Nanoscale high resolution electrodynamic printing using heterogenous mechanisms

Abstract

A method of printing a polarizable particle, the method including: applying an electric field for a hold time to a tip of a printer nozzle comprising an ink, wherein the electric field comprises an electric field strength and an electric field gradient, and wherein the ink comprises a polarizable particle dispersed in an apolar solvent; and applying the polarizable particle to a substrate. A system for printing a polarizable particle, the system including: an ink comprising a polarizable particle dispersed in an apolar solvent; a printer, the printer including: a print head; a printer nozzle comprising a print tip, the printer nozzle being coupled to the print head and being sized and shaped to contain the ink; an electric field source; a platform sized and shaped to mount a substrate; and a controller for implementing any of the methods described herein.

Description

NANOSCALE HIGH RESOLUTION ELECTRODYNAMIC PRINTING USING HETEROGENOUS MECHANISMSCROSS-REFERENCE TO RELATED APPLICATION

[0001] This application claims the benefit of U. S. Application No, 63 / 736,527, filed on December 19, 2024, and U. S. Application No. 63 / 752,005. filed on January 31.2025, the disclosures of which are hereby incorporated by reference in their entireties.STATEMENT OF GOVERNMENT LICENSE RIGHTS

[0002] This invention was made with government support under Grant No. DMR-2019444, awarded by the National Science Foundation, and under Grant No. FA8650-20-2-5506, awarded by the U. S. Army Research Laboratory. The government has certain rights in the invention.BACKGROUND

[0003] Since quantum computers were first proposed as the solution to problems considered too complex for classical transistors, the field of quantum information science has seen significant growth in developments of both theory and application. Yet, in the noisy intermediate-scale quantum (NISQ) era. the realization of quantum bits (qubits) - the fundamental building blocks for quantum operations - remains a challenge. Among the diverse qubit candidates, photons are an advantageous option due to their high mobility and resistance to decoherence at room-temperature. Often termed "flying qubits", photons are even considered as a requirement for establishing high-fidelity networks for quantum entanglement, teleportation, and quantum key distribution.

[0004] To generate single-photons for quantum processing and networking applications, colloidal solution-processable quantum dots (QDs) are leading material candidates for large-scale nanophotonic systems. These semiconductor crystals, typically 2 to 10 nm in diameter, exhibit quantum confinement, restricting movement of charge carriers (electrons and holes) to a small volume. When optically or electrically excited, QDs generate a single electron-hole pair (exciton), which, upon relaxation, releases a single photon at a wavelength that is a function of the quantum confinement within the QD. By precisely controlling the timing and intensity of the excitation, QDs can be effective on-demand single-photon sources, essential for photonic quantum technologies.

[0005] Despite progress in alternative qubit technologies, such as trapped ion, superconducting, neutral atom, and silicon spin qubits, scaling photonic platforms remains challenging. Many of these structures require the heterointegration of compound semiconductor quantum emitters with photonic materials such as dielectric oxides or nitrides. The conventional epitaxial and lithographic approaches to depositing and patterning of compound semiconductors for quantum emitting structures involves relatively slow, energy- and cost-intensive UHV techniques coupled with expensive, high waste, subtractive patterning processes such as electron beam lithography and etching. While these nanoscale fabrication approaches can produce complex, idealized structures for laboratory demonstrations and studies, they would be very cost and resource intensive for the production of quantum-emitter based devices that typically have sparsely distributed emitters at the scales needed for the broad use of quantum-based systems such as computing. Furthermore, the incompatibility of conventional epitaxial approaches for compound semiconductors with photonic elements in a combined system, such as the inability to epitaxially grow quantum scale semiconductors with low defect densities directly on materials such as silicon nitride, requires the creation of the quantum emitters as discrete devices that are then placed onto often fragile photonic structures via difficult manipulations.

[0006] An attractive pathway for direct heterointegration of QD emitters with photonic or electronic structures, such as optical cavities or structures for electrical stimulation, would be non-contact, solution-based printing of small volumes of colloidal quantum dots such as by inkjet printing, which has been demonstrated. However, proceeding to the length and printed droplet volume scales needed for single QD printing is challenging, due to the increasing surface energy barriers that dominate when forming droplets near 10 microns in diameter and picoliter volumes. For available consumer droplet formation systems and industrial inkjet, the droplet volumes have been limited to these picoliter and ca. 10-micron scales for the last two decades. Despite this, with the impressive development of colloidal quantum dots, techniques such as spin-coating and drop-casting have been used for fundamental studies and proofs-of-concept One of the significant challenges in these cases, is the resulting stochastic spatial positioning of colloidal QDs ensembles, which are typically overcome through the painstaking isolation of chance placements of QDs in advantageous positions. For functional photonic quantum platforms, spectrally identical single-photon emitters must couple to optical cavities, enabling photoninteraction and direction through waveguides without interference from misplaced QDs. While template lift-off methods have shown some success in patterning single QDs onto completely planar substrates, no scalable deterministic process for coupling single QDs to complex nanophotonic architectures has been demonstrated thus far.

[0007] To date, by leveraging dielectrophoretic (DEP) forces, EHD printing has been shown to form and eject, sub-attoliter liquid droplets carrying suspended nanoscale solids by polarizing the particles themselves in nonuniform electric fields. This mechanism generates directional forces on the particles, driving solid-laden fluid along electric field gradients to allow the formation and acceleration of high surface energy small droplets towards a target substrate. Conventionally, the droplet diameters considered have been significantly larger than the suspended particles and the ink fluid has largely been treated as a continuum fluid of liquid and solid constituents. In these cases, reduction of printhead nozzle diameters was leveraged to reduce droplet volumes and nanoparticle counts.

[0008] Inkjet nozzles formed through microelectromechanical (MEMS) processes have had some success when operated with nozzle dimensions on the order of 10 pm or larger Physical nozzles at smaller scales, however, have been difficult to fabricate with the precise dimensional control required to ensure uniform printing in a mode where the droplet size directly derives from the physical size and uniformity (in terms of dimensions and wetting properties) of the nozzle orifice, and at submicron dimensions which would allow conventional printing to access nanoscale dimensions reproducibly. Also, at single and sub-micron nozzle sizes, fluid dynamic bottlenecks arise in terms of the viscous shear forces and surface tensions need to form droplets from such a nozzle. Evidence of these challenges can be seen in the lower limits for droplet sizes for commercial inkjet systems being limited to >10 microns in diameter and greater than picoliter volumes, as represented by the circular data points in the droplet diameter versus time plot in Figure 1 A.

[0009] Semiconductor nanocrystals, known for their size-dependent properties, are desirable for next-generation technologies, including optical quantum devices, nanotransistors, sensors, light-emitting diodes, single-photon sources, and CMOS circuits.SUMMARY

[0010] This summary is provided to introduce a selection of concepts m a simplified form that are further described below in the Detailed Description. This summaryis not intended to identify key features of the claimed subject matter, nor is it intended to be used as an aid in determining the scope of the claimed subject matter.

[0011] In an aspect, the present disclosure provides a method of printing a polarizable particle, the method including: applying an electric field for ahold time to a tip of a printer nozzle comprising an ink, wherein the electric field comprises an electric field strength and an electric field gradient, and wherein the ink comprises a polarizable particle dispersed in an apolar solvent; and applying the polarizable particle to a substrate.

[0012] In some embodiments, the polarizable particle is selected from the group consisting of a quantum dot, a nanocrystal, a metallic particle, and combination thereof.

[0013] In some embodiments, the quantum dot comprises a core and a shell encapsulating the core. In some embodiments, a diameter of the core is about 3.5 nm. In some embodiments, the shell comprises between about 10 monolayers and about 100 monolayers.

[0014] In some embodiments, the core comprises a group IV composition, a group III-V composition, a group II- VI composition, a semi-conducting perovskite, and a chalcogenide semiconductor; and the shell comprises CdS, CsPbB, BaTiO3, or lead zirconium titanates.

[0015] In some embodiments, the shell comprises a dielectric material.

[0016] In some embodiments, the shell comprises a semiconductor material.

[0017] In some embodiments, a band gap of a material comprising the shell is larger than a bandgap of a material comprising the core.

[0018] In some embodiments, the shell electronically passivates or optically passivates active defects at a core-shell interface.

[0019] In some embodiments, the group IV composition comprises Si, Ge. or C / nanodiamond. In some embodiments, the group III-V composition comprises GaAs, InP, or antimonides. In some embodiments, the group II- VI composition comprises CdS, CdSe, CdTe. ZnSe, ZnS. ZnTe, or CdTe. in some embodiments, the core comprises CdSe. In some embodiments, the shell comprises CdS.

[0020] In some embodiments, the quantum dot has a diameter of between about 10 nm and about 100 nm.

[0021] In some embodiments, the polarizable particle has a total average radius of between about 20 nm and about 1 pm.

[0022] In some embodiments, the quantum dot further comprises an atomic dopant selected from the group consisting of B. P, As, N. Si, and combinations thereof.

[0023] In some embodiments, the polarizable particle has size tunable polarizability and / or polarization. In some embodiments, the polarizable particle has a particle dielectric constant of greater than 2.

[0024] In some embodiments, the solvent has a solvent dielectric constant that is lower than the particle dielectric constant. In some embodiments, the solvent dielectric constant is less than 10.

[0025] In some embodiments, the apolar solvent comprises a mixture of two or more apolar solvents. In some embodiments, the apolar solvent is a hydrocarbon solvent. In some embodiments, the hydrocarbon solvent is selected from the group consisting of octane, hexadecane, and mixtures thereof.

[0026] In some embodiments, the printer nozzle is coupled to a printhead. In some embodiments, applying the polarizable particle to a substrate comprises dielectrophoretically overcoming surface tension and / or interfacial energy of the apolar solvent to print the polarizable particle.

[0027] In some embodiments, the printhead is operatively coupled to a controller configured to control a first electric field applied to the polarizable particle and a second electric field applied to the substrate. In some embodiments, the controller comprises a tailored waveform generator.

[0028] In some embodiments, the polarizable particle further comprises highly polarizable ligand groups. In some embodiments, the ligand group reverses a solubility or dispersibility of the particle from a polar particle surface to within an apolar solvent. In some embodiments, the ligand group reverses a solubility or dispersibility" of the particle from being a high surface energy particle to being a low surface energy particle through ligand coverage of a surface of the particle.

[0029] In some embodiments, applying the electric field comprises applying a voltage between a first electrode and a second electrode, wherein the voltage is between about 500 V to about 900 V, wherein the hold time is between about 0.5 seconds and about 2 seconds, wherein a fixed bias is about 1000 V, and wherein a frequency is about 1 kHz. In some embodiments, the electric field strength is between about 105V / m and about 106V / m.

[0030] In some embodiments, the polarizable particle emits single photons. In some embodiments, the polarizable particle is optically excitable and / or electrically excitable.

[0031] In some embodiments, the method further includes applying a light source to excite the polarizable particle in the ink before applying the polarizable particle to the substrate.

[0032] In some embodiments, the method further includes heating the polarizable particle in the ink. In some embodiments, heating is by illumination of the polarizable particle.

[0033] In some embodiments, applying the polarizable particle to the substrate occurs without substantially deforming a bulk meniscus at the tip of the printer nozzle.

[0034] In some embodiments, applying the polarizable particle to the substrate occurs without reversing a curvature of a bulk meniscus at the tip of the printer nozzle relative to an air or gas interface under the meniscus.

[0035] In an aspect, the present disclosure provides a layer of a device fabricated by any of the methods described herein. In some embodiments, the device is an optical quantum device, a nano-transistor, a sensor, a light-emitting diode, a single-photon source, or a CMOS circuit.

[0036] In an aspect, the present disclosure provides a system for printing a polarizable particle, the system including: an ink including a polarizable particle dispersed in an apolar solvent; and a printer, the printer including: a print head; a printer nozzle comprising a print tip, the printer nozzle being coupled to the print head and being sized and shaped to contain the ink; an electric field source; a platform sized and shaped to mount a substrate; and a controller operatively coupled to the printer, the controller including at least one processor and a computer-readable medium having computerexecutable instructions stored thereon that, m response to execution by the at least one processor, cause the controller to perform operations including: applying an electric field for a hold time to the tip, thereby applying the polarizable particle to the substrate.DESCRIPTION OF THE DRAWINGS

[0037] The foregoing aspects and many of the attendant advantages of this disclosure will become more readily appreciated as the same become better understood byreference to the following detailed description, when taken in conjunction with the accompanying drawings, wherein:

[0038] FIGURE 1A: Scatter plotted reports of droplet sizes using traditional inkjet and EHD printing over the past 35 years.

[0039] FIGURE IB: Schematic diagram of the EHD printing setup used in this work, according to embodiments of the present disclosure. Top inset: fluorescence (FL) microscopy of EHD printhead. Scale bar: 10 pm. Bottom inset: Scanning electron microscopy (SEM) of single EHD-printed QD. Scale bar: 100 nm.

[0040] FIGURE 1C: Graphic representation of CdSe QD cores (open circles) with tunable range of hexagonal diamond CdS shell diameters.

[0041] FIGURE ID: Bisected illustrations of EHD printheads dielectrophoretically overcoming surface tension to print droplets of particle ensembles, according to embodiments of the present disclosure.

[0042] FIGURE IE: Bisected illustrations of EHD printheads dielectrophoretically overcoming mterfacial forces to print singular particles, according to embodiments of the present disclosure.

[0043] FIGURE IF: Schematic diagram of an EHD printing setup with a ring electrode.

[0044] FIGURE 2: Pendant drop test, according to embodiments of the present disclosure. Shadow image of octane:hexadecane pendant drop shape analysis. Pendant drop outline (blue) indicates shape profile used for surface tension measurement.

[0045] FIGURE 3A: Characterization of ink and energy modeling, according to embodiments of the present disclosure. Shadow images of sessile drop shape analysis of (i) water and (ii) octane: hexadecane mixture on CdSe / CdS QD thin film. Sessile droplet outlines (dashed lines) indicate shape profile used for contact angle and surface free energy measurements.

[0046] FIGURE 3B: Characterization of ink and energy modeling, according to embodiments of the present disclosure. Electrical COMSOL simulation of spherical particle at the (i) interior solution interface, (ii) halfway through solution interface, and the (lii) exterior of the solution interface. The left side of each plot show’s the electric field (£) and the right side shows the gradient of the field magnitude squared (V|E2). The simulation is symmetrical around the center axis.

[0047] FIGURE 3C: Characterization of ink and energy modeling, according to embodiments of the present disclosure. Plot of surface tension force (dashed), net interfacial forces (solid) and dielectrophoretic forces (dotted) acting on single particles of various radii. The shaded background indicates the size regime of the

[0048] FIGURE 4: Clausius-Mossotti factor for core / shell QD, according to embodiments of the present disclosure. Plotted approximation of Clausius-Mossotti factor of a core / shell QD based on the volumetric ratio between the CdSe core and CdS shell.

[0049] FIGURE 5A: Printhead analysis and simulation, according to embodiments of the present disclosure. Brightfield microscopy images of EHD printhead.

[0050] FIGURE 5B: Printhead analysis and simulation, according to embodiments of the present disclosure. Brightfield microscopy images of interior electrode tip.

[0051] FIGURE 5C: Printhead analysis and simulation, according to embodiments of the present disclosure. Brightfield microscopy images of printhead tip.

[0052] FIGURE 5D: Printhead analysis and simulation, according to embodiments of the present disclosure. Brightfield microscopy images of Finite element analysis simulating electric field in / around the printhead, substrate, and ground plane.

[0053] FIGURE 6A: Experimental results of EHD printing colossal QDs, according to embodiments of the present disclosure. Effect of drive amplitude on FL detected print yield as a heatmap of number of prints detected out of a 10 x 10 array of print attempt sites, per parameter configuration.

[0054] FIGURE 6B: Experimental results of EHD printing colossal QDs, according to embodiments of the present disclosure. Histogram plot of QDs counted per print site for a 10 x 10 array of attempt sites as detected by SEM and FL (900 V and 2 s parameter configuration). Estimated QDs indicate QDs not detected via SEM but were positively-indicated by the FL microscopy. The distribution of estimated QDs is based on the number of QDs per print yields, per bin. Inset: SEM image of 2 x 2 array of EHD-printed single QDs on ITO-glass, White circles indicate single QD positions. Inset: SEM image of single QD. Central Inset: SEM image of single QD.

[0055] FIGURE: 6C: Experimental results of EHD printing colossal QDs, according to embodiments of the present disclosure. Observation camera image stills of EHD printhead printing (i) thin-shelled QDs and (li) colossal-shelled QDs.

[0056] FIGURE 6D: Experimental results of EHD printing colossal QDs, according to embodiments of the present disclosure. Plot of single QD emission spectrum (solid) and Lorentzian fit (dashed).

[0057] FIGURE 6E: Experimental results of EHD printing colossal QDs, according to embodiments of the present disclosure. Second-order time correlation plot and fit of EHD-printed QD showing single-photon emission, measured at room temperature, with 10 pW excitation.

[0058] FIGURE 6F: Experimental results of EHD printing colossal QDs, according to embodiments of the present disclosure. Histogram plot of g(2)(0) measurements on EHD-printed single QDs (n=11).

[0059] FIGURE 7 A: MATLAB machine vision for print detection for 900V Amplitude, according to embodiments of the present disclosure. Fluorescent microscopy images of EHD prints in an array of amplitudes and hold times with 5 pm print spacing. Boxes indicate discrete prints detected by MATLAB image processing toolbox.

[0060] FIGURE 7B: MATLAB machine vision for print detection for 800V Amplitude, according to embodiments of the present disclosure. Fluorescent microscopy images of EHD prints in an array of amplitudes and hold times with 5 pm print spacing. Boxes indicate discrete prints detected by MATLAB image processing toolbox.

[0061] FIGURE 7C: MATLAB machine vision for print detection for 700V Amplitude, according to embodiments of the present disclosure. Fluorescent microscopy images of EHD prints in an array of amplitudes and hold times with 5 pm print spacing. Boxes indicate discrete prints detected by MATLAB image processing toolbox.

[0062] FIGURE 7E: MATLAB machine vision for print detection for 800V Amplitude, according to embodiments of the present disclosure. Fluorescent microscopy images of EHD prints in an array of amplitudes and hold times with 5 pm print spacing. Boxes indicate discrete prints detected by MATLAB image processing toolbox.

[0063] FIGURE 7E: MATLAB machine vision for print detection for 500V Amplitude, according to embodiments of the present disclosure. Fluorescent microscopy images of EHD prints in an array of amplitudes and hold times with 5 pm print spacing. Boxes indicate discrete prints detected by MATLAB image processing toolbox.

[0064] FIGURE 8: Smaller colossal CdSe / CdS printing results, according to embodiments of the present disclosure. Scanning electron microscopy of 3x3 array ofprinted CdSe / CdS QD ensembles. Synthesized with 30 CdS monolayers, with an average diameter of 26. 3 ± 2.2 nm.

[0065] FIGURE 9A: Single QD nanophotonic cavity heterointegration, according to embodiments of the present disclosure. Fluorescent microscopy of horseshoe¬ shaped cavity with single EHD-printed QD.[00661 FIGURE 9B: Single QD nanophotonic cavity heterointegration, according to embodiments of the present disclosure. SEM image of the cavity region containing single QD.

[0067] FIGURE 9C: Single QD nanophotonic cavity heterointegration, according to embodiments of the present disclosure. Spectrum plot of cavity integrated QD. Inset: Magnified spectrum around the cavity mode (solid) and fit Lorentzian fit (dashed).[0068| FIGURE 9D: Single QD nanophotonic cavity heterointegration, according to embodiments of the present disclosure. Spectrum of the pure QD-coupled cavity' mode transmission to the grating (solid) and Lorentzian fit (dashed), measured at room temperature with 10 uW excitation (FIGURE 9C and FIGURE 9D).

[0069] FIGURE 9E: Single QD nanophotonic cavity heterointegration, according to embodiments of the present disclosure. Power sweep spectrum measurements of QD-coupled cavity at 8 K.

[0070] FIGURE 9F: Single QD nanophotonic cavity heterointegration, according to embodiments of the present disclosure. Pow er dependence of 597 nm (circles), 617 nm (triangles), and 627 nm (squares) peak intensities at 8 K, with pow er-law7fits (dashed lines).

[0071] FIGURE 9G: Second-order time correlation plot and fit of cavity-coupled QD, measured at room temperature with 10 pW excitation, according to embodiments of the present disclosure.

[0072] FIGURE 10: Spectrum of colossal CdSe / CdS QD at 8 K, according to embodiments of the present disclosure. Plotted spectrum of colossal CdSe / CdS QD (80 CdS monolayers) measured at 8 K and 1 W excitation. Measured on SiN substrate, not in a cavity.DETAILED DESCRIPTION

[0073] In an aspect, the present disclosure provides a method of printing a polarizable particle, the method including: applying an electric field for hold time to a tip of a printer nozzle comprising an ink, wherein the electric field comprises an electric fieldstrength and an electric field gradient, and wherein the ink comprises a polarizable particle dispersed m an apolar solvent; and applying the polarizable particle to a substrate.

[0074] As used herein, "polarizable particle" refers to a particle where a dipole moment may be induced when the particle is placed in an electric field.

[0075] As used herein, "apolar solvent" refers to a solvent with a polarizability less than the particles and more specifically a solvent polarity index of between 0.0 and 0.2.

[0076] As used herein, a "group IV composition" refers to a composition consisting of elements in group 14 of the periodic table.

[0077] As used herein, a "group III-V composition" refers to a composition consisting of a mixture of elements m group 13 and group 15 of the periodic table.[00781 As used herein, a "group 1I-V1 composition" refers to a composition consisting of a mixture of elements in group 12 and group 16 of the periodic table.

[0079] This disclosure specifies new regime of EHD printing (this new regime is descnbed herein as electrodynamic (ED) punting, or as single particle extraction electrohydrodynamics (SPEED)), acting on sub-zeptoliter, highly-polarizable. single particles dispersed in relatively non-polarizable solvents, to selectively extract and precisely print individual quantum dots (QDs), a milestone for scalable integration of nanoscale materials. The proliferation of electronic and photonic devices has increased demand for innovations in precise, scalable, and less wasteful fabrication of nanoscale components. Among techniques that can directly integrate device elements with diverse physical properties and compositions, additive manufacturing through inkjet printing has emerged as a versatile method for depositing picoliter liquid volumes, with applications ranging from graphic printing to advanced microelectronics and photonics.

[0080] Printed electronics are particularly materials-efficient as compared to conventional subtractive processing of electronics. Considering the emissions associated with processing alone, printing of electronics has been modeled to have more than two orders of magnitude lower environmental emissions footprint than conventional approaches.

[0081] Electrohydrodynamic (EHD) printing advances inkjet methods by employing electric fields, as opposed to mechanical or thermal stimuli, to manipulate fluid inks. EHD printing can readily achieve patterned feature resolutions wrell below 10 pm. as depicted in FIGURE 1 A, enable attoliter-scale droplet deposition, and facilitate integrationof functional materials onto a variety of substrates. Unlike conventional inkjet droplet formation mechanisms. EHD inkjet uses electnc fields acting on ink components to overcome fluid surface tension barriers that limit the feature size limits of conventional approaches. This enables nanoscale control over deposit size and placement through a transfer mechanism that requires no moving parts, and is readily scalable into parallel printing modules for higher throughput manufacturing.

[0082] In some embodiments the printing method being disclosed further comprises ED or single particle extraction electrohydrodynamics (SPEED) printing,

[0083] In some embodiments, the polarizable particle is selected from the group consisting of a quantum dot. a nanocrystal, a metallic particle, and combination thereof. In some embodiments, the polarizable particle is a quantum dot.

[0984] Commercialized drop-on-demand inkjet heads based on silicon microelectromechanical systems (MEMS) that require complex integration of piezoelectric elements and tight control of nozzle geometry have been scaled to 2048 nozzles monolithically-integrated into single print heads. Even for printing cycle rates as low as 1 Hz per ejected deposit, a similarly manufactured EHD print system, that requires only' the application of electric field directly to the printing ink could deposit thousands of QDs per second from a single head. Parallelized, multiple printhead systems with thousands of nozzles per head running with nozzle firing rates in the kHz. range are now common in industrial piezoelectric inkjet printers.

[0085] These systems are currently7used in manufacturing of large area OLED displays with manufacturing throughputs of 60 seconds per square meter-scale sheet. Research in high-resolution EHD printing has shown that kHz droplet printing rates can also be achieved with EHD at the micron and submicron scale. The scaling of the number of nozzles per EHD print head is also progressing, as reflected in the recent announcement of 128 nozzle MEMS-fabricated EHD print heads operating in the kHz regime. Industrial deployment of multi-head and multi-nozzle printing heads firing at kHz rates may thus be used in the manufacture of, for example, arrays of single QD light sources in an additive, low waste, low temperature, ambient pressure, digitally-controllable process

[0086] FIGLIRE IB schematically illustrates an ED printing setup according to the present disclosure for positioning single QD particles Printing is initiated by applying a voltage between the electrode-integrated high-resolution (<10 pm) borosilicate glass capillary printhead and the ground plane containing the substrate The top inset forFIGURE IB shows a fluorescence microscopy (FLM) image of a capillary printhead loaded with dilute colossal QD suspension showing the presence of isolated emitters that include dispersed single QDs. By varying the printhead-to-substrate standoff height and applied voltage, the electric field intensity can be maximized at the tip interface. Colloidal particles are then driven with respect to the magnitude and direction of the electric field, in an "ink" composed of oleic acid capped CdSe / CdS core / shell QDs suspended m an apolar solution mixture. This particle mobility is achieved by utilizing a medium with a lower relative permittivity than that of the dispersed particles, which gives rise to a polarization disparity between the two that forces the particles towards regions of high electric field intensity. The QDs used in this work were synthesized via a volumetrically tunable strategy that enables the QD core to maintain its quantum-confined optoelectronic characteristics, while increasing the overall size and polarizability7of the particle through the shell design (FIGURE 1C). The tunable polarization is useful for generating the DEP forces that may overcome the net interfacial energies of a single particle, especially when factors like electric field intensity and material properties have finite limits, as discussed m the following sections. The colossal core / shell synthesis yields slightly asymmetric, hexagonal, faceted particles that will be considered as spherical for later numerical and analytical estimations, due to their relatively isotropic morphology. The initial analy sis discloses that the particle asymmetry and related field concentration effects are not likely to significantly change the printing behavior.

[0087] While the results described herein are described with reference to the ED printing setup depicted in FIG. IB, it should be understood that other arrangements of the elements of an ED printing setup consisting with the methods and systems described herein are within the scope of the present disclosure. For instance, FIG. IF depicts an ED printing setup where a first electrode is at the printing nozzle and a second electrode is a ring electrode positioned over the surface of the substrate. Thus, in FIG. IF, it is demonstrated that the second electrode can be repositioned in various embodiments between a position planar with or behind the substrate, to a position above the substrate. An advantage of this alternative configuration is that the substrate material is less relevant to influencing the methods described herein; instead, a QD approaching the substrate at high velocity' is able to be printed to a wide variety of substrates. Other similar configurations may be used and are within the ability of one having ordinary skill in the art.

[0088] In some embodiments, the quantum dot comprises a core and a shell encapsulating the core. In some embodiments, a diameter of the core is about 3.5 nm. In some embodiments, the shell comprises between about 10 monolayers and about 100 monolayers.

[0089] In some embodiments, the core comprises a group IV composition, a group III-V composition, a group II-VI composition, a semi-conducting perovskite, and a chalcogenide semiconductor; and the shell comprises CdS, CsPbBr?,, BaTiO3, or lead zirconium titanates. Without wishing to be bound by an ’ particular theory, perovskites refer to a class of cry stal structures, which m some embodiments may be hybrid organic / inorganic semiconducting perovskites, and in some embodiments may be generally- referred to as semiconducting perovskites. An example of a semiconducting perovskite is CsPbBr3, as opposed to BaTiO3or lead zirconium titanates (PZTs) which are generally not considered semiconductors. In some embodiments, a semiconductor shell may be advantageously used. In some embodiments, BaTiO and PZT advantageously have high dielectric constants (much like semiconducting perovskites) and high polarizabilities (some of the highest available)

[0090] In some embodiments, the shell comprises a dielectric material.

[0091] In some embodiments, the shell comprises a semiconductor material.

[0092] In some embodiments, a band gap of a material comprising the shell is larger than a bandgap of a material comprising the core. Without wishing to be bound by any particular theory-, a band gap of the shell being larger than a band gap of the core tends to stabilize excited states and prevent nonradiative recombination. In such configurations, the electrons and holes in the conduction bands of these dots tends to reside in the smaller energy gap core due to energy minimization. This tends to improve quantum y ields and stabilize excited states because it keeps the excited electrons and holes (and exciton bound pairs of the two) away from the outer semiconductor surfaces, which tend to have defect states to lead to undesirably fast recombination rates.

[0093] In some embodiments, the shell electronically- passivates or optically passivates active defects at a core-shell interface. Without wishing to be bound by any particular theory-, when a quantum dot has a core shell structure of CdSe / CdS, the shell electronically passivates active defects at the core-shell interface. This is at least one reason why a CdSE / CdS quantum dot also have good photoluminescence (PL) quantum yields (a property- that is advantageous m many- quantum dot applications).

[0094] In some embodiments, the group IV composition comprises Si. Ge, or C / nanodiamond. In some embodiments, the group III-V composition comprises GaAs, InP, or antimonides In some embodiments, the group II-VI composition comprises CdS, CdSe, CdTe, ZnSe, ZnS, ZnTe, or CdTe. In some embodiments, the core comprises CdSe. In some embodiments, the shell comprises CdS.

[0095] In some embodiments, the quantum dot has a diameter of between about 10 nm and about 100 nm.

[0096] In some embodiments, the polarizable particle has a total average radius of between about 20 nm and about I pm.

[0097] In some embodiments, the quantum dot further comprises an atomic dopant selected from the group consisting of B, P. As, N, Si, and combinations thereof.[0098| In some embodiments, the polarizable particle has size tunable polarizability and / or polarization. In some embodiments, the polarizable particle has a particle dielectric constant of greater than 2.

[0099] In order to determine the advantageous ED printing and material design parameters, an approach to the process of separating an individual nanoparticle from a liquid-solid interface by first principles is needed. Each interface in a three-phase system has an associated energy that quantifies the intermol ecul ar interactions dictating the work to expand said interface. These energies can be described as the surface free energy (< JSC). surface tension (ctlg), and interfacial tension (ctls), which correspond to the solid-gas, liquid-gas, and liquid-solid interfaces, respectively. By considering the contact angle (0CA) at the liquid-gas interface, the values can be related to one another via Y oung's equation:s = O’SG - LG cos(eGA) (1)

[0100] Conventional EHD printing strategies focus on overcoming the energy of surface tension (FIGURE ID) to generate higher area, reversed curvature liquid-gas interfaces in the form of convex Taylor cones and droplets. Alternatively, to separate a particle from a liquid-solid interface, the focus is on overcoming interfacial tension (FIGURE IE). This energy determines the work (IV) needed io deform the liquid interface around a particle, where A.4 represents the change in interfacial area as the particle passes through the meniscus interface:IV = o-A4 (2)

[0101] The total energy7required can be determined by considering the net positive and negative changes in the interfacial area for each interface. For a sphericalmodel, the force (Fnet) required to overcome the net interfacial forces can then be derived with respect to the translational z-axis, i.e. the printing direction towards the target substrate, where a is particle radius:[0102 Hie components of interfacial tension (Eq. 1) can be measured through optical tensiometry7to determine the Fnetas a function of particle perimeter (see Methods below).

[0103] First, a pendant drop test (FIGURE 2) was performed to assess the surface tension of the apolar solution for printing. Using Young-Laplace approximations for assessing drop curvature, machine vision calculated a mean surface tension of 25.3 ± 0.3 mN / m. which agrees with previously measured values of the solution's constituents. For the free surface energy of the QDs, a sessile drop test was performed on prepared QD thin films, as depicted in FIGURE 3 A, which also agrees with former analysis of the QD ligand chemistry-. Thus, solving for interfacial energy in Eq. 1 results in a value of 6.9 ± 1.0 mN / m, which allows for estimation of the Fneta single particle needs to overcome to be printed.[01041 Tire DEP force (FD£P) of a spherical particle under an applied non-uniform AC field can be solved analytically:FDEP = 7rEma39?[ / c(<z>)] V|E |2(4)

[0105] where Emis the real permitivity of the medium and V| E |2is the gradient of the field magnitude squared for the particle. With the complex permitivities of the particle (f~p) and medium (f~OT), the direction and magnitude of the force is described by / c(to), the frequency dependent Clausius-Mossotti factor:

[0106] Equation 5 states that when the particle is more polarizable than its respective medium, like in the approach that is disclosed here, the particle moves along the electric field gradients towards regions of high field strength, often referred to as positive DEP. For QDs with separate core / shell materials, the real component ofcan be calculated as the volumetric ratio between the shell and core's real permittivities. As the shell diameter increases past the thin (<10 nm) to the thick (10-20 nm) and colossal (20-100 nm) regimes, the contribution of the core to 9i[fc(o>)] becomes negligible, asymptotically approaching 5l[k(o>)] « 0.52 (FIGURE 4).

[0107] For the ED print setup used, the V| E |2at the QD particle at the interface of the printhead's fluid meniscus in the ED printer was > (1023) V2 / m3using a geometric electrical model numerically solving Maxwell equations. Using the measured dimensions of the ED printhead (FIGURES 5A-5D), the environment around the particle was simulated. Here, the conductivity of the particle was assumed to be similar to CdS thin films, (l(U7~10~9) fF'-cm'1, as the CdS constitutes the majority of the material volume at large shell radii and the shell diameter is significantly larger than the Bohr radius for CdS. The plotted z-component of the electric field (Fz) shows a high contrast field intensity difference between the solution and air, which draws the particle towards the higher field intensity.

[0108] Additionally, the z-component of the gradient of the field magnitude squared plot shows significant field enhancement at the particle, increasing as it passes through the solution interface. Using these estimates, FIGURE 3C represents the comparison of FDEPto Fnetand pure surface tension force (FST). Here, the FDEPgrows exponentially with increasing particle radius, overcoming net interfacial forces as the particle enters the colossal regime. However, the DEP forces at this size are significantly less than what would be expected to form a liquid droplet of equivalent size from solution if the ink solution was treated as a continuum fluid as in conventional models for EHD inkjet. By comparing the competing forces, a minimum QD radius of -32 nm is sufficient for overcoming interfacial forces to separate a single QD with the measured interfacial energy from the liquid. To be able to extract and print a single QD and maximize the colloidal stability of these QD solutions, a target particle radius of -35 nm was selected for further experimentation.

[0109] It should be noted that the effects of competing forces on the particle's overall force magnitude and direction are minimal. For example, in polar aqueous QD solutions, reductions in free ion concentration have shown a correlation with increased Debye lengths, due to the QDs requiring larger screening layers to balance charge. While large screening layers reduce the FDEPby coupling to electroosmotic flow around the particle, the selected apolar hydrocarbon solvents contain virtually no free ions, thus preventing the formation of the electric double layer to begin with. Furthermore, the viscous Stokes drag force (Fe) on a particle is equal to the FDEPat terminal velocity in bulk solution until reaching the interface. As the particle approaches the meniscus interface, wfien FDEP> Fnet. the particle decelerates, decreasing Fr, until FDEP= Fnet+ F. At thispoint, the particle continues to move through the interlace according to Newton's second law. Consequently, the drag force does not fundamentally impede the particle from crossing the interface and is therefore not considered a limiting factor. Additionally, other forces determined here to be negligible include Brownian motion, which averages out to zero-force overtime due to its stochastic nature, gravity, which is exceedingly small al this particle scale (< IO~18N); and thermally induced buoyancy. Dimensional analysis of microsystems in apolar solutions have shown that joule heating within the solution is insignificant relative to the strength of an applied non-uniform AC field.

[0110] To test these estimates, CdSe / CdS core / shell QDs were synthesized with a calculated core diameter of 3.5 nm and a designed total average radius of 36 ± 3.1 nm from 80 CdS shell monolayers (see Methods) and suspended in octane:hexadecane with phosphonic and carboxylic ligands to stabilize solubility. FIGURE 6A shows the results of an ED printing trial matrix with this suspension on Indium Tin Oxide (ITO)-coated glass (SiOz) across a variety of voltage amplitudes (500-900 V) and hold times (0.5-2 s), with a fixed bias (1000 V) and frequency (1 kHz). Here, the hold time refers to the period that the amplitude voltage is applied over a target position. Afterwards, using machine vision to count the number of detectable pnnts (see FIGURE 7), the heatmap shows a gradient of successful QD printing, as determined by FLM. As the hold time and amplitude voltage increases, the number of prints made relative to attempts increases.

[0111] Without wishing to be bound by any particular theory, this trend may be explained by the effects of competing forces on the particle's overall force magnitude normal to the meniscus as the QD reaches the interface. The viscous Stokes drag forceon a particle is equal to the FDEP. When FDEP> Fnet, the particle decelerates, decreasing Fvuntil FDEP= Fnet+ FvAt this point, the particle continues to move through the interface according to Newton's second law. Thus, increasing the hold time and / or strength of electric field translates to a longer time for the ejection to occur and faster ejections, respectively. It should be noted that during this printing process, no visible meniscus perturbations (see FIGURE 6C (i) and (ii)) could be discerned through high-magnification observational cameras mounted on the print system, indicating negligible effects of the applied electric fields on the apolar solvent. This, in combination with the approximately 5 pm printing nozzle orifice diameter, which is much larger than the printed QDs. indicates that this nanoscale printing is decoupled from the nozzle size.

[0112] In some embodiments the disclosed method of printing uses a core / shell polarizable particle or plurality' of polarizable particles having a core diameter of less than 10 nm. In some embodiments, the core diameter is 2 nm to 10 nm.

[0113] In some embodiments, the solvent has a solvent dielectric constant that is lower than the particle dielectric constant. In some embodiments, the solvent dielectric constant is less than 10.

[0114] In some embodiments, the apolar solvent comprises a mixture of two or more apolar solvents. In some embodiments, the apolar solvent is a hydrocarbon solvent. In some embodiments, the hydrocarbon solvent is selected from the group consisting of octane, hexadecane, and mixtures thereof.

[0115] In some embodiments, the printer nozzle is coupled to a printhead. In some embodiments, applying the polarizable particle to a substrate comprises dielectrophoretically overcoming surface tension and / or interfacial energy of the apolar solvent to print the polarizable particle.

[0116] Examining the highest print yield array (900 V and 2 s) with SEM, FIGURE 6B summarizes the number of QDs detected per print via SEM, resulting in a single particle yield slightly over 60%. It's worth noting that over 25% of the pnnt sites with 2+ QDs showed intimate contact between QDs. suggesting that they were likely already aggregated before being printed. The remaining multiples were observed as sets of isolated single QDs, within a few hundred nm of one another at each print site. SEM also revealed single particles for positions with no emission (n = 7), indicating that FIGLIRE 6 A underestimates the total printing yields of prints made.

[0117] Without wishing to be bound by any particular theory', this lack of emission may be attributed to either non-radiative recombination from excessive defects in the particles, photobleaching by excitation, or QD-excluded CdS aggregates. The inset of FIGURE 6B shows a 2 x 2 subarray of single QDs from the larger array. The SEMs show the expected faceted structure consistent with the known morphology of these colossal QDs. There is a lack of any observable drying rings or residue in the vicinity of the QDs.

[0118] The lack of meniscus deformation when compared to the printing behavior of conventional thin-shelled QDs seen in FIGURE 6C, in combination with (i) the high surface tension barrier for liquid droplet formation (FIGURE 3C, FSICurve), (ii) the calculated dominance of the dielectric forces for QD over the QD interfacial forces at the meniscus (FIGURE 3C. FDRPand FNET. respectively), and (iii) negligible interaction ofthe printing electric fields with the solvents themselves, with a dielectric constant ~ 2, lays out anew model for ED printing at the nanoscale. This mechanism is formalized as SPEED printing, describing the single-particle extraction of nanocrystals from solution without substantially deforming a bulk liquid meniscus. It is in this disclosure the extraction and directed printing of dry or nearly dry’ core / shell QDs from apolar solutions with appropriate surface energies, dielectric properties and electric field environments for the QDs. COMSOL simulations at the experimental conditions, slightly below the printer's maximum voltages (FIGURE 6B), showed a negligible reduction in field intensity around the particle, showing that single particle printing may be achieved at lower voltages. Experiments with thin-shelled and smaller colossal-shelled (FIGURE 8) CdSe / CdS QDs. failed to achieve individual particle printing, again consisting with the proposed model.[01191 In some embodiments, the polarizable particle further comprises highly polarizable ligand groups. In some embodiments, the ligand group reverses a solubility or dispersibility of the particle from a polar particle surface to within an apolar solvent. In some embodiments, the ligand group reverses a solubility or dispersibility of the particle from being a high surface energy particle to being a low surface energy particle through ligand coverage of a surface of the particle.[01201 In some embodiments, the polarizable particle emits single photons. In some embodiments, the polarizable particle is optically excitable and / or electrically excitable

[0121] In some embodiments, the method further includes applying a light source to excite the polarizable particle in the ink before applying the polarizable particle to the substrate.

[0122] In some embodiments, the method further includes heating the polarizable particle in the ink. Without wishing to be bound by any particular theory, heating the polarizable particle may advantageously increase polarizability'. In some embodiments, heating is by illumination of the polarizable particle.

[0123] Single QDs were also printed on silicon nitride-coated SI wafers to improve the signal-to-noise for spectral analysis. FIGURE 6D shows the room temperature photoluminescence (PL) of a single printed QD with an emission peak at 624 nm, and a full-width half-maximum (FWHM) of ~21 nm, consistent with the same QDs deposited by drop-casting approaches and measured in solution. Second-order correlation Q2)) measurements confirm single-photon emission from printed QDs for the first time.FIGURE 6D shows an example of a QD maintaining its single-photon emissivity < 0.5) after ED printing, a metric for utilizing these materials as single photon sources in quantum device technologies. Sampling an array of printed single QDs (FIGURE 6F) shows single-photon emission, with a mean of ^^(O) = 0.33 ± 0.1.

[0124] In some embodiments, the printhead is operatively coupled to a controller configured to control a first electric field applied to the polarizable particle and a second electric field applied to the substrate. In some embodiments, the controller comprises a tailored waveform generator.

[0125] In some embodiments, applying the electric field comprises applying a voltage between a first electrode and a second electrode, wherein the voltage is between about 500 V to about 900 V, wherein the hold time is between about 0.5 seconds and about 2 seconds, wherein a fixed bias is about 1000 V, and wherein a frequency is about 1 kHz. In some embodiments, the electric field strength is between about 105V / m and about 106V / m.

[0126] In some embodiments, applying the polarizable particle to the substrate occurs without substantially deforming a bulk meniscus at the tip of the printer nozzle.

[0127] In some embodiments, applying the polarizable particle to the substrate occurs without re ersing a curvature of a bulk meniscus at the tip of the printer nozzle relative to an air or gas interface under the meniscus.

[0128] This disclosure demonstrates the utility of high-resolution single QD printing, a horseshoe-shaped nanophotonic crystal cavity was designed and fabricated with a resonant frequency of -614.5 nm and a monolithic waveguide structure that directs emission to rectangular gratings at each end of the horseshoe. Applying the previous strategies for printing, a single QD was positioned m the center of the cavity. This was further enabled by the precision of the step motor driven stage, enabling step precision down to 100 nm (±5%) in lateral directions, sufficient for alignment to the -500 nm critical dimension width of the nanophotonic device target. FIGURE 9A shows a FLM image of the emission from the single QD coupling to the waveguide and scattering from the gratings. SEM inspection of the print site (FIGURE 9B) confirms the presence of the single QD through the identification of the characteristic hexagonal diamond-shaped colossal QD in one the cavities central elliptical wells.

[0129] The PL spectrum from the cavity-integrated QD in FIGURE 9C reveals the coupling between the cavity's sharp resonant mode and a broad QD emission at 70 K,a condition chosen for its high emission intensity. Examining the narrow spectrum around the cavity mode (FIGURE 9C, inset) is consistent with a modest Fano interference, indicated by the characteristic Fano line shape, which is more apparent at room temperature (FIGURE 10). Measuring the room temperature PL from the cavity grating, at either end of the horseshoe, isolates emission coupled to the cavity mode. FIGURE 9D shows this sharp Lorentzian mode, with a quality factor of 12.500, measured from the Lorentzian fit linewidth over the center wavelength. Similar to our printed arrays, photobleaching also occurred in other single QD-integrated cavities, resulting in only the emission from the SiN background and cavity mode.

[0130] The QD-cavity system was then measured in a cryostat (8 K) across multiple excitation powers (1-50 uW) to examine the broadened tail emission. FIGURE 9D show s the separation of the broader room-temperature emission into an excitonic peak (617 nm) and its phonon sideband (627 nm). At higher power (>5 pW), the emergence of a secondary' high-energy peak (597 nm) can be identified, attributable to a multi-excitonic transaction, accompanied by its own phonon sideband (605 nm).

[0131] While these behaviors aren't characteristic of the observed single excitonic and phonon sideband emission is consistent with non-cavity QDs and the literature, at low' temperature. As shown in FIGURE 9F, the exciton and phonon sideband scale nearly linearly with excitation power The high-energy peak is highly non-linear, with an exponent of 2., suggesting a multi-excitonic origin. Lastly, a$®(r) measurement of the QD-cavity' at room temperature (FIGURE 9F) shows the coupled system maintaining its single-photon emission.

[0132] Colloidal QDs have been discussed for quantum optoelectronic applications since their inception yet have largely been outside of practical considerations due to the challenges associated with their integration into devices The technologies disclosed demonstrated the first additive nanomanufacturing strategy for deterministically positioning single QDs that exhibit single-photon emission. Not only does this approach allow high throughput printing of large array's of QDs at room temperature, without resorting to vacuum processing or lithography, but it also allows for the positioned deposition of QDs into prefabricated nanophotonic elements such as high-Q cavities.

[0133] The disclosed printing is likely enabled by a new electrohydrodynamic printing mechanism, single particle extraction electrohydrodynamics (SPEED) printing, defined by dielectrophoretic expulsion of essentially dry, highly' polarizable single particlesfrom a relatively non-interacting solvent medium. The printing mechanism requires particles with sufficient dielectric contrast from the solvent, which can be realized with typical semiconductor nanocrystals at sizes that are now synthetically achievable Colossal- shelled (—70 nm) CdSe / CdS particles with oleate surface ligands, and a bulk particle to solvent dielectric constant ratio, of 9:2 were used to demonstrate single particle printing. The method is applicable to other colloidal nanoparticles, from halide perovskites, to oxides and nanodiamonds that can be synthesized into single or multi-component particles with a sufficiently high overall polarizability and particle to solvent dielectric contrast, size, appropriate surface energy and stability' in apolar solvents such that the dieletrophoretic forces can overcome surface energetics as described in the Results discussion here. This SPEED printing process opens the door to a scalable, contactless, zero-wasted additive nanomanufacturing process that can be conducted at ambient conditions to enable the positioning of single discrete colloidal QDs. Even under early-stage, non-optimized conditions and chemistries, single-particle deterministic planting yields reached over 60%, validating the underlying mechanism and enabling pathway optimization moving forward. These results represent significant progress in realizing scalable photonic qubit platforms and the future development of quantum optoelectronics. This disclosure represents a step forward for the additive manufacturing of materials, where low-waste printing processes can match and even exceed the capabilities of conventional subtractive and complex semiconductor fabrication processes.

[0134] In an aspect, the present disclosure provides a layer of a device fabricated by any of the methods described herein. In some embodiments, the device is an optical quantum device, a nano-transistor, a sensor, a light-emitting diode, a single-photon source, or a CMOS circuit.

[0135] In an aspect, the present disclosure provides a system for printing a polarizable particle, the system including: an ink including a polarizable particle dispersed in an apolar solvent; and a printer, the printer including: a print head: a printer nozzle comprising a print tip, the printer nozzle being coupled to the print head and being sized and shaped to contain the ink; an electric field source; a platform sized and shaped to mount a substrate; and a controller operatively coupled to the printer, the controller including at least one processor and a computer-readable medium having computerexecutable instructions stored thereon that, m response to execution by the at least oneprocessor, cause the controller to perform operations including: applying an electric field for a hold time to the tip, thereby applying the polarizable particle to the substrate,EXPERIMENTAL

[0136] Chemicals and Materials

[0137] All chemicals listed below were used without further purification, unless stated otherwise. Oleic acid (>90%), anhydrous methyl acetate (99.5%), selenium powder (99.999%, 100 mesh), cadmium oxide powder (CdO, 99.9%), trioctylphosphine oxide (TOPO, 99%), trioctylphosphine (TOP, 90%), 1 -octanethiol (99%), 1 -octadecene (ODE, 90%), and anhydrous hexane (95%) were purchased from MilliporeSigma, and n-octadecylphosphonic acid (ODPA, 99%) was purchased from PCI Synthesis. Cadmium oleate solution (0.2 M in ODE) was made by heating CdO (2.57 g), oleic acid (63 mL), and ODE (27 mL) at 160 °C for 30 mm, following by evacuating the solution at 110 °C for I h.

[0138] Methods

[0139] CdSe QD Synthesis

[0140] The synthesis of colossal CdSe / 80CdS QDs (CdSe with 80 monolayers (ML) of CdS) was conducted according to methods reported previously. The wurtzite CdSe core synthesis started with adding TOPO (3 g). CdO (0.06 g), ODPA (0.28 g), and a magnetic stir bar to a 15 mL three-neck round-bottom flask secured with a septum, a thermowell equipped with a thermometer, and a condenser. The flask was put under vacuum for 30 min at 100 °C, then was refilled with N2. The temperature as then set to 375 °C. A dropwise addition of TOP (1.5 mL) was done while the temperature was ramping up from 320 to 370 °C. When the temperature was at 375 °C, a solution of Se powder (0.058 g) dissolved in TOP (0.4 mL) w as quickly injected. After 45 s, the flask was quickly cooled to room temperature with forced air to yield CdSe QDs The QDs were purified in a glovebox by centrifugation with methyl acetate / hexane and w ere stored m hexane.

[0141] Shelling of CdSe with CdS

[0142] ODE (6 mL) was added into a 25 mL three-neck round-bottom flask secured with a septum, a thermowell equipped with a thermometer, and a condenser, which as put under vacuum at 110 °C for 60 min, then refilled with N2gas. An amount of CdSe core in hexane (typically 5-100 nmol) was added to the flask. Hexane was completely removed by evacuating the flask 110 °C for 30 minutes. The flask was then heated to 310 °C. When the temperature w?as at 260 °C. 0.2 M Cd(01eate)2and 0,2 M 1 -octanethiolsolutions were slowly injected into the reaction flask using a dual-syringe pump with the rate of 3 mL / h. The volumes of the shell precursors were calculated to achieve 30 MLs of CdS shells on QD cores with a diameter of -3.5 nm. After the injection finished, the reaction was annealed at 280 °C for 2 h, then cooled down to 60 °C. Without purification, a portion of the yellow CdSe 30 CdS solution w as transferred to a different 3-neck roundbottom flask for another shelling step that targeted additional 20 CdS MLs to achieve CdSe 50 CdS using the same shelling procedure. This step was repeated one more time to achieve CdSe 80 CdS. The final product was purified in a glovebox with hexane and was stored in hexane. Detailed calculations of shell precursor amounts were described m a previous report.

[0143] QD Ink Preparation[01441 The QD ink was prepared by evaporating a hexane-based QD solution under vacuum at 100 °C for 30 min, yielding -3 mg of bright yellow QD powder. The resulting powder was subsequently dispersed m 10 mL of a 1:1 octane:hexadecane mixture through stirring at 80 " C for 1 h, followed by sonication 1 h.

[0145] Pendant Drop Tensiometry

[0146] The video image is calibrated to the outer diameter of the dispensing syringe of a Kriiss drop shape analyzer to establish the scale and obtain accurate drop dimensions. The shape of the drop was then analyzed through grayscale shadow image processing. A shape parameter was adjusted iteratively by a numerical model until the computed drop shape matches the observed one. Finally, the surface tension was calculated based on the solution density and the optimized shape parameter, to be 25.3 ±0.3 mN / m.

[0147] Sessile Drop Tensiometry[01481 A substrate for the sessile drop tensiometry was prepared via spin coating CdSe / CdS on a glass substrate. Using a Kriiss drop shape analyzer, a drop was deposited onto the solid sample, and its image w as captured using a camera, then processed through drop shape analysis software. The drop's contour was first identified using grayscale shadow image analysis. Next, a geometric model was applied to fit the identified contour The contact angle w as determined as the angle betw een the fitted drop shape and the surface of the sample. These were determined as 92.3° ± 2.0° and 18.5° ± 2.9° for water and 1:1 octane:hexadecane, respectively. After the drop shape and contact angle ere measured, the surface free energy of the solid sample was calculated using a combination of contactangles from multiple probe liquids (water and 1:1 octane:hexadecane) with known surface tensions, to be 30.8 ± 1.0 mN / m.

[0149] E 'inite Element Analysis

[0150] Simulation was performed with the electric current (EC) package within the AC / DC Module using COMSOL Multiphysics. Permittivity and conductivity of the materials were used to perform the simulation. Physical dimensions of the components were modeled after micrographs (printing nozzle), SEM characterization (quantum dot) and measured substrate thickness. A source voltage of 2000 V was used as a stimulus to the electrode voltage, and the printing bed was used as the reference ground for the applied voltage, both analogous to the actual printing setup. A 2D axial rotationally symmetric simulation was performed for the analysis. A flat meniscus was assumed for the liquid-gas interface.

[0151] Electrohydrodynamic Inkjet Printing

[0152] Electrohydrodynamic inkjet printing was conducted by loading the prepared CdSe / CdS ink into pulled borosilicate glass capillary' pipettes with a tip internal nozzle diameter of -5 pm into a SIJ-050 Super Inkjet Printer. These printheads were manufactured with a tungsten electrode filament integrated inside this pipette. After mounting the printhead into the printer and placing the substrate on a grounded stage vacuum chuck, printing could be initiated. For the nanophotonic cavity, an alignment process was used to map the designed printing pattern to the orientation of the target substrate. Upon completion, printing was initiated with the following parameters: bias: 1000 V, amplitude: 900-1000 V, frequency: 1 kHz, hold time 1-2 seconds.

[0153] Photoluminescence Characterization of Bare Substrate QD

[0154] Single-particle characterization was performed in air using a custom-built scanning PL set-up, A 532 nm continuous-wave laser (Laserglow Technologies 532 nm DPSS Laser) was focused on the particles with a 100x (NA 0.95) dry objective lens with a typical excitation power of 10 pW. The laser spot position was controlled via a steering mirror (Newport FSM-300-01 ). The collected PL was filtered through both a 550 nm long-pass filter and a bandpass filtered centered on 618 nm with 50 nm bandwidth. The collected PL was fiber-coupled either to a spectrometer (Princeton Instruments Isoplane 100) to collect the single-particle spectrum or through a 50:50 fiber splitter to a pair of avalanche photodiodes (MPD-PDM) to collect the g(2)spectrum. For the g(2)spectra, the time correlation was performed via a time tagger (PicoQuant TimeHarp 260).

[0155] Nanophotonic Cavity Fabrication

[0156] The SiN nanobeam cavities were designed for operation on a SiCh substrate with no top cladding in 220 nm thick SiN. The cavity was formed by punching a one-dimensional array of elliptical holes in a 550 nm wide SiN waveguide. The dimensions of the elliptical holes were fixed to a major diameter of 411 nm and a minor diameter of 98 nm. Each half of the cavity consisted of 10 elliptical holes that quadratically tapered from a period of 184 nm to 190 nm An additional 20 elliptical holes with a period of 193 nm were placed on either end to form the cavity mirrors. According to FDTD simulations, this resulted m a cavity mode at 618 nm with quality factor - 4x10’ and mode volume ~ 2 (AAZ)3. To fabricate the nanobeam cavities, 100 kV ebeam-lithography was used to transfer the pattern to a positive-tone ebeam resist. The pattern was then etched into the SiN thin film using a fluorine-based plasma etch.

[0157] Photoluminescence Characterization of Cavity -Integrated QD

[0158] Measurements were performed in a confocal setup operating in ambient conditions. Green continuous wave 532nm laser light (LaserQuantum opus532) was passed through a 532 dichroic mirror (Chroma ZT532RDC) focused onto the center of the cavity using a 40x / 0.6 NA Olympus objective. A 580LP was used to filter out excitation light so that PL spectra went to a Princeton Instruments 300 grooves / mm grating spectrometer (SpectraPro HRS-750) coupled to a Pixis CCD (PIXIS: 100BR eXcel on). Confocal scans were performed using a SPCM (Excehtas SPCM-AQ4C) coupled to a N1DAQ (BNC- 2110). g2 was measured by going through a 40:60 fiber beam splitter and measured using a timetagger (Swabian Instruments Timetagger Ultra). All low temperature measurements were done with a Montana cryostat (cryostation S-series) operating at 8K. Peaks in FIGURE 9E were integrated and fit to a power law / — a / ’b(FIGURE 9F), with the emission intensities scaling with excitation power (P): excitonic (P1), multi-excitonic (P2or higher), and phonon-assisted (P1or higher).

[0159] Disclosed are several specific advancements and novel concepts.

[0160] In this disclosure it is demonstrated and identified a new printing model using ED that can extract dry and nearly dry particles from a suspension or dispersion at the nanoscale. This is fundamentally different from conventional 'continuum' models for ED and other printing techniques where the printing ink is considered as a fluid with continuous properties. Disclosed, the ink acts as a heterogenous material i.e. the electric fields and other parameters are varied to transport specific materials in the ink

[0161] High dielectric constant and high polarizability particles vs. lower dielectric constant solvent

[0162] Disclosed is the use of core / shell particles or QDs with a large high polarizability volume to enable single particle or QD printing or faster or more precise printing,[01631 Disclosed is the use of high polarizability ligands to enable single particle or QD printing or faster or more precise printing.

[0014] Disclosed is the use of extrinsic doping from impurities or defects within the printing particles including

[0165] Disclosed is the use of electrical dopants for semiconductors such as substitutional atomic dopants including B. P, As, N. Si, or other elemental dopants. Structural defects such as vacancies or interstitials that increase the charge carrier concentrations or otherwise increase the polarizability. Charge transfer doping from core to shell or shell to shell in a multishelled particle. High dielectric constant materials such as perovksites as cores or shells including but not limited to CsPbBrs, BaTiO^, or lead zirconium titanates.

[0166] Disclosed is the use of highly polarizable ligand groups such as ligands with lone electron pairs, local ionic charge or zwitterions.

[0167] Disclosed is the use of induction of specific electric field configurations induced in or around the particle that produce a specific response to the applied electric fields during printing, such as different three-dimensional electric fields induced around the printing particles using more than one or more than two electrodes. To first order, one would expect a uniaxial dipole polarization to occur around particles such as QDs in the print ink. Electric field simulations have shown, however, that higher order electric field distributions may be present, for example more complex multipolar (e.g. quadupole and asymmetric quadrupole field configurations). Hie following is 2D cross section example of the simulated gradient of the electric field squared near a QD at the liquid / air interface under an applied electric field showing complex field behavior. Specific field configuration may result in higher electromotive force on the particle and be advantageous for printing.[01681 Disclosed is the use of special particle shapes and morphologies

[0169] It is known that local field concentrations and field reductions can occur at high aspect ratio convex features or concave features, respectively.

[0170] Advantageous particle shapes could be introduced via particle synthesis or subsequent processing and could appear in the core or shell materials or via anisotropic ligands or ligand distributions

[0171] An advantageous shape could be particles with generally aspherical shape, or faceted shapes with small radius of curvature vertices or points at one or more locations on the particle. This could include lengthened structures such as nanorods or wires, or faceted shapes such as pyramidial, diamond-like, conical, or lenticular shapes. The field concentrations promoted by these shapes could effectively increase the dielectrophoretic forces on the particle and lead to low voltage or more selective or precise printing of such particles.

[0172] Disclosed is the use of Photon-assisted ED printing

[0173] Increasing the polarizability7by intentionally illuminating components in the ink e.g. quantum dots, nanocrystals, molecular absorbers to assist the printing process such that the excited states of these components respond more readily to the electric field driving the ED process.

[0174] Illumination to cause the promotion of electrons and holes into mobile states or increasing the free charge carrier density7thereby increasing the effective polarizability or dielectric constant of the illuminated species so that they respond more readily to ED printing manipulation. Illumination could also have other positive effects such as depopulation of carriers in trap states which could also affect its polarizability7and responsivity7to the

[0175] Using modulated illumination to control if and when droplets are ejected. This could provide better control of the printing process including better yield, faster printing, and better positioning accuracy.

[0176] It can be expected that when the light is on, there is a higher polarization of the illuminated species in the ink, such as QDs. This would tend to make them respond more strongly to the electric fields induced in the ED printing head such that absorber particles in the ink, such as QDs would respond more strongly, be induced to move at higher velocities in the fluid and / or be more easily ejected from the nozzle and accelerated towards the substrate.

[0177] The printing system could be operated in a state whereby electrical stimulation alone through the applications of varying potentials and electric fields, the printer is 'sub critical' without sufficient illuminations, in that there is not enough force toprint panicles. When light is applied, however, this would increase the particles response to the applied field and result m particle or droplet printing. The controlled modulation of the light could then be used to digitally control printing.

[0178] Illumination with a controlled spectral distribution could be used to select species from the printing ink to be printed. For example, degraded quantum dots or nanocrystals or QDs of a different size than is desired, may absorb incident light at different wavelengths from 'good' species or not absorb the light at all or even if they do absorb light, it may not beneficially affect their response to the ED printing. In this way, the illumination could be selected to preferentially cause printing of target species and not undesired species. The undesired species and their differences in optical response that could be used to restnct printing may result from degradation, oxidation, size change, aggregation or imperfections in size or composition from synthesis or interactions occurring after the synthesis of the ink components while in storage or while in use in the printing.

[0179] Providing illumination by a light source, laser. LED from underneath the substrate using a transparent printing stage

[0180] Providing illumination through the glass capdlary of the print head or an additional adjacent optical guide or sheath to effectively bring light to the printing head. Brightness around the glass region of the glass printing nozzle and the tip of the nozzle indicate waveguiding of photoluminescence from ink. This waveguiding effect could be used to bring light into the printing ink and meniscus region leading to absorption, higher free carrier densities.

[0181] Providing light in a coaxial fashion where the illumination follows a path that is coaxial or parallel to the direction of the movement of the printed drops or particles.

[0182] Providing time modulated illumination or patterned illumination from above, below or from the printing substrate to trigger or enhance the printing process to form a desired pattern.

[0183] Selecting the illumination wavelength and the particle and solvent absorption such that the particles or solvent are selectively affected vs other components of the printing ink.

[0184] Disclosed is the use of photothermal processes to locally heat particles or molecular species to affect their printing from the print nozzle.

[0185] Photothermal effects can directly increase the free carrier density and thereby increase the polarizability, dielectric constant and responsivity to the ED printing electric fields.

[0186] Other photothermal effects could locally change materials properties (decrease viscosity, density, or induce a phase transition that could enhance the printing process whereby enhancement means allowing for the printing of smaller particles, more precise positioning of particles or faster printing rates.

[0187] Disclosed is the use of integrated light sources and cameras to be able to image individual species in the ink and that are printed to allow for improved control of the printing process.

[0188] Disclosed is the use of optical filters after the light / ink interaction but before the camera or detector such that the source light is significantly reduced in intensity while the emission from the target species in the ink is less reduced in intensity at the camera or detector to increase the signal to noise.

[0189] For any cases of optical or thermal assistance to the printing process it may be advantageous to introduce a controlled inert, reduced moistures or reduced oxygen or vacuum ambient environment in the vicinity of the printing nozzle and / or target substrate to reduce detrimental interactions between the particles and the ambient.

[0190] Disclosed is the use of any of the materials and techniques above such that printing can be achieved at electric fields below the dielectric breakdown limit of air, a controlled environment or vacuum. The dielectric breakdown limit or dielectric strength of air is approximately 30 kV / cm or 3×106V / m. The dielectric strength of nitrogen gas is ~ 15% higher than air.

[0191] Non-Limiting Applications for Disclosed Techniques

[0192] Optoelectronics and nanoelectronics such as for the additive heterointegration of single or small numbers of quantum dots or nanocrystals onto photonic or electronics structures.

[0193] Microelectronics for the printing of high -resolution electrical interconnects, dielectrics or vias

[0194] Biomedical applications such as for the printing or delivery of single species such as QD tagged cells, DNA, protein or other biomolecules or biomolecule assemblies.

[0195] High resolution printing of quantum dots, semiconductor nanocrystals such as group IV (including Si, Ge, C / nanodiamond), III-V (including GaAs, InP, antimonides), II-VI (including CdS, CdSe, CdTe, ZnSe, ZnS, ZnTe. CdTe), perovskites, and chalcogenide semiconductors.

[0196] The detailed description set forth above in connection with the appended drawings, where like numerals reference like elements, are intended as a description of various embodiments of the present disclosure and are not intended to represent the only embodiments. Each embodiment described in this disclosure is provided as a representative example or illustration and should not be construed as preferred or advantageous over other embodiments. The representative examples provided herein are not intended to be exhaustive or to limit the disclosure to the precise forms disclosed. Similarly, any steps described herein may be interchangeable with other steps, or combinations of steps, in order to achieve the same or substantially similar result. Generally, the embodiments disclosed herein are non-limiting, and the inventors contemplate that other embodiments within the scope of this disclosure may include structures and functionalities from more than one specific embodiment shown in the figures and described in the specification. That is, the present disclosure includes embodiments that combine features from different embodiments.

[0197] In the foregoing description, specific details are set forth to provide a thorough understanding of exemplary embodiments of the present disclosure. It will be apparent to one skilled in the art, however, that the embodiments disclosed herein may be practiced without embodying all the specific details. In some instances, well-known process steps have not been described in detail in order not to unnecessarily obscure various aspects of the present disclosure. Further, it will be appreciated that embodiments of the present disclosure may employ any combination of features described herein.

[0198] In the detailed description herein, references to "one embodiment," "an embodiment," "an example embodiment,” "some embodiments," "one or more embodiments," etc., indicate that the embodiment described may include a particular feature, structure, or characteristic, but every embodiment may not necessarily include the particular feature, structure, or characteristic. Moreover, such phrases are not necessarily referring to the same embodiment. In addition, when a particular feature, structure, or characteristic is described in connection with an embodiment, it is submitted that it is within the knowledge of one skilled in the art to affect such feature, structure, or characteristic inconnection with other embodiments whether or not explicitly described. After reading the description, it will be apparent to one skilled in the relevant art(s) how to implement the disclosure in alternative embodiments Thus, it will be appreciated that embodiments of the present disclosure may employ any combination of features described herein. All such combinations or sub-combinations of features are within the scope of the present disclosure.

[0199] In view of the limitations of the processing techniques available in the field, the terms "approximately", "substantially", and "about" reflect a certain inability (or uncertainty) to precisely control the exact dimensions of certain features and measurements described herein. Depending on the level of precision that can be achieved using the commercially available processing and measurement tools available at the time, the terms "approximately", "substantially", and "about" may be used to mean within ±5% of a target value for some features. The terms "approximately", "substantially", and "about" may include the target value.

[0200] Throughout this specification, terms of art may be used. These terms are to take on their ordinary meaning in the art from which they come, unless specifically defined herein or the context of their use would clearly suggest otherwise,

[0201] The drawings in the FIGURES are not to scale. Similar elements are generally denoted by similar references in the FIGURES. For the purposes of this disclosure, the same or similar elements may bear the same references. Furthermore, the presence of reference numbers or letters in the drawings cannot be considered limiting, even when such numbers or letters are indicated in the claims.

[0202] Terms such as "a." "an." "the," and "said" are used to indicate the presence of one or more elements and components. The terms "comprise." "include," "have," "contain," and their variants are used to be open ended and may include or encompass additional elements, components, etc., in addition to the listed elements, components, etc., unless otherwise specified. The terms "first." "second," etc. may be used as differentiating identifiers of individual or respective components among a group thereof, rather than as a descriptor of a number of the components, unless clearly indicated otherwise

[0203] Although relative terms such as "on," "below," "upper," "lower," "top," "botom," "right." and "left" may be used to describe the relative spatial relationships of certain structural features, these terms are used for convenience only, as a direction in the examples. Thus, if a structure is turned upside down, the "upper" component will becomea "lower" component. When a structure or feature is described as being "on" (or formed on) another structure or feature, the structure can be positioned directly on (z.e., contacting) the other structure, without any other structures or features intervening between the structure and the other structure. When a structure or feature is described as being "over" (or formed over) another structure or feature, the structure can be positioned over the other structure, with or without other structures or features intervening between them.

[0204] When two components are described as being "coupled to” each other, the components can be electrically coupled to each other, with or without other components being electrically coupled and intervening between them. When two components are described as being "directly coupled to" each other, the components can be electrically coupled to each other, without other components being electrically coupled between them.

[0205] The present application may also reference quantities and numbers. Unless specifically stated, such quantities and numbers are not to be considered restrictive, but exemplary of the possible quantities or numbers associated with the present application. Also in this regard, the present application may use the term "plurality" to reference a quantity or number. In this regard, the term "plurality" is meant to be any number that is more than one, for example, two, three, four, five, etc. The term "based upon" means "based at least partially upon. "

[0206] Embodiments disclosed herein may utilize circuitry in order to implement technologies and methodologies described herein, operatively connect two or more components, generate information, determine operation conditions, control an appliance, device, or method, and / or the like. Circuitry of any type can be used. In an embodiment, circuitry includes, among other things, one or more computing devices such as a processor (e.g., a microprocessor), a central processing unit (CPU), a digital signal processor (DSP), an application-specific integrated circuit (ASIC), a field-programmable gate array (FPGA), or the like, or any combinations thereof, and can include discrete digital or analog circuit elements or electronics, or combinations thereof.

[0207] An embodiment includes one or more data stores that, for example, store instructions or data Non-limiting examples of one or more data stores include volatile memory (e.g., Random Access memory (RAM), Dynamic Random Access memory (DRAM), or the like), non-volatile memory (e.g,, Read-Only memory (ROM), Electrically Erasable Programmable Read-Only memory (EEPROM). Compact Disc Read-Only memory (CD-ROM), or the like), persistent memory, or the like. Further non-limitingexamples of one or more data stores include Erasable Programmable Read-Only memory (EPROM), flash memory, or the like. The one or more data stores can be connected to. for example, one or more computing devices by one or more instructions, data, or power buses.

[0208] In an embodiment, circuitry includes a computer-readable media drive or memory slot configured to accept sign al -bearing medium (e g., computer-readable memory’ media, computer-readable recording media, or the like). In an embodiment, a program for causing a system to execute any of the disclosed methods can be stored on, for example, a computer-readable recording medium (CRMM), a signal-bearing medium, or the like. Nonlimiting examples of signal-bearing media include a recordable type medium such as any form of flash memory, magnetic tape, floppy disk, a hard disk drive, a Compact Disc (CD), a Digital Video Disk (DVD). Blu-Ray Disc, a digital tape, a computer memory, or the like, as well as transmission type medium such as a digital and / or an analog communication medium (e.g., a fiber optic cable, a waveguide, a wired communications link, a wireless communication link (e.g., transmitter, receiver, transceiver, transmission logic, reception logic, etc.). Further non-limiting examples of signal-bearing media include, but are not limited to, DVD-ROM, DVD-RAM, DVD+RW, DVD-R W, DVD-R, DVD+R, CD-ROM, Super Audio CD, CD-R, CD+R, CD+RW, CD-RW, Video Compact Discs, Super Video Discs, flash memory, magnetic tape, magneto-optic disk, MINIDISC, non-volatile memory card. EEPROM, optical disk, optical storage, RAM. ROM, system memory, web server, or the like.

[0209] The principles, representative embodiments, and modes of operation of the present disclosure have been described in the foregoing description. However, aspects of the present disclosure, which are intended to be protected, are not to be construed as limited to the particular embodiments disclosed. Further, the embodiments described herein are to be regarded as illustrative rather than restrictive. It will be appreciated that variations and changes may be made by others, and equivalents employed, without departing from the spirit of the present disclosure. Accordingly’, it is expressly intended that all such variations, changes, and equivalents fall within the spirit and scope of the present disclosure as claimed.

[0210] While illustrative embodiments have been illustrated and described, it will be appreciated that various changes can be made therein without departing from the spirit and scope of the invention.NON-LIMITING EMBODIMENTS

[0211] While general features of the disclosure are described and shown and particular features of the disclosure are set forth in the claims, the following non-limiting embodiments relate to features, and combinations of features, that are explicitly envisioned as being part of the disclosure. The following non-limiting embodiments contain elements that are modular and can be combined with each other in any number, order, or combination to form a new non-limiting embodiment, which can itself be further combined with other non-limiting embodiments.

[0212] Embodiment!. A method of printing a polarizable particle, the method including: applying an electric field for a hold time to a tip of a printer nozzle comprising an ink. wherein the electric field comprises an electric field strength and an electric field gradient, and w-herein the ink comprises a polarizable particle dispersed in an apolar solvent; and applying the polarizable particle to a substrate.

[0213] Embodiment 2. The method of printing of Embodiment 1 or any other Embodiment, wherein the polarizable particle is selected from the group consisting of a quantum dot, a nanocrystal, a metallic particle, and combination thereof

[0214] Embodiment 3. The method of printing of any of Embodiments 1-2 or any other Embodiment, wherein the quantum dot comprises a core and a shell encapsulating the core.

[0215] Embodiment 4. The method of printing of any of Embodiments 1-3 or any other Embodiment, w herein a diameter of the core is about 3.5 nm.

[0216] Embodiment 3. The method of printing of any of Embodiments 1-4 or any other Embodiment, wherein the shell comprises between about 10 monolayers and about 100 monolayers.

[0217] Embodiment 6. The method of printing of any of Embodiments 1-5 or any other Embodiment, wherein the core is selected from a group IV composition, a group III-V composition, a group II-VI composition, a semi-conducting perovskite, and a chalcogenide semiconductor: and wherein the shell is selected from CdS, CsPbBr3, BaTiO3, or lead zirconium titanates.[02181 Embodiment 7. The method of printing of any of Embodiments 1-6 or any other Embodiment, wherein the shell comprises a dielectric material.

[0219] Embodiment 8. The method of printing of any of Embodiments 1-7 or any other Embodiment, wherein the shell comprises a semiconductor material.

[0220] Embodiment 9. The method of printing of any of Embodiments 1-8 or any other Embodiment, wherein a band gap of a material comprising the shell is larger than a bandgap of a material comprising the core.

[0221] Embodiment 10. The method of printing of any of Embodiments 1-9 or any other Embodiment, wherein the shell electronically passivates or optically passivates active defects at a core-shell interface.

[0222] Embodiment 11. The method of printing of any of Embodiments 1-10 or any other Embodiment, wherein the group IV composition comprises Si, Ge, or C / nanodiamond.

[0223] Embodiment 12. The method of printing of any of Embodiments 1-11 or any other Embodiment, wherein the group III-V composition comprises GaAs, InP, or antimonides.

[0224] Embodiment 13. The method of printing of any of Embodiments 1-12 or any other Embodiment, wherein the group II-VI composition comprises CdS. CdSe, CdTe, ZnSe, ZnS. ZnTe, or CdTe.

[0225] Embodiment 14. The method of printing of any of Embodiments 1-13 or any other Embodiment, wherein the core comprises CdSe.

[0226] Embodiment 15. The method of printing of any of Embodiments 1-14 or any other Embodiment, wherein the shell comprises CdS.

[0227] Embodiment 16. The method of printing of any of Embodiments 1-15 or any other Embodiment, wherein the quantum dot has a diameter of between about 10 nm and about 100 nm.

[0228] Embodiment 17. The method of printing of any of Embodiments 1-16 or any other Embodiment, wherein the polarizable particle has a total average radius of between about 20 nm and about 1 pm.

[0229] Embodiment 18. The method of printing of any of Embodiments 1-17 or any other Embodiment, wherein the quantum dot further comprises an atomic dopant selected from the group consisting of B. P, As, N, Si, and combinations thereof.

[0230] Embodiment 19. The method of printing of any of Embodiments 1-18 or any other Embodiment, wherein the polarizable particle has size tunable polarizability and / or polarization.

[0231] Embodiment 20, The method of printing of any of Embodiments 1-19 or any other Embodiment, wherein the polarizable particle has a particle dielectric constant of greater than 2.

[0232] Embodiment 21. The method of printing of any of Embodiments 1 -20 or any other Embodiment, wherein the solvent has a solvent dielectric constant that is lower than the particle dielectric constant.

[0233] Embodiment 22. The method of printing of any of Embodiments 1-21 or any other Embodiment, wherein the solvent dielectric constant is less than 10.

[0234] Embodiment 23. The method of printing of any of Embodiments 1-22 or any other Embodiment, wherein the apolar solvent comprises a mixture of two or more apolar solvents.

[0235] Embodiment 24. The method of printing of any of Embodiments 1-23 or any other Embodiment, wherein the apolar solvent is a hydrocarbon solvent.

[0236] Embodiment 25. The method of printing of any of Embodiments 1-24 or any other Embodiment, wherein the hydrocarbon solvent is selected from the group consisting of octane, hexadecane, and mixtures thereof.

[0237] Embodiment 26. The method of printing of any of Embodiments 1 -25 or any other Embodiment, wherein the printer nozzle is coupled to a printhead.

[0238] Embodiment 27, The method of printing of any of Embodiments 1-26 or any other Embodiment, wherein applying the polarizable particle to a substrate comprises dielectrophoretically overcoming surface tension and / or interfacial energy of the apolar solvent to print the polarizable particle.

[0239] Embodiment 28. The method of printing of any of Embodiments 1-27 or any other Embodiment, wherein the printhead is operatively coupled to a controller configured to control a first electric field applied to the polarizable particle and a second electric field applied to the substrate.

[0240] Embodiment 29. The method of printing of any of Embodiments 1-28 or any other Embodiment, wherein the controller comprises a tailored waveform generator

[0241] Embodiment 30. The method of printing of any of Embodiments 1-29 or any other Embodiment, wherein the polarizable particle further comprises highly polarizable ligand groups.

[0242] Embodiment 31, The method of printing of any of Embodiments 1-30 or any other Embodiment, wherein the ligand group reverses a solubility or dispersibility of the particle from a polar particle surface to within an apolar solvent.

[0243] Embodiment 32. The method of printing of any of Embodiments 1-31 or any other Embodiment, wherein the ligand group reverses a solubility or dispersibility of the particle from being a high surface energy particle to being a low surface energy particle through ligand coverage of a surface of the particle

[0244] Embodiment 33, The method of printing of any of Embodiments 1-32 or any other Embodiment, wherein applying the electric field comprises applying a voltage between a first electrode and a second electrode, wherein the voltage is between about 500 V to about 900 V, wherein the hold time is between about 0.5 seconds and about 2 seconds, wherein a fixed bias is about 1000 V, and wherein a frequency is about 1 kHz.

[0245] Embodiment 34, The method of printing of any of Embodiments 1-33 or any other Embodiment, wherein the electric field strength is between about 105V / m and about 106V / m.

[0246] Embodiment 35. The method of printing of any of Embodiments 1-34 or any other Embodiment, wherein the polarizable particle emits single photons.

[0247] Embodiment 36. The method of printing of any of Embodiments 1-35 or any other Embodiment, wherein the polarizable particle is optically excitable and / or electrically excitable.

[0248] Embodiment 37. The method of printing of any of Embodiments 1-36 or any other Embodiment, further comprising applying a light source to excite the polarizable particle in the ink before applying the polarizable particle to the substrate.

[0249] Embodiment 38. The method of printing of any of Embodiments 1-37 or any other Embodiment, further comprising heating the polarizable particle in the ink.

[0250] Embodiment 39. The method of printing of any of Embodiments 1-38 or any other Embodiment, wherein heating is by illumination of the polarizable particle.

[0251] Embodiment 40. The method of printing of any of Embodiments 1 -39 or any other Embodiment, wherein applying the polarizable particle to the substrate occurs without substantially deforming a bulk meniscus at the tip of the printer nozzle.

[0252] Embodiment 41, The method of printing of any of Embodiments 1 -40 or any other Embodiment, wherein applying the polarizable particle to the substrate occurswithout reversing a curvature of a bulk meniscus at the tip of the printer nozzle relative to an air or gas interface under the meniscus.

[0253] Embodiment 42. A layer of a device fabricated by the method according to any of Embodiments 1-41.

[0254] Embodiment 43. The device of Embodiment 42, wherein the device is an optical quantum device, a nano-transistor, a sensor, a light-emitting diode, a single¬ photon source, or a CMOS circuit.

[0255] Embodiment 44. A system for printing a polarizable particle, the system including: an ink comprising a polarizable particle dispersed in an apolar solvent; and a printer, the printer including: a print head; a printer nozzle comprising a print tip. the printer nozzle being coupled to the print head and being sized and shaped to contain the ink; an electric field source; a platform sized and shaped to mount a substrate; and a controller operatively coupled to the printer, the controller including at least one processor and a computer-readable medium having computer-executable instructions stored thereon that, m response to execution by the at least one processor, cause the controller to perform operations including: applying an electric field for a hold time to the tip, thereby applying the polarizable particle to the substrate.

Claims

CLAIMSWhat is claimed is:

1. A method of printing a polarizable particle, the method comprising: applying an electric field for a hold time to a tip of a printer nozzle comprising an ink, wherein the electric field comprises an electric field strength and an electric field gradient, and wherein the ink comprises a polarizable particle dispersed in an apolar solvent; andapplying the polarizable particle to a substrate.

2. The method of printing of claim 1, wherein the polarizable particle is selected from the group consisting of a quantum dot. a nanocrystal, a metallic particle, and combination thereof.3 The method of printing of claims 1-2. wherein the quantum dot comprises a core and a shell encapsulating the core.

4. The method of printing of claims 1-3, wherein the core comprises a group IV composition, a group III-V composition, a group II-VI composition, a semi-conducting perovskite, and a chalcogenide semiconductor; andwherein the shell comprises CdS, CsPbBr3, BaTiO3, or lead zirconium titanates.

5. The method of printing of claims 1-4, wherein the shell comprises a dielectric material6 The method of printing of claims 1-5, wherein the shell comprises a semiconductor material.

7. The method of printing of claims 1-6, wherein a band gap of a material comprising the shell is larger than a bandgap of a material comprising the core.

8. The method of printing of claims 1-7. wherein the shell electronically passivates or optically passivates active defects at a core-shell interface.

9. The method of printing of claims 1-8. wherein the polarizable particle has size tunable polarizability and / or polarization.

10. The method of claims 1-9, wherein the polarizable particle has a particle dielectric constant of greater than 2.

11. The method of printing of claims 1- 10, wherein the solvent has a solvent dielectric constant that is lower than the particle dielectric constant.

12. The method of printing of claims 1-11, wherein the solvent dielectric constant is less than 10.

13. The method of printing of claims 1-12, wherein the apolar solvent is a hydrocarbon solvent.

14. The method of printing of claims 1-13, wherein the printer nozzle is coupled to a printhead.

15. The method of printing of claims 1-14, wherein applying the electric field comprises applying a voltage between a first electrode and a second electrode, wherein the voltage is between about 500 V to about 900 V,wherein the hold time is between about 0.5 seconds and about 2 seconds, wherein a fixed bias is about 1000 V, andwherein a frequency is about 1 kHz.

16. The method of printing of claims 1-15, further comprising applying a light source to excite the polarizable particle in the ink before applying the polarizable particle to the substrate.

17. The method of printing of claims 1-16, wherein applying the polarizable particle to the substrate occurs without substantially deforming a bulk meniscus at the tip of the printer nozzle.

18. A layer of a device fabricated by the method according to any of claims 1-17.

19. The device of claim 18, wherein the device is an optical quantum device, a nano-transistor, a sensor, a light-emitting diode, a single-photon source, or a CMOS circuit.

20. A system for printing a polarizable particle, the system comprising; an ink comprising a polarizable particle dispersed in an apolar solvent: and a printer, the printer comprising:a print head;a printer nozzle comprising a print tip, the printer nozzle being coupled to the print head and being sized and shaped to contain the ink;an electric field source;a platform sized and shaped to mount a substrate; anda controller operatively coupled to the printer, the controller including at least one processor and a computer-readable medium having computer-executable instructions stored thereon that, in response to execution by the at least one processor, cause the controller to perform operations including:applying an electric field for a hold time to the tip, thereby applying the polarizable particle to the substrate.

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