Aerosol-based 3D printing of nanoparticles

Abstract

Systems and methods for aerosol-based three-dimensional (3D) printing (A3DP) are provided and can be used for layer-by-layer printing of polymers, metals, and composite materials by melting their nanoparticles. A solution containing nanoparticles (of the material(s) to be 3D printed or their precursors) is atomized to produce droplets of the material. The solvent can then be evaporated using a dryer and / or a furnace, and particles can be fed into a 3D printing nozzle. The nozzle can be heated to melt the particles and translated over the printer bed according to the 3D model file to deposit semi-molten nanoparticles and print the structure.

Description

DESCRIPTIONAEROSOL-BASED 3D PRINTING OF NANOPARTICLESCROSS-REFERENCE TO RELATED APPLICATIONThis application claims the benefit of U.S. Provisional Application Serial No. 63 / 580,272, filed September 1, 2023, the disclosure of which is hereby incorporated by reference in its entirety, including all figures, tables, and drawings.BACKGROUNDState-of-the-art three-dimensional (3D) printing techniques include: 1) extrusion and melting of a wire filament (for polymers, no metals) and printing on a surface; 2) photocuring a liquid polymer with light or a laser; 3) melting a bed or pile of metal powder with a laser or electron beam; or 4) extruding a viscous ink. However, each of these technologies has at least one of the following limitations: i) lack of versatility (i.e., inability to print a broad variety of materials and / or on a wide range of surfaces); ii) lack of speed (i.e., inability to print quickly, considering the post-processing of the printed structure); and iii) lack of resolution and precision (i.e., poor resolution and ability to control the properties of the printed structure). For example, powder bed fusion, the primary technique for 3D printing of metals, is highly complex, uses a powder bed that is difficult to manage, uses a high-energy laser that increases the process energy demand, and has a resolution of only 50 micrometers (pm) as it uses large particles (45 pm), and having a bed of small nanoparticles is very challenging. Additionally, it is difficult to print composite polymeric materials with the powder bed fusion technique.BRIEF SUMMARYEmbodiments of the subject invention provide novel and advantageous systems and methods for aerosol-based three-dimensional (3D) printing (A3DP). A3 DP can be used for layer- by-layer (i.e., additive manufacturing) printing of polymers, metals, metal oxides, and composite materials by melting their nanoparticles. In A3 DP, a solution of materials to be printed (that can contain soluble materials or nanoparticles or their precursors) is atomized (e.g., using a collison nebulizer) to produce droplets of the material (solvent and precursor / nanoparticles). The solvent can then be evaporated using a dryer (e.g., a diffusion dryer) and / or a furnace (e.g., an electricfurnace), and particles can be fed into a 3D printing nozzle. The nozzle can be heated to melt the particles and translated over the printer bed according to the 3D model file to deposit molten or semi-molten nanoparticles and print the structure. A3DP can be used to print polymers, metals, and composite materials at high resolution with fine details. The systems and methods are simple to use and capable of printing nearly any material with speed, resolution, and accuracy.In an embodiment, a method for A3 DP can comprise: dissolving a first material in a first solvent to give a first solution; atomizing the first solution to produce first droplets comprising the first solvent and the first material; evaporating the first solvent by providing the first droplets to at least one of a dryer and a furnace to leave first particles comprising the first material; feeding the first particles into a 3D printing nozzle; heating the 3D printing nozzle to melt the first particles and give heated particles that are molten or semi-molten; and using the 3D printing nozzle to deposit the heated particles on a substrate, thereby printing a structure using a deposited material. The deposited material can comprise the first material or the first material can be a precursor of the deposited material. The first solvent can be evaporated by, for example, providing the first droplets to the dryer or by providing the first droplets to the furnace. The dryer can be a diffusion dryer, and the furnace can be an electric furnace. The first material can comprise first soluble materials dissolved in the first solvent and / or suspended nanoparticles dispersed in the first solvent (e.g., only nanoparticles, only dissolvable (i.e., soluble) material, or both). The first material can be or comprise a polymer, a metal, a metal oxide, or a combination thereof (including multiple polymers, multiple metals, or multiple metal oxides). Atomizing the first solution to produce the first droplets can comprise using a collision nebulizer. A size of the first droplets can be in a range of from 1 micrometer (pm) to 5 pm. A resolution of the A3DP can be, for example, 40 pm or less (e.g., 10 pm or about 10 pm). The first solution can further comprise a second material different from the first material; the deposited material can be a composite material of a third material and a fourth material; the first material can be the same as the third material or can be a precursor of the third material; and the second material can be the same as the fourth material or can be a precursor of the fourth material. The second material can comprise second soluble materials dissolved in the first solvent and / or suspended nanoparticles dispersed in the first solvent (e.g., only nanoparticles, only dissolvable (i.e., soluble) material, or both). The second material can be or comprise a polymer, a metal, a metal oxide, or a combination thereof (including multiple polymers, multiple metals, or multiple metal oxides). Asize of the first particles can be in a range of from 450 nanometers (nm) to 2.5 pm. The first material can be a water-soluble polymer (for example, polyethylene glycol (PEG)).The method can further comprise: dissolving a second material in a second solvent to give a second solution; atomizing the second solution to produce second droplets comprising the second solvent and the second material; evaporating the second solvent by providing the second droplets to at least one of the dryer and the furnace to leave second particles comprising the second material; and feeding the second particles into the 3D printing nozzle. Heating the 3D printing nozzle can melt the second particles; the heated particles can comprise the second material; the deposited material can be a composite material of a third material and a fourth material; the first material can be the same as the third material or can be a precursor of the third material; and the second material can be the same as the fourth material or can be a precursor of the fourth material. A size of the second particles can be in a range of from 450 nm to 2.5 pm.In another embodiment, a system for A3DP can comprise: a solvent-evaporating device that comprises at least one of a dryer and a furnace; a 3D printing nozzle connected to an exit of the solvent-evaporating device; a tube connecting the 3D printing nozzle to the exit of the solvent evaporating device; a heating element disposed around the 3D printing nozzle and configured to heat the 3D printing nozzle during use; and a platform disposed below an exit of the 3D printing nozzle and configured for 3D printing thereon. The device can further comprise an atomizer configured to atomize a solution to produce droplets to be provided to the solvent-evaporating device. The atomizer can comprise or be, for example, a collison nebulizer. The system can further comprise a container connected to an entrance of the solvent-evaporating device and configured to have droplets contained therein. The system can further comprise a first chamber having the container and the solvent-evaporating device disposed therein. The solventevaporating device can comprise the dryer, the furnace, or both. The dryer can be a diffusion dryer, and the furnace can be an electric furnace. A resolution of the A3DP of the system can be, for example, 40 pm or less (e.g., 10 pm or about 10 pm).In another embodiment, a system for A3DP of in situ synthesized materials can comprise: a device (e.g., an atomizer, a nebulizer, a vaporizer, etc.) generating vapors and / or droplets of a precursor of the in situ synthesized materials; a solvent-evaporating device that comprises at least one of a dryer and a first furnace; a high-temperature furnace connected to an exit of the solvent-evaporating device and configured to decompose the precursor; a first tube connecting the high temperature furnace to the exit of the solvent-evaporating device; a 3D printing nozzleconnected to an exit of the high-temperature furnace; a second tube connecting the 3D printing nozzle to the exit of the high temperature furnace; a heating element disposed around the 3D printing nozzle and configured to heat the 3D printing nozzle during use; and a platform disposed below an exit of the 3D printing nozzle and configured for 3D printing thereon. The device can further comprise a container connected to an entrance of the solvent-evaporating device and configured to have droplets contained therein. The device can further comprise a first chamber having the container and the solvent-evaporating device (and the high-temperature furnace) disposed therein. The solvent-evaporating device can comprise the dryer, the first furnace, or both. The dryer can be a diffusion dryer, and the first furnace can be an electric furnace. A resolution of the A3 DP of the system can be, for example, 40 pm or less (e.g., 10 pm or about 10 pm).BRIEF DESCRIPTION OF DRAWINGSFigure la shows a schematic view of a system for aerosol-based three-dimensional (3D) printing (A3DP), according to an embodiment of the subject invention.Figure lb shows images of structures printed using the system for A3DP as shown in Figure la. The middle image is a microscopic image with a scale bar of 50 micrometers (pm).Figures 2a-2c show scanning electron microscope (SEM) images of microstructures of polyethylene glycol (PEG) printed at different nozzle temperatures. Figures 2a-2c show images or a nozzle temperature of 50 °C, 75 °C, and 100 °C, respectively. The scale bar for each image is 100 pm.Figure 3a shows an electron microscope image of microstructures of PEG printed using an A3DP system. The scale bar is 10 pm.Figure 3b shows an electron microscope image of microstructures of a composite of PEG and lignin printed using an A3DP system. The scale bar is 500 nanometers (nm).Figure 3c shows an electron microscope image of microstructures of a composite of carbon particles and PEG printed using an A3DP system. The scale bar is 1 pm.Figure 3d shows an electron microscope image of a functionally graded material comprising lignin and PEG. The scale bar is 100 pm.Figure 4 shows an overview of development of an A3 DP system.Figure 5a shows different nozzles that may be used with an A3DP system, according to embodiments of the subject invention.Figure 5b shows structure shapes that can be printed with an A3DP system, according to embodiments of the subject invention.Figure 6 shows a schematic view of a system for A3 DP, according to an embodiment of the subject invention.Figure 7 shows a chart comparing A3DP technology of embodiments of the subject invention to other types of 3D printing.Figure 8 shows a chart of example materials that can be printed using an A3 DP system according to embodiments of the subject invention.Figure 9a shows an electron microscope image of a top view of PEG printed using an A3DP system. The scale bar is 200 pm.Figure 9b shows an electron microscope image of a side view of PEG printed using an A3DP system. The scale bar is 100 pm.Figure 9c shows an electron microscope image of a top view of PEG printed using an A3DP system. The scale bar is 50 pm.Figure 9d shows an electron microscope image of a cross section of PEG printed using an A3DP system. The scale bar is 20 pm.Figures lOa-lOh show images of different shapes and structures of PEG printed using an A3DP system. Figures 10a and lOd show a square structure with a length of 5 millimeters (mm), a width of 5 mm, a height of 1 mm, and a line width of 0.2 mm. Figures 10b and lOe show an equilateral triangle structure with each side having a length of 5 mm and the line width being 0.2 mm. Figures 10c and lOf show a circle structure with a diameter of 5 mm and a line width of 0.2 mm. Figures 10g and lOh show a pentagon structure and a hexagon structure, respectively.Figure Ila shows a grid that can be printed using an A3DP system. Though certain dimensions are shown in Figure I la, these are for exemplary purposes only and should not be construed as limiting. Images of a grid printed using PEG and a lignin / PEG composite are shown in the left side and the right side, respectively, of Figure lb.Figure 11b shows an electron microscope image of a grid as shown in Figure I la, printed with a lignin / PEG composite using an A3DP system. The scale bar is 500 pm.Figure 12 shows images of a lignin / PEG composite printed using an A3DP system. The top image shows the square structure (5 mm (length) by 5 mm (width) by 1 mm (height). The solution that was used to print the composite had 2.5 milligrams per milliliter (mg / ml) oflignin and 100 mg / ml of PEG. The scale bar for the bottom lefthand and bottom righthand images are 200 gm and 10 pm, respectively.Figure 13 shows images of a lignin / PEG graded composite material printed using an A3DP system. The righthand image shows an enlarged version of the box in the lefthand image. From left to right in each image, the lignin concentration is graded from 2.5 mg / ml lignin to 0 mg / ml of lignin.Figure 14 shows images of the lignin / PEG graded composite material from Figure 13. The righthand image shows an enlarged version of the box in the bottom lefthand image. The scale bar for the bottom lefthand and the righthand images are 200 pm and 10 pm, respectively.Figure 15 shows images of a titanium dioxide (TiChj / PEG composite printed using an A3DP system. The top righthand image shows an enlarged version of the box in the lefthand image. The solution that was used to print the composite had 0.5 mg / ml of TiCh and 100 mg / ml of PEG. The scale bar for the lefthand, top righthand, and bottom righthand images are 100 pm, 10 pm, and 10 pm, respectively.Figures 16a-16d shows fluid flow through the four different nozzles, respectively, shown in Figure 5a.Figure 17 shows different nozzles that may be used with an A3 DP system, according to embodiments of the subject invention.Figure 18 shows a depiction of parameters that can be examined for a nozzle used with an A3 DP system.Figure 19a shows a plot of focusing ratio versus aerosol flow velocity (in meters per second (m / s)) for nozzle 1 from Figure 17, and Figure 19b shows a plot of focusing ratio versus ratio of aerosol flow rate to sheath flow rate for nozzles 2-4 from Figure 17. An aerosol flow of 2.35 m / s was used to obtain the results in Figure 19b. A particle size of 500 nm, a nozzle size of 0.4 mm, and a nozzle-to-printing surface distance of 0.5 pm was used to obtain the results for both Figure 19a and Figure 19b.Figure 20a shows a plot of collection efficiency versus aerosol flow velocity (in m / s) for nozzle 1 from Figure 17, and Figure 20b shows a plot of collection efficiency versus ratio of aerosol flow rate to sheath flow rate for nozzles 2-4 from Figure 17. An aerosol flow of 2.35 m / s was used to obtain the results in Figure 20b. A particle size of 500 nm, a nozzle size of 0.4 mm, and a nozzle-to -printing surface distance of 0.5 pm was used to obtain the results for both Figure 20a and Figure 20b.Figures 21a-21c show SEM images of microstructures of poly vinylidene fluoride (PVDF) printed at different nozzle temperatures. Figures 21a-21c show images for a nozzle temperature of 170 °C, 200 °C, and 220 °C, respectively. The scale bar for each image is 5 pm.Figures 22a-22f show SEM images of microstructures of composite materials at different concentration ratios. Figure 22a shows PEG only; Figure 22b shows PEG / PVDF at a ratio of 20:5 (PEG:PVDF); Figure 22c shows PEG / PVDF at a ratio of 10:15(PEG:PVDF); Figure 22d shows PEG / lignin at a ratio of 20:5 (PEG ignin); Figure 22e shows PEG / lignin at a ratio of 10:15 (PEG ignin); and Figure 22f shows PEG / lignin at a ratio of 100:25 (PEGdignin). The scale bar for each image in Figures 22a-22c and 22f is 10 pm, and the scale bar for each image in Figures 22d and 22e is 5 pm.DETAILED DESCRIPTIONEmbodiments of the subject invention provide novel and advantageous systems and methods for aerosol-based three-dimensional (3D) printing (A3 DP). A3DP can be used for layer- by-layer (i.e., additive manufacturing) printing of polymers, metals, and composite materials by melting their nanoparticles. In A3DP, a solution containing soluble materials or nanoparticles (of the material(s) to be 3D printed or their precursors) is atomized (e.g., using a collison nebulizer) to produce droplets of the material (solvent and precursor / nanoparticles). The solvent can then be evaporated using a dryer (e.g., a diffusion dryer) and / or a furnace (e.g., an electric furnace), and particles can be fed into a 3D printing nozzle. The nozzle can be heated to melt the particles and translated over the printer bed according to the 3D model file to deposit molten or semi-molten nanoparticles and print the structure. A3DP can be used to print polymers, metals, metal oxides, and composite materials (e.g., composites of polymers, composites of metal oxide and polymers, and composites of metals and polymers) at high resolution with fine details. The systems and methods are simple to use and capable of printing nearly any material with speed, resolution, and accuracy.Systems and methods of embodiments of the subject invention are simple to use, energyefficient, and low-cost compared to related art 3D printing techniques. The systems and methods do not involve solvent-substrate interaction because the solvent is evaporated prior to printing; hence, they can be used to print structures on any surface. A3 DP advances the field of additive manufacturing, along with the aerospace, healthcare, energy, automotive, and defense industries.Figure la shows a schematic view of a system for A3DP, according to an embodiment of the subject invention; and Figure lb shows images of structures printed using the system for A3DP as shown in Figure la. Referring to Figures la, the A3 DP system combines the continuous aerosol process for particle synthesis with 3D printing capabilities. A solution of material to-be- printed can be aerosolized (e.g., using a nebulizer), which generates droplets ranging, for example, from 1 pm to 5 pm in size. A smooth printing operation requires that the solution is stable - the solute (material to-be-printed) is either soluble or well dispersed within the solvent. The droplets are then carried by a carrier gas into a dryer (e.g., diffusion dryer), heater, and / or furnace to evaporate and remove the solvent, producing dry particles. The particle size can be controlled through the material concentration in the solution and can be measured online using aerosol instruments, such as a scanning mobility particle sizer (SMPS) and a GRIMM® device, and offline with a scanning electron microscope (SEM). The dry particles can subsequently be introduced into the printing nozzle inside a customized printing chamber. The printing nozzle can be heated, and as the particles pass through the nozzle, they undergo melting because the particles (with size on the order of nanometers or at least sub pm) melt rapidly during the short residence time in the nozzle. The molten / partially molten particles deposit on the printing surface or a previously printed layer, adhere, and solidify. The coordinated movement of the nozzle and the printing surface, dictated by the 3D model, facilitates the sequential layer-by-layer construction of a 3D structure. The resolution of the printer is defined as the smallest dimension it can print in the x, y, and z directions. Printing precision is defined as the accuracy in printing dimensions (x, y, and z) compared to the 3D model. The structures can be printed onto any flat surface and can also be detached from the surface post-printing.Figure 7 shows a table comparing A3DP (embodiments of the subject invention, far right column) to related state of the art 3D printing technologies, showing the advantages of A3DP. Figure 8 shows a table of example materials that can be printed using A3DP and how the aerosol can be produced before supplying to the printer.The particle deposition on the printing surface occurs through inertial impaction. When a gaseous stream containing particles flows through a nozzle with a small orifice, the flow is choked, with the upstream pressure much higher than the downstream pressure. Meanwhile, the particle experience heat from the heated nozzle and melts. Upon exiting the nozzle, the flow expands, and molten particles accelerate toward the printing surface. The particles experience the following forces: 1) drag force, which represents friction between the particle and carriergas; 2) Basset force, which represents a non-steady viscous gradient force; 3) inertia; 4) gravity force; 5) Saffman force, which represents a steady lift force induced by the local shear flow of a viscous fluid; and 6) thermophoretic force, representing temperature gradient between the nozzle and printing surface. In A3DP printing, Basset force is negligible due to the very low viscosity of the carrier gas. Similarly, the Saffman force can be disregarded due to the low viscosity of the carrier gas and the limited gradient of gas velocity within the nozzle cross-section. Therefore, the predominant forces to consider are drag, inertia, gravitational, and thermophoretic forces. Moreover, the gravitational force is low for small particles.If the thermophoretic force is small, particle deposition is defined by particle stokes number (Stk), (Stk =and depends on several factors, including particle size dp), pressure differential, article velocity (uP), fluid dynamic viscosity (p), particle density (pP), geometry of the surface (Dn), and Cunningham slip correction factor (C). Here fc = I + 0.15 eP°687is the correction factor to account for Reynolds number (Re) higher than unity. As the particle-carrying gas approaches the surface, the particle adheres to the surface if particle Stk > critical Stk and the gas diverts away from the vicinity of the surface. Having a particle size distribution, the large particles with high inertia, and hence, high Stk number, deviate from the gas flow and impact on the surface, whereas small particles that have low inertia and low Stk number follow the gas trajectory and deposit around the printing line in a broadened deposition pattern, which is called overspray (can be seen on the microscopic image in Figure lb). While the overspray is significantly smaller than the printed structure dimensions, its elimination is crucial for enhancing precision and resolution. Apart from particle size, the process parameters that affect the Stk number and / or influence the overspray can be crucial. For example, a smaller nozzle diameter minimizes overspray and enhances precision and resolution due to the higher particle velocity coming from the smaller nozzle, which improves the direct impaction of the particle on the surface. However, smaller nozzles are also susceptible to clogging issues. The particle impaction theory serves as a fundamental principle to various deposition techniques, such as cold spray or aerosol impaction-driven deposition and aerosol instrumentation.The issue of overspray can occur in 3D printing if droplets on the order of 1 pm - 5 pm are deposited on the printing surface at lower flow rates (such as less 200 standard cubic centimeters per minute (seem)). Although the droplets are much larger to directly impact the surface, having a size distribution of droplets and low flow rates decreases the Stk number, leading to overspray. However, A3DP utilizes particles that are much smaller (e.g., less than 2pm) and prints molten particles. Smaller particles have a low tendency to deviate from the gas flow and impact the surface but are required to achieve high resolution. Systems and methods of the subject invention can attain a resolution of no more than 40 pm in the x-y directions and no more than 100 nm in the z-direction using a simple converging orifice nozzle.Composite materials have several advantages over single materials, as they can be tailored to specific requirements, allowing for the incorporation of desired properties such as stiffness, thermal conductivity, and electrical conductivity. One example is a composite of polymer and carbon materials for manufacturing parts of flexible electronics, where the polymer provides flexibility to the structure and the carbon material provides desired thermal and electrical conductivity. Existing methods for printing composite materials are limited in their ability to print as-synthesized customized particles. Embodiments of the subject invention can print materials synthesized in situ from their precursors and use any type of aerosol-based material synthesis process prior to the printing process. This allows an advantage in printing any type of material. Figures 3a-3d show several materials printed via A3DP, including a polymer (polyethylene glycol (PEG)), a composite of polymers (lignin and PEG), a composite of metal and polymer (in situ synthesized carbon particles from lignin decomposition and PEG), and functionally graded material of lignin and PEG in Figures 3a-3d, respectively. The A3DP process offers a distinct capability to integrate aerosol synthesis processes into the A3DP printing system, thereby facilitating the printing of customizable materials with specific properties (mechanical, thermal, and electrical properties) and offering unprecedented versatility. This will provide many advantages in the field of additive manufacturing. Embodiments of the subject invention can print any 3D printing material, including low-melting point water-soluble materials (polymer), composites of low-melting water-soluble and water-insoluble materials (polymers), and composites of a high-melting point non-soluble (metal oxides particles) and a low melting point soluble material (polymers).Apart from printing resolution and precision, A3DP process parameters can control other properties of the printed structure, such as morphology (porous vs. dense), porosity, mechanical strength, conductivity, and other application- specific properties. Morphology of the printed structure is a direct function of the rate of melting of the particles, the residence time of the particle in the nozzle and between the nozzle and the printing surface, and the rate of solidification. These can be controlled via process parameters. Several of these parameters are interdependent; for example, the nozzle throat diameter affects the nozzle temperature requiredto melt the particles. A larger diameter widens the flow inside the nozzle and raises the required nozzle temperature to melt the particles. Because a wider nozzle throat requires a high temperature for melting the particles, a porous structure will be produced compared to the structure printed with a smaller nozzle throat diameter at the same nozzle temperature. The particle size will affect the total mass of material for printing and impact the internal porosity at a microscopic scale.Parameters, such as nozzle temperature, printing surface temperature, and nozzle-to- printing surface distance, are also externally accessible and influence structure porosity. A higher nozzle-to-printing surface controls the solidification of the molten particles, with a larger distance providing more time for solidification, therefore, depositing semi-molten to solid particles, leading to increased structural porosity. Extensive experimentation has been conducted to study all these parameters to obtain a wide range of morphology based on parameters (see also Figures 16a-16d, 17, and 18). The morphologies ofthe printed structures have been analyzed using an SEM. A comprehensive parameter-property map of printed structures have been developed, and correlations between the process parameters and the printing characteristics have been established that enable the successful application of these relationships to the printing of various single polymeric materials.Embodiments can print composite structures comprising two polymers of different melting points and water solubilities. For example, PEG (melting point = 55 °C), which is water- soluble, can be combined with poly vinylidene fluoride (PVDF) (melting point = 177 °C), which is water-insoluble. The structures in Figures 5b can be printed using any of the nozzles shown in Figures 5a or 17. In order to print composites, one of the following methods can be used: 1) preparing a stable solution of the two polymers mixed together and aerosolizing the mixed solution, which will generate composite particles; and / or 2) preparing two individual solutions of each polymer, aerosolizing each of them and mixing the polymer particles in-flight to the printer nozzle. These procedures can result in distinct printing properties (including morphology and each polymer distribution) based on the composition of each polymer and the melting and cooling dynamics of the polymer particles and are important to investigate.With respect to aerosolizing a mixed solution of polymers, this necessitates a stable solution of the polymers with vastly different properties. Insolubility of the second polymer in water requires preparing a solution in an organic solvent, which alters the dynamics of solvent evaporation and capture. In order to dissolve them together, another solvent (e.g., dimethylformamide (DMF)) can be used. While a change in the solvent affects droplet dynamics, solvent evaporation, solvent capture, and generation of dry particles, the process does not require large modifications. The nebulizer can spray a DMF solution, and the diffusion dryer can be replaced with a high-pore-size inert molecular sieve to adsorb DMF. If needed, the residence time of aerosolized droplets in the diffusion dryer can be extended to ensure the evaporation of DMF. This reinforces the capability to print materials that cannot be dissolved in water, opening a window of a range of polymers for printing with A3 DP technology.Aerosolizing the mixed polymer solution will produce droplets containing both polymers in the same composition as the solution. The primary parameter for printing is the nozzle temperature as it melts the particles, which can be categorized in two different regimes - 1) temperature lower than the melting point of the composite polymer (Tnozzie < Tmeiting, composite), and 2) temperature higher than the melting point of (Tnozzie > Tmeiting, composite)- It is important to note that the melting point of a composite polymer would lie between the melting points of each polymer and will be a function of the composition of the first polymer (Pl) and the second polymer (P2). In the first regime, composite particles will either remain solid or partially soften as they pass through the nozzle, and as they deposit, they will partially sinter with previously deposited particles and form a porous structure. When the particles do not melt, the adhesion or sintering between them is due to high-velocity impaction on the printing surface. In the second regime (Tnozzie > Tmeiting, composite), when the nozzle temperature is sufficient to melt the composite particles, molten particle deposition and solidification will result in a dense structure. If the temperature is too high, composite particles will melt and retain a high temperature. The delayed solidification upon printing will cause the printed material to deform and deteriorate the precision.At a particular temperature, the porosity of the structure can also be controlled by changing the total concentration and P1 / P2 concentration ratio. At a fixed nozzle temperature and nozzle -to-printing surface distance, a lower P1 / P2 ratio will result in a more porous structure due to faster solidification. Because one droplet produces one particle and the droplet size is independent of the nozzle temperature, particle size distribution in all three temperature regimes is the same. A high total concentration of the polymers will produce larger particles and an increased porosity within the structure at low nozzle temperature.The effect of printing parameters such as nozzle-to-printing surface distance and nozzle throat diameter will mirror the observation in the case of printing a single polymer. Overallnozzle temperature, printing surface temperature, the total concentration of the two polymers, and the ratio of their individual concentrations are critical parameters for printing composite polymers.Another strategy is to aerosolize both polymers separately, using different solutions for each of them. This eases up the formulation of the polymer solutions; the solution of the water- soluble polymer (Pl (e.g., PEG)) in water and the solution of water-insoluble polymer (P2 (e.g., PVDF)) in solvent (e.g., DMF). The droplets of each polymer can be passed through separate diffusion dryers, and dry polymer particles can be mixed in flight to the printer nozzle. A schematic diagram of the A3 DP process for two aerosol feeds is presented in Figure 6. Because the aerosolization of each polymer solution generates the same number of droplets, the aerosol number concentration will be higher than during the aerosolization of a mixed polymer solution.The nozzle temperature, in this case, can be categorized in three different regimes - 1) temperature lower than the melting point of both the polymers (Tnozzie < Traeitmg,pi and Tmeiting,P2), 2) temperature higher than the melting point of Pl but lower than the melting point of P2 (Tmeiting,Pi < Tnozzie < meiting,P2), and 3) temperature higher than the melting point of Pl and P2 (Tnozzie > Tmeiting,pi and Tmeiting,p2). Depending on the temperature of the nozzle, the polymers will deposit on the printing surface as discrete particles or molten material droplets and will solidify. In the first regime, solid particles of Pl and P2 will deposit on the surface, forming a porous structure. Furthermore, the concentration of each polymer solution will influence the particle size, consequently, the porosity of the structure. In the second regime, unlike the case of composite polymer particles, here, Pl will undergo melting, whereas P2 will deposit as dry solid particles. Pl will distribute within the space around P2 particles upon printing and function as an adhesive to connect solid P2 particles. Consequently, a denser structure will form compared to the first regime, and the porosity can be modified by controlling the composition ratio of Pl and P2. A higher amount of Pl will thoroughly occupy the pores and densify the structure. Finally, at a very high temperature in the third regime, both the polymers will melt, deposit, and solidify independently, producing a dense structure.Other important parameters in this strategy are the total concentration of the polymers in the solution and P1 / P2 concentration ratio entering the printer nozzle. This strategy provides more flexibility to vary the concentration of each polymer, which can be controlled by polymer concentration in the initial solution and the mass concentration of polymer particles entering the nozzle. Further, the particle mass concentration is a function of flow rate and the numberconcentration of particles generated from the nebulizer. Overall, fundamental parameters that could be controlled easily are the concentration of polymers in solution, aerosol flow rate, particle number concentration, along with nozzle temperature, and printing surface temperature. Correlations between printing characteristics (morphology, porosity, composition, and distribution of each polymer in the structure) and process parameters can be developed.Figure 6 shows a schematic view of a system for A3DP according to an embodiment of the subject invention. Figure 6 shows with dotted lines the example where two different polymer solutions are used (the top solution and then the section polymer solution), as well as the example where a metal oxide precursor solution is used in combination with one or more polymer solutions to make a polymer-metal composite.In an embodiment, A3DP printing can be used to print composites of a soluble low melting point material and a non-soluble high melting point material. For example, A3DP can be used to print a composite of a polymer and a material comprising a metal or a metal oxide. As an example, a composite of PEG and TiCh can be printed using A3DP. This is shown in Figure 6.Metal oxide particles can be synthesized through an aerosol process using a precursor. In the synthesis process, the precursor can be vaporized or nebulized, and the vapors can be passed through a furnace (e.g., a high-temperature tube furnace (500 - 1000 °C)) with a carrier gas. The precursor decomposes in the furnace to form metal or metal oxide particles.Introducing a non-soluble material into the solution modifies several aspects, such as the preparation of stable dispersion and consideration regarding particle melting. In order to ensure a stable dispersion of metal or metal oxide, surface modifications employing both physical and chemical means can be employed, utilizing polymeric stabilizing agents (including, e.g., PEG), to prevent or inhibit their agglomeration. The metal oxide particles do not need to melt, but rather the polymer can melt and be utilized as an adhesive between the metal-containing (e.g., TiCh) particles. Printing a metal oxide-polymer composite can be accomplished through two distinct approaches by altering the aerosol generation technique 1 ) preparing a stable solution of the metal oxide and polymer mixed together and then aerosolizing the mixed solution and / or 2) synthesizing metal oxide particles online, in-flight mixing with PEG particles before introducing them in the printer. These procedures will result in different material properties (morphology and material distribution in the structure) depending on the melting and cooling dynamics of the polymers, metal oxide / polymer composition ratio, and metal oxide particle size.Aerosolizing a mixed solution of metal oxide and polymer represents a straightforward approach to printing a metal oxide-polymer composite. However, due to the solvent evaporation that occurs after deposition on the surface, it is not feasible to print metal-oxide particles synthesized in situ. Upon aerosolization of a mixed solution, the droplet will contain metal oxide particles surrounded by solubilized polymer, which upon solvent evaporation, will result in polymer-coated metal oxide particles. As the particles pass through the nozzle, their characteristics is contingent upon the nozzle temperature. The polymer will either melt or not, and the particles will deposit on the printing surface to develop the structure.Nozzle temperature, printing surface temperature, total concentration of the solution, ratio of metal oxide to polymer concentration entering the nozzle, and metal oxide particle size are crucial parameters. For example, at nozzle temperature below the melting point of the polymer, solid particles of PEG-coated TiCh will deposit, yielding a highly porous structure. Conversely, when the nozzle temperature is enough to melt the polymer, a dense structure with PEG distributed in the space around TiCh particles will result, in which molten PEG aids in the adherence of TiCh particles. The porosity of the structure can be controlled by adjusting the concentration ratio of metal oxide to polymer, as the arrangement of solid particles gives rise to pores, which the molten polymer attempts to fill before solidification occurs. Moreover, the size of the metal oxide particles will impact the morphology, particularly at higher metal oxide concentrations.With respect to aerosolizing the metal oxide and polymer separately and in-flight mixing of particles, this second approach for printing a metal oxide-polymer composite involves the online synthesis of metal oxide particles using the aerosol process, followed by in-flight mixing of the metal oxide and polymer particles before introducing them into the printer, as depicted in Figure 6. The entire process, from the synthesis of metal oxide and polymer particles to printing their composite, can be a continuous process.Because only the polymer undergoes melting during the printing of metal oxide-polymer composites, the nozzle temperature, particle size, and metal oxide / polymer concentration ratio can affect the porosity of the structure. Lower temperatures will yield structures with higher porosity, while a higher temperature that can effectively melt the polymer will lead to the formation of a dense and precise structure. The size of the particles can be controlled. Larger particles and aggregate result in large pores in the structure compared to individual small particles. Moreover, at a larger TiC / PEG ratio, a higher number of particles will create a moreporous structure. These parameters will directly influence the properties of the structures. The structures can be characterized to determine the final composition and distribution of TiCh and PEG within the structure, and this can be correlated with the initial composition, particle size, and other parameters.The high-resolution, simple, and affordable A3DP systems and methods of embodiments of the subject invention can be advantageous for many industries. For example, in manufacturing, A3 DP can streamline the production of complex parts with intricate geometries and reduce the need for assembly and post-processing. This will improve manufacturing processes, enhance product performance, and reduce material waste. The versatility of the A3DP technique allows printing of a variety of materials and integration with several material synthesis processes (spray-drying, spray pyrolysis, flame synthesis of particles, and electrospray), which will accelerate novel material development, including composite and functionally graded materials. In healthcare, micro / nano-scale drug delivery vehicles (e.g. nanorockets, Janus micromotors) and micro / nano robots for precision surgery (e.g. microdrills, micro-grippers, and microcannons) allow doctors to perform a variety of minimally invasive procedures in difficult- to-access locations with high precision and control. Environmental microrobots that can perform remediation tasks in hard-to-reach positions, such as surveillance of pollution, purification of water bodies, and elimination of explosives and heavy metal ions, will benefit from A3 DP technology. In the energy sector, this high-resolution 3D printing will enable exploration of efficient designs for wind turbines, designs for efficient light trapping in solar cells, and fabrication of highly efficient perovskite solar cells on the complex surface of silicon solar cells. The increasing demand for high-performance and miniaturized electronics requires electronics to have a 3D form occupying z-axis space. Compared to the traditional photolithography techniques for fabrication, high-resolution and simple 3D printing will accelerate the advancement in these areas.When ranges are used herein, combinations and subcombinations of ranges (e.g., subranges within the disclosed range), as well as specific embodiments therein, are intended to be explicitly included. When the term “about” is used herein, in conjunction with a numerical value, it is understood that the value can be in a range of 95% of the value to 105% of the value, i.e. the value can be + / - 5% of the stated value. For example, “about 1 kg” means from 0.95 kg to 1.05 kg.A greater understanding of the embodiments of the subject invention and of their many advantages may be had from the following examples, given by way of illustration. The following examples are illustrative of some of the methods, applications, embodiments, and variants of the present invention. They are, of course, not to be considered as limiting the invention. Numerous changes and modifications can be made with respect to embodiments of the invention.EXAMPLE 1A3 DP according to embodiments of the subject invention was used to print a thermoplastic polymer, PEG. PEG was considered due to its good solubility in water, low melting point (melting point = 55 °C), and numerous applications, especially for microdevices in the biomedical field. A solution of PEG in water (100 mg / ml) was aerosolized using a nebulizer, which generated droplets ranging from 1 pm to 5 pm in size and yielded particles in size range from 450 nm to 2.5 pm upon solvent evaporation. The solvent was captured in the diffusion dryer, and dry particles were fed into the printing nozzle. A simple orifice nozzle with a throat diameter of 400 pm was used for printing. The particle residence time of particles within a 400 pm nozzle was 7.37 milliseconds (ms), while the approximate time for particle melting at 100 °C nozzle temperature was about 22 microseconds (ps), allowing the particles to melt inside the nozzle. The printing surface temperature was kept at 30 °C, and as the particles deposited on the printing surface, they solidified. Consequently, layer-by-layer deposition of these particles created a 3D structure. Figures 9a-9d show the PEG as printed.The A3DP process involves several process parameters that influence both the underlying physics of the process and the properties of the printed structures, such as resolution, precision, morphology, and other application-specific properties. These parameters encompass both the aerosol process parameters and the printing parameters. The aerosol process parameters are material properties, material concentration in the solution (which affects the particle size), flow rate, and particle number concentration generated from the nebulizer. The printing parameters are nozzle temperature, printing surface temperature, nozzle-to-printing surface distance, nozzle design, and nozzle size (throat diameter).The most crucial parameters for printing include the nozzle temperature and the printing surface temperature. Nozzle temperature determines the melting of particles; Figures 2a-2c depict the microstructure of a line of PEG printed at different nozzle temperatures. If the nozzletemperature is insufficient to completely melt the PEG, spherical solid or partially molten particles deposit, resulting in a porous structure (Figure 2a). Conversely, a very high temperature (Figure 2c) leads to complete particle melting and an elevated temperature of the molten particle, delaying their solidification time. In this case, the incoming gas flow from the nozzle deforms the structures. Achieving an optimal nozzle temperature is crucial for printing precise structures with specific morphology and density. These observations also demonstrate the potential of the A3DP process in manufacturing structures with diverse morphologies. Similarly, printing surface temperature affects the material solidification upon printing and particle deposition supported by thermophoretic force; therefore, the printing surface temperature lower than the nozzle temperature but higher than the room temperature is required to adhere and solidify the material on the surface.Aerosol process parameters are other important sets of parameters that affect the printing properties. For example, the aerosol flow rate directly influences the nozzle temperature required to melt the particles and the velocity of the particle toward the printing surface; hence affects the printing properties - resolution, precision, and morphology. Additionally, it also affects the rate of material supplied to the printer. Currently, the aerosol process for particle synthesis and printing process for their subsequent printing are independent, which means the amount of aerosol supplied does not change according to the desired printing parameters as happens in traditional printing techniques. Additionally, while the aerosol process is continuous, printing may require intermittent pauses in material flow as the nozzle travels between different locations on the printing surface.EXAMPLE 2A3DP according to embodiments of the subject invention was used to print a thermoplastic polymer, PVDF (melting point = 177 °C). DMF was used as the solvent. The process was performed at different nozzle temperatures, with the results shown in Figures 21 - 21c. Referring to Figures 21a - 21c, a similar effect was observed as in Example 1 in Figures 2a - 2c. At a low nozzle temperature, the microstructure is comprised of spherical particles that are very little sintered together. As the temperature increases, the sintering between the particles increases. Heating and cooling dynamics depend on the materials properties and particle size.EXAMPLE 3A3DP according to embodiments of the subject invention was used to print a composite of PEG and lignin. The process shown in Figure 6 was performed using the second polymer solution. Figures l ib and 12 show images of the printed composite material.EXAMPLE 4A3 DP according to embodiments of the subject invention was used to print a graded composite of PEG and lignin. Figures 13 and 14 show images of the printed graded composite material.EXAMPLE 5A3 DP according to embodiments of the subject invention was used to print a composite of PEG and TiCh. The process shown in Figure 6 was performed using the top and bottom solutions shown on the lefthand side. TiCh particles can be first synthesized (e.g., through an aerosol process using titanium(IV) isopropoxide (TTIP) precursors). In the synthesis process, TTIP precursors can be vaporized, and the vapors can be passed through a high-temperature tube furnace (500 °C - 1000 °C) with a carrier gas. The precursor can decompose in the furnace to form metal oxide particles. Figure 18 shows images of the printed composite material, which was obtained via A3 DP according to embodiments of the subject invention using purchased TiCh nanoparticles, which were mixed with PEG solution and aerosolized.EXAMPLE 6A3 DP according to embodiments of the subject invention was used to print a composite of PEG and PVDF and a composite of PEG and lignin. The printed materials are shown in Figures 22a - 22f. The process shown in Figure 6 was performed using a mixed solution of the two polymers.For this example, the composite materials were easily printed by aerosolizing a mixed solution of multiple materials (i.e., PEG and PVDF, or PEG and lignin). The nozzle temperature was adjusted such that only one polymer was melted and the molten polymer functioned as an adhesive between the unmelted polymer. When adding a small amount of PDVF into the PEG solution, the particle was composed of a homogeneously distributed PVDF and PEG mixture (see Figures 22a and 22b). The molten PEG might melt the small amount ofPVDF, forming a dense morphology similar to pure PEG. However, at higher PVDF concentrations, the microstructure resembles PVDF particles dispersed in PEG, leading to pore formation due to a high solid particle content compared to molten PEG (see Figure 22c).The other composite was of PEG and lignin, which has a melting point ranging from 200 °C to 500 °C. At low lignin concentrations, the micro structure resembles lignin particles dispersed in PEG as PEG cannot melt lignin. As the lignin concentration increases, more porous structure starts to form (see Figures 22d and 22e).Individual concentration of the components is also important. If both the PEG and lignin concentration were increased while keeping their ratio the same, a fibrous composite is produced, likely due to increased solution viscosity and interactions between lignin and PEG, forming a network structure (see Figures 22d and 22f). This formation is advantageous for producing reinforced polymer composites.EXAMPLE 7COMSOL Multiphysics was used to create a finite element model of the A3DP system that directly relates the process parameters to u, T, and p. The system modeled in COMSOL includes the printing nozzle (see also Figures 16a and 16b), printing surface, and the volume between the nozzle and printing surface. For simulating particle flow, a representative number of particles with lognormal size distribution were introduced to effectively mimic the A3DP while also reducing the computational time and complexity of the simulation. The initial velocity and temperature of the particles are known from the experimental conditions. Particles encountering any surface are considered to be adhered to that specific position on the surface. The time-dependent equations were solved to track the particles at each time step. It is important to note that COMSOL does not include particle-particle interaction such as coagulation; therefore, the equations for particle dynamics were numerically solved, which provided particle size distribution as a function of particle position and time. The result was compared with results for particle trajectory from COMSOL to understand the effect of coagulation.The computational results provide particle trajectory and particle position and temperature at each time step. The particle position can be used to calculate resolution and precision, and the particle temperature can be used to understand the particle melting and solidification in the process. Two dimensionless metrics, focusing ratio (FR) and collection efficiency (CE), were developed, respectively signifying the resolution and the precision. FR isthe ratio of the printed line width to the nozzle throat diameter; line width is the width that contains 90% of the particles that are deposited. In essence, FR represents the printing resolution in x and y dimensions. Resolution is the smallest x, y, and z dimensions that can be printed. CE signifies the percentage of particles in the printer nozzle that is deposited within the desired line width. Therefore, CE relates to the precision in x and y; precision is the exact dimension to be printed in the x, y, and z dimensions. Thus, a high CE and a low FR are desired for achieving high resolution and precision. Process parameters were considered to assess their effect on FR and CE, hence on resolution and precision.The nozzle is a part of the system modeled in the COMSOL, and other parameters can be changed easily in the model. PEG was used as the material. The particle size distribution can be directly measured using aerosol instrumentation in the lab. The flow rate was varied between 100 seem - 1 liter per minute (1pm); nozzle temperature was varied from Tm- 25 °C to Tm+ 100 °C, where Tmis the melting point of the bulk material; printing surface temperature was varied from 30 °C to Tm- 100 °C; nozzle-to-printing surface distance was varied from 0.5 mm to 5 mm; and nozzle throat diameter was varied from 100 pm to 1 mm.A schematic of the nozzle designs considered is shown in Figure 17. Nozzles with sheath gas surrounding the aerosol stream are more effective than those without sheath gas. These designs are primarily distinguished by the diameter of the aerosol nozzle at the intersection with the sheath gas and the length of the nozzle throat. The diameter at the junction of the sheath gas affects the mixing between the aerosol and sheath gas, thereby impacting the achievable resolution. The length of the nozzle throat determines the residence time for the particle. A longer length retains particles at high velocities, which will possibly increase the Saffman force on particles, focusing the particles toward the nozzle centerline. Additionally, for each of these designs, other variables design parameters are the nozzle throat diameter (100 pm - 800 pm) and the half-angle (30° - 60°) of the converging section before the nozzle throat.For each nozzle design, other process parameters were varied, and the flow field, temperature profile, and particle trajectories were considered to gain an understanding of their effect on resolution, precision, and morphology. FR and CE were evaluated to provide an understanding of the resulting printing resolution and precision, which serves as an indicator of efficient nozzles. Figure 18 shows the parameters studied for each nozzle.Figures 19a and 19b show the FR results for the five nozzles shown in Figure 17, and Figures 20a and 20b show the CE results for the five nozzles.It should be understood that the examples and embodiments described herein are for illustrative purposes only and that various modifications or changes in light thereof will be suggested to persons skilled in the art and are to be included within the spirit and purview of this application.All patents, patent applications, provisional applications, and publications referred to or cited herein (including those in the “References” section, if present) are incorporated by reference in their entirety, including all figures and tables, to the extent they are not inconsistent with the explicit teachings of this specification.REFERENCES1. Epicoco, M., Knowledge patterns and sources of leadership: Mapping the semiconductor miniaturization trajectory. Research Policy, 2013. 42(1): p. 180-195.2. 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Claims

CLAIMSWhat is claimed is:

1. A method for aerosol-based three-dimensional (3D) printing, the method comprising: dissolving a first material in a first solvent to give a first solution; atomizing the first solution to produce first droplets comprising the first solvent and the first material; evaporating the first solvent by providing the first droplets to at least one of a dryer and a furnace to leave first particles comprising the first material; feeding the first particles into a 3D printing nozzle; heating the 3D printing nozzle to melt the first particles and give heated particles that are molten or semi-molten; and using the 3D printing nozzle to deposit the heated particles on a substrate, thereby printing a structure using a deposited material, wherein the deposited material comprises the first material or wherein the first material is a precursor of the deposited material.

2. The method according to claim 1, wherein the first solvent is evaporated by providing the first droplets to the dryer.

3. The method according to any of claims 1 -2, wherein the first solvent is evaporated by providing the first droplets to the furnace.

4. The method according to any of claims 1 -3, wherein the dryer is a diffusion dryer.

5. The method according to any of claims 1-4, wherein the furnace is an electric furnace.

6. The method according to any of claims 1 -5, wherein the first material comprises: a) first soluble materials dissolved in the first solvent;b) first suspended nanoparticles dispersed in the first solvent; or c) both a) and b).

7. The method according to any of claims 1-6, wherein the first material is a polymer.

8. The method according to any of claims 1 -6, wherein the first material comprises a metal.

9. The method according to any of claims 1-6, wherein the first material comprises a metal oxide.

10. The method according to any of claims 1-6, wherein the first material comprises a polymer, a metal, a metal oxide, or a combination thereof.

11. The method according to any of claims 1-10, wherein atomizing the first solution to produce the first droplets comprises using a collison nebulizer.

12. The method according to any of claims 1-11, wherein a size of the first droplets is in a range of from 1 micrometer (pm) to 5 pm.

13. The method according to any of claims 1-12, wherein a resolution of the aerosolbased 3D printing is 40 pm or less.

14. The method according to any of claims 1-13, wherein the first solution further comprises a second material different from the first material, wherein the deposited material is a composite material of a third material and a fourth material, wherein the first material is the same as the third material or is a precursor of the third material, and wherein the second material is the same as the fourth material or is a precursor of the fourth material.

15. The method according to claim 14, wherein the second material comprises: a) second soluble materials dissolved in the first solvent; b) suspended nanoparticles dispersed in the first solvent; or c) both a) and b).

16. The method according to any of claims 14-15, wherein the second material is a polymer.

17. The method according to any of claims 14-16, wherein the second material is comprises a metal.

18. The method according to any of claims 14-17, wherein the first material is a polymer and wherein the second material is a metal oxide.

19. The method according to any of claims 1-18, further comprising: dissolving a second material in a second solvent to give a second solution; atomizing the second solution to produce second droplets comprising the second solvent and the second material; evaporating the second solvent by providing the second droplets to at least one of the dryer and the furnace to leave second particles comprising the second material; and feeding the second particles into the 3D printing nozzle, wherein heating the 3D printing nozzle melts the second particles, wherein the heated particles comprises the second material, wherein the deposited material is a composite material of a third material and a fourth material, wherein the first material is the same as the third material or is a precursor of the third material, and wherein the second material is the same as the fourth material or is a precursor of the fourth material.

20. The method according to claim 19, wherein a size of the second particles is in a range of from 450 nanometers (nm) to 2.5 pm.

21. The method according to any of claims 1-20, wherein a size of the first particles is in a range of from 450 nm to 2.5 pm.

22. The method according to any of claims 1-21, wherein the first material is a water- soluble polymer.

23. The method according to any of claims 1-22, wherein the first material is polyethylene glycol (PEG).

24. A system for aerosol-based three-dimensional (3D) printing, the system comprising: a solvent-evaporating device that comprises at least one of a dryer and a furnace; a 3D printing nozzle connected to an exit of the solvent-evaporating device; a tube connecting the 3D printing nozzle to the exit of the solvent evaporating device; a heating element disposed around the 3D printing nozzle and configured to heat the 3D printing nozzle during use; and a platform disposed below an exit of the 3D printing nozzle and configured for 3D printing thereon.

25. The system according to claim 24, further comprising an atomizer configured to atomize a solution to produce droplets to be provided to the solvent-evaporating device.

26. The system according to claim 25, wherein the atomizer comprises a collison nebulizer.

27. The system according to any of claims 24-26, further comprising a container connected to an entrance of the solvent-evaporating device and configured to have droplets contained therein.

28. The system according to claim 27, further comprising a first chamber having the container and the solvent-evaporating device disposed therein.

29. The system according to any of claims 24-28, wherein the solvent-evaporating device comprises the dryer.

30. The system according to any of claims 24-29, wherein the solvent-evaporating device comprises the furnace.

31. The system according to any of claims 24-30, wherein the dryer is a diffusion dryer.

32. The system according to any of claims 24-31, wherein the furnace is an electric furnace.

33. The system according to any of claims 24-32, wherein a resolution of the aerosolbased 3D printing of the system is 40 pm or less.

34. A system for aerosol-based three-dimensional (3D) printing of in situ synthesized materials, the system comprising: a device generating vapors and / or droplets of a precursor of the in situ synthesized materials; a solvent-evaporating device that comprises at least one of a dryer and a first furnace; a high-temperature furnace connected to an exit of the solvent-evaporating device and configured to decompose the precursor; a first tube connecting the high temperature furnace to the exit of the solvent-evaporating device; a 3D printing nozzle connected to an exit of the high-temperature furnace; a second tube connecting the 3D printing nozzle to the exit of the high temperature furnace; a heating element disposed around the 3D printing nozzle and configured to heat the 3D printing nozzle during use; and a platform disposed below an exit of the 3D printing nozzle and configured for 3D printing thereon.

35. The system according to claim 34, further comprising a container connected to an entrance of the solvent-evaporating device and configured to have droplets contained therein.

36. The system according to claim 35, further comprising a first chamber having the container and the solvent-evaporating device disposed therein.

37. The system according to any of claims 34-36, wherein the solvent-evaporating device comprises the dryer.

38. The system according to any of claims 34-37, wherein the solvent-evaporating device comprises the first furnace.

39. The system according to any of claims 34-38, wherein the dryer is a diffusion dryer.

40. The system according to any of claims 34-39, wherein the first furnace is an electric furnace.

41. The system according to any of claims 34-40, wherein a resolution of the aerosolbased 3D printing of the system is 40 pm or less.

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