Medical device electrode, coating and process

Abstract

A device includes an electrode, a power source, an electrical pacing circuit, and a coating applied to one or more surfaces of the electrode. The electrical pacing circuit is coupled to the power source and configured to deliver cardiac pacing. The coating includes a first adhesive layer comprising porous titanium nitride and a second electrically insulating layer comprising parylene. The thickness of the second electrically insulating layer is substantially uniform throughout the coating. A method of applying a coating, the method comprising: applying, at a first time, a first adhesive layer to one or more surfaces of an electrode; applying a plasma cleaning process to the first adhesive layer at a second time after the first time; and applying a second electrically insulating layer to the one or more surfaces of the electrode coated with the first adhesive layer at a third time after the second time.

Description

[0001] This application claims the benefit of U.S. Provisional Patent Application Serial No. 63 / 481,674, filed on January 26, 2023, which is incorporated herein by reference in its entirety. Technical Field

[0002] The present application relates to electrodes for implantable medical devices, and more particularly to techniques for forming coated electrodes. Background Art

[0003] An example implantable medical device is a leadless pacemaker that can assist a patient's cardiac function. Leadless pacemakers can provide advantages over conventional pacemakers because the absence of leads can allow for fewer complications and improved patient outcomes. To ensure long-term biostability, reliability, and performance, the pacing electrodes of a leadless pacemaker can be insulated with polyparaxylylene, a flexible, biocompatible polymer that can help reduce adverse reactions to the implanted pacemaker. Electrodes used for other cardiac pacemakers or other electrical stimulation or sensing devices, such as electrodes carried by implantable leads, can also be insulated with polyparaxylylene. The non-insulated portion of the electrode can be defined as acting as an electrically active portion for sensing and / or stimulation, and as providing desired sensing and / or stimulation performance. Summary of the Invention

[0004] Deformation of parylene in the form of delamination, swelling, or tearing can impair the long-term biostability and function of the implant device. For example, deformation of parylene can negatively affect the sensing and / or stimulation performance of the implant device. Some cardiac pacing devices, such as leadless pacing devices, include an elongated electrode extending from a first cardiac chamber to myocardial tissue of a second cardiac chamber. A distal end portion of such an electrode can be non-insulated to allow sensing of electrical activity in the second cardiac chamber and pacing of the second cardiac chamber, wherein insulation on the remainder of the electrode impedes sensing and / or pacing of the first cardiac chamber by the electrode. Deformation of parylene can allow undesirable sensing and / or stimulation of the first cardiac chamber by the elongated electrode, thereby negatively affecting the sensing and therapeutic performance of such an implant device.

[0005] According to the technology of the present disclosure, a coating can be applied to one or more surfaces of an electrode, wherein the coating includes a first adhesive layer comprising an adhesive base (such as porous titanium nitride) and a second electrically insulating layer comprising parylene. The porous titanium nitride layer can promote adhesion of the parylene layer to one or more surfaces of the electrode, which can reduce failure of the implantable medical device and increase its long-term biostability and reliability. In some examples, the electrode is elongated, for example, wherein the parylene coats all of the electrode except the distal portion. In some examples, the electrode is configured as a coil. Electrodes configured according to the technology of the present disclosure can have a significantly reduced likelihood of insulation deformation, thereby advantageously ensuring the desired performance of the medical device.

[0006] In some examples, the present disclosure describes an implantable medical device comprising an electrode, a power source, an electrical pacing circuit, and a coating applied to one or more surfaces of the electrode. The electrical pacing circuit is coupled to the power source and configured to deliver cardiac pacing therapy. The coating applied to the one or more surfaces of the electrode comprises a first adhesive layer comprising porous titanium nitride and a second electrically insulating layer comprising parylene. The thickness of the second electrically insulating layer is substantially uniform throughout the coating.

[0007] In some examples, the present disclosure describes a method for forming an implantable medical device comprising: an electrode, a power source, an electrical pacing circuit coupled to the power source and configured to deliver cardiac pacing therapy, and a coating applied to one or more surfaces of the electrode, wherein the coating comprises a first adhesive layer comprising porous titanium nitride and a second electrically insulating layer comprising parylene. The method comprises: applying the first adhesive layer comprising porous titanium nitride to the one or more surfaces of the electrode at a first time. The method further comprises: applying a plasma cleaning process to the first adhesive layer at a second time after the first time. The method further comprises: applying the second electrically insulating layer comprising parylene to the one or more surfaces of the electrode coated with the first adhesive layer at a third time after the second time.

[0008] In some examples, the present disclosure describes an implantable medical device comprising a power source, an electrical pacing circuit, a first electrode, a second electrode, and a coating. The electrical pacing circuit is coupled to the power source and configured to deliver cardiac pacing therapy. The first electrode is configured to extend distally from a distal portion of the implantable medical device. The second electrode is positioned on the distal portion of the implantable medical device. The coating comprises a first adhesive layer comprising porous titanium nitride and a second electrically insulating layer comprising parylene.

[0009] This summary is intended to provide an overview of the subject matter described in this disclosure. This summary is not intended to provide an exclusive or exhaustive explanation of the technology as described in detail in the following figures and description. Further details of one or more examples are set forth in the following figures and description. Other features, objects, and advantages will be apparent from the description and drawings and from the statements provided below. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] Figure 1 is a conceptual diagram illustrating an example device implanted in a patient's heart according to one or more aspects of the present disclosure.

[0011] Figure 2 is a diagram showing one or more aspects of the present disclosure Figure 1 Functional block diagram of an example configuration of an IMD.

[0012] Figure 3 Implanted at the target implantation site Figure 1 and Figure 2 Conceptual image of the device.

[0013] Figure 4 is a conceptual diagram illustrating an example implantable medical device including electrodes.

[0014] Figure 5 is a conceptual diagram illustrating example coatings applied to one or more surfaces of an electrode.

[0015] Figure 6 is a flow chart illustrating an example technique for forming an implantable medical device including a coated electrode. DETAILED DESCRIPTION

[0016] The present disclosure describes an implantable medical device and a method for forming such an implantable medical device, the implantable medical device comprising an electrode coated with a first adhesive layer comprising porous titanium nitride and a second electrical insulating layer comprising parylene. In some examples, the implantable medical device is a leadless pacing device, but in other examples can be other devices, such as other leadless stimulation devices or implantable leads. In some examples, the electrode is a pacing (or more generally, stimulation) electrode coil or spiral. In some examples, the electrode comprises multiple turns of at least one filament (e.g., a conductive metal wire) and delivers electrical stimulation to the patient (e.g., pacing stimulation, such as anti-tachycardia pacing, bradycardia pacing and / or post-shock pacing, etc.). In some examples, one or more surfaces of the electrode are coated with a parylene layer to improve the long-term biostability, reliability, and performance of the implantable medical device. In some examples, one or more surfaces of the electrode are coated with a first adhesive layer comprising porous titanium nitride to improve the adhesion of the parylene layer.

[0017] For example, a first adhesive layer comprising porous titanium nitride is applied to one or more surfaces of an electrode at a first time. A second electrically insulating layer comprising parylene is then applied to one or more surfaces of the electrode coated with the first adhesive layer at a second time after the first time. In some examples, a plasma cleaning process may be applied to the porous titanium nitride layer after applying the porous titanium nitride layer and before applying the parylene layer to remove any surface impurities or contaminants. In some examples, the first adhesive layer comprising porous titanium nitride is thermally bonded to the second electrically insulating layer comprising parylene. In some examples, the first adhesive layer may cover a first amount, such as the entire surface of the electrode, while the second electrically insulating layer may cover a second amount less than the first amount, thereby exposing a portion of the first adhesive layer. In some examples, the first amount and the second amount may be coextensive, thereby exposing a portion of the bare electrode. In some examples, the exposed portion may be the distal end of the electrode.

[0018] Figure 1 is a conceptual diagram illustrating an example device 10 implanted in a patient's heart 12 according to one or more aspects of the present disclosure. The device 10 is shown implanted in a target implantation region 2 in the right atrium (RA) of the patient's heart 12, such as the triangle of Koch in the patient's heart 12, with the distal end of the device 10 pointing toward the left ventricle (LV) of the patient's heart 12. Figure 1 In the example shown, the distal end of device 10 is directed toward the LV, but in some examples, the distal end may be directed toward other targets, such as the ventricular septum of heart 12. Target implantation region 2 may be located between the bundle of His and the coronary sinus and may be adjacent to the tricuspid valve.

[0019] The device 10 includes a housing 30. The device 10 includes a distal end 22 and a proximal end 24. The distal end 22 includes a first electrode 26 and a second electrode 28, both of which can extend distally from the housing 30. The first electrode 26 extends from the distal end 22 and can penetrate the wall tissue of the first chamber (e.g., the RA in the illustrated example) into the wall tissue of the second chamber (e.g., the LV in the illustrated example). The second electrode 28 extends from the distal end 22 and is configured to flexibly maintain contact with the wall tissue of the first chamber without the second electrode penetrating the wall tissue of the first chamber. The device 10 may also include a third electrode 29, which may be formed as a non-insulated portion of the housing 30 and serves as a reference electrode paired with either or both of the first electrode 26 and the second electrode 28 for sensing and stimulation.

[0020] Figure 1The illustrated configuration of electrodes 26 and 28 allows the device 10 to sense cardiac signals and / or deliver cardiac pacing to multiple chambers of the heart 12, such as the RA and ventricles in the illustrated example. In this manner, the configuration of electrodes 26 and 28 can facilitate delivery of AV synchronized pacing by a single device 10 implanted in a single chamber (e.g., the RA). Figure 1 In the example shown, the device 10 is implanted at target implant region 2 for sensing and / or pacing the RA and ventricles, but a device having an electrode configuration according to examples of the present disclosure can be implanted at any of a variety of locations for sensing and / or pacing any two or more chambers of the heart 12. For example, the device 10 can be implanted at region 2 or another region, and the first electrode 26 can extend into tissue of the LV or ventricular septum (e.g., myocardial tissue) to, for example, facilitate delivery of AV-synchronized pacing. Furthermore, a device having an electrode configuration according to examples of the present disclosure can be implanted at any of a variety of locations within the patient's body for sensing and / or delivering therapy to other patient tissue.

[0021] Figure 2 is a functional block diagram illustrating an example configuration of the device 10 including the housing 30. Figure 1 As illustrated, the device 10 includes electrodes 26, 28, and 29, which may be arranged relative to Figure 1 For example, as with respect to Figure 1 As described, the first electrode 26 can be configured to extend from the distal end 22 of the housing 30 and can penetrate the wall tissue of the first lumen (e.g., RA) into the wall tissue of the second lumen (e.g., LV). The second electrode 28 extends from the distal end 22 of the housing 30 and is configured to flexibly maintain contact with the wall tissue of the first lumen without the second electrode penetrating the wall tissue of the first lumen.

[0022] exist Figure 2 In the example shown, device 10 includes switching circuitry 50, sensing circuitry 52, signal generating circuitry 54, sensor 56, processing circuitry 58, telemetry circuitry 60, memory 62, and power source 68. The various circuits may be or include programmable or fixed-function circuitry that is configured to perform the functions attributed to the respective circuits. Memory 62 may store computer-readable instructions that, when executed by processing circuitry 58, cause device 10 to perform various functions. Memory 62 may be a storage device or other non-transitory medium. Figure 2 The components of the illustrated device 10 may be housed within a housing 30 .

[0023] The signal generating circuit 54 generates electrical stimulation signals, such as cardiac pacing pulses. The switching circuit 50 is coupled to the electrodes 26, 28, and 29 and may include one or more switching arrays, one or more multiplexers, one or more switches (e.g., a switching matrix or other set of switches), one or more transistors, or other circuits. The switching circuit 50 is configured to direct stimulation signals from the signal generating circuit 54 to a selected combination of electrodes 26, 28, and 29 having a selected polarity, for example, to selectively deliver pacing pulses to the RA, ventricles, or interventricular septum of the heart 12. For example, to pace one or both ventricles, the switching circuit 50 may couple the first electrode 26 that penetrates the wall tissue of the ventricle or interventricular septum to the signal generating circuit 54 as a cathode and couple the third electrode 29 to the signal generating circuit 54 as an anode. As another example, to pace the RA, the switching circuit 50 may couple the second electrode 28 that flexibly remains in contact with the RA endocardium to the signal generating circuit 54 as a cathode and couple the third electrode 29 to the signal generating circuit 54 as an anode.

[0024] The switching circuit 50 can also selectively couple the sensing circuit 52 to a selected combination of electrodes 26, 28, and 29, for example, to selectively sense electrical activity of the RA or ventricles of the heart 12. The sensing circuit 52 can include filters, amplifiers, analog-to-digital converters, or other circuitry configured to sense cardiac electrical signals via electrodes 26 and 28. For example, the switching circuit 50 can couple each of the first electrode 26 and the second electrode 28 in combination with the third electrode 29 to a corresponding sensing channel provided by the sensing circuit 52 to sense ventricular cardiac electrical signals or atrial cardiac electrical signals, respectively. In some examples, the sensing circuit 52 is configured to detect an event within the cardiac electrical signal, such as a depolarization, and provide an indication of the event to the processing circuit 58. In this manner, the processing circuit 58 can determine the timing of atrial depolarization and ventricular depolarization and control the delivery of cardiac pacing (e.g., AV synchronized cardiac pacing) based on the timing. The processing circuitry 58 may include any one or more of the following: a microprocessor, a controller, a digital signal processor (DSP), an application-specific integrated circuit (ASIC), a field-programmable gate array (FPGA), discrete logic circuitry, or any other processing circuitry configured to provide the functionality attributed to the processing circuitry 58, which may be embodied herein as firmware, hardware, software, or any combination thereof.

[0025] Sensor 56 may include one or more sensing elements that convert patient physiological activity into electrical signals to sense the value of a corresponding patient parameter. Sensor 56 may include one or more accelerometers, optical sensors, chemical sensors, temperature sensors, pressure sensors, or any other type of sensor. Sensor 56 may output a patient parameter value that may be used as feedback to control the sensing and delivery of therapy by device 10.

[0026] Telemetry circuit 60 supports communication between device 10 and external programmer ( Figure 2 Processing circuitry 58 of device 10 may receive updates on operating parameters from the computing device and provide collected data, such as sensed cardiac activity or other patient parameters, via telemetry circuitry 60. Telemetry circuitry 60 may communicate via radio frequency (RF) communication techniques, for example, via an antenna (not shown).

[0027] Power source 68 delivers operating power to the various components of device 10. Power source 68 may include a rechargeable or non-rechargeable battery and a power generation circuit to generate operating power. Recharging may be accomplished through proximal inductive interaction between an external charger and an inductive charging coil within device 10.

[0028] Figure 3 is a conceptual diagram of the device 10 implanted at the target implantation area 2. The first electrode 26 can be inserted so that the tissue engages with the helical shape of the first electrode 26. When the first electrode 26 engages with the tissue, the first electrode 26 penetrates the tissue at the target implantation area 2 and advances through the atrial myocardium 20 and the central fibrous body 16 to position the first electrically active area 44 in the ventricular myocardium 14, as shown. Figure 3 In some examples, first electrode 26 penetrates into the ventricular septum. In some examples, first electrode 26 does not completely penetrate the ventricular endocardial surface or the epicardial surface.

[0029] In some examples, manual pressure applied to the proximal end 24 of the housing, for example via an advancement tool, provides a longitudinal force to penetrate cardiac tissue at the target implantation region 2. In some examples, actuation of the advancement tool causes the device 10 and the first electrode 26, which is configured as a helix, to rotate about the longitudinal axis. Rotation of the helix about the longitudinal axis advances the first electrode 26 through the atrial myocardium 20 and the central fibrous body 16 to position the first electrically active region 44 in the ventricular myocardium 14, as shown. Figure 3 shown.

[0030] As the first electrode 26 is advanced into the tissue, the distance between the second electrode 28 and the atrial endocardium 18 decreases until the second electrode 28 contacts the surface of the atrial endocardium 18 and can be pressed against the surface of the atrial endocardium such that the cardiac tissue engages the second electrically active area 46. The second electrode 28 is maintained in contact with the atrial endocardium 18 by the first electrode 26, e.g., the first electrode 26 prevents the second electrode 28 from retracting from the surface of the atrial endocardium 18. As described herein, the second electrode 28 is also configured to flexibly maintain contact with the atrial endocardium 18. In some examples, the second electrode 28 can be positioned toward the distal end 22 ( Figure 1 ) elastically deforms and has a spring bias that urges the second electrode distally from distal end 22. In some examples, first electrode 26 may be the only fixed feature of device 10. The distance that first electrode 26 extends from housing 30 may be selected so that first electrically active region 44 reaches an appropriate depth in the tissue layers to reach the target pacing and sensing site, in this case, in ventricular myocardium 14, without penetrating all the way into the adjacent heart chambers.

[0031] In some pacing applications, the target implantation region 2 is along the atrial endocardium 18, substantially below the AV node and the bundle of His. The first electrode 26 can have a length that penetrates the atrial endocardium 18 in the target implantation region 2, passes through the central fibrous body 16, and enters the ventricular myocardium 14 without penetrating the ventricular endocardial surface. In some examples, when the full length of the first electrode 26 is fully advanced into the target implantation region 2, the first electrically active region 44 rests within the ventricular myocardium 14, and the second electrode 28 is positioned in close contact with the atrial endocardium 18. In various examples, the first electrode 26 can extend from the distal end 22 of the housing 30 by approximately 3 mm to 12 mm. In some examples, the first electrode 26 can extend from the housing 30 by a distance of at least 3 millimeters (mm), and in various examples, by a distance of at least 3 mm but less than 20 mm, less than 15 mm, less than 10 mm, or less than 8 mm. The diameters of the first and second electrodes 26, 28 can be less than 2 mm and can be 1 mm or less, or even 0.6 mm or less.

[0032] Figure 4 is a conceptual diagram illustrating an example implantable medical device (IMD) 80 including an elongated electrode, which may be in the form of an elongated electrode coil 86 or helix extending distally from a distal portion of the IMD 80. The IMD 80 may be substantially similar to Figure 1 、 Figure 2 and Figure 310. Instead of the depicted elongated electrode coil 86, the elongated electrode may comprise an elongated shaft, e.g., a completely straight or substantially straight shaft, needle, or dart extending distally from a distal portion of the IMD 80 along or parallel to the central longitudinal axis of the IMD 80. Such an elongated shaft electrode may be curved along all or a portion of its length and / or may be oriented at an oblique angle relative to the central longitudinal axis along all or a portion of its length and / or include a sharp or tissue-penetrating distal tip. Alternatively, the elongated electrode coil 86 may be substantially similar to Figure 1 、 Figure 2 and Figure 3 The first electrode 26. Figure 4 As shown in the example of FIG, the elongated electrode coil 86 includes one or more surfaces, such as the elongated electrode coil surface 88. Figure 4 In the example of , IMD 80 also includes a shorter electrode, which can be in the form of a partial electrode coil 82 or partial helix positioned on the distal end of IMD 80. In lieu of the depicted partial electrode coil 82, the shorter electrode can include any other suitable electrode or electrode surface, such as a round "button" electrode or other shape, such as a square electrode or rectangular electrode, that protrudes a small distance (relative to the length of the elongated electrode) from the distal end of IMD 80 or is flush with the distal end. The shorter electrode can protrude a fixed distance from the distal end of IMD 80, or it can be flexible or spring-like in nature such that a force can push the shorter electrode closer to IMD 80 and the shorter electrode can return toward its original position when the force is reduced or removed. Alternatively, the partial electrode coil 82 can be substantially similar to Figure 1 、 Figure 2 and Figure 3 The second electrode 28. In some examples, the partial electrode coil 82 includes one or more surfaces, such as a partial electrode coil surface 84.

[0033] Throughout this specification and the accompanying drawings, descriptions of the functions, features, material compositions, and application of coatings 94 to elongated electrode coils 86 and partial electrode coils 82 are presented and depicted. It should be understood that such descriptions provided herein also apply to any of the various forms or embodiments of elongated electrodes (instead of elongated electrode coils 86) and shorter electrodes (instead of partial electrode coils 82) described herein, or to any alternatives that may be apparent to one of ordinary skill in the relevant art.

[0034] In some examples, IMD 80 can be implanted in a human patient. In alternative examples, IMD 80 can be implanted in a non-human patient, such as a primate, canine, equine, porcine, bovine, or feline animal. These other animals may be undergoing clinical or research treatment that may benefit from the subject matter of the present disclosure.

[0035] exist Figure 4 In some examples, IMD 80 is a leadless pacing device, e.g., IMD 80 is not connected to any medical electrical leads and can be completely implanted in a patient. In some examples, IMD 80 may include one or more leadless medical devices that include one or more electrodes configured as described. In other examples, IMD 80 may include one or more medical devices, electrical leads, external devices, or other components including medical electrical leads. IMD 80 may include, but is not limited to, medical devices such as implantable cardioverter-defibrillators, neuromuscular stimulator devices, neurostimulator devices, pacemakers, etc. In some examples, IMD 80 is generally cylindrical or pill-shaped and is hermetically sealed to prevent the ingress of fluids. In some examples, IMD 80 is an atrial pacing device that is configured to monitor ventricular events and control atrial pacing pulse delivery based on sensed ventricular events (or the lack thereof) to promote atrial-ventricular synchronization in the patient. In some examples, IMD 80 is a ventricular pacing device configured to monitor electrical activity of the patient's heart and control ventricular pacing pulse delivery based on sensed atrial events (or the lack thereof). In some examples, IMD 80 is connected to at least one medical electrical lead. In some examples, IMD 80 is connected to two or more medical electrical leads.

[0036] Similar to Figure 1 、 Figure 2 and Figure 3 In some examples, the elongated electrode coil 86 is configured to engage cardiac tissue to deliver electrical stimulation therapy to the patient. In some examples, the elongated electrode coil 86 is configured to sense electrophysiological signals. The elongated electrode coil 86 may include or be formed of any suitable conductive material. In some examples, the elongated electrode coil 86 may include a substrate (e.g., a wire). In some examples, the elongated electrode coil 86 may include a platinum alloy, including but not limited to iridium. In some examples, the elongated electrode coil 86 may include a single filament coil. In other examples, the elongated electrode coil 86 may include a multi-filament coil, such as a double filament coil. In some examples, the elongated electrode coil 86 may include a sharp distal tip.

[0037] IMD 80 can be configured to include Figure 2 The housing 30. Figure 4 As illustrated, IMD 80 may include an elongated electrode coil 86 and a partial electrode coil 82, which may be respectively Figure 1 、 Figure 2 and Figure 3The IMD 80 can be configured in the same manner as the first electrode 26 and the second electrode 28 of the leadless device. For example, the IMD 80 can be configured to include processing circuitry, electrical sensing circuitry, electrical pacing circuitry, and a power source, which can be configured as a rechargeable or non-rechargeable battery, communication circuitry, sensor circuitry, and non-transitory memory, to achieve functionality attributable to a leadless pacemaker device, such as the Micra transcatheter pacing system from Medtronic Public Limited Company, of Fridley, Minnesota (operating headquarters).

[0038] Figure 5 This is an example Figure 4 A conceptual cross-sectional view of an example configuration of an elongated electrode coil 86, which may be substantially similar to Figure 1 、 Figure 2 and Figure 3 In the illustrated example, the elongated electrode coil 86 includes a coating 94 applied to one or more surfaces of the elongated electrode coil 86, such as the elongated electrode coil surface 88. Figure 5 As shown in the example of FIG, coating 94 includes a first adhesive layer 90 comprising porous titanium nitride in contact with elongated electrode coil 86. Layer 90 may include other compounds containing titanium or any other suitable compound that provides a "fractal" surface or a surface having columnar grains terminating at ends defined by crystalline facets. In some examples, for example, first adhesive layer 90 comprising porous titanium nitride forms a fractal surface beneath a second electrically insulating layer comprising parylene. Figure 5 In some examples, elongated electrode coil 86 (or at least its outermost portion) comprises or is formed from a platinum alloy. In some examples, elongated electrode coil 86 (or at least its outermost portion) comprises or is formed from platinum and iridium, or a nickel-cobalt-chromium-molybdenum alloy, or a stainless steel alloy (such as 316L), or nitinol, or any other suitable conductive and biocompatible material.

[0039] The coating 94 also includes a second electrically insulating layer 92 comprising parylene in contact with the first adhesive layer 90. As described herein, the first adhesive layer 90 can be a porous titanium nitride layer applied to the elongated electrode coil 86 to improve the adhesion of the second electrically insulating layer 92 to the elongated electrode coil 86. As described herein, the second electrically insulating layer 92 can be a parylene layer. Parylene is a flexible biomedical coating used for chronic implants (such as pacing electrodes). The improved adhesion of parylene can eliminate possible failures, such as delamination, swelling, or tearing in the body, which can compromise the biostability and function of the implant in the chronic phase, thereby allowing for longer-term stability and reliability of the implant. In some examples, the thickness of the first adhesive layer 90 is substantially uniform throughout the coating 94, for example, the thickness of the first adhesive layer 90 is substantially uniform over the elongated electrode coil surface 88 of the elongated electrode coil 86 to which the coating 94 is applied. In some examples, the thickness of the second electrically insulating layer 92 is substantially uniform throughout the coating 94. For example, the thickness of the second electrically insulating layer 92 is substantially uniform across the elongated electrode coil surface 88 to which the coating 94 is applied. In some examples, the thickness of the coating 94 is substantially uniform across the entire surface of the elongated electrode coil 86. In some examples, the distal-most quarter turn, or 90°, of the elongated electrode coil 86 includes only the first adhesive layer 90, thereby facilitating pacing only at the distal end of the elongated electrode coil 86. In these examples, silicone tubing is used to mask the distal-most quarter turn portion of the elongated electrode coil 86 that does not include the second electrically insulating layer 92 while the second electrically insulating layer 92 is applied. The silicone tubing can then be removed after the second electrically insulating layer 92 is applied. In some examples, the distal-most quarter turn, or 90°, of the elongated electrode coil 86 may not include both the first adhesive layer 90 and the second electrically insulating layer 92.

[0040] In some examples, the thickness of first adhesive layer 90 varies along the distal tip of elongated electrode coil 86, or at other locations on the electrode of device 10 / IMD 80. For example, first adhesive layer 90 may be thickest on the ground, distal-facing surface of the tip of elongated electrode coil 86 and thinnest on the opposite side of elongated electrode coil 86; that is, first adhesive layer 90 may be thickest on the distal-facing aspect of elongated electrode coil 86.

[0041] In some examples, the coating 94 is also applied to one or more surfaces of a portion of the electrode coil 82, such as Figure 4 The thickness of the second electrically insulating layer 92 can be substantially uniform over the portion of the electrode coil surface 84 to which the coating 94 is applied. In some examples, the thickness of the second electrically insulating layer 92 can be substantially uniform over the entire surface of the portion of the electrode coil 82.

[0042] The first adhesive layer 90 can be applied by first depositing a porous titanium nitride coating having a thickness ranging from 100 nanometers to 5 microns onto a spiral platinum alloy (e.g., platinum / iridium) electrode such as the elongated electrode coil 86. The first adhesive layer 90 can then serve as a 3D adhesion promoter layer on the elongated electrode coil 86. A second electrically insulating layer 92 can then be deposited and bonded to the 3D first adhesive layer 90 to form an adhesion-enhanced parylene having a thickness ranging from 100 nanometers to 10 microns. In some examples, a plasma cleaning process is applied after applying the first adhesive layer 90 and before applying the second electrically insulating layer 92. The plasma cleaning process can use a gas plasma to remove contaminants and impurities, such as dirt, dust, oil, and organic materials, from the elongated electrode coil surface 88 and the first adhesive layer 90 without damaging the elongated electrode coil surface 88 and the first adhesive layer 90. In addition, the plasma cleaning process can help remove surface contaminants, such as ionic contaminants or hydrocarbons, that are typically difficult to remove using other methods.

[0043] Figure 6 is a flow chart illustrating an example technique for forming an implantable medical device including a coated electrode. The technique includes applying a first adhesive layer comprising porous titanium nitride to one or more surfaces of the electrode at a first time (200). The first adhesive layer may be substantially similar to Figure 5 The first adhesive layer 90. The electrode can be substantially similar to Figure 1 、 Figure 2 and Figure 3 The first electrode 26 or Figure 4 The elongated electrode coil 86. One or more surfaces of the electrode may be substantially similar to Figure 4 The technique also includes applying a plasma cleaning process to the first adhesive layer (202) at a second time after the first time. The technique also includes applying a second electrically insulating layer comprising parylene to one or more surfaces (204) of the electrode coated with the first adhesive layer at a third time after the second time. The second electrically insulating layer may be substantially similar to Figure 5 The second electrically insulating layer 92 may be applied with a uniform thickness over the entire coating.

[0044] Various embodiments have been described. This disclosure includes the following non-limiting examples.

[0045] Example 1. An implantable medical device comprising: an electrode; a power source; an electrical pacing circuit coupled to the power source and configured to deliver cardiac pacing therapy; and a coating applied to one or more surfaces of the electrode, wherein the coating comprises a first adhesive layer comprising porous titanium nitride and a second electrically insulating layer comprising parylene, and wherein a plasma cleaning process is applied to the first adhesive layer prior to the second electrically insulating layer.

[0046] Embodiment 2. The implantable medical device of embodiment 1, wherein the thickness of the second electrically insulating layer is substantially uniform throughout the coating.

[0047] Embodiment 3. The implantable medical device of Embodiment 1 or 2, wherein the electrode is an elongated electrode configured to extend distally from a distal portion of the implantable medical device.

[0048] Example 4. An implantable medical device according to Example 1 or 3, wherein the electrode includes a first electrode, and the implantable medical device further includes a second electrode located on the distal portion of the implantable medical device, wherein the length of the second electrode is less than the length of the slender electrode, and wherein the second electrode performs one of the following operations: extends from the distal portion of the implantable medical device a distance less than the slender electrode, or is flush with the distal portion of the implantable medical device.

[0049] Example 5. An implantable medical device according to Examples 1 to 4, wherein the first adhesive layer comprising porous titanium nitride is applied to one or more surfaces of an electrode at a first time, wherein the plasma cleaning process is applied to the first adhesive layer at a second time after the first time, and wherein the second electrically insulating layer comprising polyparaxylene is applied to one or more surfaces of an electrode coated with the first adhesive layer at a third time after the second time.

[0050] Embodiment 6. The implantable medical device of embodiments 1 to 5, wherein the first adhesive layer comprising porous titanium nitride forms a fractal surface beneath the second electrically insulating layer comprising parylene.

[0051] Example 7. An implantable medical device according to any one or more of Examples 1 to 6, wherein the implantable medical device is configured as a leadless pacemaker, the leadless pacemaker comprising a housing for the power source and the electrical pacing circuit, and wherein the electrodes extend from the housing.

[0052] Embodiment 8. The implantable medical device of embodiments 1 to 7, wherein the electrode comprises an alloy including platinum and iridium.

[0053] Embodiment 9. The implantable medical device of embodiments 1 to 8, wherein the electrode is configured as a coil comprising a plurality of turns of at least one filament.

[0054] Embodiment 10. The implantable medical device of embodiment 9, wherein the coil forms a helix.

[0055] Embodiment 11. The implantable medical device of embodiments 1 to 10, wherein the first adhesive layer comprising porous titanium nitride has a thickness ranging from 100 nanometers to 5 micrometers.

[0056] Embodiment 12. The implantable medical device of embodiments 1 to 11, wherein the second electrically insulating layer comprising parylene has a thickness in the range of 100 nanometers to 10 micrometers.

[0057] Embodiment 13. The implantable medical device of embodiments 1 to 12, wherein the first adhesive layer comprising porous titanium nitride is thermally bonded to the second electrically insulating layer comprising parylene.

[0058] Example 14. A method for forming an implantable medical device, the implantable medical device comprising: an electrode, a power source, an electrical pacing circuit coupled to the power source and configured to deliver cardiac pacing therapy, and a coating applied to one or more surfaces of the electrode, wherein the coating comprises a first adhesive layer comprising porous titanium nitride and a second electrically insulating layer comprising polyparaxylene, and wherein a plasma cleaning process is applied to the first adhesive layer before the second electrically insulating layer, the method comprising: at a first time, applying the first adhesive layer comprising porous titanium nitride to the one or more surfaces of the electrode; at a second time after the first time, applying the plasma cleaning process to the first adhesive layer; and at a third time after the second time, applying the second electrically insulating layer comprising polyparaxylene to one or more surfaces of the electrode coated with the first adhesive layer.

[0059] Embodiment 15. The method of embodiment 14, wherein the thickness of the second electrically insulating layer is substantially uniform throughout the coating.

[0060] Example 16. The method of Example 14 or 15, wherein the electrode is an elongated electrode configured to extend distally from a distal portion of the implantable medical device.

[0061] Example 17. A method according to Examples 14 to 16, wherein the electrode includes a first electrode, and the implantable medical device further includes a second electrode located on the distal portion of the implantable medical device, wherein the length of the second electrode is less than the length of the slender electrode, and wherein the second electrode performs one of the following operations: extends from the distal portion of the implantable medical device a distance less than the slender electrode, or is flush with the distal portion of the implantable medical device.

[0062] Embodiment 18. The method of embodiments 14 to 17, wherein the first adhesive layer comprising porous titanium nitride forms a fractal surface beneath the second electrically insulating layer comprising parylene.

[0063] Example 19. A method according to Examples 14 to 18, wherein the implantable medical device is configured as a leadless pacemaker device, the leadless pacemaker device comprising a housing for the power source and the electrical pacing circuit, and wherein the electrodes extend from the housing.

[0064] Embodiment 20. The method of embodiments 14 to 19, wherein the electrode comprises an alloy including platinum and iridium.

[0065] Embodiment 21. The method of embodiments 14 to 20, wherein the electrode is configured as a coil comprising multiple turns of at least one filament.

[0066] Embodiment 22. The method of embodiment 21, wherein the coil forms a helix.

[0067] Embodiment 23. The method of embodiments 14 to 22, wherein the first adhesive layer comprising porous titanium nitride has a thickness ranging from 100 nanometers to 5 micrometers.

[0068] Embodiment 24. The method of embodiments 14 to 23, wherein the second electrically insulating layer comprising parylene has a thickness in a range from 100 nanometers to 10 micrometers.

[0069] Embodiment 25. The method of embodiments 14 to 24, wherein the first adhesive layer comprising porous titanium nitride is thermally bonded to the second electrically insulating layer comprising parylene.

[0070] Embodiment 26. The method of embodiments 14 to 25, wherein applying the second electrically insulating layer comprises applying the second electrically insulating layer with a uniform thickness across the entire coating layer of the coating.

[0071] Example 27. An implantable medical device comprising: a power source; an electrical pacing circuit coupled to the power source and configured to deliver cardiac pacing therapy; a first electrode configured to extend distally from a distal portion of the implantable medical device; a second electrode positioned on the distal portion of the implantable medical device; and a coating, wherein the coating comprises a first adhesive layer comprising porous titanium nitride and a second electrically insulating layer comprising polyparaxylene, and wherein a plasma cleaning process is applied to the first adhesive layer prior to the second electrically insulating layer.

[0072] Embodiment 28. The implantable medical device of Embodiment 27, wherein the coating is applied to one or more surfaces of the first electrode and the second electrode.

[0073] Embodiment 29. The implantable medical device of Embodiment 27 or 28, wherein the thickness of the second electrically insulating layer is substantially uniform throughout the coating.

[0074] Embodiment 30. The implantable medical device of Embodiments 27 to 29, wherein the first electrode is an elongated electrode.

[0075] Example 31. An implantable medical device according to Examples 27 to 30, wherein the length of the second electrode is less than the length of the slender electrode, and wherein the second electrode performs one of the following operations: extends a distance less than the slender electrode from the distal portion of the implantable medical device, or is flush with the distal portion of the implantable medical device.

[0076] Example 32. An implantable medical device according to Examples 27 to 31, wherein the first adhesive layer comprising porous titanium nitride is applied to one or more surfaces of the first electrode at a first time, wherein the plasma cleaning process is applied to the first adhesive layer at a second time after the first time, and wherein the second electrically insulating layer comprising polyparaxylene is applied to one or more surfaces of the first electrode coated with the first adhesive layer at a third time after the second time.

[0077] Embodiment 33. The implantable medical device of embodiments 27 to 32, wherein the first adhesive layer comprising porous titanium nitride forms a fractal surface beneath the second electrically insulating layer comprising parylene.

[0078] Embodiment 34. The implantable medical device of Embodiments 27 to 33, wherein the first electrode is configured as a coil comprising a plurality of turns of at least one filament.

[0079] Embodiment 35. The implantable medical device of embodiment 34, wherein the coil forms a helix.

[0080] Embodiment 36. The implantable medical device of embodiments 27 to 35, wherein the first adhesive layer comprising porous titanium nitride has a thickness ranging from 100 nanometers to 5 micrometers.

[0081] Embodiment 37. The implantable medical device of Embodiments 27 to 36, wherein the second electrically insulating layer comprising parylene has a thickness in the range of 100 nanometers to 10 micrometers.

[0082] Example 38. An implantable medical device according to Examples 27 to 37, wherein the first electrode is configured to extend from the distal portion of the implantable medical device and penetrate the wall tissue of the first heart chamber into the wall tissue of the second heart chamber.

[0083] Example 39. An implantable medical device according to Examples 27 to 38, wherein the second electrode is configured to extend from a distal portion of the implantable medical device and flexibly maintain contact with the wall tissue of the first heart chamber without penetrating the wall tissue of the first heart chamber.

[0084] Embodiment 40. The implantable medical device of Embodiments 27 to 39, wherein the thickness of the second electrically insulating layer is substantially uniform throughout the coating.

Claims

1. An implantable medical device, comprising: electrode; Power source; an electrical pacing circuit coupled to the power source and configured to deliver cardiac pacing therapy; and A coating is applied to one or more surfaces of the electrode, wherein the coating comprises a first adhesive layer comprising porous titanium nitride and a second electrically insulating layer comprising parylene, and wherein a plasma cleaning process is applied to the first adhesive layer before the second electrically insulating layer.

2. The implantable medical device of claim 1, wherein the thickness of the second electrically insulating layer is substantially uniform throughout the coating.

3. The implantable medical device of claim 1 or 2, wherein the electrode is an elongated electrode configured to extend distally from a distal portion of the implantable medical device.

4. An implantable medical device according to any one or more of claims 1 to 3, wherein the electrode comprises a first electrode, and the implantable medical device further comprises a second electrode located on the distal portion of the implantable medical device, wherein the length of the second electrode is less than the length of the elongated electrode, and wherein the second electrode performs one of the following operations: extends a lesser distance from the distal portion of the implantable medical device than the elongated electrode, or is flush with the distal portion of the implantable medical device.

5. The implantable medical device according to any one or more of claims 1 to 4, wherein the first adhesive layer comprising porous titanium nitride is applied to the one or more surfaces of the electrode at a first time, wherein a plasma cleaning process is applied to the first adhesive layer at a second time after the first time, and wherein the second electrically insulating layer comprising parylene is applied to the one or more surfaces of the electrode coated with the first adhesive layer at a third time after the second time.

6. The implantable medical device according to any one or more of claims 1 to 5, wherein the first adhesive layer comprising porous titanium nitride forms a fractal surface beneath the second electrically insulating layer comprising parylene.

7. An implantable medical device according to any one or more of claims 1 to 6, wherein the implantable medical device is configured as a leadless pacemaker device, the leadless pacemaker device comprising a housing for the power source and the electrical pacing circuit, and wherein the electrodes extend from the housing.

8. The implantable medical device of any one or more of claims 1 to 7, wherein the electrode comprises an alloy including platinum and iridium.

9. An implantable medical device according to any one or more of claims 1 to 8, wherein the electrode is configured as a coil comprising a plurality of turns of at least one filament.

10. The implantable medical device of claim 9, wherein the coil forms a helix.

11. The implantable medical device according to any one or more of claims 1 to 10, wherein the first adhesive layer comprising porous titanium nitride has a thickness in the range of 100 nanometers to 5 micrometers.

12. The implantable medical device according to any one or more of claims 1 to 11, wherein the second electrically insulating layer comprising parylene has a thickness in the range of 100 nanometers to 10 micrometers.

13. The implantable medical device of any one or more of claims 1 to 12, wherein the first adhesive layer comprising porous titanium nitride is thermally bonded to the second electrically insulating layer comprising parylene.

14. A method for forming an implantable medical device, the implantable medical device comprising: an electrode, a power source, an electrical pacing circuit coupled to the power source and configured to deliver cardiac pacing therapy, and a coating applied to one or more surfaces of the electrode, wherein the coating comprises a first adhesive layer comprising porous titanium nitride and a second electrically insulating layer comprising parylene, and wherein a plasma cleaning process is applied to the first adhesive layer before the second electrically insulating layer, the method comprising: applying the first adhesive layer comprising porous titanium nitride to the one or more surfaces of the electrode at a first time; applying the plasma cleaning process to the first adhesive layer at a second time after the first time; and At a third time after the second time, a second electrically insulating layer comprising parylene is applied to the one or more surfaces of the electrode coated with the first adhesive layer. 15 . The method of claim 14 , wherein the first adhesive layer comprising porous titanium nitride has a thickness ranging from 100 nanometers to 5 micrometers.

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