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ALTERNATING CURRENT ELECTROSPRAY MANUFACTURING AND PRODUCTS THEREOF

20220048053 · 2022-02-17

    Inventors

    Cpc classification

    International classification

    Abstract

    Provided in certain embodiments herein are alternating current electrospray systems and processes for manufacturing depositions, such as thin layer depositions. In some embodiments, processes and systems provided herein are suitable for and configured to manufacture uniform depositions, such as having uniform thickness.

    Claims

    1.-41. (canceled)

    42. A system for manufacturing a film or coating, the system comprising: a. an electrospray nozzle comprising: i. a first conduit, the first conduit being enclosed along the length of the conduit by a wall having an interior surface and an exterior surface, the first conduit having a first inlet end and a first outlet end, and the first conduit having a first diameter; and ii. a second conduit, the second conduit being enclosed along the length of the conduit by a second wall having an interior surface, the second conduit having a second inlet end and a second outlet end, and the second conduit having a second diameter, the first and second conduit having a conduit overlap length, wherein at least a portion of the first conduit is positioned inside the second conduit, the exterior surface of the first wall and the interior surface of the second wall being separated by a conduit gap; b. a power supply configured to apply an alternating current (AC) voltage to the nozzle, thereby providing an electric field; c. a substrate configured to receive a deposition thereon; and d. a pressurized gas supply configured to provide a high velocity gas to the second inlet end, thereby providing a high velocity gas stream at the second outlet end, the high velocity gas stream having a velocity of at least 5 m/s.

    43. The system of claim 42, further comprising a fluid stock supply system fluidically connected to the first inlet end, wherein the fluid stock supply system is configured to provide a fluid stock to the first inlet end, thereby providing an electrostatically charged fluid stock at the first outlet end.

    44. The system of claim 43, wherein the system is configured to inject the electrostatically charged fluid stock into the high velocity gas stream, thereby providing a plume of the fluid stock at the second outlet end.

    45. The system of claim 44, wherein the system is configured to provide the plume of the fluid stock at the substrate, thereby providing the deposition to the substrate.

    46. The system of claim 43, wherein the fluid stock supply system is configured to provide the fluid stock to the first inlet end at a rate of from about 0.5 mL/min to about 20 mL/min.

    47. The system of claim 43, wherein the fluid stock supply system is configured to agitate the fluid stock prior to providing the fluid stock to the first inlet end.

    48. The process of claim 47, wherein the agitation comprises stirring and/or sonicating the fluid stock.

    49. The system of claim 42, wherein the deposition is a thin layer deposition.

    50. The system of claim 42, wherein the deposition is a non-fibrous deposition.

    51. The system of claim 42, wherein the first diameter of the first conduit is about 25 mm or more.

    52. The system of claim 42, wherein the second diameter of the second conduit is from more than about 5 mm to about 10 cm.

    53. The system of claim 42, wherein the ratio of the conduit overlap length to the first diameter is from about 1 to about 100.

    54. The system of claim 42, wherein the conduit gap has a gap size of about 0.5 mm or more.

    55. The system of claim 42, wherein the first outlet end of the first conduit protrudes beyond the second outlet end of the second conduit by a protrusion length of from about −0.5 mm to about 1.5 mm.

    56. The system of claim 42, wherein the power supply is configured to apply an AC voltage of from about 10 kV.sub.AC to about 30 kV.sub.AC to the nozzle.

    57. The system of claim 42, wherein the power supply is configured to apply an AC voltage having a frequency of from about 50 Hz to about 500 Hz.

    58. The system of claim 42, wherein the power supply comprises a generator, an amplifier, and a transformer.

    59. The system of claim 58, wherein the generator is a waveform generator.

    60. The system of claim 42, wherein the power supply is configured to apply the AC voltage to the wall of the first conduit, thereby providing an electric field at the first outlet.

    61. The system of claim 42, wherein the pressurized gas supply is configured to provide the high velocity gas to the second inlet end at a pressure of from about 15 psi to about 45 psi.

    Description

    BRIEF DESCRIPTION OF THE DRAWINGS

    [0037] FIG. 1 illustrates high speed imaging of electrospray of a fluid stock using non-gas controlled, direct current electrospray techniques and an exemplary gas controlled, alternating current voltage (V.sub.AC) electrospray technique provided herein.

    [0038] FIG. 2 illustrates exemplary nozzle configurations of gas controlled electrospray systems using both direct current processing and alternating current processing.

    [0039] FIG. 3 illustrates an exemplary gas controlled, alternating current (AC) voltage electrospray system provided herein.

    [0040] FIG. 4 illustrates an exemplary gas controlled, alternating current (AC) voltage electrospray lab scale system provided herein.

    [0041] FIG. 5 illustrates an exemplary silazane structure having a plurality of cyclic and chain structures.

    [0042] FIG. 6 illustrates an exemplary silsesquioxane cage structure.

    [0043] FIG. 7 illustrates an exemplary silsesquioxane opened cage structure.

    [0044] FIG. 8 illustrates exemplary electrospray nozzle apparatuses provided herein.

    [0045] FIG. 9 illustrates high speed imaging of exemplary systems and processes provided herein, with varying gas pressures/velocities.

    [0046] FIG. 10 illustrates exemplary monomeric units of a polysilazanes provided herein.

    [0047] FIG. 11 shows an exemplary illustration of a gas controlled, alternating current electrospray system provided herein compared to an exemplary illustration of a non-gas controlled, direct current electrospray system.

    [0048] FIG. 12 illustrates high speed imaging of exemplary systems and processes provided herein, with varying voltage (V.sub.AC) frequencies.

    [0049] FIG. 13 illustrates high speed imaging of exemplary systems and processes provided herein, with varying flow rates.

    DETAILED DESCRIPTION OF THE INVENTION

    [0050] Provided in certain embodiments herein are systems and processes for manufacturing depositions, and the like. In some instances, depositions provided herein are thin layer depositions, which are suitable for any number of applications. In various embodiments, the depositions are coatings (e.g., films) comprising a matrix material (e.g., polymer or ceramic) and optionally further comprising inclusions (e.g., nanostructured inclusions). In some embodiments, the inclusions are dispersed in and/or on the matrix. In other embodiments, depositions provided herein are coatings comprising a plurality of structures, such as nanostructures (e.g., the nanostructures forming the coating and being dispersed on a substrate). Also provided in some embodiments herein are articles of manufacture comprising a deposition (e.g., film) or coat, e.g., a thin-layered coat manufactured or capable of being manufactured according to the processes described herein. In certain embodiments, provided herein is a substrate comprising a coating or deposition described herein on the surface thereof.

    [0051] In some embodiments, provided herein is a process for producing a deposition (e.g., a thin layer deposition), the process comprising electrospraying a fluid stock with an alternating current (e.g., applying an alternating current voltage to an electrospray nozzle, such as provided herein). In specific embodiments, the fluid stock is electrosprayed with a gas (e.g., a controlled gas flow). In certain embodiments, the fluid and the gas are ejected from an electrospray nozzle in a similar direction. In some instances, the direction of ejection of the fluid stock and the gas from the electrospray nozzle is within about 30 degrees of one another, or, more preferably within about 15 degrees of one another (e.g., within about 10 degrees or within about 5 degrees of one another). In certain embodiments, the fluid stock and the gas are configured to be ejected from the nozzle in a coaxial configuration. In some instances, configurations and processes described herein allow for an enhanced driving force of electrospray, combining the driving forces of electric field gradient with high speed gas. In certain instances, configurations and processes described herein provided for several improvements in electrospray processing, including in the manufacture of depositions, such as described herein. In addition, in some instances, such configurations allow for process throughput up to tens or hundreds of times greater than simple electrospray manufacturing and allow for the electrospray of high viscosity and/or highly loaded fluids. Moreover, in some instances, such electrospray techniques and systems allow for the manufacture of highly uniform depositions and coatings. By contrast, other or conventional electrospray is not generally of commercial use in coatings applications because of, e.g., non-uniform deposition of drops and dispersion of fillers in droplets, especially for high loaded systems. In addition, in some instances, the throughput capabilities of other or conventional electrospray systems are not sufficient to be commercially useful in some applications.

    [0052] In some instances, electrospray (e.g., using a process and/or system provided herein) of the fluid stock results in the formation of a jet, which subsequently deforms into a plume comprising a plurality of droplets (collectively referred to herein so as to encompass, e.g., droplet solutions, droplet suspensions, and/or solid particles in an plume or aerosol). In certain instances, electrospray (e.g., using a process and/or system provided herein) of a fluid stock, such as provided herein results in the formation of a plume comprising a plurality of droplets (collectively referred to herein so as to encompass, e.g., droplet solutions, droplet suspensions, and/or solid particles in an electrospray plume). In some instances, the processes described herein results in the formation of small droplets (e.g., micro- and/or nano-scale droplets) having highly uniform size distributions (e.g., especially relative to standard electrospray techniques).

    [0053] FIG. 1 illustrates high speed imaging of electrospray of a fluid stock using non-gas controlled, direct current electrospray techniques 101 and an exemplary gas controlled, alternating current voltage (V.sub.AC) electrospray technique provided herein 100 (100 and 101 not to scale). As illustrated in FIG. 1, the “plume” of the non-gas controlled, direct current electrospray process near the nozzle 104 comprises much larger droplets 102 having a less uniform size distribution than the droplets 103 of the plume resulting near the nozzle 105 of the alternating current (AC) voltage (V.sub.AC) electrospray processes described herein. In some instances, smaller and more uniform droplet size provides improved uniformity of depositions. In some instances, depositions formed by non-gas controlled, direct current electrospray techniques provide depositions that are not uniform and comprise large particles, e.g., relative to the depositions formed by exemplary gas controlled, alternating current (AC) voltage (V.sub.AC) electrospray systems and processes described herein. FIG. 11 shows an exemplary illustration of a gas controlled, alternating current electrospray system provided herein 1100 and an exemplary illustration of a non-gas controlled, direct current electrospray system 1120 (nozzles 1100 and 1120 not necessarily to scale). In some instances, a non gas-controlled, direct current system results, upon spraying from a nozzle 1121, in the formation of large droplets 1122, which droplets are large and not well dispersed in the “plume” and irregular depositions 1123 on the collector 1124. This illustration is further demonstrated in FIG. 1 by the high speed imaging of spraying 101. By contrast, in some embodiments, gas-controlled, alternating current systems (and processes) provided herein provide electrospray using V.sub.AC of a fluid stock with a gas (illustrated by the downward arrows) 1101 (e.g., having a controlled flow, such as circumferentially configured with the dispensing of the fluid stock) from a nozzle 1102 (e.g., coaxially arranged, as illustrated in FIG. 11). In some embodiments, with the flow of air, the droplets 1103 proximal to the nozzle are smaller relative to non-gas controlled techniques (e.g., in some instances due to the controlled air flow at the nozzle end 1104), and even smaller still as the droplets 1105 move away from the nozzle toward the collector (droplets distal to the nozzle 1106 and/or proximal to a collector 1107). In some embodiments, such uniformity (e.g., uniformity of size, horizontal distribution, etc.) of dispersion of small droplets provides for a deposition 1108 having a greatly improved uniformity of thickness, dispersion of inclusions, etc. This illustration is further demonstrated in FIG. 1 by the high speed imaging of spraying 101.

    [0054] In certain instances, uniformity in the plume/aerosol allows for much greater control of deposition formation, such as thickness, thickness uniformity, compositional uniformity (e.g., in composites), and the like. In certain embodiments, films provided herein have an average thickness (d.sub.f) that is about 10 mm or less, such as about 5 mm or less, about 2 mm or less, or about 1 mm or less. In certain embodiments, such as wherein the film is utilized as coating, such as a transparent coating, the thickness of the film is about 500 micron (micrometer, μm) or less, such as about 250 micron or less, about 200 micron or less, about 100 micron or less, about or the like (e.g., down to about 50 nm, about 100 nm, about 250 nm, about 500 nm, about 1 micron, about 5 micron, about 10 micron, 25 micron, 50 micron, 100 micron, or the like, depending on the desired thickness). In some embodiments, the thickness of the film is controlled by limiting or lengthening the residence time of a collector surface opposite an active nozzle system (e.g., using batch or continuous (e.g., using a conveyor) system). In certain embodiments, the films provided herein have good thickness uniformity, such as wherein the thinnest portion of the film is >d.sub.f/10, >d.sub.f/5, >d.sub.f/4, >d.sub.f/3, >d.sub.f/2, or the like. In further or alternative embodiments, the thickest portion of the film is <10×d.sub.f, <5×d.sub.f, <3×d.sub.f, <2×d.sub.f, <1.5×d.sub.f, <1.2×d.sub.f, or the like. In preferred embodiments, the minimum thickness of the film is greater than 0.9 d.sub.f, (more preferably greater than 0.95 d.sub.f) and the maximum thickness of the film is less than 1.1 d.sub.f, (more preferably, less than 1.05 d.sub.f).

    [0055] In certain embodiments, a process provided herein comprises producing an electrostatically charged plume comprising a plurality of particles and/or droplets (e.g., an area or section of air comprising a plurality of particles and/or droplets dispersed therein). In specific embodiments, the plurality of particles and/or droplets are nanoscaled and/or microscaled particles and/or droplets. In more specific embodiments, the plurality of particles and/or droplets have an average diameter of about 100 microns or less, about 50 microns or less, less than 30 micron, about 20 microns or less, less than 15 micron, or about 10 microns or less. In still more specific embodiments, the plurality of particles and/or droplets have an average diameter of about 5 microns or less, e.g., about 1 micron or less. In certain embodiments, the size of the particles and/or droplets is highly uniform, with the standard deviation of the particle and/or droplet size being about 50% of the average size of the particles and/or droplets, or less (e.g., about 40% or less, about 30% or less, about 20% or less, about 10% or less, or the like) (e.g., at any given distance from the nozzle, e.g., about 10 cm or more, about 15 cm or more, about 20 cm or more, about 25 cm or more, from the nozzle).

    [0056] In some embodiments, the fluid stock, the jet, and/or the plume comprises a fluid (e.g., water) and an inclusion (e.g., solid particulates, metal and/or ceramic precursors, and/or polymer). In certain embodiments, compositions provided herein comprise a plurality of droplets, a jet, or a fluid stock comprising a fluid (e.g., water) and an inclusion. In various embodiments, individual droplets optionally one or more inclusion type and/or other additive (e.g., polymer). Further, some or all of the fluid of the droplets (of the plume) may be evaporated during the electrospray process (e.g., prior to deposition). In various embodiments, concentrations of inclusion materials in droplets described herein, or a composition comprising the same, are generally higher than the concentrations of such materials in the fluid stock, or even in the jet (where evaporation of the fluid begins). In certain embodiments, droplets or compositions comprising the droplets having inclusions concentrations of at least 1.5×, at least 2×, at least 3×, at least 5×, at least 10×, or the like (e.g., wherein the inclusions make up up to 70 wt. % or more, 80 wt. % or more, 90 wt. % or more, or even 100 wt. % of the droplets or composition/plume comprising the same) of the concentrations of the droplets or composition/plume comprising the same.

    [0057] In specific embodiments, the plume (e.g., particles and/or droplets thereof) comprise a polymer and/or a plurality of additive particles (e.g., nanoparticles). In certain embodiments, the plume (e.g., particles and/or droplets thereof) further comprises a liquid medium (e.g., wherein the liquid medium of a fluid stock is not completely evaporated). In some embodiments, a process or system provided herein allows for high throughput electrospraying (e.g., relative to other non-gas controlled electrospray techniques). In some instances, the controlled air flow allows for a increase rate and uniformity in dispersion and breaking up of the jet and the plume, allowing for increased fluid stock flow rates, while also increasing deposition uniformity.

    [0058] In some instances, use of alternating current configurations provided herein provides for high throughput of processes and systems provided herein (e.g., in some instances, allow for greater throughput (e.g., per nozzle) than other electrospray techniques, including gas controlled manufacturing using direct current systems). In certain embodiments, the fluid stock is provided to the first inlet at a rate of about 0.1 mL/min or more, e.g., about 0.1 mL/min to about 25 mL/min, about 0.3 mL/min or more (e.g., about 0.3 mL/min to about 1 mL/min), about 0.5 mL/min or more, about 1 mL/min or more, about to about 2.5 mL/min, or about 5 mL/min or more. In some instances, such configurations allow for formation of high quality, high performance films with good uniformity of deposition (e.g., of inclusions, such as nanoparticles) at very high rates, e.g., up to 3 to 20 times greater than using similar systems configured for DC. FIG. 2 illustrates exemplary nozzle configurations of gas controlled electrospray systems using both direct current processing 201 and alternating current processing 200. As illustrated in FIG. 2, it is possible, in some instances, to utilize much larger nozzle with the gas-controlled, alternating current (AC) voltage (V.sub.AC) systems and, thereby, increase process throughput. In addition, in some instances, it is possible to retain good uniformity and dispersion of and in layers and coatings prepared utilizing such high-throughput systems. In some instances, systems provided herein allow for a high production rate via formation of multiple droplets/jets at a single large nozzle (e.g., as described herein), without the need for a multiple nozzle system (e.g., a nozzle bank). FIG. 13 illustrates high speed imaging of an exemplary system and process provided herein configured to electrospray a fluid stock using gas controlled, alternating current electrospray techniques provided herein, using various flow rates (e.g., 0.3 mL/min (1300), 0.6 mL/min (1310), and 1.0 mL/min (1320)). FIG. 13 illustrates that good droplet formation is observed at high throughput rates. Further, in some instances, improved disruption of droplets is achieved with varying flow rate parameters. In some instances, variation of flow rate allows and/or facilitates precise control of the coating characteristics (e.g., coating thickness, droplet/particle sizes, throughput, etc.).

    [0059] In specific embodiments, an electrospray process described herein comprises providing a fluid stock to a first inlet of a first conduit of an electrospray nozzle, the first conduit being enclosed along the length of the conduit by a wall having an interior surface and an exterior surface, the first conduit having a first outlet. In specific instances, the walls of the first conduit form a capillary tube, or other structure. In some instances, the first conduit is cylindrical, but embodiments herein are not limited to such configurations.

    [0060] FIG. 8 illustrates exemplary electrospray nozzle apparatuses 800 and 830 provided herein. Illustrated by both nozzle components 800 and 830 some embodiments, the nozzle apparatus comprises a nozzle component comprising a first (inner) conduit, the first conduit being enclosed along the length of the conduit by a first wall 801 and 831 having an interior and an exterior surface, and the first conduit having a first inlet (or supply) end 802 and 832 (e.g., fluidly connected to a first supply chamber and configured to receive a fluid stock) and a first outlet end 803 and 833. Generally, the first conduit has a first diameter 804 and 834 (e.g., the average diameter as measured to the inner surface of the wall enclosing the conduit). In further instances, the nozzle component comprising a second (outer) conduit, the second conduit being enclosed along the length of the conduit by a second wall 805 and 835 having an interior and an exterior surface, and the second conduit having a second inlet (or supply) end 806 and 836 (e.g., fluidly connected to a second supply chamber and configured to receive a gas—such as a high velocity or pressurized gas (e.g., air)) and a second outlet end 807 and 837. In some instances, the second inlet (supply) end 806 and 836 is connected to a supply chamber. In certain instances, the second inlet (supply) end 806 and 836 are connected to the second supply chamber via a supply component. FIG. 8 illustrates an exemplary supply component comprising a connection supply component (e.g., tube) 813 and 843 that fluidly connects 814 and 844 the supply chamber (not shown) to an inlet supply component 815 and 845, which is fluidly connected to the inlet end of the conduit. The figure illustrates such a configuration for the outer conduit, but such a configuration is also contemplated for the inner and any intermediate conduits as well. Generally, the first conduit has a first diameter 808 and 838 (e.g., the average diameter as measured to the inner surface of the wall enclosing the conduit). The first and second conduits have any suitable shape. In some embodiments, the conduits are cylindrical (e.g., circular or elliptical), prismatic (e.g., a octagonal prism), conical (e.g., a truncated cone—e.g., as illustrated by the outer conduit 835) (e.g., circular or elliptical), pyramidal (e.g., a truncated pyramid, such as a truncated octagonal pyramid), or the like. In specific embodiments, the conduits are cylindrical (e.g., wherein the conduits and walls enclosing said conduits form needles). In some instances, the walls of a conduit are parallel, or within about 1 or 2 degrees of parallel (e.g., wherein the conduit forms a cylinder or prism). For example, the nozzle apparatus 800 comprise a first and second conduit having parallel walls 801 and 805 (e.g., parallel to the wall on the opposite side of the conduit, e.g., as illustrated by 801a/801b and 805a/805b, or to a central longitudinal axis 809). In other embodiments, the walls of a conduit are not parallel (e.g., wherein the diameter is wider at the inlet end than the outlet end, such as when the conduit forms a cone (e.g., truncated cone) or pyramid (e.g., truncated pyramid)). For example, the nozzle apparatus 830 comprise a first conduit having parallel walls 831 (e.g., parallel to the wall on the opposite side of the conduit, e.g., as illustrated by 831a/831b, or to a central longitudinal axis 839) and a second conduit having non-parallel walls 835 (e.g., not parallel or angled to the wall on the opposite side of the conduit, e.g., as illustrated by 835a/835b, or to a central longitudinal axis 839). In certain embodiments, the walls of a conduit are within about 15 degrees of parallel (e.g., as measured against the central longitudinal axis, or half of the angle between opposite sides of the wall), or within about 10 degrees of parallel. In specific embodiments, the walls of a conduit are within about 5 degrees of parallel (e.g., within about 3 degrees or 2 degrees of parallel). In some instances, conical or pyramidal conduits are utilized. In such embodiments, the diameters for conduits not having parallel walls refer to the average width or diameter of said conduit. In certain embodiments, the angle of the cone or pyramid is about 15 degrees or less (e.g., the average angle of the conduit sides/walls as measured against a central longitudinal axis or against the conduit side/wall opposite), or about 10 degrees or less. In specific embodiments, the angle of the cone or pyramid is about 5 degrees or less (e.g., about 3 degrees or less). Generally, the first conduit 801 and 831 and second conduit 805 and 835 having a conduit overlap length 810 and 840, wherein the first conduit is positioned inside the second conduit (for at least a portion of the length of the first and/or second conduit). In some instances, the exterior surface of the first wall and the interior surface of the second wall are separated by a conduit gap 811 and 841. In certain instances, the first outlet end protrudes beyond the second outlet end by a protrusion length 812 and 842. In certain instances, the ratio of the conduit overlap length-to-second diameter is any suitable amount, such as an amount described herein. In further or alternative instances, the ratio of the protrusion length-to-second diameter is any suitable amount, such as an amount described herein, e.g., about 1 or less.

    [0061] FIG. 8 also illustrates cross-sections of various nozzle components provided herein 850, 860 and 870. Each comprises a first conduit 851, 861 and 871 and second conduit 854, 864, and 874. As discussed herein, in some instances, the first conduit is enclosed along the length of the conduit by a first wall 852, 862 and 872 having an interior and an exterior surface and the second conduit is enclosed along the length of the conduit by a second wall 855, 865 and 875 having an interior and an exterior surface. Generally, the first conduit has any suitable first diameter 853, 863 and 864 and any suitable second diameter 856, 866, and 876. The cross-dimensional shape of the conduit is any suitable shape, and is optionally different at different points along the conduit. In some instances, the cross-sectional shape of the conduit is circular 851/854 and 871/874, elliptical, polygonal 861/864, or the like.

    [0062] In some instances, coaxially configured nozzles provided herein and coaxial gas controlled electrospraying provided herein comprises providing a first conduit or fluid stock along a first longitudinal axis, and providing a second conduit or gas (e.g., pressurized or high velocity gas) around a second longitudinal axis (e.g., and electrospraying the fluid stock in a process thereof). In specific embodiments, the first and second longitudinal axes are the same. In other embodiments, the first and second longitudinal axes are different. In certain embodiments, the first and second longitudinal axes are within 500 microns, within 100 microns, within 50 microns, or the like of each other. In some embodiments, the first and second longitudinal axes are aligned within 15 degrees, within 10 degrees, within 5 degrees, within 3 degrees, within 1 degree, or the like of each other. For example, FIG. 8 illustrates a cross section of a nozzle component 870 having an inner conduit 871 that is off-center (or does not share a central longitudinal axis) with an outer conduit 874. In some instances, the conduit gap (e.g., measurement between the outer surface of the inner wall and inner surface of the outer wall) is optionally averaged—e.g., determined by halving the difference between the diameter of the inner surface of the outer wall 876 and the diameter of the outer surface of the inner wall 872. In some instances, the smallest distance between the inner surface of the outer wall 876 and the diameter of the outer surface of the inner wall 872 is at least 10% (e.g., at least 25%, at least 50%, or any suitable percentage) of the largest distance between the inner surface of the outer wall 876 and the diameter of the outer surface of the inner wall 872.

    [0063] A fluid stock provided herein comprises any suitable components. In specific embodiments, the fluid stock comprises a liquid medium and an optional additive. In specific embodiments, the fluid stock comprises a liquid medium and at least one additive. In more specific embodiments, the additive is a polymer and/or a solid particulate inclusion (e.g., nanoscaled—such as less than about 2 micron in at least one dimension—particulate; e.g., nanoparticles being less than about 2 micron in all dimensions, and nanorods and nanofibers being less than about 2 micron in diameter and greater or less than about 2 micron in a second dimension). In specific embodiments, nano-inclusions (e.g., nanoparticles) have nanoscale morphologies that are about 1 micron or less, about 500 nm or less, about 250 nm or less, or about 100 nm or less. In more specific embodiments, at least one dimension (e.g., all dimensions for a nanoparticle) is about 50 nm or less, or about 25 nm or less or about 10 nm or less, or about 5 nm to about 10 nm, or any other suitable size. In further or additional embodiments, processes described herein are optionally utilized with larger particles, such as micro-sized particles having a (e.g., average) dimension of about 2 micron to about 200 micron, about 2 micron to about 100 micron, or the like. In various embodiments, the additives are dissolved and/or otherwise dispersed into the liquid medium. In additional embodiments, further additives are optionally included, as desired. For example, in some instances, an additive optionally includes a fluorinated organosilane (e.g., fluoroalkyl silane (e.g., F.sub.3C(CF.sub.2).sub.a(CH.sub.2).sub.bSi(OR).sub.3, wherein a is 0 to 12, e.g., 1-6, b is 0-12, e.g., 1-6, each R is independently a hydrocarbon described herein, such as a C1-6 alkyl), and/or flouropolyether alkoxy silane, such as a perfluoropolyetheralkoxy silane (e.g., F.sub.3C((CF.sub.2).sub.aO).sub.c(CH.sub.2).sub.bSi(OR).sub.3, wherein each a is independently 0 to 12, e.g., 1-2, b is 0-12, e.g., 1-3, c is 0-12, e.g., 1-6, each R is independently a hydrocarbon described herein, such as a C1-6 alkyl or fluoroalkyl), a metal, metal oxide, or ceramic precursor, and/or other suitable additives.

    [0064] Depending on the coating and/or deposition application, any number of polymers are optionally utilized. In some embodiments, polymers include, by way of non-limiting example, polyvinyl alcohol (PVA), polyvinyl acetate (PVAc), polyethylene oxide (PEO), polyvinyl ether, polyvinyl pyrrolidone, polyglycolic acid, hydroxyethylcellulose (HEC), ethylcellulose, cellulose ethers, polyacrylic acid, polyisocyanate, and the like. In some embodiments, the polymer is polystyrene (PS), polymethacrylate (PMA), polyvinylpyridine (PVP), polyvinylalkane, polyvinylcycloalkane (e.g., polyvinylcyclohexane), a polyimide, a polyamide, a polyalkene (e.g., polypropylene (PP)), a polyether (e.g., polyethyelene oxide (PEO), polypropylene oxide (PPO)), a polyamine, or the like. In specific embodiments, the polymer is polycarbonate (PC), poly(methyl methacrylate) (PMMA), polyethylene terephthalate (PET), polystyrene (PS), acrylonitrile butadiene styrene (ABS), polyacrylonitrile (PAN), polyvinyl alcohol (PVA), or polyvinylidene fluoride (PVDF). In certain embodiments, such as wherein a transparent coat is desired, a transparent polymer is utilized (e.g., a polymer that is transparent at a thickness of a deposition or coat applied (e.g., about 1 mm or less). In certain embodiments, a deposition or coat provided herein has a transmittance (e.g., at 300-800 nm) of about 85% or greater, about 90% of greater, or about 95% or greater. Moreover, in some instances, use of electrospinning techniques to deposit a similar coat of nanofibers onto the surface resulted in an unacceptably opaque coat, rendering the underlying objects “blurry” or not visible. In some embodiments, the polymer has any suitable molecular weight. For example, in certain embodiments, the polymer has a molecular weight of at least 5,000 atomic mass units (“amu”), at least 10,000 amu, at least 20,000 amu, at least 50,000 amu, at least 75,000 amu or the like. In certain instances, use of alternating current systems provided herein provide and/or facilitate improved capabilities of electrospraying polymer solutions having increased polymer molecular weights and/or polymer concentrations (e.g., relative to other electrospraying systems, including, e.g., similar systems using direct current electrospray techniques). A polymer in used in a process or found in a composition herein has any suitable PDI (weight average molecular weight divided by the number average molecular weight). In some embodiments, the polymer has a polydispersity index of about 1 to about 10, about 2 to about 5, about 1 to about 5, or the like.

    [0065] In certain embodiments, any suitable amount of polymer is optionally utilized in a fluid stock provided herein. In some instances, the amount of polymer utilized is less than the amount that would inhibit the formation of a plume (dispersion and/or breaking-up of the jet) when being electrosprayed. In some instances, with the use of the gas controlled electrospray processes, greater amounts of polymer are optionally utilized when compared to conventional electrospray techniques because of the effect of the gas to further break-up the jet and/or plume, providing greater formation, dispersion and control of droplets. In certain embodiments, the amount of polymer present in the fluid stock is less than 10 wt. %. In more specific embodiments, the amount of polymer present in the fluid stock is 0 wt. % to about 10 wt. % (e.g., about 0 wt. % to about 5 wt. %, about 0.1 wt. % to about 5 wt. %, or about 0.5 wt. % to about 5 wt. %). In some instances, polymer concentrations are optionally higher using alternating current systems, such as those described herein, than using other or similar direct current systems.

    [0066] In additional or alternative embodiments, the fluid stock comprises an additive, such as a non-polymer additive, a solid particle additive (e.g., dispersed in the fluid stock), or the like. In some instances, processes for preparing and systems configured to prepare depositions, such as those described herein, do not require the use of a polymer. For example, depositions comprising dispersed particles (e.g., nanostructured particles) are optionally prepared using a fluid stock with or without a polymer. In some instances, when a polymer is included in a fluid stock (e.g., along with a plurality of particles), a deposition comprising a polymer matrix with particles dispersed in and/or on the polymer matrix is formed (e.g., a polymer matrix deposition being formed on a substrate surface). In some other instances, when a fluid stock (comprising a plurality of particles) without a polymer is used, a deposition comprising particles dispersed directly on a substrate is formed.

    [0067] In some embodiments, the fluid stock and/or deposition comprise an additive, such as a plurality of solid inclusion particulates. In specific embodiments, the additive comprises a plurality of nano-structured particles. In various embodiments, nanostructured particles include, by way of non-limiting example, nanoparticles, nanoscale sheets, nanoribbons, nanorods, nanofibers (including, e.g., high aspect ratio nanorods), and the like. In certain embodiments, the additive comprises metal, ceramic, metal oxide, carbon (e.g., a carbon allotrope), and/or the like. In specific embodiments, the additive comprises metal particles (e.g., nanoparticles), ceramic particles (e.g., nanoparticles), metal oxide particles (e.g., nanoparticles), or a combination thereof. In further or alternative embodiments, the additive comprises a carbonaceous inclusion (e.g., carbon allotrope), such as, by way of non-limiting example, carbon nanotubes (e.g., multi-walled carbon nanotubes (MWCNT), and/or single-walled carbon nanotubes (SWCNT)), graphene (e.g., pristine or defective graphene, such as produced from by reducing, e.g., thermal or irradiation reduction of graphene oxide), graphene oxide, reduced graphene oxide, graphite, amorphous carbon, graphene nanoribbons (GNRs), or the like.

    [0068] In specific embodiments, an additive provided herein comprises a plurality of nanofibers, the nanofibers comprising a metal, metal oxide, ceramic, carbon (e.g., amorphous carbon) or a combination thereof. Such nanofibers are optionally manufactured by any suitable method, such as those described in WO 2013/033367, published on 7 Mar. 2013, and entitled “Metal and Ceramic Nanofibers,” which is incorporated herein by reference for such disclosure. In more specific embodiments, the nanofibers comprise a composite comprising a matrix material and an inclusion material, the inclusion material embedded in the matrix material. In certain embodiment, the matrix material is a metal, metal oxide, ceramic, carbon (e.g., amorphous carbon), polymer (e.g., a polymer described herein), or other suitable material. In some embodiments, the inclusion material is a metal, metal oxide, ceramic, carbon (e.g., amorphous carbon) or other suitable material. Such nanofibers are optionally manufactured by any suitable method, such as those described in WO 2014/043612, published on 20 Mar. 2014, and entitled “Carbonaceous Metal/Ceramic Nanofibers,” which is incorporated herein by reference for such disclosure. The nanofibers have any suitable length. In some instances, a given collection of nanofibers comprise nanofibers that have a distribution of fibers of various lengths. In some embodiments, the nanofiber has an average length of about 1 micron or more, or about 5 micron or more, or about 10 micron or more, or about 20 micron or more, or about 50 micron or more, or ever larger sizes, up to and including any size capable of being dispersed in a fluid stock and electrosprayed using a process described herein. In some embodiments, nanofibers described herein have an aspect ratio of about 10 or more. In more specific embodiments, the aspect ratio is about 20 or more, about 50 or more, about 100 or more, about or even larger. “Aspect ratio” is the length of a nanofiber divided by its diameter.

    [0069] In some embodiments, metal, metal oxide, or ceramic materials (e.g., solid inclusions, precursors, or the like) provided in a metal, metal oxide, or ceramic herein optionally comprise any suitable elemental components, such as a transition metal, alkali metal, alkaline earth metal, post-transition metal, lanthanide, or actinide. Transition metals include: scandium (Sc), titanium (Ti), vanadium (V), chromium (Cr), manganese (Mn), iron (Fe), cobalt (Co), nickel (Ni), copper (Cu), zinc (Zn), yttrium (Y), zirconium (Zr), niobium (Nb), molybdenum (Mo), technetium (Tc), ruthenium (Ru), rhodium (Rh), palladium (Pd), silver (Ag), cadmium (Cd), hafnium (Hf), tantalum (Ta), tungsten (W), rhenium (Re), osmium (Os), iridium (Ir), platinum (Pt), gold (Au), mercury (Hg), rutherfordium (Rf), dubnium (Db), seaborgium (Sg), bohrium (Bh), and hasium (Hs). Alkali metals include: lithium (Li), sodium (Na), potassium (K), rubidium (Rb), cesium (Cs) and francium (Fr). Alkaline earth metals include: beryllium (Be), magnesium (Mg), calcium (Ca), strontium (Sr), barium (Ba), and radium (Ra). Post-transition metals include: aluminum (Al), gallium (Ga), indium (In), tin (Sn), thallium (Tl), lead (Pb), and bismuth (Bi). Lanthanides include the elements with atomic number 57 to 71 on the periodic table. Actinides include the elements with atomic number 89 to 103 on the periodic table. In addition, silicon (Si), germanium (Ge), antimony (Sb) and polonium (Po) are considered metals for the purposes of the present disclosure. In some embodiments, silicon is used in the process described herein to produce silicon nanofibers. In some embodiments, metal oxides include, by way of non-limiting example, Al.sub.2O.sub.3, ZrO.sub.2, Fe.sub.2O.sub.3, CuO, NiO, ZnO, CdO, SiO.sub.2, TiO.sub.2, V.sub.2O.sub.5, VO.sub.2, Fe.sub.3O.sub.4, SnO, SnO.sub.2, CoO, CoO.sub.2, Co.sub.3O.sub.4, HfO.sub.2, BaTiO.sub.3, SrTiO.sub.3, and BaSrTiO.sub.3. Other additives, such as metal precursors, surfactants, or the like, are also optionally utilized. In such cases, upon calcination (e.g., thermal treatment of about 800° C. or more, e.g., about 1200° C. or more, about 1500° C. or more), the metal precursors may be converted to a metal or metal oxide material described herein. Metal precursors include metal iodides, bromides, sulfides, thiocyanates, chlorides, nitrates, azides, fluorides, hydroxides, oxalates, nitrites, isothiocyanates, cyanides, alko-oxides (e.g., methoxide, ethoxide, propoxide, butlyoxide, or the like), or the like. In some examples, the precursor is a metal complex such as metal acetate, metal chloride, metal nitrate, or metal alko-oxide.

    [0070] In specific embodiments, the additive and/or (e.g., nano-structured) particles comprise silicon, a silicon oxide (e.g., SiOx, wherein 0<x≤2), an aluminum oxide, or a titanium oxide (e.g., TiOx, wherein 0<x≤2).

    [0071] In specific embodiments, the additive comprises carbon nonstructures, such as carbon nanotubes, graphene nanoribbons, carbon nanofibers, mesoporous carbon nanostructures, or any combination thereof. In specific embodiments, an additive provided herein comprises a graphene component (e.g., graphene or a fully reduced graphene oxide), such as an oxidized graphene component (e.g., graphene oxide, reduced graphene oxide (that is still partially oxidized), or the like).

    [0072] In some embodiments, a film or coating provided herein comprises a carbon (e.g., graphene) matrix or web (e.g., wherein the graphene matrix or web comprises a graphene structure or analog as described herein). In certain embodiments, the carbon matrix or web comprises any suitable amount of a graphene component (e.g., graphene, graphene oxide, or reduced graphene oxide). In specific embodiments, the carbon matrix or web comprises about 25 wt. % or more (e.g., about 50 wt % or more, about 60 wt % or more, about 75 wt % or more, about 85 wt % or more, about 90 wt % or more, or about 95 wt % or more) graphene component. In certain embodiments, the film further comprises a plurality of structures (e.g., micro- or nano-structures, such as comprising metal, metal oxide, and/or ceramic material), such as provided from preformed inclusions provided in a fluid stock herein, or metal or ceramic precursor materials provided in the fluid stock. In certain embodiments, the inclusion materials are embedded within the carbon matrix or web (e.g., graphenic matrix or web), and/or on the surface thereof. In some embodiments, the inclusions comprise nanoscale and/or microscale inclusions (e.g., such nanostructures comprising a nanoscale (e.g., having an average dimension of less than 2 micron, or less than 1 micron) structure in any one or more dimension, such as nanostructured fibers, particles, sheets, rods, and/or the like). In specific embodiments, the carbon inclusion is a nanostructured carbon having a nanoscale (e.g., less than 2 micron, less than 1 micron, or less than 200 nm) structure in any one or more dimension, such as nanostructured fibers, particles, sheets (e.g., graphenic sheets), rods, and/or the like). In some embodiments, the inclusion comprises microstructures (e.g., having an average dimension of less than 100 micron, less than 50 micron, or less than 30 micron, less than 25 micron, less than 20 micron, less than 15 micron, less than 10 micron, or the like, such as down to about 200 nm, about 500 nm, about 1 micron, or the like). Other details of the suitable materials, inclusions, or structures are as described herein. Further, in some instances, such as wherein larger structures are utilized, larger droplets or particles are necessarily formed upon electrospray according to the processes described herein.

    [0073] In specific embodiments provided herein is a composition or material comprising a graphene component, such as an oxidized graphene component (e.g., graphene oxide). In certain embodiments, oxidized graphene components are converted to reduced materials via reductive reaction conditions, such as through thermal, irradiation, chemical, and/or other processes described herein. In specific embodiments, thermal conditions using reductive (e.g., hydrogen gas, hydrogen gas mixed with an inert gas, or the like) or inert atmosphere (e.g., nitrogen gas, argon gas, or the like) is utilized. In specific embodiments, the oxidized graphene component is a graphene component functionalized with oxygen, such as with carbonyl groups, carboxyl groups (e.g., carboxylic acid groups, carboxylate groups, COOR groups, such as wherein R is a C1-C6 alkyl, or the like), —OH groups, epoxide groups, ether, and/or the like. In certain embodiments, the oxidized graphene component (or graphene oxide) comprises about 60% or more carbon (e.g., 60% to 99%). In more specific embodiments, the oxidized graphene component comprises about 60 wt. % to about 90 wt. % carbon, or about 60 wt. % to about 80 wt. % carbon. In further or alternative specific embodiments, the oxidized graphene component comprises about 40 wt. % oxygen or less, such as about 10 wt. % oxygen to about 40 wt. % oxygen, about 35 wt. % oxygen or less, about 1 wt. % to 35 wt. % oxygen, or the like. In various instances, oxidized graphene included graphene oxide, such as illustrated by the non-limiting exemplary structures in FIG. 15, and/or reduced graphene oxide, such as illustrated by the non-limiting exemplary structures in FIG. 16.

    [0074] In certain embodiments, the graphene component (e.g., reduced graphene oxide) comprises about 60% or more carbon (e.g., 60% to 99%), such as about 70 wt. % or greater, about 75 wt. % or more, about 80 wt. % or greater, about 85 wt. % or greater, about 90 wt. % or greater, or about 95 wt. % or greater (e.g., up to about 99 wt. % or more). In certain embodiments, the graphene component (e.g., rGO) comprises about 35 wt. % or less (e.g., 0.1 wt. % to 35 wt. %) oxygen, e.g., about 25 wt. % or less (e.g., 0.1 wt. % to 25 wt. %) oxygen, or about, about 20 wt. % or less, about 15 wt. % or less, about 10 wt. % or less (e.g., down to about 0.01 wt. %, down to about 0.1 wt. %, down to about 1 wt. % or the like) oxygen. In specific embodiments, the graphene component (e.g., rGO) comprises about 0.1 wt. % to about 10 wt. % oxygen, e.g., about 4 wt. % to about 9 wt. %, about 5 wt, % to about 8 wt, %, or the like. In certain embodiments, e.g., wherein an oxidized carbon inclusion material (e.g., graphene component) is reduced, higher ratios of carbon to oxygen are contemplated for the graphene component.

    [0075] In some embodiments, processes described herein are useful for high throughput processing of graphenic components (e.g., oxidized graphene components) to form highly uniform films and coatings. In certain embodiments, higher concentrations of graphenic inclusion components are able to be processed than are possible using conventional techniques. In certain embodiments, a fluid stock provided herein comprises at least 0.5 wt. %, or at least 1 wt. % graphenic inclusion component, e.g., at least 2 wt. % graphenic inclusion component, at least 2.5 wt. % graphenic inclusion component, at least 3 wt. % inclusion component, at least 5 wt. % graphenic inclusion component, or the like (e.g., up to 15 wt. %, up to 10 wt. %, or the like). In certain embodiments, the fluid stock comprises about 2 wt. % to about 15 wt. % (e.g., about 10 wt. % to about 15 wt. %) graphenic inclusion component.

    [0076] The additive is present in a fluid stock provided herein in any concentration desired and up to which electrospraying according to a process or using a system described herein is possible. In some instance, electrospraying a fluid stock with a controlled gas steam, such as described in certain instances herein, allows for the electrospraying of fluid stocks comprising very high concentrations of polymer and/or additive. In some instances, the concentration of the additive in the fluid stock is up to about 70 wt. %. In specific embodiments, the concentration of the additive in the fluid stock is about 5 wt. % to about 50 wt. %.

    [0077] In certain embodiments, the liquid medium comprises any suitable solvent or suspending agent. In some embodiments, the liquid medium is merely utilized as a vehicle and is ultimately removed, e.g., by evaporation during the electrospraying process and/or upon drying of the deposition. In certain embodiments, the liquid medium comprises water, an alcohol (e.g., methanol, ethanol, isopropanol, propanol, butyl alcohol, or the like), dimethylformamide (DMF), tetrahydrofuran (THF), Di methyl acetamide (DMAc), N-methyl-pyrrolidone (NMP), or a combination thereof. In certain embodiments, the liquid medium comprises a liquid precursor material that is converted upon deposition to a desired material, such as a ceramic. In some specific embodiments, the liquid medium comprises polysilazane, a silsesquioxone (e.g., polyhedral oligomeric silsesquioxane (POSS), or polysilsesquioxane (PSSQ)), or a combination thereof—e.g., wherein a deposition comprising ceramic matrix is desired.

    [0078] In some embodiments, a polysilazane has a structure of general formula (I):


    —[SiR.sup.1R.sup.2—NR.sup.3].sub.n  (I)

    [0079] In some instances, the polysilazane has a chain, cyclic, crosslinked structure, or a mixture thereof. FIG. 5 illustrates an exemplary silazane structure having a plurality of units of Formula I with cyclic and chain structures. In various embodiments, the polysilzane comprises any suitable number of units, such as 2 to 10,000 units and/or n is any suitable value, such as an integer between 2 and 10,000. In certain embodiments, the polysilazane of formula I has an n value such that the 100 to 100,000, and preferably from 300 to 10,000. Additional units are optionally present where each R.sup.1 or R.sup.2 is optionally cross-linked to another unit at the N group—e.g., forming, together with the R.sup.3 of another unit a bond—such cross-links optionally form links between separate linear chains, or form cyclic structures, or a mixture thereof. In an exemplary embodiment, a compound of formula I comprises a plurality of units having a first structure, e.g., —[SiHCH.sub.3—NCH.sub.3]—, and a plurality of units having a second structure, e.g., —[SiH.sub.2NH]—. In specific embodiments, the ratio of the first structure to the second structure is 1:99 to 99:1. Further, in certain embodiments, the compound of Formula I optionally comprises a plurality of units having a third structure, such as wherein the ratio of the first structure to the third structure is 1:99 to 99:1. The various first, second, and optional third structures may be ordered in blocks, in some other ordered sequence, or randomly. In specific embodiments, each R.sup.1, R.sup.2, and R.sup.3 is independently selected from H and substituted or unsubstituted alkyl (straight chain, branched, cyclic or a combination thereof; saturated or unsaturated). Exemplary, polysilazanes provided herein comprise one or more unit of FIG. 10, wherein x, y, and z are individually any suitable integer, such as 1 to about 100 or 1 to about 1,000 or more, and R is as described above for R.sup.1 or R.sup.2.

    [0080] In some embodiments, the silsesquioxane compound used in a liquid medium herein comprises a structure of general formula (II):


    —[SiR.sup.1R.sup.2—O].sub.n—  (II)

    [0081] In some instances, the compound is a silsesquioxane having a cage (e.g., polyhedral oligomeric) or opened cage (e.g., wherein an SiR.sup.1 is removed from the cage) structure. FIG. 6 illustrates an exemplary cage wherein n is 8 (wherein the R group of FIG. 6 is defined by R.sup.1 herein). FIG. 7 illustrates an exemplary opened cage wherein n is 7 (wherein the R group of FIG. 7 is defined by R.sup.1 herein). In some instances, an R.sup.1 or R.sup.2 group of one unit is taken together with an R.sup.1 or R.sup.2 group of another unit to form an —O—. In certain embodiments, a cage structure is optionally formed when several an R.sup.1 or R.sup.2 groups are taken together with the R.sup.1 or R.sup.2 groups of other units (e.g., as illustrated in FIG. 6). In various embodiments, the polysilazane comprises any suitable number of units, such as 2 to 20 units and/or n is any suitable value, such as an integer between 2 and 20, e.g., 7-16. In certain embodiments, the cage comprises 8 units, but larger cages are optional. In additional, opened cages, wherein one of the units is absent are also optional.

    [0082] In some embodiments, the fluid stock has any suitable viscosity. In addition, the process and systems described herein allow for the electrospray manufacture of depositions and coatings using highly viscous (and, e.g., highly loaded) fluid stocks, if desired. For example, in some embodiments, fluid stocks utilized in systems and processes herein have a viscosity of about 0.5 centipoise (cP) or more, e.g., about 5 cP or more, or about 1 cP to about 10 Poise. In more specific embodiments, the viscosity is about 10 cP to about 10 Poise. In some instances, gas-driven systems and processes described herein allow for the production of an aerosol or plume that has enough inclusion component to facilitate good, high through-put formation of films that would not be possible using conventional techniques. In certain embodiments, the viscosity of the fluid stock is at least 200 centipoise (cP), such as at least 500 cP, at least 1000 cP, at least 2000 cP, at least 2,500 cP, at least 3,000 cP, at least 4,000 cP, or the like (e.g., up to 20,000 cP, up to about 10,000 cP, or the like). In certain embodiments, the viscosity of the fluid stock is about 2,000 cP to about 10,000 cP.

    [0083] In some embodiments, a process herein comprises or a system provided herein is configured to provide an alternating current (AC) voltage (V.sub.AC) to an electrospray nozzle, such as one provided herein. In specific embodiments, the voltage is provided to the inner conduit (e.g., the walls thereof). In certain embodiments, application of the voltage to the nozzle provides an electric field at the nozzle (e.g., at the outlet of the inner conduit thereof). In some instances, the electric field results in the formation of a “cone” (e.g., Taylor cone) at the nozzle (e.g., at the outlet of the inner conduit thereof), and ultimately a jet and/or a plume. In certain instances, after the formation of a cone, the jet and/or plume is broken up into small and highly charged liquid droplets (or particles), which are dispersed, e.g., due to Coulomb repulsion. As used herein, droplets and particles are referred to interchangeably, wherein the particles comprise droplets (e.g., comprising a liquid medium of the fluid stock) or dried particles (e.g., wherein the liquid medium of the fluid stock has been evaporated during the electrospray process).

    [0084] In some embodiments, any suitable voltage (e.g., alternating current voltage) is applied (e.g., to the nozzle). In specific embodiments, the voltage applied is about 10 kV.sub.AC (e.g., wherein the voltage refers to the root mean square voltage (V.sub.ms)) or more. In more specific embodiments, the voltage applied is about 20 kV.sub.AC or more, e.g., about 30 kV.sub.AC or more. In some specific embodiments, the voltage applied is about 10 kV.sub.AC to about 25 kV.sub.AC. In certain embodiments, a power supply system is configured to provide the voltage to the nozzle. In some embodiments, the power supply system comprises a generator, an amplifier, and/or a transformer. In specific embodiments, the generator is a waveform generator (e.g., configured to generate an alternating current (AC) voltage V.sub.AC having a suitable waveshape, such as a sine, square, or triangle waveshape). In some embodiments, the amplifier is configured to amplify the voltage (e.g., with any suitable output, such as 0-260 V.sub.ms), etc. In certain embodiments, the transformer is a high voltage transformer, e.g., configured to transform the voltage of the generator and/or amplifier to high voltage, such as a voltage provided herein. In some embodiments, the alternating current (AC) voltage (V.sub.AC) has any suitable frequency, such as about 25 Hz or more, e.g., about 50 Hz to about 500 Hz. In more specific embodiments, the frequency is about 60 Hz to about 400 Hz, e.g., about 60 Hz to about 120 Hz, or about 60 Hz to about 250 Hz. FIG. 12 illustrates high speed imaging of an exemplary system and process provided herein configured to electrospray a fluid stock using gas controlled, alternating current electrospray techniques provided herein, using various frequencies (e.g., 60 Hz (1200), 90 Hz (1210), and 120 Hz (1220)). FIG. 12 illustrates that in some instances, improved disruption of droplets is achieved when varying frequency. In some instances, variation of frequency allows and/or facilitates precise control of the coating characteristics (e.g., coating thickness, droplet/particle sizes, throughput, etc.).

    [0085] FIG. 3 illustrates an exemplary system provided herein comprising a gas controlled, alternating current (AC) voltage electrospray nozzle positioned opposite a substrate. As illustrated, a system provided herein comprises a power source (e.g., a generator). In some instances, the system further comprises an amplifier and/or transformer (e.g., high voltage transformer), e.g., configured to achieve a desired voltage and/or frequency, such as described herein. Further, as is exemplarily illustrated in FIG. 3, electrospraying a fluid stock onto a substrate forms a deposition (e.g., nanoscale or thin layer coating) thereon. In some embodiments, the substrate and/or the electrospray nozzle is configured to be mobile, allowing facile deposition onto a substrate. In some instances, the substrate is optionally configured to be affixed to a roll, and/or the nozzle is configured to be portable, such as configured to be able to move over a surface of a substrate, depositing a coating on the substrate as the nozzle moves. In specific embodiments, the substrate itself completes the circuit (e.g., is “grounded”) or positioned between a collector (e.g., an object that completes the circuit) and the nozzle. FIG. 4 shows an exemplary lab scale system illustrated in FIG. 3.

    [0086] In certain embodiments, a process herein provides or a system herein is configured to provide a pressurized gas to an outer inlet of an outer conduit of an electrospray nozzle. In some embodiments, the outer conduit is enclosed along the length of the conduit by an outer wall having an interior surface, the outer conduit having an outer conduit inlet and an outer conduit outlet. In some instances, the pressurized gas is provided from a pressurized canister, by a pump, or by any other suitable mechanism. Generally, providing pressurized gas to the inlet of the outer channel results in a high velocity gas being discharged from the outlet of the outer channel of the electrospray nozzle. Any suitable gas pressure or gas velocity is optionally utilized in processes and/or systems herein. In specific embodiments, the gas pressure applied (e.g., to the inlet of the outer channel) is about 15 psi or more. In more specific embodiments, the gas pressure is about 20 psi or more, about 25 psi or more, about 35 psi or more, about 40 psi or more, about 45 psi or more, or any other suitable pressure. In certain embodiments, the velocity of the gas at the nozzle (e.g., the outlet of the outer channel thereof) is about 0.1 m/s or more, about 0.5 m/s or more, about 1 m/s or more, about 5 m/s or more, about 25 m/s or more, or the like. In more specific embodiments, the velocity is about 50 m/s or more. In still more specific embodiments, the velocity is about 100 m/s or more, e.g., about 200 m/s or more, or about 300 m/s. In certain embodiments, the gas is any suitable gas, such as comprising air, oxygen, nitrogen, argon, hydrogen, or a combination thereof. FIG. 9 illustrates high speed imaging of an exemplary system and process provided herein configured to electrospray a fluid stock using gas controlled, alternating current electrospray techniques provided herein. FIG. 9 illustrates that in some instances, improved disruption of droplets is achieved when using high gas (e.g., air) pressure 920 (45 psi) compared to a moderately high air pressure 910 (25 psi) and a lower air pressure 910 (15 psi). In some instances, variation of air pressure allows and/or facilitates precise control of the coating characteristics (e.g., coating thickness, droplet/particle sizes, throughput, etc.).

    [0087] In certain embodiments, the inner and outer conduits have any suitable diameter. In some embodiments, the diameter of the inner conduit is about 0.1 mm or more, e.g., about 0.5 mm or more, about 1 mm or more, about 7.5 mm or more, about 10 mm or more, about 7.5 mm to about 2 cm, about 1 cm to about 2 cm, about 2.5 cm or more, or the like. In certain instances, use of alternating current systems and techniques provided herein allow for the use of larger nozzle systems, which in turn allow for improve throughput capabilities of such systems provided herein. In more specific embodiments, the diameter of the outer conduit is about 1.05 or more times the diameter of the inner conduit, e.g., about 1.1 or more times the diameter of the inner conduit, about 1.15 or more times the diameter of the inner conduit, about 1.05 to about 2.5 times the diameter of the inner conduit, about 1.1 to about 2 times the diameter of the inner conduit, or the like. Generally, as discussed herein, the inner conduit is configured inside the outer conduit, preferably along an identical axis, but slight offset configurations are also considered to be within the scope of the instant disclosure. In some embodiments, an outer wall surrounds the outer conduit, the outer wall having an interior surface (e.g., defining the outer conduit). In some embodiments, the average distance between the exterior surface of the inner wall and the interior surface of the outer wall (referred to herein as the conduit gap) is any suitable distance. In specific instances, the conduit gap is about 0.1 mm or more, e.g., about 0.5 mm or more, or about 1 mm or more. In more specific embodiments, the conduit gap is about 1 mm to about 5 mm. In certain embodiments, the gap is small enough to facilitate a high velocity gas at the nozzle and to facilitate sufficient disruption of the charged fluid (jet) ejected from the nozzle (e.g., such as to provide sufficiently small droplet sizes and sufficiently uniform inclusion dispersion in the plume and on the collection substrate). In some embodiments, the inner conduit and the outer conduit run along an identical or similar longitudinal axis, the length of which both the inner and outer conduit running along that axis being the conduit overlap length. In some embodiments, the inner conduit length, the outer conduit length, and the conduit overlap length is about 0.1 mm or more, e.g., about 0.1 mm to about 100 mm, or more. In specific embodiments, the inner conduit length, the outer conduit length, and the conduit overlap length is about 0.5 mm to about 100 mm, e.g., about 1 mm to about 100 mm, about 1 mm to about 50 mm, about 1 mm to about 20 mm, or the like. In certain embodiments, the ratio of the conduit overlap length to the first diameter being about 0.1 to about 10, e.g., about 0.1 to about 5 or about 1 to about 10. In some embodiments, the inner conduit is longer than the outer conduit, the inner conduit protruding beyond the outer conduit, e.g., as illustrated in FIG. 8. In some embodiments, the protrusion length is about −0.5 mm to about 1.5 mm, e.g., about 0 mm to about 1.5 mm, or about 0 mm.

    [0088] In certain embodiments, processes herein comprise collecting and/or systems herein are configured to collect nanoscale particles and/or droplets of the plume onto a substrate. In specific embodiments, collection of these small particles/droplets allows for the formation of a uniform deposition on the substrate. Further, given the small size of the particles and/or droplets formed by systems and processes described herein, it is possible to form depositions having thin and/or uniform layers, and to have good control of the thickness thereof. In some embodiments, the substrate is positioned opposite the outlet of the nozzle.

    [0089] In some embodiments, depositions provided herein are thin layer depositions, which are suitable for any number of applications. In various embodiments, the depositions are coatings comprising a matrix material (e.g., polymer or ceramic) and optionally further comprising inclusions (e.g., nanostructured inclusions). In some embodiments, the inclusions are dispersed in and/or on the matrix. In other embodiments, depositions provided herein are coatings comprising a plurality of structures, such as nanostructures (e.g., the nanostructures forming the coating and being dispersed on a substrate). Also provided in some embodiments herein are articles of manufacture comprising a deposition or coat, e.g., a thin-layered coat manufactured or capable of being manufactured according to the processes described herein. In certain embodiments, provided herein is a substrate comprising a coating or deposition described herein on the surface thereof.

    [0090] As discussed herein, processes and systems described herein allow for good control of the thickness of depositions provided for and described herein. In some embodiments, a deposition provided herein is a thin layer deposition, e.g., having an average thickness of about 1 mm or less, e.g., about 1 micron to about 1 mm. In specific embodiments, the deposition has a thickness of about 500 micron or less, e.g., about 1 micron to about 500 micron, about 1 micron to about 250 micron, or about 10 micron to about 200 micron, about 20 micron or less, about 0.5 micron to about 20 micron, or the like. Further, the processes and systems described herein not only allow for the manufacture of thin layer depositions, but of highly uniform thin layer depositions. In some embodiments, the depositions provided herein have an average thickness, wherein the thickness variation is less than 50% of the average thickness, e.g., less than 30% of the average thickness, or less than 20% of the average thickness. In addition, in some embodiments wherein nano-inclusions (additives) are included in the fluid stock and/or deposition (e.g., wherein the deposition comprises a matrix material, such as a polymer matrix material), the dispersion of the nano-inclusions (additives) is such that the most probable distance between the nano-inclusions is about 10 nm or more, e.g., about 100 nm or more, about 10 nm to about 10 mm, about 10 nm to about 1000 nm, about 100 nm to about 10 mm, or about 100 nm to about 1000 nm.

    [0091] Further, in some embodiments, it is desirable that any additives in the fluid stock are dissolved and/or well dispersed prior to electrospray, e.g., in order to minimize clogging of the electrospray nozzle (and/or other system components), ensure good uniformity of dispersion of any inclusions in the resulting deposition, and/or the like. In specific embodiments, the fluid stock is agitated prior to being provided to the nozzle (e.g., inner conduit inlet thereof), or the system is configured to agitate a fluid stock prior to being provided to the nozzle (e.g., by providing a mechanical stirrer or sonication system associated with a fluid stock reservoir, e.g., which is fluidly connected to the inlet of the inner conduit of an electrospray nozzle provided herein).

    [0092] In a specific and exemplary embodiment, processes and systems provided herein are useful for manufacturing a deposition on a substrate that is transparent and/or imposes hydrophobic and/or oleophobic (anti-fingerprinting) characteristics to the surface. In addition, in some instances, the surface is anti-reflective. In specific embodiments, a process and/or system provided herein is utilized to manufacture such a surface. In some embodiments, the fluid stock suitable therefore comprises, for example, a polysilazane and/or a silsesquioxane (e.g., polyhedral oligomeric silsesquioxane (POSS) and/or polysilsesquioxane (PSSQ)). In further or alternative embodiments, the fluid stock comprises a transparent polymer (e.g., a polymer that is transparent in the form of a coating, such as a film (e.g., a coherent film), at a thickness less than the thickness of the deposition coating, such about 1 mm or less). A non-limiting example of such a polymer is polycarbonate (poly(bisphenol a carbonate)), or any other suitable polymer described herein. In preferred embodiments, the polymer is not soluble or swellable in water. In certain embodiments, the fluid stock further or alternatively comprises nanostructured inclusions, such as silica nanoparticles, or any other suitable inclusion described herein. In some embodiments, the fluid stock further or alternatively comprises fluoroalkyl silane or perfluoropolyether alkoxy silane (e.g., wherein alkyl or alk is a saturated or unsaturated straight chain or branched hydrocarbon having 1-20 carbon atoms, e.g., 1-6 carbon atoms, such as methyl, ethyl, propyl, isopropyl, butyl, t-butyl, sec-butyl, pentyl, hexyl, or the like). In specific embodiments, the fluid stock comprises polycarbonate, silica nanoparticles, organic polysilazane, and fluoroalkyl silane the ratio of polycarbonate to silica nanoparticles to organic polysilazane to fluoroalkyl silane being about 1 to about 70 (e.g., about 1 to about 50, or about 10 to about 30) weight parts polymer (e.g., polycarbonate) to about 1 to about 95 (e.g., about 5 to about 70, or about 10 to about 50, or about 20 to about 40) weight parts inclusions (e.g., silica nanoparticles) to about 1 to about 99 (e.g., about 10 to about 90, about 25 to about 75, about 40 to about 60, or about 50) weight parts ceramic precursor (e.g., organic polysilazane). In additional embodiments, the fluid stock further comprises a fluorinated organosilane, e.g., with about 0.05 to about 5 (e.g., about 0.1 to about 2.5, or about 0.5 to about 1.5) weight parts thereof (e.g., fluoroalkyl silane).

    [0093] In certain embodiments, superhydrophobic surfaces provided herein have a contact angle (e.g., of water) of about 130 degrees or more, e.g., about 135 degrees or more. The process of claim 28, wherein the superhydrophobic surface has a water contact angle of at least 130 degrees.

    [0094] In some embodiments, articles of manufacture are provided herein comprising, e.g., a coat described herein. In certain embodiments, an article of manufacture provided herein comprises a deposition (e.g., thin layer deposition) described herein. In specific embodiments, provided herein is an article of manufacture comprising a substrate with a surface, the surface being at least partially coated with a material that imparts to the surface superhydrophobic characteristics, such as described herein. In specific embodiments, an article of manufacture provided herein comprises a coating or deposition comprising a polymer matrix and a plurality of nano-inclusions embedded therein (and/or on the surface thereof). In yet more specific embodiments, the polymer matrix comprises polycarbonate and the nano-inclusions comprise silica nanoparticles. In some embodiments, the article of manufacture comprising a surface is any suitable article, such as, by way of non-limiting example, a window pane, such as in a building or automobile, eye glasses, laptop computers, computer monitors, televisions, tablets, mobile telephones (e.g., Smartphones), personal digital assistants (PDAs), watch, and other objects and articles.

    [0095] In certain embodiments, the substrate is any suitable substrate (e.g., a grounded substrate, or a substrate located between the electrospray nozzle and a grounded plate). In some embodiments, collected films are optionally removed from the substrate to provide self-supporting film (e.g., that is optionally deposited on a secondary surface).

    [0096] In some instances, material or films/depositions provided herein are high density (e.g., about 0.1 g/cm.sup.3 or more, about 0.5 g/cm.sup.3 or more (such as about 1 g/cm.sup.3, about 1.5 g/cm.sup.3 or more, greater than 1.5 g/cm.sup.3, about 0.7 g/cm.sup.3 to about 2 g/cm.sup.3, or the like), flexible, and/or thin layer films or depositions.

    [0097] In some embodiments, relatively small amounts of inclusion are required to form a coating or film provided herein, such as wherein the coating or film has good performance uniformity over the surface of the coating or film. In some instances, processes provided herein are well designed to not only manufacture high performance materials, but to also manufacture thin materials having very good uniformity and very low defect characteristics (e.g., which defects may result in reduced performance over time).

    [0098] In various embodiments herein, inclusions and materials are described as having specific characteristics. It is to be understood that such disclosures include disclosures of a plurality of such inclusions having an average equal to the specific characteristics identified, and vice-versa.

    EXAMPLES

    Example 1: Alternating Current Electrospray

    [0099] A fluid stock comprising 3 wt. % polyvinylalcohol (PVA) in water is prepared. The solution is provided (e.g., at a flow rate of about 0.01 to about 0.015 mL/min) to a non-gas-controlled electrospray nozzle, to which a direct voltage of about 10 kV to about 15 kV is maintained. A grounded collector is positioned opposite the electrospray nozzle, at a distance of about 20 cm to about 25 cm. High speed imaging of the electrospray process is illustrated in FIG. 1 (left panel, 101).

    [0100] A similar 3 wt. % PVA (MW:78,000) solution is provided at a flow rate of 0.1 mL/min to a non-gas-controlled electrospray nozzle (the inner conduit being about 10 gauge), to which an alternating current (AC) voltage (V.sub.AC) of about 20 kV is applied at a frequency of about 100 to about 200. The collector/substrate is configured about 17 cm from the nozzle tip, with a coating deposited thereon.

    [0101] A 7 wt. % PVA (MW:25,000) solution is provided at a flow rate of 0.1 mL/min to a non-gas-controlled electrospray nozzle (inner conduit being about 10 gauge), to which an alternating current (AC) voltage (V.sub.AC) of about 20 kV is applied at a frequency of about 200 to about 300. The collector/substrate is configured about 17 cm from the nozzle tip, with a coating deposited thereon.

    Example 2: Gas Controlled, Alternating Current Electrospray

    [0102] A PVA solution is prepared, such as set forth in Example 1. The fluid stock is electrosprayed by injecting the solution into a gas (air) stream using a coaxially configured nozzle as described herein. An alternating current (AC) voltage (V.sub.AC) is applied to the nozzle, and a coating is collected on a substrate a distance away from the nozzle. Exemplary parameters are illustrated in Table 1.

    TABLE-US-00001 TABLE 1 Exemplary gas controlled, alternating current electrospray parameters. Concentration Nozzle Size Frequency Voltage Flow Rate MW (wt. %) (gauge) (Hz) (kV) (mL/min) Distance (cm) 25,000 3 16 130 20 0.17 27 5 16 130 20 0.17 27 7 16 130 20 0.6 27 78,000 3 16 130 20 0.35 27

    [0103] In addition, variation of air flow, voltage frequency, flow rate, etc. are observed to facilitate control of droplet breakup and coating formation. For example, FIG. 9 illustrates that in some instances, improved disruption of droplets is achieved when using high gas (e.g., air) pressure 920 (45 psi) compared to a moderately high air pressure 910 (25 psi) and a lower air pressure 910 (15 psi); FIG. 12 illustrates that in some instances, improved disruption of droplets is achieved when using various frequencies (e.g., 60 Hz (1200), 90 Hz (1210), and 120 Hz (1220)); and FIG. 13 illustrates that in some instances, improved disruption of droplets is achieved when using various flow rates (e.g., 0.3 mL/min (1300), 0.6 mL/min (1310), and 1.0 mL/min (1320)). As can be seen in FIG. 9, very good disruption of the plume is observed when high pressure gas is utilized, whereas lower pressure gas provides less optimal results. By contrast, as observed in FIG. 1, no gas results in very poor “plume” formation, with large droplets being formed (e.g., resulting in inclusion aggregation and puddling on the substrate). As can be seen in FIG. 13, even at very high flow rates (1.0 mL/min), very good disruption of the plume and very small droplets are observed.

    Example 3

    [0104] Using fluid stocks and techniques, such as those described in Examples 1 and 2, a deposition is prepared by electrospraying the fluid stock using V.sub.AC and a nozzle having a diameter of up to 1 cm or more, such as illustrated in FIG. 2 (200).

    Example 4

    [0105] A viscous fluid stock comprising graphene oxide (0.75 wt. %) in an aqueous medium (additive:liquid medium=0.75:99.25). The fluid stock is electrosprayed on a substrate using a non-gas controlled DC process, a gas-controlled DC process, and a gas-controlled AC process.

    [0106] For the non-gas controlled DC system, a working voltage of 25 kV.sub.DC, a distance from the nozzle to the collector of 20 cm, and a flow rate of 0.07 mL/min is utilized. For the gas controlled DC system, a working voltage of 25 kV.sub.DC, a distance from the nozzle to the collector of 20 cm, and a flow rate of 0.07 mL/min is utilized. For the gas controlled AC system, similar conditions are utilized (e.g., with parameters as set forth in Example 2), but with flow rates increased to 0.3 mL/min to 1 mL/min. Very fine, well dispersed coatings are observed for both the DC and AC electrospray gas-controlled systems, with the AC electrospray systems providing greatly improved throughput. By contrast, the non-gas controlled system failed to produce film formation, with large droplets and collections of graphene oxide being quickly observed on the substrate; large defects are observed even after only 1 minute, with the collected material beginning to pool and run. By contrast, well-ordered films are observed when spraying graphene oxide fluid stocks with high velocity gas, even when spraying long enough to form thick films.