Patent Application
20210070043
The present disclosure relates generally to printing and, more particularly, to electrohydrodynamic printing.
Electrohydrodynamic printing, also known as e-jet printing, is a printing technique that relies on an electric field to extract droplets of a charged or polarized printing fluid from a printing nozzle. E-jet printing is capable of very high-resolution printing compared to other drop-on-demand printing methods with droplet size and spatial accuracy on a sub-micron or nanometer scale. Early e-jet printing was limited to electrically conductive printing surfaces because the printing surface was one of the electrodes between which the electric field was produced. Consistency with the electric field was also problematic due to the deposited ink causing interference with the field as printing progressed. U.S. Pat. No. 9,415,590 to Barton, et al. addressed these and other problems via clever ink extraction and directing techniques that did not rely on a conductive printing surface. Other obstacles to larger-scale commercialization remain.
In accordance with various embodiments, an electrohydrodynamic print head includes a plurality of nozzles and a common electrode at a fixed position relative to the nozzles. The print head is configured to provide separately controllable electrostatic fields between the common electrode and each nozzle.
In some embodiments, the common electrode includes a plurality of extraction openings. Each extraction opening is aligned with one of the nozzles such that printing fluid extracted from each nozzle passes through the respective extraction opening for deposition on a printing surface.
In some embodiments, the common electrode extends between adjacent nozzles in an axial direction of the nozzles to thereby shield the separately controllable electrostatic fields from each other.
In some embodiments, the print head is configured to provide a gas flow field in a direction toward a printing surface and in which printing fluid extracted from one or more of the nozzles travels toward the printing surface.
In some embodiments, the print head is configured to provide a plurality of separately controllable gas flow fields. Each gas glow field flows along one of the nozzles and in a direction toward a printing surface such that printing fluid extracted from each nozzle travels toward the printing surface in the respective gas flow field.
In some embodiments, the print head includes a plurality of extraction electrodes. Each extraction electrode is arranged to provide one of the separately controllable electrostatic fields when a voltage potential relative to the common electrode is applied to the respective extraction electrode.
In some embodiments, each nozzle comprises one of a plurality of extraction electrodes.
In some embodiments, the print head is configured to provide separately controllable back pressure on a printing fluid in each nozzle.
In some embodiments, each nozzle contains a different printing fluid.
In some embodiments, each nozzle contains the same printing fluid.
In some embodiments, each nozzle is spaced from the common electrode by a different amount in an axial direction.
In some embodiments, each nozzle includes an extraction opening at a tip of the nozzle, and each extraction opening has a different size.
In some embodiments, the print head includes a carrier and a printer cartridge. The printer cartridge includes a housing, the plurality of nozzles, and the common electrode. The carrier supports the printer cartridge for relative movement over a printing surface. The housing provides connectivity for a voltage source for an extraction electrode, a pressurized gas source for a gas flow field in which extracted printing fluid travels toward the printing surface, and/or a backpressure source for application to printing fluid in the nozzles.
In some embodiments, a printer cartridge is removably supported by a carrier for replacement with a different printer cartridge comprising a housing with connectivity for a voltage source, a pressurized gas source, and/or a backpressure source.
In accordance with various embodiments, an electrohydrodynamic printing system includes a plurality of printer cartridges and a carrier. Each printer cartridge includes a housing, a plurality of nozzles, and a common electrode at a fixed position relative to the nozzles. The carrier is configured to interchangeably support each one of the printer cartridges individually for relative movement over a printing surface. The housing of each printer cartridge provides connectivity for at least one of the following when the corresponding printer cartridge is being supported by the carrier: a voltage source for an extraction electrode of the cartridge, a pressurized gas source for a gas flow field in the cartridge in which extracted printing fluid travels toward the printing surface, and a backpressure source for application to printing fluid in the nozzles of the cartridge. The printing system is configured to provide separately controllable electrostatic fields between the common electrode and each nozzle of the same cartridge when the respective cartridge is being supported by the carrier.
In some embodiments, each nozzle of each cartridge is configured for a respective printing fluid, an extraction opening of each nozzle and a distance of each nozzle from the common electrode are a function of the respective printing fluid, and at least one of the nozzles of one of the cartridges is configured for a different printing fluid than another one of the nozzles of one of the cartridges.
In some embodiments, a first one of the cartridges is configured for use with a first printing fluid in each nozzle and a second one of the cartridges is configured for use with a different second printing fluid in each nozzle.
In some embodiments, one of the nozzles of one of the cartridges is configured for use with a different printing fluid than another one of the nozzles of the same cartridge.
It is contemplated that any number of the individual features of the above-described embodiments and of any other embodiments depicted in the drawings or the description below can be combined in any combination to define an invention, except where features are incompatible.
One or more embodiments of the invention will hereinafter be described in conjunction with the appended drawings, wherein like designations denote like elements, and wherein:
The print head 10 may be part of a larger e-jet printer or printing system, as described further below and which may include a movement system 18 configured to provide relative movement between the print head 10 and the substrate 16 such that the print head can be guided along a deposition pattern or path defined over the substrate. Multi-axis movement systems are generally known and may include axis-dedicated servos, guides, wheels, gears, belts, etc. One example of a suitable movement system 18 is disclosed by Barton et al. in U.S. Pat. No. 9,415,590. The movement system 18 may be configured to move the print head 10 back and forth along an axis while the substrate 16 is incrementally fed in a perpendicular direction after each pass of the print head, or the print head can be configured to move in any direction along a plane or three-dimensional contour while the substrate is held stationary. The print head 10 and/or the substrate 16 may be configured for relative translational movement in up to all three cartesian coordinate directions, for rotational movement about the associated axes, and for any combination of such movements to allow the print head to deliver printing fluids 12 in any direction and along any path on a substrate of any shape. The print head 10 could be affixed to the end of a robotic arm, for example.
The print head 10 of
A baseline voltage with respect to the common electrode 22 may be maintained at each extraction electrode 24 to maintain a consistent Taylor cone of polarized printing fluid 12 at the tip of each nozzle 20 for extraction. When a sufficiently high voltage V1-V4 is applied to any one or more of the extraction electrodes 24, a droplet 26 of printing fluid 12 is released from the respective nozzle 20 and drawn in a direction toward the printing surface 14 via the net electrostatic force in that direction. Exemplary extraction voltages V1-V4 may range from 300V to 1000V, while the baseline voltage at each electrode 24 is lower than the respective extraction voltage, such as in a range from 10V to 300V. In various embodiments, the baseline voltage at each electrode 24 ranges from 200V to 300V and/or the extraction voltage ranges from 400V to 700V. These voltages depend on several factors, including the stand-off height H1-H4 of each nozzle 20 and various characteristics of the respective printing fluid 12 in each nozzle, such as viscosity, solids content, electrical conductivity, and polarizability, for example.
Stand-off height is a term of art related to conventional e-jet printing performed on a conductive substrate and is defined as the distance between the electrodes that generate the electrostatic field. In this case, each of the four illustrated nozzles 20 has a respective stand-off height H1-H4 measured between the common electrode 22 and the corresponding extraction electrode 24. Exemplary ranges for stand-off height H1-H4 are between 5 μm and 100 μm, between 10 μm and 60 μm, between 15 μm and 50 μm, between 20 μm and 40 μm, and between 25 μm and 35 μm. In some cases, such as when a relatively lower printing resolution is desired, the stand-off height can be up to 500 μm, or even up to 1 mm. Other exemplary ranges may be defined among any combination of the endpoints of these ranges. The stand-off height H1-H4 associated with each nozzle 20 may be a fixed distance for a given print head 10, and each stand-off height may have a particular value associated with a particular printing fluid composition. As illustrated in
The voltages V1-V4 at the extraction electrodes 24 are individually controllable, such as by a system controller. This control may include the magnitude, polarity, timing relative to print head and substrate positioning, pulse width, and pulse frequency of each applied voltage. The voltages V1-V4 may be applied as individually controllable electrical pulses having a pulse width ranging from 0.01 to 100 milliseconds. One non-limiting pulse width range is from 0.5 to 20 milliseconds. The size of the droplets 26 of printing fluid 12 is a function of pulse width, among other variables, such that pulse width may be one variable that affects the printing resolution. In the illustrated example, V1 may be applied with a smaller pulse width and at a greater frequency than V4, for example. As such, the illustrated print head 10 can simultaneously print multiple printing fluids 12 at different resolutions and/or with different printed line widths.
The common electrode 22 in the embodiment of
The common electrode 22 of
The gas or gases of each gas flow field 28 can serve other functions in addition to droplet directionality. For instance, the gas may include one or more constituents that promote curing of the printing fluid 12 once deposited. In one example, one of the gas flow fields 28 includes nitrogen in an amount higher than atmospheric air, such as substantially pure nitrogen, which is necessary for some functional inks to cure. In other examples, the flow field 28 is of a gas that is at least partially an inert gas (e.g., argon), which may serve to exclude reactive gases like oxygen from the droplets 26 of printing fluid during deposition. In another example, the gas includes water vapor which may promote curing of moisture-cure printing fluids. In some cases, one or more of the gas flow fields 28 may be made up of atmospheric air. The gas flowing along the channels 34 and in each gas flow field 28 may be heated or otherwise be maintained at a controlled temperature. The composition, temperature, and flow characteristics (e.g., pressure and flow rate) of the gas flow fields 28 and the gases in the flow channels 34 may be the same as or different from each other and individually controllable for each nozzle 20.
The illustrated print head 10 is also configured to provide separately controllable back pressure on the printing fluid 12 in each nozzle 20. The amount of back pressure P1-P4 in each nozzle may range from 5 psi to 30 psi (˜35-200 kPa), depending on factors such as printing fluid viscosity. The back pressures are provided to ensure that the printing fluid 12 is continuously replenished at the tip of each nozzle as droplets 26 are extracted and deposited.
The size of an extraction opening 38 at the tip of each nozzle 20 may also vary among the nozzles of the print head 10. Depicted in
In a practical example, the illustrated print head 10 can fabricate a thermocouple on the printing surface 14. With reference to
An e-jet print head 10 is thus provided with multiple nozzles 20, each of which has its individual electrohydrodynamics determined by different voltage signals, back pressures, gas flow fields, stand-off heights, and nozzle size. For a given nozzle size (D1-D4) and stand-off height (H1-H4), each printing fluid 12 can be printed within a pre-determined resolution range by varying the corresponding voltage signal (V1-V4) to provide different jetting frequencies and droplet sizes.
In another implementation depicted in
A larger scale nozzle array is thus provided with multiple print head modules for different printing fluids and/or resolution. A gantry system or robot arm can pick-up and connect to one or more of the modules at a time and print different features accordingly. Each different module 40 can also be provided with different gas flow field compositions specific to the printing fluid(s) of the module.
An e-jet printing system 100 employing such a multi-module configuration is illustrated schematically in
Each printer cartridge 40 includes a housing 52, a plurality of nozzles 20, and a common electrode 22 at a fixed position relative to the nozzles as discussed above. The carrier 42 is configured to interchangeably support each one of the printer cartridges 40-40″ individually for relative movement over the printing surface 14. In some embodiments, the carrier 42 interchangeably supports more than one cartridge at a time, or the system 100 includes more than one separately operable carrier. The carrier 42 and the cartridge 40 being supported by the carrier at any given time together form the print head 10 of the system 100 such that a portion of the print head is interchangeable depending on the desired printing fluid or combination of printing fluids.
Each housing 52 provides connectivity for the controlled voltages V1-V3, the controlled back pressures P1-P3, and the controlled gases G1-G3 of the gas flow fields, each of which is provided at the carrier 42 by electrodes or fluid fittings for connection with the cartridge housing when the respective cartridge is fitted into and supported by the carrier. Each housing 52 of the various cartridges is equipped with the same connectivity so that they can be interchanged in and out of the carrier 42. The housing 52 of each cartridge may be formed by the common electrode 22 as in
Each cartridge can be configured as in the print head of
It is to be understood that the foregoing description is of one or more embodiments of the invention. The invention is not limited to the particular embodiment(s) disclosed herein, but rather is defined solely by the claims below. Furthermore, the statements contained in the foregoing description relate to the disclosed embodiment(s) and are not to be construed as limitations on the scope of the invention or on the definition of terms used in the claims, except where a term or phrase is expressly defined above. Various other embodiments and various changes and modifications to the disclosed embodiment(s) will become apparent to those skilled in the art.
As used in this specification and claims, the terms “e.g.,” “for example,” “for instance,” “such as,” and “like,” and the verbs “comprising,” “having,” “including,” and their other verb forms, when used in conjunction with a listing of one or more components or other items, are each to be construed as open-ended, meaning that the listing is not to be considered as excluding other, additional components or items. Further, the term “electrically connected” and the variations thereof is intended to encompass both wireless electrical connections and electrical connections made via one or more wires, cables, or conductors (wired connections). Other terms are to be construed using their broadest reasonable meaning unless they are used in a context that requires a different interpretation.
| Number | Date | Country | |
|---|---|---|---|
| 62898193 | Sep 2019 | US |
