Deep brain stimulation lead

The present disclosure discusses a system and methods for a deep brain stimulation lead. More particularly, the disclosure discusses a stimulation lead that includes one or more silicon based barrier layers within a MEMS film. The silicon based barrier layers can improve device reliability and durability. The silicon based barrier layers can also improve adhesion between the layers of the MEMS film.

BACKGROUND OF THE DISCLOSURE

Deep brain stimulation (DBS) is a neurostimulation therapy which involves electrical stimulation systems that stimulate the human brain and body. DBS can be used to treat a number of neurological disorders. Typically DBS involves electrically stimulating a target area of the brain.

SUMMARY OF THE DISCLOSURE

According to one aspect of the disclosure, a neurological lead includes a planar formed, cylindrical film that defines a lumen. The planar formed, cylindrical film includes a distal end, a proximal end, and a plurality of electrodes. The planar formed, cylindrical film can also include a ribbon cable extending from the distal end of the planar formed, cylindrical film into the lumen. The film can include a plurality of layers that can include a first polymeric layer, a first silicon based barrier layer at least partially disposed over the first polymeric layer, and a first metal layer at least partially disposed over the first silicon based barrier layer. Other layers can include a second silicon based barrier layer at least partially disposed over the first metal layer or the first silicon based barrier layer. The second silicon based barrier layer can define a first plurality of through-holes. Another layer can be a second polymeric layer that is at least partially disposed over the second silicon based barrier layer. The second polymeric layer can define a second plurality of through holes. The first plurality of through-holes is substantially aligned with the second plurality of through holes to define each of the plurality of electrodes. The film can also include a second metal layer disposed on the first metal layer.

In some implementations, the first metal layer can form the plurality of electrodes and a plurality of traces. The first metal layer can also form a plurality of contact pads disposed on the ribbon cable. Each of the plurality of contact pads are electrically coupled with at least one of the plurality of electrodes by a trace formed in the first metal layer. The second metal layer can include gold and the first metal layer can include one of platinum and titanium.

The first and second silicon based barrier layers can include at least one of Silicon Nitride, Silicon Oxide, Silicon Carbide, Polysilicon, Amorphous Silicon, Titanium Dioxide, and Titanium III Oxide. A thickness of the first and second silicon based barrier layers can be between about 100 nm and about 2 μm thick.

According to another aspect of the disclosure, a method of forming a neurological lead can include forming a planar film that includes a plurality of electrodes and a ribbon cable extending from a distal end thereof. Forming the film can include depositing a first silicon based barrier layer at least partially over a first polymeric layer and depositing a first metal layer at least partially over the first silicon based barrier layer. The method can also include depositing a second silicon based barrier layer partially over the first metal layer and the first silicon based barrier layer, and then depositing a second polymeric layer at least partially over the second silicon based barrier layer. Forming the film can also include depositing a second metal layer on the first metal layer. The method to form the lead can also include heating the formed planar film and molding the heated planar film into a cylinder, which defines a lumen. The method can also include extending the ribbon cable into the lumen defined by the cylinder.

In some implementations, the method also includes forming the plurality of electrodes and contact pads in the first metal layer. A plurality of traces can electrically couple each of the plurality of contact pads to at least one of the plurality of electrodes. The method can also include depositing the second metal layer on the plurality of contact pads. Each of the plurality of electrodes can be defined by etching a plurality of through holes in the second silicon based barrier layer and the second polymeric layer. The first and second silicon based barrier layers can include at least one of silicon nitride, silicon oxide, silicon carbide, polysilicon, amorphous silicon, titanium dioxide, and titanium III oxide.

According to another aspect of the disclosure a neurological lead can include a planar formed, cylindrical film defining a lumen. The planar formed, cylindrical film can include a distal end and a proximal end. The planar formed, cylindrical film may also include a plurality of electrodes disposed on an outer surface of the formed cylinder and a ribbon cable extending from the distal end of the planar formed, cylindrical film. The ribbon cable can extend into the lumen toward the proximal end of the planar formed, cylindrical film. The lumen of the planar formed, cylindrical film can be filled with an encapsulating polymer, and a tube body can be coupled with the proximal end of the planar formed, cylindrical film.

The lead can also include a plurality of contact pads disposed on the ribbon cable. Each of the plurality of contact pads can be electrically coupled to at least one of the plurality of electrodes. The lead can also include a gold layer disposed on each of the plurality of contact pads. The gold layer can be between about 5 μm and about 50 μm thick. The lead can also include a peripheral trace partially surrounding each of the plurality of electrodes and coupled with each of the plurality of electrodes at two or more locations.

In some implementations, the lead can include one or more orientation marks that are aligned with a directional electrode or the ribbon cable. The one or more orientation marks can be radiopaque.

In some implementations, the at least one of the plurality of electrodes includes a mesh configuration. One of the plurality of electrodes can include rounded corners.

According to another aspect of the disclosure, a method of manufacturing a neurological lead can include providing a planar film comprising a distal end, a proximal end, a plurality of electrodes, and a ribbon cable extending from the distal end of the planar film. The method can include forming the planar film into a cylinder that defines a lumen. The ribbon cable can be extended into the lumen defined by the cylinder, and then the lumen is filled with an encapsulating polymer.

The method can also include heating the planar film. In some implementations, the proximal end of the planar film is coupled with a catheter. The ribbon cable can be coupled with the stylet in some implementations. The method can also include disposing a radiopaque dye on the planar film.

DETAILED DESCRIPTION

The various concepts introduced above and discussed in greater detail below may be implemented in any of numerous ways, as the described concepts are not limited to any particular manner of implementation. Examples of specific implementations and applications are provided primarily for illustrative purposes.

FIG. 1illustrates an example system50for performing neurostimulation. The system50includes a stimulation lead100implanted into the brain124of a patient102. The stimulation lead100is coupled with a stimulator122through cables126. The stimulator122generates therapeutic, electrical stimulations that can be delivered to the patient's brain124by the stimulation lead100.

FIG. 2illustrates an example stimulation lead100. The stimulation lead100includes a body150. The body150may also be referred to as a tube body, tube, or catheter. The body150includes a number of orientation marks156. At a distal end105, the stimulation lead100includes a MEMS film110. At a proximal end180, the stimulation lead100includes a plurality of contacts190.

At the proximal end180of the stimulation lead100, the stimulation lead100includes one or more contacts190. The contacts190can be used to establish an electrical connection between the electrodes of the MEMS film110and the implanted stimulator122. For example, each of the contacts190can be coupled with one or more electrodes of the MEMS film110. The stimulator122may then couple with the contacts190through a plurality of cables126to stimulate tissue or record physiological signals.

The distal end105of the stimulation lead100can include a MEMS film110.FIG. 3Aillustrates the distal end105and example MEMS film110in greater detail. The MEMS film110can be wrapped or assembled around the distal end105of the body150or formed into a semi-rigid cylinder that is coupled to the end of the body150. The MEMS film110includes a plurality of electrodes120. The MEMS film110can also include a ribbon cable125that wraps over the most distal end of the MEMS film110and extends into a lumen defined by the MEMS film110. As described below, the ribbon cable125is coupled with one or more lead wires160. A portion of the length of the lead wires160are wrapped around a stylet153.

The MEMS film110can include one or more electrodes120. As illustrated, the MEMS film110includes 12 electrodes. In some implementations, the MEMS film110can include between about 6 and about 64 electrodes, between about 8 and about 32, between about 8 and about 24, or between about 8 and about 12 electrodes. The electrodes120can be configured as directional or omnidirectional electrodes. Omnidirectional electrodes may wrap substantially around (e.g., at least 80%, or at least 90%) the circumference MEMS film110when the MEMS film110is formed into a cylinder, and the directional electrodes may wrap only around a portion of the circumference (e.g., less than 80%) the planar formed, cylindrical MEMS film110. One or more directional electrodes can electrically couple to form an omnidirectional electrode. For example, the three distal most electrodes120may be electrically coupled together to form an omnidirectional electrode at the tip of the stimulation lead100. In some implementations, the MEMS film110can include a plurality of omnidirectional electrodes and a plurality of directional electrodes. For example, the electrodes120may be configured as two omnidirectional electrodes and six directional electrodes.

Electrical traces can couple each of the electrodes120with one or more of the lead wires160. For example, the traces may run under an insulative layer of the MEMS film110to the ribbon cable125, where the traces terminate and are coupled with the one or more lead wires160. In some implementations, the stimulation lead100includes one lead wire160for each of the electrodes120. In other implementations, the stimulation lead100includes fewer lead wires160than electrodes120because one or more of the lead wires160are electrically coupled with more than one of the electrodes120. For example, when the MEMS film110includes two omnidirectional electrodes and six directional electrodes, the stimulation lead100may include eight lead wires160. The lead wires160can run along the length of the body150toward the proximal end180of the body150. The lead wires160may traverse the length of the body150in the lumen of the body150. At the proximal end180of the MEMS film110, the lead wires160may be electrically coupled with the contacts190.

FIG. 3Billustrates the underside of the distal end105of the stimulation lead100. In some implementations, the MEMS film110can be initially formed as a planar film that is formed into a cylinder. This method of forming the MEMS film110can create a connecting seam111.

The MEMS film can include a plurality of layers. In some implementations, the MEMS film includes five layers. The five layers can include a first polymeric layer and a first silicon based barrier layer that is at least partially deposited (or otherwise disposed) over the first polymeric layer. The MEMS film110can also include a first metal layer that is at least partially deposited (or otherwise disposed) over the first silicon based barrier layer. Other layers can include a second silicon based barrier layer at least partially deposited (or otherwise disposed) over the first metal layer and the first silicon based barrier layer. The second silicon based barrier layer can define a first plurality of through-holes over portions of the first metal layer. Another layer of the MEMS film110can be a second polymeric layer that is at least partially deposited (or otherwise disposed) over the second silicon based barrier layer. The second polymeric layer can also define a plurality of through holes. The plurality of through-holes of the second silicon based barrier layer and the second polymeric layer are substantially aligned to define each of the plurality of electrodes120and contact pads145of the MEMS film110.

FIG. 4illustrates a flow chart of an example method400for manufacturing a stimulation lead. The method400can include forming a planar MEMS film (step401). The planar MEMS film can then be molded into a cylinder (step402). A ribbon cable of the MEMS film may then be extended into a lumen of the molded cylinder (step403). The molded MEMS film may then be coupled with a lead body (step404).

As set forth above, the method400can begin with the forming of a planar MEMS film (step401). The planar MEMS film may be a planar version of the MEMS film110. The planar MEMS film can be referred to generically as the MEMS film110. In some implementations, the MEMS film110includes a plurality of layers. The MEMS film110can include one or more polymeric layers, one or more silicon based barrier layers, and one or more metal layers. For example, the MEMS film110can include a first polymeric layer, a first silicon based barrier layer, a first metal layer, a second silicon based barrier layer, a second polymeric layer, and a second metal layer. The silicon based barrier layers can improve adhesion of the layers, improve scratch resistance of the metal layers, and impede the flow of ions and humidity between the layers. Ions and humidity can traverse a polymeric layer and cause electrical short circuits in the metal layer of a MEMS device. The silicon based barrier layers can prevent or reduce the flow of ions and the introduction of humidity into or between the layers. Accordingly, the reduction of ion flow and humidity between the layers by the silicon based barrier layers can improve the performance and durability of the MEMS film110.

FIGS. 5A-5Millustrate an example method for manufacturing the MEMS film110. More particularly,FIGS. 5A-5Millustrate a cross-sectional view of an example thin-film micro-fabrication method for fabricating the MEMS film110. The MEMS film110can be fabricated using a plurality of techniques and the below describe method illustrates one possible method for fabricating the MEMS film110. The fabrication procedure can include a series of procedural steps in which various layers are deposited or removed (e.g., etched) to achieve a final form. The cross sections inFIG. 5AthroughFIG. 5Mdemonstrate the process steps to build a MEMS film110.

In a first step illustrated inFIG. 5A, a carrier substrate201is provided, such as a wafer composed of a crystalline material, such as silicon, or an amorphous material, such as a thermal shock resistant borosilicate glass or other suitable smooth supportive material. A first layer202, which can include one or more sub-layers, is applied to a surface of the wafer201. One of the sub-layers can be a sacrificial layer deposited on the wafer201, which is removed in a subsequent electrochemical etching step. In some implementations, the sacrificial sub-layer is preceded by another sub-layer, referred to as an underlayer, which can serve to form the electrochemical cell required to etch the sacrificial layer. The sacrificial sub-layer can be aluminum, or an alloy of aluminum such as AlSi, which has a smaller granularity, whereas the underlayer can be a TiW alloy such as Chrome or similar metal. In some implementations, when the sacrificial sub-layer is not implemented, the removal of the resulting device from the substrate is difficult and could result in damage to the finished device.

Referring toFIG. 5B, the next step in the fabrication process can include depositing a first polymeric layer205. The first polymeric layer205can be deposited upon the sacrificial layer202by MEMS processes such as, but not limited to, (i) spin coating a liquid polymer precursor such as Polyimide or Silicone precursor; (ii) depositing a polymer through chemical vapor deposition as is done with parylene-C; or (iii) laminating a polymer sheet onto the wafer. In some embodiments, the polymer layer205is heated, or baked, to polymerize. In some implementations, the first polymeric layer205includes polyamic-acid dissolved in NMP and spun onto the sacrificial layer202in liquid form. The polymeric layer205is heated into a imidized polyimide. The polymer in its cured form is between about 5 μm and about 15 μm thick. The polymer layers of the MEMS film can serve as a barrier to water, humidity, and isolate the components of the MEMS film.

FIG. 5Cillustrates the deposition of a silicon based barrier layer. The silicon based barrier layer can serve both as a layer to aid the adhesion and durability of subsequent layers. The silicon based barrier layer can also serve as an ionic barrier, and limit ions from reaching the metal layers, which could compromise electrical performance. The silicon based barrier layer can also block humidity from reaching the interlayers and the metal layer, which could create short circuits and compromise electrical isolation.

In some implementations, the silicon based barrier layer is deposited onto the first polymeric layer205by vapor deposition techniques such as chemical vapor deposition (CV) and plasma enhanced chemical vapor deposition (PECVD), or by sputtering techniques such as direct current (DC) or RF (Radio Frequency) sputtering. The silicon based barrier layer can include Silicon Nitride, Silicon Oxide, Silicon Carbide, Poly-Silicon, or Amorphous-Silicon. The silicon based barrier layer can also include other non-conductive materials, such as Titanium Dioxide or Titanium (III) Oxide. The final thickness of the silicon based barrier layer can range from about 20 nm to about 2 μm. In some implementations, the silicon based barrier layer is about 400 nm to about 600 nm, which can permit the silicon based barrier layer to be flexible enough to bend during subsequent assembly techniques.

Now referring toFIG. 5D, a metal layer215can be deposited over the entire wafer on the surface of the silicon based barrier layer210. Subsequently, a photoresist layer217can be deposited. The photoresist layer217can be defined by exposing areas of the photoresist layer217to ultra-violet light and developing those areas in a solvent. Thus, the exposed areas of the photoresist layer217will be selectively removed and areas of the metal layer215will be exposed. The areas of the metal layer215covered by the photoresist layer217can form the electrodes, traces, and other components of the final product that are within the metal layer.

The metal layer215can include a variety of metals such as titanium, platinum, gold, and others metals used in neuromodulation. To improve adhesion of a metal layer215, the metal layer215can be applied in layers. For example, the metal layer215can be applied as a first layer, such as titanium, then a middle layer, such as platinum, and finally an upper layer, such as titanium. This tri-layer metal structure can improve adhesion below and above the platinum layer by using the titanium as an adhesion layer to the silicon based barrier layer. The typical thicknesses for the adhesion layer of titanium can be between about 20 nm and about 100 nm or between about 25 nm and about 75 nm. Typical thicknesses for the platinum layer can be between about 200 nm and about 7 μm, between about 400 nm and about 5 μm, between about 400 nm about 3 μm, between about 400 nm and about 1 μm, or between about 400 nm and about 700 nm. In some implementations platinum can be replaced by another, high charge transfer capable material such as iridium oxide.

FIG. 5Eillustrates the process after the etching of the metal layer215. As illustrated, the metal layer215can be locally removed in the areas that were not covered by the photoresist217. In some implementations, etching of the metal layer is performed in a plasma etcher such as a Reactive Ion Etcher. In some implementations, titanium and platinum can be etched with chlorine gas. After the etching process is finished, the photoresist layer217can be removed using a solvent.

Another method to deposit and define the metal layer is using the so-called “lift off” technique. In this method the photoresist layer can be deposited onto the silicon based barrier layer210first. The photoresist layer can be defined using photolithography. The metal layer215can then be deposited through this “lift off” mask, and the remaining photoresist removed in a solvent. In this method the metal layer is transferred onto the silicon based barrier layer without the need of plasma etching and may have some process costs and speed advantages.

Referring next toFIG. 5F, a deposition of a second barrier layer220is performed. The second barrier layer can be deposited using the same techniques as the first silicon based barrier layer210. The second barrier layer220can be the same thickness, or a different thickness as the first silicon based barrier layer. In some implementations, the second silicon based barrier layer is optional. The second silicon based barrier layer220and the first silicon based barrier layer210can substantially surround (e.g., at least 80%) the metal layer215, rendering it electrically isolated. In order to etch and define the first and second silicon based barrier layer210and220, respectively, a second photoresist layer227is deposited and photolithographically defined with clean room techniques.

The two silicon based barrier layers are etched, as illustrated inFIG. 5G. The silicon based barrier layers can be etched using a plasma etch. An example of an etching process would be a reactive ion etching using a tetrafluoromethane gas, (CF4). The second photoresist layer227can be removed using a solvent dissolution.

FIG. 5Gillustrates an example where the edges of the silicon based barrier layers210and220are defined, but the etch does not reach the metal layer215. In some implementations the photolithography can include an opening above the metal layer215, which would result in exposing the metal layer215.

FIG. 5Hillustrates the application of a second polymer layer230. The second polymer layer230can be the same or a different polymer from the first polymer layer205, and it can be the same or a different thickness.

FIG. 5Iillustrates the deposition of a third photoresist237, which can form the etching perimeter of the first and second polyimide layers205and230, respectively. In some implementations, prior to the applying the third photoresist237, a sacrificial layer, such as Silicon Dioxide or Silicon Nitride, is deposited in order to serve as an etch mask for the polyimide etch. For example, a silicon dioxide layer of thickness of about 500 nm can be deposited, which will serve as the etch mask for the process.

FIG. 5Jillustrates the result of an oxygen plasma etching of the first and second polyimide layers205and230, respectively. If applied, the silicon dioxide layer can be removed through an additional etch.

FIG. 5Killustrates the deposition of a fourth photoresist layer247. In some implementations, the fourth photoresist layer247does not cover part of the metal layer215. For example, the opening232can be maintained to create a region for a gold layer to grow.

FIG. 5Lillustrates the galvanic growth of a thick gold layer250into the opening232. In some implementations, the gold layer250is achieved by connecting the metal traces in the wafer to a perimetric metal band that allows an electrical connection between the edge of the wafer and the metal opening232. When immersed in a galvanic bath and a current applied, the gold will grow on the metal layer215using the metal layer215as the seed layer for galvanic growth. In some implementations, the gold layer250is about 2 μm to about 20 μm thick. The fourth photoresist layer247can be removed using a solvent.

FIG. 5Millustrates the removal of the MEMS film from the wafer201. The removal of the fourth photoresist layer247exposes the electrode opening233. The MEMS film can be removed from the wafer201by the removal of the sacrificial layer202using electrochemically etching. Removal of the sacrificial layer202frees the underside of the MEMS film from the wafer201. In some implementations, the sacrificial layer202is removed by placing the wafer in a saline bath with a high NaCl concentration. A platinum electrode also placed in the bath can be used as a reference, and a voltage can be applied to the aluminum layer with respect to the platinum electrode. The electrochemical cell created by the aluminum and TiW etches the aluminum—separating the MEMS film from the wafer201.

In some implementations, when the MEMS wafer is completed, and the individual devices have been removed, further process steps can occur before to assemble the wafers into a cylindrical shape.

Referring again toFIG. 4, the method400can also include molding the MEMS film110. In some implementations, the MEMS film110is molded into a cylinder shape that defines a lumen.FIGS. 6A-6Billustrate the MEMS film110being molded into a cylinder.

FIG. 6Aillustrates a planar view of the MEMS Film110. As illustrated, the MEMS film110includes twelve electrodes120. The electrodes120can be generally rectangular in shape with rounded corners. The ribbon cable125extends from the distal end of the MEMS film110. The ribbon cable125can include one or more traces that electrically couple the electrodes120to the contact pads145. In some implementations, each of the contact pads145are electrically coupled with one or more electrodes120.

FIG. 6Billustrates the molded MEMS film110. In some implementations, the MEMS film110is heated to and then molded to form a cylinder. The MEMS film110can be heated and molded using a thermal reflow method. In some implementations, the MEMS film110is heated to about 300° C. when molded. The formed cylinder can have an internal diameter of between about 0.5 mm and about 2 mm, between about 1 mm and about 1.5 mm, or between about 1.3 mm and about 1.5 mm after formed into a cylinder. The cylinder shape of the MEMS film110can be formed by inserting the MEMS film110into a tube with the same diameter that is required for the final device. The MEMS film110, within the tube, can be heated to a temperature which causes the polymer insulator to slightly reflow and take the new form of the tube.

The end of the ribbon cable125can be coupled to a stylet153.FIG. 7Aillustrates the formed MEMS film110coupled to the stylet153. Coupling the MEMS film110to the stylet153can render the distal end of the ribbon cable125rigid and can simplify later assembly steps. For example, coupling the stylet153with the ribbon cable125can ease the coupling of the lead wires160to the contact pads145. The stylet153can include a metallic material (e.g., stainless steel), a ceramic material, or a polymeric material. In some embodiments, the stylet153can be radio-opaque such that the surgeon can visualize the stimulation lead100in an x-ray or CT scan during the implantation process to control the final placement of the stimulation lead100. The stylet153can also be used to determine the rotation of the stimulation lead because the stylet153is partly planar along its longitudinal axis.

FIG. 7Billustrates the lead wires160coupling with the ribbon cable125of the MEMS film110. In some implementations, the lead wires160are coiled around the stylet153. The lead wires160can be coupled with the contact pads145through laser welding, ultrasonic bonding, crimping, thermocompression bonding, or wire bonding. In some implementations, the lead wires160are locally flattened to increase the surface area of the lead wires160that comes into contact with the contact pads145.

FIG. 7Cillustrates the process of wire bonding a lead wire160to a contact pad145. As illustrated, a lead wire160lies across the contact pad145. The insulation at the end of the lead wire160can be removed so the conductor within the lead wire160can make contact with the contact pad145. A wire bond147connects the contact pad145to the lead wire160. A weld can be formed between the wire bond147, the contact pad145, and the lead wire160through the use of heat, pressure, ultrasonic energy, or combinations thereof.

Referring again toFIG. 4, the method400can also include extending the ribbon cable into the lumen formed by the molding of the MEMS film (step403). The ribbon cable125can be folded such that a portion of the ribbon cable125and a portion of the stylet153are disposed within the lumen defined by the formed MEMS film110. In some implementations, the lumen defined by the MEMS film110can be back filled with an encapsulating polymer, such as an epoxy. The MEMS film110can be placed in a cylindrical mold prior to the backfilling with the polymer. Backfilling the MEMS film110can serve to secure the lead wires160in place and electrically encapsulate the connections within the lumen. In some implementations, the backfilling process can also be used to form a cylindrical form to the distal end of the stimulation lead100.

FIG. 8Aillustrates the extension of the ribbon cable into the lumen of the molded MEMS film110. The ribbon cable125can be folded such that a portion of the ribbon cable125and a portion of the stylet153is disposed within the lumen formed by the molded MEMS film110. The portion of the ribbon cable125and the stylet153can be extended into the lumen by temporarily opening the cylinder along the seam111.

FIG. 8Billustrates the MEMS film110after the backfilling process. The lumen defined by the MEMS film110can be backfilled, or co-molded, with a polymeric material. The backfilling process can seal the MEMS film110in place and electrically isolate the lead wires160connected to the contact pads145at the end of the ribbon cable125. The backfilled polymer can fill the interior of the lumen and can also create a distal, hemispherical tip151. In some implementations, an internal cylinder161is added proximal to the backfilling material over the lead wires160. The internal cylinder161can reduce abrupt changes in compliance (e.g., flexibility) in the final device, when transitioning from the flexible lead wires160to the relatively rigid polymeric filling of the back filled MEMS film110.

Referring again toFIG. 4among others, the method400can also include coupling the molded film to a lead body (step404). The body150can couple with the molded MEMS film110by glue or adhesive. In some implementations, the body150can be molded over a portion of the proximal end of the MEMS film110. In addition to securing the body150to the MEMS film110, molding the body150over the MEMS film110can help the MEMS film110maintain a cylindrical shape. The proximal end of the body150can include the one or more contacts190.

FIGS. 9A and 9Billustrate the proximal end180of the stimulation lead100. The proximal end180of the stimulation lead100can include a plurality of contacts190. As illustrate, the proximal end180of the stimulation lead100includes eight contacts190. Each of the contacts190are electrically coupled with at least one of the lead wires160. In some implementations, the proximal end180of the stimulation lead100is stiffer when compared to other portions of the stimulation lead100. The added stiffness of the proximal end180can assist in the coupling of the proximal end180with a stimulator or an extension cable. The stimulation lead100can also include a lumen182, which is illustrated inFIG. 9B. In some implementations, the lumen182runs the length of the stimulation lead100.

FIGS. 10A-10Cillustrate the placement of the orientation mark156along a portion of the body150. The orientation mark156can enable a neurosurgeon to determine the placement and rotation of the stimulation lead100when the stimulation lead100is implanted within the patient. For example, the orientation mark156may enable the neurosurgeon to determine the axial orientation (e.g., rotation) of the stimulation lead100and determine towards what anatomical structure the directional electrodes are facing. In some implementations, the orientation mark156can be a solid line extending the length of the stimulation lead100. The orientation mark156can also include a dashed line or a series of dots.

The orientation mark156can be aligned with a specific feature (or landmark of the stimulation lead100). For example, the orientation mark156can be aligned with a directional electrode120, as illustrated inFIG. 10A. In another example, the orientation mark156can be aligned with the seam111of the MEMS film110, as illustrated inFIG. 10B. The orientation mark156can also be aligned with a gap between two electrodes120or with the ribbon cable125(as illustrated, for example, inFIG. 10C).

The orientation mark156can be a stamped ink line or can be applied to the stimulation lead100during the extrusion body150as a dye, for example. The orientation mark156can alter the reflectivity of the body150and may be implemented as a radiopaque ink or dye in order to provide intra-operative and post-operative imaging. In some embodiments, laser marking can be used to locally change the texture, color, or reflectivity of the body150to serve as the orientation mark156.

The MEMS film110can include a combination of stimulating electrodes and recording electrodes. In some implementations, an electrode120can be recording electrode or a stimulating electrode, or both. For example, to act as a stimulating electrode, the electrode120may be coupled with a stimulator, and to act as a recording electrode, the electrode120may be coupled with an analog-to-digital converter and an amplifier. In some implementations, the recording electrodes and the stimulating electrodes may be shaped or configured differently. For example, the recording electrodes may be smaller in size compared to the stimulating electrodes.

A neurosurgeon may record from one or more of the electrodes120during the implantation of the stimulation lead100. For example, the neurosurgeon may record neurophysiological activity in the beta band (approximately 15-30 Hz) of neural activity because the beta band is closely associated with motor behavior.

FIGS. 11A-11Iillustrate planar MEMS film110configurations that include different electrode designs. Each of the MEMS film110include three columns of electrode120and can therefore record electrical activity in three directions, labeled 0 degrees, 120 degrees, and 240 degrees. The MEMS film110may also include more than three columns of electrodes120to enable the stimulation lead100to record and stimulation in more than three directions. Each of the electrodes120of each of the different MEMS films110can be electrically isolated from one another to form directional electrodes or one or more of the electrodes120can be electrically coupled to one another to form omni-directional electrodes. For reference, when the MEMS films illustrated inFIGS. 11A-11Iare molded into a cylinder, the end of the MEMS film toward the bottom of the page is coupled to the body150.

FIG. 11Aillustrates the MEMS film110configured to have both elongated electrodes120and circular electrodes120. The elongated electrodes can include semicircular ends. In some implementations, the circular electrode may be configured for use as recording electrodes and the elongated electrodes may be configured for stimulating neurological tissue. The recording electrodes can record neurological activity during the surgical descent of the stimulation lead100into the brain. By having recording electrodes close to the stimulation electrode, the electrical activity captured by the recording electrodes after stimulation from the stimulating electrodes can be clinically relevant to the stimulation lead100placement. In some implementations, recording data captured from any or all recording electrodes can be clinically relevant to determine which of the stimulating electrodes should be used to stimulate a specific target.FIG. 11Billustrates a similar implementation, but with electrodes that include rounded corners rather than semicircular ends.

FIG. 11Cillustrates an implementation of a planar MEMS film where the electrodes120are of the same dimensions. In some implementations, the most proximal row of electrodes and most distal rows of electrodes are each electrically interconnected, and therefore each row can act as a circumferential electrode.

FIG. 11Dillustrates a planar MEMS film with electrodes120configured as circular electrodes. The electrodes120configured as circular electrodes may improve charge density considerations around the edges of the electrode.FIG. 11Eillustrates a planar MEMS film with electrodes120configured as circular electrodes of different sizes. The larger circular electrodes may be used for stimulation and the smaller circular electrodes may be used for recording. FIG.11F illustrates a planar MEMS film with electrodes120configured as circular electrodes where the rows are placed closely together.

FIG. 11Gillustrates a planar MEMS film with an electrode arrangement where the electrodes120are configured as elongated electrodes and circular electrodes. The elongated electrodes can be configured as recording electrodes and are interlaced along each row with the circular electrodes, which may be configured as stimulating electrodes.FIG. 11Hillustrates a planar MEMS film with an electrode arrangement where each electrode120includes an inner portion294and an outer portion292. In some implementations, the inner portion is a stimulation electrode and the outer portion292is a recording electrode.FIG. 11Iillustrates a planar MEMS film where each electrode includes four bands299. In some implementations, two or more of the bands299are electrically coupled together.

One or more of the electrodes120can include redundant traces that improve reliability of the stimulation lead100. The electrodes120can be connected to the contact pads145on the end of the ribbon cable125via metal traces that are embedded in the MEMS film110. The traces can have several redundancies around the periphery of the electrode120to reduce the likelihood that the electrode120will become disconnected from the contact pad145to which the electrode120is coupled. This design is demonstrated inFIG. 12, for example, with a simplified embodiment of a MEMS electrode film300.

FIG. 12illustrates a MEMS film with electrodes with redundant periphery traces. As illustrated a metal layer is deposited onto a polymeric layer305. The metal layer can include the contact pads145, the traces315, the periphery traces314, and the electrodes120. Each periphery trace314can extend around the perimeter of an associated electrode120. The periphery trace314can be coupled with an electrode120at a plurality of connection points316. Each electrode120can include four connection points316. In some implementations, each electrode120includes one or more connection points316per edge of the electrode120. For example, the electrodes120illustrated inFIG. 12are squares with four edges and one connection point316per edge. In some implementations, the contact pads145can also be surrounded by a periphery trace314.

FIGS. 13A and 13Billustrate the application of a second polymeric325(or isolating layer) to the first isolating layer305illustrated inFIG. 12. The second polymeric layer325can include a plurality of through holes310that align with the electrodes120and the contact pads145. The silicon based barrier layer that can be deposited over the metal layer can also include a plurality of through holes that align with the through holes310of the second polymeric layer. The second polymeric325can be bonded to the surface of the first polymeric layer305and the metal conductive layer. The second polymeric325can be photolithographically defined. The resulting stack of layers is demonstrated inFIG. 13B, where the electrodes120and corresponding contact pads145are apparent through the through holes310, but the traces315and periphery traces314are hidden from view and electrically isolated from the outside environment.

FIGS. 14A and 14Billustrate equipotential surfaces in an electrode when a voltage is applied at trace boundaries. InFIG. 14A, the electrode is only coupled to a single trace315and does not include a periphery trace314. In some implementations, the junction between the trace315and the electrode120is an area where the applied voltage is highest.FIG. 14Aillustrates the equipotential surfaces332in an electrode120when a voltage is applied at trace315. The potential is concentrated at a corner, near the junction between the trace315and the electrode120. In some implementations, the concentrated potential can contribute to device reliability issues at the junction.FIG. 14Billustrates an electrode120with a peripheral trace314. The peripheral trace314, with four connection points to the electrode120better distributes the potential337throughout the electrode120. The distribution of the potential can increase electrode health and provide redundancies if one of the connection points break.

The electrodes120can include rounded electrode corners to decrease focal points of current density on each of the electrodes120.FIG. 15Aillustrates rectangular electrode120with a voltage applied to the electrode. High current densities can be generated at the corners of the electrode in this example.FIG. 15Billustrates an electrode120with rounded or semicircular ends, which can reduce the current density relative to rectangular corners. Reducing current density can protect the electrode from degradation.

FIGS. 16A and 16Billustrate example rounded corner electrodes with periphery traces.FIG. 16Aillustrates a MEMS film with four rounded corners electrodes120. The electrodes120are connected to contact pads145through the traces315. The trace315are coupled with periphery traces314that enable voltage distribution to be equal at contact points316, and thereby distributed the voltage more evenly across the electrode surface. As illustrated, the periphery traces314do not encircle the perimeter of the electrodes120; however, in some implementations, the periphery traces314can fully encircle the perimeter of the electrodes120.FIG. 16Billustrates the MEMS film with a second polymeric layer375in place, encapsulating the periphery traces314and the traces315.

FIG. 17illustrates a current density distribution in an electrode with rounded corners and coupled to a periphery trace. A rounded corner electrode120is fully surrounded by a periphery trace314. The periphery trace316makes two connections to the electrode120. When a potential is applied to the trace315, the equipotential regions382distribute around the periphery trace316and enter the electrode120at the two connection points. By applying the potential to multiple points of the electrode120, the potential is more evenly distributed across the electrode120.

The electrodes120can include meshes.FIG. 18illustrates a MEMS film110with a plurality of electrodes120configured as mesh electrodes. A mesh electrode configuration can be used to concentrate current density in certain areas of the electrode surface—for example, the center.FIG. 19illustrates an electrode120configured as a mesh electrode. A mesh electrode120can include a plurality of concentric bands. In some implementations, each of the bands are of the same thickness and in other implementations, as illustrated inFIG. 19, each of the bands may be narrower toward the center of the electrode120. Narrowing each of the bands towards the center of the mesh electrode120can increase current density towards the center of the electrode120, and thereby limit the spread of current from the electrode's perimeter. In some implementations, a mesh electrode has the effect of concentrating the volume of tissue being influenced by the electric current to the center of the electrode, therefore increasing the effect of directional stimulation in the patient.

FIG. 20illustrates a mesh electrode configuration with a plurality of bands. The MEMS film420includes a plurality of mesh gradient electrodes427. Each of the mesh gradient electrodes427includes a plurality of electrode bands423. In some implementations, the bands are narrower toward the center of the mesh gradient electrode427. The narrowing of the bands can concentrate current density towards the center of the electrode427.FIG. 21illustrates a finite element analysis model of the current density425around a mesh gradient electrode, which shows that current density is the highest toward the center of the mesh gradient electrode423.FIG. 22illustrates the current density425along an arc length circumferential to the electrode modelled inFIG. 21. The numerical analysis illustrated inFIGS. 21 and 22shows that current density peaks can be shifted away from the periphery of the electrodes and into the center of the electrode using mesh electrodes.

FIG. 23Aillustrates a MEMS film with gradient electrodes turned perpendicular to the length of the stimulation lead100. The gradient mesh electrode427is implemented on the MEMS film to concentrate a volume of the current longitudinally along the MEMS film.FIGS. 23B and 23Cillustrate a finite element analysis model of the electric potential at the surface of the gradient mesh electrode427when in contact with conductive media. The numerical analysis demonstrates that the current density peaks426can be shifted away from the periphery of the electrodes and toward the center of the electrode427using a gradient mesh.FIG. 23Dillustrates the peaks of current density426along the electrode longitude, and suggests that with proper gradient meshing the peaks of high current density can be driven away from the periphery toward the center of the electrode.FIG. 23Eillustrates the difference between current density2301of a non-meshed electrode. The current density2301of the non-meshed electrode includes current density peaks at its periphery. The current density2302of the gradient mesh electrode includes a plurality of peaks toward the center of the electrode.

In some implementations, the gradient mesh configurations increase efficacy of electrical stimulation in human subjects by avoiding side effects and concentrating a stimulation signal on regions of intended targets.

FIGS. 24A and 24Billustrate a MEMS film110configuration without a ribbon cable.FIG. 24Aillustrates a MEMS film110without a ribbon cable in a planar configuration. A contact pad area525extends from the MEMS film110. The contact pad area525a plurality of contact pad145. The electrode120is electrically coupled with one or more contact pads145by traces. The MEMS film110can also include a plurality of vias527(or holes in the MEMS film110). The vias527can aid in assembly, by enabling the encapsulating epoxy to flow around the contact pad area525and fully encapsulate the contact pad area525. The vias527can also improve bending at the junction of the MEMS film110and the contact pad area525.

FIG. 24Billustrates the MEMS Film110after thermal reforming into a cylindrical shape. The molded MEMS film110defines an inner lumen530. The contact pad area525is folded into the lumen530. In some implementations, the lumen530is backfilled with an encapsulating epoxy.

FIG. 25Aillustrates MEMS film without a ribbon cable coupled to a style and coupled with a body150. As illustrated the top portion of the MEMS film without a ribbon cable is removed to view the interior of the lumen defined by the molded MEMS film. The contact pad area525is coupled with a stylet153and lead wires160are coupled with the contact pads145.FIG. 25Billustrates the same embodiment as illustrated inFIG. 25A, but from a different angle. In these and other examples, sections of the MEMS film are removed to illustrate the inner features.

FIG. 25Cillustrates the MEMS Film110without a ribbon cable in an assembled and overmolded state. After the lead wires160are welded in place, MEMS Film110is back-filled with a polymer or epoxy solution to order to fortify the cylindrical shape. The polymer also encapsulates and isolates the lead wires160connections to the contact pads145. In some implementations, the MEMS film without a ribbon cable is more reliable compared to a MEMS film with a ribbon cable. The contact pad area525can also provide more spacing between electrode sites120for traces leading to the contact pads145.

FIGS. 26A-26Hillustrate methods for maintaining the cylindrical shape of the planar formed, cylindrical MEMS film.FIG. 26Aillustrates a MEMS film110that can maintain the cylindrical shape with hooks and clips. The MEMS film110can include two hooks607and two notches605, or other number of hooks or notches.FIG. 26Billustrates the planar formed, cylindrical MEMS film110with the hook607coupled with the notch605. When the MEMS film110is formed into a cylinder, the hook607and notches605on opposite sides of the MEMS film110are aligned with one another. Each hook607can slide into the recess of its matching notch607. In some implementations, the seam of the planar formed, cylindrical MEMS film110may also be glued in place.

FIG. 26Cillustrates the use of securing holes625to maintain the cylindrical shape of the planar formed, cylindrical MEMS film110. The MEMS film110includes a hole625at each of the corners of the MEMS film110. In some implementations, the MEMS film110can also include addition holes625along each long edge of the MEMS film110. As illustrated inFIG. 26D, when the MEMS film110is formed into a cylinder, two holes625are aligned with one another. A wire627can be run through each of the holes625to secure the seam and maintain the cylindrical shape of the planar formed, cylindrical MEMS film110. The wire627can be a metal or polymer wire, a staple, or a clip.

FIG. 26Eillustrates the distal end of a planar formed, cylindrical MEMS film110. The MEMS film110can include an under hang634that is positioned under the opposite edge632of the MEMS film110. The under hang634can provide a platform for applying an adhesive. The under hang634and the opposite edge632can be mechanically pressed together to form a seal at the seam of the planar formed, cylindrical MEMS film110. In some implementations, the under hang634can extend into the lumen defined by the planar formed, cylindrical MEMS Film110. In these implementations, when the lumen is backfilled with epoxy, the under hang634can be trapped within the epoxy, preventing the unravelling of the planar formed, cylindrical MEMS Film110. In some implementations, as illustrated inFIG. 26F, the under hang embodiment can include a plurality of holes625. As in the above, illustrated example, the two edges of the MEMS film110can be bound together by a wire627that passes through each of the holes625.

FIGS. 26G and 26Hillustrate an over molding method for maintaining the cylindrical shape of the planar formed, cylindrical MEMS film110. Once formed into a cylindrical shape, an end cap can form a collar655over the distal end of the MEMS film110. The body150can form a collar655over the proximal end of the MEMS film110. As illustrated byFIG. 26H, the collar655of the end cap (and the collar655of the body150) overlaps the MEMS film110by a predetermined distance657. In some instances, the collar655may extend longitudinally over the seam111in order to enclose the gap formed by the edges of the MEMS film110along the length of the cylinder shape.

The stimulation lead100can include distal recording sites on the end cap of the stimulation lead100.FIG. 27Aillustrates an example MEMS film110with end cap electrodes. The stimulation lead100can include a plurality of end cap electrodes715coupled with the end cap725of the stimulation lead100. As illustrated inFIG. 27A, the stimulation lead100includes five end cap electrodes715disposed along four end tags710. The end cap electrodes715can be used to identify neural activity during the implantation of the stimulation lead100into a patient's brain. The end tags710can be coupled with the end cap to ensure that the end cap electrodes715remain in place during implantation.

FIG. 27Billustrates an end view of the stimulation lead100configured to include distal recording sites. As described above, the stimulation lead100may include five end cap electrodes715disposed on the surface of the end cap725. The stimulation lead100may include a central end cap electrode715and then a plurality of end cap electrodes715positioned slightly proximal to the central end cap electrode715. In some implementations, one of the end cap electrodes715positioned slightly proximal to the central end cap electrode715is pointed in each of the anterior, posterior, lateral, and medial directions.

FIG. 27Cillustrates the planar MEMS film110with end cap electrodes715. Four end tags710extend from the distal end of the MEMS film110. In some implementations, the MEMS film110may include more than four end tags710. For example, the MEMS film110may include between 5 and 12 end tags710. At least one end cap electrode715is disposed on each of the end tags710. In some implementations, one of the end tags710is longer and includes an additional end cap electrode715. The longer end tag710can extend to the apex of the end cap725, and the end cap electrode715at the end of the loner end tag710is the central end cap electrode715when applied to the end cap725.

A MEMS film can couple with an existing stimulation lead.FIG. 28Aillustrates a MEMS film730coupled to an existing stimulation lead, such as a Medtronic 3389 DBS Lead (Medtronic Inc., MN). The MEMS film730can be positioned between or around existing ring electrodes755. The MEMS film730can add additional electrodes120and end cap electrodes715to the existing stimulation lead. The addition of the MEMS film730can add the ability of recording or stimulating directionally to the existing stimulation lead.FIG. 28Billustrates the MEMS film730in a planar configuration. The MEMS film730includes four electrodes120disposed along a single arm742and one end cap electrode715. In some implementations, the MEMS film730includes multiple rows of electrodes120disposed across one or more arms742. Each of the arms742can be configured to fit between each of ring electrodes755.

The stimulation lead can have electrodes distributed longitudinally along the axis of the stimulation lead. The electrodes can be distributed longitudinally along the axis of the stimulation lead to enable for flexion between electrode locations. A flexible stimulation lead can be used in spinal cord or pelvic floor stimulation, for example.

FIG. 29Aillustrates the distal end of a stimulation lead760configured with electrodes distributed longitudinally along the axis of the stimulation lead760. The stimulation lead760includes a MEMS film770, which can enable flexion between electrode sites. The MEMS film770is connected to the lead wires160which are within the external tube765to which the MEMS film770is disposed.

FIGS. 29B-29Dillustrates enlarged views of the distal end of the stimulation lead760. The MEMS film770includes a plurality of electrodes120that wrap around the circumference of the external tube765. Each electrode120is coupled with a contact pad145through traces embedded in a respective ribbon cable125. A lead wire160is connected and bonded to each of the contact pads145through welding, bonding, or gluing to electrically coupled each of the electrodes120to the proximal end of the MEMS film770. All subsequent electrode sites775on MEMS film770are assembled in the same manner.FIG. 29CandFIG. 29Dprovide additional planar perspectives of the same distal end of the Neurostimulation lead760.

FIG. 29Eillustrates the MEMS film770in a planar configuration before being disposed on the external tube765. The MEMS film770includes a plurality of electrodes120disposed on tabs780. The tabs780are connected together by the ribbon cable125, which includes the contact pad145for at least one of the electrodes120.FIG. 29Fillustrates another configuration of the MEMS film770where more than one electrode120is disposed on each of the tabs780. The number of contact pads145is increased on each ribbon cable125to match the number of electrodes120disposed on each of the tabs780. In some implementations, between 2 and 12 electrodes can be disposed on each of the tabs780.

FIGS. 30A and 30Billustrate the stimulation lead760implanted near a patient's spinal column. The flexible nature of the stimulation lead760enables the stimulation lead760to be inserted between vertebrae815to be positioned near the spinal cord817.

In some implementations, the platinum electrodes are thickened. The platinum of the electrodes can be electro-galvanically thickened past its native thickness. For example, one method is to insert the distal end of the stimulation lead into an electro-galvanic bath and apply current to the contacts in order to initiate the growth of a platinum layer.FIG. 31illustrates the process of electro-galvanically thickening electrodes. A stimulation lead100is inserted into a bath842and a current is applied using a galvanic source845. In some implementations, one advantage of growing the thickened layer on the molded stimulation lead100, and not the planar stimulation lead100on its carrier wafer, is that the thickened layer may not be stressed when subsequently molded into the cylindrical shape. In these implementations, plasma deposition methods may be used to deposit additional platinum, or other materials such as iridium oxide, to thicknesses greater than the native thickness of the electrode.

FIG. 32Aillustrates a cross section of a stimulation lead100with no platinum growth, andFIG. 32Billustrates a cross section of a stimulation lead100with platinum growth.FIGS. 32A and 32Billustrate that each stimulation lead100include a first polyimide layer870, a first silicon based barrier layer872, a first metal layer878, a second silicon based barrier layer874, and a second polyimide layer876. As illustrated inFIG. 32B, a galvanically grown platinum layer880is deposited on regions where the metal seed layer878is exposed. The growth of a platinum layer880can be close to the superior surface of the second polyimide layer876(e.g., within a few microns), or the platinum layer880can provide a platinum thickness that is flush to the surface of the second polyimide layer876.

In some implementations, the traces, or other metal components of the stimulation lead100are disposed in a second metal layer below the metal layer that includes the electrodes120. Traces in a second metal layer enable the traces to connect to the contact pads and electrode as places other than the edge of the contact pad or electrode. This can enable a more uniform current density for the contact pads and electrodes. Also, each connection to the electrode can make contact with the same electrical potential—improving the uniformness of the current density.FIGS. 33A-33Nillustrate the method of manufacturing a MEMS film with a second encapsulated metal layer.

FIG. 33Aillustrates the first step of the process where a carrier substrate901is provided. A first layer902including at least two sub-layers can be applied to a surface of the substrate901. One of the sub-layers of the first layer902can be a sacrificial layer which is later removed in a subsequent electrochemical etch step to separate the finished MEMS film from the carrier substrate901. The sacrificial sub-layer can be preceded by another sub-layer, referred to as an underlayer, which can serve to form the electrochemical cell to etch the sacrificial layer.

Referring toFIG. 33B, the next step in the fabrication process can include depositing a first polymeric layer905upon the sacrificial layer902. The first polymeric layer can be between about 2 μm and about 15 μm thick.

Referring toFIG. 33C, a silicon based barrier layer910can be deposited. The silicon based barrier layer910can be between about 500 nm and about 5 μm thick, which can enable the silicon based barrier layer910to be flexible enough to bend during subsequent assembly techniques.

FIG. 33Dillustrates a first metal layer915deposited over the entire wafer on the surface of the silicon based barrier layer910. The structures within the first metal layer915, such as traces and contacts, can be structured using photolithographic techniques. The first metal layer915can be generally incorporated by depositing several metal layers, such as Titanium, Platinum, and again Titanium, to form a tri-layer which can improve adhesion. The tri-layer can be deposited with thicknesses of 50 nm, 300 nm, and 50 nm respectively.

Referring toFIG. 33E, a second silicon based barrier layer920can be deposited. The second silicon based barrier layer920can be deposited using the same techniques as the first silicon based barrier layer910and can be generally of a similar thickness. In some implementations, the second silicon based barrier layer920is slightly thinner than the first silicon based barrier layer910. As illustrated byFIG. 33E, the second silicon based barrier layer920and the first silicon based barrier layer910completely surround the metal layer915rendering it electrically isolated.

FIG. 33Fillustrates that a local etching of the second silicon based barrier layer920can be performed to create creates a silicon based barrier layer via (or through hole)917that exposes the first metal layer915.

Referring toFIG. 33G, a second metal layer925is deposited on the surface of the second silicon based barrier layer. The second metal layer925includes similar metal to the first metal layer915, and can be about the same or similar thickness to the first metal layer915. The second metal layer925comes into electrical contact with the first metal layer915through the silicon based barrier layer via917.

FIG. 33Hillustrates the depositing of a third silicon based barrier layer927. The third silicon based barrier layer927can be deposited in a method similar to the first silicon based barrier layer910, and can be of the same or similar thickness as the first silicon based barrier layer910.

FIG. 33Hillustrates the etching of the layers. The silicon based barrier layers can be etched using a plasma etch. An example of an etching process includes a reactive ion etching using a tetrafluoromethane gas, (CF4). A photoresist layer can be used to define which areas are etched. Openings in the third silicon based barrier layer927can be created in order to expose the second or first metal layers.

FIG. 33Iillustrates a second polymer layer930deposited on the substrate. The second polymer layer930can be the same or a different polymer from the first polymer layer905, and the second polymer layer930can be the same or a different thickness. In some implementations, the second polymer layer930is polyimide and is between about 2 μm and about 15 μm thick.

FIG. 33Jillustrates the result of an oxygen plasma etching of the first and second polyimide layers905and930, respectively. The etching process creates openings932in the second polyimide layer930to expose the third silicon based barrier layer927.

FIG. 33Killustrates the etching of the third silicon based barrier layer925to create metal openings933to expose the second metal layer925. In some implementations, the openings933can also descend to regions of the first metal layer915. The openings933can define the regions of the electrodes120that come into contact with the neural tissue or for define contact pads145.

FIG. 33Lillustrates the deposition of a photoresist layer935over the substrate. The photoresist layer935can maintain the exposed metal opening933. The opening937in the photoresist layer935can create a region for a gold layer to grow.

FIG. 33Millustrates the galvanic growth of a thick gold layer940in the opening937. The gold layer940can be grown by connecting all metal traces in the wafer to a perimetric metal band that allows electrical connection between the edge of the wafer and the metal opening937. In some implementations, the gold growth layer940of about 5 μm to about 20 μm thick.

FIG. 33Nillustrates that the photoresist layer935has been removed to expose the electrode opening943. The MEMS film is now removed from the wafer901by the removal of the sacrificial layer902using electrochemically etching.

FIGS. 34A-34Eillustrate an example of a MEMS film with two metal layers.FIG. 34Aillustrates a first metal layer915deposited over a first polymeric layer and silicon based barrier layer953. The placement of the traces in a different metal layer than the electrodes can improve the potential distribution on the surface of electrodes by dispatching traces from a central point of equivalent potential. For example, a potential or current can be applied to the pad959, the current travels down the trace315toward an equipotential cross955at a given potential. From the equipotential cross955, the current travels to each of the four extremities954at similar potentials to one another.

FIG. 34Billustrates the application of the second silicon based barrier layer920. The second silicon based barrier layer920includes a number of vias917that are configured to align with the ends of the extremities954and the pads959.

FIG. 34Cillustrates the application of a second metal layer to the silicon based barrier layer920. The second metal layer includes the electrodes120and the contact pads145. Each of the electrodes120includes a plurality of contact points977that make contact with the first metal layer915through the vias917. In other implementations, the electrodes120do not include contact points977, and the electrodes120make contact with the first metal layer915through vias917that are positioned within the body of the electrodes120.

FIG. 34Dillustrates the application of the third silicon based barrier layer and the second polyimide layer930. The third silicon based barrier layer and the second polyimide layer930include through holes982that define the electrodes120and the contact pads145.

FIG. 34Eillustrates the complete MEMS film. The second polyimide layer930defines the electrodes120and the contact pads145. In some implementations, the use of a second metal layer improve the permissible electrode sizes, orientation, and quantity because moving the traces to a separate layer frees surface area within the electrode metal layer, enabling greater freedom to move and arrange electrodes.

FIG. 35Aillustrates an example proximal end180of the stimulation lead100. In some implementations, the proximal end contacts190can be implemented as a MEMS film. Implementing the proximal end contacts190as a MEMS film can decrease the diameter of the proximal end180and improve the manufacturability of the proximal end contacts190. The proximal end180can be configured to be compatible with existing extension cables such as the Medtronic 37081 cable. The extension cables can couple the stimulation lead100with the implantable stimulator122, which can be, for example, a Medtronic Activa PC. In some implementations, the proximal end180can be configured to be compatible with extension cables that have a smaller pitch between the contacts than compared to the Medtronic 37081. The MEMS film1910of the proximal end180can be manufactured using the above described MEMS film manufacturing methods. For example, the proximal MEMS film1910can be formed as a planar film that is premolded into a cylindrical shape and backfilled with a polymer or epoxy.FIG. 35Billustrates the proximal end180from a different angle.

As illustrate inFIGS. 35A and 35B, the MEMS film1910includes a distal portion1915, which incorporates a plurality of contact pads145that electrically couple the MEMS film1910to the lead wires160, which run through the lead body150toward the distal end of the stimulation lead100. A proximal portion1915of the MEMS film1910, can include a plurality of proximal contacts190. The proximal contacts190can be in electrical communication with one or more of the contact pads145on the distal portion1915of the MEMS film1910. In some implementations, the contact pads145are ring electrodes. The proximal portion1911and distal portion1915of the MEMS film1910can be coupled with one another by one or more interconnects1925. Traces electrically coupling the contacts190of the proximal portion1911with the contacts145of the distal portion1915can be housed within the interconnects1925. In some implementations, redundant traces are included within the at least one of the interconnects1925. Redundant traces can help guard against a device failure should one interconnect1925break. A lumen1950is defined through the proximal end180of the stimulation lead100. The lumen1950can be configured to permit the passage of an implantation stylet, which can provide stiffness to the stimulation lead10during implantation.

In some implementations, the proximal end180can include a stiff region distal to the proximal end contacts190. The stiff region can be between about 1 cm and about 5 cm or between about 1.5 cm and about 2.5 cm long, e.g., substantially 2 cm. The stiff region can help a neurosurgeon push the proximal end180into the female end of an extension cable.

In some implementations, the proximal contacts190can be thickened using the above described electro-galvanic deposition methods. Thickening the proximal contacts190can be advantageous for repeated coupling of an extension cable to the proximal end180because the thickened metal layer can improve the proximal contacts' resistances to scratches, making the proximal contacts190more reliable and durable. In some implementations, the MEMS film techniques described herein can also be used to implement the extension cable.

In some implementations, a MEMS film can be disposed within an encapsulating tube that is coupled with the body150.FIG. 36illustrates an example MEMS film110disposed within an encapsulating tube. The MEMS film110can include a plurality of bond pads1961onto which contacts can be coupled. In some implementations, the bond pads1961are metal surfaces similar to the electrodes120. In some implementations, the internal MEMS film110can have a smaller diameter when formed into a cylinder than compared to, for example, the cylinder formed from the MEMS film110illustrated inFIG. 3Awhere the MEMS film110is not disposed in an encapsulating tube. The diameter of the tube encapsulated MEMS film100can be between about 0.5 mm and about 1.5 mm. The internal MEMS film110can also include a plurality of contact pads145.

FIGS. 37A and 37Billustrate two views of a contact1970. In some implementations, the contact1970can be relatively thicker when compared to an electrode120. The contact1970can be formed by longitudinally splitting a platinum cylinder with a lumen into a plurality of sections. In some implementations, the platinum cylinder can have an internal diameter between about 0.5 mm and about 1.5 mm and an external diameter between about 0.7 mm and 1.7 mm. In some implementations, a wall of the platinum cylinder is about 0.2 mm thick. The platinum cylinder can be divided into contracts1970by laser micromachining the cylinder. In some implementations, the contacts1970include platinum, titanium, or other conductive materials with an iridium oxide coating.

FIGS. 38A and 38Billustrate the coupling of the contacts1970with the MEMS film1955. As illustrated, a contact1970is coupled with each of the bond pads1961. In some implementations, the contacts1970are coupled with the bond pads1961by, for example, laser welding, thermocompression bonding, ultrasonic bonding, conductive gluing, wire bonding, or brazing.FIG. 38Billustrates a contact1970coupled to each of the bonding pads1961. In some implementations, each of the contacts1970is much thicker than the MEMS film110. Once coupled with the MEMS film110, the contacts1970are electrically coupled to the contacts145through traces embedded within the MEMS film110. In some implementations, the contacts1970are coupled with the MEMS film110after the MEMS film110is formed into a cylinder and made rigid by, for example, backfilling the defined lumen with a polymer. In some implementations, the bonding pads1961are substantially the same size as the portion of the contacts1970that is coupled with the MEMS film110. In other implementations, the bonding pads1961can be larger or smaller than the portion of the contacts1970that are coupled with the MEMS film10. In some implementations, the contact bonding pads1961can be cylindrical contacts, or include different sizes and geometries, with some sizes dedicated to simulation, while others are dedicated to recording.

FIG. 38Cillustrates the coupling of lead wires160to the MEMS film110with contacts1970. The lead wires160can be coiled as they run the length of the body150. A lead wire160can be coupled with each of the contact pads145.FIG. 38Dillustrates an example stimulation lead with a MEMS film disposed within an encapsulating tube. The encapsulating tube1990encapsulates the MEMS film110, including the contact pads145and the end of the lead wires160. When encapsulated in the tube1990, the contacts1970are exposed and can be flush with the outer surface of the tube1990. The tube1990can be flush with the body150. In some implementations, the tube1990is formed by overmolding the MEMS film110with an epoxy. The overmolding can secure the contracts1970to the MEMS film110while keeping the surface of the contacts1970exposed in order to conduct electrical current to the target site. The overmolding can also electrically isolate the contacts145and lead wires160.

Various implementations of the microelectrode device have been described herein. These embodiments are giving by way of example and not to limit the scope of the present disclosure. The various features of the embodiments that have been described may be combined in various ways to produce numerous additional embodiments. Moreover, while various materials, dimensions, shapes, implantation locations, etc. have been described for use with disclosed embodiments, others besides those disclosed may be utilized without exceeding the scope of the disclosure.

Devices described herein as either acute or chronic may be used acutely or chronically. They may be implanted for such periods, such as during a surgery, and then removed. They may be implanted for extended periods, or indefinitely. Any devices described herein as being chronic may also be used acutely.

The present disclosure is not to be limited in terms of the particular embodiments described in this application, which are intended as illustrations of various aspects. Modifications and variations can be made without departing from its spirit and scope of this disclosure. Functionally equivalent methods and apparatuses may exist within the scope of this disclosure. Such modifications and variations are intended to fall within the scope of the appended claims. The subject matter of the present disclosure includes the full scope of equivalents to which it is entitled. This disclosure is not limited to particular methods, reagents, compounds compositions or biological systems, which can vary. The terminology used herein is for the purpose of describing particular embodiments, and is not intended to be limiting.

With respect to the use of substantially any plural or singular terms herein, the plural can include the singular or the singular can include the plural as is appropriate to the context or application.

In general, terms used herein, and especially in the appended claims (e.g., bodies of the appended claims) are generally intended as “open” terms (e.g., the term “including” should be interpreted as “including but not limited to,” the term “having” should be interpreted as “having at least,” the term “includes” should be interpreted as “includes but is not limited to,” etc.). Claims directed toward the described subject matter may contain usage of the introductory phrases “at least one” and “one or more” to introduce claim recitations. However, the use of such phrases should not be construed to imply that the introduction of a claim recitation by the indefinite articles “a” or “an” limits any particular claim containing such introduced claim recitation to embodiments containing only one such recitation, even when the same claim includes the introductory phrases “one or more” or “at least one” and indefinite articles such as “a” or “an” (e.g., “a” and/or “an” should be interpreted to mean “at least one” or “one or more”); the same holds true for the use of definite articles used to introduce claim recitations. In addition, even if a specific number of an introduced claim recitation is explicitly recited, such recitation can mean at least the recited number (e.g., the bare recitation of “two recitations,” without other modifiers, means at least two recitations, or two or more recitations). Furthermore, in those instances where a convention analogous to “at least one of A, B, and C, etc.” is used, in general such a construction would include but not be limited to systems that have A alone, B alone, C alone, A and B together, A and C together, B and C together, and/or A, B, and C together, etc.). In those instances where a convention analogous to “at least one of A, B, or C, etc.” is used, in general such a construction would include but not be limited to systems that have A alone, B alone, C alone, A and B together, A and C together, B and C together, and/or A, B, and C together, etc.). Any disjunctive word or phrase presenting two or more alternative terms, whether in the description, claims, or drawings, can contemplate the possibilities of including one of the terms, either of the terms, or both terms. For example, the phrase “A or B” includes the possibilities of “A” or “B” or “A and B.”

In addition, where features or aspects of the disclosure are described in terms of Markush groups, the disclosure is also described in terms of any individual member or subgroup of members of the Markush group.

Any ranges disclosed herein also encompass any and all possible subranges and combinations of subranges thereof. Any listed range can be easily recognized as sufficiently describing and enabling the same range being broken down into at least equal halves, thirds, quarters, fifths, tenths, etc. As a non-limiting example, each range discussed herein can be readily broken down into a lower third, middle third and upper third, etc. Language such as “up to,” “at least,” “greater than,” “less than,” and the like include the number recited and refer to ranges which can be subsequently broken down into subranges as discussed above. Finally, a range includes each individual member.

One or more or any part thereof of the techniques described herein can be implemented in computer hardware or software, or a combination of both. The methods can be implemented in computer programs using standard programming techniques following the method and figures described herein. Program code is applied to input data to perform the functions described herein and generate output information. The output information is applied to one or more output devices such as a display monitor. Each program may be implemented in a high level procedural or object oriented programming language to communicate with a computer system. However, the programs can be implemented in assembly or machine language, if desired. In any case, the language can be a compiled or interpreted language. Moreover, the program can run on dedicated integrated circuits preprogrammed for that purpose.

Each such computer program can be stored on a storage medium or device (e.g., ROM or magnetic diskette) readable by a general or special purpose programmable computer, for configuring and operating the computer when the storage media or device is read by the computer to perform the procedures described herein. The computer program can also reside in cache or main memory during program execution. The analysis, preprocessing, and other methods described herein can also be implemented as a computer-readable storage medium, configured with a computer program, where the storage medium so configured causes a computer to operate in a specific and predefined manner to perform the functions described herein. In some embodiments, the computer readable media is tangible and substantially non-transitory in nature, e.g., such that the recorded information is recorded in a form other than solely as a propagating signal.

In some embodiments, a program product may include a signal bearing medium. The signal bearing medium may include one or more instructions that, when executed by, for example, a processor, may provide the functionality described above. In some implementations, signal bearing medium may encompass a computer-readable medium, such as, but not limited to, a hard disk drive, a Compact Disc (CD), a Digital Video Disk (DVD), a digital tape, memory, etc. In some implementations, the signal bearing medium may encompass a recordable medium, such as, but not limited to, memory, read/write (R/W) CDs, R/W DVDs, etc. In some implementations, signal bearing medium may encompass a communications medium such as, but not limited to, a digital or an analog communication medium (e.g., a fiber optic cable, a waveguide, a wired communications link, a wireless communication link, etc.). Thus, for example, the program product may be conveyed by an RF signal bearing medium, where the signal bearing medium is conveyed by a wireless communications medium (e.g., a wireless communications medium conforming with the IEEE 802.11 standard).

Any of the signals and signal processing techniques may be digital or analog in nature, or combinations thereof.

While certain embodiments of this disclosure have been particularly shown and described with references to preferred embodiments thereof, various changes in form and details may be made therein without departing from the scope of the disclosure.