Power-source-less implantable energy harvester

Abstract

The present invention relates to an implantable energy harvester. According to the present invention, a coiled carbon nanotube yarn electrode is used as a working electrode constituting the energy harvester, wherein a portion of one end of the working electrode is fixed inside a housing and a portion of the other end is exposed outside the housing, so that the energy harvester, when attached to a heart, facilitates cardiac motion by applying electrical stimulation to the surface of the heart through exposed electrodes by means of electrical energy harvested from strain changes in the working electrode caused by cardiac motion without requiring a power source, and thus can be usefully employed as a power-source-less heart pacemaker and further applied to in vivo electrical stimulation therapy.

Description

Powerless implantable energy harvester

[0001] The present invention relates to an energy storage device, and more specifically, to an energy harvester for harvesting electrical energy from mechanical deformation.

[0002] Implantable cardiac electronic devices (CIEDs), such as implantable pacemakers, cardioverter-defibrillators, neurostimulators, and mechanical circulatory support devices, have contributed significantly to the treatment of various cardiovascular diseases, including arrhythmias, ventricular fibrillation, and heart failure. Pacemakers detect abnormal heart activity and deliver electrical pulses to heart tissue to restore a normal heart rhythm.

[0003] CIEDs can replace the function of our body's natural pacemaker. While medical device technology is advancing rapidly in this way, power supply for CIEDs remains a critical issue.

[0004] Currently, lithium-ion batteries are used as the power source for CIEDs. However, there is a risk that the device may malfunction due to battery depletion. Additionally, replacing the device every 4 to 10 years can pose a risk to the patient during every surgery.

[0005] Accordingly, to overcome the limitations of CIED batteries, efforts are being made to improve energy sources to enhance biocompatibility and avoid frequent replacement surgeries; however, alternative biological pacemaker approaches that have shown good results in preclinical trials have not yet become clinical alternatives.

[0006] Meanwhile, energy harvesters that generate energy from the environment are considered promising tools for sustainability because limited device lifespans are less of a concern. The continuous, constant, and periodic movements of body parts or organs, such as heart muscle, diaphragm, blood flow, or contractile muscles, represent an attractive source for energy harvesting due to their infinite nature throughout our lifetimes. In particular, harvesting energy from the heartbeat, capable of generating about 1 watt of mechanical performance, is promising due to periodic changes in muscle form.

[0007] Conventionally, various types of energy harvesters equipped with piezoelectric or triboelectric elements have been designed and applied to the cardiac environment. The collected electrical energy was used for various purposes, such as powering CIEDs, directly moving the heart, or monitoring heart conditions. However, these devices had problems such as being too rigid or bulky, and failing to supply sufficient energy required for CIEDs.

[0008] Accordingly, there is a need to develop an energy harvester that is compact enough to be implantable in the body and capable of converting the mechanical energy of a heartbeat into electrical energy without a power source.

[0009] The problem that the present invention aims to solve is to provide a power-free, implantable energy harvester.

[0010] To solve the above problem, one aspect of the present invention provides a power-free implantable energy harvester. The power-free implantable energy harvester comprises: a closed housing having a hollow interior and having biocompatibility and elasticity; an operating electrode disposed inside the housing, with a portion exposed to the outside of the housing; a counter electrode disposed inside the housing, with a portion exposed; a separator disposed inside the housing and surrounding the counter electrode to separate the operating electrode and the counter electrode; an electrolyte filling the interior of the housing; and connecting portions formed at both ends of the housing for coupling to an organ within the body.

[0011] The above working electrode and the above counter electrode can both be formed such that a portion is immersed in the electrolyte and a portion is exposed outside the housing.

[0012] The above housing may be a silicone tube.

[0013] The above separator may be a porous polymer tube.

[0014] The above counter electrode may be a carbon nanotube yarn in which the carbon nanotube sheet is twisted.

[0015] When the above-mentioned power-free implantable energy harvester is attached to the surface of the heart, the spring constant (SI) of the coiled carbon nanotube yarn may be greater than 0.38 and less than 0.77.

[0016] The above-mentioned implantable energy harvester is characterized by attaching to the surface of the heart and stimulating the heart with electricity generated by the tension and contraction associated with the heartbeat.

[0017] According to the present invention, a coiled carbon nanotube yarn electrode is used in the working electrode constituting the energy harvester, wherein a portion of the end of the working electrode is fixed inside the housing and a portion of the other end is exposed outside the housing, so that when the energy harvester is attached to the heart, electrical energy harvested from the strain change of the working electrode due to the movement of the heart without the need for a power source can be used to stimulate the surface of the heart again through the exposed electrode, thereby helping the heart movement, so that it can be usefully used as a power-free heart pacemaker, and furthermore, can be applied to in vivo electrical stimulation therapy.

[0018] FIG. 1 is a schematic diagram showing the structure of an energy harvester according to one embodiment of the present invention.

[0019] FIG. 2 is a drawing showing an energy harvester manufactured according to one embodiment of the present invention.

[0020] FIG. 3 is a mechanism showing the operating principle of an energy harvester when the energy harvester is attached to the heart according to one embodiment of the present invention.

[0021] FIG. 4 is a graph showing the change in open-circuit voltage (OCV) within a general range of left ventricular longitudinal strain according to the spring constant of a coiled carbon nanotube yarn working electrode in an energy harvester according to one embodiment of the present invention.

[0022] FIG. 5 is a graph showing the change in OCV when a strain deformation of 20% is applied to the working electrode in an open-type two-electrode system according to one comparative example of the present invention and a closed-type energy harvester according to one embodiment.

[0023] FIG. 6 is a graph showing the change in OCV according to the number of connected harvesters and the change in strain when the harvesters are connected in series in an energy harvester according to one embodiment of the present invention.

[0024] FIG. 7 is a graph showing the change in performance (OCV, peak power, and matching impedance) of an energy harvester according to one embodiment of the present invention as a function of tensile frequency.

[0025] FIG. 8 is a graph showing the change in OCV according to the number of cycles when performing a cycle of tension and contraction with 20% strain in an energy harvester according to one embodiment of the present invention.

[0026] FIG. 9 is a graph showing the strain change of the energy harvester during the systole and diastolic phases of an ex vivo artificial heart rate system when an energy harvester according to one embodiment of the present invention is installed in an ex vivo artificial heart rate system.

[0027] FIG. 10 is a graph showing the change in open circuit voltage (OCV) and short circuit current (SCC) of an energy harvester according to the change in strain of the energy harvester during systole and diastole in an ex vivo artificial heartbeat system according to an embodiment of the present invention.

[0028] FIG. 11 is a graph showing the OCV generated by various strains in the general range of left ventricular longitudinal strain of an ex vivo artificial heartbeat system in an energy harvester according to one embodiment of the present invention.

[0029] FIG. 12 is a graph showing the OCV generated according to the heart rate frequency in the general range of left ventricular longitudinal strain of an ex vivo artificial heart rate system in an energy harvester according to one embodiment of the present invention.

[0030] FIG. 13 is a graph showing the change in peak power and average power generated according to the load resistance connected to the energy harvester in the general range of left ventricular longitudinal strain of an ex vivo artificial heartbeat system in an energy harvester according to one embodiment of the present invention.

[0031] FIG. 14 is a graph showing the OCV, peak power, and energy per cycle generated in an energy harvester according to a heart rate frequency in a general range of left ventricular longitudinal strain of an ex vivo artificial heart rate system in an energy harvester according to one embodiment of the present invention.

[0032] FIG. 15 is a photograph showing the strain change of an energy harvester according to the systole and diastole of a heartbeat when an energy harvester according to one embodiment of the present invention is installed in the heart of a pig.

[0033] FIG. 16 is a graph showing continuous OCV output values ​​generated from four connected energy harvesters according to periodic heartbeat movements when an energy harvester according to one embodiment of the present invention is installed in the heart of a pig.

[0034] FIG. 17 is a graph showing the OCV generated in the energy harvester during the systole and diastolic phases of the heartbeat when an energy harvester according to one embodiment of the present invention is installed in the heart of a pig.

[0035] FIG. 18 is a mapping analysis diagram showing that when an energy harvester according to one embodiment of the present invention is installed in the heart of a pig, the electricity generated stimulates the left ventricle (LV) to induce an electrical signal.

[0036] FIG. 19 is a diagram showing the effect on the heart muscle when the heart is paced with electricity generated when an energy harvester according to one embodiment of the present invention is installed in the heart of a pig.

[0037] Hereinafter, embodiments of the present invention will be described in detail with reference to the attached drawings. In describing the present invention, specific descriptions of related known functions or configurations will be omitted if it is determined that such detailed descriptions may unnecessarily obscure the essence of the present invention. Furthermore, the terms used in this specification are used to appropriately express preferred embodiments of the present invention, and these may vary depending on the intentions of the user or operator, or the conventions of the field to which the present invention belongs. Accordingly, the definitions of these terms should be based on the content throughout this specification.

[0038] Identical reference numerals in each drawing indicate identical components.

[0039] Throughout the specification, when it is stated that a component is located "on" another component, this includes not only cases where a component is in contact with another component, but also cases where another component exists between the two components.

[0040] Throughout the specification, when a part is described as "comprising" a certain component, this means that, unless specifically stated otherwise, it does not exclude other components but may include additional components.

[0041] Terms such as "approximately" and "substantially," used throughout the specification, are used to mean at or near the stated value when material tolerances are presented in the stated sense, and are used to prevent unscrupulous infringers from unfairly exploiting the disclosed content in which precise or absolute values ​​are mentioned to aid in understanding the present invention.

[0042] In this specification, "pacing" means delivering electrical stimulation to the heart through a device.

[0043]

[0044] One aspect of the present invention provides a power-free, implantable energy harvester.

[0045] FIG. 1 is a schematic diagram of a power-free implantable energy harvester according to one embodiment of the present invention, and FIG. 2 is a photograph showing the actual fabrication of the power-free implantable energy harvester.

[0046] Referring to FIGS. 1 and 2, the power-free implantable energy harvester (100) comprises: an operating electrode (10); a counter electrode (20); a separator (30); an electrolyte (40); a housing (50) that accommodates the operating electrode, the counter electrode, the separator, and the electrolyte; and a connection part (60) located at the end of the housing.

[0047] Hereinafter, the power-free implantable energy harvester according to the present invention will be described in detail by component.

[0048]

[0049] In the power-free implantable energy harvester of the present invention, the operating electrode (10) is characterized by comprising a coiled carbon nanotube yarn in which a carbon nanotube sheet is twisted and coiled.

[0050] The above-mentioned coiled carbon nanotube yarn is also called a carbon nanotube twistron, and can harvest electricity by electrically converting the voltage difference generated by the change in electrochemical capacitance caused by the application of length deformation of the carbon nanotube coil.

[0051] The above-described coiled carbon nanotube yarn can be formed by stacking and twisting multiple carbon nanotube sheets, for example, 3 to 20 sheets, to form a spring-shaped coiled yarn. Specifically, the carbon nanotube sheets may be multi-walled carbon nanotube sheets, which can be manufactured from a carbon nanotube forest formed by Chemical Vapor Deposition (CVD). In one embodiment of the present invention, the carbon nanotube sheets are stacked 3 to 20 sheets to form a yarn through spinning, then twisted by 30 to 50 turns / cm to form a twisted structure, and then twisted by 60 to 80 turns / cm to manufacture a coiled yarn with an over-twisted structure in which a layer-by-layer structure and multiple pores are formed internally.

[0052] The carbon nanotube (CNT) mentioned above is a novel material in which carbon atoms are arranged in a hexagonal tube shape. It has a one-dimensional structure with a thickness of several nanometers and a length ranging from several micrometers to several millimeters. Since carbon nanotubes possess electrical conductivity similar to copper, thermal conductivity equal to diamond, and strength superior to steel, they can be effectively utilized as electrodes for energy harvesters by taking advantage of these excellent electrical, thermal, and mechanical properties. This coiled carbon nanotube yarn electrode is formed by creating a yarn from the carbon nanotube sheets through a spinning process, and then forming it into a coil shape through a twisting and coiling process, thereby allowing it to stretch well in the tensile direction when subjected to tension.

[0053] At this time, when the coiled carbon nanotube yarn electrode is applied to an organ in the body, the spring constant must be adjusted so that it stretches to be optimized for the level of tension of the organ in the body. For example, when applied to the heart, it is desirable to adjust the spring constant (SI) of the coil so that the coiled carbon nanotube yarn stretches by the tension of the heart surface according to the heartbeat.

[0054] The above-described working electrode is connected to the uppermost and lowermost parts of the housing in the direction in which the housing described below is stretched, so that it can be stretched together with the housing when the housing is stretched. When the above-described power-free implantable energy harvester is attached to the surface of the heart, the general range (GLS) of the left ventricular longitudinal strain due to the heartbeat is 10% to 30%, so the elongation range of the working electrode may be limited to 30% or less, and the spring constant (SI) of the working electrode, expressed by the following mathematical formula 1, may be greater than 0.38 and less than 0.77.

[0055] [Mathematical Formula 1]

[0056] Spring constant (SI) = {(coil outer diameter + coil inner diameter) / 2} / yarn diameter

[0057]

[0058] The above method for manufacturing a coiled carbon nanotube yarn working electrode comprises the steps of: spinning a carbon nanotube sheet into a carbon nanotube yarn (S10); twisting the spun carbon nanotube yarn to form a yarn with a twisted structure (S20); and twisting the carbon nanotube yarn with the twisted structure to form a carbon nanotube yarn coated with a charged coating material having a coiled structure (S30).

[0059] First, step S10 is the step of spinning the carbon nanotube sheet into carbon nanotube yarn.

[0060] The spinning step described above is a step of making carbon nanotube sheets into carbon nanotube yarn, i.e., thread, and methods commonly used in the industry may be used. For example, (1) tow spinning, which inserts a twist into an oriented yarn obtained by collapsing the sheet using lateral pressure (or liquid-based densification), or (2) funnel spinning, which is spun by pulling and twisting along the axis of a cylindrical CNT forest (or a CNT forest arranged in a cylindrical shape). Additionally, methods such as floating-catalyst-synthesizing web spinning and acetic acid-based carbon nanotube spinning may be used.

[0061] At this time, while a porous carbon nanotube sheet with a planar or multilayer planar shape may be purchased directly, it is preferable to use a carbon nanotube sheet manufactured by a drawing method from a carbon nanotube forest. This is because the carbon nanotube sheet formed in this way has a planar structure and contains empty spaces between the carbon nanotube fibers constituting the sheet, thereby providing a large surface area capable of bonding with the coating material described later.

[0062]

[0063] Next, step S20 is the step of twisting the spun carbon nanotube yarn to form a yarn with a twisted structure.

[0064] The twisting process of applying twist to the carbon nanotube yarn manufactured in step S10 above to form a yarn with a twisted structure may be performed by rotating both ends of the carbon nanotube yarn in opposite directions, or by fixing both ends and rotating only the opposite end; that is, any material capable of imparting twist to the carbon nanotube yarn may be used without limitation, and the present invention is not limited by the process or device for implementing it. The number of twists applied in the twisting process may be 30 to 50 turns / cm.

[0065] The carbon nanotube yarn is uniformly twisted along the length direction, and the carbon nanotube yarn uniformly twisted along the length direction can have a bias angle represented by the following mathematical formula 2 uniformly distributed along the length direction.

[0066] [Mathematical Formula 2]

[0067] Bias Angle (˚) = The angle formed by the length direction and the twist direction of the yarn

[0068] The above bias angle may be 20 to 56˚.

[0069] The bias angle of the carbon nanotube yarn aligned in the above length direction may be less than 10°.

[0070]

[0071] Next, step S30 is a step of twisting the carbon nanotube yarn of the twisted structure to form a carbon nanotube yarn having a coiled structure and coated with a charged coating material.

[0072] The above step can form an over-twisted, coiled carbon nanotube yarn by performing a twisting process on the twisted carbon nanotube yarn with the above twisted structure at a number of turns (60 to 80) / cm.

[0073] The above coiled carbon nanotube yarn working electrode is partially fixed inside the housing, while partially exposed outside the housing to come into contact with internal organs, such as the surface of the heart.

[0074]

[0075] In the power-free implantable energy harvester of the present invention, the counter electrode (20) is the counter electrode of the coiled carbon nanotube yarn working electrode (10) and can be made of a material that has high conductivity and sufficient capacity. For example, the counter electrode (20) can be a conductive metal such as platinum or a conductive material such as carbon nanotubes.

[0076] The above counter electrode (20) is manufactured to be non-stretchable to prevent the cancellation of the open circuit voltage (OCV) signal generated by the expansion of the operating electrode, as it would cancel out the open circuit voltage (OCV) signal generated by the expansion of the operating electrode if it were to expand together with the operating electrode. For example, the above counter electrode (20) may use a carbon nanotube yarn in which a carbon nanotube sheet is twisted, and since the twisted carbon nanotube yarn is as described above regarding the operating electrode, a detailed description is omitted. The above counter electrode is positioned parallel to the operating electrode but is fixed only to a part of the end inside the housing to prevent expansion, and a part is exposed outside the housing to come into contact with an internal organ, such as the surface of the heart.

[0077]

[0078] In the power-free implantable energy harvester of the present invention, the separator (30) acts as an insulating membrane that separates the working electrode (10) and the counter electrode (20) so that they do not come into contact with each other for the stability of the energy harvester, and allows only electrolyte ions to pass through the pores, and can be formed in a shape that surrounds the counter electrode.

[0079] The type of the above separator (30) is not limited, but it may be a porous polymer tube, for example, a nylon fiber tube may be used.

[0080]

[0081] In the power-free implantable energy harvester of the present invention, the electrolyte (40) may surround the working electrode (10) and the counter electrode (20). For example, the working electrode (10) and the counter electrode (20) may be immersed in the electrolyte (40). Additionally, the electrolyte (40) may fill the interior of the housing (50) described later.

[0082] According to one embodiment, the electrolyte may be a liquid electrolyte or a solid electrolyte. For example, the electrolyte may include physiological saline, i.e., NaCl, for stability in the body. According to one embodiment, the concentration of the electrolyte may be greater than 0.01 M and less than 1 M. Additionally, the temperature of the electrolyte may be 36 ℃ to 37 ℃, which is a temperature similar to body temperature.

[0083] When the electrolyte (40) is provided to the above-mentioned operating electrode (10) and counter electrode (20), if the operating electrode (10) is stretched or contracted by an external force, a self-potential difference is generated between the operating electrode (10) and the counter electrode (20), and a voltage can be formed by the self-potential difference. That is, a voltage having a magnitude equal to the self-potential difference can be formed between the operating electrode (10) and the counter electrode (20).

[0084]

[0085] In the power-free implantable energy harvester of the present invention, the housing (50) has a hollow interior to accommodate the working electrode (10), the counter electrode (20), the separator (30), and the electrolyte (40), and has a closed exterior seal for implantation within the body. The housing (50) may include a material that is biocompatible for implantation within the body and has elasticity for attachment to an organ that performs an elastic action within the body, such as a silicone tube, but is not limited thereto.

[0086]

[0087] In the power-free implantable energy harvester of the present invention, the connecting portion (60) is formed at both ends of the housing (50) to attach and connect to an internal organ after the energy harvester is inserted into the body. A fixing groove (hole) for fixing to an internal organ through a fixing unit may be formed in the connecting portion.

[0088]

[0089] FIG. 3 is a mechanism showing the operating principle of an energy harvester when the energy harvester is attached to the heart according to one embodiment of the present invention.

[0090] Referring to FIG. 3, when the energy harvester according to the present invention is attached to the heart, when the heart beat is in the systole, the coiled carbon nanotube yarn acting as the working electrode within the energy harvester forms an electric double layer (EDL) in which electrolyte ions adhere to the coil surface by electrical attraction within the electrolyte.

[0091] Subsequently, when the heart is in the diastole phase, the energy harvester attached to the heart is also stretched and elongated by the mechanical energy of the heart surface stretching. Consequently, the coiled carbon nanotube yarn fixed within the energy harvester is also stretched and elongated, causing the coil diameter to decrease. As the space between the coil fiber strands narrows, electrolyte ions contained between the fiber strands are released to the outside, thereby reducing the number of electrolyte ions in contact with the coiled carbon nanotube yarn working electrode. This induces a change in the electrical capacitance of the working electrode (decrease in capacitance), and due to the reduced capacitance, a potential difference is created, generating a voltage (OCV, Open Circuit Voltage) (Q=CV, where Q is the amount of accumulated charge, C is the electrical capacitance, and V is the potential difference). Accordingly, when the above-mentioned implantable energy harvester is attached to the surface of the heart, electricity is generated by the change in length of the coiled carbon nanotubes within the energy harvester due to the tension and contraction caused by the heartbeat, and since the electrodes exposed outside the energy harvester housing are in contact with the heart, the generated electricity can stimulate the heart again through the exposed electrodes.

[0092]

[0093] According to the present invention, a coiled carbon nanotube yarn electrode is used in the working electrode constituting the energy harvester, wherein a portion of the end of the working electrode is fixed inside the housing and a portion of the other end is exposed outside the housing, so that when the energy harvester is attached to the heart, electrical energy harvested from the strain change of the working electrode due to the movement of the heart without the need for a power source can be used to stimulate the surface of the heart again through the exposed electrode, thereby helping the heart movement, so that it can be usefully used as a power-free heart pacemaker and further applied to in vivo electrical stimulation therapy.

[0094] Hereinafter, preferred manufacturing examples and experimental examples are presented to aid in understanding the present invention. However, the following manufacturing examples and experimental examples are intended only to aid in understanding the present invention, and the present invention is not limited by the following manufacturing examples and experimental examples.

[0095]

[0096] [Preparation Example 1: Preparation of a Power-Free Implantable Energy Harvester]

[0097] (1) Fabrication of a coiled carbon nanotube yarn working electrode

[0098] From the multiwalled carbon nanotube forest (MWNT forest) to the multiwalled carbon nanotube sheet (MWNT sheet, density: 1.7 μg / cm³) 2 A carbon nanotube yarn was manufactured by drawing out (length 30 cm, width 6 cm), rolling the multi-walled carbon nanosheet into a cylindrical shape, and then performing cone spinning with a weight attached to the bottom and applying a load of 107 MPa.

[0099] Next, a twist of 26 turns / cm was applied to the carbon nanotube yarn in one direction, and then further twisted in the same direction while maintaining the same load to form a coiled carbon nanotube yarn.

[0100] Subsequently, in order to limit the elongation range of the coiled carbon nanotube yarn to 30%, a coil with a total twist density of 61 turns / cm along the entire length was formed by changing the load to 15.4 MPa, and then a coiled carbon nanotube yarn working electrode capable of elongating by about 30% with a spring constant of 0.53 was manufactured by slightly untwisting the coil by twisting it in the opposite direction by about 8% of the total twist density under the same twisting load.

[0101]

[0102] (2) Preparation of a twisted carbon nanotube yarn counter electrode

[0103] From the multiwalled carbon nanotube forest (MWNT forest) to the multiwalled carbon nanotube sheet (MWNT sheet, density: 1.7 μg / cm³) 2 A multi-walled carbon nanosheet (length 30 cm, width 6 cm) was drawn and rolled into a cylinder shape with an amount four times greater than that of the carbon nanosheet of the working electrode of (1), and then loosely twisted while applying a load of 105 MPa with a weight attached to the bottom to produce a twisted carbon nanotube yarn counter electrode.

[0104]

[0105] (3) Manufacture of a power-free implantable energy harvester

[0106] The coiled carbon nanotube yarn working electrode manufactured in (1) above and the twisted carbon nanotube yarn counter electrode manufactured in (2) above were placed together in a silicone tube as a flexible housing. Next, a nylon fabric was used as a separator to physically separate the two electrodes while simultaneously surrounding the counter electrode to share the electrolyte. Two 3D-printed connections with small holes were positioned at the ends of the silicone tube to secure one end of the working electrode and the counter electrode, making it easy to suture to the heart surface. After placing the working electrode and the counter electrode inside the silicone tube, the inside of the silicone tube was filled with a 0.15 M NaCl aqueous electrolyte having a concentration similar to that of physiological saline (0.9% NaCl). Subsequently, epoxy was applied to seal the entire silicone tube so that the end of the silicone tube was connected to the connection part, thereby forming a hollow and closed cylindrical silicone tube that accommodates the entire electrode system, and parts of the working electrode and counter electrode were made to protrude outside the silicone tube to manufacture an energy harvester as shown in the structure of Fig. 1, and the actually manufactured energy harvester is shown in Fig. 2.

[0107]

[0108] [Comparative Example 1: Manufacture of an Open-Type Two-Electrode Energy Harvester]

[0109] An open-type two-electrode energy harvester was prepared by using the coiled carbon nanotube yarn of Preparation Example 1 as the working electrode in the electrolyte bath and a platinum mesh as the counter electrode.

[0110]

[0111] [Experimental Example 1: Optimization of Spring Coefficient of Coiled Carbon Nanotube Yarn Working Electrode]

[0112] In order to optimize the spring constant (SI) of the coiled carbon nanotube yarn working electrode in a power-free implantable energy harvester according to the present invention, the change in maximum open-circuit voltage (OCV) and strain range were measured for an energy harvester including a coiled carbon nanotube yarn working electrode having various spring constants and are shown in FIG. 4.

[0113] FIG. 4 is a graph showing the change in open-circuit voltage (OCV) within a general range of left ventricular longitudinal strain according to the spring constant of a coiled carbon nanotube yarn working electrode in an energy harvester according to one embodiment of the present invention.

[0114] As shown in Fig. 4, when the spring constant (SI) of the coiled carbon nanotube yarn working electrode was 0.38, the maximum strain range of the working electrode was only 15%, so it did not function sufficiently within the left ventricular longitudinal strain range (10–30%). However, when the spring constant (SI) of the coiled carbon nanotube yarn working electrode was 0.53, the strain range of the working electrode was 30%, and the performance at maximum strain within the left ventricular longitudinal strain range (10–30%) showed an open circuit voltage (OCV) of 122.3 mV. In addition, when the spring constant (SI) of the above-mentioned coiled carbon nanotube yarn working electrode was 0.77, the elongation range of the working electrode was 50%, but the maximum peak-to-peak OCV within the left ventricular longitudinal strain range (10~30%) was 87.9 mV, which was lower than that of the working electrode having a spring constant of 0.53.

[0115] Accordingly, by optimizing the spring constant of the working electrode, the energy harvester according to the present invention can harvest various biomechanical energies with optimized performance by applying it not only to the heart but also to other organs of the body that move periodically, such as the diaphragm, stomach, etc. In the case of the heart, it is preferable that the coiled carbon nanotube yarn working electrode used in the energy harvester has a spring constant greater than 0.38 and less than 0.77.

[0116]

[0117] [Experimental Example 2: Effect of Device Encapsulation]

[0118] In the power-free implantable energy harvester according to the present invention, closed-type device encapsulation is required for implantation within the body. To investigate the effect of such encapsulation on performance, a tensile strain of 20% was applied to the same coiled carbon nanotube yarn working electrode of the encapsulated closed-type energy harvester of Manufacturing Example 1 according to the present invention and the open-type two-electrode energy harvester of Comparative Example 1, and the OCV generated upon contraction was measured and is shown in FIG. 5.

[0119] FIG. 5 is a graph showing the change in OCV when a strain deformation of 20% is applied to the working electrode in an open-type energy harvester according to one comparative example of the present invention and a closed-type energy harvester according to one embodiment.

[0120] As shown in Figure 5, the peak-to-peak OCV of the open and closed energy harvesters was 97.1 mV and 87.2 mV, respectively, indicating that there was almost no difference in OCV generation capability before and after encapsulation, and that there was no serious performance degradation due to encapsulation.

[0121]

[0122] [Experimental Example 3: Multiple Device Combination]

[0123] In the power-free implantable energy harvester according to the present invention, to improve performance, a plurality of energy harvesters were connected in series, and the change in OCV according to the number of connected harvesters and the change in strain was measured and is shown in FIG. 6.

[0124] FIG. 6 is a graph showing the change in OCV according to the number of connected harvesters and the change in strain when the harvesters are connected in series in an energy harvester according to one embodiment of the present invention.

[0125] As shown in Fig. 6, compared to the case where the energy harvester according to the present invention is used as a single unit, the performance (peak-to-peak OCV) is improved as the number of connected energy harvesters increases and the strain increases from 10% to 30%.

[0126] Specifically, when four energy harvesters of the present invention were connected in series and extended coaxially by up to 30%, a maximum peak-to-peak OCV of about 350 mV and a maximum peak short-circuit current (SCC) of 230 μA were achieved.

[0127] Therefore, the energy harvester according to the present invention can improve performance by connecting a plurality of them in series.

[0128]

[0129] [Experimental Example 4: Effect of Tensile Frequency]

[0130] In the energy harvester according to the present invention, the following experiment was performed to investigate the effect of the tensile frequency of a heartbeat on the electrical harvesting of the energy harvester.

[0131] Specifically, various tensile frequencies were applied to the operating electrode of the energy harvester of Manufacturing Example 1, and the performance of the energy harvester according to the tensile frequency (OCV, peak voltage, and matching impedance) was measured and is shown in FIG. 7.

[0132] FIG. 7 is a graph showing the change in performance (OCV, peak power, and matching impedance) of an energy harvester according to one embodiment of the present invention as a function of tensile frequency.

[0133] As shown in Figure 7, the peak-to-peak OCV generated as the tensile frequency, i.e., the beats per minute (BPM), increased showed a tendency to decrease slightly as the penetration and emission of sufficient ions into the coiled CNT yarn were hindered due to the rapid elongation and contraction of the coiled CNT yarn working electrode, but it was not to a severe level.

[0134] The generated power was calculated using the matching impedance measured at various stretching frequencies. Both peak power and average power showed an increasing trend as the BPM increased. This is because the internal impedance of the working electrode within the energy harvester according to the present invention is affected inversely by the stretching frequency; therefore, the matching impedance decreases as the BPM increases, and consequently, the voltage (P) generated therefrom follows the relationship P = V² of the peak voltage (V²) divided by the load resistance (R). 2 The voltage increases depending on / R).

[0135] The above matching impedance is the intrinsic impedance of the working electrode (coiled carbon nanotube yarn), where the coiled carbon nanotube yarn can produce its maximum power. The generated power first increases as the load resistance increases, then produces maximum power at the point where the intrinsic impedance of the coiled carbon nanotube yarn and the load resistance become equal (so-called "matching impedance"), and then begins to gradually decrease.

[0136]

[0137] [Experimental Example 5: Durability Test]

[0138] Durability and stability are essential for realizing sustainable power for the continuous operation of implantable medical devices. Accordingly, to test the durability of the energy harvester according to the present invention, the change in OCV according to the number of cycles was measured when performing cycles of tension and contraction with strain under a sinusoidal deformation condition of 20% at 1 Hz, and is shown in FIG. 8.

[0139] FIG. 8 is a graph showing the change in OCV according to the number of cycles when performing a cycle of tension and contraction with 20% strain in an energy harvester according to one embodiment of the present invention.

[0140] As shown in Figure 8, the retention rate of peak-to-peak OCV during 50,000 repetitive stretch-and-recover cycles was approximately 94%, and its robust yet elastic structure was maintained, suggesting the potential for a long-term sustainable biomechanical energy harvester.

[0141]

[0142] [Experimental Example 6: Electricity Harvesting Test in an In Vitro Artificial Heartbeat System]

[0143] Since the energy harvester according to the present invention converts linear motion into electrical energy, the unique two-dimensional strain pattern of the heart surface resulting from continuous mechanical phenomena of the circulatory system affects the output of the energy harvester. Accordingly, an in vitro artificial heart rate system resembling the strain pattern of the target implant surface, particularly the global longitudinal strain (GLS) of the atrial membrane of the left ventricle (LV), was designed, and the performance of the energy harvester according to the present invention was evaluated in this in vitro artificial heart rate system.

[0144]

[0145] FIG. 9 is a graph showing the strain change of the energy harvester during the systole and diastolic phases of an ex vivo artificial heart rate system when an energy harvester according to one embodiment of the present invention is installed in an ex vivo artificial heart rate system.

[0146] As shown in Fig. 9, the ex vivo artificial heartbeat system formed a strain waveform on the surface of a balloon by adjusting the pressure applied to a water-filled balloon. Specifically, during systole, the pressure applied to the balloon was increased to reduce the strain, and during diastole, the pressure applied to the balloon was lowered so that the strain increased as the balloon inflated.

[0147]

[0148] FIG. 10 is a graph showing the change in open circuit voltage (OCV) and short circuit current (SCC) of an energy harvester according to the change in strain of the energy harvester during systole and diastole in an ex vivo artificial heartbeat system according to an embodiment of the present invention.

[0149] As shown in Fig. 10, the OCV waveform followed the applied strain pattern, and it was confirmed that the SCC waveform had a phase difference of 90 degrees when compared to the voltage waveform.

[0150]

[0151] Meanwhile, since each part of the surface of the left ventricle (LV) of the heart has its own various strain ranges, the energy harvester according to the present invention was tested using various strain values ​​within the general range of left ventricular longitudinal strain (GLS), and the generated OCV was measured and shown in FIG. 11.

[0152] FIG. 11 is a graph showing the OCV generated by various strains in the general range of left ventricular longitudinal strain of an ex vivo artificial heartbeat system in an energy harvester according to one embodiment of the present invention.

[0153] As shown in FIG. 11, the OCV generated by the energy harvester according to one embodiment of the present invention increased in proportion to the applied strain while maintaining the basic waveform of the GLS, which suggests that the energy harvester of the present invention has potential utility as a real-time heart monitoring sensor.

[0154]

[0155] In addition, in one embodiment of the present invention, another energy harvester was tested under conditions of various tension frequencies related to actual human heart rate, and the generated OCV was measured and is shown in FIG. 12.

[0156] FIG. 12 is a graph showing the OCV generated according to the heart rate frequency in the general range of left ventricular longitudinal strain of an ex vivo artificial heart rate system in an energy harvester according to one embodiment of the present invention.

[0157] As shown in Fig. 12, three different GLS stimuli of 50, 80, and 130 BPM were applied, taking into account the human heart rate, and the heart rate frequency was reflected in the OCV and SCC changes as the frequency of the repeating pattern, which indicates the ability to detect the heart rate by the voltage or current waveform generated by the energy harvesting characteristics of the energy harvester of the present invention, which responds proportionally to the applied strain.

[0158]

[0159] In addition, power production by an energy harvester according to one embodiment of the present invention was evaluated in an ex vivo artificial heartbeat system and is shown in FIG. 13.

[0160] FIG. 13 is a graph showing the change in peak power and average power generated according to the load resistance connected to the energy harvester in the general range of left ventricular longitudinal strain of an ex vivo artificial heartbeat system in an energy harvester according to one embodiment of the present invention.

[0161] When a GLS strain of 60 BPM with a 30% tension was applied, the maximum peak power of the energy harvester according to the present invention was 1.42 W / kg, and the average power was 0.39 W / kg. In addition, the power generated by the energy harvester according to the present invention can be obtained at various BPMs within the range of human heart rate.

[0162] It was observed that the power and energy per cycle generated by the energy harvester according to the present invention depend on the strain frequency. The decrease in matching impedance as the strain frequency increased resulted in an increase in power. When an artificial heartbeat GLS strain simulated at 20% was applied, a peak-to-peak OCV of approximately 60 mV was stably maintained regardless of changes in BPM.

[0163]

[0164] FIG. 14 is a graph showing the OCV, peak power, and energy per cycle generated in an energy harvester according to a heart rate frequency in a general range of left ventricular longitudinal strain of an ex vivo artificial heart rate system in an energy harvester according to one embodiment of the present invention.

[0165] As shown in FIG. 14, as the beat frequency increased from 50 BPM to 130 BPM, the peak power increased from 1.05 W / kg to 2.50 W / kg, the average power also increased from 0.32 W / kg to 0.55 W / kg, and the energy per cycle decreased from 0.36 J / kg to 0.26 J / kg. This implies that the energy harvester according to the present invention can generate power from heartbeats across the entire range of human heart rates to power a CIED or directly stimulate the heart, and can also obtain information regarding heart conditions such as strain and beat frequency from the power generation trends associated with these strain characteristics.

[0166]

[0167] [Experimental Example 7: In vivo application in a pig model]

[0168] To evaluate the possibility of the energy harvester according to the present invention being implanted on the actual surface of the heart to generate electrical energy from deformation of the heart surface, the in vivo performance of the energy harvester was evaluated in a pig model (n=10).

[0169] FIG. 15 is a photograph showing the strain change of an energy harvester according to the systole and diastole of a heartbeat when an energy harvester according to one embodiment of the present invention is installed in the heart of a pig.

[0170] As shown in Fig. 15, during a continuous heartbeat, the length of the energy harvester sutured along the curved outer layer of the left ventricle changed simultaneously with the periodic dimensional changes of the heart surface. The heart movement during diastole caused the flexible energy harvester to be stretched, and the heart movement during systole caused the energy harvester to contract.

[0171]

[0172] FIG. 16 is a graph showing continuous OCV output values ​​generated from four connected energy harvesters according to periodic heartbeat movements when an energy harvester according to one embodiment of the present invention is installed in the heart of a pig, and FIG. 17 is a graph showing the OCV generated in the energy harvesters during the systole and diastole of the heartbeat when an energy harvester according to one embodiment of the present invention is installed in the heart of a pig.

[0173] As shown in FIG. 16, a single device of four energy harvesters reached a maximum voltage of approximately 120 mV, and as shown in FIG. 17, the waveform repeats such that the OCV increases when the length of the energy harvester is stretched during the diastole of the heartbeat, and decreases when the length of the energy harvester is released during the systole of the heartbeat, thereby confirming that the energy harvester according to the present invention produces electrical energy (OCV) through the heartbeat without a power source.

[0174]

[0175] [Experimental Example 8: Mapping Study]

[0176] After confirming that the power-free implantable energy harvester according to the present invention reliably produces energy through heart movement, the following experiment was performed to determine whether the energy harvester can electrically stimulate the heart and function as a potential pacemaker.

[0177] Specifically, to investigate the relationship between electrical energy generated from the energy harvester according to the present invention and myocardial stimulation, a detailed activity mapping analysis of the left ventricle was performed using the Rhythmia system (Rhythmiaⓒ, Boston Scientific, Marlborough, MA, USA).

[0178] The two exposed electrodes of the energy harvester according to the present invention were each positioned about 1 cm apart inside the myocardium of the left ventricle.

[0179] Next, to achieve sufficient heart rate slowing, the AV was blocked via AV node removal, and as asystole occurred, RV pacing was initiated to maintain a specific stable heart rate at 80 BPM. After maintaining RV pacing for 2 minutes, it was discontinued or the RV pacing rate was reduced to 30 BPM. Secondary beats that occurred after the discontinuation of RV pacing or during the heart rate slowing stimulation were mapped using an Orion mapping catheter, which was positioned adjacent to the energy harvester on the endocardial surface mapped by a fluoroscope.

[0180] This mapping was analyzed and is shown in Fig. 18.

[0181] FIG. 18 is a mapping analysis diagram showing that when an energy harvester according to one embodiment of the present invention is installed in the heart of a pig, the electricity generated stimulates the left ventricle (LV) to induce an electrical signal.

[0182] According to the mapping analysis in Fig. 18, heartbeats generally occur due to AV node activation (see Reference), but after removing the AV node and RV pacing, it can be seen that secondary heartbeats occurred in different regions compared to normal AV node activation. It was confirmed that these different regions are in close proximity to the area where the energy harvester according to the present invention is located.

[0183] From this, it was confirmed that the electrical impulse emitted by the energy harvester according to the present invention can electrically stimulate the heart and thus cause contraction of the myocardium, thereby enabling its use as a pacemaker for the heart.

[0184]

[0185] [Experimental Example 9: Histological Examination]

[0186] In order to identify potential structural damage that may occur in the heart due to the energy harvester according to the present invention when the energy harvester is implanted in the body, hematoxylin and eosin (H&E) tests were performed on the heart muscle tissue of pigs that underwent cardiac pacing with the energy harvester according to the present invention implanted. Additionally, the hearts of animals that did not undergo cardiac pacing were used as a control group.

[0187] The test results are shown in Fig. 19.

[0188] FIG. 19 is a diagram showing the effect on the heart muscle when the heart is paced with electricity generated when an energy harvester according to one embodiment of the present invention is installed in the heart of a pig.

[0189] As shown in FIG. 19, as a result of evaluating cells and tissue structures by performing H&E, no serious damage such as myocardial infarction, inflammatory cell infiltration, necrosis, or loss of normal myocardial tissue was observed even after installing an energy harvester according to one embodiment of the present invention into the heart of a pig and performing cardiac pacing.

[0190] Therefore, the energy harvester according to the present invention does not cause damage to myocardial tissue even after insertion into the body, thus exhibiting excellent in vivo stability, and can be usefully employed as a power-free implantable cardiac pacemaker.

[0191]

[0192] Although preferred embodiments of the present invention have been described above, those skilled in the art may modify and change the present invention in various ways by adding, changing, deleting, or adding components, etc., without departing from the spirit of the present invention as described in the claims, and such modifications and changes shall also be deemed to be included within the scope of the rights of the present invention. For example, each component described as a single unit may be implemented in a distributed manner, and components described as distributed may likewise be implemented in a combined form. The scope of the present invention is defined by the claims set forth below rather than by the above detailed description, and all modifications or variations derived from the meaning and scope of the claims and equivalent concepts thereof should be interpreted as being included within the scope of the present invention.

[0193] [Explanation of the symbol]

[0194] 100: Power-free implantable energy harvester

[0195] 10: Working electrode

[0196] 20: Counter electrode

[0197] 30: Separator

[0198] 40: Electrolytes

[0199] 50: Housing

[0200] 60: Connection

Claims

1. A closed housing having biocompatibility and elasticity and a hollow interior; An operating electrode disposed inside the housing, with a portion exposed outside the housing; A counter electrode disposed inside the housing, with a portion exposed outside the housing; A separator disposed inside the above housing and separating the working electrode and the counter electrode in a manner that surrounds the perimeter of the counter electrode; Electrolyte filling the interior of the above housing; and It includes connecting portions formed at both ends of the above housing for connecting to internal organs, The above working electrode and the above counter electrode are formed such that a portion is immersed in the electrolyte and a portion is exposed outside the housing, and The above working electrode is characterized by comprising a coiled carbon nanotube yarn in which a carbon nanotube sheet is twisted and coiled. Powerless implantable energy harvester.

2. In Paragraph 1, A power-free, implantable energy harvester characterized in that the housing is a silicone tube.

3. In Paragraph 1, A power-free, implantable energy harvester characterized in that the above-mentioned separator is a porous polymer tube.

4. In Paragraph 1, A power-free, implantable energy harvester characterized in that the counter electrode is a carbon nanotube yarn in which the carbon nanotube sheet is twisted.

5. In Paragraph 1, The above-described power-free implantable energy harvester is characterized by the spring constant (SI) of the coiled carbon nanotube yarn being greater than 0.38 and less than 0.77 when attached to the surface of the heart.

6. In Paragraph 1, The above-mentioned power-free implantable energy harvester is characterized by attaching to the surface of the heart and stimulating the heart with electricity generated by tension and contraction according to the heartbeat.

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