Application of irreversible electroporation (IRE) ablation using a catheter with an electrode array

Abstract

To provide a method for applying irreversible electroporation.SOLUTION: The method comprises inserting an array of multiple electrodes, fitted at a distal end of a catheter, into a cavity in an organ of a patient. The array is brought into contact with the inner surface of the cavity. Input from a user is received that specifies one or more tissue segments on the inner surface to be ablated. In response to the input, one or more electrode pairs in the array are selected using a processor, and the selected electrode pairs, when driven with an irreversible electroporation (IRE) signal, ablate the specified tissue segment. The designated tissue segment is ablated by applying an IRE signal to the pair of electrodes.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates generally to medical probes, and more particularly to multi-electrode catheters. [Background technology]

[0002] Various medical probes having multiple electrodes disposed on their distal end have been proposed in the patent literature. For example, U.S. Patent No. 9,867,978 describes an array of electrodes on a flexible scaffold that can be folded into an axially aligned shape suitable for deployment through a narrow cylindrical channel. The electrode array can be placed within the ventricular system of the brain, forming a minimally invasive platform for precisely localizing electrical activity in space and time within the brain and electrically stimulating brain tissue with precision, diagnosing diseases caused by abnormal electrical activity within the brain, and restoring function.

[0003] As another example, U.S. Patent Application Publication No. 2005 / 0065509 describes a device for ablating the pleura with electrical energy, the device including an array of electrodes disposed within a cannula lumen and deployable from the distal end of the cannula. When deployed from the cannula, the electrodes may extend in a direction substantially perpendicular to the longitudinal axis of the cannula and define a plane. During use, the cannula may be inserted into the thoracic cavity until the distal ends are adjacent the pleura. The electrodes are advanced from the cannula so that their distal portions are spaced apart and lie in a plane. The distal portions are positioned in contact with the pleura, and electrical energy is delivered from the electrodes to ablate the pleura. Summary of the Invention [Means for solving the problem]

[0004] One embodiment of the present invention, described below, provides a method including inserting an array of multiple electrodes attached to the distal end of a catheter into a cavity in a patient's organ. The array is brought into contact with an inner surface of the cavity. Input is received from a user specifying one or more tissue segments on the inner surface to be ablated. In response to the input, a processor is used to select one or more electrode pairs in the array, which, when activated with an irreversible electroporation (IRE) signal, ablate the specified tissue segment. The specified tissue segment is ablated by applying the IRE signal to the electrode pair.

[0005] In some embodiments, receiving the input includes allowing a user to visualize a position of the array relative to the cavity, and receiving the input in response to the visualized position.

[0006] In some embodiments, receiving the input includes indicating to a user a partial subset of electrodes in the array that are in contact with the inner surface of the cavity, and receiving the input in response to that subset.

[0007] In other embodiments, receiving the input includes indicating to a user one or more areas on the inner surface of the cavity that are in contact with the array, and receiving the input in response to the one or more areas.

[0008] In one embodiment, contacting the array with the interior surface of the cavity includes measuring impedance using a plurality of electrodes.

[0009] In another embodiment, contacting the array with the inner surface of the cavity comprises measuring a shape of the array, hi yet another embodiment, contacting the array with the inner surface of the cavity comprises measuring a contact force between the array and the surface.

[0010] In some embodiments, the array is a planar array.

[0011] According to another embodiment of the present invention, there is further provided a system including a processor and an IRE generator. The processor is attached to the distal end of a catheter and connected to an array of multiple electrodes that are inserted into a cavity in a patient's organ and brought into contact with the inner surface of the cavity. The processor is also configured to (a) receive input from a user designating one or more tissue segments on the inner surface of the cavity to be ablated, and (b) select one or more pairs of electrodes in the array that, when activated with an irreversible electroporation (IRE) signal, ablate the designated tissue segments. The IRE generator is configured to ablate the designated tissue segments by applying the IRE signal to the pairs of electrodes. [Brief explanation of the drawings]

[0012] The present invention will be more fully understood from the following detailed description taken in conjunction with the drawings, in which: [Figure 1] FIG. 1 is a schematic depiction of a catheter-based, irreversible electroporation (IRE) ablation system including a planar array of electrodes, according to an exemplary embodiment of the present invention. [Figure 2] 2 is a side view of a flat array of electrodes of the catheter of FIG. 1, in accordance with an exemplary embodiment of the present invention. [Figure 3] 3 is a side view of the flat array of multiple electrodes of FIG. 2 highlighting electrode pairs selected for irreversible electroporation (IRE) ablation, according to an exemplary embodiment of the present invention. FIG. [Figure 4] 3 is a flow chart that schematically illustrates irreversible electroporation (IRE) using the planar array of multiple electrodes of FIG. 2, in accordance with an exemplary embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0013] Overview Irreversible electroporation (IRE), also known as pulsed field ablation (PFA), can be used as an invasive treatment modality to kill tissue cells in the surface tissue of a patient's organ cavity by exposing them to a high-voltage pulse. Specifically, IRE pulses have potential applications in killing myocardial tissue cells (e.g., myocardial tissue cells in a heart chamber) to treat cardiac arrhythmias. Of particular note is the use of bipolar electrical pulses (e.g., using a pair of electrodes in contact with the tissue on a catheter) to kill tissue cells between the electrodes. Cell destruction occurs when the transmembrane potential exceeds a threshold, resulting in cell death and the development of tissue degeneration.

[0014] To effectively use IRE to ablate selected tissue, it is important that the electrode delivering the IRE pulse be able to contact the selected tissue. This is possible with virtually any catheter, such as a focal catheter or basket catheter, but if large areas of tissue are to be ablated, these types of catheters must be moved to precisely position the electrode. Furthermore, the electrode must maintain contact with the tissue on the cardiac surface while the heart wall is moving, which, among other things, can make the procedure more complicated and increase the time required to complete the ablation.

[0015] The use of multiple electrodes, when positioned simultaneously in close proximity to each other and in contact with the superficial tissue, can enhance the effectiveness of IRE ablation because they enhance the applied electric field and, in some cases, allow local control of the field direction, providing better selectivity and facilitating irreversible electroporation of only cardiac cells.

[0016] In an exemplary embodiment of the invention described below, an array catheter, e.g., a flat array catheter, having multiple electrodes is used to apply IRE pulses to the inner surface of a cavity within a patient's organ into which the flat array is inserted.

[0017] In one exemplary embodiment, a physician inserts an array attached to the distal end of a catheter into a cavity and contacts the array with the interior surface of the cavity. The physician designates one or more tissue segments on the interior surface to be ablated. In response to the designation, a processor selects one or more pairs of electrodes in the array that, when activated with an IRE signal, ablate the designated tissue segments. An IRE pulse generator controlled by the processor applies the IRE signal to the electrode pairs, thereby ablating the designated segments.

[0018] In some exemplary embodiments, the array is flat, while in other exemplary embodiments, the array is curved, such as, for example, an array of basket catheters. The array is typically a two-dimensional array, but may also be a one-dimensional array.

[0019] In one exemplary embodiment, input from the physician (i.e., user) is based on a visualization to the physician of the position of the array relative to the cavity. In another exemplary embodiment, the user receives input indicating a partial subset of electrodes in the array that are in contact with the interior surface of the cavity. In yet another exemplary embodiment, the user receives input indicating one or more areas on the interior surface of the cavity that are in contact with the array.

[0020] In one exemplary embodiment, the physician receives an indication as to which electrodes in the catheter's electrode array are in contact with tissue by measuring the frequency response of each electrode in the catheter to determine whether that electrode is in physical contact with tissue, for example, as described in U.S. Patent Application Publication No. 2019 / 0365463, assigned to Biosense Webster, Inc. The physician then selects at least those electrodes in the array as described below.

[0021] In another exemplary embodiment, a physician may use the typically large area of ​​an array of the disclosed electrodes to simultaneously ablate separate tissue regions that are considered to be in contact with the electrodes of the array, for example, by selecting a subset of electrodes, one for each region.

[0022] In one exemplary embodiment, the electrodes are formed as short cylinders on the tubing, with insulated leads for the electrodes inside the tubing, and the tubing is deployed in a "flyswatter" fashion, such as found in the Picasso™ catheter manufactured by Biosen-Webster, Inc. (California). By forming the electrodes as relatively massive cylinders around the tubing, the electrodes can transmit high IRE voltages without breaking down. Irrigation fluid can also be delivered through the tubing, which can cool the edges of the electrodes and avoid voltage breakdown.

[0023] In another exemplary embodiment, the electrodes are formed on an expandable, flexible distal assembly that includes two flexible substrates onto which an array of electrodes is printed, along with electrical leads to the electrodes. The substrates are cemented together on either side of a flat, flexible Nitinol backing sheet, into which irrigation channels are formed. Irrigation is achieved by flowing coolant through holes in the substrates that connect to the channels and into the blood near the electrodes.

[0024] Alternatively, a cooling fluid may be circulated in a closed loop within a channel that is in thermal contact with the blood. An expandable, flexible distal-end assembly with two cooling options is described in U.S. Patent Application No. 16 / 852,165, filed April 17, 2020, entitled "Flexible Distal-End Assembly With Double-Sided Electrode Array And Irrigation," the disclosure of which is incorporated herein by reference.

[0025] In the disclosed methods, the catheter is guided to the desired portion of tissue using an electrical and / or magnetic tracking system. Once the catheter is in place, the physician using the catheter utilizes a provided protocol to select which electrodes should be used for IRE ablation and to select the parameters of the IRE pulse.

[0026] By using an array (e.g., planar array) catheter and selecting electrode pairs and IRE parameters, the disclosed method can achieve efficient and consistent ablation over large areas and complex tissue anatomies.

[0027] System Description 1 is a schematic depiction of a catheter-based, irreversible electroporation (IRE) ablation system 20 including a planar electrode array catheter 21, according to an exemplary embodiment of the present invention. System 20 is used to position a planar array 50 (FIG. 2) of multiple electrodes 55, such as the aforementioned Picasso™ catheter, shown attached to the distal end of a shaft 22 in inset 25, for IRE ablation of targeted cardiac tissue in a heart 26 of a patient 28.

[0028] The physician 30 guides the planar array 50 to a target tissue location within the heart 26 by manipulating the shaft 22 using a manipulator 32 near the proximal end of the catheter and / or using deflection from the sheath 23. The planar array 50 is inserted through the sheath 23 in a collapsed configuration, and only after the sheath 23 is retracted does the planar array 50 resume its intended functional shape. By housing the planar array 50 in a collapsed configuration, the sheath 23 also serves to minimize vascular trauma along the path to the target location.

[0029] Typically, the planar array 50 is used in diagnostic or therapeutic procedures, such as, for example, spatially mapping the heart and mapping respective electrical potentials within the heart prior to ablation of cardiac tissue.

[0030] As mentioned above, the planar array 50 includes multiple electrodes (seen in FIG. 2) arranged on a large-area assembly of electrodes and has multiple uses (i.e., guidance, sensing, and ablation). The electrodes are connected by wires extending through the shaft 22 to an IRE pulse generator 37 that includes processor-controlled switching circuitry 38 (e.g., an array of relays) within the console 24. Using circuitry 38, a system processor or a physician may select which electrodes to connect to the pulse generator 37 for application of an IRE pulse.

[0031] Console 24 includes a processor 41, typically a general-purpose computer, with suitable front-end and interface circuitry 44 for receiving signals from patch electrodes 49. The signals from electrodes 49 may be electrocardiogram (ECG) signals and / or position signals for use in the Advanced Catheter Location (ACL)-style catheter position tracking method described below. Processor 41 is connected to patch electrodes 49, which are attached to the skin on the chest of patient 26, by wires extending through cable 39.

[0032] In some exemplary embodiments, processor 41 precisely determines the position coordinates of the electrodes of planar electrode array 50 within heart 26. Processor 41 determines the position coordinates based on input information such as the measured impedance between the electrodes (on the catheter) and ACL patch electrode 49 (i.e., using the ACL method described below). Console 24 drives display 27, which shows the distal end of the catheter positioned within the heart.

[0033] Once the processor 41 calculates the estimated location within the patient's heart of at least a portion of the electrodes of the planar array 50, any given signal, e.g., an electrophysiological signal, received from that electrode can then be associated with the location at which the signal was obtained.

[0034] ACL-style electrode position sensing methods using system 20 have been implemented in a variety of medical applications, including the CARTO™ system manufactured by Biosense-Webster, Inc. (Irvine, Calif.), which are described in detail in U.S. Patent Nos. 7,756,576, 7,869,865, and 7,848,787, the disclosures of which are all incorporated herein by reference.

[0035] Console 24 further includes a magnetic sensing subsystem. Patient 28 is placed in a magnetic field generated by pads that include field generator coils 42 driven by unit 43. The magnetic field generated by coils 42 generates position signals in magnetic sensors 51 (shown in inset 25), which are mounted immediately proximal to planar array 50. The signals are further provided as corresponding electrical inputs to processor 41, which uses those inputs to calculate the roll angle of planar array 50, for example, to correct for ACL-derived electrode positions and / or the orientation of planar array 50 within the cavity.

[0036] This method of position sensing using an external magnetic field has been implemented in a variety of medical applications, including the CARTO™ system manufactured by Biosense Webster, Inc. (Irvine, Calif.) This method is described in detail in U.S. Patent Nos. 5,391,199, 6,690,963, 6,484,118, 6,239,724, 6,618,612, and 6,332,089, WO 96 / 05768, and U.S. Patent Application Publication Nos. 2002 / 0065455(A1), 2003 / 0120150(A1), and 2004 / 0068178(A1), the disclosures of which are all incorporated herein by reference.

[0037] The processor 41 is typically programmed to carry out the functions described herein in software. The software can be downloaded to the computer in electronic form, for example over a network, or alternatively or additionally can be provided and / or stored on a non-transitory tangible medium, such as a magnetic, optical, or electronic memory. In particular, the processor 41 runs dedicated algorithms that enable it to carry out the steps described in FIG. 4.

[0038] For the sake of brevity and clarity, FIG. 1 shows only elements relevant to the disclosed technology. System 20 typically includes additional modules and elements not directly related to the disclosed technology and therefore intentionally omitted from FIG. 1 and the corresponding description. Another position tracking technique that may be used to track the location within heart 26 of electrodes on a planar array 50 similar to the ACL method described above is described in U.S. Patent Application No. 15 / 966,514, filed April 30, 2018, and entitled "Improved Active Voltage Location (AVL) Resolution," which is assigned to the assignee of the present patent application and is incorporated herein by reference.

[0039] Flexible distal tip assembly for bilayer electrode array and irrigation Figure 2 is a side view of a planar array 50 of multiple electrodes 55 of the catheter 21 of Figure 1, in accordance with an exemplary embodiment of the present invention. The electrode array assembly (i.e., the planar array of electrodes) shown is that of the Picasso™ catheter described above, although, as noted above, other planar electrode array assemblies may be used.

[0040] As shown, the planar array 50 comprises an array of cylindrical electrodes 55 mounted on tubes 57. The array is characterized by inter-electrode distances 70 and 72, which determine the strength of the electric field applied to the tissue between any two electrodes 55 for a given voltage of a bipolar electrical pulse applied between those electrodes 55. Furthermore, electrode pairs can be selected according to the direction of the electric field that is deemed most suitable for killing cardiac muscle cells with greater selectivity, as shown by field lines 60 and 61.

[0041] 2 schematically illustrates a region 62 including a subset of electrodes 55, which are selected using processor 41 instructing switching circuitry 38 to apply IRE ablation. Anatomical and / or physiological factor-driven selection and use of a subset of electrodes 55 for IRE ablation is described in connection with FIG.

[0042] Finally, cooling fluid is delivered to the electrode edges through tubing 57 to avoid voltage breakdown. The cooling fluid may circulate in a closed loop. Alternatively, the tubing may optionally include irrigation holes 59 for flowing (irrigating) cooling fluid (e.g., saline solution) into the blood near the electrode edges.

[0043] FIG. 3 is a side view of the planar array 50 of multiple electrodes 55 of FIG. 2, highlighting a subset of electrodes 75 and a subset of electrodes 175 selected for irreversible electroporation (IRE) ablation of distinct tissue regions 74 and 174, respectively, in accordance with an exemplary embodiment of the present invention.

[0044] In the illustrated exemplary embodiment, processor 41 determines that a subset of electrodes 75 and a subset of electrodes 175 of the electrode array are in contact with tissue regions 74 and 174, respectively, using, for example, one of the electrical, mechanical, or other available methods for determining physical contact between individual electrodes of the catheter and tissue. As illustrated, selected electrodes 75 and 175 are depicted shaded in black, in contrast to electrode 76, which is deemed not to be in contact with tissue. Thus, after processor 41 selects electrodes 75 and 175, it commands switching assembly 38 to connect electrodes 75 and 175 to IRE pulse generator 37 and apply a bipolar IRE pulse between the pair of electrodes 75 and a separate bipolar IRE pulse between the pair of electrodes 175. However, if the two regions are close to each other, processor 41 may group electrodes 75 and 175 together to determine the best electrode connection configuration for IRE ablation.

[0045] Processor 41 is used to select an IRE ablation protocol that includes bipolar IRE pulses. An example of an IRE ablation setting that can be used with electrodes 75 and 175 of catheter 21 is provided by Table I.

[0046] [Table 1]

[0047] As can be seen in the protocol of Table I, the direction of the applied electric field is selected by the user. FIG. 3 shows the physician 30 selecting and applying the pulses so that different tissue regions 78, 80, 82, 84, and 86 in contact with the electrodes 75 receive IRE pulses, resulting in electric fields oriented along directions 88, 90, 92, 94, and 96, respectively. Such selection may be, for example, appropriate to a known alignment of myocardial fiber cells suitable for selectively killing them. One possible means for allowing the user to select the electric field direction is a graphical user interface that inputs the selected electric field direction into a processor, which then selects pairs of electrodes 75 between which to apply the pulse according to the input. However, other methods, such as selecting one of a number of possible preset directions, may also be used.

[0048] Figure 4 is a flow chart that schematically illustrates a method for applying irreversible electroporation (IRE) using the planar array 50 of multiple electrodes 55 of Figure 2, in accordance with an exemplary embodiment of the present invention. In the embodiment presented here, the algorithm executes a process that begins in planar array guidance step 102 when a physician 30 guides the planar array 50 to a target tissue location within a patient's organ (e.g., the ostium of the heart) using, for example, electrodes 55 as ACL sensing electrodes.

[0049] Next, physician 30 positions planar array 50 at the ostium in planar array positioning step 104. Subsequently, in electrode physical contact determination and electrode selection step 106, processor 41 determines which electrodes 55 are in contact with tissue, and physician 30 selects at least some of these electrodes for application of an IRE pulse.

[0050] Next, in electrode configuration step 108, processor 41 receives user input, which may be, for example, input from step 106 and / or may be input in the form of one or more predetermined directions (e.g., relative to the longitudinal axis of the distal tip) in which the electric field should be applied to the tissue. The predetermined directions may be different for different tissue regions, as described above. Based on the required electric field directions, processor 41 determines selected pairs of electrodes between which an IRE pulse should be applied.

[0051] Next, in a pair electrode connection step 110, processor 41 controls switching assembly 38 to connect the pair of electrodes to IRE pulse generator 37 according to the determined configuration.

[0052] Next, in IRE parameter selection step 112, processor 41 receives an ablation protocol (e.g., uploaded from memory) that includes IRE ablation parameters (e.g., number of pulses and peak voltage). At this stage, the physician may modify some of the parameters. Alternatively, the protocol may have been loaded earlier in the procedure and be ready to use at this stage.

[0053] Finally, in IRE processing step 114, processor 41 commands IRE pulse generator 37 to apply a directional IRE pulse to the tissue via the selected pair of electrodes 55.

[0054] 4 is an exemplary flow shown purely for clarity. Additional steps, such as applying irrigation, may be included. In alternative embodiments, any other suitable method flow may be used. For example, if there is not enough information regarding the orientation of the cardiomyocytes, processor 41 may control switching assembly 38 to apply IRE pulses in multiple (typically two) different orientations to the same region of tissue. For example, processor 41 may control switching assembly 38 to apply IRE pulses in two mutually orthogonal directions.

[0055] Although the exemplary embodiments described herein relate primarily to cardiac applications, the methods and systems described herein may also be used in other medical applications, such as neurology, ENT, and renal denervation.

[0056] It will therefore be understood that the above-described embodiments are given by way of example, and that the present invention is not limited to what has been particularly shown and described above. Rather, the scope of the present invention includes both combinations and subcombinations of the various features described in the foregoing specification, as well as variations and modifications thereof that would occur to one skilled in the art upon reading the foregoing description, and that are not disclosed in the prior art. Documents incorporated by reference into this patent application are to be deemed part of this application, except that if any term is defined in such incorporated document in a way that contradicts the definition given herein, either expressly or impliedly, then only the definition given herein shall be considered.

[0057] [Embodiment] (1) A method for applying irreversible electroporation, comprising: inserting an array of electrodes attached to a distal end of a catheter into a cavity in an organ of a patient; contacting the array with an interior surface of the cavity; receiving input from a user specifying one or more tissue segments on the inner surface to be ablated; In response to the input, using a processor, selecting one or more pairs of the electrodes in the array to be driven with an irreversible electroporation (IRE) signal to ablate the designated tissue segment; ablating the designated tissue segment by applying the IRE signal to the pair of electrodes; A method comprising: (2) The method of embodiment 1, wherein receiving the input includes having the user visualize the position of the array relative to the cavity, and receiving the input in response to the visualized position. (3) The method of embodiment 1, wherein receiving the input includes indicating to the user a partial subset of the electrodes in the array that are in contact with the inner surface of the cavity, and receiving the input in response to the subset. (4) The method of embodiment 1, wherein receiving the input includes indicating to the user one or more areas on the inner surface of the cavity that are in contact with the array, and receiving the input in response to the one or more areas. (5) The method of embodiment 1, wherein contacting the array with the inner surface of the cavity includes measuring impedance using the plurality of electrodes.

[0058] (6) The method of embodiment 1, wherein contacting the array with the inner surface of the cavity includes measuring the shape of the array. (7) The method of embodiment 1, wherein contacting the array with the inner surface of the cavity includes measuring a contact force between the array and the surface. (8) The method of embodiment 1, wherein the array is a flat array. (9) A system for applying irreversible electroporation, comprising: a processor attached to a distal end of a catheter, the processor connected to an array of electrodes inserted into a cavity within a patient's organ and brought into contact with an inner surface of the cavity; receiving input from a user specifying one or more tissue segments on the interior surface of the cavity to be ablated; selecting one or more pairs of electrodes in the array to be driven with an irreversible electroporation (IRE) signal to ablate the designated tissue segment; a processor configured to: an IRE generator configured to ablate the designated tissue segment by applying the IRE signal to the pair of electrodes; A system comprising: (10) The system of embodiment 9, wherein the processor is configured to allow the user to visualize the position of the array relative to the cavity and to receive the input according to the visualized position.

[0059] (11) The system of embodiment 9, wherein the processor is configured to present to the user a partial subset of the electrodes in the array that are in contact with the inner surface of the cavity and receive the input according to the subset. (12) The system of embodiment 9, wherein the processor is configured to indicate to the user one or more areas on the inner surface of the cavity that are in contact with the array and receive the input in response to the one or more areas. (13) The system of embodiment 9, wherein the array is a planar array.

Claims

1. 1. A system for applying irreversible electroporation, comprising: a processor attached to a distal end of a catheter, the processor connected to an array of electrodes inserted into a cavity within a patient's organ and brought into contact with an inner surface of the cavity; indicating to a user one or more areas on the interior surface of the cavity that are in contact with the array; receiving input from the user, responsive to the one or more regions, specifying one or more tissue segments on the inner surface of the cavity to be ablated and a direction of an electric field directed along the inner surface to be applied to at least one of the one or more tissue segments; selecting one or more pairs of the electrodes in the array that, when driven with an irreversible electroporation (IRE) signal, apply the electric field in the specified direction to ablate the specified tissue segment; a processor configured to: an IRE generator configured to ablate the designated tissue segment by applying the IRE signal to the pair of electrodes; A system comprising:

2. The system of claim 1 , wherein the processor is configured to allow the user to visualize a position of the array relative to the cavity and to receive the input in response to the visualized position.

3. 2. The system of claim 1, wherein the processor is configured to present to the user a partial subset of the electrodes in the array that are in contact with the inner surface of the cavity and to receive the input in response to the partial subset.

4. The system of claim 1 , wherein the direction of the applied electric field for each of the one or more tissue segments is specified by the user.

5. The system of claim 1 , wherein the array is a planar array.

6. 2. The system of claim 1, wherein the processor is configured to control the electrode pairs and the IRE generator to apply IRE pulses to the same region of the one or more tissue segments at a plurality of different orientations along the direction of the electric field.

7. The system of claim 6 , wherein the different electric field directions are two mutually orthogonal directions.

8. 2. The system of claim 1, wherein the array of electrodes includes a first array of electrodes and a second array of electrodes adjacent to the first array of electrodes, the pair of electrodes includes a first electrode and a second electrode, the first electrode is disposed within the first array of electrodes and the second electrode is disposed within the second array of electrodes, and the direction of the electric field is along an axis passing through the first electrode and the second electrode.

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