WO2021154895A1

WO2021154895A1 - Three-dimensional (3d) printing including upconversion photopolymerization

Info

Publication number: WO2021154895A1
Application number: PCT/US2021/015341
Authority: WO
Inventors: Peter T. Kazlas
Original assignee: Quadratic 3D, Inc.
Priority date: 2020-01-28
Filing date: 2021-01-27
Publication date: 2021-08-05

Abstract

Methods for forming a three-dimensional object are disclosed. In one aspect a method includes irradiating a volume of a photopolymerizable liquid in a container with an excitation light at the first wavelength, wherein the photopolymerizable liquid is not irradiated substantially by the second wavelength within a margin of about 1-10 mm from the internal surfaces of the container, wherein the photopolymerizable liquid comprises (i) a photopolymerizable component; (ii) upconverting nanoparticles including a sensitizer and an annihilator, the sensitizer being selected to absorb light at a first wavelength and the annihilator being selected to emit light at a second wavelength after transfer of energy from the sensitizer to the annihilator, the second wavelength being shorter than the first wavelength; and (iii) a photoinitiator that initiates polymerization of the photopolymerizable component upon excitation by light at the second wavelength. Other methods, a cartridge including the photopolymerizable liquid, and an optical printhead device are also disclosed.

Description

THREE-DIMENSIONAL (3D) PRINTING INCLUDING UPCONVERSION PHOTOPOLYMERIZATION

CLAIM OF PRIORITY

This application claims priority to U.S. Provisional Patent Application No. 62/966,945, filed on January 28, 2020, and U.S. Provisional Patent Application No. 63/003,051, filed on March 31, 2020, each of which is hereby incorporated herein by reference in its entirety for all purposes.

TECHNICAL FIELD OF THE INVENTION

The present invention relates to the technical field of 3D printing.

BRIEF SUMMARY OF THE INVENTION

In accordance with one aspect of the present invention, there is provided a method of forming a three-dimensional object, comprising: (a) providing a volume of a photopolymerizable liquid contained within a container including an optically transparent portion, the photopolymerizable liquid comprising: (i) a photopolymerizable component; (ii) upconverting nanoparticles including a sensitizer and an annihilator, the sensitizer being selected to absorb light at a first wavelength and the annihilator being selected to emit light at a second wavelength after transfer of energy from the photosensitizer to the annihilator, the second wavelength being shorter than the first wavelength; and (iii) a photoinitiator that initiates polymerization of the photopolymerizable component upon excitation by light at the second wavelength, the upconverting particles and photoinitiator being dispersed throughout the photopolymerizable component and the volume of the photopolymerizable liquid being under an inert atmosphere; and (b) irradiating the photopolymerizable liquid in the container through the at least optically transparent portion of the container with an excitation light at the first wavelength to form the three-dimensional object from the photopolymerizable liquid, wherein the photopolymerizable liquid in the container is not irradiated substantially by the second wavelength within a margin of about 1-10 mm from internal surfaces of the container, wherein the photopolymerizable liquid is maintained in an inert atmosphere during the irradiating step.

In accordance with another aspect of the present invention, there is provided a method of forming a three-dimensional object, comprising: (a) filling a container including at least an optically transparent window with a photopolymerizable liquid, the photopolymerizable liquid comprising: (i) a photopolymerizable component; (ii) upconverting nanoparticles including a sensitizer and an annihilator, the sensitizer being selected to absorb light at a first wavelength and the annihilator being selected to emit light at a second wavelength after transfer of energy from the sensitizer to the annihilator, the second wavelength being shorter than the first wavelength; and (iii) a photoinitiator that initiates polymerization of the photopolymerizable component upon excitation by light at the second wavelength; (b) closing the container including the photopolymerizable liquid to isolate the photopolymerizable liquid from a source of oxygen, and (c) irradiating the photopolymerizable liquid in the closed container through the at least optically transparent window of the container with an excitation light at the first wavelength to form the three-dimensional object from the photopolymerizable liquid, wherein the photopolymerizable liquid in the closed container is not irradiated substantially by the second wavelength within a margin of about 1-10 mm from the internal surfaces of the closed container, and wherein the photopolymerizable liquid is maintained in an inert atmosphere during the filling, closing, and irradiating steps.

In accordance with a further aspect of the present invention, there is provided a method of forming a three-dimensional object, comprising: (a) providing a volume of a photopolymerizable liquid contained within a container including an optically transparent portion, the photopolymerizable liquid comprising: (i) a photopolymerizable component; (ii) upconverting nanoparticles including a sensitizer and an annihilator, the sensitizer being selected to absorb light at a first wavelength and the annihilator being selected to emit light at a second wavelength after transfer of energy from the sensitizer to the annihilator, the second wavelength being shorter than the first wavelength; and (iii) a photoinitiator that initiates polymerization of the photopolymerizable component upon excitation by light at the second wavelength, the upconverting particles and photoinitiator being dispersed throughout the photopolymerizable component and the volume of the photopolymerizable liquid being under an inert atmosphere; and (b) irradiating the photopolymerizable liquid in the container through the at least optically transparent portion of the container with light wherein the irradiating is carried out with both: (i) an excitation light at the first wavelength, and (ii) a depletion light at a third wavelength, different from the first and second wavelengths, that inhibits the excitation of the upconverting particles, to form the three-dimensional object, wherein the photopolymerizable liquid in the container is not irradiated substantially by the second wavelength within a margin of about 1-10 mm from the internal surfaces of the container, wherein the photopolymerizable liquid is maintained in an inert atmosphere during the irradiating step.

In accordance with a further aspect of the present invention, there is provided a method of forming a three-dimensional object, comprising: (a) filling a container including at least an optically transparent window with a photopolymerizable liquid, the photopolymerizable liquid comprising: (i) a photopolymerizable component; (ii) upconverting nanoparticles including a sensitizer and an annihilator, the sensitizer being selected to absorb light at a first wavelength and the annihilator being selected to emit light at a second wavelength after transfer of energy from the sensitizer to the annihilator, the second wavelength being shorter than the first wavelength; and (iii) a photoinitiator that initiates polymerization of the photopolymerizable component upon excitation by light at the second wavelength; (b) closing the container including the photopolymerizable liquid to isolate the photopolymerizable liquid from a source of oxygen, and (c) irradiating the photopolymerizable liquid in the closed container through the at least optically transparent window of the container with light wherein the irradiating is carried out with both: (i) an excitation light at the first wavelength, and (ii) a depletion light at a third wavelength, different from the first and second wavelengths, that inhibits the excitation of the upconverting particles, to form the three-dimensional object, wherein the photopolymerizable liquid in the container is not irradiated substantially by the second wavelength within a margin of about 1-10 mm from the internal surfaces of the closed container, wherein the photopolymerizable liquid is maintained in an inert atmosphere during the filling, closing, and irradiating steps.

In accordance with yet another aspect of the present invention, there is provided a method of forming a three-dimensional object, comprising: (a) providing a volume of a photopolymerizable liquid contained within a build chamber including an optically transparent portion, the photopolymerizable liquid comprising: (i) a photopolymerizable component; (ii) upconverting nanoparticles including a center portion including a sensitizer and an annihilator, the sensitizer being selected to absorb light at a first wavelength and the annihilator being selected to emit light at a second wavelength after transfer of energy from the sensitizer to the annihilator, the second wavelength being shorter than the first wavelength; and (iii) a photoinitiator that initiates polymerization of the photopolymerizable component upon excitation by light at the second wavelength, the upconverting particles and photoinitiator being dispersed throughout the photopolymerizable component and the volume of the photopolymerizable liquid being under an inert atmosphere; (b) directing a beam of excitation light at the first wavelength through the optically transparent portion of the build chamber to a location within the volume of the photopolymerizable liquid to upconvert the excitation light to the second wavelength to polymerize the photopolymerizable liquid at the location; and (c) further directing the excitation light within the volume of photopolymerizable liquid to form the three-dimensional object from the photopolymerizable liquid, wherein the photopolymerizable liquid in the container is not irradiated substantially by the second wavelength within a margin of about 1-10 mm from the internal surfaces of the build chamber, wherein the photopolymerizable liquid is maintained in an inert atmosphere.

In accordance with a still further aspect of the present invention, there is provided a method of forming a three-dimensional object, comprising: (a) disposing a volume of a photopolymerizable liquid within a container including at least an optically transparent portion, the photopolymerizable liquid comprising: (i) a photopolymerizable component; (ii) upconverting nanoparticles including a sensitizer and an annihilator, the sensitizer being selected to absorb light at a first wavelength and the annihilator being selected to emit light at a second wavelength after transfer of energy from the sensitizer to the annihilator, the second wavelength being shorter than the first wavelength; and (iii) a photoinitiator that initiates polymerization of the photopolymerizable component upon excitation by light at the second wavelength; (b) closing the container including the photopolymerizable liquid to isolate the photopolymerizable liquid from a source of oxygen; (c) directing a beam of excitation light at the first wavelength through the optically transparent portion of the closed container to a location within the volume of the photopolymerizable liquid to upconvert the excitation light to the second wavelength to polymerize the photopolymerizable liquid at the location; and (d) further directing the excitation light within the volume of photopolymerizable liquid to form the three- dimensional object from the photopolymerizable liquid, wherein the photopolymerizable liquid in the container is not irradiated substantially by the second wavelength within a margin of about 1-10 mm from the internal surfaces of the closed container, wherein the photopolymerizable liquid is maintained in an inert atmosphere during the disposing, closing, and directing steps.

In any of the above-described methods, the excitation light can optionally be temporally and/or spatially modulated. Optionally, the intensity of the excitation light can be modulated.

In carrying out any of the above-described methods, the excitation light can be movable in relation to the container or the container can be movable in relation to the excitation light. When the excitation light is movable in relation to the container, the container is preferably stationary. The excitation light and container can also be movable in relation to each other, with one being movable, e.g., in the x,y-plane, and the other in the z-direction.

In accordance with a still further aspect of the invention, there is provided a method of forming a three-dimensional object, comprising: (a) providing a volume of a photopolymerizable liquid contained within a container including a bottom surface including an optically transparent portion, the photopolymerizable liquid comprising: (i) a photopolymerizable component; (ii) upconverting nanoparticles including a center portion including a sensitizer and an annihilator, the sensitizer being selected to absorb light at a first wavelength and the annihilator being selected to emit light at a second wavelength after transfer of energy from the sensitizer to the annihilator, the second wavelength being shorter than the first wavelength; and (iii) a photoinitiator that initiates polymerization of the photopolymerizable component upon excitation by light at the second wavelength, the upconverting particles and photoinitiator being dispersed throughout the photopolymerizable component; (b) positioning a carrier at the interface of the top surface of the photopolymerizable liquid in the container with the atmosphere in the container above the top surface; (c) directing excitation light at the first wavelength through the optically transparent portion of the container and through the volume of the photopolymerizable liquid in the container to a location at the interface to upconvert the excitation light to the second wavelength to polymerize the photopolymerizable liquid at the location to form the top surface of the three-dimensional object, and (d) capturing the top surface of the three-dimensional object with the carrier, and advancing the carrier away from the interface as formation of the three-dimensional object is continued by irradiating the photopolymerizable liquid at the top surface thereof until the three-dimensional object is formed, wherein the container is under an inert atmosphere.

Optionally, the excitation light can be temporally and/or spatially modulated. Optionally, the intensity of the excitation light can be modulated.

In accordance with yet another aspect of the present invention, there is provided a cartridge for use in a 3D printing method including upconversion, the cartridge comprising: an hermetically sealed optically transparent container including a photopolymerizable liquid that has been purged with an inert gas, the photopolymerizable liquid comprising: (i) a photopolymerizable component; (ii) upconverting nanoparticles including a sensitizer and an annihilator, the sensitizer being selected to absorb light at a first wavelength and the annihilator being selected to emit light at a second wavelength after transfer of energy from the sensitizer to the annihilator, the second wavelength being shorter than the first wavelength; and (iii) a photoinitiator that initiates polymerization of the photopolymerizable component upon excitation by light at the second wavelength.

The container preferably includes an optically flat bottom and optically flat perpendicular walls.

In accordance with still a further aspect of the present invention, there is provided an optical printhead device for delivering a beam of excitation light into a photopolymerizable material, the optical device comprising, in combination, a collimator arranged to collimate the excitation light along an optical axis, a spatial filter arranged to receive and filter the collimated excitation light, and an objective lens having an aperture with a center point and perimeter edges, the objective lens being arranged for focusing the filtered excitation light into the photopolymerizable material to form a voxel.

The foregoing, and other aspects and embodiments described herein and contemplated by this disclosure all constitute embodiments of the present invention.

It should be appreciated by those persons having ordinary skill in the art(s) to which the present invention relates that any of the features described herein in respect of any particular aspect and/or embodiment of the present invention can be combined with one or more of any of the other features of any other aspects and or embodiments of the present invention described herein, with modifications as appropriate to ensure compatibility of the combinations. Such combinations are considered to be part of the present invention contemplated by this disclosure.

It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the invention as claimed.

Other embodiments will be apparent to those skilled in the art from consideration of the description and drawings, from the claims, and from practice of the invention disclosed herein.

BRIEF DESCRIPTION OF THE DRAWINGS

In the drawings,

FIGS. 1A & IB depict diagrams of examples of embodiments of system configurations for use with various aspects and embodiments of the methods of the invention.

FIG. 2 depicts a diagram of an example of an embodiment of a system configuration for use with various aspects and embodiments of the methods of the invention.

FIG. 3 depicts a diagram of an example of an embodiment of a system configuration for use with various aspects and embodiments of the methods of the invention.

FIGS. 4A & 4B depict diagrams of examples of an excitation system for use with various aspects and embodiments of the methods of the invention; the depicted system includes an example of an embodiment of an optical printhead device in accordance with an aspect of the present invention.

FIGS. 5 A & 5B depict diagrams of example of an embodiment of one of the methods of the present invention.

The attached figures are simplified representations presented for purposes of illustration only; the actual structures may differ in numerous respects, particularly including the relative scale of the articles depicted and aspects thereof.

For a better understanding to the present invention, together with other advantages and capabilities thereof, reference is made to the following disclosure and appended claims in connection with the above-described drawings. DETAILED DESCRIPTION OF THE INVENTION

Various aspects and embodiments of the present inventions are further described in the following detailed description.

In accordance with one aspect of the present invention, there is provided a method of forming a three-dimensional object, comprising: (a) providing a volume of a photopolymerizable liquid contained within a container including an optically transparent portion, the photopolymerizable liquid comprising: (i) a photopolymerizable component; (ii) upconverting nanoparticles including a sensitizer and an annihilator, the sensitizer being selected to absorb light at a first wavelength and the annihilator being selected to emit light at a second wavelength after transfer of energy from the sensitizer to the annihilator, the second wavelength being shorter than the first wavelength; and (iii) a photoinitiator that initiates polymerization of the photopolymerizable component upon excitation by light at the second wavelength, the upconverting particles and photoinitiator being dispersed throughout the photopolymerizable component and the volume of the photopolymerizable liquid being under an inert atmosphere; and (b) irradiating the photopolymerizable liquid in the container through the at least optically transparent portion of the container with an excitation light at the first wavelength to form the three-dimensional object from the photopolymerizable liquid, wherein the photopolymerizable liquid in the container is not irradiated substantially by the second wavelength within a margin of about 1-10 mm from the internal surfaces of the container, wherein the photopolymerizable liquid is maintained in an inert atmosphere during the irradiating step.

Spatially modulated excitation light can be created by known spatial modulation techniques, including, for example, a liquid crystal display (LCD) or a digital micromirror display (DMD), liquid-crystal-on-silicon (LCOS), vertical-cavity laser (VCL) array or a microLED array. Other known spatial modulation techniques can be readily identified by those skilled in the art.

In carrying out the method, the excitation light can be movable in relation to the container or the container can be movable in relation to the excitation light. When the excitation light is movable in relation to the container, the container is preferably stationary. The excitation light and container can also both be movable in relation to each other, with one being movable, e.g., in the x,y-plane, and the other in the z-direction. In carrying out the method, the photopolymerizable liquid can be selectively irradiated with the excitation light at the first wavelength to induce photopolymerization within the volume of the photopolymerizable liquid to form a three-dimensional object. The photopolymerizable liquid can be selectively irradiated by controlled irradiation of the photopolymerizable liquid to obtain confined photopolymerization in three-dimensional regions thereof to form the desired three- dimensional object.

Preferably, the source of the excitation light is a light source positioned external to the photopolymerizable liquid.

The light source is preferably selected based on the absorption characteristics of the sensitizer.

The present method can facilitate printing three-dimensional objects in a volume of photopolymerizable liquid at a distance or depth of greater than 1 cm from the interface of the photopolymerizable fluid and the inside surface of the container in which it is disposed.

The irradiation step of the method can include application of continuous excitation light.

The irradiation step of the method can include application of intermittent excitation light. Intermittent excitation can include random on and off application of light or periodic application of light. Examples of periodic application of light includes pulsing, such as provided by a pulsed laser.

The irradiation step of the method can include the application of a combination of both continuous excitation light and intermittent light, including, for example, an irradiation step that includes the application of intermittent excitation light that is preceded or followed by irradiation with continuous light.

Suitable wavelengths as the excitation wavelength include 400-800 nm.

Preferably, the first and/or second wavelengths are in the visible range. Examples of wavelengths in the visible range include wavelengths in a range from about 400 nm to about 700 nm.

Other wavelengths may be determined to be useful based on the characteristics of the sensitizer, annihilator, and/or photoinitiator. The photopolymerizable liquid, photopolymerizable component, upconverting nanoparticles, sensitizer, annihilator, and photoinitiator, and excitation source are discussed in more detail below.

Spatially modulated excitation light can be created by known spatial modulation techniques, including, for example, a liquid crystal display (LCD) or a digital micromirror display (DMD), liquid-crystal-on-silicon (LCOS), vertical-cavity laser (VCL) array or a microLED array. Other known spatial modulation techniques can be readily identifiable by those skilled in the art.

In carrying out the method, the excitation light can be movable in relation to the container or the container can be movable in relation to the excitation light. When the excitation light is movable in relation to the container, the container is preferably stationary. The excitation light and container can also both be movable in relation to each other, with one being movable, e.g., in the x,y-plane, and the other in the z-direction.

In carrying out the method, the photopolymerizable liquid can be selectively irradiated with the excitation light at the first wavelength to induce photopolymerization within the volume of the photopolymerizable liquid to form a three-dimensional object. The photopolymerizable liquid can be selectively irradiated by controlled irradiation of the photopolymerizable liquid to obtain confined photopolymerization in three-dimensional regions thereof to form the desired three- dimensional object.

Examples of suitable wavelengths as the excitation wavelength include 400-800 nm.

Other wavelengths may be determined to be useful based on the characteristics of the sensitizer, annihilator, and/or photoinitiator.

The photopolymerizable liquid, photopolymerizable component, upconverting nanoparticles, sensitizer, annihilator, and photoinitiator, and excitation source are discussed in more detail below.

FIG. 1A depicts a diagram of an example of an embodiment of a system configuration for

3D printing for use with various aspects and embodiments of methods of the invention. The example of the system configuration shown FIG. 1A includes a container 2 (depicted in this example as a closed container) including a photopolymerizable liquid 4 with excitation light 6 at the first wavelength being irradiated into the volume of the photopolymerizable liquid within the container. In the depicted example the excitation light is projected into the volume from an optical subsystem 8 located above the container. As depicted, the three-dimensional object 9 formed within the volume of photopolymerizable liquid in the container is not in contact with any internal surfaces of the closed container and is suspended within the volume. While only one optical system is shown in FIG. 1A, optionally, more than one optical system, each generating a separate excitation light beam can be used. (The x, y, z orientation for each of the depicted optical system and container are also shown.)

FIG. IB depicts a diagram of an example of another embodiment of a system configuration for 3D printing for use with various aspects and embodiments of methods of the invention. The example of the system configuration shown FIG. IB includes a container 12 (depicted in this example as a closed container) of a photopolymerizable liquid 14 with an optical subsystem 18 irradiating more than one beam of excitation light 16 at the first wavelength into the volume of the photopolymerizable liquid within the container. In the depicted example the excitation light is projected into the volume as two beams from an optical system located below the container. As depicted in FIG. IB, the three-dimensional object 19 formed within the volume of photopolymerizable liquid in the container is not in contact with any internal surfaces of the closed container and is suspended within the volume. While only one optical system is shown in FIG. IB, optionally, more than one optical system, each generating a separate excitation light beam can be used. (The x, y, z orientation for each of the depicted optical system and container are also shown.)

As mentioned elsewhere herein, in carrying out the methods of the invention, the excitation light can be movable in relation to the container. FIG. 2 depicts a diagram of an example of an embodiment of a system configuration for 3D printing for use with various aspects and embodiments of methods of the invention which includes one or more excitation systems. In the figure, the depicted excitation system comprises a projection system. The example of the system configuration depicted in FIG. 2 shows a system including three projection systems 21, 22, 23 (labeled “Proj Sys” in the drawing) that are separately movable in relation to the container which is preferably stationary. A projection system preferably includes optics. However, a projection system without optics can also be used. FIG. 2 shows a container 25 (depicted in this example as a closed container) of a photopolymerizable liquid 26 with three excitation systems 21, 22, 23, each generating excitation light, respectively 27, 28, 29, at the first wavelength into the volume of the photopolymerizable liquid within the container. In the depicted example the excitation light is projected into the volume from each of the excitation systems which are movable in relation to the container. As shown, the excitation systems are located below the container. The excitation systems can alternatively be positioned above or adjacent to a side of the container. Additionally, while the figure depicts a single container, additional containers can optionally be included. While three excitation systems are shown in FIG. 2, optionally, one, two, or more excitation systems, each generating a separate excitation light beam, can be used. (The x, y, z orientation for the system configuration is also shown.)

As also mentioned elsewhere herein, in carrying out the methods of the invention, the container including a volume of the photopolymerizable liquid can be movable in relation to the excitation system. In the figure, the depicted excitation system comprises a projection system. FIG. 3 depicts a diagram of an example of an embodiment of a system configuration for 3D printing for use with various aspects and embodiments of methods of the invention which includes one or more containers (depicted in this example as a closed container) that are separately movable in relation to one or more excitation systems (labeled “Proj Sys” in the drawing), which are preferably stationary. The example of the system configuration depicted in FIG. 3 shows a system including three containers 31, 32, 33 (depicted in this example as closed containers) including a photopolymerizable liquid 34, 35, 36 with three excitation systems 37, 38, 39 , each generating excitation light 40, 41, 42 at the first wavelength into the volume of the photopolymerizable liquid within one container which is aligned therewith. In the depicted example the excitation light is projected from each of the excitation systems into the volume included the container aligned therewith. Each container is individually movable in relation to the excitation system with which it is aligned for being irradiated to vary the location in the volume that is irradiated to photopolymerize the photopolymerizable liquid at that position within the volume. As shown, the excitation systems are located below the containers. The excitation systems can alternatively be positioned above or adjacent to the sides of the containers. Additionally, while the figure depicts three containers, one, two, or more additional containers can optionally be included. While three excitation systems are shown in FIG. 3, optionally, one, two, or more excitation systems, each generating a separate excitation light beam, can be used.

In any of the examples depicted in FIGS. 1A-3, at least the portion of the container facing an excitation system is optically transparent, and preferably also optically flat.

In accordance with still a further aspect of the present invention, there is provided an optical printhead device for delivering a beam of excitation light into a photopolymerizable material, the optical printhead device comprising, in combination, a collimator arranged to collimate the excitation light along an optical axis, a spatial filter arranged to receive and filter the collimated excitation light, and an objective lens having an aperture with a center point and perimeter edges, the objective lens being arranged for focusing the filtered excitation light into the photopolymerizable material to form a voxel. A voxel is a term used in 3d printing to refer to a 3- dimensional pixel.

FIGS. 4 A & 4B depict diagrams of examples of an excitation system for 3D printing for use with various embodiments of the methods of the invention. The depicted examples include a printhead 141 (also referred to herein as an optical printhead device or an x,y,z controlled printhead) disposed above a container 142 including a photopolymerizable liquid 143. The printhead is controllable in the x, y, and z directions for printing in an x,y plane (e.g., parallel to the bottom of the container) within the volume of the photopolymerizable liquid and also in the z-direction (perpendicular to the x,y-plane).

The depicted printhead 141 includes a collimator 144, spatial filter 145, and objective 146. The spatial filter modifies the beam of light before it enters the objective. As an example, the spatial filter can block the light that travels along the optical axis (shown in FIG. 4B) exiting the collimator near the center of the objective lens and only allow light to pass along the edges of the objective’s aperture. In this way, light can be better concentrated at the focal point of the objective improving the axial resolution (z-axis). The spatial filter can act on the two-dimensional wavefront exiting the collimator by modifying the amplitude and/or phase of the wavefront. The spatial filter can be either static (as example, an etched chrome or aluminum mask) or dynamic (as an example, a spatial light modulator). The printhead is in connection by an optical fiber 147 with an excitation source 148. FIGS. 4A and 4B depict different configurations of the optical fiber connection. By way of example, the figures depict a lOOmW laser that emits excitation light 149 with a 532 nm wavelength, which is used with a sensitizer, e.g., a metalloporphyrin, that absorbs 532 nm light.

With a photopolymerizable liquid that includes a sensitizer that absorbs light with a different wavelength, a laser that emits at that different wavelength would be preferred). . (The x, y, z orientation for the system configuration is also shown in each of FIGS. 4 A & 4B.) FIG. 4B also indicates the optical axis 150 for the depicted example.

Optionally, at least one of the excitation light and depletion light can be temporally and/or spatially modulated. Optionally, the intensity of at least one of the excitation light and depletion light can be modulated.

Spatially modulated excitation light and or depletion light can be created by known spatial light modulation techniques, including, for example, a liquid crystal display (LCD) or a digital micromirror display (DMD), liquid-crystal-on-silicon (LCOS), vertical-cavity laser (VCL) array or a microLED array. Other known spatial modulation techniques can be readily identifiable by those skilled in the art.

In carrying out the method, the excitation and depletion lights can be movable in relation to the container or the container can be movable in relation to the excitation and depletion lights.

When the excitation and depletion lights are movable in relation to the container, the container is preferably stationary. The excitation and depletion lights and the container can also both be movable in relation to each other, e.g., one movable in the x,y-plane, and the other movable in the z- direction. Optionally, the excitation and depletion light may be separately movable.

Preferably, the source of the excitation light is a light source positioned external to the photopolymerizable liquid. The light source is preferably selected based on the absorption characteristics of the sensitizer.

Optionally, when the excitation light is both spatially and temporally modulated, the depletion light can be applied as: (i) uniform flood exposure over time, (ii) uniform flood exposure modulated in intensity over time; (iii) uniform intensity exposure spatially modulated over time; or (iv) spatially and temporally modulated over time.

Optionally, when the excitation light is (i) uniform flood exposure over time or (ii) uniform flood exposure modulated in intensity over time, the depletion light can be both spatially and temporally modulated.

The irradiation step of the method can include application of continuous depletion light.

The irradiation step of the method can include application of intermittent depletion light. Intermittent depletion can include random on and off application of depletion light or periodic application of depletion light. Examples of periodic application of light includes pulsing.

The irradiation step of the method can include the application of a combination of both continuous depletion light and intermittent depletion light, including, for example, an irradiation step that includes the application of intermittent depletion light that is preceded or followed by irradiation with continuous depletion light.

Examples of suitable wavelengths as the excitation wavelength include 400-800 nm. Preferably, the first and/or second wavelengths are in the visible range. Examples of wavelengths in the visible range include wavelengths in a range from about 400 nm to about 700 nm.

Examples of suitable wavelengths for the third wavelength include wavelengths in a range of 400-700 nm up to 1300-1600 nm.

A patterned exposure of excitation and depletion light can be created by a liquid crystal display (LCD), a digital micromirror display (DMD), or other known techniques identifiable by the skilled artisan.

In accordance with a further aspect of the present invention, there is provided a method of forming a three-dimensional object, comprising: (a) filling a container including at least an optically transparent window with a photopolymerizable liquid, the photopolymerizable liquid comprising: (i) a photopolymerizable component; (ii) upconverting nanoparticles including a sensitizer and an annihilator, the sensitizer being selected to absorb light at a first wavelength and the annihilator being selected to emit light at a second wavelength after transfer of energy from the sensitizer to the annihilator, the second wavelength being shorter than the first wavelength; and (iii) a photoinitiator that initiates polymerization of the photopolymerizable component upon excitation by light at the second wavelength; (b) closing the container including the photopolymerizable liquid to isolate the photopolymerizable liquid from a source of oxygen; and (c) irradiating the photopolymerizable liquid in the closed container through the at least optically transparent window of the container with light wherein the irradiating is carried out with both: (i) an excitation light at the first wavelength, and (ii) a depletion light at a third wavelength, different from the first and second wavelengths, that inhibits the excitation of the upconverting particles, to form the three-dimensional object, wherein the photopolymerizable liquid in the container is not irradiated substantially by the second wavelength within a margin of about 1-10 mm from the internal surfaces of the closed container, wherein the photopolymerizable liquid is maintained in an inert atmosphere during the filling, closing, and irradiating steps. Optionally, at least one of the excitation light and depletion light can be temporally and/or spatially modulated. Optionally, the intensity of at least one of the excitation light and depletion light can be modulated.

Optionally, when the excitation light is both spatially and temporally modulated, the depletion light can be applied as: (i) uniform flood exposure over time, (ii) uniform flood exposure modulated in intensity over time; (iii) uniform intensity exposure spatially modulated over time; or (iv) spatially and temporally modulated over time. Optionally, when the excitation light is (i) uniform flood exposure over time or (ii) uniform flood exposure modulated in intensity over time, the depletion light can be both spatially and temporally modulated.

In carrying out the method, the excitation light can be movable in relation to the build chamber or the build chamber can be movable in relation to the excitation light. When the excitation light is movable in relation to the build chamber, the build chamber is preferably stationary. The excitation light and build chamber can also both be movable in relation to each other, with one being movable, e.g., in the x,y-plane, and the other in the z-direction.

The present method can facilitate printing three-dimensional objects in a volume of photopolymerizable liquid at a distance or depth of greater than 1 cm from the interface of the photopolymerizable fluid and the inside surface of the build chamber in which it is disposed.

Preferably, the first and/or second wavelengths are in the visible range. Examples of wavelengths in the visible range include wavelengths in a range from about 400 nm to about 700 nm. Other wavelengths may be determined to be useful based on the characteristics of the sensitizer, annihilator, and/or photoinitiator.

In accordance with a still further aspect of the present invention, there is provided a method of forming a three-dimensional object, comprising: (a) disposing a volume of a photopolymerizable liquid within a container including at least an optically transparent portion, the photopolymerizable liquid comprising: (i) a photopolymerizable component; (ii) upconverting nanoparticles including a sensitizer and an annihilator comprising, the sensitizer being selected to absorb light at a first wavelength and the annihilator being selected to emit light at a second wavelength after transfer of energy from the sensitizer to the annihilator, the second wavelength being shorter than the first wavelength; and (iii) a photoinitiator that initiates polymerization of the photopolymerizable component upon excitation by light at the second wavelength; (b) closing the container including the photopolymerizable liquid to isolate the photopolymerizable liquid from a source of oxygen; (c) directing a beam of excitation light at the first wavelength through the optically transparent portion of the closed container to a location within the volume of the photopolymerizable liquid to upconvert the excitation light to the second wavelength to polymerize the photopolymerizable liquid at the location; and (d) further directing the excitation light within the volume of photopolymerizable liquid to form the three-dimensional object from the photopolymerizable liquid, wherein the photopolymerizable liquid in the container is not irradiated substantially by the second wavelength within a margin of about 1-10 mm from the internal surfaces of the closed container, wherein the photopolymerizable liquid is maintained in an inert atmosphere during the disposing, closing, and directing steps.

Optionally, the excitation light can be temporally and or spatially modulated. Optionally, the intensity of the excitation light can be modulated.

In accordance with a still further aspect of the invention, there is provided a method of forming a three-dimensional object, comprising: (a) providing a volume of a photopolymerizable liquid contained within a container including a bottom surface including an optically transparent portion, the photopolymerizable liquid comprising: (i) a photopolymerizable component; (ii) upconverting nanoparticles including a center portion including a sensitizer and an annihilator, the sensitizer being selected to absorb light at a first wavelength and the annihilator being selected to emit light at a second wavelength after transfer of energy from the sensitizer to the annihilator, the second wavelength being shorter than the first wavelength; and (iii) a photoinitiator that initiates polymerization of the photopolymerizable component upon excitation by light at the second wavelength, the upconverting particles and photoinitiator being dispersed throughout the photopolymerizable component; (b) positioning a carrier at the interface of the top surface of the photopolymerizable liquid in the container with the atmosphere in the container above the top surface; (c) directing excitation light at the first wavelength through the optically transparent portion of the container and through the volume of the photopolymerizable liquid in the container to a location at the interface to upconvert the excitation light to the second wavelength to polymerize the photopolymerizable liquid at the location to form the top surface of the three-dimensional object; and (d) capturing the top surface of the three-dimensional object with the carrier, and advancing the carrier away from the interface as formation of the three-dimensional object is continued by irradiating the photopolymerizable liquid at the top surface thereof until the three-dimensional object is formed, wherein the container is under an inert atmosphere.

It is believed that the method of this aspect of the invention can improve z-axis or depth control during printing.

Optionally the carrier is advanced by a mechanism that lifts it from above or one that pushes it up from below.

During printing the optical system maintains focus at the print location.

Optionally, a light absorbing layer of liquid can float on the top surface of the photopolymerizable liquid to suppress unwanted reflections at the surface at which printing occurs. By way of example, an absorbing layer can be a black layer or can be comprised of a material strongly absorbing at the excitation wavelength (e.g., nanomaterials, microspheres, or dye molecules that are strongly absorbing at the excitation wavelength that are dispersed in a fluid, preferably with a density lighter than the photopolymerizable liquid or immiscible therein).

As the three-dimensional object is formed at the top surface, the level of the photopolymerizable liquid is preferably maintained constant by feeding additional amounts thereof into the container.

FIGS. 5 A and 5B depict diagrams of an example of an embodiment of this method at different stages of formation of a three-dimensional object.

FIGS. 5 A and 5B depict a system including a container 153 including the photopolymerizable liquid 154 with an optical subsystem 155 positioned below the bottom surface of the container. At least a portion of the bottom of the container is optically transparent.

Preferably the bottom surface is also optically flat. A carrier advancing the three-dimensional object away from the top surface of the photopolymerizable liquid is also shown. In FIG. 5A, the optical system irradiates the top surface of the photopolymerizable liquid with two beams 156 of excitation light. In FIG. 5B, at a later stage of printing the three-dimensional object, the optical system irradiates the top surface of the photopolymerizable liquid with one beam 156 of excitation light, based on the excitation needs at that stage of the printing process.

Optionally, in carrying out this method, multiple projection illumination of the surface of the photopolymerizable liquid can be used. Optionally, multiple projection illumination of the volume in the container or build chamber can be used in connection with the other methods described herein.

Examples of excitation systems for use in this method and other methods described herein include, but are not limited to, laser projection systems, a liquid crystal display (LCD), a digital micromirror display (DMD), a micro-LED array, and a vertical cavity laser (VCL), scanning laser systems, liquid-crystal-on-silicon (LCOS), etc.

Optionally, portions of the cartridge that are not positioned or intended to provide excitation light access to the contents of the cartridge when used for printing are not optically transparent.

The photopolymerizable liquid, photopolymerizable component, upconverting nanoparticles, sensitizer, annihilator, and photoinitiator are discussed in more detail below.

A preferred photopolymerizable liquid for inclusion in a method or cartridge in accordance with the various aspects and embodiments of the present invention comprises a photopolymerizable liquid comprising: (i) a photopolymerizable component; (ii) upconverting nanoparticles including a sensitizer and an annihilator, the sensitizer being selected to absorb light at a first wavelength and the annihilator being selected to emit light at a second wavelength after transfer of energy from the sensitizer to the annihilator, the second wavelength being shorter than the first wavelength; and (iii) a photoinitiator that initiates polymerization of the photopolymerizable component upon excitation by light at the second wavelength.

The photopolymerizable component included in the photopolymerizable liquid may be any photopolymerizable resin or monomer suitable for the mechanism to be used to trigger the polymerization (radical mechanism, ionic mechanism, etc.). Examples of photopolymerizable components that may be included in the photopolymerizable liquid include, for example, without limitation, monomers, oligomers or polymers which can be polymerized by the radical route by addition or crosslinking mechanisms such as: acrylated monomers, such as acrylates, polyacrylates, methacrylates, or -acrylated oligomers such as unsaturated amides, or -methacrylated polymers, polymers which have a hydrocarbyl skeleton and pendant peptide groups with a functionality which can be polymerized by free radicals, or vinyl compounds such as styrenes, diallyl phthalate, divinyl succinate, divinyl adipate and divinyl phthalate, or -mixtures of several of the above monomers, oligomers or polymers, cationically polymerizable monomers and oligomers and cationically crosslinkable polymers, for example epoxy resins such as monomeric epoxies and polymeric epoxides having one or more epoxy groups, vinyl ethers, cyanate esters, etc. and mixtures of several of these compounds.

Additional information concerning photopolymerization resins and monomers that may be useful can be found in in WO2019/025717 of Baldeck, et ah, published February 7, 2019, International Application No. Application No. PCT/US2019/063629, of Congreve, et al., filed November 27, 2019, each of which is hereby incorporated herein by reference in its entirety.

The photoinitiator can be readily selected by one of ordinary skill in the art, taking into account its suitability for the mechanism to be used to initiate polymerization as well as its suitability for and/or compatibility with the resin to be polymerized. Information concerning photoinitiators that may be useful can be found in WO2019/025717 of Baldeck, et al., published February 7, 2019, and International Application No. Application No. PCT/US2019/063629, of Congreve, et al., filed November 27, 2019, each of which is hereby incorporated herein by reference in its entirety.

Upconverting nanoparticles preferably have an average particle size less than the wavelength of the exciting light. Examples of preferred average particle sizes are less than 100 nm, less than 50 nm, less than 30 nm, less than 20 nm, although still larger, or smaller, nanoparticles can also be used. Most preferably, the upconverting nanoparticles have an average particle size creates no appreciable light scattering.

Examples of materials for use as sensitizers and annihilators are described in International Application No. PCT/US2019/063629, of Congreve, et al., filed November 27, 2019, S. Sanders, et al., “Photon Upconversion in Aqueous Nanodroplets”, J. Amer. Chem. Soc. 2019, 141, 9180-9184, and Beauti, Sumar, Abstract entitled “Search for New Chromophore Pairs for Triplet-Triplet Annihilation Upconversion” ISEF Projects Database, Finalist Abstract (2017), available at https://abstracts.societyforscience.org, each of the foregoing being hereby incorporated herein by reference in its entirety. WO2019/025717 of Baldeck, et al., published February 7, 2019, and International Application No. PCT/US2019/063629, of Congreve, et al., filed November 27, 2019 also provide information that may be useful concerning the concentration of the upconverting nanoparticles and the concentrations of the sensitizer and annihilator in the photopolymerizable liquid.

An annihilator can comprise molecules capable of receiving a triplet exciton from a molecule of the sensitizer through triplet-triplet energy transfer, undergo triplet fusion with another annihilator molecule triplet to generate a higher energy singlet that emits light at a second wavelength to excite the photoinitiator to initiate polymerization of the photopolymerizable component. Examples of annihilators include, but are not limited to, polycyclic aromatic hydrocarbons, e.g. anthracene, anthracene derivatives (e.g., diphenyl anthracene (DP A) 9,10- dimethylanthracene (DMA), 9,10-dipolyanthracene (DTA), 2-chloro-9,10-diphtylanthracene (DTACI, 2-carbonitrile-9, 10-dip tetrylanthracene (DTACN), 2-carbonitrile-9,10- dinaphthylanthracene (DNACN), 2-methyl-9,10-dinaphthylanthracene (DNAMe), 2-chloro-9,10- dinaphthylanthracene (DNACI), 9 , lObis (phenylethynyl) anthracene (BPEA), 2-chloro-9,10bis (phenylethynyl) anthracene (2CBPEA), 5,6,ll,12-tetraphenylnaphthacene(rubrene), pyrene and or perylene (e.g., tetra-t-butyl perylene (TTBP). The above anthracene derivatives may also be functionalized with a halogen. For example, DPA may be further functionalized with a halogen (e.g., fluorine, chlorine, bromine, iodine). Fluorescent organic dyes can be preferred.

A sensitizer can comprise at least one molecule capable of passing energy from a singlet state to a triplet state when it absorbs the photonic energy of excitation at the first wavelength. Examples of sensitizers include, but are not limited to, metalloporphyrins (e.g., palladium tetraphenyl tetrabutyl porphyrin (PdTPTBP), platinum octaethyl porphyrin (PtOEP), octaethyl- porphyrin palladium (PdOEP), paladium-tetratolylporphyrin (PdTPP), palladium-meso- tetraphenyltetrabenzoporphyrin 1 (PdPh4TBP), l,4,8,ll,15,18,22,25octabutoxyphthalocyanine (PdPc (OBu)), 2,3-butanedione (or diacetyl), or a combination of several of the above molecules,).

The sensitizer preferably absorbs the excitation light at the first wavelength in order to make maximum use of the energy thereof.

A consideration in selecting a photosensitizer/annihilator pair may include the compatibility of the pair with the photoinitiator being used.

Preferably upconverting nanoparticles include a core portion that includes the sensitizer and the annihilator in a liquid (e.g., oleic acid) and an encapsulating coating or a shell (e.g., silica) around the outer surface of the core portion. Examples of preferred upconverting nanoparticles include nanocapsules described in International Application No. PCT/US2019/063629, of Congreve, et al., filed November 27, 2019 which is hereby incorporated herein by reference in its entirety. Other information concerning nanocapsules that may be useful includes International Publication No. WO2015/059179, of Landfester, et al., which published April 30, 2015 and S. Sanders, et al., “Photon Upconversion in Aqueous Nanodroplets”, J. Amer. Chem. Soc. 2019, 141, 9180-9184, each of which is hereby incorporated herein by reference in its entirety.

Upconverting nanoparticles can further include surface functionalization at the surface thereof for facilitating distribution of the nanoparticles in the photopolymerization component. Surfactants and other materials useful for surface functionalization are commercially available. Preferred examples of such materials include, but are not limited to, polyethylene glycols.

The photopolymerizable liquid included in the methods and cartridge described herein may have any suitable viscosity. For example, a photopolymerizable liquid can have a viscosity greater than 1 centipoise, greater than 100 centipoise, greater than 1,000 centipoise, greater than 5,000 centipoise. For printing a three-dimensional object that is floating within the volume in the container or build chamber, a higher viscosity can be desirable for keeping the object that is being printed suspended. A photopolymerizable liquid having a viscosity of about 1,000 centipoise or higher, 2,000 centipoise or higher, 4,000 centipoise, 5,000 centipoise, or higher, or even higher can be preferred in this regard. Preferably the photopolymerizable liquid has the desired viscosity under the conditions in which printing is carried out.

Examples of excitation sources of the excitation light for use in the methods described herein include laser diodes, such as those available commercially, light emitting diodes, DMD projection systems, micro-LED arrays, vertical cavity lasers (VCLs), filtered white light. In some embodiments, the excitation radiation source (e.g., the light source) is a light-emitting diode (LED).

The photopolymerizable liquid may further include additional additives. Examples of such additives include, but are not limited to, thixotropes, oxygen scavengers, etc. WO2019/025717 of Baldeck, et ah, published February 7, 2019 provides information that may be useful regarding antioxidant additives.

Other information that may be useful with the present invention is U.S. Patent Application No. 62/9211125 of Congreve, et ah, filed October 4, 2019.

The methods disclosed herein can also include the use commercially available optical projection and filtering techniques that can assist in providing a very narrow depth of focus or systems that employ two or more optical projection methods at once.

In the methods described herein, the container or build chamber can be rotated to expose from another side from another angle. This can be of assistance in patterning object volumes or surfaces more accurately or it can be used as a means of providing multiple exposure of a given feature from different angles in a tomographic way. The excitation source (or projected image or wavefront) is preferably positioned orthogonal to the container’s or build chamber’s surface to minimize light loss and distortion. (For example, for a cylinder this would be orthogonal to the rotation axis; for a cube this would be true for four angles.)

As discussed herein, containers or build regions included in methods or cartridges in accordance with the present invention include at least a portion that is optically transparent so that photopolymerizable liquid included therein is accessible by excitation light. Preferably, the entire container is optically transparent.

Optically transparent portions of a container or build regions included in methods or cartridges in accordance with the present invention can be constructed from a material comprising, for example, but not limited to, glass, quartz, fluoropolymers (e.g., Teflon FEP, Teflon AF, Teflon PFA), cyclic olefin copolymers, polymethyl methacrylate (PMMA), polynorbornene, sapphire, or transparent ceramic.

Examples of container shapes include, but are not limited to, a cylindrical container having a circular or oval cross-section, a container having straight sides with a polygonal cross-section or a rectangular or square cross-section.

A closed container for use in the systems and methods of the present invention can be a one- piece unit or can be constructed from two or more pieces.

The container can be an integral part of the build region of a printing system or can be a removable component. A removable container can be preferred for isolating printed three- dimensional objects from remaining unpolymerized liquid in the container.

Preferably the photopolymerizable liquid is degassed, purged, or sparged with an inert gas before or after being introduced into the container and is maintained under inert conditions, e.g., under an inert atmosphere, while in the container which is preferably closed during printing. This can prevent introduction of oxygen into the container while the three-dimensional object is being printed or formed. Examples of inert gases include, but are not limited to, argon, nitrogen, etc.

Preferably the container is sealed or otherwise closed in an air-tight manner to prevent introduction of oxygen into the container during printing. The seal or other closing techniques that may be used are preferably not permanent so at least that the printed objects and unpolymerized material can be removed from the container after printing. Methods of part removal can include piercing the container, breaking it and/or flushing or rinsing the container it with a solvent. The container and uncured resin can be recycled or discarded.

Optionally, one or more filters can be added to at least a surface of any optically transparent portions of the container to block undesired light, e.g., with a wavelength the same as the upconverted light (e.g., light with the second wavelength), to prevent unintentional curing.

An example of a system for use with methods in accordance with various aspects or embodiments of the present invention can include (a) an excitation source and (b) a container including a photopolymerizable liquid. Optionally, a system can further include any or more of optics, a spatial light modulator, projection optics, and an x,y,z-stage or other movement device. Another example of a system for use with methods in accordance with various aspects or embodiments of the present invention can include (a) an excitation source and optics, (b) a spatial light modulator (e.g., DMD, LCOS, LCD), (c) projection optics, (d) a container including a photopolymerizable liquid, (e) an x,y,z-stage or other movement device to more either the projection system (which can include above components (a)-(c) or the container. Other features of a system can optionally be further included. Examples of other movement devices include, but are not limited to, a track system, pistons, pneumatic movement device, a fast submicron stage, etc.

Examples of excitation or illumination sources include, but are not limited to, LEDS, laser, OLEDS, microLED, VCLs, an array of elements, etc.

In the methods described herein, the power per unit area of excitation light directed into the volume of photopolymerizable liquid to at least initiate polymerization to occur may be, without limitation, less than 1000 W/cm², less than 500 W/cm², less than 100 W/cm², less than 50 W/cm², less than 10 W/cm², less than 5 W/cm², less than 1 W/cm², less than 500 mW/cm², less than 100 mW/cm², etc. (Power per unit area may also be referred to herein as power density or intensity or irradiance.)

Most preferably, a quadratic or higher relationship exists between the power of the excitation light and emission from the annihilator.

Preferably the irradiation power of the excitation light is monitored and controlled by a light controller in hardware and or software. It is also advantageous to monitor the spatial distribution of light in the photopolymerizable liquid by means of a camera or offline (no photopolymerizable liquid or container present) by means of a laser beam or light profiler or irradiance meter or photodetector (with pinhole) that measures power density as a function of x,y and z.

As described above, methods in accordance with various aspects or embodiments of the present invention and systems used in connection therewith may employ different wavelength illumination and projection schemes and may contain more than one printing subsystem. Various spatial light modulators can used to modulate the amplitude, phase, or combination to create the desired light field in the photopolymerizable liquid. Preferably imaging light fields in the photopolymerizable liquid are formed at sharp angles so that depth of focus is small.

Methods in accordance with various aspects or embodiments of the present invention and systems used in connection therewith may include an optical system including a dc-block filter. Such filters can filter in the Fourier plane to reduce unwanted axial light. Additional information that may be helpful in this regard can be found in “Introduction to Fourier Optics”, Joseph W. Goodman McGraw-Hill, New York 1968, relevant portions of which are hereby incorporated herein by reference. For example, such filters may be employed in a 4F imaging system for example where the DC component is spatially filter by an inverse aperture in the Fourier plane of the system. This can be accomplished by a patterned chrome mask (a circle) that is place on the optical axis.

As mentioned above, the projection optics subsystem, projection system, etc. and/or the container including the photopolymerizable liquid can optionally be moved during printing. Movement can be in a stepped fashion (3D volume print then index in x,y, or z) or it can move continuously during printing. The photopolymerizable liquid does not need to be stirred during printing and the photopolymerizable liquid resin can optionally remain stationary during printing. This allows use to high viscosity resins. After printing the viscosity of the resin can be reduced, for example, by heating or other known techniques.

As mentioned herein, a container is preferably optically clear and optically flat so there are no distortions in the optical path.

When used as a characteristics of a portion of a container or build chamber or cartridge, “optically transparent” refers to having high optical transmission to the wavelength of light being used, and “optically flat” refers to being non-distorting (e.g., optical wavefronts entering the portion of the container or build chamber remain largely unaffected).

Other information concerning optical systems that may useful in connection with the various aspects of the present inventions includes Texas Instruments Application Report DLPA022- July 2010 entitled “DLP™ System Optics”; Texas Instruments “TI DL^R Technology for 3D Printing - Design scalable high-speed stereolithograpy [sic] systems using TI DLP technology” 2016; Texas Instruments “DLP65000.65 1018p MVSP Type A DMD”, DLP6500, DLPS040A-October 2014 - Revised October 2016; and Y-H Lee, et al., “Fabrication of Periodic 3D Nanostmcturation for Optical Surfaces by Holographic Two-Photon-Polymerization”, Int’l Journal of Information and Electronics Engineering, Vol 6, No. 3, May 2016, each of the foregoing being hereby incorporated herein by reference in its entirety.

As used herein, the singular forms "a", "an" and "the" include plural unless the context clearly dictates otherwise. Thus, for example, reference to an emissive material includes reference to one or more of such materials.

Applicant specifically incorporates the entire contents of all cited references in this disclosure. Further, when an amount, concentration, or other value or parameter is given as either a range, preferred range, or a list of upper preferable values and lower preferable values, this is to be understood as specifically disclosing all ranges formed from any pair of any upper range limit or preferred value and any lower range limit or preferred value, regardless of whether ranges are separately disclosed. Where a range of numerical values is recited herein, unless otherwise stated, the range is intended to include the endpoints thereof, and all integers and fractions within the range. It is not intended that the scope of the invention be limited to the specific values recited when defining a range.

Other embodiments of the present invention will be apparent to those skilled in the art from consideration of the present specification and practice of the present invention disclosed herein. It is intended that the present specification and examples be considered as exemplary only with a true scope and spirit of the invention being indicated by the following claims and equivalents thereof.

Claims

WHAT IS CLAIMED IS:

1. A method of forming a three-dimensional object, comprising:

(a) providing a volume of a photopolymerizable liquid contained within a container including an optically transparent portion, the photopolymerizable liquid comprising: (i) a photopolymerizable component; (ii) upconverting nanoparticles including a sensitizer and an annihilator, the sensitizer being selected to absorb light at a first wavelength and the annihilator being selected to emit light at a second wavelength after transfer of energy from the sensitizer to the annihilator, the second wavelength being shorter than the first wavelength; and (iii) a photoinitiator that initiates polymerization of the photopolymerizable component upon excitation by light at the second wavelength, the upconverting particles and photoinitiator being dispersed throughout the photopolymerizable component and the volume of the photopolymerizable liquid being under an inert atmosphere; and

(b) irradiating the photopolymerizable liquid in the container through the at least optically transparent portion of the container with an excitation light at the first wavelength to form the three- dimensional object from the photopolymerizable liquid, wherein the excitation light is optionally temporally and/or spatially modulated, wherein optionally at least one of the container and the excitation light is movable in relation to the other, to form the three-dimensional object from the photopolymerizable liquid, wherein the photopolymerizable liquid in the container is not irradiated substantially by the second wavelength within a margin of about 1-10 mm from the internal surfaces of the container, and wherein the photopolymerizable liquid is maintained in an inert atmosphere during the irradiating step.

2. A method of forming a three-dimensional object, comprising:

(a) filling a container including at least an optically transparent window with a photopolymerizable liquid, the photopolymerizable liquid comprising: (i) a photopolymerizable component; (ii) upconverting nanoparticles including a sensitizer and an annihilator, the sensitizer being selected to absorb light at a first wavelength and the annihilator being selected to emit light at a second wavelength after transfer of energy from the sensitizer to the annihilator, the second wavelength being shorter than the first wavelength; and (iii) a photoinitiator that initiates photopolymerization of the photopolymerizable component upon excitation by light at the second wavelength;

(b) closing the container including the photopolymerizable liquid to isolate the photopolymerizable liquid from a source of oxygen; and (c) irradiating the photopolymerizable liquid in the closed container through the at least optically transparent window of the container with an excitation light at the first wavelength to form the three-dimensional object from the photopolymerizable liquid, wherein the excitation light is optionally temporally and/or spatially modulated, wherein optionally at least one of the container and the excitation light is movable in relation to the other, wherein the photopolymerizable liquid in the closed container is not irradiated substantially by the second wavelength within a margin of about 1-10 mm from the internal surfaces of the closed container, and wherein the photopolymerizable liquid is maintained in an inert atmosphere the filling, closing, and irradiating steps.

3. A method of forming a three-dimensional object, comprising:

(a) providing a volume of a photopolymerizable liquid contained within a container including an optically transparent portion, the photopolymerizable liquid comprising: (i) a photopolymerizable component; (ii) upconverting nanoparticles including a sensitizer comprising and an annihilator, the sensitizer being selected to absorb light at a first wavelength and the annihilator being selected to emit light at a second wavelength after transfer of energy from the sensitizer to the annihilator, the second wavelength being shorter than the first wavelength; and (iii) a photoinitiator that initiates polymerization of the photopolymerizable component upon excitation by light at the second wavelength, the upconverting particles and photoinitiator being dispersed throughout the photopolymerizable component and the volume of the photopolymerizable liquid being under an inert atmosphere; and

(b) irradiating the photopolymerizable liquid in the container through the at least optically transparent portion of the container with an excitation light at the first wavelength, wherein the excitation light is optionally temporally and or spatially modulated, to form the three-dimensional object from the photopolymerizable liquid, wherein the photopolymerizable liquid in the container is not irradiated substantially by the second wavelength within a margin of about 1-10 mm from the internal surfaces of the container, wherein the photopolymerizable liquid is maintained in an inert atmosphere during the irradiating step, and wherein the container is stationary during the irradiating step.

4. A method of forming a three-dimensional object, comprising:

(a) filling a container including at least an optically transparent window with a photopolymerizable liquid, the photopolymerizable liquid comprising: (i) a photopolymerizable component; (ii) upconverting nanoparticles including a sensitizer and an annihilator, the sensitizer being selected to absorb light at a first wavelength and the annihilator being selected to emit light at a second wavelength after transfer of energy from the sensitizer to the annihilator, the second wavelength being shorter than the first wavelength; and (iii) a photoinitiator that initiates polymerization of the photopolymerizable component upon excitation by light at the second wavelength;

(b) closing the container including the photopolymerizable liquid to isolate the photopolymerizable liquid from a source of oxygen; and

(c) irradiating the photopolymerizable liquid in the closed container through the at least optically transparent window of the container with an excitation light at the first wavelength, wherein the excitation light is optionally temporally and/or spatially modulated, to form the three- dimensional object from the photopolymerizable liquid, wherein the photopolymerizable liquid in the closed container is not substantially by the second wavelength irradiated within a margin of about 1-10 mm from the internal surfaces of the closed container, wherein the photopolymerizable liquid is maintained in an inert atmosphere during the filling, closing, and irradiating steps, and wherein the filled container is stationary during the irradiating step.

5. The method of any of claims 1-4 wherein the photopolymerizable liquid is selectively irradiated with the excitation light at the first wavelength.

6. The method of any of claims 1-4 wherein the three-dimensional object is formed in the volume of the photopolymerizable liquid at a distance of greater than 1 cm from the interface of the photopolymerizable fluid with the inside surface of the container in which it is disposed.

7. The method of any of claims 1-4 wherein the irradiation step includes application of continuous excitation light.

8. The method of any of claims 1-4 wherein the irradiation step includes application of intermittent excitation light.

9. The method of any of claims 1-4 wherein the irradiation step includes application of intermittent excitation light that is preceded or followed by irradiation with continuous light.

10. The method of any of claims 1-4 wherein the excitation light is spatially modulated by a liquid crystal display (LCD) or a digital micromirror display (DMD).

11. The method of any of claims 1-4 wherein the first wavelength is in the visible range, and the second wavelength is in the visible range.

12. The method of any of claims 1-4 wherein the first wavelength is in the range of 400 nm - 700 nm.

13. The method of any of claims 1-4 wherein the second wavelength is in the range of 400 nm - 700 nm.

14. The method of any of claims 1-4 wherein the photopoly merizable liquid has a viscosity of greater than 1 centipoise under the conditions in which the method is carried out.

15. The method of any of claims 1-4 wherein the photopoly merizable liquid has a viscosity greater than 1,000 centipoise under the conditions in which the method is carried out.

16. The method of any of claims 1-4 wherein the photopoly merizable liquid has a viscosity greater than 5,000 centipoise under the conditions in which the method is carried out.

17. The method of any of claims 1-4 wherein the excitation light at the first wavelength is created by an excitation source emitting excitation light with a power per unit area of less than 1000 W/cm².

18. The method of any of claims 1-4 wherein the excitation light at the first wavelength is created by an excitation source emitting excitation light with a power per unit area of less than 100 W/cm².

19. The method of any of claims 1-4 wherein the excitation light at the first wavelength is created by an excitation source emitting excitation light with a power per unit area of less than 1 W/cm².

20. The method of any of claims 1-4 wherein the excitation light at the first wavelength is created by an excitation source emitting excitation light with a power per unit area of less than 100 mW/cm².

21. The method of any of claims 1-4 wherein the excitation light at the first wavelength is created by an excitation source comprising a laser.

22. The method of any of claims 1-4 wherein a quadratic relationship exists between the power of the excitation light and emission from the annihilator.

23. A method of forming a three-dimensional object, comprising:

(b) irradiating the photopolymerizable liquid in the container through the at least optically transparent portion of the container with light wherein the irradiating is carried out with both: (i) an excitation light at the first wavelength, and (ii) a depletion light at a third wavelength, different from the first and second wavelengths, that inhibits the excitation of the upconverting particles, to form the three-dimensional object, wherein optionally at least one of the excitation and depletion lights is temporally and/or spatially modulated, to form the three-dimensional object, wherein the photopolymerizable liquid in the container is not irradiated substantially by the second wavelength within a margin of about 1-10 mm from the internal surfaces of the container, wherein the photopolymerizable liquid is maintained in an inert atmosphere during the irradiating step, and wherein the filled container is stationary during the irradiating step.

24. A method of forming a three-dimensional object, comprising:

(b) closing the container including the photopolymerizable liquid to isolate the photopolymerizable liquid from a source of oxygen; and (c) irradiating the photopolymerizable liquid in the closed container through the at least optically transparent window of the container with light wherein the irradiating is carried out with both: (i) an excitation light at the first wavelength, and (ii) a depletion light at a third wavelength, different from the first and second wavelengths, that inhibits the excitation of the upconverting particles, to form the three-dimensional object, wherein optionally at least one of the excitation and depletion lights is temporally and/or spatially modulated, wherein the photopolymerizable liquid in the container is not irradiated substantially by the second wavelength within a margin of about 1-10 mm from the internal surfaces of the closed container, wherein the photopolymerizable liquid is maintained in an inert atmosphere during the filling, closing, and irradiating steps, and wherein the filled container is stationary during the irradiating step.

25. A method of forming a three-dimensional object, comprising:

(b) irradiating the photopolymerizable liquid in the container through the at least optically transparent portion of the container with light wherein the irradiating is carried out with both: (i) an excitation light at the first wavelength, and (ii) a depletion light at a third wavelength, different from the first and second wavelengths, that inhibits the excitation of the upconverting particles, to form the three-dimensional object, wherein optionally at least one of the excitation and depletion lights is temporally and/or spatially modulated, wherein at least one of the excitation and depletion lights and container is movable in relation to another, wherein the photopolymerizable liquid in the container is not irradiated substantially by the second wavelength within a margin of about 1-10 mm from the internal surfaces of the container, and wherein the photopolymerizable liquid is maintained in an inert atmosphere during the irradiating step.

26. A method of forming a three-dimensional object, comprising:

(b) closing the container including the photopolymerizable liquid to isolate the photopolymerizable liquid from a source of oxygen, and

(c) irradiating the photopolymerizable liquid in the closed container through the at least optically transparent window of the container with light wherein the irradiating is carried out with both: (i) an excitation light at the first wavelength, and (ii) a depletion light at a third wavelength, different from the first and second wavelengths, that inhibits the excitation of the upconverting particles, to form the three-dimensional object, wherein optionally at least one of the excitation and depletion lights is temporally and/or spatially modulated, wherein at least one of the excitation and depletion lights and container is movable in relation to another, wherein the photopolymerizable liquid in the container is not irradiated substantially by the second wavelength within a margin of about 1-10 mm from the internal surfaces of the closed container, and wherein the photopolymerizable liquid is maintained in an inert atmosphere during the filling, closing and irradiating steps.

27. The method of any of claims 23-26 wherein the excitation light is both spatially and temporally modulated, and the depletion light is: (i) uniform flood exposure over time, (ii) uniform flood exposure modulated in intensity over time; (iii) uniform intensity exposure spatially modulated over time; or (iv) spatially and temporally modulated over time.

28. The method of any of claims 23-26 wherein the excitation light is (i) uniform flood exposure over time or (ii) uniform flood exposure modulated in intensity over time, and the depletion light is both spatially and temporally modulated.

29. The method of any of claims 23-26 wherein the photopolymerizable liquid is selectively irradiated with the excitation light at the first wavelength.

30. The method of any of claims 23-26 wherein the volume of the three-dimensional objects is formed in the volume of the photopolymerizable liquid at a distance of greater than 1 cm from the interface of the photopolymerizable fluid with the inside surface of the container in which it is disposed.

31. The method of any of claims 23-26 wherein irradiating with the excitation light includes application of continuous excitation light.

32. The method of any of claims 23-26 wherein irradiating with the excitation light includes application of intermittent excitation light.

33. The method of any of claims 23-26 wherein irradiating with the excitation light includes application of intermittent excitation light that is preceded or followed by irradiation with continuous excitation light.

34. The method of any of claims 23-26 wherein irradiating with the depletion light includes application of continuous depletion light.

35. The method of any of claims 23-26 wherein irradiating with the depletion light includes application of intermittent depletion light.

36. The method of any of claims 23-26 wherein irradiating with the depletion light includes application of intermittent depletion light that is preceded or followed by irradiation with continuous depletion light.

37. The method of any of claim 23-26 wherein a patterned exposure is created by a liquid crystal display (LCD).

38. The method of any of claims 23-26 wherein a patterned exposure is created by a digital micro mirror display (DMD).

39. The method of any of claims 23-26 wherein the first wavelength is in the visible range.

40. The method of any of claims 23-26 wherein the second wavelength is in the visible.

41. The method of any of claims 23-26 wherein the first wavelength is in the range of 400 nm -

700 nm.

42. The method of any of claims 23-26 wherein the second wavelength is in the range of 400 - 700 nm.

43. The method of any of claims 23-26 wherein the third wavelength is the range of 400-700 nm, up to 1300-1600 nm.

44. The method of any of claims 23-26 wherein the photopolymerizable liquid has a viscosity of greater than 1 centipoise, under the conditions in which the method is carried out.

45. The method of any of claims 23-26 wherein the photopolymerizable liquid has a viscosity greater than 1,000 centipoise, under the conditions in which the method is carried out.

46. The method of any of claims 23-26 wherein the photopolymerizable liquid has a viscosity greater than 5,000 centipoise, under the conditions in which the method is carried out.

47. The method of any of claims 23-26 wherein the excitation light at the first wavelength is created by an excitation source emitting excitation light with a power per unit area of less than 1000 W/cm².

48. The method of any of claims 23-26 wherein the excitation light at the first wavelength is created by an excitation source emitting excitation light with a power per unit area of less than 100 W/cm².

49. The method of any of claims 23-26 wherein the excitation light at the first wavelength is created by an excitation source emitting excitation light with a power per unit area of less than 1 W/cm².

50. The method of any of claims 23-26 wherein the excitation light at the first wavelength is created by an excitation source emitting excitation light with a power per unit area of less than 100 mW/cm².

51. The method of any of claims 23-26 wherein the excitation light at the first wavelength is created by an excitation source comprising a laser.

52. The method of any of claims 23-26 wherein a quadratic relationship exists between the power of the excitation light and emission from the annihilator.

53. A method of forming a three-dimensional object, comprising:

(a) providing a volume of a photopolymerizable liquid contained within a build chamber including an optically transparent portion, the photopolymerizable liquid comprising: (i) a photopolymerizable component; (ii) upconverting nanoparticles including a center portion including a sensitizer and an annihilator, the sensitizer being selected to absorb light at a first wavelength and the annihilator being selected to emit light at a second wavelength after transfer of energy from the sensitizer to the annihilator, the second wavelength being shorter than the first wavelength; and (iii) a photoinitiator that initiates polymerization of the photopolymerizable component upon excitation by light at the second wavelength, the upconverting particles and photoinitiator being dispersed throughout the photopolymerizable component and the volume of the photopolymerizable liquid being under an inert atmosphere;

(b) directing a beam of excitation light at the first wavelength through the optically transparent portion of the build chamber to a location within the volume of the photopolymerizable liquid to upconvert the excitation light to the second wavelength to polymerize the photopolymerizable liquid at the location; and

(c) further directing the excitation light within the volume of photopolymerizable liquid to form the three-dimensional object from the photopolymerizable liquid, wherein the photopolymerizable liquid in the container is not irradiated substantially by the second wavelength within a margin of about 1-10 mm from the internal surfaces of the build chamber, wherein the photopolymerizable liquid is maintained in an inert atmosphere.

54. A method of forming a three-dimensional object, comprising:

(a) disposing a volume of a photopolymerizable liquid within a container including at least an optically transparent portion, the photopolymerizable liquid comprising: (i) a photopolymerizable component; (ii) upconverting nanoparticles including a sensitizer and an annihilator, the sensitizer being selected to absorb light at a first wavelength and the annihilator being selected to emit light at a second wavelength after transfer of energy from the sensitizer to the annihilator, the second wavelength being shorter than the first wavelength; and (iii) a photoinitiator that initiates polymerization of the photopolymerizable component upon excitation by light at the second wavelength;

(b) closing the container including the photopolymerizable liquid to isolate the photopolymerizable liquid from a source of oxygen; (c) directing a beam of excitation light at the first wavelength through the optically transparent portion of the closed container to a location within the volume of the photopolymerizable liquid to upconvert the excitation light to the second wavelength to polymerize the photopolymerizable liquid at the location; and

(d) further directing the excitation light within the volume of photopolymerizable liquid to form the three-dimensional object from the photopolymerizable liquid, wherein the photopolymerizable liquid in the container is not irradiated substantially by the second wavelength within a margin of about 1-10 mm from the internal surfaces of the closed container, wherein the photopolymerizable liquid is maintained in an inert atmosphere during the disposing, closing, and directing steps.

55. The method of claim 53 wherein the photopolymerizable liquid is selectively irradiated with the excitation light at the first wavelength.

56. The method of claim 54 wherein the photopolymerizable liquid is selectively irradiated with the excitation light at the first wavelength.

57. The method of claim 53 or claim 54 wherein the excitation light is spatially modulated and the spatially modulated is created by a liquid crystal display (LCD) or a digital micromirror display (DMD).

58. The method of claim 53 or claim 54 wherein the first wavelength is in the visible range, and the second wavelength is in the visible range.

59. The method of claim 53 or claim 54 wherein the first wavelength is in the range of 400 nm - 700 nm.

60. The method of claim 53 or claim 54 wherein the second wavelength is in the range of 400 - 700 nm.

61. The method of claim 53 or claim 54 wherein the photopolymerizable liquid has a viscosity of greater than 1 centipoise, under the conditions in which the method is carried out.

62. The method of claim 53 or claim 54 wherein the photopolymerizable liquid has a viscosity greater than 1,000 centipoise, under the conditions in which the method is carried out.

63. The method of claim 53 or claim 54 wherein the photopolymerizable liquid has a viscosity greater than 5,000 centipoise, under the conditions in which the method is carried out.

64. The method of claim 53 or claim 54 wherein the excitation light at the first wavelength is created by an excitation source emitting excitation light with a power per unit area of less than 1000 W/cm².

65. The method of claim 53 or claim 54 wherein the excitation light at the first wavelength is created by an excitation source emitting excitation light with a power per unit area of less than 100 W/cm².

66. The method of claim 53 or claim 54 wherein the excitation light at the first wavelength is created by an excitation source emitting excitation light with a power per unit area of less than 1 W/cm².

67. The method of claim 53 or claim 54 wherein the excitation light at the first wavelength is created by an excitation source emitting excitation light with a power per unit area of less than 100 mW/cm².

68. The method of claim 53 or claim 54 wherein the excitation light at the first wavelength is created by an excitation source comprising a laser.

69. The method of claim 53 or claim 54 wherein a quadratic relationship exists between the power of the excitation light and emission from the annihilator.

70. The method of claim 53 wherein at least one of the build chamber and the excitation light is movable in relation to the other, during the directing step.

71. The method of claim 54 wherein at least one of the container and the excitation light is movable in relation to the other during the directing step.

72. The method of claim 53 wherein the build region is rotatable in relation to the excitation light during the directing step to expose another side from another angle.

73. The method of claim 54 wherein the container is rotatable in relation to the excitation light during the directing step to expose another side from another angle.

74. The method of claim 53 wherein the three-dimensional object is formed in the volume of the photopolymerizable liquid at a distance of greater than 1 cm from the interface of the photopolymerizable fluid with the inside surface of the build chamber in which it is disposed.

75. The method of claim 54 wherein the three-dimensional object is formed in the volume of the photopolymerizable liquid at a distance of greater than 1 cm from the interface of the photopolymerizable fluid with the inside surface of the container in which it is disposed.

76. A cartridge for use in a 3D printing method including upconversion, the cartridge comprising: an hermetically sealed optically transparent container including a photopolymerizable liquid that has been purged with an inert gas, the photopolymerizable liquid comprising: (i) a photopolymerizable component; (ii) upconverting nanoparticles including a sensitizer and an annihilator, the sensitizer being selected to absorb light at a first wavelength and the annihilator being selected to emit light at a second wavelength after transfer of energy from the sensitizer to the annihilator, the second wavelength being shorter than the first wavelength; and (iii) a photoinitiator that initiates polymerization of the photopolymerizable component upon excitation by light at the second wavelength.

77. The cartridge of claim 76 wherein the container includes a bottom and perpendicular optically flat walls.

78. The method of any of claims 1-4, 23-26, and 54 wherein the entire container is optically transparent.

79. The method of any of claims 1-4, 23-26, and 54 wherein the entire container is optically transparent and the container includes a bottom and perpendicular optically flat walls.

80. The method of any of claim 53 wherein the entire build chamber is optically transparent.

81. The method of claim 53 wherein the entire build chamber is optically transparent and the build chamber includes a bottom and perpendicular optically flat walls.

82. A method of forming a three-dimensional object, comprising:

(a) providing a volume of a photopolymerizable liquid contained within a container including a bottom surface including an optically transparent portion, the photopolymerizable liquid comprising: (i) a photopolymerizable component; (ii) upconverting nanoparticles including a center portion including a sensitizer and an annihilator, the sensitizer being selected to absorb light at a first wavelength and the annihilator being selected to emit light at a second wavelength after transfer of energy from the sensitizer to the annihilator, the second wavelength being shorter than the first wavelength; and (iii) a photoinitiator that initiates polymerization of the photopolymerizable component upon excitation by light at the second wavelength, the upconverting particles and photoinitiator being dispersed throughout the photopolymerizable component and the volume of the photopolymerizable liquid being under an inert atmosphere;

(b) positioning a carrier at the interface of the top surface of the photopolymerizable liquid in the container with the atmosphere in the container above the top surface;

(c) directing excitation light at the first wavelength through the optically transparent portion of the container and through the volume of the photopolymerizable liquid in the container to a location at the interface to upconvert the excitation light to the second wavelength to polymerize the photopolymerizable liquid at the location to form the top surface of the three-dimensional object; and

(d) capturing the top surface of the three-dimensional object with the carrier, and advancing the carrier away from the interface as formation of the three-dimensional object is continued by irradiating the photopolymerizable liquid at the top surface thereof until the three-dimensional object is formed, wherein the photopolymerizable liquid is maintained in an inert atmosphere during the disposing, closing, and directing steps.

83. The method of claim 82 wherein the first wavelength is in the visible range, and the second wavelength is in the visible range.

84. The method of claim 82 wherein the first wavelength is in the range of 400 nm - 700 nm.

85. The method of claim 82 wherein the second wavelength is in the range of 400 - 700 nm.

86. The method of claim 82 wherein the photopolymerizable liquid has a viscosity of greater than 1 centipoise, under the conditions in which the method is carried out.

87. The method of claim 82 wherein the photopolymerizable liquid has a viscosity greater than 1,000 centipoise, under the conditions in which the method is carried out.

88. The method of claim 82 wherein the photopolymerizable liquid has a viscosity greater than 5,000 centipoise, under the conditions in which the method is carried out.

89. The method of claim 82 wherein the excitation light at the first wavelength is created by an excitation source emitting excitation light with a power per unit area of less than 1000 W/cm².

90. The method of claim 82 wherein the excitation light at the first wavelength is created by an excitation source emitting excitation light with a power per unit area of less than 100 W/cm².

91. The method of claim 82 wherein the excitation light at the first wavelength is created by an excitation source emitting excitation light with a power per unit area of less than 1 W/cm².

92. The method of claim 82 wherein the excitation light at the first wavelength is created by an excitation source emitting excitation light with a power per unit area of less than 100 mW/cm².

93. The method of claim 82 wherein the excitation light at the first wavelength is created by an excitation source comprising a laser.

94. The method of claim 82 wherein a quadratic relationship exists between the power of the excitation light and emission from the annihilator.

95. The method of any of claims 1-4, 23-26, and 82 wherein the container is rotated to expose another side from another angle.

96. An optical printhead device for delivering a beam of excitation light into a photopolymerizable material, the optical printhead device comprising, in combination, a collimator arranged to collimate the excitation light along an optical axis, a spatial filter arranged to receive and filter the collimated excitation light, and an objective lens having an aperture with a center point and perimeter edges, the objective lens being arranged for focusing the filtered excitation light into the photopolymerizable material to form a voxel.

97. The optical printhead device of claim 96 wherein the spatial filter is capable of blocking the excitation light that travels along the optical axis exiting the collimator near the center point of the objective lens such that the excitation light passes along the perimeter edges of the aperture of the objective.

98. The optical printhead device of claim 96 wherein the spatial filter acts on a two-dimensional wavefront exiting the collimator by modifying the amplitude and or phase of the wavefront.

99. The optical printhead device of claim 96 wherein the optical device is adapted for connection by an optical fiber to an excitation source.

100. The optical printhead device of claim 96 wherein the photopolymerizable material comprises a photopolymerizable liquid.

101. The new, useful, and unobvious processes, machines, manufactures, and compositions of matter, as shown and described herein.