Negative capacitive fiber-type strain sensing system

Abstract

The present invention relates to a negative capacitive fiber-type strain sensing system comprising: an induction coil for transmitting and receiving electrical stimulation signals; a fiber strain sensor in which a first electrode, a dielectric fiber and a second electrode are sequentially arranged, and which is formed by winding the first electrode, the dielectric fiber and the second electrode a plurality of times into a spring structure; and a transmission line electrically connecting the induction coil to the fiber strain sensor, and thus wireless signal amplification with the body is possible such that recovery efficiency can be increased through effective rehabilitation and therapeutic assistance.

Description

Negative electrostatic fiber strain sensing system

[0001] The present invention relates to a negative capacitive fiber-type strain sensing system, and more specifically, to a negative capacitive fiber-type strain sensing system capable of amplifying a wireless signal by utilizing the reduction in capacitance due to deformation caused by an external force of a fiber-type strain sensor located inside the body.

[0002] As the elderly population increases globally, the importance and interest in healthcare are growing in modern society. In particular, the number of patients with ligament-related diseases is also increasing among the elderly.

[0003] The inherent biomechanical properties and regenerative capacity of body tissues depend significantly on the individual. Therefore, during the healing and rehabilitation phases following soft tissue injury, continuous monitoring of various biomechanical signals emitted from treated tissues is becoming increasingly urgent for personalized treatment and rehabilitation strategies. Furthermore, there is high demand for real-time monitoring of these signals within the field of sports biomechanics research. Nevertheless, current clinical tools such as magnetic resonance imaging (MRI) and sonography have limited applicability for continuous monitoring.

[0004] Implantable electronic devices are devices inserted into the body to measure and monitor human movements. Implantable devices have the advantage of improving the accuracy of measurement results by directly detecting bodily responses. However, existing implantable sensing systems face limitations in long-term sensor use due to the difficulty of attaching to organs and tissues with complex internal structures, as well as the potential for inflammation and immune responses caused by the presence of batteries and circuits. To address this, a passive RLC circuit-based electronic device has been fabricated that allows for stable fixation to the target site by manufacturing the sensor in the form of a suture, and enables wireless measurement of biosignals without a battery.

[0005] However, existing implantable electronic devices as well as passive RLC circuit-based wireless sensing systems have limitations in providing stable wireless communication signals over long periods. Specifically, conventional passive wireless sensing systems generally operate by increasing the sensor response (such as capacitance) to external stimuli; this leads to a decrease in the Q factor, which determines the signal of RLC circuit-based passive wireless communication systems, potentially causing the wireless communication signal to attenuate. This signal attenuation poses a problem, as the wireless sensing system may be interfered with in environments where it is located deep within the body and subject to significant movement, thereby creating significant difficulties in rehabilitation and therapeutic assistance.

[0006] The present invention aims to provide a negative capacitive fiber-type strain sensing system configured such that the capacitance measured by the strain sensor decreases in accordance with the action of an external force, so that wireless signals can be amplified within the body and the signals can be precisely measured by an external reading system.

[0007] In addition, the present invention aims to provide a negative capacitive fiber-type strain sensing system in which a plurality of sensing bundles are provided in the strain sensor so that the wireless signal can be amplified even when the amount of deformation of the sensor increases as the magnitude of the external force increases, and the capacitance can be reduced as the spacing between the sensing bundles increases due to the external force.

[0008]

[0009] The purposes of the embodiments of the present invention are not limited to those mentioned above, and other unmentioned purposes will be clearly understood by those skilled in the art from the description below.

[0010] According to one embodiment of the present invention, a negative capacitive fiber-type strain sensing system may be provided, comprising an induction coil for transmitting and receiving an electrical stimulation signal, a fiber strain sensor in which a first electrode, a dielectric fiber, and a second electrode are sequentially arranged and the first electrode, the dielectric fiber, and the second electrode are wound multiple times in a spring structure, and a transmission line electrically connecting the induction coil and the fiber strain sensor.

[0011]

[0012] In addition, according to one embodiment of the present invention, the fiber strain sensor may be provided with a negative capacitive fiber-type strain sensing system comprising a sensing bundle formed by winding the first electrode, the dielectric fiber, and the second electrode sequentially once.

[0013]

[0014] In addition, according to one embodiment of the present invention, the fiber strain sensor may be provided as a negative electrostatic fiber-type strain sensing system in which a flexible insulating material is coated on the outer surface.

[0015]

[0016] In addition, according to one embodiment of the present invention, a negative capacitive fiber strain sensing system may be provided, wherein the fiber strain sensor is configured such that when tension is applied to one sensing bundle and another sensing bundle adjacent to it, the one sensing bundle and the other sensing bundle are spaced apart.

[0017]

[0018] In addition, according to one embodiment of the present invention, a negative capacitive fiber strain sensing system may be provided, wherein when the tension acting on one sensing bundle and another sensing bundle adjacent to it is released, the position of the separated one sensing bundle and the other sensing bundle is restored.

[0019]

[0020] In addition, according to one embodiment of the present invention, a negative capacitive fiber-type strain sensing system may be provided, characterized in that when one sensing bundle and another adjacent sensing bundle are spaced apart, the fiber strain sensor measures a change in capacitance by measuring a change in the distance between a first electrode of one sensing bundle and a second electrode of another sensing bundle.

[0021]

[0022] In addition, according to one embodiment of the present invention, a negative electrostatic fiber-type strain sensing system may be provided, characterized in that the first electrode and the second electrode comprise a fiber substrate and metal nanoparticles.

[0023]

[0024] In addition, according to one embodiment of the present invention, a negative electrostatic fiber-type strain sensing system may be provided, characterized in that the fiber substrate is one or more materials selected from the group consisting of polyurethane, SBS (styrene-butadiene-styrene), SEBS (styrene-ethylene-butadiene-styrene), EcoFlex, and Dragon Skin (silicone).

[0025]

[0026] In addition, according to one embodiment of the present invention, a negative electrostatic fiber-type strain sensing system may be provided, characterized in that the metal nanoparticles are one or more materials selected from the group consisting of silver (Ag) nanoparticles, copper (Cu) nanoparticles, platinum (Pt) nanoparticles, gold (Au) nanoparticles, zinc (Zn) nanoparticles, and magnesium (Mg) nanoparticles.

[0027]

[0028] In addition, according to one embodiment of the present invention, the sensing bundle may be provided with a negative electrostatic fiber-type strain sensing system comprising a hollow core formed in the center by the first electrode, dielectric fiber, and second electrode that are wound.

[0029]

[0030] In addition, according to one embodiment of the present invention, a negative electrostatic fiber-type strain sensing system may be provided, wherein the sensing bundle is configured such that when the hollow core increases, the amount of change in the spacing between adjacent sensing bundles increases.

[0031]

[0032] In addition, according to one embodiment of the present invention, a negative capacitive fiber-type strain sensing system may be provided, wherein the sensing bundle is configured such that when the deflection angle of the sensing bundle increases, the amount of change in the spacing of adjacent sensing bundles increases.

[0033]

[0034] In addition, according to one embodiment of the present invention, a negative electrostatic fiber-type strain sensing system may be provided, characterized in that the insulating material is formed from at least one of PDMS (polydimethylsiloxane), Ecoflex, Dragon skin (silicon), polyurethane, SBS (styrene-butadiene-styrene), SEBS (styrene-ethylene-butadiene-styrene), PPC (Polypropylene carbonate), PGS (Poly glycerol sebacate), POC (Poly octanediol-co-citrate), POMaC (Poly(octamethylene maleate (anhydride) citrate)), PLCL (Poly(L-lactide-co-ε-caprolactone)), and PGCL (Poly(glycolide-co-caprolactone)).

[0035]

[0036] In addition, according to one embodiment of the present invention, a negative capacitive fiber-type strain sensing system may be provided, characterized in that the induction coil and the transmission line are formed from the same stretchable conductive fiber as the first electrode and the second electrode of the fiber strain sensor.

[0037]

[0038] In addition, according to one embodiment of the present invention, a negative capacitive fiber-type strain sensing system may be provided, further comprising a spike connected to the rear end of the fiber strain sensor and configured to fix the fiber strain sensor within the body.

[0039]

[0040] In addition, according to one embodiment of the present invention, a negative electrostatic fiber-type strain sensing system may be provided, characterized in that the spike is formed in a conical shape.

[0041]

[0042] In addition, according to one embodiment of the present invention, a negative capacitive fiber-type strain sensing system may be provided, wherein the spike is provided with a first spike and a second spike, and the second spike is positioned between the first spike and the rear end of the fiber strain sensor.

[0043]

[0044] In addition, according to one embodiment of the present invention, a negative electrostatic fiber-type strain sensing system may be provided, comprising a coil case positioned above and below the induction coil and configured to cover the induction coil.

[0045] In the present invention, various biomechanical signals generated within the body can be measured more precisely through the amplification of wireless signals.

[0046] In addition, since the wireless signal is amplified in response to external stimuli, the problems of existing passive wireless sensing systems can be dramatically resolved, thereby maximizing the efficiency of post-operative rehabilitation and treatment.

[0047] In addition, the present invention can be utilized not only in implantable devices but also in various wearable electronic devices based on signal stimulation characteristics caused by external stimuli.

[0048] FIG. 1 is a drawing illustrating a negative electrostatic fiber-type strain sensing system according to one embodiment of the present invention.

[0049] FIG. 2 is a drawing illustrating a strain sensor of a negative capacitive fiber-type strain sensing system according to one embodiment of the present invention.

[0050] FIG. 3 is a diagram illustrating the elongation of a strain sensor of a negative capacitive fiber-type strain sensing system according to one embodiment of the present invention.

[0051] FIG. 4 is a diagram illustrating the relationship between tensile strain and change in capacitance of a negative electrostatic fiber-type strain sensing system according to one embodiment of the present invention.

[0052] FIG. 5 is a diagram illustrating the size and deflection angle of the hollow core of a sensing bundle of a negative electrostatic fiber-type strain sensing system according to one embodiment of the present invention.

[0053] FIG. 6 is a diagram illustrating the relationship between the size and capacitance of a hollow core of a sensing bundle of a negative electrostatic fiber-type strain sensing system according to one embodiment of the present invention.

[0054] FIG. 7 is a drawing illustrating a spike of a negative electrostatic fiber-type strain sensing system according to one embodiment of the present invention.

[0055] FIG. 8 is a diagram illustrating the manufacturing process of a negative electrostatic fiber-type strain sensing system according to one embodiment of the present invention.

[0056] FIG. 9 is a diagram illustrating the relationship between the amount of deformation or response time and the capacitance of a negative capacitive fiber-type strain sensing system according to one embodiment of the present invention.

[0057] FIG. 10 is a drawing illustrating a negative electrostatic fiber-type strain sensing system and a network analyzer according to one embodiment of the present invention.

[0058] FIG. 11 is a diagram illustrating the relationship between the magnitude of an external force, the frequency of the external force, and the sensing response of a negative electrostatic fiber-type strain sensing system according to one embodiment of the present invention.

[0059] FIG. 12 is a diagram illustrating the relationship between the resonance frequency and signal strength according to the strain of a negative electrostatic fiber-type strain sensing system according to one embodiment of the present invention.

[0060] FIG. 13 is a diagram illustrating the relationship between the resonance frequency, signal strength, response time, and resonance frequency according to the strain of a negative electrostatic fiber-type strain sensing system according to one embodiment of the present invention.

[0061] The advantages and features of the embodiments of the present invention, and the methods for achieving them, will become clear by referring to the embodiments described below in detail together with the accompanying drawings. However, the present invention is not limited to the embodiments described below but may be implemented in various different forms. These embodiments are provided merely to ensure that the invention is complete and to fully inform those skilled in the art of the scope of the invention, and the invention is defined only by the scope of the claims. Throughout the specification, the same reference numerals refer to the same components.

[0062] In describing the embodiments of the present invention, specific descriptions of known functions or configurations will be omitted if it is determined that such detailed descriptions could unnecessarily obscure the essence of the invention. Furthermore, the terms described below are defined in consideration of their functions in the embodiments of the present invention, and these definitions may vary depending on the intentions or practices of the user or operator. Therefore, such definitions should be based on the content throughout this specification.

[0063] Hereinafter, embodiments of the present invention will be described in detail with reference to the attached drawings.

[0064]

[0065] First, in a strain sensor (120) according to one embodiment of the present invention, the direction of the induction coil (110) may mean the front of each member, and the direction from the strain sensor (120) to the spike (140) may mean the rear of each member.

[0066]

[0067] Referring to FIGS. 1 to 13, a negative capacitive fiber-type strain sensing system (100) according to one embodiment of the present invention may include an induction coil (110), a strain sensor (120), a transmission line (130), a spike (140), etc.

[0068] FIG. 1 is a drawing illustrating a negative electrostatic fiber-type strain sensing system according to one embodiment of the present invention.

[0069] Referring to FIG. 1, the induction coil (110) can perform the function of an inductor (L) in a negative electrostatic fiber-type strain sensing system (100) and can be housed inside a coil case (111) and positioned inside the body.

[0070] To describe above, a fiber strain sensing system (100) according to one embodiment of the present invention is an electrical LCR resonant circuit, and the fiber strain sensor (120) is a capacitor (C), the induction coil (110) is an inductor (L), and the transmission line (R) (130) can perform the function of connecting the fiber strain sensor (120) and the induction coil (110).

[0071] The induction coil (110) of the fiber-type strain sensing system (100) according to one embodiment of the present invention can be inductively coupled with a leading coil provided in an external network analyzer (not shown). Here, since the inductance (L) of the coil is fixed, the resonance frequency in the RLC circuit can change according to the change in capacitance (C) measured by the fiber strain sensor (120). Accordingly, the amount of change in capacitance (C) can be measured by the fiber strain sensor (120), and the resonance frequency can also change according to the measured amount of change, and such a change in resonance frequency can be measured in real time through the external network analyzer.

[0072]

[0073] FIG. 2 is a diagram illustrating a strain sensor of a negative capacitive fiber-type strain sensing system according to one embodiment of the present invention, FIG. 3 is a diagram illustrating the elongation of a strain sensor of a negative capacitive fiber-type strain sensing system according to one embodiment of the present invention, FIG. 4 is a diagram explaining the relationship between tensile deformation and change in capacitance of a negative capacitive fiber-type strain sensing system according to one embodiment of the present invention, and FIG. 5 is a diagram illustrating the size and deflection angle of a hollow core of a sensing bundle of a negative capacitive fiber-type strain sensing system according to one embodiment of the present invention.

[0074] Referring to FIGS. 2 to 5, the fiber strain sensor (120) may be configured such that a first electrode (122), a dielectric fiber (124), and a second electrode (123) are arranged sequentially, and the first electrode (122), the dielectric fiber (124), and the second electrode (123) are wound multiple times in a spring structure.

[0075] The fiber strain sensor (120) is a fiber-based sensor, and when an external force is applied, physical deformation occurs in the sensor, and the deformation (i.e., strain) is converted into an electrical signal to measure the amount of deformation.

[0076] A fiber strain sensor (120) according to one embodiment of the present invention may be provided with a plurality of sensing bundles (121). In the fiber strain sensor (120), a first electrode (122), a dielectric fiber (124), and a second electrode (123) that are sequentially arranged and combined may be wound multiple times in a spring structure. Here, among the wound first electrode (122), dielectric fiber (124), and second electrode (123), the first electrode (122), dielectric fiber (124), and second electrode (123) wound once (or one turn) may form a single sensing bundle (121). For example, if the first electrode (122), dielectric fiber (124), and second electrode (123) are wound five times (or five turns), five sensing bundles (121) may be formed.

[0077] As described above, as a plurality of sensing bundles (121) are formed, each sensing bundle (121) may be equipped with a first electrode (122), a dielectric fiber (124), and a second electrode (123). That is, a sensing bundle (121a) may be equipped with a first electrode (122a), a dielectric fiber (124a), and a second electrode (123a) arranged sequentially, and another sensing bundle (121b) adjacent to a sensing bundle (121a) may also be equipped with a first electrode (121b), a dielectric fiber (124b), and a second electrode (123b). Additionally, the sensing bundle (121) can be formed by winding a first electrode (122), a dielectric fiber (124), and a second electrode (123), and each first electrode (122), dielectric fiber (124), and second electrode (123) of each sensing bundle (121) can be continuous. That is, the first electrode (122a) of one sensing bundle (121a) can be continuous with the first electrode (122b) of an adjacent sensing bundle (121b) (the same applies to each dielectric fiber (124) and second electrode (123)). Each sensing bundle (121) does not function in a separate form and can serve as a single sensing unit for the fiber strain sensor (120) to sense.

[0078] Additionally, a plurality of sensing bundles (121) may be formed to be in close contact with one another. For example, one sensing bundle (121a) may be formed to be in close contact with an adjacent sensing bundle (121b). Accordingly, the first electrode (121a) of one sensing bundle (121a) may be in close contact with the second electrode (123b) of an adjacent sensing bundle (121b).

[0079] Additionally, the sensing bundle (121) may have a hollow core formed in the center by the wound first electrode (122), dielectric fiber (124), and second electrode (123). Accordingly, when the fiber strain sensor (120) is deformed, the sensing bundle (121) may be allowed to shrink to some extent in the direction of the center.

[0080] Referring to FIG. 2, a first electrode (122), a dielectric fiber (124), and a second electrode (123) according to one embodiment of the present invention can be fixed in a linearly aligned state through spray coating while sequentially arranged. The first electrode (122a), the dielectric fiber (124a), and the second electrode (123a) of a sensing bundle (121a) can be formed so as not to be separated even when an external force is applied to the fiber strain sensor (120). Accordingly, when an external force is applied to the fiber strain sensor (120), the space (d1) between one sensing bundle (121a) and another sensing bundle (121b) adjacent to the sensing bundle (121a) can be separated. That is, a variation may occur in which the gap (d1) between the first electrode (122a) of one sensing bundle (121a) and the second electrode (123b) of an adjacent sensing bundle (121b) increases.

[0081] A negative electrostatic fiber strain sensing system (100) according to one embodiment of the present invention can detect an external force acting on a fiber strain sensor (120) by utilizing a variation in the spacing between sensing bundles (121).

[0082] To be more specific, when an external force is applied to the fiber-type strain sensor (120), tension may be applied to the fiber-type strain sensor (120) in the longitudinal direction of the fiber-type strain sensor (120) with respect to the central axis (i.e., the front and rear directions of the strain sensor (120). Due to the tension, the sensing bundle (121) of the fiber-type strain sensor (120) may also receive tension and undergo deformation in the longitudinal direction. Here, the first electrode (122), dielectric fiber (124), and second electrode (123) of the sensing bundle (121) are integrally combined, so it is difficult for deformation to occur in which the gap between the first electrode (122), dielectric fiber (124), or second electrode (123) increases. Accordingly, a deformation may occur in which the gap (from d0 to d1) between one of the multiple sensing bundles (121) and another sensing bundle (121b) adjacent thereto widens (or increases).

[0083] When the gap (d1) between one sensing bundle (121a) and another adjacent sensing bundle (121b) increases, the capacitance (C1) between the first electrode (122a) of one sensing bundle (121a) and the second electrode (123b) of another adjacent sensing bundle (121b) may change. The capacitance of the capacitor can be calculated by the following formula.

[0084] (ε: permittivity, A: electrode area, d: distance between electrodes, C: capacitance)

[0085]

[0086] When the sensing bundle (121) is manufactured, there may be an initial capacitance (C0) acting between the first electrode (122) and the second electrode (123). Here, with respect to the initial capacitance (C0), the permittivity (ε) is constant, and the area (A) of the first electrode and the second electrode, the distance (d) between the first electrode and the second electrode, etc., can also be maintained constant. Accordingly, the initial capacitance (C0) can be fixed.

[0087] When an external force is applied to the strain sensor (120) and the spacing (d1) between multiple sensing bundles (121) increases (when the spacing between the sensing bundles (121) changes), the capacitance (C1) between the first electrode (122a) of one sensing bundle (121a) and the second electrode (123b) of another sensing bundle (121b) adjacent thereto may also change. That is, the permittivity (ε) and the area (A) of the first electrode and the second electrode may be kept constant (or may change by a negligible difference), and as the distance between the electrodes increases, the changed capacitance (C1) may decrease.

[0088] For example, referring to FIG. 4, a negative electrostatic fiber-type strain sensor (120) according to one embodiment of the present invention may have a hollow core formed to be 500 μm, and two dielectric fibers (124) may be formed between the first electrode (122) and the second electrode (123) of a sensing bundle (121). According to FIG. 4, as the tensile strain increases due to the application of an external force, it can be seen that the capacitance of the strain sensor (120) decreases.

[0089] As capacitance decreases, the value of the wireless signal strength (Q-factor) can also change. The wireless signal strength (Q-factor) can be used to measure the signal strength and quality of a specific frequency band. The wireless signal strength (i.e., Q) can be calculated by the following equation.

[0090] (R: Resistance, L: Inductance of the coil, C: Capacitance of the capacitor)

[0091]

[0092] Here, since the inductance (L) and resistance (R) of the coil can be kept constant, the wireless signal strength can be determined by the capacitance (C). In the case of a strain sensor formed such that the capacitance increases when a stimulus or external force is continuously applied to the strain sensor, the wireless signal strength may decrease as the capacitance increases. Consequently, as the stimulus is applied to the sensor, the wireless signal also weakens, which may cause difficulties in long-term signal measurement.

[0093] On the other hand, in a strain sensor (120) according to one embodiment of the present invention, as stimulation to the sensor continues or increases, the spacing between the sensing bundles (121) may become longer, and the capacitance measured between the electrodes of the sensing bundles (121) may also decrease. Accordingly, a sensing system (100) including a fiber-type strain sensor (120) may increase the wireless signal strength as stimulation increases, and may be able to measure the signal over a long period of time.

[0094]

[0095] Referring to FIG. 5, the fiber-type strain sensor (120) according to one embodiment of the present invention may have a different amount of change in response to external stimulation depending on the shape of the sensing bundle (121).

[0096] A hollow core may be formed in the central part of the sensing bundle (121). Depending on the diameter (D) of the hollow core of the sensing bundle (121), the bias angle (α) of the sensing bundle (121), etc., the amount of change of the strain sensor (120) for the same stimulus may vary.

[0097] The diameter of the hollow core can be measured as the diameter of the cross-section along the axial direction (or longitudinal direction) of the sensing bundle (121). That is, the diameter of the hollow core does not refer to the diameter of the first electrode (122) and the second electrode (123) of the sensing bundle (121) itself, but may refer to the diameter (D) of the axial cross-section of the sensing bundle (121). Additionally, the deflection angle (α) of the sensing bundle (121) can be measured as the angle at which the sensing bundle (121) is tilted on the side of the sensing bundle (121). As the sensing bundle (121) is wound into a spring structure during the forming process, multiple sensing bundles (121) can be formed in a spiral shape. Accordingly, the first electrode (122), the second electrode (123), etc. of the sensing bundle may be tilted at a predetermined angle with respect to the central axis of the sensing bundle (121), and this angle may represent the deflection angle of the sensing bundle (121).

[0098] Here, as the diameter of the hollow core increases (i.e., from D1 to D0), the deflection angle (α) of the sensing bundle (121) may increase, and as the diameter of the hollow core decreases (i.e., from D0 to D1), the deflection angle (α) of the sensing bundle (121) may also decrease.

[0099]

[0100] FIG. 6 is a diagram illustrating the relationship between the size of the hollow core and the capacitance of the sensing bundle of a negative electrostatic fiber-type strain sensing system according to one embodiment of the present invention.

[0101] Referring to FIG. 6, it can be seen that when the diameter of the hollow core is 500 µm or 750 µm, the deflection angle of the sensing bundle (121) is relatively increased compared to when the diameter of the hollow core is formed to be 250 µm. It can be seen that as the diameter of the hollow core increases, the amount of change in the spacing of the multiple sensing bundles (121) in response to an external stimulus also increases. Accordingly, when an external stimulus is applied, the amount of change in the difference in capacitance between the multiple sensing bundles (121) may also increase. On the other hand, when the diameter of the hollow core is relatively small (or when the deflection angle is small), it can be seen that the amount of change in the spacing of the multiple sensing bundles (121) in response to an external stimulus is not large.

[0102] Looking at the graph in Fig. 6, the results described above can be confirmed. When the diameter of the hollow core is formed to be 500 µm or 750 µm, as the amount of change of the strain sensor (120) (or sensing bundle (121)) in response to external stimulation increases, the difference in capacitance measured between multiple sensing bundles (121) can also increase.

[0103] On the other hand, when the diameter of the hollow core is formed to be 250 µm, the difference in capacitance measured between multiple sensing bundles (121) may increase slightly when an external force is applied, but when an external stimulus is continuously applied, a decrease in the diameter of the hollow core may occur more significantly than a change in the spacing between multiple sensing bundles (121). To be more specific, in the case of a sensor in which the diameter of the hollow core is formed to be 250 µm, the deflection angle of the winding sensing bundle (121) may decrease due to the reduction in the size of the hollow core. In particular, when an external force is applied to a sensor in which the deflection angle of the sensing bundle (121) is formed to be about 50 degrees or less, rather than the distance between the sensing bundles (121) increasing, the sensing bundle (121) may tilt further (i.e., the deflection angle decreases further), and a phenomenon of pressing on other adjacent sensing bundles may occur. Accordingly, only the size of the entire hollow core may be reduced, and the length of the strain sensor (120) may be increased (wherein, the increase in the length of the strain sensor (120) may mean that the length in the longitudinal direction of the sensing bundle (120) increases as the deflection angle of the sensing bundle (121) itself decreases, rather than due to an increase in the length between multiple sensing bundles (121)). In addition, as the size of the hollow core decreases, a phenomenon may occur in which the distance between the electrodes of adjacent sensing bundles (121) becomes closer. As a result, the capacitance may increase, and the Q-factor of the wireless signal may decrease, so that negative characteristics may not be formed in the strain sensor (120).

[0104]

[0105] The first electrode (122) and the second electrode (123) may be formed as conductive fiber electrodes and may be stretchable conductive fibers. Each of the first electrode (122) and the second electrode (123) may include a fiber substrate and metal nanoparticles, and may be formed by dispersing metal nanoparticles in the fiber substrate.

[0106] The fiber substrate may be one or more materials selected from the group consisting of polyurethane, SBS (styrene-butadiene-styrene), SEBS (styrene-ethylene-butadiene-styrene), EcoFlex, and Dragon Skin (silicon). The metal nanoparticles may be one or more materials selected from the group consisting of silver (Ag) nanoparticles, copper (Cu) nanoparticles, platinum (Pt) nanoparticles, gold (Au) nanoparticles, zinc (Zn) nanoparticles, and magnesium (Mg) nanoparticles.

[0107] A dielectric fiber (124) may be disposed between the first electrode (122) and the second electrode (123). The distance between the first electrode (122) and the second electrode (123) may be controlled by the dielectric fiber (124). The initial capacitance may be determined according to the distance between the first electrode (122) and the second electrode (123). As previously described, even when an external stimulus is applied to the strain sensor (120), almost no deformation of the dielectric fiber (124) occurs, so the amount of change in the initial capacitance may be fixed. Accordingly, it may be determined by the width (or thickness) of the dielectric fiber (124) provided between the first electrode (122) and the second electrode (123), and according to the formula for calculating capacitance, the larger the width (or thickness) of the dielectric fiber (124), the lower the initial capacitance may be. In addition, the initial capacitance may be determined according to the number of dielectric fibers (124) provided. That is, as the number of dielectric fibers (124) increases, the initial capacitance may decrease.

[0108] The transmission line (130) can electrically connect the induction coil (110) and the fiber strain sensor (120). It may be formed from the same stretchable conductive fiber as the first electrode (121), second electrode (123), etc. of the fiber strain sensor (120). Changes in the capacitive response of the fiber strain sensor (120) of the present invention directly affect the shift in the resonant frequency of the LCR system and enable wireless reading. In addition, regarding the material of the transmission line (130), it will be substituted with the example previously provided.

[0109]

[0110] FIG. 7 is a drawing illustrating a spike of a negative electrostatic fiber-type strain sensing system according to one embodiment of the present invention.

[0111] Referring to FIG. 7, the spike (140) may be provided to be connected to the rear end of the fiber strain sensor (120) and may fix the fiber strain sensor (120) to a suture location inside the body. The spike (140) may be formed in a conical shape or the like so that a tip is formed on the rear side of the fiber strain sensor (120). The frictional force between the fiber strain sensor (120) and the skin, etc., on which the fiber strain sensor is placed may be reduced by the tip formed on the spike (140). Accordingly, when an external stimulus acts on the fiber strain sensor (120), the fiber strain sensor (120) can be stably stretched.

[0112] The spike (140) may be provided with a first spike (141) and a second spike (142), and the second spike (142) may be positioned between the first spike (141) and the rear end of the fiber strain sensor. A suture may be connected to the rear end of the first spike (141) so that the fiber strain sensor (120), etc., is fixed inside the body, and then the suture may be removed. The second spike (142) may connect the first spike (141) and the fiber strain sensor (120). As previously exemplified, the first spike (141) and the second spike (142) may be formed in a conical shape, etc.

[0113]

[0114] FIG. 8 is a diagram illustrating the manufacturing process of a negative electrostatic fiber-type strain sensing system according to one embodiment of the present invention.

[0115] Referring to FIG. 8, a fiber strain sensor (120) according to one embodiment of the present invention can be manufactured in the following process. First, a first electrode (122), a dielectric fiber (124), and a second electrode (123) can be sequentially arranged in a line. The first electrode (122), dielectric fiber (124), and second electrode (123) arranged in a line can be fixed through a polymer solution-based spray coating. Additionally, the first electrode (122), dielectric fiber (124), and second electrode (123) arranged in a line can be insulated by performing a spray coating on them. When a first electrode (122), dielectric fiber (124), and second electrode (123) are wound in a row to form a plurality of sensing bundles (121), electrical contact may occur between the electrodes that come into contact with each other in the sensing bundles (121). In this case, a short circuit may occur in the strain sensor (120), and the strain sensor (120) may not operate normally. To prevent such a phenomenon, a polymer solution-based spray coating is applied to the first electrode (122), dielectric fiber (124), and second electrode (123) that are aligned in a row, thereby preventing a short circuit from occurring between the formed sensing bundles (121).

[0116] In a spray coating according to one embodiment of the present invention, polymeric materials such as PU (Polyurethane), SBS (Poly(styrene-butadiene-styrene)), SEBS (Styrene-Ethylene-Butylene-Styrene), PVDF (Polyvinylidene fluoride), PCL (Polycaprolactone), PPC (Polypropylene carbonate), PLLA (Poly(L-lactic acid)), PVA (Poly(vinyl alcohol)), and PAA (Poly(acrylic acid)) may be used.

[0117]

[0118] Next, the first electrode (122), dielectric fiber (124), and second electrode (123) arranged around the sacrificial chamber can be wound. The arranged first electrode (122), dielectric fiber (124), and second electrode (123) can be wound in multiple circuits while forming a spiral shape with a spring structure. Here, the first electrode (122), dielectric fiber (124), and second electrode (123) wound one full turn can be formed into a single sensing bundle (121). Additionally, during the process of forming the sensing bundle (121) (i.e., the process of winding the first electrode (122), dielectric fiber (124), and second electrode (123)), one sensing bundle (121a) can be formed to be in close contact with an adjacent sensing bundle (121b). Accordingly, multiple sensing bundles (121) can be formed by being densely arranged in a row.

[0119] Next, a flexible polymer layer may be coated on the sensing bundle (121). The flexible polymer layer may be provided as an insulating material. Here, the insulating material may be formed from at least one of PDMS (polydimethylsiloxane), Ecoflex, Dragon skin (silicone), polyurethane, SBS (styrene-butadiene-styrene), SEBS (styrene-ethylene-butadiene-styrene), PPC (Polypropylene carbonate), PGS (Poly glycerol sebacate), POC (Poly octanediol-co-citrate), POMaC (Poly(octamethylene maleate (anhydride) citrate)), PLCL (Poly(L-lactide-co-ε-caprolactone)), and PGCL (Poly(glycolide-co-caprolactone)). Since a flexible polymer layer is coated on a plurality of sensing bundles (121), when tension is applied to the strain sensor (120), the flexible polymer layer can be stretched and the sensing bundles (121) can also be stretched. Additionally, when the tension is removed, the flexible polymer layer and the sensing bundles (121) can be restored to their original shape.

[0120] Next, the sacrificial chamber can be removed. The sacrificial chamber supports the formation of the sensing bundle (121) during the manufacturing process and can be removed so that only the sensing bundle (121) remains. The sacrificial chamber can be formed from a polymer, silicone, etc.

[0121]

[0122] Referring to FIGS. 9 to 13, a performance evaluation of a negative electrostatic fiber-type strain sensing system (100) according to one embodiment of the present invention can be observed.

[0123] FIG. 9 is a diagram illustrating the relationship between the amount of deformation or response time and capacitance of a negative capacitive fiber-type strain sensing system according to one embodiment of the present invention; FIG. 10 is a diagram illustrating a negative capacitive fiber-type strain sensing system and a network analyzer according to one embodiment of the present invention; FIG. 11 is a diagram illustrating the relationship between the magnitude of an external force, the frequency of the external force, and the sensing response of a negative capacitive fiber-type strain sensing system according to one embodiment of the present invention; FIG. 12 is a diagram illustrating the relationship between the resonance frequency and signal strength according to the strain of a negative capacitive fiber-type strain sensing system according to one embodiment of the present invention; and FIG. 13 is a diagram illustrating the relationship between the resonance frequency and signal strength, and response time and resonance frequency according to the strain of a negative capacitive fiber-type strain sensing system according to one embodiment of the present invention.

[0124] FIG. 9(a) is a graph showing the change in capacitance according to the strain of the strain sensor (120) when an external stimulus is applied to the fiber strain sensor (120) or when the applied stimulus is removed. When an external stimulus is applied to the fiber strain sensor (120), the fiber strain sensor (120) can be stretched, and when the external stimulus is removed, the fiber strain sensor (120) can be released. Through FIG. 9(a), it can be seen that the paths of stretching and releasing of the fiber strain sensor (120) are nearly identical, and the change in capacitance also changes within a certain range (about 0.03F).

[0125] Additionally, FIG. 9(b) is a graph showing the sensitivity of the response of the fiber strain sensor (120) when a deformation of about 0.5% (i.e., about 0.5% deformation relative to the maximum deformation amount) occurs in the fiber strain sensor (120). When an external stimulus that causes a minute deformation is applied to the fiber strain sensor (120) and the external stimulus is removed, the change in capacitance according to the time during which the fiber strain sensor (120) is stretched or restored can be observed. Referring to FIG. 9(b), the fiber strain sensor (120) is maintained at a constant stretching or restoration time of about 5 seconds, and it can be observed that the change in capacitance during the stretching or restoration process also changes within a constant level range (about 0.03F). Accordingly, it can be confirmed that the fiber strain sensor (120) is formed with high sensitivity capable of precisely measuring even a small deformation of about 0.5%.

[0126] Additionally, as shown in FIG. 9 (a) and (b), the fiber strain sensor (120) according to one embodiment of the present invention has a portion of error that occurs during the restoration process after stretching. However, this is a low level of hysteresis compared to a general sensor, and if Ecoflex or dragon skin with high elasticity is used, it can have negligible hysteresis.

[0127]

[0128] Referring to FIG. 10, a negative strain sensing system (100) according to one embodiment of the present invention can measure through inductive coupling between an induction coil in the strain sensing system and a reading coil attached to a network analyzer. The resonant frequency of the circuit can be measured in real time through the network analyzer, and this resonant frequency value can be influenced by L and C according to the above resonant frequency formula. However, since the inductance of the coil constituting the circuit is fixed, the change in resonant frequency during measurement can be determined only by the change in the sensor.

[0129] In conventional capacitive sensors, the capacitance of the sensor increases when strain is applied. At this time, the wireless signal strength (Q-factor) of the sensing system may be inversely proportional to the increase in capacitance, so the signal weakens as the sensor is stimulated, which can interfere with long-term signal measurement.

[0130] On the other hand, since the capacitance of

[0131]

[0132] Referring to FIG. 11, the stability of the response of the fiber strain sensor (120) according to the magnitude, frequency, etc. of the stimulus can be confirmed. Looking at FIG. 11 (a), as the intensity of the external stimulus changes, the fiber strain sensor (120) can be deformed by approximately 2.5%, 5%, 10%, and 20%. In each case, the measured changed capacitance is approximately 0.1 (F), 0.15 (F), 0.2 (F), and 0.25 (F). Even if each stimulus is applied multiple times, the capacitance can be measured at a constant value. Accordingly, it can be confirmed that the fiber strain sensor (120) according to one embodiment of the present invention responds stably even when the magnitude of the external stimulus increases.

[0133] Additionally, referring to FIG. 11(b), it can be seen that for the same stimulus, the fiber strain sensor (120) responds with a constant period for each stimulus as the frequency of the stimulus changes. That is, it can be seen that the fiber strain sensor (120) responds with a constant period for the same frequency. Accordingly, it can be seen that the fiber strain sensor (120) according to one embodiment of the present invention responds stably to each frequency even if the frequency of external stimulus increases.

[0134] In addition, referring to Fig. 11 (c), it can be seen that even when a deformation of about 10% is applied to the sensor 1,000 times to test the durability of the sensor, the response of the sensor is measured without degradation.

[0135]

[0136] Referring to Fig. 12, the process of measuring the resonance frequency and wireless signal strength between the induction coil (i.e., the sensing coil) of the strain sensing system and the reading coil attached to the network analyzer can be observed. As the magnitude of the external force increases, the amount of strain deformation also increases, and the resonance frequency corresponding to each magnitude of the external force can be identified. That is, when an external force is applied, it can be observed that the resonance frequency of the sensing system increases and the signal strength increases simultaneously. In addition, as the magnitude of the external force increases, it can be observed that the curve changes abruptly, confirming that the sensitivity of the response also increases with the magnitude of the external force.

[0137]

[0138] Referring to Fig. 13, the wireless signal strength (Q-factor) of the system was calculated by changing the resonant frequency to verify the wireless signal strength, and as shown in Fig. 13 (a), it can be seen that the wireless signal strength increases as strain (tensile deformation) is applied. In addition, as shown in Fig. 13 (b), it can be seen that the change in resonant frequency becomes observable even when a small deformation of 0.5% occurs in the sensor.

[0139]

[0140] Although various embodiments of the present invention have been presented and described in the above description, the present invention is not necessarily limited thereto, and those skilled in the art will readily understand that various substitutions, modifications, and changes are possible within the scope of the technical concept of the present invention.

Claims

1. An induction coil that transmits and receives electrical stimulation signals, and A fiber strain sensor formed by sequentially arranging a first electrode, a dielectric fiber, and a second electrode, and winding the first electrode, the dielectric fiber, and the second electrode multiple times in a spring structure, and A transmission line electrically connecting the induction coil and the fiber strain sensor. A negative capacitive fiber-type strain sensing system including 2. In Paragraph 1, The fiber strain sensor above is, A sensing bundle formed by winding the first electrode, the dielectric fiber, and the second electrode, which are arranged sequentially, once. A negative capacitive fiber-type strain sensing system including 3. In Paragraph 2, The fiber strain sensor above is, The outer surface is coated with a flexible insulating material, Negative electrostatic fiber strain sensing system.

4. In Paragraph 3, The fiber strain sensor above is, When tension is applied to one sensing bundle and another adjacent sensing bundle, the one sensing bundle and the other sensing bundle are spaced apart. Negative electrostatic fiber strain sensing system.

5. In Paragraph 4, The fiber strain sensor above is, When the tension acting on one sensing bundle and another adjacent sensing bundle is released, the positions of the separated one sensing bundle and the other sensing bundle are restored. Negative electrostatic fiber strain sensing system.

6. In Paragraph 4, The fiber strain sensor above is, When one of the above-mentioned sensing bundles is spaced apart from another adjacent sensing bundle, the change in capacitance is measured by measuring the change in the distance between the first electrode of one of the above-mentioned sensing bundles and the second electrode of another of the above-mentioned sensing bundles. Negative electrostatic fiber strain sensing system.

7. In Paragraph 1, The first electrode and the second electrode above are, Characterized by including a fiber substrate and metal nanoparticles, Negative electrostatic fiber strain sensing system.

8. In Paragraph 7, The above fiber substrate is, Characterized by being one or more materials selected from the group consisting of polyurethane, SBS (styrene-butadiene-styrene), SEBS (styrene-ethylene-butadiene-styrene), EcoFlex, and Dragon Skin (silicone). Negative electrostatic fiber strain sensing system.

9. In Paragraph 7, The above metal nanoparticles are, Characterized by being one or more materials selected from the group consisting of silver (Ag) nanoparticles, copper (Cu) nanoparticles, platinum (Pt) nanoparticles, gold (Au) nanoparticles, zinc (Zn) nanoparticles, and magnesium (Mg) nanoparticles. Negative electrostatic fiber strain sensing system.

10. In Paragraph 2, The above sensing bundles are, A hollow core formed in the center by the wound first electrode, dielectric fiber, and second electrode A negative capacitive fiber-type strain sensing system including 11. In Paragraph 10, The above sensing bundles are, When the above hollow core increases, the amount of change in the spacing of the adjacent sensing bundles increases, provided Negative electrostatic fiber strain sensing system.

12. In Paragraph 2, The above sensing bundles are, When the bias angle of the above-mentioned sensing bundle increases, the amount of change in the spacing of the adjacent above-mentioned sensing bundle increases, Negative electrostatic fiber strain sensing system.

13. In Paragraph 3, The insulating material is characterized by being formed from at least one of PDMS (polydimethylsiloxane), Ecoflex, Dragon skin (silicone), polyurethane, SBS (styrene-butadiene-styrene), SEBS (styrene-ethylene-butadiene-styrene), PPC (Polypropylene carbonate), PGS (Poly glycerol sebacate), POC (Poly octanediol-co-citrate), POMaC (Poly(octamethylene maleate (anhydride) citrate)), PLCL (Poly(L-lactide-co-ε-caprolactone)), and PGCL (Poly(glycolide-co-caprolactone)). Negative electrostatic fiber strain sensing system.

14. In Paragraph 1, The above induction coil and the above transmission line are, Characterized by being formed of the same stretchable conductive fiber as the first electrode and the second electrode of the fiber strain sensor. Negative electrostatic fiber strain sensing system.

15. In Paragraph 1, A spike connected to the rear end of the fiber strain sensor and configured to fix the fiber strain sensor within the body. A negative capacitive fiber-type strain sensing system further comprising 16. In Paragraph 15, The above spike is, Characterized by being formed in a conical shape. Negative electrostatic fiber strain sensing system.

17. In Paragraph 15, The above spike is, A first spike and a second spike, wherein the second spike is positioned between the first spike and the rear end of the fiber strain sensor. Negative electrostatic fiber strain sensing system.

18. In Paragraph 1, A coil case positioned above and below the induction coil and configured to cover the induction coil. A negative capacitive fiber-type strain sensing system including

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