Method and apparatus for achieving high electrospray deposition efficiency on low surface area targets - Patents.com

Abstract

A method comprising: establishing an electric field (210) in an electrospray deposition device (100B); and emitting, in the electric field, a spray of a medium (114) containing a payload material (116A) from an emitter (104) toward a conductive target (132) disposed on an insulated conductor (200); disposing a charged payload material (116BE) on the insulated conductor; and establishing electric field lines (130BE) in the electric field between the emitter and the charged payload material on the insulated conductor to stabilize the electric field and carry the spray of the medium between the emitter and the target to the target.

Description

[Technical field]

[0001] This application claims the benefit of U.S. Provisional Patent Application No. 63 / 269,496, filed March 17, 2022, which is incorporated herein by reference.

[0002] STATEMENT REGARDING FEDERALLY ASSISTANT DEVELOPMENT This invention was made with Government support under Grant No. 1911518 awarded by the National Science Foundation. The Government has certain rights in this invention. [Background technology]

[0003] Micro / nanoscale conformal coatings can be applied in either molecular or condensed states. Molecular deposition techniques such as electrodeposition, vacuum deposition, atomic layer deposition, or chemical vapor deposition generally require either a fluid bath or high vacuum to apply and may also require high temperature precursor treatments. This counterbalances cost-effectiveness accounts and limits the size of components that can be coated. Condensation deposition techniques such as spray coating, dip coating, spin coating, and brush or blade coating are challenging for 3D surfaces and lead to capillary or shadowing effects.

[0004] The widespread use of additive manufacturing is growing exponentially. Industries using additive manufacturing include: aerospace, agriculture, architecture, engineering, construction, automotive, consumer products, education, high tech, industrial equipment, biomedical implants, prosthetics, dental, jewelry, and electronics. A variety of industries utilize additive manufacturing to design and build prototypes, tooling, and end-use parts. Existing additive manufacturing techniques rely on a material ejection device to direct the printed material to a desired target location, and do not provide any mechanism to redirect the material away from its ejection vector toward uncoated areas of the target location. Furthermore, according to existing methods, if a 3D printed component is coated, it is done in an entirely different process. Summary of the Invention

[0005] Various embodiments relate to methods and apparatus for achieving high electrospray deposition efficiency on small area targets. The method may include establishing an electric field in an electrospray deposition device, emitting a spray of a medium containing payload materials from an emitter in the electric field toward a conductive target disposed on an insulated conductor, disposing the charged payload material on the insulated conductor, and establishing field lines in the electric field between the emitter and the charged payload material on the insulated conductor to stabilize the electric field and carry the spray of medium between the emitter and the target to the target.

[0006] According to various embodiments, the method may further include depositing the charged payload material onto the insulated conductor by directing an initial overspray of the medium containing the charged payload material onto the insulated conductor.

[0007] According to various embodiments, the method may further include ensuring that, when an electric field is present, insulating material on the insulated conductor causes electric field lines to form between the charged payload material on the insulated conductor and the conductor of the insulated conductor.

[0008] According to various embodiments, the method may further include maintaining the electrical conductor at a relatively lower or higher potential difference with the emitter than with the target.

[0009] According to various embodiments, the method may further include grounding the electrical conductor.

[0010] According to various embodiments, the method may further include ensuring that the electric field lines between the emitter and the charged payload material on the insulated conductor completely surround the target.

[0011] According to various embodiments, the method may further include directing the spray of the medium using the electric field lines between the emitter and the target.

[0012] According to various embodiments, the method may further include applying a mask to the portion of the target.

[0013] According to various embodiments, the method may further include aligning the spray of medium to the electric field lines between the emitter and the target and: 1) isolating the electric field lines between the emitter and the unmasked portion of the target from other electric field lines; 2) assisting in concentrating the spray of medium to the electric field lines between the emitter and the unmasked portion of the target; and 3) thereby ensuring that the electric field lines between the emitter and the mask are less dense than the electric field lines between the emitter and the charged payload material on the insulated conductor to concentrate the spray of medium to the unmasked portion of the target.

[0014] According to various embodiments, the method may further include ensuring that the conductor mass of the insulated conductor is at least 1,000 times the mass of the target.

[0015] According to various embodiments, the method may include establishing an electric field between an emitter and an insulated conductor in an electrospray deposition apparatus, positioning a target on the insulated conductor, emitting a spray of medium toward the target, and allowing an initial overspray of the spray to reach the insulated conductor.

[0016] According to various embodiments, the method may further include allowing the initial overspray to reach a mask on the target.

[0017] According to various embodiments, the insulated conductor establishes an insulator profile as seen by the emitter, and the method further includes ensuring that the target is located entirely within the insulator profile as seen by the emitter.

[0018] According to various embodiments, the method may further include maintaining a distance of at least one centimeter between the target and the entire perimeter of the insulator profile as viewed by the emitter.

[0019] According to various embodiments, the insulator profile establishes an insulator profile area, the target establishes a target profile as seen by the emitter, the target profile establishes the target profile area, and the method further includes ensuring that the insulator profile area is at least 100 times the target profile area.

[0020] According to various embodiments, the method may further include ensuring that the conductor mass of the insulated conductor is at least 1000 times the mass of the target.

[0021] Various embodiments of the method may include subjecting a stream of media from a capillary to a relatively high electric field to form a spray of droplets of the media, directing the spray towards a target disposed on an insulating surface disposed on a conductor maintained at an electrical potential difference with the media in the capillary, causing an initial overspray of the spray, and ensuring that the initial overspray reaches onto the insulating surface adjacent the target.

[0022] According to various embodiments, the method may include subjecting a stream of media from a capillary to a relatively high voltage to form a spray of droplets of the media, directing the spray towards a target disposed on an insulating surface disposed on a conductor maintained at a relatively low voltage, causing initial overspray of the spray, and ensuring that the initial overspray reaches the insulating surface adjacent the target.

[0023] According to various embodiments, the method may further include ensuring that the initial overspray surrounds the entire perimeter of the target.

[0024] According to various embodiments, the method may further include ensuring that the overspray is located within an electric field generated by the relatively high potential difference.

[0025] According to various embodiments, the potential difference arises from a grounded object.

[0026] According to various embodiments, the method may further include applying a pre-spray to the target and the insulating surface to dissipate or apply an electric charge.

[0027] According to various embodiments, the method may further include focusing the spray using a focus ring positioned around the spray.

[0028] According to various embodiments, the apparatus includes an electrospray deposition emitter configured to generate a spray of a medium toward a target and to be maintained at or above a first electric potential magnitude, and an extractor target configured to be maintained at a potential magnitude lower or higher than the first electric potential magnitude and to define a support surface, an insulating material on the support surface, and a charged payload material disposed on the support surface.

[0029] According to various embodiments, the first electrical potential is configured to generate an electric field, the electric field being sufficient to cause electric field lines to form between the charged payload material and the electrical conductor.

[0030] According to various embodiments, the electrical conductor is grounded.

[0031] According to various embodiments, the apparatus may further include a focus ring configured to constrict the spray radially inward as the spray passes through the focus ring.

[0032] According to various embodiments, the apparatus may further comprise a controller configured to control at least one of the first voltage potential and the flow rate of the medium.

[0033] According to various embodiments, the apparatus includes a capillary configured to pass and release a flow of medium therefrom; an extractor target including an electrical conductor configured to define a support surface facing the capillary and an insulating material on the support surface; and a high voltage source configured to generate an electric potential that will cause the flow exiting the capillary to disperse into a spray of charged droplets directed toward the support surface, and configured to generate an electric field between the capillary and the target on the support surface at different electric potentials, where the electrical conductor of the extractor target is configured to be maintained at a lower electric potential than the relatively high voltage generated by the high voltage source.

[0034] According to various embodiments, the apparatus may be further configured to cause an initial overspray of the spray to reach a support surface, and the electric field is configured to generate electric field lines between the capillary and media from the overspray disposed on the support surface.

[0035] According to various embodiments, the apparatus may further comprise a controller configured to control generation of at least one of the electric field and the flow rate of the medium.

[0036] According to various embodiments, the apparatus includes a capillary configured to pass and release a flow of medium therefrom, an extractor target including an electrical conductor configured to define a support surface facing the capillary and an insulating material on the support surface, and a high voltage source configured to disperse the flow exiting the capillary into a spray of charged droplets directed toward the support surface and configured to generate an electric field between the capillary and a target on the support surface at a relatively low voltage, where the electrical conductor of the extractor target is configured to be maintained at a lower potential than the relatively high voltage.

[0037] According to various embodiments, the apparatus may be further configured to cause an initial overspray of the spray to reach a support surface, and the electric field is configured to generate electric field lines between the capillary and media from the overspray disposed on the support surface.

[0038] Further aspects, features, and advantages will become readily apparent from the following detailed description, by way of illustration only of certain specific embodiments and implementations, including the best mode contemplated for carrying out the invention. Other embodiments are also capable of other different features and advantages, and its several details can be modified in various obvious respects, all without departing from the spirit and scope of the invention. Accordingly, the drawings and description should be regarded as illustrative in nature, and not as restrictive.

[0039] Electrospray deposition (ESD) is a common thin-film coating technique that can generate charged droplets at the micro- and nanoscale that can be used in medicine, such as for drug delivery purposes and medical implants. In ESD, electrostatic forces are applied to a solution, which then disperses the charged droplets filled with the material to be deposited. One mode of ESD is self-limiting electrospray deposition (SLED). In SLED, the material arrives on the target as a dry spray, carrying a charge that eventually begins to self-repel over time. The charged spray is redirected to uncoated areas such that manipulation of electrostatic repulsion, hydrodynamic forces, and evaporation kinetics can be employed to conformally coat 3D structures with microcoatings. The coatings produced are hierarchical, with either nanoshell, nanoparticle, or nanowire microstructures, and can be smoothed by further post-processing. SLED can be an alternative to dip or conventional spray coating. The advantage can be the possibility of much higher material utilization. Many studies have postulated high efficiency in ESD, but rarely quantified. Here we show how local "charge landscapes" can be engineered to yield SLED coatings approaching 100% deposition efficiency, including biocompatible polymers, proteins, and bioactive small molecules, on microneedle arrays (MRAs) and other complex substrates for relevant therapeutics and model materials.

[0040] Electrostatic spraying is an efficient coating method that has traditionally been used in the automotive and agricultural industries to coat large surfaces (#93). More recently, a related technique, electrospray deposition (ESD), which is primarily utilized for analytical measurement, has expanded significantly in the manufacturing world. Due to the high controllability of the thin-film coatings produced by ESD, it has been utilized where micro- and nano-scale coatings are required. As an example, ESD has been able to produce organic photovoltaics (OPVs) and achieve high power conversion efficiency through optimization of solvent evaporation (#94, #95). ESD provides a further avenue for the rapid and easy fabrication of organic light-emitting diodes, which can then meet the demand in the full-color display industry (#96). Due to the ease of thin-film fabrication, ESD also offers an alternative thin-film coating method in biotechnology. As mentioned above, altering ESD parameters allows for the manipulation of droplet morphology, and more specifically, droplet diameter. Nanoparticles (NPs) are important in the biomedical field for drug delivery applications, and NPs can be rapidly generated via ESD. Such applications of NPs include electrospraying chitosan NPs (#97) and collagen NPs (#98) as drug delivery carriers (#97, 98) and spraying polycaprolactone NP layers to control alignment and growth patterning for cell culture (#99). Collagen / calcium phosphate coatings on metal implants have been investigated to promote stronger chemical bonds between the implant and native bone tissue compared to metal and native tissue alone (#100). Metal implants were coated with bioglass, composed of silicon dioxide, calcium oxide, and phosphorus pentoxide, by ESD with a similar aim to promote osseointegration of the implant (#101). ESD can also safely deposit protein nanoparticles while still demonstrating bioactivity after spraying (#102, 103).

[0041] By applying a high electric field on a dilute solution, monodisperse charged droplets emerge from the needle tip and move towards a grounded target. (#44, #104, #105). The high electric field induces shear forces on the solution, causing it to break up into droplets reaching the micro- and nano-scale. More notably, the cone-jet mode of spraying maintains a Taylor cone at the tip of the nozzle, stabilized by the competing interplay between surface tension and Coulombic forces. (#104).

[0042] The droplet size resulting from the cone-jet mode is a result of the solution properties in addition to its flow rate (#44, #104, #106, #20):

[0043]

number

[0044] where α is a constant related to the dielectric constant of the fluid, Q is the flow rate, ε is the dielectric constant of a vacuum, ρ is the density of the solution, γ is the surface tension of the solution, σ is the conductivity of the solution, and d is a relatively small diameter that only operates at low flow rates.

[0045] In a stable cone jet, or even in the more chaotic but easier to stabilize multi-jet mode, ESD has several advantages compared to other conventional methods of thin film coating and mechanical or acoustic atomizers. First, concentrations are typically limited to dilute solutions, but by using monomeric or other transforming materials as the spray material, higher concentrations approaching 100% active material can be utilized. In addition, many materials can be deposited, including particles, (poly)peptides, sugars, (poly)nucleic acids, polymers, and any other material that can be easily dispersed in low viscosity fluids. Flow rates can vary from uL / h to ~100mL / h, depending on several techniques available to enhance the flow rate, including multiplexing (i.e., using an array of needles) to the use of specially designed flow tips. Spraying can be performed in a variety of environments, including vacuum, and can be regulated by control of the ambient humidity and temperature. Stimuli can be applied to the airborne droplets, including light (e.g., ultraviolet light), additional induced electric fields, magnetic fields, and sound fields, which are used to induce chemical reactions. In addition to droplet diameters as small as 100 nm, relatively monodisperse droplets can be achieved. Furthermore, charged droplets can obtain higher deposition efficiencies compared to sprays using uncharged droplets due to the non-inertial droplets following the electric field lines to the grounded target. (#105, #106). For this reason, ESD (similar to electrostatic spraying) is considered to be a very efficient deposition method with predicted efficiencies approaching 100%. However, this same advantage can also lead to reduced efficiency due to self-limiting effects. Here, self-limiting refers to an experimental scenario in which the accumulation of charge by ESD and the lack of dissipation of this charge leads to the formation of a repulsive field that prevents further spraying in that area. (#107) described two consequences of these effects: (1) when a particular target area receives an excess of undissipated charge, the spray will either become unstable or find other grounded targets in the spray chamber, and (2) non-conductive materials placed on top of the grounded target will rapidly accumulate excess charge and begin to repel the spray.(#107).A further issue is the stability of the spray, as any electric field generated by charge accumulation at the target will reduce the effective potential difference between the spray needle and the target, ultimately destroying the conditions necessary for the formation of a stable cone-jet spray mode. (#106).The accumulation of charge by insulating surfaces was recently quantified by Zhu and Chiarot, who demonstrated that the repulsive electric field can remain at the surface for an experimentally significant time. (#108).Our work has catalogued how these self-limiting effects can be exploited to conformally coat complex 3D objects, provided certain conditions of the spray solution are met. (#44,#104,#109).Specifically, the spray solution must arrive at the spray target as a non-conductive glass-like material. This regime is called self-limited electrospray deposition (SLED).

[0046] More generally, the self-limiting effect is believed to apply to a larger family of ESD techniques in which additional charged or high-voltage elements are incorporated to statically or dynamically modify the electric field lines or "charge landscape" of the spray. The most universal approach is the use of guard rings, whereby a more homogeneous electric space is created in the interelectrode region. Recent studies have demonstrated the effectiveness of these rings using computer simulations, resulting in a more stable Taylor cone-jet mode (#110). An intermediate voltage is applied to the guard ring to extract or focus the spray plume. In the former case, the ring is placed close to or even behind the needle tip to widen the plume. In the latter case, the ring is placed in front of the needle tip, where the intermediate voltage perturbs the space potential, forcing the spray into a central, reduced area (#85,#86,#110). These can be considered as far-field means of controlling ESD. These methods can provide high efficiency when the characteristic size of the target is larger than the spray plume. For example, Morozov et al. employed a far-field focusing approach to obtain 79±7% efficiency in quartz crystal microbalance measurements of protein sprays (#103). Near-field approaches to controlled deposition also exist, specifically using insulating materials placed directly above the sample to first accumulate charge and then focus the spray by modifying the charge landscape. In these near-field methods, the spray plume is most commonly larger than the characteristic size of the template, and while a high degree of control of the spatial positioning of the deposited material may be obtained, the efficiency of these sprays has only been evaluated to a limited extent and can be expected to be lower than when larger targets are utilized. In fact, the only report of deposition efficiency in near-field templates known to us comes from a recent study by Kingsley et al., who showed that for even more macroscopic (3 mm thick) insulating masks, deposition efficiencies of less than 5% are reported using SLED-compatible materials.26. (#77) All additional materials apparently found other grounded targets in their spray chambers.

[0047] Here, we investigated whether it is possible to manipulate the charge landscape to efficiently coat targets smaller than the characteristic plume size by manipulating the charge landscape. If this is possible, ESD could potentially be used as an alternative precision coating to two more established techniques, dip coating and inkjet printing. Dip coating is a highly controlled means of depositing films down to the nanoscale, but requires a stationary reservoir of virgin material and precise mechanical control of the object being coated. This is especially true when only specific portions of the target are to be coated, such as the needle tip. Furthermore, when multiple layers are required, a lengthy drying process between coats may be required. (#112,#113). Inkjet printing can target specific portions of a target with submicron spatial resolution through the use of a piezoelectric stage, but this precision comes at the expense of it being a continuous process requiring expensive positioning equipment. Furthermore, geometries above the "2.5D" complexity cannot be targeted by the line-of-sight nature of the jet, and capillary and gravity flow effects can lead to coating undesired portions of the sample. 27. In assessing whether ESD could be a viable alternative to these methods, we decided to focus on biologically relevant materials where material cost can often be a significant driving factor. To do this, we selected as model materials the small molecule trehalose used as a matrix material, the therapeutic small molecule GLS-1027, the biocompatible glassy polymer poly(vinylpyrrolidone) (PVP), the polymer melt poly(ethylene glycol) (PEG), and the protein complex trehalose-stabilized horse radish peroxidase (HRP). These are merely examples of materials that may be used and are not an exhaustive list of materials or categories of materials that may be used.Of these, it is noted that PVP and HRP (and thus their complexes) are SLED coatings, i.e., they are expected to rapidly accumulate repulsive charges. As model geometries, we primarily employ steel microneedle arrays (MNAs) as 3D surfaces with total surface areas orders of magnitude smaller than the plume size. We also use small silicon tips (~1 cm) as another exemplary geometry. 2 ) was employed, but many other geometries commensurate with or smaller than the characteristic size of the spray plume can be employed. This includes complex 3D surfaces with re-entrant geometries, especially when the spray is SLED in nature. Through image processing, the surface area of ​​the MNA is found to be ~5 cm2 compared to that of a non-SLED sample at the same distance. 2 Compared to the wafer spot size of ~0.2 mm 2 In addition to meeting the criteria of this study, the MNA was determined to be technically relevant for dermal drug delivery (#112, #113).

[0048] It is a common assumption (shown diagrammatically in FIG. 5A) that an efficient spray should (1) start from a relatively "blank" state, unaffected by previous sprays, (2) contain no alternate targets, (3) utilize a focus ring, and (4) have a large extractor ground (buried extractor target) located behind the target from the perspective of the spray. The first three points have been vindicated in the discussion above, and the use of an extractor ground serves a similar purpose to the extractor ring, stabilizing the spray by providing a persistent target. In addition, humidity was kept low for all sprays to maximize the effect of the deposited charge and minimize any post-deposition effects, which has previously been shown to amplify self-limiting effects in ESD (#115).

[0049] The results showed that engineering the charge landscape to focus and stabilize the spray can enable highly efficient coating for all investigated materials and deposition rates, with the exception of low-viscosity melts, which were removed from the target by post-deposition kinetics. This points out that ESD with engineered charge landscapes is a promising alternative or synergistic addition to other coating methods. [Brief description of the drawings]

[0050] Embodiments are illustrated by way of example, and not by way of limitation, in the figures of the accompanying drawings and in which like reference numerals refer to similar elements and in which:

[0051] [Figure 1] 1 illustrates a schematic diagram of an exemplary electrostatic deposition process. [Diagram 2] 1 illustrates a schematic of an exemplary electrostatic deposition process disclosed herein. [Diagram 3] 3 shows a schematic diagram of the electrostatic deposition process of FIG. 2 taken along line AA of FIG. 2. [Figure 4] 1 illustrates a schematic representation of an alternative electrostatic deposition process. [Figure 5A] 1 illustrates a schematic representation of an alternative electrostatic deposition process. [Figure 5B] 13 illustrates a schematic diagram of another alternative electrostatic deposition process. [Figure 6] 1 is a chart showing exemplary results of various coating processes. [Figure 7A] 1 is a chart showing deposition efficiency without any specific modifications. [Figure 7B] 1 shows an exemplary embodiment of a bare microneedle array. [Figure 7C] An exemplary embodiment of an unmasked trehalose-sprayed microneedle array is shown. [Figure 7D] An exemplary embodiment of a trehalose-sprayed microneedle array without insulation on the focus ring or buried extractor target is shown. [Figure 7E] An exemplary embodiment of a trehalose-sprayed microneedle array with all augmentations is shown. [Figure 7F] An exemplary embodiment of a trehalose-sprayed silicon chip is shown. [Figure 7G] An exemplary embodiment of a trehalose-sprayed microelectrode pattern is shown. [Figure 7H] 1 is a chart showing exemplary deposition efficiencies for different substrates. [Figure 8] 8A and 8B show an exemplary embodiment of a self-limiting electrospray deposition (SLED) process. [Figure 9] 9A and 9B are charts showing the results of a self-limiting electrospray deposition (SLED) process using DNA alone and DNA with the addition of trehalose. [Figure 10A] 1 is a chart showing processing results of various electrospray deposition processes. [Figure 10B] An exemplary embodiment of a silicon maskless microneedle array of the type used in the chart of FIG. 10A is shown. [Figure 10C] An exemplary embodiment of a microneedle array with a silicon mask of the type used in the chart of FIG. 10A is shown. [Figure 11] 11A-11C show an exemplary embodiment of selective electrospray deposition (SLED) onto a three-dimensional object. [Figure 12] 12A-12C show an alternative exemplary embodiment of selective electrospray deposition (SLED) onto a three-dimensional object. [Figure 13] 1 is a chart showing the results of selective electrospray deposition (SLED) processing. [Figure 14A] 1 shows selective electrospray deposition (SLED) on a small target. [Figure 14B] 1 is a chart showing dewetting width and spray height. [Figure 15]15A-15D compare microneedle arrays coated with various coating techniques. [Figure 16] Figure 16A is an exemplary embodiment of a microneedle array subjected to various coating techniques with various compositions, and Figures 16B and 16C are charts showing the process results of the coatings on the microneedle array of Figure 16A. [Figure 17] Figure 17A shows DNA delivery using electrospray deposition. Figures 17B and 17C show the results of DNA delivery from Figure 17A. [Figure 18] 18A and 18B show the results of DNA delivery applied via self-limiting electrospray deposition (SLED). [Figure 19] 1 is a chart of wavelength vs. absorbance relevant to UV-Vis determinations. [Figure 20] 1 shows a calibration curve for 0.0025 wt % Rhodamine B in water in a chart of the amount of Rhodamine versus the integrated area of ​​the Rhodamine peak relevant for UV-Vis determination. [Figure 21] FIG. 21A and FIG. 21B show the high performance liquid chromatography results for the control and GLS-1027 samples in respective charts of duration versus height. [Figure 22] 13 is a block diagram illustrating a computer system 1300 upon which embodiments of the present invention may be implemented. [Diagram 23] 14 illustrates a chipset 1400 in which embodiments of the present invention may be implemented. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0052] In the following description, for purposes of explanation, numerous specific details are set forth in order to provide a thorough understanding of the present invention. However, it will be apparent to those skilled in the art that the present invention may be practiced without these specific details. In other instances, well-known structures and devices are shown in block diagram form in order to avoid unnecessarily obscuring the present invention.

[0053] Although the numerical ranges and parameters specifying broad ranges are approximations, the numerical values ​​specified in the specific non-limiting examples are reported as precisely as possible. However, any numerical value inherently contains certain errors necessarily resulting from the standard deviation found in the respective testing measurements at the time of writing. Moreover, unless otherwise clear from the context, numerical values ​​presented herein have an implied precision given by the least significant digit. Thus, the value 1.1 means a value from 1.05 to 1.15. The term "about" is used to indicate a broader range centered on a given value, and unless otherwise clear from the context, it means a broad range around the least significant digit, such as "about 1.1" means a range from 1.0 to 1.2. When the least significant digit is unclear, the term "about" means a factor of 2, for example, "about X" means a value ranging from about 0.5X to 2X, for example, about 100 means a value ranging from 50 to 200. Moreover, all ranges disclosed herein are to be understood to encompass all subranges contained herein. For example, a range "less than 10" may include, for a parameter that is limited to being positive, all subranges between (and including) a minimum value of zero and a maximum value of 10, i.e., all subranges having a minimum value greater than or equal to 0 and a maximum value less than or equal to 10, e.g., 1 to 4.

[0054] As used herein, the term "additive manufacturing" refers to industry standard terminology (ASTM F2792). It is generally defined as a process of joining materials to create objects from 3D model data, usually layer upon layer, as opposed to subtractive manufacturing methods. 3D printing is a type of additive manufacturing. The term "3D printing" is also used broadly to refer to various additive manufacturing methods, and thus the term "3D printing" also has some generality.

[0055] One of the longest-standing technological challenges is the problem of large amounts of waste material. One example is in the field of coatings, where many applications, including protective (e.g., antifouling, anticorrosion, antistatic, and ultraviolet (UV) barrier) and active (e.g., catalytic and sensing) coatings, only a thin top layer is required for functionality. This can be particularly problematic when highly efficient nanomaterials or other advanced materials are used in the coatings, resulting in significant unused material costs.

[0056] Electrospray deposition (ESD) is one of a family of electrostatically driven material deposition processes in which a high voltage electric field (typically >100 kilovolts per meter, kV / m) is used to generate fluid droplets or extruded wires. ESD describes conditions in which a dilute spray solution (typically <5% by volume) is subjected to an electric field while being expelled through a narrow capillary. The electric field creates an electric charge on the surface of the fluid, which in turn draws the fluid into a Taylor cone that expels droplets. These charged droplets break up in one or several generations of finely dispersed droplets to a size where surface and electrostatic forces balance. When each of these droplets reaches a grounded or opposite polarity target, the droplets deliver the material contained therein and deposit a coating of material.

[0057] Electrospray deposition processes are disclosed in the following references: U.S. Provisional Patent Application No. 62 / 683,869, filed June 12, 2018, entitled "THICKNESS LIMITED ELECTROSPRAY DEPOSITION OF THERMORESPONSIVE MATERIALS," which is incorporated herein by reference in its entirety; U.S. Non-Provisional Patent Application No. 17 / 251,262, filed December 11, 2020, entitled "THICKNESS-LIMITED ELECTROSPRAY DEPOSITION," which is incorporated herein by reference in its entirety; and U.S. Provisional Patent Application No. 62 / 848,320, filed May 15, 2019, entitled "METHODS AND DEVICES FOR THICKNESS-LIMITED ELECTROSPRAY ADDITIVE MANUFACTURING," which is incorporated herein by reference in its entirety. U.S. Non-provisional Patent Application No. 17 / 595,341, filed November 15, 2019, entitled "METHODS AND DEVICES FOR THICKNESS LIMITED ELECTROSPRAY ADDITIVE MANUFACTURING," the entirety of which is incorporated herein by reference.

[0058] The inventors have devised a unique and innovative approach to electrospray deposition. Specifically, the inventors place the target of the electrospray deposition process on a buried extractor target. The buried extractor target includes a conductor and a layer of insulating material between the target and the conductor. The buried extractor target shapes the charge landscape and focuses the spray onto the intended target. It is experimentally observed that deposition efficiency using the buried target extractor approaches 100%.

[0059] FIG. 1 shows a schematic of an exemplary electrospray deposition process. The diagram presented and discussed is a very highly conceptualized representation of the electrostatic deposition process, and the generalizations are not meant to be limiting. In addition, the disclosure provided herein attempts to describe the mechanisms at work, but the invention is not bound by these descriptions or by these mechanisms. Neither is the invention limited to these mechanisms.

[0060] The electrospray mechanism 100A includes a spray device 102 having an emitter 104. The emitter 104 includes a capillary 106 through which the medium flows and from which the medium is emitted. A high voltage power supply 110 is in electrical communication with the spray device 102 and is configured to apply a high voltage to the medium exiting the emitter 104. A medium source 112 is configured to supply medium 114 to the spray device 102. A controller 120 is in electrical and signal communication with the high voltage power supply 110, the medium source 112, and the spray device 102 to appropriately control the electrospray deposition process.

[0061] In an electrospray deposition process, a high voltage power supply 110 applies a high voltage to at least the emitter 104 and the medium 114 therein. This high voltage establishes an electric field 130 between the emitter 104 and a target 132 that is maintained at a lower voltage or grounded. The target 132 is typically composed of a conductive material. This high voltage also disperses the medium 114 exiting the emitter 104 into a spray plume composed of droplets of the medium of various sizes that are directed toward the target 132. The droplets of the medium 114 contain therein a solvent and a dispersed or dissolved payload material 116A. As the droplets traverse the distance to the target 132, the solvent may evaporate completely, leaving the flying payload material 116A that tends to follow the electric field lines 134 established by the electric field 130 to the target 132. The solvent may also reach the target 132 and continue to evaporate.

[0062] When the electrospray deposition process and the electric field 130 begins, the spray plume directs the payload material onto the mask 140 as payload material 116M and onto the unmasked portion 142 as payload material 116UM, which may be favorable for overspray to occur before establishing a stable electric field 130 and a stable spray plume. The overspray may completely surround the target 132. The payload material 116M on the mask 140 remains charged because they are in the electric field 130 and the electric field lines 130M are established by the payload material 116M. This is possible because the charged payload material 116M in turn establishes electric field lines with the target 132 through the mask 140. The electric field lines 130UM are also established to the unmasked portion 142 due to the payload material 116UM and the exposed conductive surface 144UM of the unmasked portion.

[0063] The charge 150M is formed around the payload material 116M on the mask 140 and is characterized by the intensity of the charge 150MC. The intensity of the charge 150MC is relatively large due to the relatively small profile of the target 132 in the electric field 130. In other words, the entire electric field 130 is focused on the relatively small target 132. As a result, the relatively large intensity of the charge 150MC is concentrated in the unmasked portion 142, which results in a relatively small window 152 that can be "seen" by the payload material 116A. Therefore, the electric field lines 130UM to the unmasked portion 142 are not necessarily appreciably denser than the electric field lines 130M to the mask 140. This causes the payload material 116A to not be attracted as strongly to the electric field lines 130UM beyond the electric field lines 130M to the mask 140. As a result, the payload material 116A continues to be deposited on the mask 140 as well as the unmasked portion 142, which represents a lower deposition efficiency than desired.

[0064] FIG. 2 is a schematic diagram of an exemplary electrospray deposition process disclosed herein. The process disclosed in the example of FIG. 2 includes an electrospray mechanism 100B having the same hardware and a recessed extractor target 200. The recessed extractor target 200 includes a conductor 202 made at least in part of a conductive material. The conductor 202 is held at a lower voltage / potential than the relatively high voltage of the emitter 104 or is grounded. The extractor target further includes an insulating material 204 disposed at least between the conductor 202 and the target 132. The target 132 is placed on the support surface 206 of the recessed extractor target 200 and the electrospray deposition process is initiated.

[0065] Similar to the process of FIG. 1, when the electrospray deposition process and electric field 210 begins, the spray plume directs payload material onto the mask 140 as payload material 116M and onto the unmasked portion 142 as payload material 116UM before establishing a stable electric field 130 and a stable spray plume. In addition, the spray plume directs payload material onto the insulating material 204 of the buried extractor target 200 (aka an insulated conductor) as payload material 116BE. The payload material 116M on the mask 140 and the payload material 116BE on the buried extractor target 200 remain charged because they are in the electric field 210. Again, the electric field lines 130M are established by the payload material 116M and the electric field lines 130UM are established up to the unmasked portion 142. In addition, the electric field lines 130BE are established by the payload material 116BE because they are in the reshaped / landscaped electric field 210. This is possible because the charged payload material 116BE, in turn, establishes electric field lines 130CB with the conductors 202 through the insulating material 204.

[0066] The resulting landscaped electric field 210 is larger than the electric field 130 in the process of Figure 1 and spreads among more payload material 116. Charges 150MC, 150BEC are formed around payload materials 150M and 150BE, respectively. Because there is more payload material 116M and 116BE in this process compared to the process of Figure 1, the electric field 210 spreads among more payload material 116M, 116BE. The resulting charges 150MC, 150BEC around the payload material will be relatively small compared to the charges in the process of Figure 1.

[0067] The smaller charges 150MC, 150BEC do not crowd the windows 220 of the unmasked portion 142 to the same extent. This allows the resulting electric field lines 130UM to better "see" the unmasked portion 142. As a result, the resulting electric field lines 130UM are characterized by a greater intensity (as indicated by their relatively thicker lines) than the other electric field lines 130BE, 130M. Payload material 116A in the spray plume is attracted to the relatively dense electric field lines 130UM more than it is attracted to the other electric field lines 130BE, 130M. As a result, the payload material 116A is more likely to follow the electric field lines 130UM to the unmasked portion 142 (as indicated by the payload material 116A only present within the electric field lines 130UM) than it is to follow the other electric field lines.

[0068] The buried extractor target 200 thus landscapes the electric field 210 (on the mask 140 and on the buried extractor target 200) by spreading the electric field lines and by reducing the magnitude and associated interference of the charge 150 of the oversprayed payload material. This allows the electric field lines 130 UM associated with the unmasked portion 142, which is the desired destination of the payload material 116 A, to be relatively stronger, thereby attracting more of the payload material 116 A. This improves the deposition efficiency. In addition, structuring the electric field 210 in this manner stabilizes the electric field, which in turn stabilizes the spray plume, the electric field lines, and the payload material 116 A therein.

[0069] The magnitude of the charges 150MC and 150BEC can be adjusted by adjusting the insulating value of the mask 140 and the insulating value of the insulating material 204, individually and relative to each other. For example, the magnitude of the charge 150MC can be reduced relative to the magnitude of the charge intensity 150BEC. This can result in the electric field lines 130M being relatively less dense than the electric field lines 130BE. Reducing the density of the electric field lines 130M can provide a buffer of relatively low density electric field lines 130M around the electric field lines 130UM. The buffer can help contain the payload material 116A in the preferred electric field lines 130UM by making it more difficult for the payload material 116A to reach / jump to adjacent electric field lines such as 130BE. The insulating material here may be characterized as having a bulk resistivity greater than about 1 GΩ / m, no other means of charge dissipation such as mass transport or surface conductivity, and is thick enough to prevent dissipation of the charge, for example, greater than about 10 μm.

[0070] Exemplary embodiments The following disclosure applies to the examples provided below and not necessarily to the entire disclosure of this specification.

[0071] In an exemplary embodiment, the target 132 and / or the embedded extractor target 200 may be temperature controlled. Heating or cooling the target 132 and / or the embedded extractor target 200 can change the viscosity of the liquid material that reaches thereon. This can then ensure that the liquid material does not electrowet away too much. Alternatively, one of the target 132 and / or the embedded extractor target 200 can be heated and the other cooled to achieve the desired electrowetting effect.

[0072] In an exemplary embodiment, the masking procedure may be an additive masking procedure (e.g., adding insulating regions to a conductive target), or the masking procedure may be a subtractive masking procedure (e.g., adding conductive regions to an insulating target).

[0073] Figure 3 shows a schematic of the electrostatic deposition process of Figure 2, taken along line AA of Figure 2. Figure 3 is a view from the perspective of the emitter 104. The electric field 210 is shown as a cone, but any suitable shape may be landscaped. The electric field lines 130BE to the buried extractor target 200 and the electric field lines 130M to the mask 140 are shown. Additionally, the electric field lines 130UM leading to the unmasked portion 142 are shown.

[0074] The buried extractor target 200 establishes an extractor target profile 300 as seen by the emitter 104. The perimeter 302 of the extractor target profile 300 establishes an extractor target profile region 304. The electric field 210 establishes an electric field profile 310 as seen by the emitter 104. The perimeter 312 of the electric field profile 310 establishes an electric field profile region 314. The target 132 establishes a target profile 330 as seen by the emitter 104. The perimeter 322 of the target profile 330 establishes a target profile region 324.

[0075] In some examples, the target 132 is disposed completely within the perimeter 302 of the extractor target profile 300. In some examples, the target 132 is disposed completely within the perimeter 312 of the electric field profile 310 such that the electric field lines 130BE completely surround the target 132. In some examples, the extractor target profile area 304 is at least 500% larger than the target profile area 324. In some examples, the extractor target profile area 304 is at least 100 times larger than the target profile area 324. In some examples, the electric field profile area 314 is at least 1000% larger than the target profile area 324. Although the electric field profile area 314 is shown as being smaller than the extractor target profile 300, this is not required. The electric field profile area 314 may be larger than the extractor target profile 300.

[0076] In one exemplary embodiment, the perimeter 322 of the target profile 330 maintains a setback 340 of at least 2 cm from all points on the perimeter 312 of the unaltered electric field profile 310. In one example, the perimeter 322 of the target profile 330 maintains a setback 342 of at least 1 cm from all points on the perimeter 302 of the extractor target profile 300.

[0077] In one example, the mass of the embedded extractor target 200 is at least 1,000 times the mass of the target 132. In one example, the mass of the embedded extractor target 200 is at least 1,000,000 times the mass of the target 132.

[0078] Although the process has been described with the mask 140 present on the target 132, the mask need not be present. The principles relating to the embedded extractor target 200 would still apply.

[0079] 4 shows a schematic of an alternative example of the electrostatic deposition process. In this example, the target 132 and embedded extractor target 200 are repositioned relative to the emitter 104 to more closely align the axis 400 of the capillary 106 with the trajectory of the electric field lines 130 that favor carrying the payload material 116A. This alignment causes the payload material 116A to start traveling along a path that coincides with the electric field lines 130, thereby increasing the likelihood that the payload material 116A will follow the electric field lines 130.

[0080] 5A shows a schematic of an alternative example of an electrospray deposition process. In this example, a focusing ring 500, constructed of an insulating or conductive material maintained at a voltage of about 0-75% of the drive voltage, is used to focus the electric field lines 502 and associated shape of the spray 504 of medium therethrough to the unmasked regions 506 of a target 508. The target 508 is positioned on an insulating material 520 of a buried extractor target 522.

[0081] 5B shows a schematic of an alternative electrospray deposition process: (1) shows, for example, a negative polarity ethanol pre-spray; (2) shows, for example, a positive polarity spray of the target 508.

[0082] In an alternative embodiment, additional potential differences may be created. For example, focus ring 500 and spray 504 may have a positive potential, buried extractor target 522 may be grounded, and target 508 may have a negative potential. In various embodiments, emitter 104, focus ring 500, target 508, and buried extractor target 522 may be held at any combination of different potentials to manipulate the charge landscape to achieve different desired depositions. Each potential may be unique, or one or more potentials may be the same while the other potentials are unique. In an embodiment, the voltage may be reduced such that emitter 104 voltage may be higher than focus ring 500 voltage, which may be higher than target 508 voltage, which may be higher than buried extractor target 522 voltage, and so on. In another embodiment, the voltage of target 508 may be lower than the voltage of buried extractor target 522, which is lower than the voltage of focus ring 500, which is lower than the voltage of emitter 104. These examples are non-limiting and any order or polarity may be used.

[0083] As used herein, a relatively high voltage may, in a non-limiting example, describe a first positive voltage that is higher than a second positive voltage or a second negative voltage. However, the present disclosure is not so limited. The potential difference that creates the polarity between components is more broadly applicable. In a first polarity scheme, for example, the nozzle may be at a first positive voltage and the target may be at a second voltage that is positive but lower than the first positive voltage. In a different first polarity scheme, the nozzle may be at a first positive voltage and the target may be at a second voltage that is negative. In another first polarity scheme, the nozzle may be at a first negative voltage and the target may be at a second voltage that is even more negative than the first negative voltage. The potential difference that results in the first polarity scheme is not limited to the above examples, and other potential differences that create a first polarity may be used.

[0084] In a second polarity scheme, for example, the nozzle may be at a first positive voltage and the target may be at a second voltage that is positive but higher than the first positive voltage. In a different first polarity scheme, the nozzle may be at a first negative voltage and the target may be at a second voltage that is positive. In another first polarity scheme, the nozzle may be at a first negative voltage and the target may be at a second voltage that is less negative than the first negative voltage. The potential difference resulting in the second polarity scheme is not limited to the above examples, and other potential differences that generate the second polarity may be used. Furthermore, the above-mentioned scheme between the nozzle and the target may be applied individually between any two (or more) of at least the emitter 104, the focus ring 500, the target 508, and the embedded extractor target 522 to generate any desired potential difference scheme between the two (or more) components.

[0085] FIG. 6 is a chart showing exemplary results of various coating processes. In the first coating process, a needle was used. In the second coating process, a flat geometry was used. Also shown are results of processes where no mask was applied to the target, no pre-spray was performed, no insulation was present on the conductor of the buried extractor target, and no extractor target was used. It can be seen that the process disclosed herein, together with the use of pre-spray, provides deposition efficiency approaching 100%.

[0086] Approaches to Engineering Charge Landscapes

[0087] Figure 7A shows the UV-visible deposition efficiency for microneedle array MNA (T1), silicon chip (T2), and microelectrode test pattern printed on borofloat (T3) samples with all process enhancements using 0.2 wt % trehalose spray, as well as for MNA samples with a single enhancement removed (no pre-spray (-E1), no buried extractor (-E2), no insulation for focus ring and extractor ground (-E3), no insulating mask (-E4), and no focus ring (-E5)).

[0088] FIG. 7B shows an exemplary embodiment of a bare MNA (no insulating mask). FIG. 7C shows an exemplary embodiment of an unmasked trehalose-sprayed MNA. FIG. 7D shows an exemplary embodiment of a trehalose-sprayed MNA with no insulation on the focus ring or buried extractor target. FIG. 7E shows an exemplary embodiment of a trehalose-sprayed MNA with all enhancements. FIG. 7F shows an exemplary embodiment of a generic trehalose-sprayed silicon chip. FIG. 7G shows an exemplary embodiment of a generic trehalose-sprayed microelectrode pattern.

[0089] It should be noted that some of the apparent efficiencies are greater than 100%, which is hypothesized to be a combined effect of the accuracy of the UV-vis approach, especially for small amounts of material, and the accumulation of some dried material on the needle tip between samples and stabilization of the spray. In terms of final system design, automated sample transfer and spray stabilization, as recently demonstrated by Toth et al., (#84), would likely improve the accuracy of the technique. Despite this, there are still significant differences between the augmented and non-augmented results.

[0090] A significant difference is the effect of allowing alternative targets. This is shown here in two ways. The first is obtained by omitting the silicon mask (Figure 7C), which allows 45±35% of the coating to be deposited on undesired parts of the sample, consistent with the amount of undesired conductive surface. The second is to omit the masking tape of the extractor ground and the focus ring (Figure 7D), which results in a much larger conductive surface for the spray to deposit on. The role of this tape is to accumulate charge during the first few moments of the spray at the beginning, which redirects the field lines towards the unmasked parts of the target. 91±2% of the spray is redirected to these large alternative targets, especially the focus ring, which do not have their own electric field strong enough to repel the spray and require a small accumulation of charge. The omission of the focus ring allows the droplets to follow a wider range of electric field paths, allowing the spray to escape to other distant grounds or to the circulating air in the spray chamber, leading to a decrease in efficiency of 22±15%. The pre-spray establishes a "blank slate" condition, the absence of which causes the charge in the chamber to gradually rise to the point of destabilizing the spray, leading to a gradual decrease in efficiency of 60±46%. Finally, excluding the extracting ground (buried extractor target) causes a loss of efficiency of 60±16%, which arises from charge screening and eventual destabilization of the spray in the absence of a large stabilizing extractor ground. This extractor ground is hypothesized to allow the electric field lines not directed toward the target to remain stable against the opposing electric field imposed by the charge deposited on the insulating surface.

[0091] Implementing all of these process enhancements (Figure 7E) leads to 104 ± 10% of the spray arriving at the needle tip, indicating that very little solid payload leaves the needle without reaching the target. Looking towards a silicon chip (Figure 7F) or a microelectrode test pattern (Figure 7G) does not change this efficiency (110 ± 25% and 96 ± 18%, respectively).

[0092] Spray efficiency for various materials

[0093] FIG. 7H shows the UV-vis deposition efficiency for various materials, including trehalose (T1), GLS-1027 (M2), PEDGA (M3), PVP (M4), PEDOT:PSS (M5), GLS-6150 (M6), and bovine serum albumin protein (M7).

[0094] All materials have average apparent efficiencies above 97%, except for PEG, which could not be quantified. Note that in all cases, only the tracer was quantified. This is based on the assumption that the composition of the spray is constant from the syringe to the target. This assumption can be justified by (1) the use of a relatively dilute solution such that precipitation at the spray needle tip is unlikely, and (2) the fact that the tracer has a molecular weight commensurate with the lightest payload (479 g / mol compared to 205 g / mol for GLS1027). This means that if atomization of the material and detachment by diffusion or convection occurs, it is likely to occur for the tracer as well. In the case of PEG, there are two explanations for the low efficiency, both due to its low viscosity. First, as was observed, gravity led to dripping from the needle. Second, the material remains mobile after spraying, but becomes uncharged due to electrowetting dissipation (#83), and finds itself at a large potential difference with the spray needle (especially at a sharp needle tip), which could electrospray back onto the needle. These opposite polarity droplets may collide with the incoming spray droplets, dissipating their charge and resulting in undirected droplets that are carried away by the air current. This mechanism is not often observed and is likely secondary in earth gravity.

[0095] experiment

[0096] Materials: D-(+)-Trehalose dihydrate, PEGDA (Mn=4,000), BSA in water (20 mg mL-1), HRP type VI, PEDOT:PSS, rhodamine B, MilliQ water, ethanol, l-step Ultra TMB-ELISA substrate solution, and Pierce 660 nm protein assay reagent were obtained from Sigma Aldrich. Kollidon 12 (PVP) was obtained from BASF. GLS-6150 (Lot VGX-6150.13A001) and GLS-1027 (Lot 19AK0183A) were obtained from GeneOne Life Science, Inc. Sulfuric acid was obtained from Fisher Scientific. AZ400K developer (potassium-based buffered alkaline solution) was obtained from MicroChemicals. PicoPure water was obtained from Hydro Service and Supplies.

[0097] Solution preparation: PEDOT:PSS solutions were prepared by dialyzing the dry redispersible PEDOT:PSS pellets in water for 5 days, ending with a final concentration of 20 mg mL-1. The dialyzed solution was further diluted to 10 mg mL-1. For PEDOT:PSS and BSA, 100 μL of the 10 mg mL-1 solution in water was mixed with 400 μL of pure ethanol and diluted with 1 cm 2 All other solutions sprayed onto the microneedle substrate were prepared by mixing 100 μL of a 10 mg mL-1 solution in water (or 200 proof ethanol for GLS-1027), 10 μL of 25 μg mL-1 Rhodamine B, and 450 μL of pure ethanol.

[0098] Electrospray setup: The electrospray setup consisted of a syringe pump (Harvard Apparatus 11Plus), one negative high voltage power supply (Acopian Power Supply, N012HA5), two positive high voltage power supplies (Acopian Power Supply, P012HA5), a stainless steel needle (SAI The chamber contained a 4 × 4 array of 2 mm long stainless steel microneedles, a 20 gauge, 0.5” Infusion, steel guard ring (4 cm outer diameter, 2 cm inner diameter), and a humidity and temperature controlled environmental chamber (ETS). The chamber had a controlled humidity ranging from 15-25% RH and temperature ranging from 24-27 °C. A 1 mL Luer lock syringe with an inner diameter of 4.78 mm was used to fill the spray solution. The microneedle array was placed on an aluminum holding block and the microneedle and holding block were grounded. A positive voltage was applied to the syringe needle and guard ring and adjusted as necessary. Each sample was sprayed with a negative pre-spray using 200 proof ethanol. All conductive materials within the chamber, including the guard ring and holding block, were insulated by using one layer of 2 mil Kapton polyimide tape. The microneedle array was sonicated in a vial containing surfactant and water for cleaning.

[0099] Experimental parameters: Sprays were stabilized at a constant spray distance of 2 cm to the ring and 4 cm to the target using a primary voltage ranging from 6 to 8.5 kV. The ring voltage was held at 0.41 kV. Ambient humidity was regulated between 15 and 25%. All sprays were performed at a flow rate of 0.1 mL / h, corresponding to a mass delivery rate of 180 μg / h of payload material and 45 ng / h of tracer. Sprays for efficiency calculations were sprayed for 30 min, yielding 90 μg of material and 45 ng of tracer.

[0100] Calculation of apparent deposition efficiency

[0101] The PEDOT:PSS and BSA samples were immersed in 600 μL of water and measured using the UV-vis and BSA protein A280 functions of a Thermo Scientific Nanodrop 2000C, respectively. Measurements were performed at 260 nm and no baseline correction was used for the measurements.

[0102] For all other samples, the needle or tip was immersed in 600 μL of water, or for GLS-1027, AZ400K developer (MicroChemicals) for 2 min until all material had dissolved from the needle. The solutions were then analyzed on a Jasco 770 UV-vis spectrophotometer. Results were then background subtracted using a Gaussian fit to extract the rhodamine peak, which was compared to a standard calibration curve generated in the same solvent.

[0103] 8A and 8B show an exemplary embodiment of a self-limiting electrospray deposition (SLED) process with an ungrounded buried extractor target 800. In this example, an emitter 804 includes a capillary 806 through which a medium flows. The cone-jet mode of spraying maintains a Taylor cone 810 at the tip of the emitter 804. A droplet jet 812 then flows from the Taylor cone 810 toward a target 832.

[0104] 9A and 9B are charts showing the results of the self-limiting electrospray deposition (SLED) process using DNA alone and DNA with the addition of trehalose. DNA in a water-only solution is not necessarily compatible for SLED, as DNA is above its glass transition temperature at room temperature. Trehalose was added to the DNA solution to form a glassy complex, which allowed SLED to be performed.

[0105] FIG. 10A is a chart showing the processing results of various electrospray deposition processes. FIG. 10B shows an exemplary embodiment of a microneedle array without a silicon mask of the type used in the chart of FIG. 10A. FIG. 10C shows an exemplary embodiment of a microneedle array with a silicon mask of the type used in the chart of FIG. 10A. Without a form of insulation, the charged spray deposits on the electrodes with a deposition efficiency of about 6%. By shaping the charge landscape and adding target areas, the spray is directed to the needle tips. Silicone tape with larger needle arrays shows the highest deposition efficiency.

[0106] 11A-11C show an exemplary embodiment of selective electrospray deposition (SLED) onto a three-dimensional object 1100. The build-up of charge in the material depositing on the target starts to repel itself, leading to a limit in the final thickness and a slowdown in the deposition rate. Because of this property, SLED redirects the spray onto areas of the target that are not being coated, achieving a uniform coating.

[0107] Figures 12A-12C show an exemplary embodiment of selective electrospray deposition (SLED) onto a three-dimensional object. Similar to Figures 11A-11C, charge build-up of material depositing on the target begins to repel itself, leading to a limit in final thickness and a slowdown in deposition rate. Because of this property, SLED redirects the spray onto areas of the target that are not being coated, achieving a uniform coating. (#44).

[0108] Figure 13 is a chart showing the process results of selective electrospray deposition (SLED) compared to the conventional electrospray deposition process (ESD). (#44).

[0109] Figure 14A shows selective electrospray deposition (SLED) on a small target. Figure 14B is a chart showing dewetting width and spray height. (#91).

[0110] Figures 15A-D compare microneedle arrays coated with various coating techniques. As seen in Figure 15A, dip coating provides easy application but exhibits capillary action and requires bath processing. As seen in Figure 15B, inkjet printing provides targeted delivery but exhibits capillary action and requires continuous processing. As seen in Figure 15C, standard spray coating provides targeted delivery but wastes mask material. As seen in Figure 15D, electrospray deposition provides localized coating with rapid processing but can result in shear damage. (#116).

[0111] Figure 16A is an exemplary embodiment of a microneedle array subjected to various coating techniques with various compositions, and Figures 16B and 16C are charts showing the process results of the coatings on the microneedle array of Figure 16A.

[0112] Figure 17A shows DNA delivery using electrospray deposition (#92). Figures 17B and 17C show the results of DNA delivery in Figure 17A (#117).

[0113] Figures 18A and 18B show the results of DNA delivery applied via self-limiting electrospray deposition (SLED). It demonstrates up to 70% delivery of viable supercoiled pDNA by SLED loaded into a biocompatible, dissolvable coating, with Q approaching the control (Q = (supercoiled / linear)). GFP DNA from the spray coating was successfully expressed in in vitro electroporation experiments.

[0114] 19 is a chart of wavelength vs. absorbance relevant to the UV-vis determination disclosed herein. Rhodamine B is used as an internal standard for the UV-vis signal. A Gaussian model is used for background subtraction.

[0115] FIG. 20 shows a calibration curve for 0.0025% by weight Rhodamine B in water in a chart of the amount of Rhodamine versus the integrated area of ​​the Rhodamine peak relevant for UV-Vis determination.

[0116] FIG. 21A and FIG. 21B show the high performance liquid chromatography results for the control and GLS-1027 samples in respective charts of duration versus height.

[0117] The buried extractor target can be used in conjunction with any electrospray process. In addition, the buried extractor target can be used in conjunction with various aspects of electrospray deposition, including applying negative, positive, or neutral pre-spray, use with a focus ring, use of a shutter, and dissipating ambient charge.

[0118] The inventors have created an apparatus and method that can improve the deposition efficiency of selectively coated substrates in a manner that is simple and inexpensive to implement, and thus represents an improvement in the art.

[0119] Computer Hardware FIG. 7 is a block diagram illustrating a computer system 1300 on which embodiments of the invention may be implemented. The computer system 1300 includes a communication mechanism, such as a bus 1310, for conveying information between other internal and external components of the computer system 1300. The information is represented as a physical signal of a measurable phenomenon, typically a voltage, but in other embodiments including phenomena such as magnetism, electromagnetism, pressure, chemicals, atomic and quantum interactions of molecules. For example, north and south magnetic fields, or zero and non-zero electrical voltages represent the two states (0,1) of a binary digit (bit). Other phenomena can represent digits of higher order binary numbers. A superposition of multiple simultaneous quantum states before measurement represents a quantum bit (qubit). One or more strings of binary digits constitute digital data used to represent numbers or code letters. In some embodiments, information, referred to as analog data, is represented by a close continuum of measurable values ​​within a particular range. The computer system 1300, or portions thereof, constitute a means for performing one or more steps of one or more methods described herein.

[0120] A sequence of binary digits constitutes digital data used to represent a code for a number or character. The bus 1310 includes many parallel conductors of information so that information may be rapidly conveyed among devices coupled to the bus 1310. One or more processors 1302 are coupled to the bus 1310 for processing information. The processor 1302 performs a set of operations on the information. The set of operations includes taking information from the bus 1310 and putting information onto the bus 1310. The set of operations also typically includes comparing two or more units of information, rearranging units of information, and combining two or more units of information, such as by addition or multiplication. The sequence of operations performed by the processor 1302 constitutes computer instructions.

[0121] The computer system 1300 also includes a memory 1304 coupled to the bus 1310. The memory 1304, such as a random access memory (RAM) or other dynamic storage device, stores information, including computer instructions. Dynamic memory allows information stored therein to be changed by the computer system 1300. RAM allows units of information stored at locations called memory addresses to be stored and retrieved independently of information at nearby addresses. The memory 1304 is also used by the processor 1302 to store temporary values ​​during execution of computer instructions. The computer system 1300 further includes a read only memory (ROM) 1306 or other static storage device coupled to the bus 1310 for storing static information, including instructions, that is not changed by the computer system 1300. Additionally, a non-volatile (persistent) storage device 1308, such as a magnetic or optical disk, is also coupled to the bus 1310 for storing information, including instructions, that persists even when the computer system 1300 is turned off or otherwise loses power.

[0122] Information, including instructions, is provided on the bus 1310 for use by the processor from an external input device 1312, such as a keyboard containing alphanumeric keys operated by a human user or by sensors. The sensors detect conditions in their vicinity and convert the detections into signals compatible with those used to represent information in the computer system 1300. Other external devices connected to the bus 1310, primarily used for human interaction, include a display device 1314, such as a cathode ray tube (CRT) or liquid crystal display (LCD), for presenting images, and a pointing device 1316, such as a mouse or trackball or cursor direction keys, for controlling the position of a small cursor image presented on the display 1314 and for issuing commands related to graphical elements presented on the display 1314.

[0123] In the illustrated embodiment, special purpose hardware such as application specific integrated circuits (ICs) 1320 are coupled to bus 1310. The special purpose hardware is configured to perform operations for a special purpose that cannot be performed quickly enough by processor 1302. Examples of special purpose ICs include graphics accelerators for generating images for display 1314, cryptographic processing boards for encrypting and decrypting messages sent over a network, voice recognition, and interfaces to specialized external devices such as robotic arms or medical scanning devices that perform some complex sequence of movements that are more efficiently performed in hardware.

[0124] The computer system 1300 also includes one or more instances of a communications interface 1370 coupled to the bus 1310. The communications interface 1370 provides a two-way communications coupling to various external devices, such as printers, scanners, and external disks, that run on their own processors. Typically, this coupling is to a network link 1378 that is connected to a local network 1380 to which various external devices with processors are connected. For example, the communications interface 1370 may be a parallel port or a serial port, or a universal serial bus (USB) on a personal computer. In some embodiments, the communications interface 1370 is an Integrated Services Digital Network (ISDN) card, or a Digital Subscriber Line (DSL) card, or a telephone modem that provides a telecommunications connection to a corresponding type of telephone line. In some embodiments, the communications interface 1370 is a cable modem that converts signals on the bus 1310 to signals for a communications connection via coaxial cable, or optical signals for a communications connection via fiber optic cable. As another example, the communications interface 1370 may be a local area network (LAN) card to provide a data communications connection to a compatible LAN, such as Ethernet. Wireless links may also be implemented. Carrier waves, such as acoustic and electromagnetic waves, including radio, light, and infrared waves, travel through space without wires or cables. The signals include man-made variations in the amplitude, frequency, phase, polarization, or other physical properties of the carrier wave. For wireless links, communications interface 1370 sends and receives electrical, acoustic, or electromagnetic signals, including infrared and optical signals, that carry information streams, such as digital data.

[0125] The term "computer-readable medium" is used herein to refer to a medium that participates in providing information to the processor 1302, including instructions for execution. Such media may take many forms, including, but not limited to, non-volatile media, volatile media, and transmission media. Non-volatile media include, for example, optical or magnetic disks, such as the storage device 1308. Volatile media include, for example, the dynamic memory 1304. Transmission media include, for example, waves that travel through space without wires or cables, such as coaxial cables, copper wire, fiber optic cables, radio waves, light waves, and sound waves and electromagnetic waves, including infrared waves. The term computer-readable storage medium is used herein to refer to any medium that participates in providing information to the processor 1302, except for transmission media.

[0126] Common forms of computer readable media include, for example, a floppy disk, flexible disk, hard disk, magnetic tape or other magnetic media, compact disk ROM (CD-ROM), digital video disk (DVD) or other optical media, punch cards, paper tape or other physical media with patterns of holes, RAM, programmable ROM (PROM), erasable PROM (EPROM), flash EPROM or other memory chips or cartridges, carrier waves, or other media from which a computer can read. The term non-transitory computer readable storage medium is used herein to refer to any medium that participates in providing information to the processor 1302, excluding carrier waves and other signals.

[0127] The logic encoded in one or more tangible media includes one or both of computer-readable storage media and processor instructions on special purpose hardware, such as an ASIC (1320).

[0128] The network link 1378 typically provides information communication through one or more networks to other devices that use or process the information. For example, the network link 1378 may provide a connection through a local network 1380 to a host computer 1382 or to equipment 1384 operated by an Internet Service Provider (ISP). The ISP equipment 1384 in turn provides data communication services through the public world-wide packet-switched communication network of networks now commonly referred to as the Internet 1390. A computer connected to the Internet, referred to as a server 1392, provides services responsive to information received on the Internet. For example, the server 1392 provides information representing video data for presentation on the display 1314.

[0129] The present invention relates to the use of computer system 1300 to implement the techniques described herein. According to one embodiment of the present invention, such techniques are performed by computer system 1300 in response to processor 1302 executing one or more sequences of one or more instructions contained in memory 1304. Such instructions, also referred to as software or program code, may be loaded into memory 1304 from another computer-readable medium, such as storage device 1308. Execution of the sequences of instructions contained in memory 1304 causes processor 1302 to perform the method steps described herein. In alternative embodiments, hardware, such as application specific integrated circuit 1320, may be used in place of or in combination with software to implement the present invention. Thus, embodiments of the present invention are not limited to any specific combination of hardware and software.

[0130] Signals sent through network link 1378 and other networks through communication interface 1370 carry information to and from computer system 1300. Computer system 1300 can send and receive information, including program code, through networks 1380, 1390, among others, through network link 1378 and communication interface 1370. In an example using Internet 1390, server 1392 transmits application specific program code requested by messages sent from computer 1300 through Internet 1390, ISP equipment 1384, local network 1380, and communication interface 1370. The received code may be received and executed by processor 1302 and / or stored in storage device 1308 or other non-volatile storage for later execution. In this manner, computer system 1300 may obtain application program code in the form of signals on a carrier wave.

[0131] Various forms of computer readable media may be involved in carrying one or more sequences of instructions, data, or both, to the processor 1302 for execution. For example, the instructions and data may initially be carried on a magnetic disk of a remote computer, such as the host 1382. The remote computer loads the instructions and data into its dynamic memory and sends the instructions and data over a telephone line using a modem. A modem native to the computer system 1300 receives the instructions and data on the telephone line and uses an infrared transmitter to convert the instructions and data into signals on an infrared carrier wave that serves as the network link 1378. An infrared detector, serving as the communications interface 1370, receives the instructions and data carried in the infrared signal and places information representing the instructions and data on the bus 1310. The bus 1310 conveys the information to the memory 1304, and the processor 1302 retrieves and executes the instructions from the memory, using a portion of the data transmitted with the instructions. The instructions and data received by the memory 1304 may optionally be stored on a storage device 1308 either before or after execution by the processor 1302.

[0132] FIG. 8 illustrates a chipset 1400 upon which an embodiment of the present invention may be implemented. The chipset 1400 includes the processor and memory components described with respect to FIG. 7, programmed to perform one or more steps of the methods described herein, and integrated into one or more physical packages (e.g., chips). By way of example, the physical package may include an arrangement of one or more materials, components, and / or wires on a structural assembly (e.g., skirting board) to provide one or more characteristics such as physical strength, size conservation, and / or limited electrical interaction. In an embodiment, it is contemplated that the chipset may be implemented in a single chip. The chipset 1400, or portions thereof, constitute a means for performing one or more steps of the methods described herein.

[0133] In one embodiment, the chipset 1400 includes a communication mechanism, such as a bus 1401, for passing information between components of the chipset 1400. The processor 1403 has connectivity to the bus 1401 to execute instructions and process information stored in, for example, the memory 1405. The processor 1403 may include one or more processing cores, each configured to perform independently. A multi-core processor allows for multi-processing within a single physical package. Examples of multi-core processors include two, four, eight, or more processing cores. Alternatively, or in addition, the processor 1403 may include one or more microprocessors configured in tandem via the bus 1401 to enable independent execution of instructions, pipelining, and multi-threading. The processor 1403 may be accompanied by one or more dedicated components to perform specific processing functions and tasks, such as one or more digital signal processors (DSPs) 1407 or one or more application specific integrated circuits (ASICs) 1409. DSP 1407 is typically configured to process real-world signals (e.g., sound) in real time, independent of processor 1403. Similarly, ASIC 1409 can be configured to perform specialized functions not easily performed by a general-purpose processor. Other specialized components that assist in performing the functions of the invention described herein include one or more field programmable gate arrays (FPGAs) (not shown), one or more controllers (not shown), or one or more other special purpose computer chips.

[0134] The processor 1403 and associated components have connectivity to memory 1405 via bus 1401. The memory 1405 includes both dynamic memory (e.g., RAM, magnetic disk, writable optical disk, etc.) and static memory (e.g., ROM, CD-ROM, etc.) for storing executable instructions that, when executed, perform one or more steps of the methods described herein. The memory 1405 further stores data associated with or generated by the execution of one or more steps of the methods described herein.

[0135] In the foregoing specification, the invention has been described with reference to specific embodiments thereof. However, it will be apparent that various modifications and changes can be made without departing from the broader spirit and scope of the invention. For this reason, the specification and drawings are to be regarded in an illustrative rather than a restrictive sense. Throughout this specification and claims, unless otherwise required by context, the term "comprise" and its variations, "comprises" and "comprising" and the like, will be understood to imply the inclusion of a stated item, element, or step, or group of items, elements, or steps, but not the exclusion of other items, elements, or steps, or group of items, elements, or steps. Furthermore, the indefinite article "a" or "an" is meant to indicate one or more of the items, elements, or steps modified by the indefinite article.

[0136] References The following are incorporated herein by reference as if fully set forth herein, except for any terminology that conflicts with terminology used herein: 1. Klein,LC;Kallontzi,S.;Fabris,L.;Jitianu,A.;Ryan,C.;Aparicio,M.;Lei,L.;Singer,JPJournal of Sol-Gel Science and Technology 2018. 2. Naguib,M.;Mochalin,V.N.;Barsoum,M.W.;Gogotsi,Y.Advanced Materials 2014,26,(7),992-1005. 3. Merrill,M.H.;Pogue,I.I.I.W.R.;Baucom,J.N.Journal of Micro and Nano-Manufacturing 2015,3,(1),011003-011003. 4. Merrill,M.;Teferra,K.;Kang,W.In Nano-scaled Structures through Charged Particle Interactions,Proceedings of the American Society for Composites:Thirty-First Technical Conference,2016. 5. Zeleny,J.Physical review 1917,10,(1),1. 6. Vonnegut,B.;Neubauer,R.L.Journal of Colloid Science 1952,7,(6),616-622. 7. Taylor,G.Proceedings of the Royal Society of London.Series A,Mathematical and Physical Sciences 1964,280,(1382),383-397. 8. Yamashita,M.;Fenn,J.B.The Journal of Physical Chemistry 1984,88,(20),4451-4459. 9. Blumberg,L.N.;Gursky,J.C.;Stein,P.C.,Electrospraying of Thin Targets.Los Alamos Scientific Laboratory:1962. 10. Wu,S.Polymer-Plastics Technology and Engineering 1976,7,(2),119-220. 11. Prasad,L.K.;McGinity,J.W.;Williams,R.O.International Journal of Pharmaceutics 2016,505,(1),289-302. 12. Elmoursi,A.A.;Garner,D.P.J.Coat.Technol.1992,64,(805),39-44. 13. Tachi,K.;Okuda,C.;Yamada,K.J.Coat.Technol.1990,62,(791),19-25. 14. Bailey,A.G.Journal of Electrostatics 1998,45,(2),85-120. 15. Edward Law,S.Journal of Electrostatics 2001,51-52,25-42. 16. Gaskell,S.J.Journal of mass spectrometry 1997,32,(7),677-688. 17. Jaworek,A.;Sobczyk,A.T.Journal of Electrostatics 2008,66,(3-4),197-219. 18. Subbiah,T.;Bhat,G.S.;Tock,R.W.;Parameswaran,S.;Ramkumar,S.S.Journal of Applied Polymer Science 2005,96,(2),557-569. 19. Gomez,A.;Tang,K.Physics of Fluids 1994,6,(1),404-414. 20. Ganan-Calvo,A.M.;Davila,J.;Barrero,A.Journal of Aerosol Science 1997,28,(2),249-275. 21. Moerman,R.;Frank,J.;Marijnissen,J.C.M.;Schalkhammer,T.G.M.;van Dedem,G.W.K.Analytical Chemistry 2001,73,(10),2183-2189. 22. Hinaut,A.;Pawlak,R.;Meyer,E.;Glatzel,T.Beilstein Journal of Nanotechnology 2015,6,1927-1934. 23. Woo,C.G.;Shin,H.;Jeong,C.;Jun,K.;Lee,J.;Lee,J.-R.;Lee,H.;You,S.;Son,Y.;Choi,M.Small 2011,7,(13),1790-1794. 24. Hu,H.;Singer,J.P.;Osuji,C.O.Macromolecules 2014,47,(16),5703-5710. 25. Choo,Y.;Hu,H.;Toth,K.;Osuji,C.O.Journal of Polymer Science Part B:Polymer Physics 2016,54,(2),247-253. 26. Hu,H.;Toth,K.;Kim,M.;Gopalan,P.;Osuji,C.O.MRS Communications 2015,5,(2),235-242. 27. Kim,J.-S.;Chung,W.-S.;Kim,K.;Kim,D.Y.;Paeng,K.-J.;Jo,S.M.;Jang,S.-Y.Advanced Functional Materials 2010,20,(20),3538-3546. 28. Rietveld,I.B.;Kobayashi,K.;Yamada,H.;Matsushige,K.Soft Matter 2009,5,(3),593-598. 29. Weiss,F.M.;Topper,T.;Osmani,B.;Peters,S.;Kovacs,G.;Muller,B.Adv.Electron.Mater.2016,2,(5),8. 30. Guo,Q.;Mather,J.P.;Yang,P.;Boden,M.;Mather,P.T.PLOS ONE 2015,10,(6),e0129960. 31. Rietveld,I.B.;Kobayashi,K.;Yamada,H.;Matsushige,K.Journal of Colloid and Interface Science 2006,298,(2),639-651. 32. Novak,S.;Johnston,D.E.;Li,C.;Deng,W.;Richardson,K.Thin Solid Films 2015,588,56-60. 33. Chavhan,M.P.;Ganguly,S.Industrial & Engineering Chemistry Research 2016,55,(38),10073-10083. 34. Leeuwenburgh,S.;Wolke,J.;Schoonman,J.;Jansen,J.Journal of Biomedical Materials Research Part A 2003,66A,(2),330-334. 35. Kim,J.-Y.;Kim,E.-K.;Kim,S.S.Journal of Colloid and Interface Science 2013,392,376-381. 36. Kim,J.W.;Yamagata,Y.;Kim,B.J.;Higuchi,T.Journal of Micromechanics and Microengineering 2009,19,(2),025021. 37. Al-Milaji,K.N.;Zhao,H.Applied Surface Science 2017,396,955-964. 38. Burkarter,E.;Saul,C.K.;Thomazi,F.;Cruz,N.C.;Roman,L.S.;Schreiner,W.H.Surface and Coatings Technology 2007,202,(1),194-198. 39. Hou,X.;Choy,K.-L.Surface and Coatings Technology 2004,180-181,15-19. 40. Krella,A.K.;Sobczyk,A.T.;Krupa,A.;Jaworek,A.Mechanics of Materials 2016,98,120-133. 41. Hwang,D.;Lee,H.;Jang,S.-Y.;Jo,S.M.;Kim,D.;Seo,Y.;Kim,D.Y.ACS Applied Materials & Interfaces 2011,3,(7),2719-2725. 42. Li,Q.;Church,J.S.;Naebe,M.;Fox,B.L.Composites Part A:Applied Science and Manufacturing 2016,90,174-185. 43. Tang,J.;Gomez,A.Aerosol Science and Technology 2017,51,(6),755-765. 44. Lei,L.;Kovacevich,D.A.;Nitzsche,M.P.;Ryu,J.;Al-Marzoki,K.;Rodriguez,G.;Klein,L.C.;Jitianu,A.;Singer,J.P.ACS Applied Materials & Interfaces 2018,10,(13),11175-11188. 45. Cazaux,J.Journal of Electrostatics 2007,65,(12),764-774. 46. Hoburg,J.F.IEEE Transactions on Industry Applications 1982,(6),666-672. 47. Bodnar,E.;Rosell-Llompart,J.Journal of Colloid and Interface Science 2013,407,(0),536-545. 48. Hoang,A.;Pallon,L.;Liu,D.;Serdyuk,Y.;Gubanski,S.;Gedde,U.Polymers 2016,8,(3),87. 49. A.,N.F.;Alexandra,P.;F.,K.B.A.;Martin,D.;Markus,R.Advanced Materials 2018,30,(14),1704910. 50. Tang,K.;Gomez,A.Physics of Fluids 1994,6,(7),2317-2332. 51. Freeman,P.;Rowlinson,J.Polymer 1960,1,20-26. 52. Kay,D.;Styles,V.;Welford,R.Interfaces Free Bound 2008,10,(1),15-43. 53. Brown,E.;Zhang,H.;Forman,N.A.;Maynor,B.W.;Betts,D.E.;DeSimone,J.M.;Jaeger,H.M.Physical Review E 2011,84,(3),031408. 54. Bertrand,E.;Bibette,J.;Schmitt,V.Physical Review E 2002,66,(6),060401. 55. Banerjee,P.;Mandal,B.M.Macromolecules 1995,28,(11),3940-3943. 56. Park,M.;Im,J.;Shin,M.;Min,Y.;Park,J.;Cho,H.;Park,S.;Shim,M.-B.;Jeon,S.;Chung,D.-Y.;Bae,J.;Park,J.;Jeong,U.;Kim,K.Nat Nano 2012,7,(12),803-809. 57. Kim,Y.;Zhu,J.;Yeom,B.;Di Prima,M.;Su,X.;Kim,J.-G.;Yoo,S.J.;Uher,C.;Kotov,N.A.Nature 2013,500,(7460),59-63. 58. Balazs,A.C.;Emrick,T.;Russell,T.P.Science 2006,314,(5802),1107-1110. 59. Li,J.;Kim,J.-K.Composites Science and Technology 2007,67,(10),2114-2120. 60. Wang,Y.;Shan,J.W.;Weng,G.J.Journal of Applied Physics 2015,118,(6),065101. 61. Dhawan,S.K.;Singh,N.;Venkatachalam,S.Synthetic Metals 2001,125,(3),389-393. 62. Coleman,J.N.;Curran,S.;Dalton,A.B.;Davey,A.P.;McCarthy,B.;Blau,W.;Barklie,R.C.Physical Review B 1998,58,(12),R7492-R7495. 63. Winey,K.I.;Kashiwagi,T.;Mu,M.Mrs Bulletin 2007,32,(4),348-353. 64. Powell,M.Physical Review B 1979,20,(10),4194. 65. Narkis,M.;Lidor,G.;Vaxman,A.;Zuri,L.Journal of Electrostatics 1999,47,(4),201-214. 66. Kitano,M.;Shiojiri,M.Powder Technology 1997,93,(3),267-273. 67. Kuhn,H.H.,Characterization and Application of Polypyrrole-Coated Textiles.In Intrinsically Conducting Polymers:An Emerging Technology,Aldissi,M.,Ed.Springer Netherlands:Dordrecht,1993;pp 25-34. 68. Maleski,K.;Mochalin,V.N.;Gogotsi,Y.Chemistry of Materials 2017,29,(4),1632-1640. 69. Sprik,M.;Delamarche,E.;Michel,B.;Roethlisberger,U.;Klein,M.L.;Wolf,H.;Ringsdorf,H.Langmuir 1994,10,(11),4116-4130. 70. Lee,J.;Bong,J.;Ha,Y.-G.;Park,S.;Ju,S.Applied Surface Science 2015,330,445-448. 71. Kanta,A.;Sedev,R.;Ralston,J.Colloids and Surfaces A:Physicochemical and Engineering Aspects 2006,291,(1),51-58. 72. Kataby,G.;Prozorov,T.;Koltypin,Y.;Cohen,H.;Sukenik,C.N.;Ulman,A.;Gedanken,A.Langmuir 1997,13,(23),6151-6158. 73. Hoque,E.;DeRose,J.A.;Houriet,R.;Hoffmann,P.;Mathieu,H.J.Chemistry of Materials 2007,19,(4),798-804. 74. Kay,D.;Styles,V.; Welford.R Interfaces Free Bound 10.1(2008):15-43. 75. High-Efficiency Electrospray Deposition Method for Nonconductive Substrates:Applications of Superhydrophobic Coatings.Md.Khalilur Rahman,et al.ACS Appl.Mater.Interfaces 2021,13,15,18227-18236. 76. Self-Limiting Electrospray Deposition on Polymer Templates.Jonathan Singer,et al.Scientific Reports volume 10,Article number:17290(2020). 77. Electrospray Printing of Polyimide Films Using Passive Material Focusing.Bryce Kingsley,et al.ACS Appl.Polym.Mater.2021,3,6274-6284. 78. Determining the Self-Limiting Electrospray Deposition Compositional Limits for Mechanically Tunable Polymer Composites.Jonathan Singer,et al.ChemRxiv 2021. 79. Experimental Design and Instability Analysis of Coaxial Electrospray Process For Microencapsulation Of Drugs And Imaging Agents.Ting Si,et al.Journal of Biomedical Optics 2013,18(7):75003. 80. Continuous Equilibrated Growth of Ordered Block Copolymer Thin Films By Electrospray Deposition.Chinedum Osuji,et al.ACS Nano.2013,7(4),2960-2970 81. Morozov,V.N.and T.Y.Morozova(1999).”Electrospray Deposition as a Method for Mass Fabrication of Mono- and Multicomponent Microarrays of Biological and Biologically Active Substances.”Analytical Chemistry 71(15):3110-3117. 82. Blumberg,L.N.,et al.(1962).Electrospraying of Thin Targets,Los Alamos Scientific Laboratory. 83. Lei,L.,et al.(2018).”Obtaining Thickness-Limited Electrospray Deposition for 3D Coating.”ACS Appl Mater Interfaces 10(13):11175-11188. 84. Toth,K.,Osuji,C.O.,Yager,K.G.& Doerk,G.S.Comprehensive study on electrospray deposition in the single Taylor cone-jet mode by changing the spatial electric potential using a ring-shaped ternary electrode.Rev Sci Instrum 91,013701,doi:10.1063 / 1.5129625(2020). 85. Jaworek,A.,Sobczyk,A.T.& Krupa,A.Electrospray application to powder production and surface coating.Journal of Aerosol Science 125,57-92,doi:https: / / doi.org / 10.1016 / j.jaerosci.2018.04.006(2018). 86. Jaworek,A.& Krupa,A.Generation and characteristics of the precession mode of EHD spraying.Journal of Aerosol Science 27,75-82(1995). 87. Brown,N.A.,et al.(2017).”Structure of Electrospray Printed Deposits for Short Spray Times.”Journal of Micro and Nano-Manufacturing 5(4). 88. Kudoh,Y.,et al.(2014).”Control of the pretilt angle for liquid crystal alignment using novel electrospray deposition methods with two capillaries.”Journal of the Society for Information Display 22(7):357-363. 89. Rietveld,I.B.,et al.(2008).”Electrospray Deposition of Photoresist:A Low Impact Method for the Fabrication of Multilayered Films.”Macromolecular Materials and Engineering 293(5):387-399. 0. Arya,J.;Prausnitz,M.R.Microneedle Patches for Vaccination in Developing Countries.J.Controlled Release 2016,240,135-141. 91. Lei,L.;Gamboa,A.R.;Kuznetsova,C.;Littlecreek,S.;Wang,J.;Zou,Q.;Zahn,J.D.;Singer,J.P Scientific Reports,2020,10,17290 92. Shlyapnikov,M.Y.,Shlyapnikova,A.E.,Morozov,N.V.,Anal.Chem.,2016,88(14),pp 7295-7301. 93. Morozov,V.N.Electrospray Deposition of Biomolecules.Adv Biochem Eng Biotechnol 119,115-162(2009). 94. Fukuda,T.,Toda,A.,Takahira,K.,Kuzuhara,D.& Yoshimoto,N.Improved performance of organic photovoltaic cells with PTB7-Th:PC71 BM by optimized solvent evaporation time in electrospray deposition.Organic Electronics 48,96-105, doi:10.1016 / j.orgel.2017.05.049(2017). 95. Fukuda,T.et al.Improved Power Conversion Efficiency of Organic Photovoltaic Cell Fabricated by Electrospray Deposition Method by Mixing Different Solvents.Japanese Journal of Applied Physics 51,doi:10.1143 / jjap.51.02bk12(2012). 96. Ju.J,Yamagata,Y.& Higuchi,T.Thin-Film Fabrication Method for Organic Light-Emitting Diodes Using Electrospray Deposition.Advanced Materials 21(2009). 97. Zhang,S.& Kawakami,K.One-step preparation of chitosan solid nanoparticles by electrospray deposition.Int J Pharm 397,211-217,doi:10.1016 / j.ijpharm.2010.07.007 (2010). 98. Nagarajan,U.,Kawakami,K.,Zhang,S.,Chandrasekaran,B.& Nair,B.U.Fabrication of Solid Collagen Nanoparticles Using Electrospray Deposition.Chemical and Pharmaceutical Bulletin 62,422-428(2014). 99. Lee,S.J.,Park,S.M.,Han,S.J.& Kim,D.S.Electrolyte solution-assisted electrospray deposition for direct coating and patterning of polymeric nanoparticles on nonconductive surfaces.Chemical Engineering Journal 379,doi:10.1016 / j.cej.2019.122318(2020). 100. de Jonge,L.T.et al.The osteogenic effect of electrosprayed nanoscale collagen / calcium phosphate coatings on titanium.Biomaterials 31,2461-2469,doi:10.1016 / j.biomaterials.2009.11.114(2010). 101. Muller,V.,Jobbagy,M.& Djurado,E.Coupling sol-gel with electrospray deposition: Towards nanotextured bioactive glass coatings.Journal of the European Ceramic Society 41,7288-7300,doi:10.1016 / j.jeurceramsoc.2021.07.041(2021). 102. Gomez,A.,Binghamd,D.,de Juan,L.& Tang,K.Production of protein nanoparticles by electrospray drying.Journal of Aerosol Science 29,561-574(1998). 103. Morozov,V.N.& Morozov,T.Y.Electrospray Deposition as a Method To Fabricate Functionally Active Protein Films.Analytical Chemistry 71,1415-1420(1999). 104. Kovacevich,D.A.et al.Self-Limiting Electrospray Deposition for the Surface Modification of Additively Manufactured Parts.ACS Applied Materials & Interfaces 12, 20901-20911,doi:https: / / doi.org / 10.1021 / acsami.9b23544(2020). 105. Jaworek,A.Electrospray droplet sources for thin film deposition.Journal of Materials Science 42,266-297,doi:10.1007 / s10853-006-0842-9(2006). 106. Jaworek,A.& Sobczyk,A.T.Electrospraying route to nanotechnology:An overview. Journal of Electrostatics 66,197-219,doi:10.1016 / j.elstat.2007.10.001(2007). 107. Altmann,K.,Schulze,R.D.,Hidde,G.& Friedrich,J.Electrospray ionization for deposition of ultra-thin polymer layers - principle,electrophoretic effect and applications.J.Adhes.Sci.Technol.27,988-1005,doi:10.1080 / 01694243.2012.727170(2013). 108. Zhu,Y.& Chiarot,P.R.Surface charge accumulation and decay in electrospray printing.J.Phys.D:Appl.Phys.54,075301,doi:10.1088 / 1361-6463 / abc449(2020). 109. Lei,L.et al.Homogeneous gelation leads to nanowire forests in the transition between electrospray and electrospinning.Materials Horizons 7,2643-2650,doi:10.1039 / d0mh00872a(2020). 110. Toth,K.,Osuji,C.O.,Yager,K.G.& Doerk,G.S.Comprehensive study on electrospray deposition in the single Taylor cone-jet mode by changing the spatial electric potential using a ring-shaped ternary electrode.Rev Sci Instrum 91,013701,doi:10.1063 / 1.5129625(2020). 112. Gill,H.S.& Prausnitz,M.R.Coating formulations for microneedles.Pharm Res 24,1369-1380,doi:10.1007 / s11095-007-9286-4(2007). 113. Kim,Y.C.,Quan,F.S.,Compans,R.W.,Kang,S.M.& Prausnitz,M.R.Stability kinetics of influenza vaccine coated onto microneedles during drying and storage.Pharm Res 28, 135-144,doi:10.1007 / s11095-010-0134-6(2011). 114. Arya,J.& Prausnitz,M.R.Microneedle patches for vaccination in developing countries.J Control Release 240,135-141,doi:10.1016 / j.jconrel.2015.11.019(2016). 115. Bodnar,E.& Rosell-Llompart,J.Growth dynamics of granular films produced by electrospray.Journal of Colloid and Interface Science 407,536-545,doi:http: / / dx.doi.org / 10.1016 / j.jcis.2013.06.013(2013). 116. Ingrole,R.S.J.;Gill,H.S.J.Pharmacol.Exp.Ther.2019,370(3),555-569. 117. X.Cheng,I.I.D.G.Camp,Q.Wu,R.Bakhtiar,D.L.Springer,B.J.Morris,J.E.Bruce,G.A.Anderson,C.G.Edmonds,R.D.Smith,Nucleic Acids Res.1996,24,2183.

Claims

1. establishing an electric field in an electrospray deposition device and emitting a spray of a medium containing a payload material from an emitter within said electric field toward a conductive target disposed on an insulated conductor; disposing a charged payload material on the insulated conductor; establishing field lines in an electric field between the emitter and a charged payload material on the insulated conductor to stabilize the electric field and carry the spray of the medium between the emitter and the target to the target; The method includes:

2. 10. The method of claim 1, further comprising depositing the charged payload material onto the insulated conductor by allowing an initial overspray of the medium containing the charged payload material to reach the insulated conductor.

3. 10. The method of claim 1, further comprising: ensuring that when the electric field is present, insulating material on the insulated conductor creates electric field lines between the charged payload material on the insulated conductor and a conductor of the insulated conductor.

4. The method of claim 3 further comprising the step of maintaining the electrical conductor at a relatively lower or higher potential difference with the emitter than with the target.

5. The method of claim 4 further comprising the step of grounding the electrical conductor.

6. The method of claim 1 , further comprising ensuring that the electric field lines between the emitter and the charged payload material on the insulated conductor completely surround the target.

7. The method of claim 1 further comprising the step of directing the spray of the medium by electric field lines between the emitter and the target.

8. The method of claim 1 , further comprising applying a mask to a portion of the target.

9. aligning the spray of the medium with the electric field lines between the emitter and the target; 1) separating electric field lines between the emitter and unmasked portions of the target from other electric field lines; 2) assisting in focusing the spray of the medium at the electric field lines between the emitter and the unmasked portions of the target; and 3) thereby ensuring that the electric field lines between the emitter and the mask are less dense than the electric field lines between the emitter and the charged payload material on the insulated conductor in order to focus the spray of the medium at the unmasked portions of the target. The method of claim 8 further comprising:

10. The method of claim 1 , further comprising ensuring that the conductor mass of the insulated conductors is at least 1000 times the mass of the target.

11. establishing an electric field between an emitter and an insulated conductor in an electrospray deposition apparatus; disposing a target on the insulated conductor; directing a spray of medium toward the target; allowing an initial overspray of the spray to reach the insulated conductor; The method includes:

12. The method of claim 11 further comprising the step of allowing the initial overspray to reach a mask on the target.

13. 12. The method of claim 11, wherein the insulated conductors establish an insulator profile as seen by the emitter, the method further comprising ensuring that the target is located entirely within the insulator profile as seen by the emitter.

14. The method of claim 13 further comprising maintaining a distance of at least one centimeter between the target and the entire perimeter of the insulator profile as viewed from the emitter.

15. 14. The method of claim 13, wherein the insulator profile establishes an insulator profile area, the target establishes a target profile as seen from the emitter, the target profile establishes a target profile area, the method further comprising ensuring that the insulator profile area is at least 100 times the target profile area.

16. The method of claim 11 , further comprising ensuring that the conductor mass of the insulated conductors is at least 1000 times the mass of the target.

17. subjecting a stream of medium from a capillary to a relatively high electric field to form a spray of droplets of said medium; directing the spray towards a target disposed on an insulating surface disposed on a conductor maintained at a potential difference with the medium in the capillary; causing an initial overspray of the spray; ensuring that the initial overspray lands on the insulating surface adjacent the target; The method includes:

18. The method of claim 17 further comprising ensuring that the initial overspray surrounds the entire perimeter of the target.

19. The method of claim 17 further comprising ensuring that the initial overspray is located within an electric field created by a relatively high potential difference.

20. The method of claim 19 , wherein the potential difference arises from a grounded object.

21. The method of claim 17 further comprising applying an insulating mask to a portion of the target.

22. 20. The method of claim 17, further comprising applying a pre-spray to the target and the insulating surface to dissipate or apply an electric charge.

23. 20. The method of claim 17, further comprising focusing the spray using a focus ring disposed around the spray.

24. An apparatus comprising: an electrospray deposition emitter configured to generate a spray of a medium toward a target and to be maintained at or above a first electrical potential magnitude; an extractor target comprising: an electrical conductor configured to be maintained at a potential magnitude lower or higher than the first potential magnitude and defining a support surface; an insulating material on the support surface; and a charged payload material disposed on the support surface; An apparatus comprising:

25. 25. The apparatus of claim 24, wherein the first electrical potential is configured to generate an electric field, the electric field being sufficient to cause electric field lines to form between the charged payload material and the electrical conductor.

26. 25. The apparatus of claim 24, wherein the electrical conductor is grounded.

27. 25. The apparatus of claim 24, further comprising a focus ring configured to constrict the spray radially inward as the spray passes through the focus ring.

28. 25. The apparatus of claim 24, further comprising a controller configured to control at least one of the first electrical potential and a flow rate of the medium.

29. An apparatus comprising: a capillary configured to pass and release a flow of a medium therethrough; and an extractor target comprising a conductor configured to define a support surface facing the capillary, and an insulator on the support surface; a high voltage source configured to generate a potential that will cause the stream exiting the capillary to disperse into a spray of charged droplets directed towards the support surface, and configured to generate an electric field between the capillary and a target on the support surface at different potentials; An apparatus configured such that the electrical conductor of the extractor target is maintained at a lower potential than the relatively high voltage generated by the high voltage source.

30. 30. The apparatus of claim 29, further configured to cause an initial overspray of the spray to reach the support surface, the electric field configured to generate electric field lines between the capillary and media from the initial overspray disposed on the support surface.

31. 30. The apparatus of claim 29, wherein the electrical conductor is grounded.

32. 30. The apparatus of claim 29, further comprising a focus ring configured to constrict the spray radially inward as the spray passes through the focus ring.

33. 30. The apparatus of claim 29, further comprising a controller configured to control generation of at least one of the electric field and the flow rate of the medium.

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