearability is becoming increasingly important. Although technologies utilizing very thin electrodes have been developed today, they are difficult to handle, have low durability, and, critically, have very low adhesive strength, which makes it impossible to support essential components (Bluetooth modules, batteries, sensors, etc.) required for the practical operation of the device. Furthermore, in the case of skin adhesives with high adhesion, problems arise such as difficulty in removal after use, causing skin damage, and limitations on repeated use; therefore, it is essential to have an adhesive strength control feature that allows the adhesive strength to be lowered when desired by the user.

[0004] Therefore, there is a demand for a patch that simultaneously achieves close contact even on skin contours, maintains attachment even during movement, provides a comfortable fit, and controls adhesive strength, as well as a wearable device that uses the same, but related technology is currently lacking.

[0005] The aforementioned background technology is one that the inventor possessed or acquired in the process of deriving the content of the disclosure of the present application, and it cannot be considered as prior art disclosed to the general public prior to the filing of this application.

[0006] To solve the above-mentioned problem, the present invention aims to provide a wearable patch capable of adjusting adhesive strength, a method for manufacturing the same, and a wearable device including the same.

[0007] However, the problems that the present invention aims to solve are not limited to those mentioned above, and other unmentioned problems will be clearly understood by those skilled in the art from the description below.

[0008] A wearable patch according to the present invention comprises a base layer; and an electrode layer formed on one side of the base layer; wherein the base layer alternately has a variable stiffness portion comprising a plurality of segments and a flexible portion comprising a flexible material, and the flexible material is filled between the plurality of segments.

[0009] According to one embodiment, the segment and the flexible material may each include a shape memory polymer.

[0010] According to one embodiment, the segment comprises stearyl acrylate and lauryl methacrylate in a weight ratio of 3:2 to 4:1, and the flexible material may comprise stearyl acrylate and lauryl methacrylate in a weight ratio of 1:4 to 2:3.

[0011] According to one embodiment, the variable stiffness part and the flexible part may have a length ratio of 1:1 to 3:1 and a weight ratio of 1:1 to 3:1.

[0012] According to one embodiment, the spacing between a plurality of segments within the variable stiffness part may be 0.7 mm to 2 mm each.

[0013] According to one embodiment, the plurality of segments may each have an aspect ratio of 1:1 to 1:4 and a length of 1 mm to 5 mm.

[0014] According to one embodiment, the electrode layer may comprise at least one selected from the group consisting of CNT, graphene, conductive particles, MXene, silver nanowires and gold nanowires.

[0015] According to one embodiment, the electrode layer may include a pattern including a regular or irregular curve, and a part of the electrode layer may be embedded in the segment.

[0016] According to one embodiment, the base layer comprises nanoparticles, and the nanoparticles may comprise at least one selected from the group consisting of carbon black, silica, carbon nanotubes (CNT), and hydroxyapatite.

[0017] According to one embodiment, the nanoparticles may be 3% to 9% by weight of the base layer.

[0018] According to one embodiment, the base layer may have a shape recovery force of 50 kPa to 150 kPa and a tensile strength of 20% to 200%.

[0019] According to one embodiment, the wearable patch may have a thickness of 100 μm to 400 μm.

[0020] According to one embodiment, the segment has a glass transition temperature of 30°C to 45°C, and the flexible material may have a glass transition temperature of less than 30°C.

[0021] According to one embodiment, when the glass transition temperature of the segment is above, the stiffness of the wearable patch may be 70 MPa to 200 MPa and the adhesive strength may be less than 5 kPa.

[0022] According to one embodiment, when the glass transition temperature of the segment is lower than the peel strength of the wearable patch, the peel strength may be 80 N / m or more, and the adhesive strength may be 200 kPa or more.

[0023] A method for manufacturing a wearable patch according to the present invention comprises: a step of arranging a plurality of segments by screen printing; a step of forming a base layer by filling a flexible material between the plurality of segments; a step of forming an electrode layer by spray coating on a substrate; a step of forming an assembly by combining the base layer and the electrode layer; and a step of curing the assembly.

[0024] A wearable device according to the present invention comprises a skin adhesive portion including a wearable patch according to the present invention; and an integrated module portion; wherein the skin adhesive portion collects a biosignal, and the integrated module portion measures the collected biosignal.

[0025] According to one embodiment, the skin adhesive portion further comprises a flexible heater layer; and the flexible heater layer may comprise a liquid metal.

[0026] According to one embodiment, the biosignal may include at least one selected from the group consisting of electrocardiogram, photoplethysmography, electromyography, brainwave, body temperature, pulse, and respiration.

[0027] According to one embodiment, continuous blood pressure may be estimated through simultaneous measurement of an electrocardiogram and a photoplethysmogram.

[0028] The present invention can provide a wearable patch capable of adjusting adhesive strength, a method for manufacturing the same, and a wearable device including the same.

[0029] Specifically, the wearable patch according to the present invention can minimize skin irritation upon removal through strong skin adhesion performance and adhesion force control with excellent adaptability to curved surfaces and skin movements, and can provide a wearable device by stably integrating the device based on high adhesion force.

[0030] Accordingly, the wearable device according to the present invention can enable stable and accurate measurement of multiple types of biosignals with a single device that can be attached to the skin.

[0031] FIG. 1 is a diagram showing the configuration of a wearable patch according to the present invention.

[0032] FIG. 2 is a diagram showing the configuration of the base layer of a wearable patch according to the present invention.

[0033] FIG. 3 is a diagram showing an electrode layer embedded in a segment of a wearable patch according to the present invention.

[0034] Figure 4 shows the self-detachment of a wearable patch according to the present invention through nanoparticle impregnation.

[0035] Figure 5 shows the adhesive structure according to the temperature change of a wearable patch according to the present invention.

[0036] FIG. 6 is a schematic diagram illustrating a method for manufacturing a wearable patch according to the present invention.

[0037] FIG. 7 is a schematic diagram illustrating the layer assembly process of a wearable device according to the present invention.

[0038] FIG. 8 shows a block diagram of a wearable device according to the present invention.

[0039] FIG. 9 shows a wearable patch according to one embodiment of the present invention.

[0040] FIG. 10 shows the results of skin irritation and cytotoxicity tests of a wearable patch according to one embodiment of the present invention.

[0041] FIG. 11 shows a modification of a wearable patch according to one embodiment of the present invention.

[0042] FIG. 12 shows the results of a tensile test of a wearable patch according to one embodiment of the present invention.

[0043] FIG. 13 shows the results of the movement adaptation characteristics of a wearable patch according to one embodiment of the present invention.

[0044] Figure 14 shows the contact resistance of a wearable patch according to one embodiment of the present invention.

[0045] Figure 15 shows the results of the skin contact impedance of a wearable patch according to one embodiment of the present invention.

[0046] Hereinafter, embodiments are described in detail with reference to the attached drawings. However, various modifications may be made to the embodiments, and thus the scope of the patent application is not limited or restricted by these embodiments. It should be understood that all modifications, equivalents, and substitutions to the embodiments are included within the scope of the rights.

[0047] The terms used in the embodiments are for illustrative purposes only and should not be interpreted as intended to be limiting. Singular expressions include plural expressions unless the context clearly indicates otherwise. In this specification, terms such as "comprising" or "having" are intended to indicate the existence of the features, numbers, steps, actions, components, parts, or combinations thereof described in the specification, and should be understood as not precluding the existence or addition of one or more other features, numbers, steps, actions, components, parts, or combinations thereof.

[0048] Unless otherwise defined, all terms used herein, including technical or scientific terms, have the same meaning as generally understood by those skilled in the art to which the embodiments pertain. Terms such as those defined in commonly used dictionaries should be interpreted as having a meaning consistent with their meaning in the context of the relevant technology, and should not be interpreted in an ideal or overly formal sense unless explicitly defined in this application.

[0049] In addition, when describing with reference to the attached drawings, identical components are assigned the same reference numeral regardless of the drawing symbols, and redundant descriptions thereof are omitted. In describing the embodiments, if it is determined that a detailed description of related prior art could unnecessarily obscure the essence of the embodiments, such detailed description is omitted. Furthermore, when describing the components of the embodiments, terms such as first, second, A, B, (a), (b), etc., may be used. These terms are intended merely to distinguish the components from other components, and the essence, order, or sequence of the components is not limited by these terms. Where it is stated that a component is "connected," "combined," or "joined" to another component, it should be understood that while the component may be directly connected or joined to the other component, another component may also be "connected," "combined," or "joined" between each component.

[0050] Components included in any one embodiment and components having common functions shall be described using the same names in other embodiments. Unless otherwise stated, the descriptions given in any one embodiment may also apply to other embodiments, and specific descriptions shall be omitted to the extent of overlap.

[0051] Hereinafter, the wearable patch, the method of manufacturing the same, and the wearable device of the present invention will be described in detail with reference to the embodiments and drawings. However, the present invention is not limited to these embodiments and drawings.

[0052] A wearable patch according to the present invention comprises a base layer; and an electrode layer formed on one side of the base layer; wherein the base layer alternately has a variable stiffness portion comprising a plurality of segments and a flexible portion comprising a flexible material, and the flexible material is filled between the plurality of segments.

[0053] The wearable patch according to the present invention exhibits excellent skin adhesion performance, forming close contact even with skin curvature and maintaining attachment even with movement, and can provide a wearable patch that is easy to attach and detach through the adjustment of adhesive force and a comfortable fit. In other words, it can provide a skin-attached patch with excellent adhesion, detachability, and elasticity.

[0054] FIG. 1 is a diagram showing the configuration of a wearable patch according to the present invention. The wearable patch of the present invention may include a tessellation structure having different rigidity structures, in which a soft flexible material is filled between rigid pieces. Referring to FIG. 1, the wearable patch according to the present invention may include a base layer (100) in which a variable rigidity part (110) including a plurality of segments (111) and a flexible part (120) including a flexible material (121) are alternately formed, and an electrode layer (200) formed on one side of the base layer.

[0055] The variable rigidity part (110) can provide fixing force with high rigidity at room temperature and is easily deformed into a flexible state at high temperature, and the flexible part (120) is flexible even at room temperature and has good elasticity, so it can prevent detachment when bending parts such as joints. As the temperature rises, both the variable rigidity part (110) and the flexible part (120) may have low rigidity in a flexible state. A flexible material (121) is filled between a plurality of segments (111) and may preferably be arranged in a grid shape. The grid arrangement pattern has the characteristic of being able to secure isotropic mechanical properties in the horizontal direction of the pattern. Since it is possible to deform in the horizontal direction in accordance with body movement along with high adhesion, it can have high resistance to peeling.

[0056] Conventional adhesive patches would crack when the skin was deformed, but the wearable patch of the present invention can maintain the shape of the patch stably and improve adhesion even when skin bending occurs in joint areas, etc. due to the elasticity of the flexible part (120) and the repeating structure of the variable stiffness part (110) and the flexible part (120).

[0057] The electrode layer (200) forms an electrical connection and may have conductivity and flexibility. The electrode layer (200) of the present invention may enable stable electrical coupling through the surface adaptability of the base layer (100).

[0058] According to one embodiment, the segment and the flexible material may each include a shape memory polymer.

[0059] Shape memory polymers (SMPs) are materials whose physical properties change reversibly depending on temperature. The variable stiffness characteristics of shape memory polymers can enable the simultaneous securing of a high contact area and high stiffness for high adhesion. In the wearable patch according to the present invention, surface adaptability is improved when the stiffness of the shape memory polymer is lowered through heating, thereby increasing the adhesion of the patch. Subsequently, the patch can be strongly fixed to the skin as it cools due to a temperature change from its adhesive form, causing its shape to harden. When the fixed patch is to be detached, the patch can be heated again to lower its stiffness and restore its shape, allowing it to be easily removed.

[0060] The shape memory polymer mentioned above may be applied without limitation as long as it is a shape memory polymer capable of adhering to the human body. Preferably, it may include at least one selected from the group consisting of lauryl methacrylate, stearyl acrylate, polycaprolactone, polyurethane acrylate, polyvinyl chloride, polyethylene glycol dimethacrylate, tert-butyl acrylate, stearyl methacrylate, acrylic acid, polyurethane, polyamide, epoxy, olefin, polysiloxane, polydimethylsiloxane, polyimide, polyethylene glycol diacrylate, chitosan, and polycarbonate. The types of polymers of the segment and the flexible material may be the same, partially the same, or entirely different.

[0061] According to one embodiment, the segment comprises stearyl acrylate and lauryl methacrylate in a weight ratio of 3:2 to 4:1, and the flexible material may comprise stearyl acrylate and lauryl methacrylate in a weight ratio of 1:4 to 2:3.

[0062] The weight ratio of stearyl acrylate and lauryl methacrylate in the segment may preferably be 3:2 to 7:3 or 7:3 to 4:1. If the weight ratio of lauryl methacrylate is below the above range, there may be a problem where the glass transition temperature rises above the skin damage temperature, and if it exceeds the above range, there may be a problem where the glass transition temperature is too low and rigidity cannot be maintained at room temperature.

[0063] The weight ratio of stearyl acrylate and lauryl methacrylate in the flexible material may preferably be 1:4 to 3:7 or 3:7 to 2:3. If the weight ratio falls outside the above range, there may be a problem of reduced flexibility due to a lack of elasticity at room temperature.

[0064] By including the weight ratio of stearyl acrylate and lauryl methacrylate within the above range, the segment and the flexible material can provide a wearable patch with optimized skin adhesion by precisely controlling the stiffness change characteristics, and by controlling the glass transition temperature, it can be used within a temperature range safe for skin burns and exhibit excellent biocompatibility through the biocompatible material. In addition, since the segment and the flexible material are composed of the same material, failure due to stress concentration at the interface between the variable stiffness part and the flexible part can be minimized.

[0065] According to one embodiment, the variable stiffness part and the flexible part may have a length ratio of 1:1 to 3:1 and a weight ratio of 1:1 to 3:1.

[0066] FIG. 2 is a diagram showing the configuration of the base layer of a wearable patch according to the present invention. Referring to FIG. 2, the length ratio of the variable stiffness portion (110) and the flexible portion (120) is such that the length (l) of the variable stiffness portion r ) and length of the flexible part (l cIt may mean that the variable stiffness and flexible parts have a length ratio within the above range and can exhibit mechanical similarity to skin through excellent adhesive ability and flexibility.

[0067] The length ratio of the variable stiffness portion and the flexible portion may preferably be 1:1 to 2:1 or 2:1 to 3:1. If the variable stiffness portion is less than the above length ratio, the area of ​​the variable stiffness portion responsible for high adhesion and adhesion switching characteristics is reduced, which may lead to a decrease in vertical adhesion and adhesion on / off characteristics. If the above length ratio is exceeded, the effective stiffness of the wearable patch increases to 750 kPa or more, which may cause mechanical mismatch with biological tissues such as skin (approx. 100 to 500 kPa). Additionally, there may be a problem in that elasticity is limited, potentially reducing the maximum elongation to break to less than 55%.

[0068] The weight ratio of the variable stiffness part and the flexible part may preferably be 1:1 to 2:1 or 2:1 to 3:1. If the variable stiffness part is less than the weight ratio or the flexible part is more than the weight ratio, the gap between segments widens and the bending stiffness of the variable stiffness part decreases, making it difficult to obtain a large crack arrest effect, which may result in a problem of low peel strength. If the variable stiffness part is more than the weight ratio or the flexible part is less than the weight ratio, the gap between segments narrows, increasing the bending stiffness of the variable stiffness part, but the size of the flexible part becomes smaller than the characteristic length, so the optimal crack arrest effect is not obtained, which may result in problems of easy detachment and insufficient adhesion below the glass transition temperature.

[0069] Here, the peel resistance effect is such that when crack shear moves from a flexible part to a high-rigidity part, the high-rigidity part has high resistance to deformation, and the 'work' created by the peel force at this moment is converted into energy to bend the high-rigidity part, thereby dissipating energy and causing an instantaneous improvement in peel adhesion. The ratio of adhesion improvement may vary depending on the ratio of bending rigidity between the variable rigidity part and the flexible part. In the case of general commercial adhesives, when a crack starts, it propagates to a steady state adhesive strength, whereas the wearable patch according to the present invention can exhibit a peel resistance effect by generating an instantaneous improved peel adhesion.

[0070] According to one embodiment, the spacing between a plurality of segments within the variable stiffness part may be 0.7 mm to 2 mm each.

[0071] The spacing between the above plurality of segments may be constant. If the spacing between the segments deviates from the above range, there may be a problem with reduced peel resistance effect.

[0072] According to one embodiment, the plurality of segments may each have an aspect ratio of 1:1 to 1:4 and a length of 1 mm to 5 mm.

[0073] The plurality of segments may be in the shape of polygons, wherein the aspect ratio may refer to the ratio of width to height. Preferably, the aspect ratio may be 1:1 to 1:2, and more preferably, the aspect ratio may be 1:1. If the aspect ratio of the segments falls outside the above range, there may be a problem of reduced peel resistance effect.

[0074] The above length may refer to the length of the longest side of each of the plurality of segments. Preferably, it may be the length of one base of a square. Preferably, it may be 1 mm to 4 mm; 1 mm to 3 mm; 1 mm to 2 mm; 2 mm to 5 mm; 2 mm to 4 mm; 2 mm to 3 mm; 3 mm to 5 mm; 3 mm to 4 mm; or 4 mm to 5 mm. The length of the segment is an important factor in movement adaptation characteristics and is a length that takes into account the radius of curvature of human joints to enable stable contact; if the length of the segment is less than the above range, there may be a problem in that it is difficult to obtain the optimal peeling resistance effect. Specifically, for the optimal peeling resistance effect, the size of the segment must be larger than the stress field size. That is, the segment's size It must be greater. (F = Adhesive strength of a patch consisting only of flexible parts, EI) compliant = Bending stiffness of the flexible part) Furthermore, if the length of the segment exceeds the above range, there may be a problem in that stable contact cannot be maintained against deformation caused by human joints, muscles, etc. Specifically, when the adhesive patch is deformed into a shape with non-zero Gaussian curvature, according to the stationary principle, stable contact can be maintained when the elastic deformation energy is smaller than the adhesive energy. In this case, the deformation energy and the adhesive energy follow the relationship shown in the following equation.

[0075]

[0076] (E r = segment modulus, t = patch thickness, p = substrate radius of curvature, v = Poisson's ratio, w ad = Adhesion work)

[0077] Ultimately, the size of the segment (l rThe smaller the value, the more deformation energy can be reduced, so multiple small segments may be more advantageous for stable contact than a single large segment.

[0078] According to one embodiment, the electrode layer may comprise at least one selected from the group consisting of CNT, graphene, conductive particles, MXene, silver nanowires and gold nanowires.

[0079] The electrode layer is configured to transmit an electrical signal and is not limited to any material having conductivity capable of forming an electrical connection.

[0080] The above electrode layer can enable close electrical contact and improve the sensitivity of the signal sensor.

[0081] According to one embodiment, the electrode layer may include a pattern including a regular or irregular curve, and a part of the electrode layer may be embedded in the segment.

[0082] The electrode layer may have flexibility and conductivity by including a pattern comprising regular or irregular curves. Preferably, it may include a wavy curve.

[0083] FIG. 3 is a diagram showing an electrode layer embedded in a segment of a wearable patch according to the present invention. Referring to FIG. 3, a portion of the electrode layer (200) is embedded in each of a plurality of segments (111), and through the surface adaptability of the segment (111), stable electrical coupling with the surface of the electrode may be possible, and low skin contact impedance, excellent durability, and reusability may be exhibited. A portion of the electrode layer (200) not embedded in the segment (111) may be connected in a pattern including a curve.

[0084] According to one embodiment, the base layer comprises nanoparticles, and the nanoparticles may comprise at least one selected from the group consisting of carbon black, silica, carbon nanotubes (CNT), and hydroxyapatite.

[0085] Nanoparticles may induce self-detachment. This may reduce the detachment adhesion force by self-reducing the contact area upon shape recovery. Figure 4 illustrates self-detachment according to the nanoparticle impregnation of a wearable patch according to the present invention. Referring to Figure 4, generally, shape memory polymers have low physical properties upon shape recovery, making self-detachment difficult and thus low skin adhesion force upon detachment cannot be expected. However, the wearable patch according to the present invention, by impregnating nanoparticles, releases stored elastic energy and bounces off the skin surface, enabling self-detachment through low detachment adhesion force, thereby minimizing skin irritation when removing the wearable patch.

[0086] According to one embodiment, the nanoparticles may be 3% to 9% by weight of the base layer.

[0087] Preferably, it may be 3 weight% to 7 weight%; 3 weight% to 5 weight%; 5 weight% to 9 weight%; 5 weight% to 7 weight%; or 7 weight% to 9 weight%.

[0088] If the content is below the aforementioned range, the shape recovery characteristics of the variable stiffness section may be reduced, and there may be issues making it difficult to induce spontaneous detachment. Shape recovery occurs when the variable stiffness section is reheated above the phase transition temperature; during this process, the adhesion to the substrate is overcome by the shape recovery force, leading to spontaneous detachment. The shape recovery force is closely related to the stiffness of the reheated variable stiffness section, and nanoparticles play a role in maximizing shape recovery characteristics by increasing this stiffness. However, if the nanoparticle content is below the aforementioned range, the shape recovery force is insufficient, which may hinder smooth spontaneous detachment. If the content exceeds the aforementioned range, the stiffness of the variable stiffness section in the heated state increases excessively, which may increase the pressure required to make close contact with a rough surface. This may lead to problems such as causing damage to biological tissues or hindering close contact.

[0089] According to one embodiment, the nanoparticles in the segment may be 3% to 9% by weight of the segment, and the nanoparticles in the flexible material may be 3% or less by weight of the flexible material.

[0090] Flexible materials can be considered as segment materials with a low phase transition temperature and can maintain a continuously heated state (rubbery state) at room temperature and body temperature. Therefore, if the nanoparticle content exceeds 3 weight%, there is a possibility that unintended spontaneous detachment will continuously occur in the flexible part, so it may be desirable to have a content of 3 weight% or less.

[0091] The flexible material may include nanoparticles to control the stiffness of the flexible portion and the entire patch, but may not include nanoparticles.

[0092] According to one embodiment, the base layer may have a shape recovery force of 50 kPa to 150 kPa and a tensile strength of 20% to 200%.

[0093] The above base layer may have excellent shape recovery ability. Shape recovery ability is the ability to self-reduce the contact area upon shape recovery, and preferably, it may be between 100 kPa and 150 kPa. If the shape recovery ability is below the above range, spontaneous detachment from the skin substrate may not occur smoothly, which may result in difficulties in securing the on / off characteristics of the adhesion; if it exceeds the above range, it may result in difficulties in forming close contact, which may limit the ability to secure sufficient skin adhesion. While exhibiting the above shape recovery ability, it can be easily removed as needed through low detachment adhesion.

[0094] The tensile strength indicates the degree of tension without breaking during tension, and the length of the tensioned portion may be 20% to 200% of the length of the untensioned portion. That is, the tensioned base layer may be 120% to 300% of the untensioned base layer. This may be an elasticity range without loss of adhesive ability, and while exhibiting the above tensile strength, it is possible to prevent detachment even during movement due to excellent elasticity.

[0095] According to one embodiment, the wearable patch may have a thickness of 100 μm to 400 μm.

[0096] Preferably, the thickness may be 100 μm to 300 μm; 100 μm to 200 μm; 200 μm to 400 μm; 200 μm to 300 μm; or 300 μm to 400 μm. If the thickness is less than the above range, there may be problems such as difficulty in handling and reduced mechanical durability, which limits smooth operation and repeated use; and if it exceeds the above range, there may be problems such as reduced excessive bending stiffness and flexibility, which makes it difficult to use as a wearable patch applied to a skin surface with a lot of movement.

[0097] According to one embodiment, the segment has a glass transition temperature of 30°C to 45°C, and the flexible material may have a glass transition temperature of less than 30°C.

[0098] The glass transition temperature and melting point of the above segment are 30°C or higher. At room temperature (25°C), it exists in an opaque and rigid form, but when the temperature rises due to heating, the rigidity decreases and it changes to a flexible state. It can regain rigidity at room temperature, and if the temperature is above the glass transition temperature of the segment, the wearable patch can be easily detached by crack propagation.

[0099] The glass transition temperature of the above segment may preferably be 30 ℃ to 40 ℃; 30 ℃ to 35 ℃; 35 ℃ to 45 ℃; 35 ℃ to 40 ℃; or 40 ℃ to 45 ℃.

[0100] Preferably, the glass transition temperature may be higher than body temperature while minimizing skin and tissue damage. If a shape memory polymer with a glass transition temperature lower than body temperature is used, a phase transition may occur due to body temperature, making it impossible to maintain a shape fixation state capable of securing high adhesion; therefore, a glass transition temperature higher than body temperature may be desirable. Additionally, since skin can suffer thermal damage at temperatures above 45°C, a glass transition temperature below the skin damage temperature may be desirable for use as a skin-attached patch without skin damage.

[0101] The glass transition temperature and melting point of the above flexible material are less than 30°C, and it is transparent at room temperature (25°C) and can function as a flexible joint with behavior similar to that of an elastic material. The above flexible material maintains a flexible state even at low temperatures, allowing for close contact that does not detach even during movement.

[0102] That is, the wearable patch according to the present invention comprises a repeating structure of variable stiffness and flexible parts, each including a plurality of segments having different glass transition temperature values. At room temperature, when a peel line passes from a flexible region to a rigid region (segment), the segment with high stiffness resists deformation, thereby significantly increasing the peel strength. Additionally, the stiffness of the segment can be lowered through heating to temporarily convert from a heterogeneous structure to a homogeneous structure, thereby eliminating the peel resistance effect, and the patch can exhibit switchable skin adhesion as it is detached as needed. Since the variable stiffness part including the segment can regain stiffness at room temperature, switching characteristics can be further maximized through shape adaptation and shape recovery.

[0103] According to one embodiment, when the glass transition temperature of the segment is above, the stiffness of the wearable patch may be 70 MPa to 200 MPa and the adhesive strength may be less than 5 kPa.

[0104] FIG. 5 shows the adhesive structure according to the temperature change of a wearable patch according to the present invention. Referring to FIG. 5, when the temperature is above the glass transition temperature of the segment (right drawing), the variable stiffness portion and the flexible portion may have the same adhesive strength, and the wearable patch may temporarily convert from a heterogeneous structure to a homogeneous structure to have a homogeneous structure.

[0105] When a temperature above the glass transition temperature of the segment is maintained, the bending stiffness of the variable stiffness portion may change uniformly regardless of the pattern. Since the bending stiffness is the same regardless of the patch position, peel propagation may occur in a manner similar to that of conventional adhesive tapes. In particular, when a temperature above the glass transition temperature is maintained, it exhibits rubber-like stiffness and possesses high elastic energy; consequently, the adhesive strength decreases, and through shape recovery, it spontaneously pushes away the adhesive target on a rough surface, minimizing the contact area and allowing for lower adhesive strength, which may enable easy detachment.

[0106] If the adhesive strength falls outside the above range, there may be a problem where the patch cannot be removed smoothly without catching.

[0107] According to one embodiment, when the glass transition temperature of the segment is lower than the peel strength of the wearable patch, the peel strength may be 80 N / m or more, and the adhesive strength may be 200 kPa or more.

[0108] Referring to Fig. 5, when the glass transition temperature of the segment is below the level shown in the left diagram, the bending stiffness of the variable stiffness section may vary depending on the variable stiffness section and the flexible section. Since the bending stiffness differs depending on the patch position, crack arrest may occur the moment the peel line crosses from the variable stiffness section to the interface of the flexible section. This crack arrest phenomenon may be caused by a change in the deformation energy of the adhesive patch. Within the flexible section, the deformation is maintained in accordance with the bending shape of the adhesive patch for peeling, whereas the variable stiffness section has high stiffness, so deformation does not occur easily, causing the bending shape of the patch to change instantaneously. This change in deformation energy can instantaneously generate strong peeling strength.

[0109] If the peel strength is below the above range, the peel resistance effect is reduced, which may cause the patch to peel off easily, and if the adhesive strength is below the above range, the adhesive strength is reduced, which may cause the patch to peel off easily.

[0110] A method for manufacturing a wearable patch according to the present invention comprises: a step of arranging a plurality of segments by screen printing; a step of forming a base layer by filling a flexible material between the plurality of segments; a step of forming an electrode layer by spray coating on a substrate; a step of forming an assembly by combining the base layer and the electrode layer; and a step of curing the assembly.

[0111] FIG. 6 is a schematic diagram illustrating a method for manufacturing a wearable patch according to the present invention. The wearable patch of the present invention may be formed by manufacturing a base layer and an electrode layer separately and combining them.

[0112] First, the step of arranging multiple segments by screen printing can be performed by placing a shadow mask on a glass substrate and using screen printing to create a segment array such as a grid array. After removing the shadow mask for creating the segment array, a flexible material may be filled between the multiple segments to form a base layer. Here, the segments and the flexible material may each include a shape memory polymer.

[0113] The step of forming an electrode layer by spray coating on a substrate may preferably involve placing a shadow mask having a pattern on a PET substrate and spraying a conductive solution to form an electrode layer. Here, the conductive solution may comprise at least one selected from the group consisting of CNTs, graphene, conductive particles, MXene, silver nanowires, and gold nanowires. The spray coating may form a percolation network of the conductive solution.

[0114] The step of forming an assembly by combining the base layer and the electrode layer may preferably involve using a pre-cured base layer. Subsequently, through a step of curing the assembly, a portion of the electrode layer may be embedded in a segment of the base layer. At this time, the curing may preferably be performed by curing with UV light for 1 to 30 minutes.

[0115] A wearable device according to the present invention comprises a skin adhesive portion including a wearable patch according to the present invention; and an integrated module portion; wherein the skin adhesive portion collects a biosignal, and the integrated module portion measures the collected biosignal.

[0116] Conventional wearable devices have difficulty collecting highly reliable biosignals due to inconsistent contact, and large, rigid components of the devices cause discomfort when worn. Accordingly, there is an increasing importance in developing wearable devices that offer excellent wearability and maintain close adhesion to the skin's curvature and movement to enable precise biosignal measurement. Furthermore, this high adhesion necessitates an adhesive strength control feature that allows the adhesion to be lowered when desired by the user.

[0117] The wearable device according to the present invention may enable precise and stable acquisition and processing of biosignals using skin adhesion-based technology. The skin adhesive portion including the wearable patch according to the present invention attaches the wearable device to a human body measurement site (e.g., local skin), thereby providing close surface contact and excellent adhesion, and can provide switchable adhesion characteristics that allow for easy attachment and detachment without skin irritation and repeated use. The skin may be freely attached to skin in areas capable of collecting biosignals, such as the neck, ankle, and arm, in addition to the wrist, chest (heart), and scalp.

[0118] By the excellent adhesive strength of the wearable patch according to the present invention, a biosignal measurement element can be stably fixed to the skin, enabling accurate and stable signal measurement and improving the quality of the measured signal. Accordingly, a single device capable of securing excellent skin adhesion performance and stable biosignal acquisition based on excellent movement and surface adaptation characteristics can be provided.

[0119] FIG. 7 is a schematic diagram illustrating the layer assembly process of a wearable device according to the present invention. Referring to FIG. 7, the process of assembling a wearable device including a skin adhesive part (710) and an integrated module part (720) involves preparing the skin adhesive part (710) and the integrated module part (720), and the protruding connecting lines of the electrodes of the wearable patch constituting the skin adhesive part (710) can be connected to flat electrodes located on the back of the integrated module part (720). Based on the low contact resistance and high adhesive strength of the skin adhesive part (710), a stable electrical connection can be made, and biosignals can be collected with low noise and low power.

[0120] FIG. 8 shows a block diagram of a wearable device according to the present invention. Referring to FIG. 8, the darker parts represent sensor sections, and the other sections represent circuit components. Preferably, the integrated module may include a sensor, a chip, a Biomedical IC, a wireless communication MCU, a battery, etc.

[0121] The above sensor can sense signals in addition to collecting biosignals through the skin adhesive part. The sensor may include a PPG sensor, an IMU sensor, a temperature sensor, etc. For example, in the case of a PPG sensor, an LED and a photodiode inside the PPG sensor can detect light reflected from the blood volume changing over time, and in the case of an IMU sensor, it can monitor 3-axis acceleration and direction during movement along with biosignals.

[0122] The above-mentioned Biomedical IC is intended for processing and communicating biological signals and may include a multimode biomedical analog front-end (AFE), an analog-to-digital converter (ADC), an SPI interface, and a power management circuit. Here, SPI is a communication method that enables a microcontroller to exchange data quickly and efficiently with other electronic components, such as sensors, memory chips, and displays.

[0123] The above wireless communication MCU may include a BLE MCU and may be responsible for system control and wireless communication.

[0124] The above battery, intended to supply power, may be a rechargeable battery or a non-rechargeable battery. Examples of suitable batteries may include, for instance, lithium-ion batteries, nickel batteries (e.g., nickel-cadmium batteries), alkaline batteries, etc.

[0125] According to one embodiment, the skin adhesive portion further comprises a flexible heater layer; and the flexible heater layer may comprise a liquid metal.

[0126] Referring to FIG. 7, a flexible heater layer (730) may be inserted onto the skin adhesive part (710), and an integrated module part (720) may be assembled. The flexible heater layer (730) may enable switching of adhesive force and may apply heat through Joule heating via voltage applied from the integrated module part (720).

[0127] The flexible heater layer may contain liquid metal, which has low resistance, enabling efficient heating while minimizing power loss. Unlike solid metal electrodes, it can deform together with a flexible substrate, allowing performance to be maintained even under repeated deformation. Additionally, due to its excellent elasticity, it may be suitable for application in wearable patches.

[0128] According to one embodiment, the biosignal may include at least one selected from the group consisting of electrocardiogram, photoplethysmography, electromyography, brainwave, body temperature, pulse, and respiration.

[0129] The wearable device according to the present invention can provide a device for measuring biosignals. The biosignals that can be collected through the skin adhesive portion of the present invention may be an electrocardiogram, photoplethysmography, electromyography, brainwaves, body temperature, pulse, or respiration.

[0130] According to one embodiment, continuous blood pressure may be estimated through simultaneous measurement of an electrocardiogram and a photoplethysmogram.

[0131] The skin adhesive part can measure various types of biosignals and estimate biosignals (e.g., continuous blood pressure) based on the various types of biosignals. It can estimate continuous blood pressure through calculations based on electrocardiograms and photoplethysmography measured as various types of biosignals.

[0132] The skin adhesion technology comprising a wearable patch applied to a wearable device according to the present invention can form close contact and stable attachment with the skin. This enables the acquisition of high-quality biosignals and can minimize signal noise caused by motion artifacts.

[0133] The wearable device according to the present invention is a single device capable of being attached to the skin, possessing excellent device integration performance, and can stably support essential components while bearing weight thanks to strong adhesive force. It allows for close attachment along the fine contours of the skin, and since the adhesive force is maintained even during vigorous movements to obtain high-quality biosignals while embedding a battery, sensors, etc., it enables not only stable skin attachment but also adaptation to dynamic movements to acquire high-quality biosignals. Furthermore, it is possible to measure various types of biosignals (ECG, photoplethysmography, electromyography, brainwaves, respiration, etc.) and to estimate continuous blood pressure through the simultaneous measurement of ECG and photoplethysmography, thereby providing a skin-attachable continuous blood pressure estimation wearable device. Based on low contact impedance and a high signal-to-noise ratio, it is perfectly integrated with the human skin and can accurately measure various biosignals even in environments with movement, making it a significant contribution to healthcare monitoring devices that continuously monitor, as well as personalized health management and remote medical services. Additionally, due to high reusability and adhesive switching characteristics, it offers advantages in terms of cost-effectiveness and sustainability.

[0134] The present invention will be explained in more detail below through examples and comparative examples.

[0135] However, the following examples are merely for illustrating the present invention, and the content of the present invention is not limited to the following examples.

[0136] Examples

[0137] Wearable patch manufacturing

[0138] A shadow mask was placed on a silane-treated glass substrate, and multiple segments of a grid arrangement were formed using screen printing. Subsequently, the segment arrangement was completed at a temperature of 10°C or lower, and a flexible material was filled between the segments to form a base layer. A patterned shadow mask was placed on a PET substrate, and an electrode layer was formed by spraying a silver nanowire conductive solution. The pre-cured base layer and electrode layer were combined and UV cured for 5 to 15 minutes. Here, the segments consisted of stearyl acrylate and lauryl methacrylate in a ratio of 7:3 and contained 6 wt% of silica nanoparticles. The silanol and hydroxyl groups of the silica nanoparticles can easily combine with the acrylate groups of the shape memory polymer.

[0139] FIG. 9 shows a wearable patch according to an embodiment of the present invention. A plurality of segments having a tessellation structure and an electrode composed of a flexible material and silver nanowires filled between them can be seen.

[0140] Analysis of Wearable Patch Characteristics

[0141] FIG. 10 shows the results of skin irritation and cytotoxicity tests of a wearable patch according to one embodiment of the present invention. Referring to FIG. 10, the base layer patch (TSP) of the wearable patch according to the present invention exhibits minimal skin irritation through adhesive switching characteristics and shows a cell viability of 95% compared to a negative control sample, and it was confirmed that it has excellent biocompatibility and can be applied to the skin.

[0142] FIG. 11 shows the deformation of a wearable patch according to one embodiment of the present invention. Referring to FIG. 11, an NSP, which is an SMP without a tessellation structure, does not stretch well with a strain of less than 15%, whereas a patch (TSP) including a tessellation structure according to the present invention can exhibit various types of deformation, including twisting and expansion, even at room temperature.

[0143] Figure 12 shows the results of a tensile test of a wearable patch according to an embodiment of the present invention. Finite element analysis was performed to evaluate the adaptability of a TSP with a tessellation flexible structure applied to a stretchable substrate to deformation. In the case of an SMP without a tessellation structure, large stress was concentrated at the edge of the contact interface after the substrate was stretched, indicating a high risk of delamination. In contrast, in the case of a TSP containing a tessellation structure, the tessellation structure dispersed the stress generated at the contact interface, thereby preventing delamination. It was confirmed that this finite element analysis was similar to the tensile test of an actual substrate. Referring to Figure 11, both patches initially adhered well to the artificial skin substrate, but in the case without a tessellation structure (NSP), cracks began at the edge adhesion even at only 5% deformation of the substrate. On the other hand, it was confirmed that the patch according to the present invention (TSP) maintained strong adhesion even at 60% deformation due to improved elasticity and reduced stress distribution at the contact interface.

[0144] Figure 13 shows the results of the movement adaptation characteristics of a wearable patch according to one embodiment of the present invention. The results of the movement adaptation characteristics of the TSP applied to an actual joint area show that after bending the wrist joint, the structureless SMP separated, but the TSP with a tessellation structure maintained close contact with the skin and adapted well to large and dynamic movements of the finger joint.

[0145] Figure 14 shows the results of the contact resistance of a wearable patch according to an embodiment of the present invention. Referring to Figure 14, before the shape-memory polymer electrode was surface-adapted to a target substrate, it can be seen that the contact resistance increased rapidly as the RMS roughness of the substrate increased due to poor contact, and that very high contact resistance was observed even when high pressure was applied. On the other hand, after surface adaptation, the electrode showed low contact resistance on an electrode substrate with high RMS even without external pressure.

[0146] FIG. 15 shows the results of the skin contact impedance of a wearable patch according to one embodiment of the present invention. Referring to FIG. 15, it can be seen that the wearable patch (TSP electrode) according to the present invention has a lower skin contact impedance compared to a commercial Ag / AgCl electrode. In particular, it exhibits a contact impedance similar to or even lower than that of Ag / AgCl with an additional conductive gel paste applied, and this low contact impedance can be maintained for more than 7 days. On the other hand, it can be seen that existing commercial electrodes rely on hydrogel electrodes and are very susceptible to drying.

[0147] Although embodiments have been described as above, those skilled in the art can apply various technical modifications and variations based on the above. For example, suitable results can be achieved even if the described techniques are performed in a different order than described, and / or the components of the described system, structure, device, circuit, etc. are combined or assembled in a form different from described, or replaced or substituted by other components or equivalents.

[0148] Therefore, other implementations, other embodiments, and equivalents to the claims also fall within the scope of the claims set forth below.

Claims

1. Base layer; and Includes an electrode layer formed on one side of the base layer; The above base layer is formed such that a variable stiffness portion including a plurality of segments and a flexible portion including a flexible material are alternately formed. The flexible material is filled between the plurality of segments. Wearable patch.

2. In Paragraph 1, The above segment and the above flexible material each comprise a shape memory polymer. Wearable patch.

3. In Paragraph 1, The above segment comprises stearyl acrylate and lauryl methacrylate in a weight ratio of 3:2 to 4:1, and The above flexible material comprises stearyl acrylate and lauryl methacrylate in a weight ratio of 1:4 to 2:

3. Wearable patch.

4. In Paragraph 1, The above variable stiffness part and the above flexible part have a length ratio of 1:1 to 3:1, and A weight ratio of 1:1 to 3:1, Wearable patch.

5. In Paragraph 1, The spacing between a plurality of segments within the variable stiffness part is, respectively, 0.7 mm to 2 mm. Wearable patch.

6. In Paragraph 1, The above plurality of segments, each, The aspect ratio is 1:1 to 1:4, and One having a length of 1 mm to 5 mm, Wearable patch.

7. In Paragraph 1, The electrode layer comprises at least one selected from the group consisting of CNT, graphene, conductive particles, MXene, silver nanowires, and gold nanowires. Wearable patch.

8. In Paragraph 1, The electrode layer comprises a pattern including a regular or irregular curve, and A portion of the electrode layer is embedded in the segment, Wearable patch.

9. In Paragraph 1, The above base layer contains nanoparticles, and The above nanoparticle comprises at least one selected from the group consisting of carbon black, silica, carbon nanotubes (CNT), and hydroxyapatite. Wearable patch.

10. In Paragraph 9, The above nanoparticles are 3% to 9% by weight of the base layer, Wearable patch.

11. In Paragraph 1, The above base layer has a shape recovery force of 50 kPa to 150 kPa, and One having a tensile strength of 20% to 200%, Wearable patch.

12. In Paragraph 1, The above-mentioned wearable patch has a thickness of 100 μm to 400 μm, Wearable patch.

13. In Paragraph 1, The above segment has a glass transition temperature of 30 ℃ to 45 ℃, and The above flexible material is one having a glass transition temperature of less than 30 ℃. Wearable patch.

14. In Paragraph 1, If the glass transition temperature of the above segment is higher than, The stiffness of the above-mentioned wearable patch is 70 MPa to 200 MPa, and one having an adhesive strength of less than 5 kPa, Wearable patch.

15. In Paragraph 1, If the glass transition temperature of the above segment is less than, The peel strength of the above-mentioned wearable patch is 80 N / m or more, and one having an adhesive strength of 200 kPa or more, Wearable patch.

16. A step of arranging multiple segments by screen printing; A step of forming a base layer by filling a flexible material between the plurality of segments; A step of forming an electrode layer by spray coating on a substrate; A step of forming an assembly by combining the base layer and the electrode layer; and A step of curing the above assembly; comprising Method for manufacturing a wearable patch.

17. A skin adhesive portion comprising the wearable patch of claim 1; and Includes an integrated module section; and The above-mentioned skin adhesive part collects biosignals, and The above integrated module is capable of measuring the collected biosignals. Wearable device.

18. In Paragraph 17, The above skin adhesive portion further includes a flexible heater layer; and The above flexible heater layer comprises liquid metal, Wearable device.

19. In Paragraph 17, The above biosignal comprises at least one selected from the group consisting of electrocardiogram, photoplethysmography, electromyography, brainwave, body temperature, pulse, and respiration. Wearable device.

20. In Paragraph 17, Estimating continuous blood pressure through simultaneous measurement of electrocardiogram and photoplethysmography, Wearable device.

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