US20130314472A1

US20130314472A1 - Methods and Apparatus for Manufacturing Micro- and/or Nano-Scale Features

Info

Publication number: US20130314472A1
Application number: US13/959,849
Authority: US
Inventors: Salil Desai
Original assignee: North Carolina A&T State University
Current assignee: North Carolina A&T State University
Priority date: 2009-03-26
Filing date: 2013-08-06
Publication date: 2013-11-28
Also published as: US8573757B2; US20100245489A1

Abstract

The present invention provides devices for generating scalable patterned features on a substrate. In some embodiments, the device includes a means for forming and ejecting a succession of droplets, a charge tunnel, a quadrupole mechanism, a means for reducing the size of one or more of the droplets and one or more stream deflectors.

Description

RELATED APPLICATIONS

This application claims priority under 35 U.S.C. §120 to, and is a divisional application of, U.S. patent application Ser. No. 12/732,435, filed Mar. 26, 2010, which claims the benefit of priority under 35 U.S.C. §119(e) to U.S. Provisional Patent Application Ser. No. 61/163,484 filed Mar. 26, 2009, the disclosure of each of which is incorporated by reference herein in its entirety.

GOVERNMENT SUPPORT

Aspects of this research were supported by the NSF-CAREER Award No. 0846562. The U.S. Government has certain rights to this invention.

FIELD OF THE INVENTION

The present invention generally relates to the field of micro and nano-scale manufacturing.

BACKGROUND OF THE INVENTION

There exists a need for developing a micro/nano manufacturing process that has the ability to fabricate selective features at both the micro and nano scale. Also, such processes should be able to build multi-material features at scalable lengths (nano to micro scale ranges) extemporaneously.
The ability to fabricate structures from the micro to the nano-scale with varied geometry and high precision in a wide variety of materials is important in advancing the practical impact of micro and nano-technology.
Manufacturing of micro and nano-sized features has been achieved by using both contact and non-contact based technologies. However, when contact based technology is used, there is a possibility of contamination of the substrate from the tools. In addition, most known processes involve pre and post processing operations that are time consuming and may release hazardous material. Non-contact based processes, such as Pulse Laser Deposition (PLD) and Magnetron Sputtering, usually involve masking and may not be able to build selective features when needed.

SUMMARY OF THE INVENTION

Aspects of the present invention include the application of a controlled heat flux around a microdroplet periphery. A customized direct-write inkjet system equipped with a resistive heating ring fixture and a temperature proportional integral derivative (PID) controller may be employed. Additionally, a laser source with variable power modulation control may be employed. Controlled evaporation of mondispersed microdroplets to submicron and nanoscale dimensions can be achieved to provide the basis for generating particulate loaded (i.e., colloids, nanotubes, bio-media and the like) droplets for applications in micro and nanomanufacturing in the semiconductor, biotechnological and industrial sectors.
Thus, according to some embodiments of the present invention, provided herein are methods of generating scalable patterned features on a substrate. The methods comprise (1) ejecting a succession of droplets; (2) applying a force to the droplets in a manner such that the droplets travel along a designated path; (3) altering the properties of droplets in a manner so as to adjust the size of the droplets from micrometer to nanometer; and (4) depositing droplets on the substrate to generate patterned features on the substrate.
In some embodiments, the patterned features are three-dimensional. In another embodiment, the methods described herein further comprise repeating steps (1), (2) and/or (3) at least once. In one embodiment, the ejecting step comprises selectively applying a force to a stream of fluid such that the stream breaks into a succession of monodispersed droplets. In another embodiment, the ejecting step further comprises varying the properties of the force to control the characteristics of the droplets.
In one embodiment, the ejecting step comprises providing a piezoelectric nozzle, wherein a piezoelectric disk is located in the nozzle.
In one embodiment, the ejecting step provides droplets in the size of microns. In another embodiment, the applying step comprises charging the droplets. In a different embodiment, the altering step comprises applying a heating or laser source to the droplets.
According to another aspect of the present invention, an apparatus for generating scalable patterned features on a substrate is provided. The apparatus comprises (1) a means for droplet forming and ejecting a succession of droplets; (2) a means for altering the properties of droplets in a manner so as to adjust the size of the droplets from micrometer to nanometer; and (3) one or more stream deflectors to control the direction of the droplets to generate patterned features on the substrate. Yet, according to some embodiments of the present invention, an apparatus comprises (1) the continuous ink jet, (2) quadrupole assembly, and one or more stream deflectors.
Objects of the present invention will be appreciated by those of ordinary skill in the art from a reading of the Figures and the detailed description of the embodiments which follow, such description being merely illustrative of the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS

The following drawings form part of the present specification and are included to further demonstrate certain aspects of the present invention. Aspects of the invention may be better understood by reference to one or more of these drawings in combination with the detailed description of specific embodiments presented herein.

FIG. 1 is a schematic illustration of the apparatus of micro/nano manufacturing process.

FIG. 2 is a schematic showing of the geometry of a linear quadrupole with hyperbolic electrodes.

FIGS. 3 a-3 d show results of experiments comparing temperature and volume reduction for candidate fluids acetone and water.

FIGS. 4 a-4 b shows results of experiments comparing evaporation characteristics for candidate fluids acetone and water.

FIG. 5 shows results of experiments comparing evaporation characteristics for candidate fluids acetone and water based upon surface-to-volume ratio of microdroplets.

DETAILED DESCRIPTION

The foregoing and other aspects of the present invention will now be described in more detail with respect to the description and methodologies provided herein. It should be appreciated that the invention can be embodied in different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art.
The terminology used in the description of the invention herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. As used in the description of the embodiments of the invention and the appended claims, the singular forms “a”, “an” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. Also, as used herein, “and/or” refers to and encompasses any and all possible combinations of one or more of the associated listed items. Furthermore, the term “about,” as used herein when referring to a measurable value such as an amount of a compound, dose, time, temperature, and the like, is meant to encompass variations of 20%, 10%, 5%, 1%, 0.5%, or even 0.1% of the specified amount. It will be further understood that the terms “comprises” and/or “comprising,” when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof. Unless otherwise defined, all terms, including technical and scientific terms used in the description, have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs.
All patents, patent applications and publications referred to herein are incorporated by reference in their entirety. In case of a conflict in terminology, the present specification is controlling.
Provided herein, according to some embodiments of the invention, are methods of generating scalable patterned features on a substrate. The methods comprise (a) ejecting a succession of droplets; (b) applying a force to the droplets in a manner such that the droplets travel along a designated path; (c) altering the properties of droplets in a manner so as to adjust the size of the droplets and (d) depositing droplets on the substrate to generate patterned features on the substrate. In some embodiments, during the altering step (c), the size of the droplets is adjusted from micrometer to nanometer.
In some embodiments, the patterned features are three-dimensional. In another embodiment, the droplets comprise colloids of one or more material. Any applicable material may be used in the present invention. In some embodiments, the material is selected from the group consisting of metal, ceramics, fiber glass, semiconductors, polymers, bio-media (for example, drugs, cell lines, growth factors, and the like), a precursor solution for sol-gel process and a combination thereof. In some embodiments, the droplets are deposited via hydrophobic or hydrophilic patterns. In other embodiments, the droplets comprise polymer fluid.
In another embodiment, the methods further comprise repeating steps (a), (b) and/or (c) at least once. For example, a second or more tiers of droplets may be deposited to build multiple layers of nano or micro sized features. In some embodiments, the multiple application of depositing droplets may provide three-dimensional patterned features.
In one embodiment, the method further comprises the step of curing or gelation of the droplets after steps (a)-(c). In some embodiments, the step of curing may be carried out by adding chemical additives, exposing to ultraviolet radiation and/or electron beam or heat. In some embodiments, the method further comprises a curing or gelation process for polymer fluids. For example, an ultra violet curing process and/or gelation may be adopted for polymer fluids.
In some embodiments, the methods of the present invention further comprise heating the substrate to remove a solvent. For example, when the droplets are deposited via a solution and after the fluid droplets are deposited, the substrate may be soft-baked in-situ on a hot plate to remove volatile solvents and consolidate the deposited layer.
As used herein, “curing” is a process by which a polymer is toughened or hardened by cross-linking of polymer chains, brought about by chemical additives, ultraviolet radiation, electron beam and/or heat.

Stage 1-Ejecting Step (a)

In some embodiments, the ejecting step comprises selectively applying a force to a stream of fluid such that the stream breaks into a succession of droplets. In one embodiment, the ejecting step further comprises varying the properties of the force to control the characteristics of the droplets. In another embodiment, the ejecting step comprises providing a piezoelectric nozzle, wherein a piezoelectric disk may be located in the nozzle. Yet, in one embodiment, the force may be applied to the disk, and the force may be controlled to adjust the size, velocity and/or the ejecting rate of droplets.
In another embodiment, the ejecting step may be performed by a droplet forming mechanism that includes a customized inkjet setup. The customized inkjet set up may further include a continuous inkjet setup as known and described in, for example, U.S. Pat. No. 6,863,385 and U.S. Pat. No. 6,509,917, which are incorporated by reference in their entireties.
In some embodiments, the droplet forming mechanism may include a piezoelectric nozzle assembly where a stream of fluid is supplied at a high pressure (e.g. 5 to 50 psi). A piezoelectric disk may be located in the piezoelectric nozzle assembly and vibrates at high frequencies (e.g. from 1 KHz to 1 MHz) to generate acoustic waves. In some embodiments, the voltage and frequency of excitation of the piezoelectric disk may be varied. For example, increasing the voltage applied to the disk may result in a higher amplitude of vibration, and the fluid may break into larger droplet sizes. Another example is when a higher frequency of piezoelectric disk excitation is applied, the droplets may have a higher rate, and therefore, the temporal dimension is controlled.
In a different embodiment, the ejecting step further comprises controlling the orifice diameter of the nozzle to adjust the dimension of the droplets. In one embodiment, the ejecting step provides droplets in the size of microns. In some embodiments, the size of the nozzle may be varied from 100 microns to a few microns (for example, 1-10) based on the orifice diameter. In another embodiment, the spatial dimension of the droplets may be adjusted by varying the orifice diameter of the nozzle. In other embodiments, droplets may be generated at micrometer sizes during the ejecting step and then reduced to nanometer size in the later stage, for example step (c) the altering step.
In the present invention, the properties that affect droplet formation include, but are not limited to, viscosity and surface tension of the stream of fluids provided to the piezoelectric nozzle assembly. For example, fluids with higher viscosity may require higher voltages for exciting the piezoelectric disk; fluids with higher surface tension properties may require higher excitation of the piezoelectric disk to form consistent monodispersed microdroplets.

Stage 2-Applying (b) and Altering Steps (c):

In some embodiments, the applying step comprises charging the droplets. In another embodiment, the altering step comprises applying a heating or laser source to the droplets.
In some embodiments, a quadrupole mechanism may be used to guide the droplets in a straight line path. The exemplary quadrupole mechanism is described in Heston, Stephen F, Linear quadrupole focusing for high resolution Micro-droplet-based fabrication, MS theses, Mechanical engineering, University of Pittsburgh, 2002. The properties of the droplets may be altered during their path of flight. Several mechanisms including, but not limited to, resistive heating and laser-based curing, may be employed to change the physical, magnetic and electric properties of the droplets during path of flight. For example, if a heat source is used, the heat intensity may be controlled to reduce sizes of droplets from micrometer to nanometer by evaporating the solvent. If the heat source is not applied, the droplet size may remain within the micrometer range with reduction in size only due to evaporation effect. In other embodiments, the magnetic and electrical properties of droplets may be adjusted by changing the laser wavelengths, pulse width (i.e., duration) and/or source intensity. Other applicable parameters of droplets include, but are not limited to, fluid properties such as viscosity, density, surface tension, conductivity and/or percent solids (particle concentration) in solvent base colloids. In some embodiments, the heat or laser source may be attenuated or switched off to obtain micrometer to sub-micrometer features.
In some embodiments, a linear quadrupole system may be used to focus the charged microdroplets and manipulate their fluid properties. The associated stability conditions may be predicted from the governing conditions (See Rayleigh, On the Equilibrium of Liquid Conducting Masses Charged with Electricity, Phil. Mag., Vol. 5, 14, 184-186, at 1882.). A linear quadrupole comprises four electrodes with their axes at the corners of a square. By connecting the electrodes and applying AC voltage across adjacent rods, particles of a certain charge to mass ratio may be focused during their path of flight. The focusing quadrupole will allow an interval in which the properties of the droplet may be altered for additive fabrication.
For a droplet with radius α₀, surface tension y and charge Q, the spherical shape remains stable as long as the fissility X is less than one.
$X = \frac{Q^{2}}{64 π^{2} ɛ_{0} γ a_{0}^{3}} < 1$

To prevent the spontaneous disintegration of droplets due to electrostatic repulsion of the like charges residing on the surface of the droplet, the AC voltages on the quadrupole electrodes may be adjusted to stay below the Rayleigh limit. Another method of controlling the charge on droplets is to vary the charge potential being impressed by the charge tunnel when the droplets are initially charged when they exit from the nozzle orifice as described in stage 1.

Stage 3 Depositing Step (d)

In one embodiment, the droplets are charged and the depositing step comprises deflecting charged droplets to generate patterned features on the substrate. In some embodiments, the deflection of the charged droplet depends on the strength of the electric field through which it travels. The equations of motion for a charged droplet traveling through an electric field of intensity E are given as:
$m \frac{\partial υ_{x}}{\partial t} = QE - D \sin θ, m \frac{\partial υ_{z}}{\partial t} = m g - D \cos θ,$
If the undeflected droplet stream is aligned with the z coordinate which is parallel to the gravity vector, and the magnitude of the deflection is measured in the perpendicular x coordinate. Here vx and vz are the components of velocity in the x and z coordinates. In the above, g is the gravitational acceleration, and D is the aerodynamic drag force.
Fillmore [1977] predicted the deflection distance as:
$x_{d} = \frac{QE}{m υ_{0}^{2}} l_{dp} (z_{p} - \frac{l_{dp}}{2}),$
Where Q is charge, m is mass, v_ois initial stream speed, x_dis the deflection of a droplet, z_pis the distance from the deflection plate entry to the substrate, and l_dpis the length of the deflection plates. The prediction neglects the effects of gravity, drag, and/or mutual electrostatic interactions.
In other embodiments, the placement of droplets may be controlled by the positioning of the substrate. The crystal growth, material composition and morphology of the droplets may be controlled by the temperature gradients around the droplets and may be adjusted by the heating-cooling cycles.
According to some aspects of the present invention, the methods described herein may be used to selectively manufacture heterogeneous structures both in terms of geometry and material composition. In some embodiments, the methods described herein may further comprise substrate treatments. For example, sintering, curing, or other functionalizing, may be performed on the features.
As one of ordinary skill in the art may appreciate, the parameters described herein may vary greatly depending on the material/droplets. Such modifications are known to those skilled in the art.
Apparatus
Another aspect of the present invention provides an apparatus for generating scalable patterned features on a substrate. The apparatus comprises (1) a means for droplet forming and ejecting a succession of droplets; (2) a means for altering the properties of droplets in a manner so as to adjust the size of the droplets from micrometer to nanometer; and (3) one or more stream deflectors to control the direction of the droplets to generate patterned features on the substrate.
In one embodiment, the means for droplet forming may be selected from a continuous ink jet (CIJ), drop-on-demand (DOD) or thermal inkjet (TIJ) method. In another embodiment, the continuous ink jet comprises piezoelectric nozzle assembly. Yet, in a different embodiment, the piezoelectric nozzle assembly comprises a piezoelectric disk. In one embodiment, the means for altering the properties of droplets comprises a charge tunnel and a quadrupole assembly. In another embodiment, the means for altering the properties of droplets further comprise a heating, laser source, or a combination thereof.
The present invention will now be described in more detail with reference to the following examples. However, these examples are given for the purpose of illustration and are not to be construed as limiting the scope of the invention.

EXAMPLES

Example 1

Stage 1—Customized Continuous Inkjet-Based Microdroplet Generation

As shown in FIG. 1, a customized continuous inkjet (CIJ) setup may be utilized to generate microdroplets. Fluid is supplied at a high pressure (5 to 50 psi) to a piezoelectric (PZT) nozzle assembly to generate a fluid jet. A piezoelectric disk located within the PZT nozzle assembly vibrates at high frequencies (variable from 1 kHz to 1 MHz) generating acoustic waves. A combination of Rayleigh instabilities and forced acoustic waves create standing nodes on the surface of the ejected jet, causing it to break up into fine droplets. (See Rayleigh, On the Instability of Jets, Proceedings of the London Mathematical Society, 10 (4), 4-13 (1878), Depending on the fluid properties, piezoelectric disk excitation parameters and nozzle geometry, droplet diameters can vary from 1 to 2.5 times the nozzle orifice diameter. The inkjet process described above involves a complex interaction of three domains: electrostatic, structural, and fluid. More importantly, the drop generation mechanism occurs at particular spatial and temporal dimensions. For example, at 1 MHz frequency each drop is formed at around 1 microsecond and can have dimensions to the order of 1-5 μm. Further, each droplet is charged before break-off from the jet in a charge tunnel. These charged droplets are fed to a quadrupole mechanism.

Stage 2—Quadrupole Mechanism

As shown in FIG. 1, the quadrupole mechanism acts as a guide way to constrain the path of the droplet motion. It consists of four electrodes arranged with their axes at right angles to each other. By connecting the electrodes, as shown in FIG. 2 and applying an AC voltage across adjacent electrodes, charged fluid microdroplets of a certain charge-to-mass ratio are focused as they travel through the electrode length. The constrained motion of the microdroplets allows for a sufficient time interval in which the properties of the droplets can be altered during their path of flight. The droplet may be adjusted from a microdroplet (1 to 5 μm) to a nanodroplet (80 to 200 nm).

Stage 3—Deflector Plate Mechanism

As shown in FIG. 1, on exit from the quadrupole mechanism the droplet is deflected onto the substrate using a deflector plate mechanism. This mechanism consists of two high voltage plates which deflect the droplet based on the potential equilibrium. These deflector plates can be charged at variable voltages depending on the droplet pattern to be generated on the substrates. The principle of electric field based deflection of charged particles is described in U.S. Pat. No. 6,509,917, which is incorporated by reference in its entirety.

Example 2

Comparison of Different Fluid Types

Nanopure distilled water and 99.998% filtered acetone were the two fluids used as candidate fluids with specific heats of 75.33 and 126.66 (J/mol·K) respectively. This comparison enabled the assessment of the significance of specific heat of fluids (e.g., low vs. high) on droplet evaporation. The other factor investigated was the impact of nozzle diameter (50 μm vs. 30 μm), which can determine the effect of surface to volume ratio on droplet evaporation. Both fluids were jetted using a customized direct-writing inkjet system (MicroFab Technologies Inc., Plano, Tex.). The system included a JetDrive III waveform generator and amplifier, a pneumatics console, optics system and a MJ-AT-01-30 piezoelectric (PZT) microvalve with an interchangeable orifice (i.e., nozzle) diameter of 30 and 50 μm, Monodispersed microdroplets were generated and subjected to convective heat flux using a resistive heating ring fixture (Mid Atlantic Heater and Control Inc., S.C.) equipped with a controller.
The experimental conditions included jetting both fluids (water and acetone) from two different nozzle diameters (30 μm and 50 μm). The temperature of the resistive heating ring fixture was adjusted to evaporate the droplets from each experimental condition as shown in Table 1 below. The initial droplet condition (i.e., without the heating ring) for each experiment was recorded at room temperature (25° C.). The reductions in droplet for temperatures from 200° C. to 400° C. in increments of 50° C. were recorded.

TABLE 1

Experimental Conditions

Condition	Nozzle		Ring temperature
No.	Diameter	Fluid type	range (° C.)

1	50 microns	Acetone	200-400
2	30 microns	Acetone	200-400
3	50 microns	Distilled water	200-400
4	30 microns	Distilled water	200-400

A charge coupled device (CCD) camera with a microscopic zoom lens was employed to capture microdroplet formation and their trajectories during their path of flight as they were jetted from the nozzle orifice. A light emitting diode (LED) source was synchronized with the piezoelectric actuator to provide illumination for observing the droplets. Once a stable monodispersed droplet condition was achieved, the heating ring fixture was positioned to envelope the droplets for evaporation. Image acquisition software (ImageJ) from the National Institute of Health (NIH) was used to analyze the droplet evaporation. A copper wire with predefined dimension was introduced in the frame during image capture to calibrate the microdroplet dimensions. Droplet surface area and volume were calculated for each experimental condition to observe reduction in its size with variations in the temperature.

Percentage Reduction in Droplet Volume

For each of the four experimental conditions, a proportional relationship between percentage volume reduction and incremental temperature (shown in FIG. 3) was observed.
A 50 μm nozzle size yielded higher percentage reductions in volume over the 30 μm nozzle size for both the fluid types.

Effect of Fluid Type

Based on the fluid type, acetone was observed to evaporate at a higher rate with an increase in the temperature as shown in FIG. 4.

Effect of Surface Area to Volume Ratio

The effect of surface to volume ratio on droplet evaporation was observed as shown in FIG. 5. Fluids when jetted through smaller nozzles size resulted in higher surface to volume ratio and vice versa. However, as the temperature increased, a 50 μm acetone droplet evaporated at much faster rates than the 30 μm size droplets resulting in higher surface-to-volume ratio at higher temperatures.
In conclusion, the droplet evaporation characteristics for water and acetone were studied to understand the microdroplet size reduction phenomenon. A proportional reduction in the volume of the microdroplets of water and acetone was observed with an increase in heat flux. Acetone microdroplets exhibited more percentage volume reduction compared to that of water under the same conditions. Also for both fluids, droplets jetted with the 50 μm diameter nozzle were observed to have higher percentage volume reductions than those jetted with the 30 micron nozzle. Droplets with higher surface area to volume ratio evaporated at a faster rate.

REFERENCES

1. Desai et al., Coupled field analysis of Piezoelectric Bimorph Disk in a Direct Write Fabrication Process, COMPOSITE B J. 38:824 (2007).
2. Desai and Lovell, Statistical Optimization of Process Variables in a Continuous Inkjet Process for Direct Write Fabrication-A Case Study, INTL. J. OF INDUS. ENG. 15(1):104 (2008).
3. Chappell et al., Computational Modeling of a Drop-on-Demand (DOD) Inkjet System for Understanding Microdroplet Behavior, ASME EARLY CAREER TECH. J. 6(1) (2007).
4. Desai and Lovell, Computational Fluid Dynamic Analysis of a Direct Write Manufacturing Process, INTL. J. OF NANOMANUFACTURING 4(3):171 (2009).
5. Lord Rayleigh, On the Equilibrium of Liquid Conducting Masses Charged with Electricity, PHIL. MAG. 5:14:184 (1882).
6. Doyle and Vonnegut, Behavior of Evaporating Electrically Charged Droplets, J. COLLOID SCI. 19:136143 (1964).
7. Abbas and Latham, The Instability of Evaporating Charged Drops, J. FLUID MECH. 30:663670 (1967).
8. Schweizer and Hanson, Stability Limit of Charged Drops, J. COLLOID INTERFACE SCI. 35:417423 (1971).
9. Taflin et al., Electrified Droplet Fission and the Rayleigh Limit, LANGMUIR, 5:376384 (1989).
10. Richardson et al., On the Stability Limit of Charged Droplets, PROC. R. SOC. LOND., A., 422:319328 (1989).
11. Gomez and Tang, Charge and Fission of Droplets in Electrostatic Sprays, PHYS. FLUIDS 6:404414 (1994).
12. Choi and Kim, Experimental evaluation of electrodynamically focused nanoparticle behavior in the quadrupole electric field, Annual Conference of the American Association for Aerosol Research (2007),
13. Orme et al., Electrostatic charging and deflection of non conventional droplet streams formed from capillary stream breakup, PHYS. FLUIDS 12(9) (September 2000).
14. Schneider et al., Stability of an electrified liquid jet, J. APPL. PHYS. 38(6):2599 (1967).
15. Eiroma et al., UV curing of electronic printing, RADTECH Rep. (September/October 2007).
16. Harrop, Developments in printed and thin film electronics, PRINTED ELECTRONICS, EUROPE 2007, Cambridge, UK (2007).
17. Kiang and Balcerski, UV Curing Technology: Issues for Inkjet Formulations, Sartomer Company, Inc. Exton, Pa. USA.
18. Sweet, High frequency recording with electrostatically deflected ink jets, REV. SCI. INSTRUM. 36:131 (1965).
19. Kamphoefner, Ink jet printing, IEEE TRANS. ELECTRON DEVICES 19:584 (1972).
20. Fillmore et al., Drop charging and deflection in an electrostatic ink jet printer, IBM J. RES. DEV. 1:37 (1977).
21. Desai et al., Understanding Microdroplet Evaporation towards Scalable Micro/Nano Fabrication, PROC. INDUS. ENG, RES. CONF., MEXICO (2010).
The foregoing is illustrative of the present invention and is not to be construed as limiting thereof. Although a few exemplary embodiments of this invention have been described, those skilled in the art will readily appreciate that many modifications are possible in the exemplary embodiments without materially departing from the novel teachings and advantages of this invention. Accordingly, all such modifications are intended to be included within the scope of this invention as defined in the claims. The invention is defined by the following claims, with equivalents of the claims to be included therein.

Claims

1. An apparatus comprising:

(1) a means for forming and ejecting a succession of droplets;

(2) a charge tunnel;

(3) a quadrupole mechanism;

(4) a means for reducing the size of one or more of the droplets; and

(5) one or more stream deflectors.

2. The apparatus of claim 1, wherein the means for forming and ejecting a succession of droplets is configured to selectively adjust the size, velocity and/or ejection rate of the droplets.

3. The apparatus of claim 1, wherein the means for forming and ejecting a succession of droplets comprises a continuous ink jet apparatus, a drop-on-demand inkjet apparatus or a thermal inkjet apparatus.

4. The apparatus of claim 1, wherein the means of droplet forming and ejecting a succession of droplets comprises a piezoelectric nozzle.

5. The apparatus of claim 4, wherein the piezoelectric nozzle comprises a piezoelectric disk.

6. The apparatus of claim 5, wherein the means for forming and ejecting a succession of droplets is configured to selectively vary a voltage of excitation of the piezoelectric disk.

7. The apparatus of claim 5, wherein the means for forming and ejecting a succession of droplets is configured to selectively vary a frequency of excitation of the piezoelectric disk.

8. The apparatus of claim 5, wherein the means for forming and ejecting a succession of droplets is configured to selectively vary an orifice diameter of the piezoelectric disk.

9. The apparatus of claim 1, wherein the charge tunnel is configured to apply a variable charge potential to the droplets.

10. The apparatus of claim 1, wherein the quadrupole mechanism is configured to guide the droplets in a straight line path.

11. The apparatus of claim 1, wherein the quadrupole assembly comprises four electrodes wherein the electrodes are arranged with their axes at right angles to each other.

12. The apparatus of claim 1, wherein the means for reducing the size of one or more of the droplets is configured to reduce the size of one or more of the droplets by at least about 20%.

13. The apparatus of claim 1, wherein the means for reducing the size of one or more of the droplets is configured to reduce the size of one or more of the droplets from 1 to 5 μm to 80 to 200 nm.

14. The apparatus of claim 1, wherein the means for reducing the size of one or more of the droplets comprises a heat source.

15. The apparatus of claim 1, wherein the means for reducing the size of one or more of the droplets comprises a laser source.

16. The apparatus of claim 1, wherein the one or more stream deflectors comprise two plates, each of which is charged.

17. An apparatus, comprising:

(1) a means for forming and ejecting a succession of droplets, comprising a piezoelectric nozzle;

(2) a charge tunnel;

(3) a quadrupole mechanism;

(4) a means for reducing the size of one or more of the droplets, comprising a heat source, a laser source or a combination thereof; and

(5) two or more charged deflector plates.

18. The apparatus of claim 17, wherein the piezoelectric nozzle comprises a piezoelectric disk.

19. The apparatus of claim 17, wherein the means for forming and ejecting a succession of droplets is configured to selectively vary:

(a) a voltage of excitation of the piezoelectric disk;

(b) a frequency of excitation of the piezoelectric disk; and/or

(c) an orifice diameter of the piezoelectric disk.

20. The apparatus of claim 19, wherein the means for reducing the size of one or more of the droplets is configured to reduce the size of one or more of the droplets by at least about 20%.