Medical leads and techniques for manufacturing the same

In some examples, the disclosure relates to a medical device comprising a lead including an electrically conductive lead wire; and an electrode electrically coupled to the lead wire, the electrode including a substrate and a coating on an outer surface of the substrate, wherein the lead wire is formed of a composition comprising titanium or titanium alloys, wherein the substrate is formed of a composition comprising one or more of titanium, tantalum, niobium, and alloys thereof, wherein the coating comprises at least one of Pt, TiN, IrOx, and poly(dioctyl-bithiophene) (PDOT). In some examples, the lead wire may be coupled to the lead wire via a weld, such as, e.g., a laser weld.

TECHNICAL FIELD

The present disclosure relates to medical devices, more particularly to medical device leads and electrodes configured for delivery of electrical stimulation therapy and/or sensing of electrical signals.

BACKGROUND

Medical devices may be used to treat a variety of medical conditions. Medical electrical stimulation devices, for example, may deliver electrical stimulation therapy to a patient via implanted electrodes. Electrical stimulation therapy may include stimulation of nerve, muscle, or brain tissue, or other tissue within a patient. An electrical stimulation device may be fully implanted within the patient. For example, an electrical stimulation device may include an implantable electrical stimulation generator and one or more implantable leads carrying electrodes. Alternatively, the electrical stimulation device may comprise a leadless stimulator. In some cases, implantable electrodes may be coupled to an external electrical stimulation generator via one or more percutaneous leads or fully implanted leads.

SUMMARY

Some examples of the present disclosure relate to medical device leads including one or more electrodes for use in medical device systems. The one or more electrodes may include a surface coating deposited on a titanium or titanium alloy electrode substrate. The electrode substrate may be welded or otherwise coupled to a lead wire of the lead that is also formed of a titanium or titanium alloy. The surface coating may be formed of a Pt, TiN, IrOx, and poly(dioctyl-bithiophene) (PDOT) composition.

In one example, the disclosure relates to a medical device comprising a lead including an electrically conductive lead wire; and an electrode electrically coupled to the lead wire, the electrode including a substrate and a coating on an outer surface of the substrate, wherein the lead wire is formed of a composition comprising titanium or titanium alloys, wherein the substrate is formed of a composition comprising one or more of titanium, tantalum, niobium, and alloys thereof, wherein the coating comprises at least one of Pt, TiN, IrOx, and poly(dioctyl-bithiophene) (PDOT).

In another example, the disclosure relates to a method for forming a medical device lead, the method comprising electrically coupling a lead including an electrically conductive lead wire to an electrode, the electrode comprising a substrate having an outer surface; and depositing a coating on the outer surface of the substrate, wherein the lead wire is formed of a composition comprising titanium or titanium alloys, wherein the substrate is formed of a composition comprising one or more of titanium, tantalum, niobium, and alloys thereof, wherein the coating comprises at least one of Pt, TiN, IrOx, and poly(dioctyl-bithiophene) (PDOT).

DETAILED DESCRIPTION

As described above, some examples of the disclosure relate to medical device leads (also referred to as “medical leads” or “leads”) including one or more electrodes. Using the lead and electrode, a medical device may deliver and/or sense electrical signals to provide therapy to a patient to treat a patient condition. Medical leads may include a conductive electrode member electrically and mechanically connected to one or more conductive lead wires extending through the lead body. Electrical stimulation from a medical device may be conductive along the lead to be delivered across the electrode surface.

In some examples, the electrode and lead wires of a medical lead may each be formed of materials having substantially the same or similar composition. For example, one lead design includes one or more platinum iridium electrodes mounted on the distal end of a lead including a platinum or platinum iridium (Pt—Ir) lead wire. Each of the electrodes may be electrically and mechanically coupled to the Pt—Ir lead wire via lasing welding. In some examples, bare Pt-10Ir may be used as an electrode material for medical device leads. However, in some instances, a Pt-10Ir electrode may not support high charge injection density without inducing corrosion on the electrode itself, e.g., in certain applications where the charge density limit requirement is relatively very high. Further, in addition to being relatively expensive in comparison to other metals, in order to suit more magnetic resonance imaging (MRI) compatible medical device systems, materials other than that of Pt—Ir lead wires and electrodes may be desirable.

In some instances, conductor materials such as titanium alloys (e.g., Ti-15Mo) or other low modulus beta titanium alloys, which have high electrical resistance to help reduce MRI induced heating of tissue adjacent to electrodes, may be used to form a lead wire. Further, Ti and Ti alloys, and Ti-15Mo alloys in particular, may exhibit superior fatigue life, e.g., as compared to that of Pt or Pt—Ir lead wires. However, such materials may not be desirable to form the portion of the lead electrode in direct contact with body tissue. For example, in some instances, Ti and alloys may have a relatively low charge density compared to that of Pt based alloys, which may decrease the effectiveness for delivering electrical stimulation.

While providing for MRI compatibility in a medical lead, laser welding dissimilar metals such as Pt—Ir and titanium alloys can be difficult. For example, micro cracking may occur in an intermetallic layer when a titanium alloy and Pt—Ir are welded together, which may impose a reliability concern.

In accordance with examples of the disclosure, medical lead designs including an electrode formed of substrate comprising one or more of titanium, tantalum, niobium, and alloys thereof that is bonded to a titanium or titanium alloy lead wire. A thin coating may be applied to the outer surface of the electrode substrate. The surface coating may comprise at least one of Pt, TiN, IrOx, and poly(dioctyl-bithiophene) (PDOT). A Pt, TiN, IrOx coating may be applied via any suitable technique including, e.g., sputtering such as vacuum sputtering. Electropolymerization of PDOT may be used to form a conductive coating on the outer surface of the titanium or titanium alloy electrode substrate.

Example coated electrode designs in medical leads may allow may allow for one or more advantages. For example, a surface coated electrode substrate comprising one or more of titanium, tantalum, niobium, and alloys thereof may provide an electrode capable of supporting relatively high charge density limits e.g., due to increased effective surface area and surface roughness compared to that of the surface of the uncoated electrode substrate Moreover, such an electrode may exhibit reduced electrode tissue impedance compared to a bare 90Pt-10Ir electrode. Such an electrode may allow for design freedom such as further miniaturization of parts and reduced pitch of leads. In addition to reduced cost of materials compared to that of the Pt or Pt—Ir electrodes, the electrode substrate may be reliably bonded, e.g., via laser welding, to a titanium or titanium alloy lead wire due the similar compositions. As noted above, a titanium or titanium alloy lead wire may reduce tissue heating adjacent to electrodes during MRI scanning of a medical device system employing such a lead.

FIG. 1is a conceptual diagram illustrating an example stimulation system with a stimulation lead implanted in the brain of a patient. As shown inFIG. 1, stimulation system10includes implantable medical device (IMD)20, lead plug22, lead wire24, lead14and one or more electrodes15implanted within patient12. Specifically, lead14enters through cranium16and is implanted within brain18to deliver DBS. One or more electrodes15of lead14provides electrical pulses to surrounding anatomical regions of brain18in a therapy that may alleviate a condition of patient12. In some examples, more than one lead14may be implanted within brain18of patient12to stimulate multiple anatomical regions of the brain. As shown inFIG. 1, system10may also include a programmer19, which may be a handheld device, portable computer, or workstation that provides a user interface to a clinician. The clinician interacts with e user interface to program stimulation parameters.

For ease of illustration, examples of the disclosure will primarily be described with regard to implantable electrical stimulation leads and implantable medical devices that neurostimulation therapy to a patient's brain in the form of DBS. However, the features and techniques described herein may be useful in other types of medical device systems, which may include other types of implantable medical leads for use with medical devices, such as, e.g., implantable medical devices (IMDs). For example, the features and techniques described herein may be used in systems with medical devices that deliver stimulation therapy to a patient's heart, e.g., pacemakers, and pacemaker-cardioverter-defibrillators. As other examples, the features and techniques described herein may be embodied in systems that deliver other types of neurostimulation therapy (e.g., spinal cord stimulation or sacral nerve stimulation), stimulation of at least one muscle or muscle groups, stimulation of at least one organ such as gastric system stimulation, stimulation concomitant to gene therapy, and, in general, stimulation of any tissue of a patient.

Therapy system10includes medical device programmer14, implantable medical device (IMD)16, lead extension18, and one or more leads20A and20B (collectively “leads20) with respective sets of electrodes24,26. IMD16includes a stimulation therapy module that includes an electrical stimulation generator that generates and delivers electrical stimulation therapy to one or more regions of brain28of patient12via a subset of electrodes24,26of leads20A and20B, respectively. In the example shown inFIG. 1, therapy system10may be referred to as a DBS system because IMD16provides electrical stimulation therapy directly to tissue within brain28, e,g., a tissue site under the dura mater of brain28. In other examples, leads20may be positioned to deliver therapy to a surface of brain28(e.g., the cortical surface of brain28).

In the example shown inFIG. 1, IMD16may be implanted within a subcutaneous pocket above the clavicle of patient12. In other examples, IMD16may be implanted within other regions of patient12, such as a subcutaneous pocket in the abdomen or buttocks of patient12or proximate the cranium of patient12. Implanted lead extension18is coupled to PAD16via connector block30(also referred to as a header), which may include, for example, electrical contacts that electrically couple to respective electrical contacts on lead extension18. The electrical contacts electrically couple the electrodes24,26carried by leads20to16. Lead extension18traverses from the implant site of IMD16within a chest cavity of patient12, along the neck of patient12and through the cranium of patient12to access brain28. Generally, IMD16is constructed of a biocompatible material that resists corrosion and degradation from bodily fluids. IMD16may comprise a hermetic housing34to substantially enclose components, such as a processor, therapy module, and memory.

Leads20may be positioned to deliver electrical stimulation to one or more target tissue sites within brain28to manage patient symptoms associated with a disorder of patient12. Leads20may be implanted to position electrodes24,26at desired locations of brain28through respective holes in cranium32. Leads20may be placed at any location within brain28such that electrodes24,26are capable of providing electrical stimulation to target tissue sites within brain28during treatment. AlthoughFIG. 1illustrates system10as including two leads20A and20B coupled to IMD16via lead extension18, in some examples, system10may include one lead or more than two leads.

Leads20may deliver electrical stimulation via electrodes24,26to treat any number of neurological disorders or diseases in addition to movement disorders, such as seizure disorders or psychiatric disorders. Leads20may be implanted within a desired location of brain28via any suitable technique, such as through respective burr holes in a skull of patient12or through a common burr hole in the cranium32. Leads20may be placed at any location within brain28such that electrodes24,26of leads20are capable of providing electrical stimulation to targeted tissue during treatment. In the examples shown inFIG. 1, electrodes24,26of leads20are shown as ring electrodes. In other examples, electrodes24,26of leads20may have different configurations including segmented electrodes or paddle electrodes. Electrodes24,26of leads20may have a complex electrode array geometry that is capable of producing shaped electrical fields. In this manner, electrical stimulation may be directed to a specific direction from leads20to enhance therapy efficacy and reduce possible adverse side effects from stimulating a large volume of tissue.

In accordance with one or more examples of the disclosure, electrodes24and26may include an electrode substrate formed of a titanium or titanium alloy material. As noted above, in some examples, the electrode substrate for each of electrodes24,26may include a coating deposited on the outer surface of the electrode substrate. The surface coating may comprise at least one of Pt, TiN, IrOx, and poly(dioctyl-bithiophene) (PDOT). The electrode substrates may be mechanically and electrically coupled to a lead wire (not shown) formed of a titanium or titanium alloy material within leads20.

IMD16may deliver electrical stimulation therapy to brain28of patient12according to one or more stimulation therapy programs. A therapy program may define one or more electrical stimulation parameter values for therapy generated and delivered from IMD16to brain28of patient12. Where IMD16delivers electrical stimulation in the form of electrical pulses, for example, the stimulation therapy may be characterized by selected pulse parameters, such as pulse amplitude, pulse rate, and pulse width. In addition, if different electrodes are available for delivery of stimulation, the therapy may be further characterized by different electrode combinations, which can include selected electrodes and their respective polarities. The exact therapy parameter values of the stimulation therapy that helps manage or treat a patient disorder may be specific for the particular target stimulation site (e.g., the region of the brain) involved as well as the particular patient and patient condition.

In addition to delivering therapy to manage a disorder of patient12, therapy system10monitors one or more bioelectrical brain signals of patient12. For example, IMD16may include a sensing module that senses bioelectrical brain signals within one or more regions of brain28. In the example shown inFIG. 1, the signals generated by electrodes24,26are conducted to the sensing module within IMD16via conductors within the respective lead20A,20B. As described in further detail below, in some examples, a processor of IMD16may sense the bioelectrical signals within brain28of patient12and controls delivery of electrical stimulation therapy to brain28via electrodes24,26.

External programmer14wirelessly communicates with IMD16as needed to provide or retrieve therapy information. Programmer14is an external computing device that the user, e.g., the clinician and/or patient12, may use to communicate with IMD16. For example, programmer14may be a clinician programmer that the clinician uses to communicate with IMD16and program one or more therapy programs for IMD16. Alternatively, programmer14may be a patient programmer that allows patient12to select programs and/or view and modify therapy parameters. The clinician programmer may include more programming features than the patient programmer. In other words, more complex or sensitive tasks may only be allowed by the clinician programmer to prevent an untrained patient from making undesired changes to IMD16.

Programmer14may be a hand-held computing device with a display viewable by the user and an interface for providing input to programmer14(i.e., a user input mechanism). In other examples, programmer14may be a larger workstation or a separate application within another multi-function device, rather than a dedicated computing device. For example, the multi-function device may be a notebook computer, tablet computer, workstation, cellular phone, personal digital assistant or another computing device that may run an application that enables the computing device to operate as a secure medical device programmer14.

FIG. 2is a functional block diagram illustrating components of IMD16. In the example shown inFIG. 2, IMD16includes memory40, processor42, stimulation generator44, sensing module46, switch module48, telemetry module50, and power source52. Processor42may include any one or more microprocessors, controllers, digital signal processors (DSPs), application specific integrated circuits (ASICs), field-programmable gate arrays (FPGAs), and discrete logic circuitry. The functions attributed to processors described herein, including processor42, may be provided by a hardware device and embodied as software, firmware, hardware, or any combination thereof.

In the example shown inFIG. 2, sensing module46senses bioelectrical brain signals of patient12via select combinations of electrodes24,26. The output of sensing module46may be received by processor42. In some cases, processor42may apply additional processing to the bioelectrical signals, e.g., convert the output to digital values for processing and/or amplify the bioelectrical brain signal. In addition, in some examples, sensing module46or processor42may filter the signal from the selected electrodes24,26in order to remove undesirable artifacts from the signal, such as noise from cardiac signals generated within the body of patient12. Although sensing module46is incorporated into a common outer housing with stimulation generator44and processor42inFIG. 2, in other examples, sensing module46is in a separate outer housing from the outer housing of IMD16and communicates with processor42via wired or wireless communication techniques. In some examples, sensing module46may sense brain signals substantially at the same time that IMD16delivers therapy to patient14. In other examples, sensing module46may sense brain signals and IMD16may deliver therapy at different times.

Memory40may include any volatile or non-volatile media, such as a random access memory (RAM), read only memory (ROM), non-volatile RAM (NVRAM), electrically erasable programmable ROM (EEPROM), flash memory, and the like. Memory40may store computer-readable instructions that, when executed by processor42, cause IMD16to perform various functions described herein. Memory40may be considered, in some examples, a non-transitory computer-readable storage medium comprising instructions that cause one or more processors, such as, e.g., processor42, to implement one or more of the example techniques described in this disclosure. The term “non-transitory” may indicate that the storage medium is not embodied in a carrier wave or a propagated signal. However, the term “non-transitory” should not be interpreted to mean that memory40is non-movable. As one example, memory40may be removed from IMD16, and moved to another device. In certain examples, a non-transitory storage medium may store data that can, over time, change (e.g., in RAM).

In the example shown inFIG. 2, processor42controls switch module48to sense bioelectrical brain signals with selected combinations of electrodes24,26. In particular, switch module48may create or cut off electrical connections between sensing module46and selected electrodes24,26in order to selectively sense bioelectrical brain signals, e.g., in particular portions of brain28of patient12. Processor42may also control switch module48to apply stimulation signals generated by stimulation generator44to selected combinations of electrodes24,26. In particular, switch module48may couple stimulation signals to selected conductors within leads20, which, in turn, deliver the stimulation signals across selected electrodes24,26. Switch module48may be a switch array, switch matrix, multiplexer, or any other type of switching module configured to selectively couple stimulation energy to selected electrodes22A,22B and to selectively sense bioelectrical brain signals with selected electrodes24,26. Hence, stimulation generator44is coupled to electrodes24,26via switch module48and conductors within leads20. In some examples, however, IMD16does not include switch module48. In some examples, IMD16may include separate current sources and sinks for each individual electrode (e.g., instead of a single stimulation generator) such that switch module48may not be necessary.

Stimulation generator44may be a single channel or multi-channel stimulation generator. For example, stimulation generator44may be capable of delivering, a single stimulation pulse, multiple stimulation pulses or a continuous signal at a given time via a single electrode combination or multiple stimulation pulses at a given time via multiple electrode combinations. In some examples, however, stimulation generator44and switch module48may be configured to deliver multiple channels on a time-interleaved basis. For example, switch module48may serve to time divide the output of stimulation generator44across different electrode combinations at different times to deliver multiple programs or channels of stimulation energy to patient12.

Telemetry module50may support wireless communication between IMD16and an external programmer14or another computing device under the control of processor42. Telemetry module50in IMD16, as well as telemetry modules in other devices and systems described herein, such as programmer14, may accomplish communication by radiofrequency (RF) communication techniques. In addition, telemetry module50may communicate with external programmer14via proximal inductive interaction of IMD16with programmer14. Accordingly, telemetry module50may send information to external programmer14on a continuous basis, at periodic intervals, or upon request from IMD16or programmer14.

Power source52delivers operating power to various components of IMD16. Power source52may include a small rechargeable or non-rechargeable battery and a power generation circuit to produce the operating power. Recharging may be accomplished through proximal inductive interaction between an external charger and an inductive charging coil within IMD16. In some examples, power requirements may be small enough to allow IMD16to utilize patient motion and implement a kinetic energy-scavenging device to trickle charge a rechargeable battery. In other examples, traditional batteries may be used for a limited period of time.

FIG. 3is a conceptual block diagram of an example external medical device programmer14, which includes processor60, memory62, telemetry module64, user interface66, and power source68. Processor60controls user interface66and telemetry module64, and stores and retrieves information and instructions to and from memory62. Programmer14may be configured for use as a clinician programmer or a patient programmer. Processor60may comprise any combination of one or more processors including one or more microprocessors, DSPs, ASICs, FPGAs, or other equivalent integrated or discrete logic circuitry. Accordingly, processor60may include any suitable structure, whether in hardware, software, firmware, or any combination thereof, to perform the functions ascribed herein to processor60.

Memory62may include instructions for operating user interface66and telemetry module64, and for managing power source68. Memory62may also store any therapy data retrieved from IMD16during the course of therapy. Memory62may include any volatile or nonvolatile memory, such as RAM, ROM, EEPROM or flash memory. Memory62may also include a removable memory portion that may be used to provide memory updates or increases in memory capacities. A removable memory may also allow sensitive patient data to be removed before programmer14is used by a different patient.

Memory62may be considered, in some examples, a non-transitory computer-readable storage medium comprising instructions that cause one or more processors, such as, e.g., processor60, to implement one or more of the example techniques described in this disclosure. The term “non-transitory” may indicate that the storage medium is not embodied in a carrier wave or a propagated signal. However, the term “non-transitory” should not be interpreted to mean that memory62is non-movable. As one example, memory62may be removed from programmer14, and moved to another device. In certain examples, a non-transitory storage medium may store data that can, over time, change (e.g., in RAM).

Wireless telemetry in programmer14may be accomplished by RF communication or proximal inductive interaction of external programmer14with IMD16. This wireless communication is possible through the use of telemetry module64. Accordingly, telemetry module64may be similar to the telemetry module contained within IMD16. In alternative examples, programmer14may be capable of infrared communication or direct communication through a wired connection. In this manner, other external devices may be capable of communicating with programmer14without needing to establish a secure wireless connection.

Power source68may deliver operating power to the components of programmer14Power source68may include a battery and a power generation circuit to produce the operating power. In some examples, the battery may be rechargeable to allow extended operation.

FIG. 4is a conceptual diagram illustrating an example medical device lead70for use in a medical device system, such as, e.g., medical device system10ofFIG. 1. Lead70may be substantially the same or similar to that of lead20A or20B ofFIG. 1. For ease of description, lead70will be described with regard to system10ofFIG. 1. As shown, lead70includes a single ring electrode74located on lead body72. Lead body72is formed of an electrically insulating, biocompatible material, such as, e.g., polyurethane or silicone. Lead body72includes a lead wire (not shown inFIG. 4) which runs the length of lead body72and electrically couples electrode74to IMD16for delivery of electrical stimulation and/or sensing of electrical signals as described herein.

FIG. 5is a conceptual diagram illustrating the example medical device lead ofFIG. 4along cross-section A-A. As shown, electrode74includes electrode substrate78and coating76deposited on the outer surface of substrate78. Conversely, the inner surface of substrate78is mechanically and electrically coupled to conductive lead wire80. When implanted in patient12, the outer surface of coating76on electrode substrate78may interface or be in contact with tissue of patient12. Electrical stimulation may be delivered to patient12via electrode74by conducting electrical stimulation generating by IMD16from lead wire80across coating76via electrode substrate78. Likewise, for sensing with electrode74, electrical signals may be transmitted across coating76to lead wire80via substrate78to IMD16.

As noted above, lead wire80may be formed of a composition including titanium or alloys thereof, such as, e.g., Ti-15Mo or other low modulus beta titanium alloys, which have high electrical resistance to reduce heating of tissue adjacent to electrodes during MRI scanning, e. g., as compared to that of Pt, Pt—Ir, or MR35 lead wires. Additionally, as noted above, Ti and Ti alloys, and Ti-15Mo alloys in particular, may exhibit superior fatigue life, e.g., as compared to that of Pt or Pt—Ir lead wires. In some instances, lead wire80may be formed of titanium or alloys thereof, where lead wire80exhibits a wire resistivity greater than approximately 80 μΩ-cm. Example alloying elements may include one or a combination of Mo, Nb, Ta, Zr, Fe, Sn, Fe and Al. In one example, lead wire80may consist essentially of titanium or titanium alloy, where any additionally material in present only in an amount that does not alter one or more properties of the material in a manner that does not allow lead wire80to function as described herein.

As noted above, in some examples, it may be desirable for electrode substrate80to be formed of a composition other than that of Pt or alloys thereof, such, as, e.g., Pt—Ir. In particular, substrate78of electrode74may be formed of one or more of titanium, tantalum, niobium, and alloys thereof, such as, e.g., Ti15Mo to allow for conduction of electrical signals from lead wire80as well as allowing for substrate78to be welded, e.g., laser welded, to lead wire80. Example titanium materials for forming substrate78include commercially pure titanium grade 1, 2, 3, and 4 and any other biocompatible Ti alloys. In some examples, substrate78may be formed of Ti—Mo alloy, e.g., wherein Mo is present in between about 5 wt % to about 25 wt %. Other example alloying elements may include Nb, Ta, Zr, Sn, Fe and Al. In some examples, substrate78may have substantially the same composition of that of lead wire80. In one example, substrate is formed on MP35. In one example, substrate78may consist essentially of Ti, where any additionally material in present only in an amount that does not alter one or more properties of the material in a manner that does not allow substrate78to function as described herein.

While the use of one or more of titanium, tantalum, niobium, and alloys thereof to form substrate78may provide for one or more benefits, as noted above, in some examples, Ti and Ti alloys may have a relatively low charge density limits compared to that of Pt based alloys, which may decrease the effectiveness for delivering electrical stimulation. In accordance with one of aspects of this disclosure, coating76may be applied to outer surface of electrode substrate78. The coating of composition may increase the charge density of electrode74by increasing the surface roughness along with providing a fractal morphology that results in large increase effective surface area compared to that of the surface of electrode substrate78. Also, the combination of electrode substrate78and coating may provide for a reduced electrode impedance compared to that of Pt-10Ir electrodes. In some cases, tower over impedance will reduce energy consumption and increase device life.

Coating76on substrate78may be formed of a composition comprising at least one of Pt, TiN, IrOx, and PDOT. For examples utilizing Pt coatings, the composition of coating76may be substantially all Pt or alloyed with one or more elements, such as, e.g., Ir, Rh, and Au. For examples utilizing TiN coatings, the composition of coating76may include any suitable ratio of Ti to N, e.g., a ratio of approximately 1:1. Coating76may have a composition that provide for a relatively large increase in the effective surface roughness and effective surface area compared to that of the uncoated electrode substrate surface. In one example, coating76may consist essentially of one or more of Pt, TiN, IrOx, and PDOT, where any additionally material in present only in an amount that does not alter one or more properties of the material in a manner that does not allow coating76to function as described herein.

Surface coating76may be deposited on the outer surface of substrate78to define any suitable thickness over substrate. For example, coating76may have a thickness between approximately 0.5 micrometers and approximately 15 micrometers. Coating76may have a substantially uniform thickness over the surface of substrate78or, alternatively, may vary in thickness. In some examples, coating76may cover substantially the entire exposed outer surface of substrate78.

Any suitable technique may be used to form coating76on substrate78. For example, coating76may be deposited using sputtering, such as, e.g., vacuum sputtering, PVD, CVD, or plasma enhanced deposition process when the composition of coating76includes one or more of Pt, TiN, or IrOx. As another example, when coating76is formed of conductive PDOT, electropolymerization techniques may be used.

FIGS. 26A-Care schematic diagrams illustrating another example medical device lead82. Lead82includes a plurality of rings electrodes, including electrode86located at the end of the distal section84of lead82. Electrode86may be substantially the same or similar to that of electrode74of lead70described previously.

FIG. 26Billustrates the distal end of lead82. As shown, electrode74includes electrode substrate90with the outer surface coated with coating88. One of the plurality of lead wires of lead82, lead wire92, is welded or otherwise coupled to substrate90. Substrate90, coating88, and lead wire92may be substantially similar to that of substrate78, coating76, and lead wire80of lead70described previously.

FIG. 26Cis a magnified view of lead82showing distal electrode88. As shown, electrode substrate90exhibits a stepped configuration with respect to the bumped surface formed by the welding of lead wire92to substrate90. In this manner, the weld bump does not protrude from the smooth circular cross section of the distal end of lead82after the lead body has been overmolded.

Although examples of the present disclosure have primarily been described with regard to coated ring electrodes, examples are not limited as such. For example, in some cases a lead may include one or more segmented electrodes. The segments electrodes may each include an electrode substrate coupled (e.g., welded) to a lead wire having those compositions described herein. The outer surface of the electrode substrate for each of the segmented electrodes may be coated with those compositions described herein.

As another example, examples of the disclosure may include paddle leads having any suitable shape and configuration. In some examples, each electrode located on the lead may include an electrode substrate coupled (e.g., welded) to a lead wire having those compositions described herein. The outer surface of the electrode substrate for each of the segmented electrodes may be coated with those compositions described herein. In other examples, rather than including an electrode substrate, the outer surface of lead wire may be coated with those compositions described herein, e.g., after the lead wire has been crimped or otherwise modified in a suitable manner.

EXAMPLES

As series of experiments were performed to evaluate one or more aspects related to the present disclosure. In one instance, a series of Ti rods having a diameter of approximately 0.05 inches were coating with various coatings compositions and various thickness via vacuum sputtering. The properties of the sample coated Ti rods were then evaluated. The below table summarizes the samples that were evaluated.

For each sample, high magnification scanning electron microscopy (SEM) images were taken of the surface of the coating. These images are shown in the first or “A’ figures for the set of five figures corresponding to a sample, as indicated in the above table. For example,FIG. 6Ais a SEM image of the surface of the approximately 2 μm Pt coating applied to the surface of the approximately 0.05 inch Ti-15Mo rod. As indicated by the SEM images, each sample including Pt or TiN coatings exhibited highly textured fractal morphology, vastly increasing effective surface area over a bare Pt electrode. The sputtered deposited IrOx coating had rough surface morphology.

The surface of the coated sample then underwent a ramping load microscratch test with a diamond tip, after which two SEM images were taking of the surface of the coating to evaluate the results of the test. These images are shown in the second and third images or “B” and “C” images for the set of five figures corresponding to a sample. As indicated by the SEM images, for each of the samples including a Pt or TiN coating, the coating was ductile and deformable. The microscratch tests showed that both Pt coating and TiN coating have very good adhesion to the substrate rods. Such results indicate that the risk of coating delamination/chipping-off is very low.

Finally, two cross-sectional optical images of each sample where taken. These images are shown in the fourth and fifth images or “D” and “E” images for the set of five figures corresponding to a sample. As indicated by the cross-sectional images, the coating for each sample exhibited a substantially uniform thickness and there was substantially consistent coverage throughout.

Various electrochemical tests were performed to evaluate each sample.FIG. 16is a plot illustrating the open circuit potential of a bare Pt rod and bare Ti-15Mo rod versus the sample coated Ti-15Mo rods in the above table.FIG. 17is a plot illustrating the open circuit potential of a bare Pt rod and bare Ti-Grade 2 rod versus the sample coated Ti-Grade 2 rods in the above table. As shown inFIGS. 16 and 17, both the Ti-15Mo and Ti Grade 2 rods displayed stable open circuit potentials and likely would not undergo active dissolution if substrate is exposed due to mechanical damage or defects (e.g. pinhole) in coating.

FIG. 18is a bode plot generated using electrochemistry impedance spectroscopy (EIS) for a bare Pt rod and bare Ti-15Mo rod versus the sample Pt and TiN coated Ti-1.5Mo rods in the above table. As shown, the application of the Pt and TiN coatings reduced electrode impedance by about one-half order to about two orders of magnitude in the low frequency range.

FIG. 19is a bode plot generated using electrochemistry impedance spectroscopy (EIS) for a bare Pt rod and bare Ti-Grade 2 rod versus the sample Pt and TIN coated Ti-Grade rods in the above table. Again, as shown, the application of the Pt and TiN coatings reduced electrode impedance by about one-half order to about two orders of magnitude in the low frequency range.

FIG. 20is a bar chart illustrating the electrode capacitance determined for each sample as well as bare Pt, bare Ti-15Mo, and bare Ti-Grade 2 rods. As shown, the application of the coating to the sample rods improved electrode capacitance by a minimum of one order of magnitude.

FIG. 21is a plot comparing the cyclic voltammogram for the sample Ti-15Mo rod with a 2 μm Pt coating versus bare Pt rod.FIG. 22is a plot comparing the cyclic voltammogram for the sample Ti-15Mo rod with a 4 μm TiN coating. As shown inFIGS. 21 and 22, there was a significant increase in charge storage capacity when the substrates were coated, which is desirable.

FIG. 23is a plot of charge storage capacity for the Ti15Mo rod with a 2 μm Pt coating determined based on the voltammogram ofFIG. 21. The anodic charge storage capacity was determined to be approximately 24.27 mC/cm2. The cathodic charge storage capacity was determined to be approximately −22.76 mC/cm2for a total charge storage capacity of approximately 47.03 mC/cm2determined for the sample.

FIG. 24is a bar chart summarizing the charge storage capacity determined for each sample coated Ti-15Mo rod along with a bare Pt and bare Ti-15Mo rod. For each sample on the bar chart, the first bar, moving left to right, corresponds to the anodic charge storage capacity, the second bar corresponds to the cathodic charge storage capacity, and the third bar corresponds to the total charge storage capacity. As indicated by the results, the application of the example coatings on the Ti-15Mo rods increased the charge storage capacity for all sample by a minimum of one order of magnitude compared to the bare rods.

FIG. 25is a bar chart summarizing the charge storage capacity determined for each sample coated Ti-Grade 2 rod along with a bare Pt and bare Ti-Grade 2 rod. For each sample on the bar chart, the first bar, moving left to right, corresponds to the anodic charge storage capacity, the second bar corresponds to the cathodic charge storage capacity, and the third bar corresponds to the total charge storage capacity. As indicated by the results, the application of the example coatings on the Ti-Grade 2 rods increased the charge storage capacity for all sample by a minimum of one order of magnitude compared to the bare rods.