High-reliability armored aerosol flow diverter

Abstract

A method and apparatus for splitting an aerosol stream into a plurality of streams prior to deposition. The aerosol stream is surrounded by the sheath gas stream in each outlet. Adjusting the sheath gas flow in each outlet determines the amount of aerosol delivered through each of the outlets, if any. For example, the sheath flow in an outlet may be increased until all of the aerosol streams passing through the outlet are diverted to one or more other outlets. One of the outlets may be an exhaust outlet that may exhaust all of the aerosol generated by the system if the flow of aerosol in the other outlet is stopped, thus preventing material settling and achieving a fast shut-off rate in combination with increasing the flow of sheath gas in the other outlet. The sheath gas prevents the aerosolized material from accumulating on the bottom of the splitter chamber and inside the outlet.

Description

[0001] Cross - Reference to Related Applications

[0002] This application claims priority and the benefit of U.S. Provisional Patent Application No. 63 / 428,700, filed on November 29, 2022, entitled "HIGH RELIABILITY SHEATHED AEROSOL FLOW SPLITTER", the entire content of which is incorporated herein by reference. Technical Field

[0003] The present invention relates to devices and methods for propagating an aerosol stream and splitting the aerosol stream into separate discrete streams. The aerosol stream can be a stream of droplets, a stream of solid particles, or a stream comprising droplets and solid particles or droplets containing solid particles. Background Art

[0004] Note that the following discussion may refer to many publications and references. The discussion of such publications herein is given for a more complete background of scientific principles and should not be construed as an admission that such publications are prior art for purposes of patentability determination.

[0005] Typical methods for splitting an aerosol stream in an aerosol jet printing device mimic methods of pneumatic flow splitting and are achieved by means of standard pipe connections (e.g., T - fittings and manifolds). Aerosol particles generally follow the pneumatic flow pipeline, resulting in aerosol delivery; however, depending on the flow velocity, losses of the aerosol along the delivery path may occur due to gravitational settling and particle impingement. Material accumulation caused by the delivery losses typically reduces the transport efficiency in as little as 4 to 8 hours and results in reduced system performance, throughput, and system runtime.

[0006] Multi - nozzle aerosol jet applications that print multiple identical features simultaneously to increase system throughput require flow splitting if one aerosol generation source is used to supply all deposition nozzles. The balance of the aerosol flow across the aerosol streams created by the splitting determines the degree to which the features match each other. Imbalances in the aerosol flow result in reduced print quality because the features deviate from each other in size or shape. Special chambers with one aerosol input and multiple outputs, which are optimized to perform the task of splitting the aerosol, can achieve <20% matching across the outputs and are related to the aerosol particle diameter and flow rate. These chambers suffer from gravitational settling losses and reliability challenges similar to those of tees and standard manifolds. There is a need for flow splitting that balances the flow across the output flow channels and has a performance that supports a runtime of greater than 8 hours.

[0007] In a traditional aerosol jet printing system, the material to be printed is delivered to a printing nozzle via a carrier gas introduced into an atomizer, and the carrier gas is mixed with droplets or particles generated by the atomizer to form an aerosol, which is transported to a deposition nozzle where an outer flow is added to effect printing. The amount of material to be printed is directly controlled and is proportional to the carrier gas flow rate. To reduce the mass flow rate, the carrier gas flow rate must also be reduced. When the carrier gas flow rate is low, the aerosol droplets and / or particles settle out of the flow, resulting in a reduction or even complete loss of mass output. Additionally, in many systems, a pneumatic gate is inserted between the atomizer and the printing nozzle to open and close the aerosol flow, thereby initiating and terminating various printed features. In this configuration, the speed at which the gate can operate directly depends on the carrier gas flow rate. If the carrier gas flow rate is very small, it takes more time to clear or fill the internal cavity of the pneumatic gate, resulting in slower gate opening and closing times and lower precision in the details of the printed features. Summary of the Invention

[0008] An embodiment of the present invention is a method of depositing a material, the method comprising: atomizing the material to form an aerosol; transporting the aerosol into a chamber, the chamber including a plurality of outlets, each outlet providing a resistance to the aerosol flow; varying the resistance to the aerosol flow for each outlet, thereby directing the aerosol flow to one or more of the outlets at a predetermined amount of aerosol flow rate for each outlet; and depositing the material. The resistance to the aerosol flow for each outlet preferably includes surrounding the aerosol flow in each outlet with a sheath gas, and setting the flow rate of the sheath gas in each outlet to achieve the predetermined amount of aerosol flow in each outlet. Increasing the flow rate of the sheath gas in the outlet preferably reduces the aerosol flow rate in the outlet, which preferably results in an increase in the aerosol flow rate in one or more other outlets. The flow rate of the sheath gas in the outlet can alternatively be increased sufficiently to stop the aerosol flow in the outlet. Reducing the flow rate of the sheath gas in the outlet preferably increases the aerosol flow rate in the outlet. The sum of all the sheath gas flow rates and all the aerosol flow rates leaving all the outlets is preferably substantially constant, regardless of the aerosol flow rate in any individual outlet. The method preferably includes measuring the aerosol flow rate in each outlet, and preferably using a mass flow controller to control the flow rate of the sheath gas in each outlet to achieve the predetermined amount of aerosol flow in each outlet. Setting the flow rate of the sheath gas in each outlet is performed such that the sum of the flow rate of the sheath gas and the aerosol flow rate in each outlet is substantially constant, regardless of the amount of aerosol flow in the outlet. One of the outlets preferably includes an exhaust outlet, in which case the method includes discharging the aerosol through the exhaust outlet. The sum of the aerosol flow rates in all the outlets is preferably constant, regardless of the amount of aerosol flow in any individual outlet. The flow rate of the sheath gas in all the outlets other than the exhaust outlet can alternatively be increased sufficiently such that preferably substantially without reducing the velocity of the aerosol flow, all the aerosol entering the chamber is discharged through the exhaust outlet. The method preferably further includes closing the aerosol flow rate and the sheath gas flow rate in at least one of the outlets. The sheath gas is preferably introduced into the chamber and travels along the bottom surface of the chamber before entering each of the outlets. The sheath gas preferably prevents the material from accumulating on the inner walls of the outlets and on the bottom surface of the chamber. At least one of the outlets preferably includes a fog tube.

[0009] The objects, advantages and novel features of the present invention, as well as the further scope of application, will be partly described in the following detailed description in conjunction with the accompanying drawings, and will become partly apparent to those skilled in the art upon studying the following content, or may be learned through the practice of the present invention. The objects and advantages of the present invention can be achieved and obtained by the means and combinations particularly pointed out in the appended claims. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] The drawings incorporated in and forming a part of the specification illustrate the practice of embodiments of the present invention and, together with the specification, are used to explain the principles of the present invention. The drawings are only for the purpose of illustrating certain embodiments of the present invention and should not be construed as limiting the present invention. In the drawings:

[0011] Figure 1 is a schematic view showing an embodiment of an aerosol delivery path of an aerosol jet printing engine that splits into three streams and shows the flow rate and aerosol distribution.

[0012] Figure 2 is a schematic view showing the flow rate and aerosol distribution within the split aerosol stream Figure 1 of the single fog tube assembly 2.

[0013] Figure 3 is a schematic view of an embodiment of an aerosol delivery path of an aerosol jet printing engine having non-uniform flow rate and non-uniform aerosol distribution.

[0014] Figure 4 is a schematic view of the flow rate and aerosol distribution when all aerosol streams are directed out of a split.

[0015] Figure 5 is a schematic view of the flow rate and aerosol distribution when the aerosol stream splits between the nozzle and the exhaust valve. DETAILED DESCRIPTION

[0016] The present invention relates to an apparatus and method for splitting and adjusting an aerosol stream in an aerosol deposition system. As used throughout the specification and claims, the term "aerosol" or "fog" means liquid droplets (which may optionally contain suspended solid materials), fine solid particles, or mixtures thereof, transported by a carrier gas.

[0017] In one or more embodiments of the present invention, the aerosol delivery path is incorporated into an apparatus for transporting material from an aerosol source (e.g., an ultrasonic or pneumatic nebulizer) to a deposition nozzle. Before entering the deposition nozzle, a concentric gas sheath is applied around the aerosol stream. When the combined stream flows through the nozzle, aggregation of the aerosol occurs, resulting in the deposition of printing features as small as 10 μm in width.

[0018] An embodiment of the present invention is a method for equally splitting an aerosol stream among nozzles as illustrated in Figure 1 . The aerosol stream 1 enters at the top of the flow splitting chamber 3 and is split into three split outputs 5, 7, 9 flowing respectively to the fog tubes 11, 13, 15. At the same time, sheath gases 23, 25, 27 enter the sheath gas pressurizing chambers 31, 33, 35 and are preferably injected circumferentially into the flow splitting chamber 3 around the outer diameter of each fog tube 11, 13, 15. The sheath gases preferably focus the aerosol streamlets emerging from the deposition nozzle tip, resulting in the deposition of the printing features 17, 19, 21. Although three split outputs are shown, any number of flow outputs may be present. Figure 2 Details of the flow in a single sheath gas pressurizing chamber and fog tube are shown in

[0019] The fog tubes preferably act as flow restrictors to limit the flow of the aerosol, thereby providing a resistance that can be utilized to produce a controlled, varying aerosol stream at various outlets. Varying the amount of the sheath flow in combination with a fixed flow resistance acts to cause the fog to select one path or the other. Flow restrictors (such as nozzles, fog tubes, orifices, or channels) that provide resistance to the aerosol stream are preferably located at each of the outlets of the flow splitting chamber 3. In an embodiment of the present invention, the amount of flow in each fog tube (or other flow restriction) is preferably determined by the sheath flow rate in that fog tube, and the sheath flow rate preferably displaces the corresponding aerosol flow rate in that fog tube. Thus, by varying the amount of sheath flow in each fog tube, the user can determine the relative aerosol flow rate in the fog tubes, including but not limited to splitting the flow and redirecting the aerosol stream from one or more outlets to one or more other outlets as needed.

[0020] The flow rate of the output aerosol stream passing through the fog tube is preferably inversely proportional to the flow rate of the sheath gas in that tube. For example, in Figure 3In this case, the flow rates of each split output are not equal; the flow rate of the sheath gas 46 in the mist tube 52 is higher than the flow rate of the sheath gas 50 in the mist tube 56, and the flow rate of the sheath gas 50 in the mist tube 56 is higher than the flow rate of the sheath gas 48 in the mist tube 54, which means that the output flow rate 40 is less than the output flow rate 44, and the output flow rate 44 is less than the output flow rate 42. Therefore, in addition to the resistance to the flow of the mist tube itself, the sheath flow rate in the mist tube can also act as a flow restrictor to limit the flow of the aerosol in that mist tube. The sheath flow rate in one or more mist tubes can be increased such that the flow of the aerosol in each of those tubes stops. The flow rate of each sheath flow is preferably set by a mass flow controller. The method further optionally includes: after splitting the aerosol flow, measuring the aerosol flow rate of each split output and adjusting the sheath flow rate to achieve a balanced or target output value for each output.

[0021] In yet another embodiment of the present invention, as illustrated in Figure 4 the aerosol stream is stopped in all flow outputs except for one flow output. Preferably, the aerosol stream 60 is directed towards one split output 62 by increasing the sheath flow rates 64, 66 in the corresponding sheath gas plenum chambers 63, 65 such that the aerosol flow is cut off in the corresponding mist tubes 70, 72. The sum of all flows into and out of the flow splitter is preferably kept substantially constant. When the sheath flow rates 64, 66 are increased in their respective sheath gas plenum chambers 63 and 65, the sheath flow rate 68 in the corresponding sheath gas plenum chamber 67 is preferably decreased by an amount equal to the sum of the increase in the sheath gas flow rate 64 and the increase in the sheath gas flow rate 66. Increasing the sheath gas flow rates 64, 66 displaces the aerosol flow that would otherwise enter the mist tubes 70, 72 such that the output aerosol only flows in the mist tube 74.

[0022] In another embodiment of the present invention, the aerosol stream is split between a mist tube 86 and an exhaust outlet 84, as shown in Figure 5 The exhaust flow rate 80 is preferably such that, by diverting excess aerosol away from the system as an exhaust stream 80 through the exhaust outlet 84, the aerosol flow rate when the aerosol 82 travels from the atomizer to the aerosol flow splitting location 88 is maintained high even when the output aerosol flow rate 81 is low or stopped. This minimizes the mass output loss due to gravitational settling (which occurs at low flow rates). This diversion is preferably accomplished by varying the sheath gas flow rate 85 and the exhaust outlet sheath gas flow rate 87 relative to each other. For example, the sheath gas flow rate 85 can optionally be increased sufficiently to deflect all the aerosol from the mist tube 86, and the exhaust outlet sheath gas flow rate 87 is preferably decreased by a substantially equal amount to extract the additional deflected aerosol through the exhaust outlet 84.

[0023] Flow splitting can be utilized in conjunction with a gate 83 that preferably includes a pneumatic gate. As described above, a relatively high and constant flow rate through the gate 83 is preferred to maintain a fast switching time of the gate 83, which is defined as less than about 20 ms. Since the total gas flow rate through the gate 83 is a combination of the sheath gas flow rate 85 and the output aerosol flow rate 81, when it is desirable to reduce the output aerosol flow rate 81, some or all of the output aerosol flow rate 81 is diverted to the exhaust outlet 84. The sheath gas flow rate 85 is preferably increased to maintain a constant, relatively high total flow rate through the gate 83, thereby achieving a fast gate switching time. This also enables the aerosol flow rate in the system to remain constant and relatively high even when the output aerosol flow rate 81 is low (or stopped), thus preventing mass sedimentation as described above. In this way, the total combined flow rate flowing out of the fog tube 86 and the exhaust outlet 84 preferably remains constant, while the output aerosol flow rate 81 through the gate 83 can preferably vary from 0 to 100%. Therefore, the amount of aerosol traveling to the printing nozzle (i.e., the fog tube 86) is preferably adjusted independently of the aerosol flow rate in the system, and the amount of gas flowing through the gate 83 can be maintained at a high rate independently of the amount of aerosol material.

[0024] Note that in the specification and claims, "about" or "approximately" means within twenty percent (20%) of the recited numerical amount. Unless the context clearly dictates otherwise, as used herein, the singular forms "a", "an", and "the" include plural referents. Thus, for example, a reference to "functional group" refers to one or more functional groups, and a reference to "method" includes references to equivalent steps and methods that will be understood and appreciated by those skilled in the art, and so on.

[0025] Although the invention has been particularly described in detail with reference to the disclosed embodiments, other embodiments can achieve the same results. Variations and modifications of the invention will be apparent to those skilled in the art and are intended to cover all such modifications and equivalents. The entire disclosure of all patents and publications cited above is hereby incorporated by reference.

Claims

1. A method of depositing a material, the method comprising: atomizing the material to form an aerosol; delivering the aerosol into a chamber, the chamber including a plurality of outlets, each outlet providing a resistance to the aerosol flow; varying the resistance of each outlet to the aerosol flow, thereby directing the aerosol flow to one or more of the outlets with a predetermined amount of aerosol flow for each outlet; and depositing the material.

2. The method according to claim 1, wherein, The resistance of each outlet to the aerosol flow includes: surrounding the aerosol flow in each outlet with a sheath gas and setting the flow rate of the sheath gas in each outlet to achieve the predetermined amount of aerosol flow in each outlet.

3. The method according to claim 2, wherein Increasing the flow rate of the sheath gas in an outlet reduces the aerosol flow in that outlet.

4. The method according to claim 3, wherein, Reducing the aerosol flow in an outlet causes an increase in the aerosol flow in one or more other outlets.

5. The method according to claim 3, including sufficiently increasing the flow rate of the sheath gas in the outlet to stop the aerosol flow in the outlet.

6. The method according to claim 2, wherein, Reducing the flow rate of the sheath gas in an outlet increases the aerosol flow in that outlet.

7. The method according to claim 2, wherein Regardless of the aerosol flow in any individual outlet, the total amount of all sheath gas flows and all aerosol flows exiting all the outlets is substantially constant.

8. The method according to claim 2, including measuring the aerosol flow rate in each outlet and controlling the flow rate of the sheath gas in each outlet to achieve the predetermined amount of aerosol flow in each outlet.

9. According to the method of claim 8, wherein Using a mass flow controller to perform the control of the flow rate of the sheath gas.

10. The method according to claim 2, wherein The setting of the flow rate of the sheath gas in each outlet is performed such that, regardless of the amount of aerosol flow in the outlet, the total amount of the sheath gas flow and the aerosol flow in each outlet is substantially constant.

11. The method according to claim 10, wherein, One of the outlets includes an exhaust outlet, and the method includes discharging the aerosol through the exhaust outlet.

12. The method according to claim 11, wherein, Regardless of the amount of aerosol flow in any individual outlet, the total amount of the aerosol flow in all the outlets is constant.

13. The method according to claim 12, comprising: Sufficiently increasing the flow rate of the sheath gas in all the outlets except the exhaust outlet such that all the aerosol entering the chamber is discharged through the exhaust outlet.

14. The method according to claim 13, performing the method with substantially no reduction in the velocity of the aerosol flow.

15. The method according to claim 11, further including closing the aerosol flow and the sheath gas flow in at least one of the outlets.

16. The method according to claim 2, wherein, The sheath gas is introduced into the chamber and travels along the bottom surface of the chamber before entering each of the outlets.

17. The method according to claim 16, wherein, The sheath gas prevents the material from accumulating on the inner walls of the outlets and the bottom surface of the chamber.

18. The method according to claim 1, wherein, At least one of the outlets includes a mist tube.

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