Patent Description:
<CIT>) discloses various systems and methods relating to two-dimensional materials such as graphene. A membrane includes a cross-linked graphene platelet polymer that includes a plurality of cross-linked graphene platelets. The cross-linked graphene platelets include a graphene portion and a cross-linking portion. The cross-linking portion contains a <NUM> to <NUM> atom link. The cross-linked graphene platelet polymer is produced by reaction of an epoxide functionalized graphene platelet and a (meth)acrylate or (meth)acrylamide functionalized cross-linker.

<NPL>) provides a review of membranes prepared from graphene based nanomaterials, summarizes the state-of-the-art, and provides a survey of the theoretical and experimental approaches using graphene-based nanomaterials to construct new membranes and modify existing membranes.

<CIT>) discloses a method for producing a water permeable molecular sieve in which a porous substrate having micron-size pores has deposited on a surface thereof non-porous 2D platelets to seal, at the substrate surface, pores in the porous substrate to form a layer of 2D platelets. A curable sealing material is deposited onto the layer of 2D platelets and any remaining exposed areas of the surface of the porous substrate and curing the curable sealing material in order to form a sealed layer on the surface of the porous substrate to prevent water by-passing the non-porous 2D platelets and passing through the porous substrate. An array of sub-nanopores are then produced through the sealed layer with the array of sub-nanopores having a size to allow water to pass therethrough but not metal ions to give a water permeable molecular sieve characterized by water permeability at low differential pressures.

International Patent Application Publication No. <CIT>) discloses methods for forming a membrane. In one embodiment, the method includes: dispersing GO nanoparticles in a solvent; depositing the GO nanoparticles on a support to form a GO membrane; and reducing the GO membrane to form a rGO membrane. Also provided is the rGO membrane formed from such methods, along with a plurality of stacked rGO layers. Methods are also provided for separating water from a water/oil emulsion by, for example, passing water through the rGO membrane.

<CIT>) discloses technologies for composite membranes which may include a porous graphene layer in contact with a porous support substrate. In various examples, a surface of the porous support substrate may include at least one of: a thermo-formed polymer characterized by a glass transition temperature, a woven fibrous membrane, and/or a nonwoven fibrous membrane. Examples of the composite membranes permit the use of highly porous woven or nonwoven fibrous support membranes instead of intermediate porous membrane supports. In several examples, the composite membranes may include porous graphene layers directly laminated onto the fibrous membranes via the thermo-formed polymers. The described composite membranes may be useful for separations, for example, of gases, liquids and solutions.

The following summary is intended to introduce the reader to various aspects of the detailed description, but not to define or delimit any invention.

Apparatuses for fabricating graphene membranes are disclosed. According to some aspects, an apparatus for fabricating a graphene membrane, comprises:.

In some examples, the porous support includes a first layer having pores of a first size, a second layer having pores of a second size larger than the first size, and a third layer having pores of a third size larger than the second size. The first layer can include a sheet of at least one of cellulose, a fabric, and a polymer. The second layer can include a first sub-layer of a sintered polymer or a porous metal, and a second sub-layer of a sintered polymer or a porous metal.

In some examples, the pressurizer is connected to the first section and creates the pressure differential between the first fluid chamber and the second fluid chamber by pressurizing the first fluid chamber while the second fluid chamber remains at atmospheric pressure. The pressurizer can include a hydraulic cylinder, a compressed air cylinder, or a high-pressure water pump.

In some examples, the pressurizer includes a vacuum apparatus for creating a vacuum in the second fluid chamber.

In some examples, the apparatus further includes an ultrasonic transducer in the first fluid chamber.

In some examples, the apparatus further includes a substrate support frame having a first piece and a second piece. The porous substrate can be securable between the first piece and the second piece. The substrate support frame can be maneuverable to position the porous substrate on the porous support.

In some examples, when the first section, the substrate support frame is outboard of the first fluid chamber and the second fluid chamber.

In some examples, the apparatus further includes at least one sensor for sensing a parameter of the suspension, and/or the fluid, and/or the graphene platelets.

Methods for fabricating graphene membranes are also disclosed. According to some aspects, a method for fabricating a graphene membrane includes a) positioning a porous substrate across a porous support. The porous substrate has a first surface and a second surface, and the porous substrate is positioned so that the first surface faces away from the porous support and the second surface faces towards the porous support. The method further includes b) sandwiching the porous substrate between a first outer wall of a first section and a second outer wall of a second section, with the first outer wall bearing against the second outer wall via the porous substrate; c) applying a suspension of graphene platelets in a fluid to a first fluid chamber of the first section, to contact the first surface of the porous substrate with the suspension; and d) applying a pressure differential across the porous substrate to force the graphene platelets into the pores of the porous substrate and force the fluid through the porous substrate into the second section.

In some examples, step d) includes pressurizing the first fluid chamber. In some examples, step d) includes applying a vacuum to the porous support.

In some examples, the method includes sonicating the suspension during step c) and/or step d).

In some examples, the method further includes, prior to step a), mounting the porous substrate in a substrate support frame. Step a) can include maneuvering the substrate support frame to position the porous substrate across the porous support. The method can further include, after step d), removing the substrate support frame and the porous substrate from the porous support.

In some examples, the method further includes, during step d), sensing a parameter of the suspension and/or the fluid.

In some examples, step d) includes passing the fluid through a first layer, a second layer, and a third layer of the porous support.

Systems for fabricating graphene membranes are also disclosed. According to some aspects, a system for fabricating a graphene membrane includes an apparatus and a control sub-system. The apparatus comprises (i) a first section having a first outer wall and a first fluid chamber for housing a suspension of graphene platelets in a fluid, (ii) a second section having a second outer wall, a second fluid chamber, and a porous support housed in the second fluid chamber for supporting a porous substrate, wherein the first section is positioned to sandwich a porous substrate between the first section and the second section with the first outer wall bearing against the second outer wall via the porous substrate and with the porous substrate supported by the porous support, to place the first fluid chamber and the second fluid chamber are in fluid communication via the porous substrate, (iii) at least one sensor for sensing a parameter of the suspension and/or the fluid, and (iv) a pressurizer for creating a pressure differential between the first fluid chamber and the second fluid chamber and thereby forcing the fluid through the porous substrate and into the second fluid chamber and lodging the graphene platelets in the pores of the porous substrate to yield a graphene membrane that comprises the porous substrate with the graphene platelets lodged in the pores of the porous substrate. The control sub-system receives information from the sensor and controls the apparatus based on the received information, wherein the information comprises a pressure differential across the porous substrate, a concentration of ions in the suspension, a conductivity of the suspension, a flow rate across the porous substrate, and/or a conductivity of the porous substrate, and wherein the control sub-system controls the pressure differential induced by the pressurizer, and/or the entry of the suspension into the first section.

The drawings included herewith are for illustrating various examples of articles, methods, and apparatuses of the present specification and are not intended to limit the scope of what is taught in any way. In the drawings:.

Various apparatuses or processes or compositions will be described below to provide an example of an embodiment of the claimed subject matter. No embodiment described below limits any claim and any claim may cover processes or apparatuses or compositions that differ from those described below. The claims are not limited to apparatuses or processes or compositions having all of the features of any one apparatus or process or composition described below or to features common to multiple or all of the apparatuses or processes or compositions described below. It is possible that an apparatus or process or composition described below is not an embodiment of any exclusive right granted by issuance of this patent application. Any subject matter described below and for which an exclusive right is not granted by issuance of this patent application may be the subject matter of another protective instrument, for example, a continuing patent application, and the applicants, inventors or owners do not intend to abandon, disclaim or dedicate to the public any such subject matter by its disclosure in this document.

Generally disclosed herein are apparatuses, methods, and systems for fabricating graphene membranes. More specifically, disclosed herein apparatuses, methods, and systems for fabricating graphene membranes, where the graphene membranes include a porous substrate, and graphene platelets lodged in the pores of the porous substrate and/or deposited as a layer on the surface(s) of the porous substrate. Such graphene membranes are disclosed, for example, in international patent application (<CIT>), <CIT>), and <CIT>), each of which is incorporated herein by reference in its entirety. Such graphene membranes may be used, for example, in water filtration and purification, or to form conductive surfaces (e.g. for use in batteries).

In general, the apparatuses disclosed herein can allow for a suspension of graphene platelets in a fluid to be applied to a porous substrate, and for a pressure differential to be created across the porous substrate, so that the suspension is forced into the pores of the porous substrate. The fluid can pass through the pores, while the graphene platelets are trapped in the pores, to create the membrane (i.e. where the membrane includes the porous substrate and the graphene platelets lodged in the pores of the porous substrate and/or deposited as a layer on the surface(s) of the porous substrate).

As used herein, the term "platelet" refers to a structure that includes one or multiple (e.g. at least two and up to nine) sheets of graphene. Preferably, platelets include two, or three sheets of graphene. A platelet can be, for example, up to <NUM> nanometers thick, with a diameter of up to <NUM> microns. As used herein, the term 'graphene platelet' can refer to a platelet of pure graphene (i.e. non-functionalized graphene) and/or a platelet of functionalized graphene. Functionalized graphene can include, for example, hydroxylated graphene (also referred to as graphene oxide), aminated graphene, and/or hydrogenated graphene. Functionalization of the graphene can create pores in the graphene, which can allow for flow of filtrates, and can create a desired spacing between graphene sheets. For example, in platelets of non-functionalized graphene, the interlayer spacing may be approximately <NUM>. In platelets of functionalized graphene, e.g. graphene that is functionalized as hydroxylated graphene (also known as graphene oxide), the interlayer spacing may be approximately <NUM>.

As used herein, the term "porous substrate" refers to a sheet-like material having pores extending therethrough, from a first surface thereof to a second surface thereof. The pores can have a diameter of, for example, less than or equal to <NUM> microns. Preferably, the pores are at most <NUM> times larger in diameter than the diameter of the graphene platelets. The substrate can have a thickness (i.e. between the first surface and the second surface) of, for example, less than <NUM>. In some examples the substrate is a polymer, such as but not limited to polytetrafluoroethylene (Teflon®), polysulfone (PsF) (also referred to as polyether sulfone), cellulose, and/or polyester. In some examples, the substrate is an acid-treated polymer, for example polysulfone treated with sulfuric acid. In some examples, the substrate is an acid-treated and ion-treated polymer, for example polysulfone may be treated with sulfuric acid and then with a solution of metal ions (e.g. aluminum or calcium ions). In some examples, the substrate is non-polymeric, such as a woven cotton.

A first example of an apparatus for fabricating a graphene membrane will now be described. Referring to <FIG>, the apparatus <NUM> generally includes a first section <NUM>, a second section <NUM>, a pressurizer <NUM>, and a substrate support frame <NUM>. In the example shown, the first section <NUM> is an upper section, and the second section <NUM> is a lower section; however, in alternative examples, the first <NUM> and second <NUM> sections may be otherwise positioned (e.g. as a left-side section and a right-side section).

Referring also to <FIG>, in use, a porous substrate <NUM> (which ultimately becomes part of the graphene membrane) is supported by the substrate support frame <NUM>. The substrate support frame <NUM> has a first piece <NUM> and a second piece <NUM>, between which the porous substrate <NUM> is securable (e.g. using bolts). The substrate support frame <NUM> can be used to ease handling of the porous substrate <NUM> and to prevent or minimize physical damage to the porous substrate <NUM>. The substrate support frame <NUM> generally holds the porous substrate <NUM> flat (i.e. it can prevent bending, folding, and/or crimping).

Referring back to <FIG>, in use, the substrate support frame <NUM> can facilitate positioning of the porous substrate <NUM> between the first section <NUM> and the second section <NUM>, so that the porous substrate <NUM> is sandwiched between the first section <NUM> and the second section <NUM>, with a first surface <NUM> of the porous substrate <NUM> facing towards the first section <NUM> and away from the second section <NUM>, and a second surface <NUM> (shown in <FIG>) of the porous substrate <NUM> facing towards the second section <NUM> and away from the first section <NUM>.

Referring now to <FIG>, the first section <NUM> includes an outer wall <NUM> (also referred to herein as a "first outer wall") that defines a fluid chamber <NUM> (also referred to herein as a "first fluid chamber"). In use, as will be described in further detail below, the fluid chamber <NUM> houses a suspension of graphene platelets in a fluid.

In the example shown, the first section <NUM> includes a pair of fluid inlet ports <NUM> and an air escape port <NUM>. In alternative examples, the first section <NUM> may include another number of fluid inlet ports, such as one fluid inlet port, and the fluid inlet ports may be in another position. The fluid inlet ports <NUM> may be opened and closed by a valve (not shown). Furthermore, the first section <NUM> may include another number of air escape ports, such as more than one air escape port, and the air escape port may be in another position. The air escape port <NUM> may be opened and closed by a valve (not shown).

The first section <NUM> can further include an ultrasonic transducer (not shown) for sonicating the suspension of graphene platelets, which can help to pack the graphene platelets into the pores of the porous substrate <NUM> (as described in further detail below).

Referring still to <FIG>, the second section <NUM> includes an outer wall <NUM> (also referred to herein as a "second outer wall") that defines a fluid chamber (also referred to herein as a "second fluid chamber"). The second fluid chamber is not visible in the figures, as it is filled with a porous support <NUM>, described below. In use, the second section <NUM> is positionable adjacent to the first section <NUM> so that the first outer wall <NUM> bears against the second outer wall <NUM>, via the porous substrate <NUM>. The second section <NUM> can further be secured to the first section <NUM>, for example by clamping or bolting the first outer wall <NUM> to the second outer wall <NUM>.

Referring still to <FIG>, the second fluid chamber has a drain port <NUM>. In alternative examples, additional drain ports can be provided (e.g. four drain ports).

Referring still to <FIG>, the second section <NUM> further includes a porous support <NUM>, which is housed within the second fluid chamber. In use, during fabrication of a graphene membrane, the porous support <NUM> supports the porous substrate <NUM> of the graphene membrane, so that when a pressure differential is applied across the porous substrate <NUM>, the porous substrate does not tear or rip or break or stretch or otherwise incur damage. Furthermore, in use, when the first section <NUM> is positioned adjacent the second section <NUM> and the porous substrate <NUM> is supported by the porous support <NUM>, the first fluid chamber <NUM> and the second fluid chamber are in fluid communication via the porous substrate <NUM>;.

In the example shown, the porous support <NUM> includes several layers, namely a first layer <NUM>, a second layer <NUM>, and a third layer <NUM>. Each layer is porous, with the pore sizes larger than those of the porous substrate <NUM>, and becoming larger going from the first layer <NUM> layer to the third layer <NUM>. For example, the first layer <NUM> may have pore sizes on the scale of microns, the second layer <NUM> may have pore sizes on the scale of millimeters, and the third layer <NUM> may have pore sizes on the scale of inches.

In some examples, the first layer <NUM> includes a sheet of, for example, cellulose, fabric, and/or various polymers or other materials. In some examples, the first layer <NUM> includes more than one sheet of material. The first layer <NUM> can be in contact with and physically support the porous substrate <NUM> during fabrication of the graphene membrane.

In the example shown, the second layer <NUM> includes two sub-layers: a first sub-layer <NUM> and a second sub-layer <NUM>. The first sub layer <NUM> and second sub-layer <NUM> can include, for example, porous materials such as sintered polymers, sintered metals, zeolites, and/or ceramics. In some particular examples, the first sub-layer <NUM> and second sub-layer <NUM> each include a plexiglass sheet with holes drilled therethrough, with the holes of the first sub-layer <NUM> being smaller than the holes of the second sub-layer <NUM>. In use, the second layer <NUM> can contact and physically support the first layer <NUM>, distribute forces caused by the pressure differential (described in more detail below), and direct fluid away from the porous substrate <NUM> (i.e. downwardly, in the example shown).

In the example shown, the third layer <NUM> generally serves to drain the second layer <NUM>, and can be made from various materials having large pores, such as drilled plexiglass.

Referring still to <FIG>, the pressurizer <NUM> can be any device or apparatus or assembly that in use, can create a pressure differential between the first section <NUM> and the second section <NUM> (i.e. between the first fluid chamber <NUM> and the second fluid chamber, across the porous substrate <NUM>), to force the fluid of the suspension through the porous substrate <NUM> and into second fluid chamber and lodge the graphene platelets in the pores of the porous substrate <NUM>. In the example shown, the pressurizer <NUM> is a hydraulic cylinder (shown schematically) that is connected to the first section <NUM>, for pressurizing the fluid chamber <NUM> of the first section <NUM>, while the second fluid chamber remains at atmospheric pressure (or below atmospheric pressure, e.g. using a vacuum apparatus). In alternative examples the pressurizer can be, for example, a compressed air cylinder, or a mechanical screw, or a high-pressure water pump, or a compressor. Alternatively, the pressurizer can be a vacuum apparatus and can create a vacuum in the second fluid chamber, while the first fluid chamber <NUM> remains at atmospheric pressure (or above atmospheric pressure). While in the example shown, the hydraulic cylinder moves vertically to pressurize the first fluid chamber <NUM>, in alternative examples, a hydraulic cylinder can move horizontally.

Referring back to <FIG>, in the example shown, the apparatus <NUM> is part of a system that includes a control sub-system <NUM>. The control sub-system <NUM> can receive information from the apparatus <NUM> and/or can control the apparatus <NUM>. For example, the apparatus <NUM> can include various sensors, such as pressure sensors and/or pH sensors and/or conductivity sensors and/or flow sensors. The control sub-system <NUM> can receive information from the sensors. Such information can relate, for example, to the pressure differential across the porous substrate <NUM>, a concentration of ions in a suspension within the first fluid chamber <NUM> and/or second fluid chamber, a conductivity of the suspension within the first fluid chamber <NUM> and/or second fluid chamber, a flow rate across the porous substrate <NUM>, and/or a conductivity of the porous substrate <NUM>. Furthermore, the control sub-system <NUM> can control the apparatus <NUM> based on the received information. For example, the control sub-system <NUM> can control the pressure differential induced by the pressurizer <NUM>, and/or the entry of fluid into the upper fluid chamber based on the information. In the example shown, a sensor is shown schematically at <NUM> in <FIG>.

A method of fabricating a graphene membrane will now be described. The method will be described with reference to the apparatus <NUM>; however, the method is not limited to the apparatus <NUM>, and the apparatus <NUM> is not limited to operation by the method. In general, the method can include a) positioning the porous substrate <NUM> across the porous support <NUM> so that the first surface <NUM> faces away from the porous support <NUM> and the second surface <NUM> faces towards the porous support <NUM>; b) applying a suspension of graphene platelets in a fluid to the fluid chamber <NUM> of the first section <NUM>, to contact the first surface <NUM> of the porous substrate <NUM> with the suspension; and c) applying a pressure differential across the porous substrate <NUM> to force the graphene platelets into the pores of the porous substrate <NUM> and force the fluid through the porous substrate <NUM>.

More specifically, in use, the porous substrate <NUM> may first be mounted in the substrate support frame <NUM>, by securing the porous substrate <NUM> between the first <NUM> and second <NUM> pieces of the substrate support frame <NUM>, as shown in <FIG>. The apparatus <NUM> may then be assembled as shown in <FIG>, with the substrate support frame positioned <NUM> outboard of the first fluid chamber <NUM> and the second fluid chamber, and with the porous substrate <NUM> sandwiched between the first outer wall <NUM> and the second outer wall <NUM> and supported by the porous support <NUM>. This can be achieved by opening the apparatus <NUM> (i.e. separating the first section <NUM> and second section <NUM>), maneuvering the substrate support frame <NUM> to lay the porous substrate <NUM> on the second section <NUM>, closing the apparatus <NUM> (positioning the first section <NUM> adjacent the second section <NUM>), and securing the first section <NUM> to the second section <NUM>.

A suspension of graphene platelets in a fluid can then be applied to the first fluid chamber <NUM>, so that the suspension is in contact with the first surface <NUM> of the porous substrate <NUM>. For example, the suspension can be loaded into the first fluid chamber <NUM> via one of the fluid inlet ports <NUM>.

A mentioned above, the suspension includes graphene platelets suspended in a fluid. The fluid can be, for example, a liquid or a gas. For example, the fluid can be or can include a liquid such as water, an alcohol, and/or an organic solvent (e.g. N-Methyl-<NUM>-pyrrolidone (NMP)). Alternatively, the fluid can be or can include a gas such as nitrogen gas, carbon dioxide, noble gases, water vapor, and/or hydrogen gas. In addition to the graphene platelets, various other materials can be suspended in or dissolved in the fluid. The additional materials can be micro- or nano- sized. For example, the suspension can include carbons (e.g. graphite and/or carbon nanotubes), ceramics (such as oxides, carbides, carbonates, and/or phosphates), metals (such as aluminum and/or iron), semiconductors, lipids, and/or polymers.

A pressure differential can then be applied across the porous substrate <NUM>. As mentioned above, this can be achieved by pressurizing the first fluid chamber <NUM> and/or applying a vacuum to the second fluid chamber. In the example shown, the pressurizer <NUM> pressurizes the first fluid chamber <NUM>. Referring to <FIG>, as the pressure differential is applied, the suspension will be forced towards the second section <NUM>. Particularly, as the pressure differential is applied, the fluid <NUM> (shown schematically) of the suspension will pass through the pores <NUM> of the porous substrate <NUM>, while the graphene platelets <NUM> will become lodged within the pores <NUM>, leaving behind a graphene membrane (i.e. a membrane that includes the porous substrate <NUM> with the graphene platelets <NUM> lodged within the pores <NUM> and/or on the first surface <NUM> of the porous substrate). Optionally, while the pressure differential is being applied, the suspension can be sonicated, in order to facilitate tight packing of the graphene platelets <NUM> within the pores <NUM>.

After passing through the pores <NUM>, the fluid <NUM> will pass into the second section <NUM>, and through the first layer <NUM>, second layer <NUM>, and third layer <NUM> of the porous support <NUM>. The fluid can then be drained via the drain port <NUM>.

Optionally during pressurization, the control sub-system <NUM> can be used to receive information from the apparatus <NUM>, and/or to control the apparatus <NUM>.

Optionally, additional suspensions can be applied to the substrate. For example, a first suspension of a first type of graphene platelets (e.g. aminated graphene platelets) can be applied to the porous substrate <NUM>. Then, a second suspension of a second type of graphene platelets (e.g. oxidized graphene platelets) can be applied to the porous substrate. This can result in a graphene membrane that includes several sub-layers of graphene.

Upon completion of fabrication of the membrane (e.g. when all of the fluid <NUM> of the suspension has passed from the first fluid chamber <NUM> into the second fluid chamber), the apparatus <NUM> can be disassembled (i.e. by separating the first section <NUM> and the second section <NUM>), and the substrate support frame <NUM> and the graphene membrane (which includes the porous substrate <NUM> with the graphene platelets <NUM> lodged within the pores <NUM> of the porous substrate <NUM> and/or deposited as a layer on the porous substrate <NUM>) can together be removed from the first section <NUM> and second section <NUM>. The membrane can then optionally be removed from the substrate support frame <NUM>, or can remain in the substrate support frame <NUM> for further processing steps.

In some examples, rather than loading the suspension into the first fluid chamber <NUM>, the suspension can be made in the first fluid chamber <NUM>. For example, the fluid and the graphene platelets can be added to the first fluid chamber <NUM> separately, and then combined in the first fluid chamber <NUM>.

While the above describes a batch process for fabricating a graphene membrane, the apparatus <NUM> may alternatively be operated in a semi-batch fashion that approximates or simulates continuous operation. For example, the porous substrate <NUM> and the substrate support frame <NUM> can move through the first section <NUM> and second section <NUM>, across the porous support <NUM>. Furthermore, several of the apparatuses <NUM> may be operated in parallel or in series. When operating in series, each subsequent apparatus <NUM> can be used to deposit additional graphene platelets <NUM> onto/into the porous substrate <NUM>, or to deposit additional materials onto/into the porous substrate <NUM>. For example, the first apparatus in a series can deposit aminated graphene platelets into/onto the porous substrate <NUM>, while the second apparatus in the series can deposit oxidized graphene platelets into/onto the porous substrate <NUM>.

Optionally, the various parts of the apparatus <NUM> can be configured for removal, replacement, and cleaning.

While the above description provides examples of one or more processes or apparatuses or compositions, it will be appreciated that other processes or apparatuses or compositions may be within the scope of the accompanying claims.

Claim 1:
An apparatus for fabricating a graphene membrane, comprising:
a first section having a first outer wall and a first fluid chamber for housing a suspension of graphene platelets in a fluid;
a second section having a second outer wall, a second fluid chamber, and a porous support housed in the second fluid chamber for supporting a porous substrate, wherein the first section is positioned to sandwich a porous substrate between the first section and the second section with the first outer wall bearing against the second outer wall via the porous substrate and with the porous substrate supported by the porous support, to place the first fluid chamber and the second fluid chamber in fluid communication via the porous substrate;
a pressurizer for creating a pressure differential between the first fluid chamber and the second fluid chamber and thereby forcing the fluid through the porous substrate and into the second fluid chamber and lodging the graphene platelets in the pores of the porous substrate to yield a graphene membrane that comprises the porous substrate with the graphene platelets lodged in the pores of the porous substrate.