The invention relates to depositing particles.
Direct-write printing has enabled the rapid growth of the flexible and organic electronics industries. However, the spatial resolution of dominant printing technologies such as inkjet is insufficient to fabricate high-performance devices. In addition, printing methods that result in random distributions of solid materials on a substrate limit feature geometry and performance.
Particles can be individually placed on a surface by controlling particle ejection from an orifice. The control can be implemented by adjusting local electric or magnetic fields at or near the point of ejection.
In one aspect, a method of delivering a particle can include providing a liquid including a particle to an exit orifice, sensing a condition at a meniscus of the liquid at the orifice, and applying an electromagnetic signal near the orifice for timed particle ejection based on the sensed condition to deliver the particle from the orifice after applying the electromagnetic signal.
In certain embodiments, the electromagnetic signal can include an electric signal, a magnetic signal, or a combination thereof. In other embodiments, the electromagnetic boundary condition can be an electric boundary condition, a magnetic boundary condition, or a combination thereof.
In certain embodiments, the electromagnetic signal can be AC or DC. The electromagnetic signal can be constant or varying. A single particle can be specifically printed.
In certain embodiments, the method can include sensing an electromagnetic boundary condition. The method can include sensing a liquid flow boundary condition. The method can include applying an electromagnetic signal pulse.
In certain embodiments, the particle can be a solid having a size of less than 100 μm. The particle can be a solid having a size of less than 10 μm. The particle can be a solid having a size less than 1 μm. The particle can be a solid having a size of less than 100 nm. The particle can include polymer. The particle can include metal. The particle can include ceramic. The particle can include an organic crystal. The particle can be conductive. The particle can include semiconductor material.
In certain embodiments, the orifice can expose the liquid meniscus from which a particle is ejected. The orifice can have an opening larger than the particle diameter. The opening of the orifice can have a diameter of at least ten times of the diameter of the particle. The opening of the orifice can have a diameter of at least 100 times of the diameter of the particle. The opening of the orifice can have a diameter of at least 1000 times of the diameter of the particle.
In certain embodiments, the method can include annealing the particle. The method can include printing particles in arrays. The method can include printing particles in lines. The method can include printing a two-dimensional pattern. The method can include printing a vertical stack. The method can include printing a three-dimensional pattern.
In another aspect, a device of delivering a particle can include an orifice, a liquid including a particle to an exit orifice, a sensor capable of sensing a condition at a meniscus of the liquid at the orifice, and an electromagnetic supply configured to generate an electromagnetic field near the orifice.
In certain embodiments, the device can include an array of print nozzles. The device can print particles of different sizes. The device can print particles of different materials. The device can print a two-dimensional pattern comprising heterogeneous materials. The device can print a three-dimensional pattern comprising heterogeneous materials.
In another aspect, a device of delivering a particle can include a liquid containing one or more particles, an orifice through which a single particle is ejected from the liquid, and an electromagnetic supply configured to generate an electromagnetic field near the orifice.
In certain embodiments, applying a signal near the orifice can include applying the signal between the orifice and substrate, between the orifice and the surrounding environment, or between liquid and substrate (for example, using a needle in the top of capillary). In this context, near the orifice, can mean proximal to, adjacent to, or through the orifice. In other embodiments, at a meniscus of the liquid can be near the apex of the meniscus. In other embodiments, the particle can be delivered to a space, for example, a drug delivered to an airstream.
In certain embodiments, exactly one particle can be delivered at a time. Other aspects, embodiments, and features will be apparent from the following description, the drawings, and the claims.
Direct-write printing has enabled the rapid growth of the flexible and organic electronics industries; however, the spatial resolution of dominant printing technologies such as inkjet is insufficient to fabricate high-performance devices. As a result, additional processing steps are used to increase printing resolution while sacrificing device density, further miniaturization and cost-reduction is limited, and the opportunity to print functional materials from a growing library of colloidal inks is not fully realized. To resolve these problems, Deterministic Particle Ejection (DPE) can be used for high-speed digital printing. DPE can print virtually any solid object capable of being suspended in a liquid, spanning from nanometers to micrometers in size. These objects could be particles of polymers, metals, or ceramics; intricate chemically made crystals; or miniature chiplets containing lithographically fabricated devices. DPE can print within the 0.1-100 μm size range and make and characterize micron-scale conductive lines and arrayed organic light emitting crystals.
There is a growing need for innovative printing technologies that can leverage a rapidly expanding library of commercially available discrete micro- and nanoscale objects. These printable objects include well-established dispersions of ink and toner particles, new particle formulations such as semiconductor and metal nanoparticles, engineered molecules for organic crystals, biochemically specific beads, and even miniature electronic components (“chiplets”) released en masse from silicon wafers. See, for example, Stewart, M. E., Chemical Reviews, 108(2), pp. 494-521; Knuesel, R. J., et al., Proceedings of the National Academy of Sciences of the United States of America, 107(3), pp. 993-998, each of which is incorporated by reference in its entirety. Many of these objects (from complex molecules to chiplets) can now be bulk-manufactured in large quantities with excellent dimensional resolution at low cost. However, means of their placement are limited to approximate methods such as solution casting or droplet printing, which intrinsically result in stochastic organization or require the use of costly substrate pre-patterning methods to enhance registry and/or resolution to meet the needs of electronics manufacturing. For these reasons, practically unlimited possibilities exist for the design of new devices, surfaces, and bulk materials via the capability to organize discrete micro- and nanoscale objects in an efficient and scalable manner.
The potential impact of new printing technologies is demonstrated by the synergetic advancement of inkjet printing (
A performance summary of inkjet and other commercial printing technologies is provided in
However, for many flexible and organic devices, the critical dimensions are on the order of 1 μm for both organic and metallic circuitry. Therefore, to manufacture functional devices, inkjet is often combined with optical lithography and other patterning processes, enabling micron-scale resolution where necessary. This results in increased manufacturing complexity and cost, and often limits the areal density of features (due to the larger size of the sacrificial inkjet templates).
Electrohydrodynamic (EHD) can print liquid droplets, where an applied electromagnetic field, rather than a mechanical pressure pulse, is used to eject liquid droplets from a dispenser nozzle. See, for example, EP1948854B1; U.S. Pat. No. 5,838,349; U.S. Pat. No. 6,154,226; US20110187798; US20120105528; Park, J. U., et al., 2007, “High-resolution electrohydrodynamic jet printing,” Nature Materials, 6(10), pp. 782-789; Chen, C. H., et al., Applied Physics Letters, 88(15), page 3, each of which is incorporated by reference in its entirety.
Other technologies such as xerographic printing suffer from analogous limitations governed by the stochastic accumulation of patterned charge. And, at the opposite extreme of versatility, semiconductor and imprint lithography now enable sub-50 nm patterning, but the high cost of pattern generation and the limited material set does not make this technology deployable beyond the integrated circuit and MEMS industries.
In addition, current printing methods result in random distributions of solid materials on the substrate which limits feature geometry and performance. Therefore, “pain” in direct-write printing, where inkjet is the dominant technology, is that higher feature resolution and throughput are needed (and highly sought-after) for improving the performance of printed electronic devices comprising metallic, semiconducting, and organic solid constituents.
Deterministic ejection of individual particles from a random dispersion can be achieved with DPE. The particles can be in a single file inside a structure, such as a capillary tip. The particles can be ejected through a particle funneling or alignment method. The ejection can be due to physical constraint, like a capillary tip, or by an applied field, such as an electromagnetic field. DPE, a direct-write printing technology, operates by ejection of individual particles from a confined liquid meniscus. DPE enables micron- and sub-micron resolution printing of virtually any solid object, and can be capable of 10-100× smaller feature sizes (e.g., dots, lines) than industrial inkjet printing. Each printing can deliver exactly one particle onto the target substrate (
DPE operates by application of a voltage to a liquid held in a capillary tip. This causes ejection of a submerged particle near the liquid-air interface (
Several strategies can achieve control of particle ejection. The strategies can include local electric (or magnetic) field concentration near the apex of liquid meniscus ensuring singular particle ejection. This may be achieved by choosing the appropriate electrode configuration inside and outside the liquid, by application of AC or DC field. This can be a passive approach, where particle positioning is guaranteed given the proper ‘wait time’ between voltage pulses for printing. The field gradient may also be utilized to draw a particle to the proper location for ejection.
The strategies can include optical feedback, using machine-vision, to identify and track the location of particles inside the liquid. When a particle is identified as at the right location for ejection, a voltage pulse command can be issued. This can be a computationally intense approach that may limit print speed.
The strategies can include direct measurement of the electrical signature at the apex of the meniscus cone using a micro voltage probe. When the electromagnetic signature of a particle is sensed, a voltage pulse command can be issued to eject the particle in the vicinity of the probe.
The strategies can include physical entrapment or delivery of a particle to the apex of the liquid meniscus by a stationary or actuated mechanical probe, and/or by a micro- or nanofluidic channel or device. The method of entrapment or delivery may include applying a secondary electrical signal, such as a potential difference, within the liquid meniscus, where the potential difference can be time-varying.
A further strategy may use a physical or chemical process, such as a crystallization or polymerization reaction, to also form the particles within the meniscus, or in proximity to the meniscus or to the delivery means. The particles could be therefore synthesized on demand as printing events are executed and controlled, and the characteristics of the particles could be chosen as necessary.
DPE is distinct from existing EHD printing methods. For example, DPE can involve the ejection of individual solid particles rather than the ejection of a liquid droplet optionally containing a stochastic number of particles, and the particles can be significantly smaller than the diameter of the capillary tip thus enabling clog-free printing of particles. The latter point enables cost-effective micro-nozzle arrays for eventual high-throughput printheads. The particle can be wet, such that a liquid contacts a portion of the surface of the particle. The particle can include a liquid portion, which can have a volume substantially smaller than the solid particle volume.
Electronics and optics can be used for controlling, sensing, and imaging the process. For example, high-precision motorized actuators can be used for programmable positioning of the capillary tip, custom machining can be used to enable exchangeable dispensing tips, and high-speed sensitive electronic circuitry can be used to measure printing process parameters. Hardware components for DPE printing can include a liquid reservoir, dispensing orifice, electrode configuration, and a voltage source. Certain features of the hardware and methods can enable controllable sensing and ejection of individual particles from the liquid meniscus. Microfabricated nozzle arrays can be as printheads for DPE. In contrast, bulky capillary tube delivery systems have been used in multi-tip EHD liquid printers. A method of forming conductive lines can include heating chains of individually arranged particles. DPE can also be used to prepare OLED architectures featuring printed micro-crystals and/or stacked particulate elements.
Key process parameters and attributes (i.e., voltage pulse profile, particle ejection velocity and trajectory, power consumed per print, etc.) can be determined, and derive experimental scaling laws for DPE printing (e.g., speed and voltage versus size and particle conductivity) can also be determined.
Threshold voltage to eject a particle as a function of the particle-to-capillary diameter ratio and particle-to-meniscus liquid gap (i.e., distance ‘δ’ labeled in
An analytical model capturing the local ejection of a single particle can be derived. Arbitrary particle-liquid combinations and printer configurations desirable for specific applications can be developed. The particle ejection physics can be determined by local conditions between a single particle and nearby liquid interface, and therefore the model can be adapted to different tip designs and can be independent of the particle concentration away from the tip.
DPE printer can print discrete particulates from 0.1-100 μm, such as 1-μm diameter, from an orifice, such as a glass capillary tip. DPE printer can print discrete particulates from 1-100 μm; DPE printer can print discrete particulates from 0.1-1 μm. DPE can print not only one-dimensional structures, but also two-dimensional or three-dimensional structures. For example, DPE can print metallic particle (˜1 μm) lines and grid arrays, and organic crystals (0.5-50 μm). In addition, DPE can print 1-10 μm wide conductive lines on substrates, by printing individual conductive (metallic or carbon) particles (1-10 μm diameter) in line patterns, followed by an annealing step (i.e., heating) to fuse the particles into solid conductive traces (
During DPE printing, a condition near the apex of a meniscus of the liquid at the orifice can be sensed. The condition can be an electrical boundary condition and/or a liquid flow boundary condition by near the apex of a meniscus of the liquid at the orifice. The condition can be sensed by by detecting the location of the particle near the apex of a meniscus of the liquid at the orifice. The condition can be sensed by measuring electrical properties of the liquid.
During DPE printing, an electromagnetic signal can be applied. The electrical signal can be AC or DC; the electromagnetic signal can be either constant or slowly varying with respect to print dynamics. A profiled electrical signal pulse on the timescale of particle ejection dynamics can be applied and may be or superimposed on the applied electrical signal. A voltage pulse can be applied. An alternative is to apply s constant bias voltage, which can cause repeatable and regularly timed printing of individual particles.
For DPE printing, particles can be supplied in different ways. For example, particles can travel within the liquid towards the meniscus, where it is ejected when sufficiently close. In another approach, a discrete number of the particles can be supplied directly onto the meniscus, from which they are ejected once at the proper location.
The particles can be printed in arrays, lines, or vertical stacks. DPE can print an arbitrary two-dimensional pattern; DPE can print an arbitrary three-dimensional pattern. The arrays, lines or stacks can be annealed. The two-dimensional pattern or the three-dimensional pattern can be annealed. DPE can also deliver exactly one particle. A particle printed by DPE can be used for building an electronic or optical component or device, such as a component of a silicon device wafer.
Two-dimension printing of lines on flat substrates at this scale can be relevant to printing near-field communication (NFC) and radio-frequency identification (RFID) antennas with reduced area, thereby achieving a smaller form factor and reduced cost (i.e., more devices/substrate). Notable commercial technologies at the limited scales of inkjet include Kovio's anti-theft tags (
DPE can print organic micro-crystals into discretized arrays, which can function as pixels comprising an OLED display (
In addition, DPE can scale up. DPE can identify a liquid/particle delivery and sensing/control scheme that is conducive to highly multiplexed parallel printing. Inkjet print heads may have a 10's-100's of nozzles, enabled by MEMS fabrication, in order to improve printing throughput. Parallel array print nozzles can also be used for DPE printing to enable industry-throughput scale-up.
DPE has the ability to print any solid object from solution, which can expand the library of printable materials to include dimensionally precise dispersed micro- and nanoparticles that can be integrated as discrete device elements. For example, chemically made organic micro-crystals can be digitally printed to function as individual light-emitting pixels, enabling lower-cost and higher-performance OLED displays. For these and other applications, DPE printing can be a “drop-in” replacement for inkjet, enabling simplified and lower-cost manufacturing, as well as improved device functionality.
Further, the substrate area throughput of DPE can be invariant with feature size, contrasting the area-throughput tradeoff of inkjet and other direct-write methods. This is because the mechanical time constants of capillary force phenomena, which govern the speed of particle ejection for DPE printer, scale as the inverse square of the particle radius. Thus, the number of particles required to cover a fixed substrate area, as well as the printing frequency, both may increase as the inverse square of the particle size. For example, achieving complete uniform coverage of a substrate with 10 μm versus 100 nm diameter particles may take the same amount of time, and printing of particles with different sizes (e.g., from different tips in a microfabricated tip array) does not have to decrease the area throughput.
DPE has advantages over inkjet and competing printing technologies. For example, DPE can provide deterministic printing of 0.1-100 μm matter with digital precision, where a single particle can be printed using a voltage pulse with a specific duration and profile. DPE can have compatibility with a wide range of materials including polymers, organic crystals, metals, and ceramics—virtually anything that can be dispersed in a carrier liquid. DPE can be cost-effective because operational expenditures are comparable to inkjet (no clean-room), inks, and print speed can be invariant with area throughput. DPE can have versatility and broad applicability by enabling printing of arbitrary discrete or continuous patterns, and even stacking particulates in 3D.
With DPE, printing machines and/or modules can be developed for highly integrated manufacturing operations (e.g., in the electronics and display industries); desktop printers can be developed; and particulate material formulations, including solutions of “electronic” particles, can be used for printing.
High-value applications of DPE can exist for micron-scale printing, and conductive particulate materials commercially available and currently used in inkjet printing can be printed at finer length scales enabling higher performance of printed electronics. DPE can print 1-10 μm particles visualized optically during printing. The demand for finer printed solid features spans several different industries, and the generality of the DPE approach to print solids including conductors and organic semiconductors can be complementary to the growing availability of particulate materials. In this regard, the ability to decouple feature size, shape, and chemistry from the printing process via DPE can introduce a new approach to material design for printing. Also, the “drop-in” compatibility of DPE as a direct-write method analogous to inkjet would enable its implementation in existing manufacturing operations.
DPE can be disruptive to manufacturing of flexible and organic electronics manufacturing, and can have significant potential for both commercial and scientific impact. The capabilities of DPE to print functional particulate matter can enable many potential market opportunities including further miniaturization of flexible electronic elements (wires, spirals) at lower manufacturing cost, and manufacturing of high-performance OLEDs by direct printing of crystals.
DPE can also enable heterogeneous assembly of micrometer-scale processors, memory devices, photovoltaic cells, and RFID tags. Another future area could be custom fabrication of biosensors/assays using chemically specific polymer and metallic beads. Moreover, specific arrangements of individual nm-μm sized particles on substrates can trigger nanoscale electrical and optical transport phenomena that could be integrated with semiconductor fabrication.
DPE can be a practical solution to achieve deterministic ejection of individual particles from a random dispersion. DPE can also minimize complexity by using capillary tips much larger than the particle diameter. The flow of particles can be manipulated to determine which feedback control scheme can serve to first “deliver” then “eject” particles.
DPE can achieve high accuracy placement of particles on the substrate, robust to variations due to the influence of the surrounding electromagnetic field. The flight path of ejected particles can be influenced by substrate features and previously printed particles. This occurs because particles locally modify the electromagnetic field distribution near the substrate; and the thin liquid film initially encapsulating each particle at ejection contributes a net charge on the particle that may interact with the electromagnetic field during flight. Path-correction algorithms can be implemented in printing software to modify these effects. On the other hand, local field focusing by conductive particles aids in vertical construction, and assisted in building the vertical tower shown in
Therefore DPE can represent the ultimate patterning resolution of ink printing processes, and can enable further miniaturization of printed and flexible electronic circuit elements at low manufacturing costs. It can enable printing of significantly smaller and more dimensionally precise solid features than by direct inkjet deposition, which is particularly useful in fabrication of printed integrated circuits (IC) and radio-frequency identification (RFID) tags.
A single capillary tip apparatus for printing of microspheres dispersed in water is show in
The enabling physical principle of DPE involves the interaction between (1) the electromagnetic boundary condition at the liquid/air interface, and (2) the liquid flow boundary condition at the particle/liquid interface (
Because DPE depends on the local electrical and capillary force balance surrounding a single particle near the liquid interface, it is not necessary for the dispensing tip to be approximately the particle size, nor must the particles stack in single-file to enable printing. In
Rows of individual 75 μm diameter metallic (Ag-coated) particles with 1 mm spacing can be printed onto a copper substrate, three of which are depicted in
3D structures can be printed. For example, a vertical tower made from seven 75 μm diameter metallic (Ag-coated) particles, ejected individually and sequentially, can be constructed. Such a structure is not possible by inkjet, stamp imprint, or xerography, and shows the potential to build novel 3D device architectures from the same material, or possibly from different materials ejected from different tips in a programmed sequence.
In
DPE particle ejection can be controlled. Control strategies can comprise (1) a physical system configuration, and (2) a control loop algorithm. Exemplary schematics are shown in
“Passive” control strategies may also be implemented, in which a constant-bias electrical signal (AC or DC) is applied to the liquid, which induces predictable periodic ejection of individual particles. The control loop algorithm differs in this example because a “print event sensor”, such as a sensitive high-speed voltmeter or ammeter in series with the signal generator (
Physical entrapment control strategies may also be utilized, such as that depicted in
These control strategy examples demonstrate the versatility of DPE to adapt to a wide range of industry applications with varying performance/functional requirements.
Other embodiments are within the scope of the following claims.
This application is a continuation of U.S. application Ser. No. 14/562,631, filed on Dec. 5, 2014, now U.S. Pat. No. 9,937,522, which claims priority to U.S. Provisional Patent Application No. 61/912,202, filed Dec. 5, 2013, each of which is incorporated by reference in its entirety.
This invention was made with Government support under Grant No. CMMI 1150585 awarded by the National Science Foundation. The Government has certain rights in the invention.
Number | Date | Country | |
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61912202 | Dec 2013 | US |
Number | Date | Country | |
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Parent | 14562631 | Dec 2014 | US |
Child | 15949040 | US |