WO2021067577A1 - Convertisseurs-élévateurs fonctionnalisés par des atomes lourds pour augmenter des seuils de conversion-élévation pour l'impression 3d - Google Patents

Convertisseurs-élévateurs fonctionnalisés par des atomes lourds pour augmenter des seuils de conversion-élévation pour l'impression 3d Download PDF

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WO2021067577A1
WO2021067577A1 PCT/US2020/053765 US2020053765W WO2021067577A1 WO 2021067577 A1 WO2021067577 A1 WO 2021067577A1 US 2020053765 W US2020053765 W US 2020053765W WO 2021067577 A1 WO2021067577 A1 WO 2021067577A1
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liquid
upconverter
energy
sensitizer
upconversion
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PCT/US2020/053765
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English (en)
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Daniel N. CONGREVE
Samuel N. SANDERS
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President And Fellows Of Harvard College
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C64/00—Additive manufacturing, i.e. manufacturing of three-dimensional [3D] objects by additive deposition, additive agglomeration or additive layering, e.g. by 3D printing, stereolithography or selective laser sintering
    • B29C64/10—Processes of additive manufacturing
    • B29C64/106—Processes of additive manufacturing using only liquids or viscous materials, e.g. depositing a continuous bead of viscous material
    • B29C64/124—Processes of additive manufacturing using only liquids or viscous materials, e.g. depositing a continuous bead of viscous material using layers of liquid which are selectively solidified
    • B29C64/129—Processes of additive manufacturing using only liquids or viscous materials, e.g. depositing a continuous bead of viscous material using layers of liquid which are selectively solidified characterised by the energy source therefor, e.g. by global irradiation combined with a mask
    • B29C64/135—Processes of additive manufacturing using only liquids or viscous materials, e.g. depositing a continuous bead of viscous material using layers of liquid which are selectively solidified characterised by the energy source therefor, e.g. by global irradiation combined with a mask the energy source being concentrated, e.g. scanning lasers or focused light sources
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B33—ADDITIVE MANUFACTURING TECHNOLOGY
    • B33Y—ADDITIVE MANUFACTURING, i.e. MANUFACTURING OF THREE-DIMENSIONAL [3-D] OBJECTS BY ADDITIVE DEPOSITION, ADDITIVE AGGLOMERATION OR ADDITIVE LAYERING, e.g. BY 3-D PRINTING, STEREOLITHOGRAPHY OR SELECTIVE LASER SINTERING
    • B33Y10/00—Processes of additive manufacturing
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B33—ADDITIVE MANUFACTURING TECHNOLOGY
    • B33Y—ADDITIVE MANUFACTURING, i.e. MANUFACTURING OF THREE-DIMENSIONAL [3-D] OBJECTS BY ADDITIVE DEPOSITION, ADDITIVE AGGLOMERATION OR ADDITIVE LAYERING, e.g. BY 3-D PRINTING, STEREOLITHOGRAPHY OR SELECTIVE LASER SINTERING
    • B33Y70/00—Materials specially adapted for additive manufacturing
    • C—CHEMISTRY; METALLURGY
    • C07—ORGANIC CHEMISTRY
    • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
    • C07C15/00—Cyclic hydrocarbons containing only six-membered aromatic rings as cyclic parts
    • C07C15/20—Polycyclic condensed hydrocarbons
    • C07C15/27—Polycyclic condensed hydrocarbons containing three rings
    • C07C15/28—Anthracenes

Definitions

  • additive manufacturing or “3D printing” finds uses in industries such as prototyping and manufacturing.
  • 3D printing Several methods of 3D printing are known, but none of these methods truly operate in three dimensions. Instead, these methods use some form of extrusion, either layer by layer in most cases, or continuous withdrawal methods, to photopolymerize a polymer at a liquid-solid interface.
  • the main limitation with these approaches is the inability to truly 3D “print” a pattern because light absorption occurs not only at the desired location, but also at the interface, which leads to undesired, uncontrolled, or inadequate polymerization. Instead, a very slow interfacial process is used, limiting throughput, practicality, and cost efficiency.
  • Typical implementations of 3D printing involve a container of liquid and a solid stage where the solid stage is lowered until a short layer of liquid polymer covers the stage.
  • a laser “writes” a pattern onto this thin layer which hardens upon exposure.
  • the stage then lowers further to immerse this material in more liquid, and exposure repeats until the desired structure has been formed. Due to the ability to create arbitrary designs, as well as form shapes that would be difficult to achieve by standard machining techniques, this technique has garnered enormous interest on the market.
  • one of the main challenges in this field is that the stepwise printing nature limits printing speed and introduces steps into the surface, as a single layer of material is printed at a time. Thus, improvements in 3D printing technologies are needed.
  • a liquid comprising a sensitizer that may be configured to absorb a first energy to form a first triplet state, and an upconverter, wherein the upconverter may be configured to receive the first triplet state from the sensitizer to produce a second triplet state.
  • the upconverter may be configured to upconvert the first energy upon interaction with a second upconverter to produce a second energy where the second energy is greater than the first energy.
  • the upconverter comprises at least one heavy atom with an atomic number of at least 17.
  • the liquid may further comprise a polymerizable species configured to receive the second energy from the upconverter to cause polymerization of the polymerizable species to occur.
  • liquid comprising a metal porphyrin having a formula (I):
  • R 3 , R 6 , R 9 , R 12 are independently selected from the group consisting of hydrogen, optionally substituted alkyl, optionally substituted aryl, and optionally substituted alkenyl
  • R 1 , R 2 , R 4 , R 5 , R 7 , R 8 , R 10 , and R 11 are independently selected from the group consisting of hydrogen, optionally substituted alkyl, optionally substituted aryl, and optionally substituted alkenyl.
  • the liquid in some cases, also comprises a diphenyl anthracene having a formula (II): wherein R A and R B are independently selected from the group consisting of optionally substituted alkyl and optionally substituted aryl, and wherein the diphenyl anthracene having the formula (II) further comprises at least one heavy atom with an atomic number of at least 17.
  • the method comprises providing a liquid, the liquid comprising a polymerizable species, a sensitizer, and an upconverter.
  • the upconverter comprises at least one heavy atom with an atomic number of at least 17.
  • the method also comprises focusing at least one laser beam on a focal region of the liquid. At least some of the laser beam with a first energy may be absorbed by the sensitizer, wherein the first energy can be transmitted from the sensitizer to the upconverter to produce a triplet state in the upconverter. In some cases, the triplet state decays via upconversion to produce light (e.g., a photon) of a second energy, where the second energy may be greater than the first energy.
  • light e.g., a photon
  • the second energy in some embodiments, polymerizes the polymerizable species within the focal region to produce a polymeric object.
  • the method is performed where substantially no polymerization occurs outside of the focal region of the liquid due to the at least one laser beam.
  • the method also includes separating the polymeric object from the liquid.
  • FIG. 1 shows a schematic diagram of a liquid configured to increase the upconversion threshold using a triplet exciton acceptor functionalized with a heavy atom, according to one set of embodiments;
  • FIG. 2 shows example upconverter (e.g. emitter, annihilator) molecules functionalized with heavy atoms, according to one set of embodiments;
  • upconverter e.g. emitter, annihilator
  • FIG. 3 shows a plot of upconverted photoluminescence at 476 nm vs input laser at 638 nm to illustrate the increase in upconversion threshold, according to one set of embodiments
  • FIGS. 4A-4B are photographic images comparing linear and quadratic processes in a 1 cm cuvette of PdTPBP and Br-TIPS anthracene in oleic acid where in the linear process, blue light is generated throughout the vial, while in a quadratic process, blue light is generated only at the focal spot whereby the linear process results from directly exciting the annihilator at 365 nm, while the quadratic process results from triplet fusion upconversion excited at 637 nm, according to one set of embodiments;
  • FIG. 4C is a schematic diagram of the upconversion process where two low energy photons generate two singlet excitons on sensitizer molecules, which intersystem cross (1) to generate triplet excitons, and then these excitons triplet energy transfer to the annihilator (2) where they undergo triplet fusion (3) to generate a higher energy singlet, which can radiatively decay by emitting a high energy photon that couples to the photoinitiator, according to some embodiments;
  • FIG. 5A shows chemical structures of examples of upconversion molecules showing, from left to right, the chemical structures of the sensitizer PdTPBP, and the annihilators TIPS -anthracene, Cl-TIPS anthracene, and 2Cl-TIPS-anthracene, according to one set of embodiments;
  • FIG. 5B is a plot of the absorption of the sensitizer PdTPBP and the annihilators TIPS-anthracene, Cl-TIPS anthracene, and 2Cl-TIPS-anthracene, according to one set of embodiments;
  • FIG. 5C is a plot of the upconversion efficiency as a function of input power for the annihilators TIPS-anthracene, Cl-TIPS anthracene, and 2C1-TIPS -anthracene where a linear fit (dotted lines) to the quadratic regime gives the threshold of each material (circles), according to some embodiments;
  • FIG. 6A is a schematic overview of the UCNC synthesis, according to one embodiment
  • FIG. 6B is a photographic image of UCNCs diluted in acetone showing penetration depths where the capsules are excited at 635 nm and are imaged through a 600 nm shortpass filter, according to one set of embodiments;
  • FIG. 6C is an SEM image of the UCNCs showing the scale and uniformity of the synthesis, according to one embodiment
  • FIG. 6D shows a TEM image of the UCNCs, according to one embodiment
  • FIG. 6E shows an image of a dispersion of the initial micelles and final UCNCs in acetone under the same conditions showing the necessity of the silica shell to upconversion survival where the emission peak at -800 nm corresponds to phosphorescence from the sensitizer PdTPBP, according to one set of embodiments;
  • FIG. 7A is a photographic image of a printing setup that moves a laser spot in three dimensions, according to one embodiment
  • FIG. 7B is a photographic image of a benchmark boat called “Benchy,” printed according to certain embodiments described herein, sitting on a dime for scale, according to one set of embodiments;
  • FIG. 7C is a photographic image of multiple Benchy prints showing the repeatability of the printing process using a resin, according to some embodiments.
  • FIGS. 7D-7E are schematic illustrations of side and top views of the Benchy STL file, respectively, according to one set of embodiments.
  • FIGS. 7F-7G are photographic images of side and top views of the final print that show the fidelity in reproduction of the main features, according to one set of embodiments;
  • FIG. 8 shows a plot of emission-absorption overlap between the upconverted emission and the titanocene photoinitiator, according to one set of embodiments
  • FIG. 9 shows the absorption spectra of several annihilators, according to some embodiments.
  • FIG. 10 shows UCNCs and F127 micelles dispersed in various solvents where the UCNCs and F127 micelles were both synthesized in water and added at 1:30 ratio to the listed solvents in which they were then excited at 635 nm and imaged through a 550 nm shortpass filter, and the tap water sample was dispersed in water directly from the tap and left uncapped for 20 minutes before taking the image whereby acrylic acid and PEGDA were each used to assess capsule durability in acrylate -based monomers for printing resins, according to one set of embodiments;
  • 1 lA-1 IB show Formlab’s print of the same Benchy STL where the file was imported into the free software Preform 3.2.2 and simulated for printing on a Form 3B printer at 50 micron layer height and whereby the object was scaled to be 8.35 mm in height to match the dimensions of the Benchy printed using liquids and methods described herein, and whereby the object required 176 layers and less than 0.1 mL of resin utilizing the "one click print" function to generate the printable structure, which resulted in an object with 250 layers at 50 micron layer height, using 0.59 mL of resin, according to one set of embodiments;
  • FIG. 12A-12B are photographic images showing an overprinted boat with a lack of discernable features whereby the issue can be remedied by altering the print speed and irradiation power, according to one set of embodiments;
  • FIG. 12C is a photographic image of an underprinted boat that shows missing features and damage from the wash process whereby the issue can be remedied by altering the print speed and irradiation power, according to one set of embodiments;
  • FIGS. 13A-13B show the Harvard logo printed from the PETA-based resin and corresponding STL file used to generate the print, according to one set of embodiments.
  • FIG. 14A-14B are photographs of a pyramid printed from PEGDA-based resin and FIG. 14C shows and the corresponding STL file used to generate the print, according to one set of embodiments.
  • Articles and methods for increasing the triplet upconversion threshold are generally described. Some embodiments, for example, are directed to articles and methods that use a triplet sensitizer and a heavy atom-functionalized upconverter to produce upconverted photons (e.g., light of a second energy).
  • the light can be used to polymerize a polymerizable species.
  • Other upconversion configurations can also be used in other embodiments. In some cases, this may allow true 3D printing to be achieved due to improved control of light absorption, e.g., without needing to “print” on a layer-by-layer basis.
  • a liquid 100 comprises a sensitizer 110, which may form a triplet state upon photoexcitation (for example by laser 115 with first energy 120).
  • the triplet state formed by sensitizer 110 may first start as a singlet state and convert to a triplet state via intersystem crossing (not pictured) within sensitizer 110.
  • Sensitizer 110 may then transfer this triplet state to an upconverter 130, illustrated with arrow 129.
  • Upconverter 130 may then interact with another upconverter 140 and undergo triplet-triplet annihilation to produce upconverted photons (i.e., photons of higher energy than the photons used to photoexcite the sensitizer).
  • upconverters 130 and 140 may further comprise a heavy atom, described in more detail below.
  • An acceptor 160 may then receive a triplet state from upconverters 130 and 140 where acceptor 160 has a triplet exciton energy level lower than both the sensitizer 110 and upconverters 130 and 140.
  • the higher energy photons may be used, for example, to cause polymerization of a polymerizable entity within the liquid, which can be used for 3D printing, or other applications as discussed herein.
  • triplet upconversion (or triplet-triplet annihilation, TTA) may be used to produce light of a higher energy relative to light used to photoexcite the sensitizer or the upconverter.
  • TTA triplet-triplet annihilation
  • the inclusion of a heavy atom-functionalized upconverter or heavy atom-functionalized auxiliary molecule may slow or prevent two triplet-excited upconverters from undergoing TTA, thereby slowing the process of TTA and hence avoiding saturation of triplet upconverters.
  • an upconverter functionalized with a heavy atom may help facilitate the relaxation of an excited state triplet on an upconverter.
  • relaxation of the excited state triplet on the upconverter limits its ability to undergo upconversion with another upconverter.
  • This may advantageously allow for an increase in laser power to result in an increase of the rate of TTA (i.e. the upconversion frequency) and thus can allow higher powered lasers to maintain a quadratic or other dependence on the photoluminescence of upconverter as a function of laser power (i.e., upconversion remains second order with respect to the input laser power or a higher order).
  • two photons absorbed by the sensitizer may be combined by the upconverter to produce upconverted photons (e.g., having higher energy) that can be used to cause polymerization of polymerizable entity.
  • upconverted photons e.g., having higher energy
  • lasers can be focused on polymerizable entities within a liquid to cause polymerization to occur due to the high number of higher-energy photons produced by the upconversion of the laser light, while elsewhere within the liquid, minimal or no upconversion of light occurs, and thus, no polymerization of the polymerizable entity can occur.
  • This can be used, for example, to achieve true 3D-printing within the liquid, e.g., by focusing one or multiple lasers to illuminate appropriate locations within the liquid, without requiring layer-by-layer printing.
  • Functionalizing the upconverter with a heavy atom may act to enhance the overall above-described effect; that is, an upconverter (e.g., an emitter) functionalized with a heavy atom may further slow or prevent two triplet-excited upconverters from undergoing TTA.
  • a “heavy atom” is any atom with an atomic number greater than 17 (i.e., chlorine or heavier).
  • an upconverter without a heavy atom can have a first upconversion threshold, while that same upconverter functionalized with a first heavy atom (e.g., chlorine) can have a second upconversion threshold higher than the first upconversion threshold.
  • a first heavy atom e.g., chlorine
  • same upconverter functionalized with a second heavy atom can have a third upconversion threshold higher than the second upconversion threshold and the first upconversion threshold.
  • a second heavy atom e.g., bromine
  • a third upconversion threshold higher than the second upconversion threshold and the first upconversion threshold.
  • Those of ordinary skill in the art in view of the teachings of this disclosure will be capable of selecting the appropriate number, kind (e.g., atomic number of at least 17), and/or the number of heavy atoms on an upconverter in order to tune the upconversion threshold over a particular range of upconversion thresholds (e.g., at least 1.7 W/cm 2 and no greater than 283 W/cm 2 , or other ranges such as are discussed herein).
  • an upconverter comprising at least one heavy atom may advantageously permit faster relaxation of a triplet state on an upconverter. This may be achieved by enhancing the ability of an upconverter to undergo intersystem crossing. It will be understood by those skilled in the art that a transition from a triplet state to a singlet state (or vice versa) is “forbidden” in a quantum mechanical sense; however, the probability of this process (i.e., intersystem crossing) is more favorable when spin/orbit interactions (i.e., spin-orbit coupling) increase by inclusion of atoms with a larger number of occupied atomic orbitals.
  • Heavy atoms such as bromine or iodine, increase spin-orbit coupling interactions and may facilitate faster relaxation times of the triplet state of an upconverter.
  • the heavy atom is chlorine.
  • the heavy atom is bromine.
  • Still other examples include iodine, calcium, nickel, iron, platinum, palladium, manganese, or zinc, or the like.
  • more than one heavy atom is present. In cases where more than one heavy atom is present, these heavy atoms can be identical or distinct.
  • the addition of a suitable heavy atom reduces triplet lifetimes of the upconverter, causing the relationship between the power of input laser 115 and the upconverted light 150 to remain quadratic at higher input powers than in the absence of the additional heavy atoms.
  • an external heavy atom may be used. This effect may include a heavy atom facilitating spin-orbit coupling as described above, but when the heavy atom is attached to molecule present in the system that is not the upconverter, such as the sensitizer, an acceptor, or an auxiliary molecule, such as a solvent molecule, as non limiting examples.
  • a solvent molecule is optionally present and distinct from the sensitizer or the upconverter.
  • Non-limiting examples of solvent molecules comprising a heavy atom include iodobenzene, ethyl iodide, 1,2- dibromoethane, 1,2-dichloroethane, dichloromethane, 2-bromopropane, and 1- bromopropane.
  • any effect that creates this effect may be suitable.
  • other effects that facilitate or enhance intersystem crossing may also be used, such as the including of a paramagnetic species in the liquid.
  • certain embodiments comprise a liquid.
  • the liquid may be a solvent, such as an organic solvent, that dissolves or otherwise contains the sensitizer, the upconverter, the acceptor, and/or the polymerizable species. These are discussed in more detail below.
  • a sensitizer is present, used interchangeably herein with “triplet sensitizer.”
  • a sensitizer or a triplet sensitizer can readily intersystem cross to a triplet state following excitation to its singlet state (i.e., by a stimulus, such as light, heat, etc.).
  • the sensitizer may be excited (e.g., by a photon) to produce an excited state sensitizer comprising a singlet excited state, wherein the excited state singlet may rapidly produce an excited state triplet in the sensitizer via intersystem crossing.
  • the sensitizer can then, for example, transfer an excited state triplet to an upconverter.
  • the sensitizer is a photosensitizer, which includes compounds that can be efficiently excited to an excited triplet excited state (e.g., a first triplet state, a second triplet state), e.g., using light or electromagnetic radiation.
  • the sensitizer absorbs low energy light (relative to the energy of the upconverted light) to produce a triplet state that is subsequently transferred to a triplet upconverter, which may then produce high energy light (relative to light incident to the sensitizer).
  • the sensitizer may reach a triplet state upon excitation, e.g., without the need of an additional external stimulus.
  • the sensitizer transfers its energy state, e.g., a triplet state (or its corresponding triplet state energy) to an upconverter.
  • the upconverter may be configured to upconvert this energy, as further described below, in some instances.
  • sensitizers may excite at least two upconverters, such that the two upconverters may undergo triplet-triplet annihilation.
  • the sensitizer may transfer a triplet state and/or corresponding energy to an upconverter.
  • the sensitizer comprises a metal porphyrin having a formula (I): wherein M is selected from the group consisting of platinum, palladium, manganese, and zinc, wherein R 3 , R 6 , R 9 , R 12 are independently selected from the group consisting of hydrogen, optionally-substituted alkyl, optionally-substituted aryl, and optionally-substituted alkenyl, and wherein R 1 , R 2 , R 4 , R 5 , R 7 , R 8 , R 10 , and R 11 are independently selected from the group consisting of hydrogen, optionally-substituted alkyl, optionally-substituted aryl, and optionally-substituted alkenyl.
  • the sensitizer comprises formula (I).
  • the sensitizer comprises an optionally-substituted metal porphyrin.
  • the sensitizer comprises a structure: In certain embodiments, the sensitizer is palladium tetraphenyl porphyrin. Other sensitizers are possible. Some non-limiting examples of other sensitizers include, but are not limited to, palladium octabutoxy phthalocyanine (PdOBuPc), platinum tetraphenyltetranaphthoporphyrin (PtTPTNP), palladium(II)-meso-tetraphenyl- tetrabenzoporphyrin (PdTPTBP), [Ru(dmb)3] 2+ (dmb is 4,4’ -dimethyl-2,2’ -bipyridine), 2,3-butanedione (biacetyl), palladium(II) tertraanthraporphyrin (PdTAP), platinum(II)tetraphenyltetrabenzoporphyrin (PtTPBP), palladium
  • the sensitizer transfers a triplet state to an upconverter.
  • upconverter may be used interchangeably with “emitter,” “triplet upconverter,” “annihilator,” and “triplet annihilator.”
  • An upconverter may receive a triplet state and/or a triplet energy from the sensitizer to enter a first excited triplet state of the upconverter.
  • the upconverter in some embodiments, is configured to undergo upconversion (or triplet upconversion).
  • an upconverter may undergo upconversion (i.e., “triplet upconversion,” “annihilation,” “triplet-triplet annihilation,” “fusion,” “triplet fusion,” etc.) when two upconverters in a triplet excited state collide or otherwise combine their energy to produce a higher energy excited state (relative to the individual energies of the excited upconverters), which may then emit a photon of higher energy than the original excitation photon.
  • upconversion i.e., “triplet upconversion,” “annihilation,” “triplet-triplet annihilation,” “fusion,” “triplet fusion,” etc.
  • Two upconverters in an excited triplet state may undergo triplet-triplet annihilation such that one upconverter returns to the ground state (and can, thus, be re-excited by a sensitizer) and the other upconverter may enter a second excited state (e.g. a singlet excited state, SI) and subsequently relax to its ground state, for example, by emitting the upconverted photon (which can be used, for example, for polymerization, or other applications including those described herein).
  • a triplet acceptor with lower triplet energy than the sensitizer or upconverter may be included to remove triplets from the system and shorten the effective triplet lifetimes.
  • this emission is fluorescence.
  • this emission is blue-shifted relative to the excitation light.
  • the fluorescent emission is an anti- Stokes emission.
  • the upconverter comprises a diphenyl anthracene or an optionally-substituted diphenyl anthracene.
  • the upconverter comprise a diphenyl anthracene having a formula (II):
  • R A and R B are independently selected from the group consisting of optionally- substituted alkyl, and optionally-substituted aryl, and wherein the diphenyl anthracene having the formula (II) further comprises at least one heavy atom with an atomic number of at least 17.
  • the upconverter may comprise an anthracene having a formula (IV): wherein Rw, Rx, R Y , and Ry are independently hydrogen or any element with an atomic number of at least 17.
  • an upconverter (e.g., an emitter) comprises one or more structures, such as:
  • the upconverter is a heavy atom- functionalized dihexyl diphenyl anthracene. Other examples are possible.
  • Certain embodiments comprise an ethynyl anthracene having a formula (IV), wherein R c and R° are independently selected from the group consisting of optionally substituted alkyl and optionally substituted silyl.
  • an acceptor comprises formula (IV).
  • alkyl includes straight, branched and cyclic alkyl groups. An analogous convention applies to other generic terms such as “alkenyl”, “alkynyl”, and the like. Furthermore, as used herein, the terms “alkyl”, “alkenyl”, “alkynyl”, and the like encompass both substituted and unsubstituted groups. In certain embodiments, as used herein, “alkyl” is used to indicate those aliphatic groups (cyclic, acyclic, substituted, unsubstituted, branched or unbranched) having 1-20 carbon atoms.
  • Aliphatic group substituents include, but are not limited to, any of the substituents described herein, that result in the formation of a stable moiety (e.g ., aliphatic, alkyl, alkenyl, alkynyl, hetero aliphatic, heterocyclic, aryl, heteroaryl, acyl, nitrido, imino, thionitrido, cyano, isocyano, amino, azido, nitro, hydroxyl, thiol, halo, aliphaticamino, heteroaliphaticamino, alkylamino, heteroalkylamino, arylamino, heteroarylamino, alkylaryl, arylalkyl, aliphaticoxy, heteroaliphaticoxy, alkyloxy, heteroalkyloxy, aryloxy, heteroaryloxy, aliphaticthioxy, heteroaliphaticthioxy, alkylthioxy, hetero alkylthioxy, arylthioxy, heteroaryl
  • alkyl is given its ordinary meaning in the art and refers to the radical of saturated aliphatic groups, including straight-chain alkyl groups, branched-chain alkyl groups, cycloalkyl (alicyclic) groups, alkyl substituted cycloalkyl groups, and cycloalkyl substituted alkyl groups.
  • the alkyl group may be a lower alkyl group, i.e., an alkyl group having 1 to 10 carbon atoms (e.g., methyl, ethyl, propyl, butyl, pentyl, hexyl, heptyl, octyl, nonyl, or decyl).
  • a straight chain or branched chain alkyl may have 30 or fewer carbon atoms in its backbone, and, in some cases, 20 or fewer. In some embodiments, a straight chain or branched chain alkyl may have 12 or fewer carbon atoms in its backbone (e.g., C1-C12 for straight chain, C3-C12 for branched chain), 6 or fewer, or 4 or fewer. Likewise, cycloalkyls may have from 3-10 carbon atoms in their ring structure, or 5, 6, or 7 carbons in the ring structure.
  • alkyl groups include, but are not limited to, methyl, ethyl, propyl, isopropyl, cyclopropyl, butyl, isobutyl, /-butyl, cyclobutyl, hexyl, and cyclochexyl.
  • the alkyl groups employed in the invention contain 1-10 aliphatic carbon atoms. In yet other embodiments, the alkyl, alkenyl, and alkynyl groups employed in the invention contain 1-8 aliphatic carbon atoms. In still other embodiments, the alkyl groups employed in the invention contain 1-6 aliphatic carbon atoms. In yet other embodiments, the alkyl groups employed in the invention contain 1- 4 carbon atoms.
  • Illustrative aliphatic groups thus include, but are not limited to, for example, methyl, ethyl, n-propyl, isopropyl, allyl, n-butyl, sec-butyl, isobutyl, /-butyl, n- pentyl, sec-pentyl, isopentyl, /-pentyl, n-hexyl, sec -hexyl, moieties and the like, which again, may bear one or more substituents.
  • cycloalkyl refers specifically to groups having three to ten, preferably three to seven carbon atoms. Suitable cycloalkyls include, but are not limited to cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, cycloheptyl and the like, which, as in the case of other aliphatic, heteroaliphatic, or hetercyclic moieties, may optionally be substituted with substituents including, but not limited to aliphatic; heteroaliphatic; aryl; heteroaryl; arylalkyl; heteroarylalkyl; alkoxy; aryloxy; heteroalkoxy; heteroaryloxy; alkylthio; arylthio; heteroalky lthio; heteroaryl thio; -F; -Cl; -Br; -I; -OH; -NO2; -CN; -CF ; -CH2CF3
  • aryl is given its ordinary meaning in the art and refers to aromatic carbocyclic groups, optionally substituted, having a single ring (e.g., phenyl), multiple rings (e.g., biphenyl), or multiple fused rings in which at least one is aromatic (e.g., 1,2,3,4-tetrahydronaphthyl, naphthyl, anthryl, or phenanthryl). That is, at least one ring may have a conjugated pi electron system, while other, adjoining rings can be cycloalkyls, cycloalkenyls, cycloalkynyls, aryls and/or heterocyclyls.
  • the aryl group may be optionally substituted, as described herein.
  • Substituents include, but are not limited to, any of the previously mentioned substituents, i.e., the substituents recited for aliphatic moieties, or for other moieties as disclosed herein, resulting in the formation of a stable compound.
  • an aryl group is a stable mono- or polycyclic unsaturated moiety having preferably 3-14 carbon atoms, each of which may be substituted or unsubstituted.
  • “Carbocyclic aryl groups” refer to aryl groups wherein the ring atoms on the aromatic ring are carbon atoms. Carbocyclic aryl groups include monocyclic carbocyclic aryl groups and polycyclic or fused compounds (e.g., two or more adjacent ring atoms are common to two adjoining rings) such as naphthyl groups.
  • the aryl group is a radical of a monocyclic or polycyclic (e.g., bicyclic or tricyclic) 4n+2 aromatic ring system (e.g., having 6, 10, or 14 p electrons shared in a cyclic array) having 6-14 ring carbon atoms and zero heteroatoms provided in the aromatic ring system (“C6 14 aryl”).
  • an aryl group has 6 ring carbon atoms (“Ce aryl”; e.g., phenyl).
  • an aryl group has 10 ring carbon atoms (“Cio aryl”; e.g., naphthyl such as 1-naphthyl and 2-naphthyl). In some embodiments, an aryl group has 14 ring carbon atoms (“Ci4 aryl”; e.g., anthracyl). “Aryl” also includes ring systems wherein the aryl ring, as defined above, is fused with one or more carbocyclyl or heterocyclyl groups wherein the radical or point of attachment is on the aryl ring, and in such instances, the number of carbon atoms continue to designate the number of carbon atoms in the aryl ring system.
  • sil is given its ordinary meaning in the art and refers to the radical of a silicon-containing saturated silane group (e.g., -S1H3) in which zero or one or more of hydrogens has been replaced with an organic group (e.g., alkyl, aryl), including straight-chain silyl groups, branched-chain silyl groups, cyclosilyl groups, alkyl substituted cyclosilyl groups, cycloalkyl substituted silyl groups, and aryl silyl groups.
  • an organic group e.g., alkyl, aryl
  • silyl groups include, but are not limited to, trimethylsilyl (-SiMe3, TMS), triethylsilyl (-SiEt3, TES), triisopropylsilyl (Si(iPr)3, TIPS), tert- butyldimethylsilyl (TBS or TBDMS), and / ⁇ ?/7 -butyldiphcnyl silyl (TBDPS).
  • any of the above groups may be optionally substituted.
  • substituted is contemplated to include all permissible substituents of organic compounds, “permissible” being in the context of the chemical rules of valence known to those of ordinary skill in the art.
  • substituted whether preceded by the term “optionally” or not, and substituents contained in formulas of this invention, refer to the replacement of hydrogen radicals in a given structure with the radical of a specified substituent.
  • substituent When more than one position in any given structure may be substituted with more than one substituent selected from a specified group, the substituent may be either the same or different at every position. It will be understood that “substituted” also includes that the substitution results in a stable compound, e.g., which does not spontaneously undergo transformation such as by rearrangement, cyclization, elimination, etc. In some cases, “substituted” may generally refer to replacement of a hydrogen with a substituent as described herein. However, “substituted,” as used herein, does not encompass replacement and/or alteration of a key functional group by which a molecule is identified, e.g., such that the “substituted” functional group becomes, through substitution, a different functional group.
  • a “substituted phenyl group” must still comprise the phenyl moiety and cannot be modified by substitution, in this definition, to become, e.g., a pyridine ring.
  • the permissible substituents include acyclic and cyclic, branched and unbranched, carbocyclic and heterocyclic, aromatic and nonaromatic substituents of organic compounds.
  • Illustrative substituents include, for example, those described herein.
  • the permissible substituents can be one or more and the same or different for appropriate organic compounds.
  • the heteroatoms such as nitrogen may have hydrogen substituents and/or any permissible substituents of organic compounds described herein which satisfy the valences of the heteroatoms.
  • stable preferably refers to compounds which possess stability sufficient to allow manufacture and which maintain the integrity of the compound for a sufficient period of time to be detected and preferably for a sufficient period of time to be useful for the purposes detailed herein.
  • substituents include, but are not limited to, halogen, azide, alkyl, aralkyl, alkenyl, alkynyl, cycloalkyl, hydroxyl, alkoxyl, amino, nitro, sulfhydryl, imino, amido, phosphonate, phosphinate, carbonyl, carboxyl, silyl, ether, alkylthio, sulfonyl, sulfonamido, ketone, aldehyde, ester, heterocyclyl, aromatic or heteroaromatic moieties, -CF 3 , -CN, aryl, aryloxy, perhaloalkoxy, aralkoxy, heteroaryl, heteroaryloxy, heteroarylalkyl, heteroaralkoxy, azido, amino, halide, alkylthio, nitrido, acylalkyl, carboxy esters, -carboxamido, acyloxy,
  • triplet upconversion (or triplet-triplet annihilation, TTA) may be used to produce light of a higher energy relative to light used to photoexcite the sensitizer or the upconverter.
  • TTA refers to the energy transfer mechanism between two molecules (e.g., two upconverters) in their triplet state, and is related to the Dexter energy transfer mechanism. If TTA occurs between two molecules in their excited states, one molecule transfers its excited state energy to the second molecule, resulting in one molecule returning to its ground state and the second molecule being promoted to a higher excited singlet, triplet, or quintet state.
  • TTA combines the energy of two triplet excited molecules onto one molecule to produce a higher excited state, it may be used to convert the energy of two photons each of a lower energy into one photon of higher energy (i.e., photon upconversion or triplet upconversion, as described herein).
  • a sensitizer i.e., annihilator
  • the sensitizer absorbs a low energy photon and populates its first excited triplet state (Tl) through intersystem crossing.
  • Tl first excited triplet state
  • the sensitizer then transfers the excitation energy to the upconverter, resulting in a triplet excited upconverter and a ground state sensitizer.
  • Two triplet-excited upconverters may then undergo triplet-triplet annihilation, and if a singlet excited state (SI) of the upconverter is populated, fluorescence results in an upconverted photon.
  • SI singlet excited state
  • a heavy atom-functionalized upconverter may slow or prevent two triplet-excited upconverters from colliding and undergoing TTA, thereby slowing the process of TTA and hence avoiding saturation of triplet upconverters until higher powers than in the absence of the same upconverter without the heavy atom functionalization, thus increasing the upconversion threshold of the system.
  • certain embodiments can include heavy atom-functionalized upconverters, such as those described herein.
  • the inclusion of a heavy atom-functionalized upconverter may advantageously allow for an increase in laser power to be used while maintaining a quadratic dependence on the photoluminescence of the upconverter as a function of laser power.
  • a heavy atom- functionalized upconverter may increase the upconversion threshold.
  • the upconversion threshold may, in certain embodiments, refer to the point at which the amount of upconverted light ceases to increase quadratically with input light (e.g., laser light) and begins to increase linearly instead.
  • the a heavy atom- functionalized upconverter or a heavy atom-functionalized auxiliary molecule may act to reduce the number of excited upconverters such that the upconversion (or triplet-triplet annihilation) processes remains second order with respected to the upconverter and that incident light (i.e., photons) may increase the upconversion frequency.
  • the upconversion threshold is the point where the process switches from second order to first order with respect to the upconverter, such that incident light (e.g., laser light) no longer increases the upconversion frequency.
  • the upconversion threshold may be measured by plotting photoluminescence versus input power laser power, as illustrated by the Examples below. Other methods of measuring the upconversion threshold are possible.
  • the acceptor comprises an optionally substituted ethynyl anthracene or diethynyl anthracene.
  • the acceptor is bisphenyl ethynyl anthracene.
  • acceptors may include 9,10-diphenylanthracene (DPA), TIPS-tetracene, tetra-tert-butylperylene, anthracene (An), 2,5-diphenyloxazole (PPO), rubrene, 2-chloro-bis- phenylethynylanthracene (2CBPEA), 9,10-bis(phenylethnyl)anthracene (BPEA), 9,10- bis(phenylethynyl)napthacene (BPEN), perylene, coumarin 343 (C343), 9,10- dimethylanthracene (DMA), pyrene, tert-butylpyrene, and iodophenyl-bearing boron dipyrromethene (BODIPY) derivatives BD-1 and BD-2.
  • DPA 9,10-diphenylanthracene
  • TIPS-tetracene tetra
  • the sensitizer, the upconverter, and/or the acceptor can be present at any suitable amount or concentration.
  • the concentration may be expressed as a molar ratio (and/or a mole fraction) of a sensitizer, upconverter, and/or an acceptor.
  • the ratio of upconverter to sensitizer is 10:1.
  • the ratio of the upconverter to the sensitizer is no more than 100:1, no more than 75:1, no more than 50:1, no more than 25:1, no more than 10:1, no more than 5:1, no more than 3:1, or no more than 1:1. in some cases, the ratio of upconverter to sensitizer is 10:1.
  • the ratio of the upconverter to the sensitizer is at least 100:1, at least 75:1, at least 50:1, at least 25:1, at least 10:1, at least 5:1, at least 3:1, or at least 1:1.
  • more than one sensitizer, more than one upconverter, and/or more than one acceptor may be present in some embodiments.
  • the concentration (of a sensitizer, of an upconverter, of an acceptor, etc.) may be expressed in terms of molar concentration or molarity (M).
  • M molar concentration or molarity
  • the concentration of a sensitizer, an upconverter, and/or an acceptor is at least 5 M, at least 6 M, at least 7 M, at least 8 M, at least 9 M, or at least 10 M.
  • the concentration of a sensitizer, an upconverter, and/or an acceptor is no greater than 10 M, no greater than 9 M, no greater 8 M, no greater than 7 M, no greater than 6 M, or no greater than 5 M.
  • sensitizer, the upconverter, and the acceptor can be present at any suitable amount or concentration, and it should be understood that the concentration of one of these (e.g., as discussed in this paragraph) can be independent of the concentration of the others.
  • the sensitizer, the upconverter, and the acceptor are contained within a liquid, which also may comprise a polymerizable species.
  • a polymerizable species describes a chemical entity capable of undergoing a chemical reaction to produce a polymer, such as plastics, resins, etc.
  • the polymerizable species may be, for example, monomers or other entities that can be polymerized to form a polymer, such as oligomers or other partially-formed polymers.
  • light may be used to cause the polymerizable species to polymerize; that is, the polymerizable entities may be photopolymerizable.
  • the polymerizable entities may be polymerized to form a polymeric solid object.
  • the polymerizable species is a precursor to a polymeric object produced by 3D printing.
  • photons produced by the upconversion of two upconverters is used to caused polymerization of the polymerizable species.
  • upconverters 130 and 140 may interact and/or collide to produce upcoverted photon 150. Photon 150 may then cause the polymerization of polymerizable species 160.
  • either upconverters 130 or 140 (or both) may be in an excited state, excited by, for example, sensitizer 110.
  • a triplet acceptor which can receive triplets from either sensitizer or upconverter can also be included to increase upconversion threshold.
  • the polymerizable species may comprise a resin, such as a 3D printing resin.
  • 3D printing resins include, but are not limited to, thermoplastics and thermo- setting resins. Many of these are commercially available. Specific non-limiting examples include polyamides, polypropylene, ABS, PLA, PVA, PET, PETT, HIPS, nylon, etc. Additional examples of monomers include vinyl monomers, acrylates, styrenic monomers, and the like. In some cases, the monomer has a double bond, e.g., an alkene. A variety of monomers can be used, e.g., for 3D printing. For instance, examples of acrylates include, but are not limited to, methacrylate, methyl methacrylate, polyacrylates, or the like.
  • monomers include, but are not limited to, branched polyethylene glycol; linear polyethylene glycol; polyamides and polyamines such as nylon 6, nylon 6,6-poly(pyromellitic dianhydride-co-4,4'-oxydianiline); polyesters 5 such as poly(ethylene terephthalate, poly(4,4'-methylenebis(phenyl isocyanate)-alt-l,4- butanediol/di(propylene gl yco 1 )/po 1 ycapro 1 actonc) ; poly ethers such as Pluronic®F127, poly(2, 6-dimethyl- 1 ,4-phenylene oxide) ; poly(oxy- 1 ,4-phenylenesulfonyl- 1,4- phenylene); silicones such as poly(dimethylsiloxane); vinyl polymers such as HDPE, poly(acrylonitrile-co-butadiene) acrylonitrile, poly( 1 -(4-
  • the liquid containing components such as the sensitizer, the upconverter, and the acceptor may be any suitable liquid.
  • the liquid may be a solvent, including benzene, toluene, iodobenzene, dichloromethane, acetonitrile, methanol, ethanol, as non limiting examples, or any organic solvent capable of dissolving or suspending the components of the liquid.
  • the liquid may also be transparent in some cases, e.g., so as to allow light of a certain wavelength or a particular range of wavelengths to pass through the liquid in order to, for example, interact with the sensitizer or other component of the liquid.
  • the liquid may help to facilitate polymerization of a polymerizable species. For instance, light or other electromagnetic radiation may be focused on specific regions within the liquid that can be upconverted as discussed herein to cause polymerization of a polymerizable species in the liquid in those regions to occur, e.g., while avoiding or minimizing polymerization in other regions of the liquid.
  • the liquid may be one that is optically transparent for a certain set of wavelengths. For example, in embodiments, the liquid is optically transparent to light of a wavelength of 450 nm. In some embodiments, the liquid is optically transparent to light of a wavelength of 1100 nm.
  • the liquid is optically transparent to a wavelength between 450 nm and 1100 nm (e.g. 455 nm, 460 nm, 465 nm, ..., 1090 nm, 1095 nm).
  • a wavelength between 450 nm and 1100 nm e.g. 455 nm, 460 nm, 465 nm, ..., 1090 nm, 1095 nm.
  • Other wavelengths outside of 450 nm to 1100 nm may also be possible.
  • Optical transparency may be determined, for example, by taking an absorption spectrum.
  • the liquid may have any suitable viscosity.
  • the viscosity is relatively low (e.g., similar to water), although in other cases, the viscosity may be higher.
  • relatively high viscosities may be useful to allow relatively fast polymerization of the polymerizable species to form a polymeric object to occur within the liquid or other material, e.g., without the polymeric object being able to drift too far or too quickly away from its initial position, due to the viscosity of the liquid.
  • the polymerizable species may be polymerized into a solid object while free-floating in a liquid.
  • the viscosity of the liquid may be at least about 1 cP, at least about 3 cP, at least about 5 cP, at least about 10 cP, at least about 30 cP, at least about 50 cP, at least about 100 cP, at least about 300 cP, at least about 500 cP, at least about 1,000 cP, at least about 3,000 cP, at least about 5,000 cP, at least about 10,000 cP, at least about 30,000 cP, at least about 50,000 cP, at least about 100,000 cP, etc.
  • the viscosity may be less than about 300,000 cP, less than about 100,000 cP, less than about 50,000 cP, less than about 30,000 cP, less than about 10,000 cP, less than about 5,000 cP, less than about 3,000 cP, less than about 1,000 cP, less than about 500 cP, less than about 300 cP, less than about 100 cP, less than about 50 cP, less than about 30 cP, less than about 10 cP, less than about 5 cP, less than about 3 cP, etc. Combinations of any of these ranges are also possible.
  • the viscosity of the liquid may be between 10,000 cP and 300,000 cP.
  • a variety of techniques or components may be used within the liquid to increase its viscosity.
  • components that can be added include, but are not limited to, gelatin, xanthan gum or other macromolecules.
  • a polymer of the resin itself may be used to increase the viscosity of the liquid.
  • a component such as polymethacrylate may be added to the liquid to increase its viscosity.
  • a combination of techniques and/or components may be used.
  • methods of 3D printing a polymeric object is provided, e.g., as discussed above.
  • the method includes providing a liquid comprising a polymerizable species, a sensitizer, an upconverter, and an acceptor.
  • polymerization of the polymerizable species may be facilitated using a laser, e.g., to cause upconversion and the production of higher-energy photons that can be used for polymerization.
  • a laser e.g., to cause upconversion and the production of higher-energy photons that can be used for polymerization.
  • one or more lasers are present.
  • An example of such a laser is illustrated by laser 115 in FIG. 1.
  • this laser is a part of a 3D printing device.
  • the laser may be the source of photons, e.g., that can be used to cause photoexcitation of the sensitizer and/or the upconverter.
  • the laser may be focused, and/or may intersect with other lasers to create regions of more and less intense laser light.
  • the laser may have a particular excitation wavelength, e.g., as discussed below.
  • the light or photons produced by upconversion are higher in energy than the excitation wavelength (i.e., its corresponding excitation energy) of the laser.
  • the excitation wavelength i.e., its corresponding excitation energy
  • two, three, four, or more lasers may be present, for example, controlled to focus on a location or region within a liquid.
  • the light may be directed at the upconversion compositions, e.g., such that the resulting upconverted light is able to initiate polymerization.
  • a laser may be the source of the light.
  • the mixture or liquid within a container containing the upconversion materials may be irradiated with light (e.g., laser light) to initiate upconversion and/or to initiate polymerization of the polymerizable species.
  • Suitable wavelengths include, for example, 400 nm to 800 nm, e.g., as the excitation wavelength.
  • upconverted light can be produced locally between 390-500 nm using 532 nm laser light, which is in the range of some common photopolymerization initiators.
  • light can be applied having a range of between 600 nm and 700 nm, or between 600 nm and 650 nm, which can then be upconverted as discussed herein, e.g., producing shorter wavelengths (or equivalently, higher frequencies or energies).
  • the light may be applied using any suitable light or electromagnetic radiation source, such as a laser or other coherent light source.
  • the light source is a laser diode, such as those available commercially.
  • a laser has a characteristic intensity or power density. This intensity or power density can be selected in some cases to match the upconversion threshold (i.e., the value where the upconversion threshold changes from quadratic to linear, from second order to first order).
  • the intensity or power density of the applied electromagnetic radiation applied to the focal point or region to cause polymerization to occur may be less than 5,000 W/cm 2 , less than 3,000 W/cm 2 , less than 2,000 W/cm 2 , less than 1,000 W/cm 2 , less than 500 W/cm 2 , less than 300 W/cm 2 , less than 200 W/cm 2 , less than 100 W/cm 2 , less than 50 W/cm 2 , less than 30 W/cm 2 , less than 20 W/cm 2 , less than 10 W/cm 2 , less than 5 W/cm 2 , less than 3 W/cm 2 , less than 2 W/cm 2 , less than 1 W/cm 2 , less than 500 mW/cm 2 , less than 300 mW/cm 2 , less than 200 mW/cm 2 , less than 100 mW/cm 2 , etc.
  • one, two, or more (i.e., three, four, etc.) laser beams may be focused in at least a portion of a container, e.g., containing a liquid and other components such as those discussed herein.
  • the focus of the laser beams may be altered or moved around within the container, which can be used to define an object, e.g., by causing polymerizable entity within the focus to polymerize to produce the object. It should be understood that the focus need not define a contiguous region.
  • one or more lasers may be turned on and off as necessary to define two, three, four, or more objects within the container.
  • areas surrounding the focus of the lasers may also receive sufficient light to cause polymerization to occur, e.g., using upconversion as discussed herein.
  • the area of a spot created by at least one laser beam is at least 300 nm. In some embodiments, the area of a spot created by at least one laser beam is no greater than 1 mm. In some embodiments, the area of a spot created by at least one laser beam is between 300 nm and 1 mm.
  • a method of 3D printing involves focusing at least one laser beam on at least a portion of the liquid, e.g., a focal region, wherein at least some of the laser beam with a first energy is absorbed by the sensitizer.
  • the sensitizer may absorb a photon.
  • a laser such as laser 115 in FIG. 1 provides the laser beam of first energy 120 to sensitizer 110.
  • substantially no polymerization occurs outside of the focal region of the laser beam in the liquid, e.g., due to the quadratic dependence of the upconverter as a function of laser power. This may advantageously allow for formation of a polymeric object to occur in specified areas while preventing polymerization in other areas, in certain embodiments.
  • the liquid may comprise additional components. Several of these additional components will be described below.
  • the liquid may further comprise a micelle forming agent or micelle-forming molecule.
  • the micelle-forming agent is a surfactant.
  • the micelle-forming agent is oleic acid.
  • the micelle-forming agent may interact with other components comprising the liquid as to form a micelle to encapsulate the components.
  • Non-limiting examples of micelle forming agents include TritonTM X100, Pluronic® F-127, sodium dodecyl sulfate, and bovine serum albumin.
  • a nanocapsule to encapsulate the liquid, e.g., one or more of the sensitizer, the upconverter, and/or the acceptor.
  • the nanocapsule may, in some cases, include a vesicular system made of a membrane or a shell which encapsulates an inner liquid core at the nanoscale.
  • the shell is a silica-based shell (e.g., SiC ).
  • a nanocapsule may contain upconversion materials or molecules (e.g., a sensitizer, an upconverter, an acceptor) that can be used to facilitate photon upconversion.
  • the nanocapsules may be contained within a liquid or other within a container of a 3D printing device, which may also contain polymerizable species, cross-linking agents, photopolymerization initiators, or the like, e.g., as discussed herein.
  • Light focused on the nanocapsules may be upconverted to produce wavelengths sufficient to cause polymerization to occur, e.g., as discussed herein.
  • regions within the liquid may receive some light, that light may not be sufficient to be upconverted, and thus, any polymerizable species in those regions would generally not polymerize.
  • the nanocapsules are typically approximately spherical and may have an average diameter of less than 1 micrometer, e.g., such that the nanocapsules have an average diameter on the order of nanometers.
  • the nanocapsules may have an average diameter of less than about 1 micrometer, less than about 900 nm, less than about 800 nm, less than about 700 nm, less than about 600 nm, less than about 500 nm, less than about 400 nm, less than about 300 nm, less than about 200 nm, less than about 100 nm, less than about 90 nm, less than about 80 nm, less than about 70 nm, less than about 60 nm, less than about 50 nm, less than 40 nm, less than about 30 nm, less than about 20 nm, less than about 10 nm, less than about 5 nm, less than about 3 nm, etc.
  • the nanocapsules may have an average diameter of at 20 least about 5 nm, at least about 10 nm, at least about 20 nm, at least about 30 nm, at least about 40 nm, at least about 50 nm, at least about 60 nm, at least about 70 nm, at least about 80 nm, at least about 90 nm, at least about 100 nm, at least about 200 nm, at least about 300 nm, at least about 400 nm, at least about 500 nm, at least about 600 nm, at least about 700 nm, at least about 800 nm, at least about 900 nm, etc. In some cases, combinations of any of these are also possible.
  • the nanocapsules may have a diameter between or equal to 30 and 40 nm between 50 nm and 100 nm, between 100 nm and 400 nm, or the like.
  • the nanocapsules may be present with a range of sizes or average diameters (i.e., the nanocapsules need not all have precisely the same dimensions), which may include any suitable combination of any of the above-described dimensions.
  • the nanocapsules are smaller than the wavelength of visible light. Nanocapsules having smaller dimensions may be useful in certain embodiments, as they do not substantially interfere with the passage of visible light, thus allowing liquids containing such nanocapsules to appear optically transparent, or to allow visible light to pass without significant scatter.
  • the nanocapsules may comprise a silica (S1O2) shell. This may, for instance, impart some rigidity to the nanocapsules.
  • a shell may be formed, for example, upon reaction of a silane (e.g., 3-aminopropyl triethoxysilane) with a silicate (e.g., tetraethyl orthosilicate).
  • a silane e.g., 3-aminopropyl triethoxysilane
  • silicate e.g., tetraethyl orthosilicate
  • the silica shell may also be crosslinked together in certain embodiments.
  • the silicate may comprise a hydrophilic portion (e.g., methoxy polyethylene glycol tetraethyl orthosilicate), such that upon formation of the silica shell, the nanocapsule comprises an outer portion that is relatively hydrophilic (e.g., comprising polyethylene glycol).
  • a relatively hydrophilic outer portion may, for example, allow dispersion or dissolution of the nanocapsules in a number of different solvents or liquids.
  • the relatively hydrophilic portions e.g., comprising polyethylene glycol units
  • the silicate may comprise a hydrophilic portion (e.g., methoxy polyethylene glycol tetraethyl orthosilicate), such that upon formation of the silica shell, the nanocapsule comprises an outer portion that is relatively hydrophilic (e.g., comprising polyethylene glycol).
  • the relatively hydrophilic portions e.g., comprising polyethylene glycol units
  • the liquid may also optionally contain one or more photopolymerization initiators according to certain embodiments.
  • the initiators may form free radicals or cations upon initiation.
  • photopolymerization initiators but are not limited to, isopropylthioxanthone, benzophenone, 2,2-azobisisobutyronitrile, camphorquinone, diphenyltrimethylbenzoylphosphine oxide (TPO), HCP (1- hydroxycyclohexylphenylketone), BAPO (phenyl bis-2,4,6-(trimethylbenzoyl)phosphine oxide).
  • TPO diphenyltrimethylbenzoylphosphine oxide
  • HCP 1- hydroxycyclohexylphenylketone
  • BAPO phenyl bis-2,4,6-(trimethylbenzoyl)phosphine oxide
  • Other examples include Norrish Type-1 and Norrish Type-2 initiators.
  • the liquid may also contain one or more cross-linking agents that are able to polymerize with the polymerizable species.
  • crosslinking agents include ethylene glycol dimethacrylate, trimethylolpropane triacrylate, divinylbenzene, N,N’-methylenebisacrylamide, etc.
  • the liquid may be contained within a container, and the container may be transparent to light (or other suitable electromagnetic radiation) applied to the liquid.
  • the light may be visible light, ultraviolet light, or other suitable forms of
  • the photon upconversion materials discussed herein are not limited to only 3D printing applications. Other applications, such as photoredox catalysis chemistry or anti-counterfeiting, are also contemplated as well.
  • the nanocapsules may be used to control delivery of high energy light to a sample. For example, laser light may be applied to a sample that is of a relatively low intensity, long wavelength, etc., but due to the presence of the nanocapsules, that light may be upconverted to a shorter wavelength that can induce a photoredox reaction to occur. In this way, the amount of light applied to the sample may be controlled.
  • upconversion may be useful in delivering upconverted short wavelength light further into a reaction than is possible by direct illumination at the same wavelength.
  • the nanocapsules may be contained within a suitable component (e.g., paper, a polymer, a metal, or the like), and the presence of upconversion may be used to determine whether the component is genuine or counterfeit.
  • a suitable component e.g., paper, a polymer, a metal, or the like
  • the presence of upconversion may be used to determine whether the component is genuine or counterfeit.
  • laser light may be applied to the component, and if the material produces emission of light at shorter wavelengths than the excitation wavelengths (for example, due to the presence of the nanocapsules), the component can be identified as being genuine.
  • Photoluminescence as a function of input power for continuous wave illumination was probed at a series of excitation powers to produce the plot shown in FIG. 3. While in the control experiment without any biphenyl ethynyl anthracene, the quadratic regime did not persist past 1 mW of input power, when a saturated solution of bisphenyl ethynyl anthracene is added up to 14 uL per mL, the plot of photoluminescence versus power remains quadratic up to -10 mW. In the context of 3D printing, this formulation may allow printing at ⁇ 10x higher powers without losing contrast between emission from the focused and unfocused parts of our laser beam.
  • Three-dimensional (3D) printing can be used in manufacturing, providing custom parts.
  • stereolithography where layers are patterned sequentially by two-dimensional photopolymerization, has been shown to be particularly successful due to its relatively high resolution and surface finish.
  • the layer-by-layer nature of this process introduces limitations that hinder resin choice, and shape gamut and material quality. Further, the need for support structures in these existing systems often necessitates significant postprocessing.
  • triplet fusion upconversion is utilized to perform volumetric 3D printing by taking advantage of the quadratic nature of photon upconversion, which occurs predominately where light is most intense.
  • the upconversion threshold can be extensively tuned to suit different printing setups. The entire printing process can be performed air-free, opening up new material and geometric opportunities for 3D printing.
  • Three-dimensional (3D) printing also known as additive manufacturing, has received considerable interest as technologies have opened up a variety of applications for the technique.
  • One mode of 3D printing is stereolithography (SLA), where a photopolymer is patterned using a laser or light emitting diode.
  • SLA stereolithography
  • this technique requires photopolymerization to occur at the surface of the printing volume, necessitating layer-by-layer printing.
  • the interfacial nature of this printing technique imparts fundamental limitations on resin choice and shape gamut and often necessitates use of extensive support structures.
  • Triplet fusion upconversion is one approach, as previously discussed elsewhere herein, that can be applied to volumetric 3D printing, an example of which is illustrated in FIG. 4.
  • This process takes advantage of excitonic states in molecules to generate blueshifted anti-Stokes emission, as shown in FIG. 4C.
  • the final upconversion step requires molecular collisions of two excited annihilator triplets, which fuse to form one higher energy annihilator singlet which then emits anti-Stokes shifted light that can be used to drive photopolymerization. Therefore, this process has a quadratic nature due to the requirement for two triplets to meet, yet also has high absorption and requires relatively low light fluences due to the high extinction coefficient of the sensitizer. It is also tunable in both excitation and emission wavelength.
  • Triplet fusion upconversion can be applied to volumetric 3D printing.
  • upconversion may exhibit a threshold behavior where the process crosses over from quadratic to linear above a certain fluence. Achieving control over this threshold value may be important in some cases to applying upconversion to different printing schemes. For example, a single voxel at a time was targeted with a focal point on the order of 100 W/cm 2 . While this operating fluence is enormously smaller than the 10 12 W/cm 2 required for 2PA, it is considerably higher than the threshold value for typical upconversion systems.
  • triplet fusion upconversion relies on high concentrations of strongly absorbing molecules undergoing frequent collisions
  • direct addition of the sensitizer and annihilator to the resin poses severe restrictions; high concentrations of the molecules are needed to dissolve in the 3D printing resin, resulting in excessive attenuation of the input light and limited print volumes, as well as potentially affecting the properties of printed parts.
  • the rate of collision varies with viscosity, and as printing occurs the resin viscosity changes, changing the upconversion threshold and efficiency and thus losing the selectivity of the print.
  • TIPS -anthracene was selected as the annihilator and Pd(II) meso-tetraphenyl tetrabenzoporphine (PdTPBP) was selected as the sensitizer.
  • PdTPBP Pd(II) meso-tetraphenyl tetrabenzoporphine
  • This red-to-blue upconversion system can work with efficiencies of up to 30%.
  • the TIPS -anthracene threshold of 1.7 W/cm 2 .
  • heavy atom-functionalized annihilators were synthesized (e.g., TIPS-anthracene derivatized with an atom with an atomic number of at least 17).
  • the threshold value of a triplet fusion system can be related to the nonradiative triplet decay rate k A and the rate of triplet fusion kn :
  • the triplet recombination rate was focused on in order to increase the threshold by adding heavy atoms to the molecule.
  • acetylation chemistry a series of molecules with heavy atom substitution was prepared, see FIG. 5A, in order to adjust the threshold. This substitution introduces only small differences in emission or absorbance other than a slight redshift, as shown in FIG. 5B and FIG. 9.
  • FIG. 5C the relative upconversion efficiency of each of these emitted molecules is plotted against power density. This relative efficiency is the derivative of the upconverted light versus the input light and should be constant at high powers and linear at low powers. Indeed, this relationship was observed for all five molecules.
  • the measured thresholds range from 1.7 W/cm 2 for unsubstituted TIPS-anthracene all the way up to 283 W/cm 2 for the 2Br-TIPS-anthracene, spanning over two orders of magnitude.
  • a monovoxel excitation source can take advantage of the high threshold of the bromide materials at a focused laser spot, while a large area parallel excitation printer, which normally works with lower excitation intensities, can use the chlorides or even the unsubstituted TIPS-anthracene.
  • upconverting micelles can be prepared using a block copolymer, these materials can be unstable in the resin environment and released their contents, resulting in a loss of upconversion.
  • a nano encapsulation technique was employed that can be dispersed in 3D printing resins without scattering light.
  • the upconversion materials were built using upconverting silica nanocapsules that were substantially durable in water. Due to aggregation of the nanocapsules, these materials sometimes scattered the input laser beam and were not dispersible in resins.
  • a nanocapsule synthesis that incorporated a long PEG chain as a solubilizing ligand on the exterior of the silica shell was used. Details of the optimized synthesis can be found in at least FIG. 6A and Example 3.
  • Silane-terminated PEG which can covalently graft to the nanocapsule, can prevent aggregation over time and allowed the nanocapsules to disperse without scatter in 3D printing resins.
  • Electron microscopy of the resulting upconverting nanocapsules (UCNCs) (FIGS. 6C and 6D) showed uniform capsules approximately 50 nm in diameter. Of particular importance is the stability imparted by the silica shell; to demonstrate this, the nanocapsule solution was diluted from both the initial micelle formation after dropwise addition of (3-aminopropyl)triethoxysilane (APTES) and the final shelled UCNCs at 100:1 in acetone.
  • APTES (3-aminopropyl)triethoxysilane
  • the micelles fall apart, leading to limited upconversion and significant PdTPBP phosphorescence at -800 nm, while the in latter case the bright upconversion from the UCNCs is preserved with minimal phosphorescence, FIG. 6E.
  • the capsules were further able to be dispered in a number of common solvents while maintaining bright upconversion, see FIG. 10.
  • the capsules could be introduced to 3D printing resins. See, for example, Int. Pat. Apl. Pub. No. PCT/US 19/63629, incorporated herein by reference in its entirety.
  • Acrylic acid was used to disperse the capsules in an acrylate-based monomer resin.
  • PETA penentaerythritol tetraacrylate
  • FDM fused deposition modeling
  • TEMPO (2, 2, 6, 6- Tetramethylpiperidin-l-yl)oxyl
  • FIG. 7 A standard yet difficult test of 3D printing systems is the benchmark boat print (often referred to as “Benchy”), shown in FIG. 7.
  • This Benchy print was able to be reproduced at small scales using the liquids and methods described herein.
  • printing could be achieved without any support structures, simplifying post-processing and limiting surface blemishes.
  • FIG. 11 The power and print speed were carefully optimized to prevent “underprinting” and “overprinting”, FIG. 12, to realize high fidelity, reproducible prints, FIG. 7C. Additional examples of the fine details are shown by printing a Harvard logo (FIG. 13).
  • print parts could be produced in a poly ethylene glycol diacrylate (PEGDA)- based resin, opening up this technology towards hydrogel printing for biological applications (see FIG. 14).
  • PEGDA poly ethylene glycol diacrylate
  • this technique can enable printing in resins that cannot be printed in a traditional SLA 3D printing setup, such as those with high viscosity, soft parts, or resins requiring air-free polymerizations techniques.
  • the liquids and methods described herein can print surfaces without steps between layers or support structures. These features suggest promise in printing channels, fine filigree features, and other shapes that may be challenging for traditional macroscale SLA approaches.
  • the ability to tune the threshold behavior over orders of magnitude to facilitate tailoring of these UCNCs to a variety of printing excitation schemes beyond the monovoxel printer demonstrated here are also contemplated, such as projector-based printing approaches. It is also contemplated to combine this technique with recent technological developments in optical parallelization to greatly increase print speeds.
  • liquids and methods described herein show the strength in volumetric, upconversion-nanoparticle-driven 3D printing towards fourth generation manufacturing.
  • EXAMPLE 3 The following example describes the preparation of several upconversion materials (e.g., annihilators), their characterization, and their use in 3D printing systems.
  • upconversion materials e.g., annihilators
  • TIPS -anthracene (9,10-bis((triisopropylsilyl)ethynyl)anthracene) was purchased commercially, and bromo TIPS -anthracene (((2-bromoanthracene-9,10- diyl)bis(ethyne-2,l-diyl))bis(triisopropylsilane)) and dibromo TIPS-anthracene (((2,6- dibromoanthracene-9,10-diyl)bis(ethyne-2,l-diyl))bis(triisopropylsilane)) synthesis have been reported previously.
  • the chloro TIPS-anthracene and dichloro TIPS-anthracene were synthesized according to the same protocol.
  • Chloro TIPS-anthracene (((2-chloroanthracene-9, 10-diyl)bis(ethyne-2, 1 - diyl))bis(triisopropylsilane)).
  • the flask was sealed tight before taking out of the glovebox and heated to 65 °C under Ar environment.
  • a second portion of TEOS (10 mL) was added after 48 hours.
  • a third portion of TEOS (10 mL) and second portion of MPEG-Silane (4 g) were added after 96 hours and 102 hours respectively.
  • the reaction crude was cooled to room temperature, poured into a centrifuge tube, and centrifuged at 7000 rpm in a JA10 rotor on a J2- MC Beckman Coulter centrifuge for one hour at room temperature (18-22 °C), after which the pellet was discarded. The supernatant was further centrifuged at 7000 rpm for 14 hours at room temperature. After the second centrifuge, the paste-like UCNCs (-10 g) were immediately transferred to the glovebox.
  • the solution was mixed in a LlackTek SpeedMixer at 1000 rpm for 5 minutes to remove bubbles.
  • the resin was then poured into 4 mL cuvettes, mixed in the SpeedMixer again to remove bubbles, and used immediately for printing.
  • the resin was then poured into 4 mL cuvettes, mixed in the SpeedMixer again to remove bubbles, and used immediately for printing.
  • Printing The printing is performed on a custom built, highly modified Kossel Delta configuration reprap printer, with many modifications gathered from Haydn Huntley (https://www.kosselplus.com/).
  • the firmware run on the printer is a fork of Reprap: RepRapFirmware-dc42, available at https://github.com/dc42/RepRapFirmware, and the printing electronics are the Duet 2 Wifi controller (https://www.duet3d.com/DuetWifi).
  • STL files are sliced in Simplify3D to generate gCode inputs to the printer.
  • the printing is powered by a Thorlabs S4FC637 637 nm 70 mW fiber coupled laser.
  • the laser is collimated with a 30 mm focal length lens then fed into a 50X Mitutoyo Plan Apochromat Objective where it is focused into the resin.
  • the entire optical system is moved by the printer in three dimensions to generate the print. Power was adjusted as a function of height to maintain consistent voxel power across the height of the print.
  • the final part was rinsed twice in propylene glycol diacetate to remove unreacted resin before a final cure with a 405 nm laser pointer. Control resins without upconversion nanocapsules showed no printing at all.
  • FIG. 8 images are of a dilute stock solution of PdTPBP and Br- TIPS- anthracene.
  • the quadratic voxel was generated with 637 nm light.
  • the linear voxel was generated from a fiber coupled 365 nm LED coupled into the same optical path.
  • the linear cuvette was diluted by a factor of 2 relative to the quadratic cuvette to better show the entire voxel.
  • FIG. 10 images are taken with the same camera with the sample excited in free space by a 635 nm laser from the right through a 550 nm short pass filter.
  • F127 micelles were made as discussed previously with the sole change that Br-TIPS- anthracene was used as the annihilator. Capsules and micelles were diluted 30: 1 in the specified resin. The tap water was taken directly from a sink and left uncapped for 20 minutes before the image was taken. All other cuvettes were mixed in the glovebox. Photoluminescence spectra were recorded with an Ocean Optics QE Pro. Absorption spectra were taken on a Cary-5000 UV-Vis spectrometer. For intensity dependence, incident laser intensity was measured with a calibrated Si photodetector from Newport and varied using ND filters. The emission intensity was measured with the QE Pro spectrometer and integrated. No variation in emission shape or time was observed throughout the measurement.
  • the spot size was measured by moving a razor blade through the spot with a micrometer.
  • SEM image was captured by using an in-lens (immersion lens) detector on Supra55VP Field Emission Scanning Electron Microscope (FESEM) at 10 keV.
  • TEM image was captured by JEOL-2100 HR-TEM operated at 200 kV. The sample was drop casted on a polymer coated Cu grid. The image in Fig. 3D was taken with an EOS Rebel T6i through Thorlabs LG4 laser safety glasses that have a 400 - 600 nm bandpass. 1 g of capsules was dissolved in 2 mL of acrylic acid and then diluted with -800 mL of acetone. All images are unedited.
  • a reference to “A and/or B,” when used in conjunction with open-ended language such as “comprising” can refer, in one embodiment, to A without B (optionally including elements other than B); in another embodiment, to B without A (optionally including elements other than A); in yet another embodiment, to both A and B (optionally including other elements); etc.
  • the phrase “at least one,” in reference to a list of one or more elements, should be understood to mean at least one element selected from any one or more of the elements in the list of elements, but not necessarily including at least one of each and every element specifically listed within the list of elements and not excluding any combinations of elements in the list of elements.
  • This definition also allows that elements may optionally be present other than the elements specifically identified within the list of elements to which the phrase “at least one” refers, whether related or unrelated to those elements specifically identified.
  • “at least one of A and B” can refer, in one embodiment, to at least one, optionally including more than one, A, with no B present (and optionally including elements other than B); in another embodiment, to at least one, optionally including more than one, B, with no A present (and optionally including elements other than A); in yet another embodiment, to at least one, optionally including more than one, A, and at least one, optionally including more than one, B (and optionally including other elements); etc.
  • Some embodiments may be embodied as a method, of which various examples have been described.
  • inventions may be constructed in which acts are performed in an order different than illustrated, which may include different (e.g., more or less) acts than those that are described, and/or that may involve performing some acts simultaneously, even though the acts are shown as being performed sequentially in the embodiments specifically described above.

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Abstract

La présente invention concerne d'une manière générale des articles et des procédés pour augmenter le seuil de conversion-élévation de triplets, par exemple, en utilisant un convertisseur-élévateur d'excitons triplets fonctionnalisé par des atomes lourds. Certains modes de réalisation concernent, par exemple, des articles et des procédés qui font appel à un sensibilisateur de triplets et à un convertisseur-élévateur fonctionnalisé par des atomes lourds pour produire des photons à conversion-élévation (par exemple, de la lumière d'une seconde énergie).<i /> La lumière peut être utilisée pour polymériser une espèce polymérisable. D'autres configurations de conversion-élévation peuvent également être utilisées dans d'autres modes de réalisation. Dans certains cas, cela peut permettre d'obtenir une véritable impression 3D en raison d'une régulation améliorée de l'absorption de lumière, par exemple, sans avoir besoin d'« imprimer » sur une base couche par couche.<i />
PCT/US2020/053765 2019-10-04 2020-10-01 Convertisseurs-élévateurs fonctionnalisés par des atomes lourds pour augmenter des seuils de conversion-élévation pour l'impression 3d WO2021067577A1 (fr)

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Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20130171060A1 (en) * 2009-03-18 2013-07-04 Immunolight, Llc Up and down conversion systems for production of emitted light from various energy sources
US20170087920A1 (en) * 2015-09-25 2017-03-30 Imperial Toy Llc Device for dispensing chemiluminescent solution
US20180311353A1 (en) * 2015-07-02 2018-11-01 Children's Medical Center Corporation Triplet-triplet annihilation-based upconversion

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20130171060A1 (en) * 2009-03-18 2013-07-04 Immunolight, Llc Up and down conversion systems for production of emitted light from various energy sources
US20180311353A1 (en) * 2015-07-02 2018-11-01 Children's Medical Center Corporation Triplet-triplet annihilation-based upconversion
US20170087920A1 (en) * 2015-09-25 2017-03-30 Imperial Toy Llc Device for dispensing chemiluminescent solution

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