The present invention is related to a microelectrode array for a brain-machine interface and neural recording and stimulation, and a method of making the same.
Microelectrodes may be implanted into a brain in order to monitor neurological signals and/or deliver therapy to the patient's brain. Deep brain electrodes may be used to investigate and treat a variety of neurological conditions. Electrodes intended to penetrate into neural tissue may have a single recording or stimulating site or multiple sites. As used herein, these electrodes are called single-shank probes, or simply probes. An array can include a plurality of probes, each probe of the array having a single recording or stimulating site or multiple recording or stimulating sites.
Differences in probe packaging, interconnections, and surgical methods make it difficult to directly compare electrode performance in experimental studies, making it difficult to improve the brain-machine interface. For example, the ability of probes implanted chronically in the brain to record resolvable neuronal activities is often reduced or completely lost over time. However, the efficacy and rate of degradation of different types of probes may be difficult to compare objectively when they are not contained in a single array.
Furthermore, it may also be beneficial to combine different types of probes into a single array so that the benefits of several different types of probes may be realized in a single array. However, it is difficult to combine multiple types of probes into a single array. This is due to the small size of the probes and the difficulty in precisely aligning the small probes and in keeping lead wires safe during the assembly. In addition, bonding of lead wires to multisite silicon-based probes is quite different from microwire-based electrodes, or multi-electrode modules supplied by commercial vendors.
Accordingly, there is a need for a method to combine multiple probes and multiple types of probes into a single hybrid microelectrode array.
Aspects of the present invention are directed to a multielectrode array that includes multiple probes or array sub-assemblies, and a method of making the same.
According to one embodiment, a method of forming a multielectrode array includes forming an array bottom plate, the array bottom plate having a first opening, a second opening, a first alignment opening, and a second alignment opening. The method further includes forming an alignment plate, the alignment plate having a third opening and a fourth opening corresponding to the first opening and the second opening, respectively, a third alignment opening and a fourth alignment opening corresponding to the first alignment opening and the second alignment opening, respectively. An anti-wicking plate may be applied to the alignment plate. A first alignment member may be placed through the first alignment opening and the third alignment opening and a second alignment member may be placed through the second alignment opening and the fourth alignment opening to align the alignment plate and the array bottom plate. The array bottom plate may be temporarily affixed to the anti-wicking plate. A first probe or array sub-assembly may be inserted into the first opening and the third opening and a second probe or array sub-assembly may be inserted into the second opening and the fourth opening so that at least a portion of each of the first probe or array sub-assembly and the second probe or array sub-assembly extends above the array bottom plate. Each of the first probe or array sub-assembly and the second probe or array sub-assembly may be fixed to the array bottom plate. Then, the array bottom plate with the first probe or array sub-assembly and the second probe or array sub-assembly may be removed from the alignment plate to form a multielectrode array.
The array bottom plate may be adhered to the anti-wicking plate using a temporary adhesive.
The applying the anti-wicking plate to the alignment plate may include forming the anti-wicking plate and fixing the anti-wicking plate to the alignment plate using a permanent adhesive. Or, the applying the anti-wicking plate to the alignment plate may include integrally forming the anti-wicking plate and the alignment plate using 3-D printing.
The method may further include applying an edge strip to a surface of the array bottom plate opposite the anti-wicking plate. The applying the edge strip to a surface of the array bottom plate may include forming the edge strip and fixing the edge strip to the array bottom plate using a permanent adhesive. A permanent adhesive may be applied on top of the array bottom plate up to the edge strip and then cured to secure the first probe or array sub-assembly and the second probe or array sub-assembly in place. The adhesive may partially cured prior to being applied on top of the array bottom plate. The edge strip may be affixed to the array bottom plate using a first permanent, biocompatible adhesive, and a second permanent, biocompatible adhesive may be applied on the array bottom plate up to the edge strip and then cured to form an adhesive cap.
The alignment member may be a wire.
The first probe or array sub-assembly may be different from the second probe or array sub-assembly. The first probe or array sub-assembly may have a different shape than the second probe or array sub-assembly.
The forming the alignment plate may include forming two alignment plates each having the third opening, the fourth opening, the third alignment opening, and the fourth alignment opening corresponding to the first opening, the second opening, the first alignment opening, and the second alignment opening, respectively, wherein a first alignment tube is located in the first opening and the third opening between the two alignment plates, and a second alignment tube is located in the second opening and the fourth opening between the two alignment plates.
The array bottom plate, the alignment plate, and the anti-wicking plate may each include a material independently selected from silicon, a ceramic, a metal, an alloy, and a polymer. In some embodiments, each of the array bottom plate, the alignment plate, and the anti-wicking plate may be made of silicon.
The forming the array bottom plate may include using photolithography and micromachining to form the array bottom plate and the forming the alignment plate may include using photolithography and micromachining to form the array bottom plate.
According to one embodiment, a multielectrode array may include an array bottom plate, a first probe or array sub-assembly and a second probe or array sub-assembly extending below the array bottom plate, the first probe or array sub-assembly and the second probe or array sub-assembly being different, and an adhesive cap above the array bottom plate, the adhesive cap fixing the first probe or array sub-assembly and the second probe or array sub-assembly to the array bottom plate.
The first probe or array sub-assembly may have a different shape than the second probe or array sub-assembly.
The array bottom plate may include a first opening through which the first probe or array sub-assembly extends and a second opening through which the second probe or array sub-assembly extends through the second opening.
The array bottom plate may include a material selected from silicon, a ceramic, a metal, an alloy, and a polymer.
According to some embodiments, a method of forming a multielectrode array including at least two different electrodes includes forming an apparatus for assembling an array, assembling an array, and removing the array from the assembly.
The apparatus 100 is made specific to a specific array configuration. Thus, the size and number of openings in the various components may be adjusted according to the desired array. For example, as shown in
In some embodiments, the top alignment plate may be fixed to the top of a support 60, as shown in
The apparatus may include an anti-wicking plate as shown in
Last, a cover plate 50 (or top plate) may be attached to the top of the edge strip 40 as shown in
Once the components (e.g., alignment plate, anti-wicking spacer, bottom plate, edge strip, top plate) of the apparatus are fabricated, they may be assembled. Those of ordinary skill in the art would understand that the apparatus used to assemble the hybrid array may be fabricated in any suitable order. First, the alignment plate 10 may be fixed to the support 60. Optionally, two alignment plates and/or the stainless steel tubes 11 may be used and assembled, as discussed above. That is, optionally, one alignment plate may be fixed to the top of the support and one alignment plate may be fixed to the bottom of the support, and stainless steel tubes may be inserted into the openings of each alignment plate and fixed thereto. Then, the anti-wicking plate 20 may be permanently fixed to the top surface of the alignment plate 10 using an epoxy, polymer, or other adhesive, and for example, an Epotek epoxy may be used. The alignment plate 10 and the support may then be placed in an oven to allow the adhesive to cure. For example, they may be placed in a low temperature oven for about 15 minutes. Then, the anti-wicking plate 20 may be permanently fixed to the alignment plate 10 using an epoxy, polymer, or other adhesive, and for example, an Epotek epoxy may be used. The anti-wicking plate 20, the alignment plate 10, and the support 60 may be placed in an oven to allow the adhesive to cure, for example, they may be placed in a low temperature oven for about 15 minutes. In fixing the anti-wicking plate 20 to the alignment plate 10, it is important that the edge is aligned, so that the openings in the anti-wicking plate 20 are registered (e.g., lined up) with the openings of the alignment plate. Alternatively, the anti-wicking plate 20 may be fixed to the alignment plate 10 prior to fixing the alignment plate 10 to the support 60.
The edge strip 40 may be attached to the bottom plate 30. The bottom plate 30 may be aligned along two walls (for example, pushed up against two walls of a structure), and then the edge strip 40 may be placed on the bottom plate 30, with a layer of permanent adhesive therebetween. The permanent adhesive may be a polymer, epoxy, or other permanent adhesive, and for example, could be a biocompatible epoxy. The adhesive should be biocompatible because the edge strip and bottom plate are a permanent part of the hybrid array. The bottom plate 30 and the edge strip 40 may then be placed in an oven to allow the adhesive to cure. For example, they may be placed in a low temperature oven for about 15 minutes to cure. Alternatively, the edge strip 40 may be fixed to the bottom plate after the probes and/or arrays are fixed to the bottom plate.
Next, the bottom plate 30 may be attached to the top surface of the anti-wicking plate 20. First, an alignment member (e.g., a thin wire) that fits inside the alignment openings 16 and 36 is placed in one set of the alignment openings. Then, the bottom plate 30 is moved (e.g., rotated around the inserted thin wire) until another thin wire may be inserted into the other alignment opening. 16 and 36. Once aligned, and once the bottom plate 30 is seated firmly on the anti-wicking plate 20, a temporary adhesive may be applied to the junction between the bottom plate 30 and the anti-wicking plate 20. In some embodiments, the temporary adhesive may only be applied along the back surface of the structures (i.e., the widest part of the anti-wicking plate). The temporary adhesive may be a water-soluble adhesive such as polyvinyl alcohol or any other suitable temporary adhesive. The temporary adhesive may be a type such that when the assembly of the hybrid array is completed, a solvent, e.g., water, may be applied to the temporary adhesive to release the bond between the bottom plate 30 and the anti-wicking plate 20 without harming the hybrid array.
Then, the probes and/or array sub-assemblies may then be inserted into the apparatus 100. In view of the fragile nature of the probes, care must be taken when inserting probes into the apparatus. As such, in some embodiments, a micromanipulator or other suitable device for intricate manipulation may be used. However, the probes may be inserted by any suitable method. Each probe may then be inserted into a probe opening 32 (and accordingly, probe opening 12) using the micromanipulator. The opening 12 in the alignment plate aligns the axis of the probes. The amount of extension of each probe below the array bottom plate may be controlled by a protuberance on the probe that is greater in size than the diameter of the opening 32 (e.g., in the case of a NeuroNexus probe, its bonding zone or area which contains bond pads). The array sub-assembly including a plurality of probes (e.g., a Blackrock 4×2) is seated in the array sub-assembly opening 34, and should be seated so that the electrodes of the array sub-assembly are approximately an equal distance from the front and back and left and right edges of the opening 36. Once all probes and array sub-assemblies have been inserted, and they have been seated against the bottom plate 30, a very small amount of an adhesive is applied where each probe or array contacts the bottom plate 30. For example, a fast-curing epoxy or other permanent adhesive that is biocompatible may be used. Alternatively, the probes may be fixed one at a time, as they are inserted, or, once a group of probes (e.g., a row) is inserted, they may be fixed. In some embodiments, an electrode or array is not inserted into one or more openings. That is, the bottom plate and/or alignment plate may include unused openings.
The lead wires may be any suitable lead wires, such as those commonly used with penetratable electrode probes. For example, gold lead wires may be used. In addition, gold lead wires coated with Parylene-C may be used.
Then the lead wires are directed out of the structure and attached to a connector. In some embodiments, when the top plate is going to be used, the lead wires are directed out the open side of the structure (where the edge strip is not present). In other embodiments, when a top plate is not going to be used, the lead wires may be extended vertically out of the structure (i.e., in a direction generally perpendicular to the surface of the bottom plate). Then, the secured probes may be further secured by applying partly cured epoxy or other adhesive along the seated and fixed row. The epoxy or other adhesive is partly cured to increase its viscosity and prevent the adhesive from seeping through the openings or spreading along the array bottom. Alternatively, once a single probe or a group of probes (e.g., a row) is inserted, they may be further secured by applying an epoxy or other adhesive that is partly cured. The direction of the lead wire can restrict or enable the hybrid array's use for a specific purpose. For example, if the lead wires exit through the area where the top of the hybrid array, the hybrid array can be used with deep brain structures. On the other hand, if the leads exit through the side of the hybrid array, the hybrid array can be used for the top of the brain or the cerebral cortex.
Once all probes and/or array sub-assemblies have been seated and fixed to the bottom plate 30, the cavity is filled with a polymer, epoxy, or other adhesive. For example, Epotek 301 may be used. The adhesive may be partially cured when it is applied to the cavity so that it does not flow beyond the cavity. For example, when Epotek 301 is used, it may be allowed to partly polymerize for about 2.5 hours at room temperature. The partial curing of the Epotek 301 may be tested by lifting a drop with 0.001″ wire; when it requires about 3 seconds for the string to retract into the drop on the end of the wire, an appropriate amount of curing has occurred for use. Slowly, the cavity may be filled with adhesive. The adhesive should not extend above the top of the edge strip 40. This forms the body of the hybrid array.
The cover plate 50 may be fixed to the top of the edge strip. The cover plate may also be in contact with the adhesive filling the cavity. When the adhesive is fully cured, a lifting surface controlled by a micromanipulator is joined to the upper plate using a water-soluble adhesive. Water or another solvent is applied to the junction between the array bottom plate and the anti-wicking plate to break the adhesive bond and separate the bottom plate and the anti-wicking plate, and the array is lifted from the anti-wicking plate using the micromanipulator. The micromanipulator may then be used to lower the structure into a solvent to release the array from the micromanipulator. In some embodiments, no cover plate is used.
Any suitable penetratable electrode probes and/or array sub-assemblies may be used. In some embodiments, the probes may be made of silicon, for example, boron-doped silicon devices from NeuroNexus Inc. or Utah Intracortical Arrays from Blackrock Microsystems, Inc., thick silicon probes shaped by deep reactive ion etching, or the like; carbon; metal, for example, iridium, platinum, gold, alloys such as a platinum-iridium alloy, or the like; diamond; compound semiconductor materials, for example GaAs, InP, or the like; polymers for example, polyimide, Parylene, silicone/PDMS, or the like; or biodegradable polymers, for example, poly-lactic-glycolic acid or the like. The type of probes may be single-site electrodes, for example, metal-based microwires or the like; multi-site electrodes, for example, silicon devices, polymer devices, or the like; or metal microwires with open site(s) along the length of the wire; or the like. However, any suitable probe materials and any suitable types of probes may be used.
As used herein, “polymer, epoxy, or other adhesive” generally refers to any material that adheres or bonds two things together. The polymer, epoxy, or other adhesive may include a filler. As used herein, a temporary adhesive refers to an adhesive, such as a polymer or an epoxy, that is dissolved by a common solvent that does not harm the array. For example, an adhesive such as polyvinyl alcohol that dissolves with water is a temporary adhesive. As used herein, a permanent adhesive refers to an adhesive, such as a polymer or epoxy, commonly known as a permanent adhesive. For example, a permanent adhesive may be an adhesive that is not dissolved by a solvent that does not harm the array or is only dissolved by an uncommon solvent.
Using this method, a hybrid multi-electrode array may be formed as shown in
The preceding description has been presented with reference to certain exemplary embodiments of the invention. Workers skilled in the art and technology to which this invention pertains will appreciate that alterations and changes to the described embodiments may be practiced without meaningfully departing from the spirit and scope of this invention, as defined in the appended claims. It is further understood that the drawings are not necessarily to scale.
Accordingly, the foregoing description should not be read as pertaining only to the precise structures and methods described and illustrated in the accompanying drawings, but rather should be read consistent with and as support to the following claims which are to have their fullest and fairest scope.
This application claims priority to and the benefit of U.S. Provisional Application No. 61/569,721, filed Dec. 12, 2011, the entire contents of which are incorporated herein by reference.
Number | Date | Country | |
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61569721 | Dec 2011 | US |