Patent Publication Number: US-2023163315-A1

Title: Electrode Ink Deposition System for High-Throughput Polymer Electrolyte Fuel Cell

Description:
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
     This invention was made with government support under Contract No. DE-ACO2-06CH11357, awarded by the U.S. Department of Energy to UChicago Argonne, LLC, operator of Argonne National Laboratory. The government has certain rights in the invention. 
    
    
     FIELD OF THE DISCLOSURE 
     The present disclosure is directed to fuel cell technology and, in particular, to methods and systems for rapid and precise fabrication of membrane electrode assemblies of such fuel cells to facilitate rapid testing and characterization of electrode materials with minimal waste of electrode materials. 
     BACKGROUND 
     As new applications of battery and fuel cell technology continue to emerge, a variety of factors are driving the development Polymer Electrolyte Membrane or Proton Exchange Membrane Fuel Cells (PEMFCs). One example of such an application is electric vehicles (EVs), which, as a result of the desire to lower vehicle emissions and emissions in general, are becoming more common. For EVs to be practical and successful in the market, they require power sources (e.g., batteries) or energy conversion devices that convert fuel to electricity with high efficiency (e.g., fuel cells) with a number of attributes. The EV application requires low operating temperatures for quick start, safe operation, and high energy density to achieve maximum range with minimal weight and volume. 
     In general, fuel cells are electrochemical devices that convert energy from a fuel and an oxidizing agent into electricity.  FIG.  1    illustrates a PEMFC at its most basic level. Fuel provided to an anode causes electrons to migrate across an electrolyte to a cathode supplied with an oxidizing agent. In many fuel cells, the fuel is hydrogen and the oxidizing agent is oxygen, typically from air. The hydrogen combines with the oxygen to produce electricity and water. PEMFCs use a polymer membrane for the electrolyte, removing liquid electrolytes from the picture. 
     Though PEMFCs have a variety of components, as illustrated in  FIG.  2   , the “heart” of a PEMFC is the membrane electrode assembly (MEA). The MEA is typically a polymer membrane having on each side of it a catalyst-coated carbon paper or a catalyst-coated membrane placed between two carbon papers. A solubilized form of the membrane (i.e., ionomer) is typically used as a binder and to provide proton conductivity in the electrode layers. MEAs are fabricated by applying this catalyst-ionomer-solvent “ink” to a carbon paper to form a gas diffusion electrode (GDE) with subsequent hot-pressing to the membrane or by applying the catalyst ink to a substrate with subsequent transfer to the membrane or directly to the membrane to form a catalyst-coated membrane (CCM). The most common catalyst is Platinum, though other noble metals may be used. Platinum is preferred because of its high catalytic activity and stability. However, the high costs of Platinum and other noble metals used for catalysts remains a key challenge slowing commercialization and adoption of fuel cell technology, especially for automotive uses. Therefore, finding alternative catalysts and, in particular, platinum group metal free (PGM-free) catalysts, is a priority of many research groups studying fuel cells. 
     Testing MEAs manufactured with different catalysts and/or membranes for analysis of performance and stability can be a laborious and time-consuming process. For example, a conventional single cell test setup can require an entire day to complete fuel cell performance measurements: warming up the cell/humidifier system, conditioning the electrode, acquiring polarization curve and other diagnostic data, and assembling/disassembling the cell and test setup. Commercial systems exist that can test the performance of multiple cathodes simultaneously, however such systems require precise placement on the membrane of each cathode being tested, which negates some of the benefits of being able to test multiple cathodes simultaneously. 
     While some conventional fabrication techniques, such as spraying electrode ink over a mask to make patterned electrodes on a membrane, allow for the fabrication of multiple electrodes in a particular pattern dictated by the multi-electrode cell hardware, such techniques each have their drawbacks. It is difficult to control precise catalyst loading when spraying the electrode ink, for example, and much of the ink is sprayed onto the mask, resulting in unnecessary waste. It is also more difficult to apply different catalyst formulations at each of the spots in the electrode pattern. 
     SUMMARY OF THE DISCLOSURE 
     One embodiment of a system according to the present disclosure includes a linear stage having a platform and a base, the platform movable along X and Y axes according to electronic signals received from a controller device communicatively coupled to the linear stage. A vacuum source is configured to create vacuum pressure is coupled to a vacuum port of a heated vacuum table physically coupled to the platform of the linear stage and having a working face parallel to both the X and Y axes. The working face has, formed therein, a plurality of channels in fluid communication with the vacuum port formed in the vacuum table. The system also includes a sheet of perforated heat-conductive material sized to fit on the working face of the vacuum table the sheet having a table-facing side placed against the working face of the vacuum table and a mesh-facing side, and having staggered holes configured to evenly distribute the vacuum pressure from the plurality of channels to the mesh side of the sheet. Further, system includes a heat-conductive wire mesh having a sheet-facing side placed against the mesh-facing side of the sheet and a working side, the wire mesh having openings smaller than the staggered holes such that a membrane material placed on the working side of the wire mesh is not deformed by the vacuum pressure. The system includes a nanopipette or micropipette coupled to a pump and configured to deposit ink onto an exposed surface of the membrane material as the controller device causes the linear stage to move the heated vacuum table to control deposition of the ink onto the exposed surface of the membrane material. 
     An embodiment of a method for creating a catalyst coated membrane electrode according the present description includes placing a membrane material onto a heated vacuum table assembly, positioning a nanopipette or micropipette adjacent to the membrane material, and coupling the nanopipette or micropipette to a source of electrode ink, the electrode ink comprising a solvent, a catalyst, and an ionomer. The method also includes operating a pump coupled to the nanopipette or micropipette and to the source of electrode ink to cause the electrode ink to be dispensed from the nanopipette or micropipette, and moving the heated vacuum table assembly relative to the nanopipette or micropipette to cause the electrode ink to be deposited onto the membrane material in a pattern defined by the movement of the heated vacuum table. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The following detailed description will be more easily and better understood when considered in conjunction with the following figures, in which like reference numbers are employed to designate like structures. It should be understood that, with the exception of magnified images, the drawings are not to scale, as scaled drawings would not facilitate an understanding of the depicted structures. 
         FIG.  1    is a diagram illustrating the principle of operation of a polymer electrolyte membrane fuel cell; 
         FIG.  2    is a diagram illustrating a polymer electrolyte membrane fuel cell assembly; 
         FIG.  3    is an illustration of a system for creating a fuel cell according to the present disclosure; 
         FIG.  4    is a perspective view of a vacuum table according to the present description; 
         FIG.  5    is a top plan view of the vacuum table of  FIG.  4   ; 
         FIG.  6    is a side elevation view of the vacuum table of  FIG.  4   ; 
         FIG.  7    is an exploded perspective view of an XY stage and a vacuum table; 
         FIGS.  8 A to  8 C  illustrate various arrangements of layered materials placed on the vacuum table in various embodiments; 
         FIG.  9    depicts various components of the system according to the present description; 
         FIG.  10    depicts a pattern according to which the XY table is operated in embodiments; 
         FIG.  11    depicts an electrode printed on a membrane placed on a vacuum table assembly according to the present description; 
         FIG.  12    depicts a multiplicity of electrodes printed on a membrane placed on a vacuum table assembly according to the present description; 
         FIG.  13    is a block diagram depicting the various elements of an embodiment of the system according to the present description; and 
         FIG.  14    is a flow chart depicting a method of creating one or more electrodes according to the present description. 
     
    
    
     DETAILED DESCRIPTION 
     Methods and systems in accordance with the present description overcome the limitations of prior art methods of producing MEAs (also referred to herein as electrodes) generally and, in particular, of accurately and reproducibly fabricating MEAs in a configuration compatible with high throughput test fixtures used to characterize and test the MEAs. With reference to  FIG.  3   , the methods and systems described herein employ a vacuum table assembly  100  mounted on a high-precision, computer-controlled XY stage  102  (also referred to as a linear stage) that positions the vacuum table assembly  100  relative to a nanopipette or micropipette  104 . A high-precision low flow rate pump  106  controlled in coordination with the XY stage  102  delivers electrode ink from an ink source  108  to the pipette  104  and onto a substrate membrane  110  mounted on the vacuum table assembly  100  to from an electrode  112 . 
     The vacuum table assembly  100  includes a vacuum table  114 , one embodiment of which is depicted in perspective view in  FIG.  4   , in a top plan view in  FIG.  5   , and in a front elevation view in  FIG.  6   . The vacuum table  114  is generally a machined or injection molded form having a planar surface  116  that serves as a working face of the vacuum table. One or more channels  118  formed in the planar surface  116  serve to provide fluid communication between the planar surface  116  and port  120  to which a vacuum source may be coupled, such that, when vacuum is applied to the port  120 , air may be drawn through the channels  118  to the port  120 . As should be understood, a planar sheet placed against the planar surface  116  may be held against the planar surface  116  by a vacuum created in the channels  118  when suction is applied at the port  120 . In particular, the membrane  110  of the MEA, onto which the electrode ink is deposited in order to create the electrode, is held securely by the vacuum. Additionally, while the solvent that makes up the electrode ink may cause the membrane  110  to deform, the vacuum may maintain the membrane  110  in a generally planar form. 
     In embodiments, the membrane  110  is formed of a synthetic polymer and, in particular ones of these embodiments, the synthetic polymer is an ionomer polymer. One example of an ionomer polymer that may be employed as the membrane  110  is a sulfonated tetrafluoroethylene based fluoropolymer-copolymer, such as Nafion  6  perfluorinated membrane registered trademark of The Chemours Company FC, LLC. 
     The electrode ink may comprise one or more catalysts, one or more ionomers, and carbon in a solvent, in embodiments. The ratios of the catalyst(s), ionomer(s), carbon, and solvent, and the particular substances used for each, may vary from ink to ink. 
     In embodiments, such as that depicted in  FIGS.  4 - 6   , the port  120  may formed as a channel in the vacuum table  114 , and may have internal threads  120 A for coupling a conduit (not shown in  FIGS.  4 - 6   ) extending between a vacuum pump (not shown in  FIGS.  4 - 6   ) and the port  120 . As should be understood, in other embodiments, the port  120  may protrude from the vacuum table  114 , and may have external threads for coupling the conduit extending between the port and the vacuum pump. 
     In an embodiment, the channels  118  are formed in the planar surface  116  as a plurality of intersecting, linear channels  122  (as depicted in  FIGS.  4 - 6   ), such that each of the linear channels  122  extends in one direction across the planar surface  116  from one side of the planar surface  116  to an opposing side of the planar surface  116 . In the embodiment of  FIGS.  4 - 6   , four linear channels  122  extend parallel to an arbitrarily selected Y-axis along an arbitrarily selected X-axis, while three linear channels  122  extend parallel to the X-axis along the Y-axis. Preferably, the linear channels  122  spaced along a particular dimension are evenly spaced, though this is not necessarily a requirement. Likewise, while not required, it is preferable that the linear channels  122  extend almost entirely from a first side of the planar surface  116  to an opposing side of the planar surface  116 . In embodiments, the linear channels  122  extend to within 0.125 inches from each side of the planar surface  116 . In other embodiments, the linear channels  122  may extend to within about 0.1 inches, about 0.2 inches, about 0.25 inches, about 0.5 inches, about one inch, or more than one inch from each side of the planar surface  116 . In still other embodiments, the linear channels  122  may extend to the edges of the planar surface  116 . 
     While depicted in  FIGS.  4 - 6    as linear channels  122 , the one or more channels  118  need not be linear in all embodiments. Other arrangements of channels, while not depicted, are nevertheless expressly contemplated, including concentric circular channels, nested rectangular channels, boustrophedonic channels, spiral channels, and the like, so long as the channels are configured such that vacuum pressure applied at the port  120  is generally communicated to all portions of the channel or channels. Additionally, while it is preferable that the channels  118  are symmetrical across the planar surface  116 , such symmetry is not a requirement. 
     The one or more channels  118  in the planar surface  116  may have a depth, d 1 , relative to the planar surface  116 , that is exceeded by their width. For example, in an embodiment, the width of each channel is 0.25 inches, while the depth of each channel is 0.125 inches. 
     In embodiments, a channel  124  couples the one or more channels  118  in the planar surface  116  to the port  120 . The channel  124  may be orthogonal to channels  118  and also to the port  120 , in embodiments, but need not be orthogonal so long as the channel  124  provides fluidic communication between the port  120  and the channels  118 . Further, while  FIGS.  4 - 6    depict a single channel  124  fluidically coupling the plurality of channels  118  in the planar surface  116  to the port  120 , in embodiments, multiple channels  124  may couple the port  120  to the channels  118  in the planar surface  116 . Further, the various channels  118  in the planar surface  116  may be fluidically coupled to one another by intersections between the channels  118 , as depicted in  FIGS.  4 - 6   , or may be fluidically coupled to one another via multiple channels  124 , as should be readily understood. 
     In embodiments, the planar surface  116  may be bounded by a raised lip  126  (i.e., a raised piece along the edge) extending along the perimeter of the planar surface  116 . The lip  126  may serve to assist in properly positioning other components of the table assembly  100  (described below), as well as in maintaining vacuum pressure between those other components and the one or more channels  118  formed in the planar surface  116 . 
     One or more apertures  128  may extend orthogonally through the vacuum table  114  between the planar surface  116  and an opposing surface of the vacuum table  114  to facilitate secure connection of the vacuum table  114  to the XY stage  102 . In embodiments, the apertures  128  may each include a counterbore  130  such that a head of a fastener (not shown) inserted into the aperture  128  is disposed below the planar surface  116  and does not prevent other components placed on the planar surface  116  from sitting flush with the planar surface  116 . Of course, the vacuum table  114  may be secured to the XY stage  102  using methods other than fasteners inserted into apertures, such methods including clamps, slide locks, welds, rivets, etc. 
     In embodiments, the vacuum table  114  is configured to be heated. Heating the vacuum table may advantageously facilitate improved and/or accelerated evaporation of the ink solvent from the membrane  110  as ink is deposited on the membrane  110 . As depicted in  FIGS.  4 - 6   , in embodiments, the vacuum table  114  is formed from a thermally-conductive material (e.g., metal) and includes a plurality of apertures  132 A,  132 B into which heating elements (not shown) may be inserted. The apertures  132 A,  132 B may be arranged such that heat generated by the heating elements is distributed evenly within the surface of vacuum table  114 . In  FIGS.  4 - 6   , for example, the apertures  132 A are formed in a first perimeter surface  134 A, and the apertures  1326  are formed in a second perimeter surface  1346  opposite the first perimeter surface  134 A. In embodiments, the apertures  132 A,  1326  are positioned symmetrically about one, two, or more than two axes parallel to the planar surface  116 , and/or such that the heating elements inserted into the apertures  132 A,  1326  are positioned symmetrically about one, two, or more than two axes parallel to the planar surface  116 . A depth, d 2 , of the apertures  132 A,  1326  below the planar surface  116  will be greater than the depth, d 1 , of the one or more channels  118 . 
     The vacuum table  114  may be heated to a desired temperature according to a variety of factors including the temperature at which the ink solvent (e.g., water, alcohol, etc.) evaporates, the membrane material&#39;s composition, and the like. In embodiments, the vacuum table  114  is heated to a temperature high enough to quickly evaporate the ink solvent before shrinking or swelling the membrane  110 . In particular embodiments, the vacuum table  114  is heated to a temperature between 80° C. and 90° C., or to a temperature between 80° C. and 110° C., or to a temperature between 80° C. and 100° C. 
     An additional aperture  136  may extend from one of the perimeter surfaces (e.g., from the surface  134 A, the surface  1348 , etc.) into the vacuum table  114 . The aperture  136  may facilitate insertion into the vacuum table  114  of a temperature sensor such as a thermistor or other temperature probe (not shown) that can measure a temperature of the vacuum table  114 . In embodiments, the aperture  136  extends into the vacuum table  114  at a depth, d 3 , from the planar surface  116  that exceeds the depth, d 1 , of the one or more channels  118 , but does not exceed the depth, d 2 , of the apertures  132 A,  132 B. The temperature probe may communicate a feedback signal representative of the measured temperature to a controller (described below) according to which the controller may increase or decrease the temperature of the heating elements. 
       FIG.  7    is an exploded perspective view of the XY stage  102  and the vacuum table  114 . As illustrated in  FIG.  7   , a rubber pad  140  may be placed between the vacuum table  114  and the XY stage  102  to insulate the XY stage  102  from the heat generated by the vacuum table  114 . In particular, the rubber pad  140  may be placed on a surface  142  of the XY stage  102 , to which surface  142  the vacuum table  114  is attached. Accordingly, the rubber pad  140  may include apertures  144  sized and positioned to allow fasteners to extend between the vacuum table  114  and the surface  142  of the XY stage  102 . 
     As described above, the membrane  110  may deform when wet by the solvent used in the electrode ink. The vacuum pressure applied by the vacuum table  114  counteracts this tendency by pulling the membrane  110  flat. However, to prevent the membrane  110  from being pulled into the channels  118 , one or more intervening surfaces are preferably placed on the vacuum table  114  and, in particular, on the planar surface  116 .  FIG.  8 A  depicts an embodiment of a stack  150  that may be placed on the planar surface  116  of the vacuum table  114 . The stack  150  and the vacuum table  114  comprising the vacuum table assembly  100 . 
     In an embodiment, the stack  150  includes a perforated sheet  152  and a wire mesh material  154  onto which the membrane  110  is placed. The perforated sheet  152  is a planar sheet having staggered holes  156  that allow the vacuum pressure to transmit through the perforated sheet  152 . In embodiments, the perforated sheet  152  is formed of a thermally conductive material, such that the heat from the vacuum table  114  is transmitted to the perforated sheet  152 , bringing the heat closer to the membrane  110  such that the solvent of the electrode ink is quickly evaporated and the membrane  110  restored to its generally planar disposition. In embodiments, the perforated sheet  152  is formed from stainless steel. In a particular embodiment, the perforated sheet  152  is 0.024″ (0.6 mm) thick, the holes  156  each have a diameter of 0.0625″ (1.6 mm) and have a hole-to-hole pitch (center to center) of 0.109″ (2.8 mm), and have an open area (i.e., an area of the holes relative to the total surface area) of approximately 30%. 
     The perforated sheet  152  may nevertheless allow the vacuum pressure from the vacuum table  114  to distort the surface of the membrane  110  by pulling the membrane  110  into the holes  152 . In order to prevent such distortion, the wire mesh material  154  is placed over the perforated sheet  152  before placing the membrane  110  on the stack  150 . In contrast to the perforated sheet  152 , which is preferably rigid, the wire mesh material  154  is generally flexible and sufficiently permeable to transmit the vacuum pressure to the membrane  110  to hold it flat against the wire mesh material  154 , which is significantly more flat than applying only the perforated sheet  152 . In embodiments, the wire mesh material  154  is formed of a thermally conductive material, such that the heat from the vacuum table  114  is transmitted to the wire mesh material  154 , bringing the heat closer yet to the membrane  110  such that the solvent of the electrode ink is quickly evaporated and the membrane  110  restored to its generally planar disposition. In embodiments, the wire mesh material  154  is formed from stainless steel. In a particular embodiment, the wire mesh material  154  is formed from wire having a diameter of 0.0026″ (66 μm), mesh openings of 0.0041″ (104 μm), and an open area (i.e., an area of the mesh openings relative to the total surface area) of approximately 38%. 
       FIG.  8 B  depicts an alternate embodiment of a stack  150 A that may be placed on the planar surface  116  of the vacuum table  114 . The stack  150  is similar to the stack  150  depicted in  FIG.  8 A , except that the stack  15 A includes an additional layer of wire mesh material  158 , even finer than the wire mesh material  154 , between the wire mesh material  154  and the membrane  110 . In embodiments, the wire mesh material  158  is formed of a thermally conductive material, such that the heat from the vacuum table  114  is transmitted to the wire mesh material  158  via the wire mesh material  154  and the perforated sheet  152 , bringing the heat closer yet to the membrane  110  such that the solvent of the electrode ink is quickly evaporated and the membrane  110  restored to its generally planar disposition. In embodiments, the wire mesh material  158  is formed from stainless steel. In a particular embodiment, the wire mesh material  158  is formed from wire having a diameter of 0.001″ (25.4 μm), mesh openings of 0.0015″ (38.1 μm), and an open area (i.e., an area of the mesh openings relative to the total surface area) of approximately 36%. 
       FIG.  8 C  is a side view (not to scale) showing the perforated sheet  152 , the wire mesh material  154 , and the membrane  110 . The perforated sheet  152  has a first, table-facing side  152 A and a second, mesh-facing side  152 B. The first and second sides  152 A,  152 B are generally planar, as depicted, excepting of course of the staggered holes  156 . While called out here for the purpose of explaining that one side (e.g., the first side  152 A) of the perforated sheet  152 , when positioned in the stack  150 , is adjacent to the working face  116  of the vacuum table  114 , and that another side (e.g., the second side  152 B) of the perforated sheet  152 , when positioned in the stack  150  is adjacent to the wire mesh material  154 , the two sides  152 A,  152 B are not specific in the depicted embodiments, and the perforated sheet  152  may be placed with either side  152 A or  152 B against the working face  116  of the vacuum table. (Other embodiments are contemplated, though not depicted or described explicitly, in which the sides  152 A and  152 B may require specific orientation with respect to the face that is adjacent to the working face  116  of the vacuum table  114 , as would be appreciated in view of the present description, without departing from the scope of the contemplated embodiments.) 
     The wire mesh material  154  has a first, sheet-facing side  154 A and a second, working side  154 B. The first and second sides  154 A,  15 BB of the wire mesh material  154  are generally planar (though not necessarily rigid), as depicted, excepting of course of the general topography of the mesh. While called out here for the purpose of explaining that one side (e.g., the first side  154 A) of the wire mesh material  154 , when positioned in the stack  150 , is adjacent to the mesh-facing side  152 B of the perforated sheet  152 , and that another side (e.g., the second side  154 B) of the wire mesh material  154 , when positioned in the stack  150  is adjacent to the membrane  110  (or to the additional layer of wire mesh material  158 ), the two sides  154 A,  154 B are not specific in the depicted embodiments, and the wire mesh material  154  may be placed with either side  154 A or  154 B against the perforated sheet  152 . (Other embodiments are contemplated, though not depicted or described explicitly, in which the sides  154 A and  154 B may require specific orientation with respect to the face that is adjacent to the perforated sheet  154 , as would be appreciated in view of the present description, without departing from the scope of the contemplated embodiments.) 
     It is worth mention that, in embodiments, the vacuum table  114  may be not be heated directly but, rather, the perforated sheet  152 , the wire mesh material  154 , and/or the wire mesh material  158  may be heated instead, for example, by passing an electric current through the perforated sheet  152 , the wire mesh material  154 , and/or the wire mesh material  158 . 
     While the stack  150  and the stack  150 A are depicted, respectively, in  FIGS.  8 A and  8 B  with each layer being progressively smaller in area than the layer closer to the vacuum table  114 , this convention is for illustrative purposes only so that the various layers are readily visible in the illustrations. There is no requirement that each layer is smaller than the layer on which it sits. In embodiments, the perforated sheet  152 , the wire mesh material  154  and, if present, the wire mesh material  158 , may all be the same size or may even decrease in size with each layer closer to the vacuum table  114 . In preferred embodiments, the area covered by the membrane  110  has beneath it the perforated sheet  152 , the wire mesh material  154  and, if present, the wire mesh material  158 . In other preferred embodiments, at least the area of the membrane  110  on which electrode ink will be deposited has beneath it the perforated sheet  152 , the wire mesh material  154  and, if present, the wire mesh material  158 . 
       FIG.  9    depicts the vacuum table assembly  100  in the context of the broader electrode forming system. The vacuum table assembly  100  is physically coupled to the XY stage  102 , with the rubber pad  140  disposed between the two. A pump  160  is coupled via a tube  161  or other fluid conduit to the port  120  of the vacuum table  114 , and pumps air from the port  120  to create suction in the plurality of channels  118  of the vacuum table  114 . The membrane  110  sits atop the stack  150 , which is placed on the surface  116  of the vacuum table  114 . A source  162  of electrode ink  170  is fluidically coupled by a PTFE Teflon tube  163  to a pump  164  that, in turn, is fluidically coupled by a PTFE Teflon tube  165  to a micropipette or nanopipette  166  having a tip  168  disposed at or near the membrane  110 . The pipette  166  and its tip  168  are fixed in space such that the tip  168  is configured to dispense the electrode ink  170  onto the membrane  110  at positions according to the movement, relative to the tip  168 , of the XY stage  102  and the vacuum table  114  disposed thereon. A controller  172  communicatively coupled to the XY stage  102  controls the XY stage  102  to cause movement in the X and Y directions, thereby controlling the position of the pipette tip  168  relative to the membrane  110 . The controller  172  (or another controller) may control the pump  160  and/or the pump  164 . 
     In embodiments, the pump  164  is a peristaltic pump configured to move the electrode ink  170  through the PTFE Teflon tube  163  (which is contiguous in such embodiments with the tube  165 ), into the pipette  166 , and through the tip  168  onto the membrane  110 . In particular embodiments, the peristaltic pump has a pump rate of approximately 0.31 μl/sec, of 0.25 to 0.35 μl/sec, of 0.20 to 0.40 μl/sec, of 0.29 to 0.33 μl/sec, of less than 0.35 μl/sec, of less than 0.30 μl/sec, of less than 0.50 μl/sec, or of less than 1 μl/sec. 
     The pipette tip  168  may have an aperture of 200 μm in embodiments. In other embodiments, the tip  168  may have an aperture of between 100 μm and 300 μm, between 150 μm and 250 μm, between 175 μm and 225 μm, of greater than 200 μm, of less than 250 μm, of less than 350 μm, or of less than 150 μm. In general, the aperture size of the pipette tip  168  is proportional to a size of particles suspended in the electrode ink  170 , and is sized to provide sufficient control of ink deposition while preventing the aperture of the pipette tip  168  from clogging. 
     By moving the XY stage  102  in the X- and/or Y-direction(s) and, as a result, causing the vacuum table assembly  100  to move correspondingly with respect to the pipette tip  168  positioned adjacent to the membrane  110 , the pipette tip  168  may deposit electrode ink on the membrane  110  in a desired pattern. The pattern may be programmed into a controller that controls the XY stage  102 , as further described below.  FIG.  10    shows one exemplary pattern  180  in which ink could be deposited on the membrane  110 . By taking into consideration the rate at which ink is being dispensed from the pipette tip  168 , the width of the ink&#39;s dispersion as it contacts the surface (which, as will be appreciated, will be a function of its viscosity and surface tension, among other things), and the desired thickness of the ink layer on the membrane  110 , the XY stage  102  can be programmed to move the vacuum table assembly  114  such that a layer of ink is deposited on the membrane  110 . In embodiments, the XY stage  102  has a resolution of 0.05 μm or less, allowing the XY stage  102  to cause lines of electrode ink to be deposited on the membrane  110  0.05 μm apart. In embodiments, the XY stage  102  has a resolution of 0.25 μm or less, of 0.2 μm or less, of 0.15 μm or less, or of 0.1 μm or less. 
     The membrane  110  may be sized according to the desired size of the electrode or electrodes to be created.  FIG.  11   , for example, depicts a membrane  110  disposed on the stack  150  and having printed on it an electrode  182 . The electrode  182  may be printed by moving the XY stage  102  relative to the pipette tip  168  while the pump  164  is pumping the ink  170 , for example in the pattern depicted in  FIG.  10   . It should be understood that, in embodiments in which the membrane  110  does not cover most or all of the surface of the wire mesh material  154  and/or the perforated sheet  152 , an additional material may be required to be positioned over the wire mesh material  154  and/or the perforated sheet  152  such that the vacuum pressure holds the membrane  110  flat against the wire mesh material  154  (rather than merely pulling air through the exposed wire mesh material  154  and the exposed perforated sheet  152 ). The additional material may be any flexible material (e.g., a non-air permeable material such as a thin plastic film) sufficient to ensure the vacuum pressure pulls the membrane  110  against the surface of the wire mesh material  154 . 
     In embodiments, multiple electrodes  182  may be printed on the membrane  110 , as depicted in  FIG.  12   . The multiple electrodes  182  may be printed in any desired pattern. Where each of the electrodes  182  is printed using the same electrode ink  170 , the electrodes  182  may be identical, or may vary in size, shape, or thickness of the deposited layer of electrode ink  170 . In other embodiments, different ones of the electrodes  182  may be printed using corresponding different formulations of electrode ink. That is, a first electrode ink formulation may be used to print one or more electrodes  182  in a first set of electrodes  182 , while a second, different ink formulation may be used to print one or more electrodes  182  in a second set of electrodes  182 . The electrodes  182  in the first set, in the second set, or in both sets, may likewise vary in size, shape, or thickness of the deposited layer of the respective electrode ink  170 . 
     Electrodes  182  created from different ink formulations may respectively be formed using different pipettes  166 , or by the same pipette  166  after the pipette  166  has been cleaned with a proper solvent such as Acetone or Isopropyl Alcohol, fluidically coupled to an ink source filled with a different ink formulation. In some embodiments, however, multiple ink sources  162  (e.g., an array of ink sources) and may be fluidically coupled to a corresponding array of pipettes  166  via corresponding pumps  164  (or a single pump  164  with multiple channels) to create multiple electrodes  182  simultaneously on the membrane  110 , as will be readily understood in view of the remainder of this description. 
     Of course, while depicted as circular in the various figures, the electrodes need not be circular and can, in fact, be any shape desirable for the application in question. Additionally, while, in embodiments, the electrodes are approximately 0.785 cm 2  (1 cm diameter), the size of the electrodes may likewise be any size desirable for the application in question. In embodiments, dimensions of the working surface  116  of the vacuum table are 6 inches by 6 inches (15.24 cm by 15.24 cm), providing a working surface  116  with an area of 36 in 2  (232.26 cm 2 ), and the membrane  110  has dimensions of 3.94 inches by 3.94 inches (10 cm by 10 cm), providing an area of 15.52 in 2  (100 cm 2 ) on which electrodes can be printed. A pattern of 25, equally spaced, electrodes having diameters of 1 cm may be created on such a membrane, in embodiments. 
       FIG.  13    is a block diagram of an exemplary system according to the presently described embodiments. As illustrated in  FIG.  13    a pump controller  184  may control the pump  164  that delivers the electrode ink  170  from the ink source  162  to the pipette  166 . Controlling the pump  164  may include controlling the on/off status of the pump  164  and/or may include controlling the rate at which the pump  164  is pumping the electrode ink  170 . A heater controller  186  may control heater elements  188  disposed in the aperture(s)  132 A,  1326  of the vacuum table  114 , controlling the current delivered to the heating elements  132 A,  132 B and, as a result, the heat generated by the heating elements  132 A,  1326 , to control the temperature of the vacuum table  114 . In embodiments, the heater controller  186  may receive a signal from a thermocouple  190  disposed in the aperture  136  of the vacuum table, the signal representing a temperature of the vacuum table  114 , and may control the heater elements  188  according, in part, to the signal received from the thermocouple  190 . A vacuum controller  192  may control the on-off state of the vacuum pump  160  and, in embodiments, may control the level of vacuum drawn by the pump  160 . The stage controller  172 , as described above, may control the position and movement of the XY stage  102  and, in particular, may control an X-servo  194  and a Y-servo  196  in the XY stage  102  that cause the surface  142  (and the vacuum table assembly  100  coupled to the surface  142 ) to move relative to the pipette  166 . While described herein as separate controllers, the pump controller  184 , the heater controller  186 , the vacuum controller  192 , and the stage controller  172  may be separate controllers or may be integrated into one or more controller devices. (For example, a computer workstation may be programmed, e.g., using LabView® software, to control all of the devices.) 
       FIG.  14    is a flow chart depicting an example method  200  for creating an electrode using the devices and systems described above. The membrane material  110  may be placed onto the heated vacuum table assembly  100  (block  202 ). Of course, this may involve placing the stack  150  onto the vacuum table  114  which, in turn, may involve placing the perforated sheet  152  on the surface  116  of the vacuum table  114 , placing the wire mesh material  154  (and possibly the wire mesh material  158 ) perforated sheet  152 , and then placing the membrane  150  on the wire mesh material  154  or  158 . Placing the membrane material  110  on the heated vacuum table assembly  100  may also require heating the vacuum table  114 , either before or after the membrane  110  is placed thereon. The method  200  also includes positioning the pipette  166  adjacent to the surface of the membrane  110  (block  204 ) and coupling the pipette  166  to the source  162  of the electrode ink  170  (block  206 ). Further, the method  200  includes operating the pump  164  to cause the electrode ink  170  to be dispensed from the pipette  166  through the pipette tip  168  on to the surface of the membrane  110  (block  208 ). The vacuum table  114  is moved relative to the pipette  166  using the XY stage  102  while the pump  164  is operating to cause the electrode to be printed on the membrane (block  210 ). 
     Of course, a person of ordinary skill in the art will readily appreciate that, unless one step is a necessary prerequisite to another, the order of the steps may vary from that described above. 
     The methods and systems described herein may, in embodiments, be employed to create electrode structures with multiple layers. The multiple layers may be made of the same composition or different compositions, may be of different thicknesses or the same thicknesses, may be patterned, graded, porous, etc. Any individual layer (whether part of a multiple layer electrode or a single layer electrode) may be patterned in any number of ways, limited only by the movement of the XY stage  102 . 
     The following list of aspects reflects a variety of the embodiments explicitly contemplated by the present application. Those of ordinary skill in the art will readily appreciate that the aspects below are neither limiting of the embodiments disclosed herein, nor exhaustive of all of the embodiments conceivable from the disclosure above, but are instead meant to be exemplary in nature. 
     1. A system comprising: a linear stage having a platform and a base, the platform movable along X and Y axes according to electronic signals received from a controller device communicatively coupled to the linear stage; a vacuum source configured to create vacuum pressure; a heated vacuum table physically coupled to the platform of the linear stage and having a working face parallel to both the X and Y axes, the working face having formed therein a plurality of channels in fluid communication with a vacuum port formed in the vacuum table, the vacuum port coupled to the vacuum source; a sheet of perforated heat-conductive material sized to fit on the working face of the vacuum table, the sheet having a table-facing side placed against the working face of the vacuum table and a mesh-facing side, and having staggered holes configured to evenly distribute the vacuum pressure from the plurality of channels to the mesh side of the sheet; a heat-conductive wire mesh having a sheet-facing side placed against the mesh-facing side of the sheet and a working side, the wire mesh having openings smaller than the staggered holes such that a membrane material placed on the working side of the wire mesh is not deformed by the vacuum pressure; and a nanopipette or micropipette coupled to a pump and configured to deposit ink onto an exposed surface of the membrane material as the controller device causes the linear stage to move the heated vacuum table to control deposition of the ink onto the exposed surface of the membrane. 
     2. A system according to aspect 1, wherein the heated vacuum table comprises a heating element disposed in an aperture, the heating element positioned to distribute heat evenly across the working face of the vacuum table. 
     3. A system according to aspect 1, wherein the heated vacuum table comprises a plurality of heating elements, each disposed in a corresponding aperture, the plurality of heating elements positioned to distribute heat event across the working face of the vacuum table. 
     4. A system according to any one of aspects 1 to 3, wherein the heated vacuum table comprises a thermocouple configured to detect a temperature of the working face of the heated vacuum table. 
     5. A system according to aspect 4, wherein the thermocouple is communicatively coupled to a heater control device, and wherein the heater control device controls the temperature of the heated vacuum table. 
     6. A system according to any one of aspects 1 to 5, further comprising a heat-insulating material disposed between the platform of the linear stage and the heated vacuum table. 
     7. A system according to any one of aspects 1 to 6, wherein the linear stage has a resolution of 0.05 μm or less. 
     8. A system according to any one of aspects 1 to 7, wherein the system is configured to maintain the working face of the heated vacuum table at a temperature between 80° C. and 110° C. 
     9. A system according to any one of aspects 1 to 7, wherein the system is configured to maintain the working face of the heated vacuum table at a temperature between 80° C. and 90° C. 
     10. A system according to any one of aspects 1 to 7, wherein the system is configured to maintain the working face of the heated vacuum table at a temperature between 80° C. and 100° C. 
     11. A system according to any one of aspects 1 to 10, wherein the plurality of channels formed in the working face of the heated vacuum table comprise two sets of channels, each set comprising a plurality of parallel channels, the channels of each set being perpendicular to the channels of the other set, and both sets of channels being parallel to the working face of the heated vacuum table. 
     12. A system according to any one of aspects 1 to 11, wherein the sheet of perforated heat-conductive material comprises a rigid material. 
     13. A system according to any one of aspects 1 to 12, wherein the sheet of perforated heat-conductive material is formed of stainless steel. 
     14. A system according to any one of aspects 1 to 13, wherein the heat-conductive wire mesh is formed of stainless steel. 
     15. A system according to any one of aspects 1 to 14, wherein the nanopipette or micropipette has a tip with an aperture selected to be proportional to a size of one or more particles suspended in the ink. 
     16. A system according to any one of aspects 1 to 15, further comprising a second layer of wire mesh disposed between the heat-conductive wire mesh and the sheet of perforated heat-conductive material. 
     17. A method for creating a catalyst coated membrane electrode, the method comprising: placing a membrane material onto a heated vacuum table assembly; positioning a nanopipette or micropipette adjacent to the membrane material; coupling the nanopipette or micropipette to a source of electrode ink, the electrode ink comprising a solvent, a catalyst, and an ionomer; operating a pump coupled to the nanopipette or micropipette and to the source of electrode ink to cause the electrode ink to be dispensed from the nanopipette or micropipette; and moving the heated vacuum table assembly relative to the nanopipette or micropipette to cause the electrode ink to be deposited onto the membrane material in a pattern defined by the movement of the heated vacuum table. 
     18. A method according to aspect 17, wherein the heated vacuum table assembly comprises: a linear stage having a platform and a base, the platform movable along X and Y axes according to electronic signals received from a controller device communicatively coupled to the linear stage; a heated vacuum table physically coupled to the platform of the linear stage and having a working face parallel to both the X and Y axes, the working face having formed therein a plurality of channels in fluid communication with a vacuum port formed in the vacuum table, the vacuum port configured to be coupled to a vacuum source; a sheet of perforated heat-conductive material sized to fit on the working face of the vacuum table, the sheet having a table-facing side placed against the working face of the vacuum table and a mesh-facing side, and having staggered holes configured to evenly distribute the vacuum pressure from the plurality of channels to the mesh side of the sheet; and a heat-conductive wire mesh having a sheet-facing side placed against the mesh-facing side of the sheet and a working side, the wire mesh having openings smaller than the staggered holes such that the membrane material placed on the working side of the wire mesh is not deformed by the vacuum pressure. 
     19. A method according to aspect 18, wherein the heated vacuum table comprises: a plurality of heating elements disposed each disposed in a corresponding aperture in the heated vacuum table, the plurality of heating elements configured to evenly distribute heat across the working face of the vacuum table; and a thermocouple configured to detect a temperature of the working face of the heated vacuum table. 
     20. A method according to either aspect 18 or aspect 19, wherein the plurality of channels formed in the working face of the heated vacuum table comprise two sets of channels, each set comprising a plurality of parallel channels, the channels of each set being perpendicular to the channels of the other set, and both sets of channels being parallel to the working face of the heated vacuum table. 
     21. A method according to any one of aspects 17 to 20, wherein the membrane material is sized such that vacuum is created between the heated vacuum table assembly and the membrane material. 
     22. A method according to any one of aspects 17 to aspect 20, wherein the membrane material cooperates with another material to create vacuum between the heated vacuum table assembly and the membrane material when the size of the membrane material alone is too small to create vacuum between the heated vacuum table assembly and the membrane material. 
     23. A method according to any one of aspects 17 to 22, further comprising heating the heated vacuum table assembly to a temperature that causes the solvent in the electrode ink to evaporate without damaging the membrane material. 
     24. A method according to any one of aspects 17 to 23, wherein the pump is a peristaltic pump. 
     25. A method according to any one of aspects 17 to 24, further comprising creating a plurality of discrete electrodes on the membrane material. 
     26. A method according to aspect 25, wherein each of the plurality of discrete electrodes comprises a different ink composition. 
     27. A method according to any one of aspects 17 to 26, wherein: positioning the nanopipette or micropipette adjacent to the membrane material comprises positioning a plurality of nanopipettes or micropipettes adjacent to the membrane material, coupling the nanopipette or micropipette to a source of electrode ink comprises coupling each of the plurality of nanopipettes or micropipettes to a corresponding source of electrode ink, operating the pump causes each of the nanopipettes or micropipettes to dispense electrode ink from its corresponding source of electrode ink, and the method causes a plurality of electrodes to be created simultaneously. 
     28. A method according to aspect 27, wherein: each of the corresponding sources of electrode ink contains an electrode ink having a different composition from the others, and the plurality of electrodes created simultaneously have different properties from one another. 
     29. A method according to either aspect 27 or 28, wherein positioning the plurality of nanopipettes or micropipettes adjacent to the membrane material comprises positioning the plurality of nanopipettes or micropipettes such that the created electrodes are positioned to cooperate with an electrode testing apparatus to test properties of each of the created electrodes.