Stereolithographic 3D printing of foam materials containing hollow microspheres

Abstract

In some embodiments, the present disclosure relates to a method of forming a three-dimensional (3D) printed resin. In some embodiments, the method includes combining a mesogen with a solvent and a stabilizer to form a mixture, heating the mixture, adding a spacer to the mixture, and adding a catalyst to the mixture. In some embodiments, the method further includes mixing a photoinitiator with the mixture. In some embodiments, the method further includes mixing a filler with the mixture. In some embodiments, the method further includes adjusting the viscosity of the mixture. In some embodiments, the method further includes mixing a thermal initiator with the mixture. In further embodiments, the present disclosure relates to a method of forming a material utilizing a 3D printed resin, and a 3D foam device comprised of a porous material printed into a form by the forming method.

Description

[Technical field]

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS This application claims priority to U.S. Provisional Application No. 63 / 306,528, filed February 4, 2022, the entire contents of which are incorporated by reference.

[0002] The present disclosure relates generally to three-dimensional printing, and more specifically, but not exclusively, to stereolithographic three-dimensional printing of foam materials containing hollow microspheres. [Background technology]

[0003] This section provides background information to facilitate a better understanding of the various aspects of the present disclosure. It should be understood that statements in this section of the document are to be read in this light, and not as admissions of prior art.

[0004] Currently, many methods exist for making conventional polymer foams. These methods may include, for example, gas foaming or blow molding, phase separation methods, high internal phase emulsion methods, breath figure methods, or direct templating methods. Additionally, various methods may incorporate the use of foamable or foamed microspheres. However, these conventional porous polymer manufacturing methods lack design flexibility and customizability. For example, molds are usually required to create the desired shape, or post-processing (e.g., machining) is required. Furthermore, some of these methods require special manufacturing conditions (e.g., high temperature or pressure). In view of the foregoing, there is a need to develop methods that improve design flexibility and customizability and minimize or eliminate post-processing, as well as methods that allow manufacturing under easily maintainable conditions (e.g., ambient conditions).

[0005] Summary of the Invention This Summary is provided to introduce a selection of concepts that are further described below in the Detailed Description. This Summary is not intended to identify key features or essential features of the claimed subject matter, nor should it be used as an aid in limiting the scope of the claimed subject matter.

[0006] In one embodiment, the present disclosure relates to a method of forming a three-dimensional (3D) printing resin. In some embodiments, the method includes forming a mixture by combining a mesogen with a solvent and a stabilizer, heating the mixture to improve miscibility, adding a spacer to the mixture, and adding a catalyst to the mixture. In some embodiments, the method includes mixing a photoinitiator into the mixture, heating the mixture, and remixing the mixture until the photoinitiator is completely dissolved. In some embodiments, the method further includes mixing a filler into the mixture until the filler is uniformly distributed throughout the resin, and allowing the mixture to cool to room temperature. In some embodiments, the filler is a microsphere. In some embodiments, the method further includes adjusting the viscosity of the mixture. In some embodiments, adjusting the viscosity includes adding a second solvent to the mixture. In some embodiments, the method further includes mixing a thermal initiator into the mixture.

[0007] In another embodiment, the present disclosure relates to a printing resin comprised of a mixture formed by the disclosed method of forming a three-dimensional (3D) printing resin.

[0008] In additional embodiments, the present disclosure relates to a method of forming (e.g., printing) a material. In some embodiments, the method includes pouring a three-dimensional (3D) printing resin formed by the methods of the present disclosure into a tank of a 3D printer and printing the material. In some embodiments, the printing utilizes ultraviolet (UV) light to initiate reaction of components in the 3D printing resin. In some embodiments, the printing utilizes heat to initiate reaction of components in the 3D printing resin.

[0009] In further embodiments, the present disclosure relates to three-dimensional (3D) foam devices constructed from porous materials printed into forms by the printing methods (e.g., forming materials) of the present disclosure.

[0010] A more complete understanding of the subject matter of the present disclosure can be obtained by reference to the following detailed description in conjunction with the accompanying drawings, in which: [Brief description of the drawings]

[0011] [Figure 1] 1 shows an overview of stereolithography (or digital light processing) using microspheres (e.g., hollow microspheres) according to an embodiment of the present disclosure. [Diagram 2] A comparison of EXPANCEL® silicone and EXPANCEL® liquid crystal elastomer (LCE) is shown. [Diagram 3] The LCE material softens as it warms from room temperature to body temperature. [Figure 4] 1 is an example of a material response to cyclic loading, showing displacement and load over time. [Diagram 5] Examples of LCEs that have been tested for glassy nematic, rubbery nematic, and isotropic properties are presented (measuring elastic modulus and dissipation as a function of temperature). [Figure 6]A direct comparison of dissipation between conventional polymer networks and LCEs is shown, with temperature normalized to the glass transition temperature of each polymer. [Figure 7] Mesogen rotation is shown. [Figure 8] 3 shows dynamic mechanical analysis (DMA) curves for 3D printing resins of the present disclosure. [Figure 9] A comparison of tan ∂ between LCE and silicone is shown. [Figure 10] LCEs exhibit improved damping properties compared to conventional viscoelastic foams. [Figure 11] Durometer measurements are shown for silicone, printed solid LCE, and printed LCE foam.

[0012] Detailed Description It should be understood that the following disclosure provides many different embodiments or examples for implementing different features of various embodiments. To simplify the disclosure, specific examples of components and configurations are described below. These are, of course, merely examples and are not intended to be limiting. The section headings used herein are for editorial purposes only and should not be construed as limiting the subject matter described herein.

[0013] Currently, there are many types of three-dimensional (3D) printed "foams". Generally, these "foams" can either use technologies that allow a 3D printer to print an object where the material itself is porous, or technologies that allow a 3D printer to print an object where the structure is porous (i.e., lattice), but the material itself is solid. The latter is generally referred to as digital foam. In view of the desirability of increased design flexibility and customizability, the methods and compositions of the present disclosure generally relate to methods where the material itself is porous. Since hierarchical design typically uses porous materials to print porous structures, the methods and compositions of the present disclosure seek to leverage the capabilities of 3D printing to print foams using porous materials.

[0014] Various 3D printing methods are currently available. For example, nozzle-based printing and powder-based printing are often used. Nozzle-based printing typically involves extruding an ink, resin, or filament through a nozzle, whereas powder-based printing typically involves fusing powder particles together with heat. These methods are colloquially known as direct ink writing, or fused filament fabrication, and selective laser sintering, or binder jetting, respectively. However, these methods are inherently porous and can suffer from various challenges, such as a lack of design flexibility and customizability.

[0015] Thus, the present disclosure generally relates to resin-based printing, also known as stereolithography (or digital light processing), for increased design flexibility and customizability. Resin-based printing typically utilizes a viscous liquid resin that is cured layer-by-layer with ultraviolet (UV) light. This technique typically produces solid components and was originally designed to avoid porosity in materials. Thus, most resin-based printing methods are not used to print porous materials. However, the method disclosed herein utilizes a resin-based printing approach to produce porous materials that achieve a wide range of porosity.

[0016] As will be discussed in more detail below, the present disclosure allows for increased design flexibility and customizability available in resin-based printing while maintaining optimal porosity typically only available in nozzle-based and powder-based printing processes. In addition, as will be discussed in more detail below, the method of the present disclosure allows for the use of microspheres to form liquid crystal elastomer (LCE) viscous resins for use in stereolithography printing. In general, the high viscosity of liquid crystal elastomer resins prevents the spheres from settling to the bottom of the liquid crystal elastomer resin or from separating from the resin. In addition, the exact chemistry of the resin must be considered so that the resin does not dissolve the shell of the microspheres (e.g., when using thermoplastic microspheres).

[0017] Such resins formed by the present methods can be utilized to form highly customizable materials, require minimal post-processing, can be manufactured at room temperature, and have easily controlled porosity. Generally, methods according to the present disclosure can include one or more of the following general steps, as discussed below: (1) resin reaction (illustratively, a first state reaction which may include, for example, a Michael addition reaction); (2) preparation; (3) mixing in microspheres; (4) viscosity adjustment; (5) printing; and (6) post-processing.

[0018] FIG. 1 shows a schematic stereolithography (or digital light processing) overview using microspheres (e.g., hollow microspheres) according to an embodiment of the present disclosure. While stereolithography and digital light processing printing techniques were originally designed to avoid porosity in materials, the disclosed method can be used to create compositions and materials with tailored porosity, unlike similar processes that utilize other photocurable materials (e.g., photoreactive ligand inorganic cores: PLICs). For example, the disclosed method can achieve a wide porosity range, and can achieve porosity levels below 60%, unlike salt leeching techniques.

[0019] As discussed in more detail below, one aspect of achieving these results is to consider the appropriate size of the microspheres for each application, for example, the diameter of the microspheres should be smaller than the layer thickness of the printer, e.g., for a layer that is 100 μm thick, microspheres of about 20-80 μm are used.

[0020] In general, the disclosed methods can be used to form a variety of materials and components, for example in the form of printed foams. Foams printed using the disclosed methods and compositions can form closed-cell liquid crystal elastomers. Additionally, the printed foams can be printed as solid parts (e.g., solid ear molds, or solid inner ear molds) or as macroporous structures. Furthermore, 3D printing can be used to engineer macroporosity into open or closed cells. Additionally, the printed foams can be used to print printed components and materials that exhibit a combination of solid and porous properties. For example, ear molds can be formed with a solid exterior and a lattice structure on the interior.

[0021] While printed foams can be used to print a variety of components, sound deadening components can be greatly improved with the methods and compositions of the present disclosure, given the improved acoustic damping properties of liquid crystal elastomers. Porosity in general improves damping in materials.

[0022] FIG. 2 shows a comparison between silicone with EXPANCEL® and LCE with EXPANCEL®. The liquid crystal elastomer has improved acoustic attenuation between 4000 and 8000 Hz (the magnitude of the values ​​is different because the thickness of the sample is different from the previous figure). In addition, the liquid crystal elastomer foam of the present disclosure softens at body temperature, from approximately 20 MPa at room temperature to approximately 10 MPa at body temperature (FIG. 3). Silicone is unaffected by temperatures between room temperature and body temperature. This property can improve user comfort, for example, for ear molds or devices using ear molds.

[0023] Additionally, other benefits may be achieved by utilizing microspheres in the methods and compositions of the present disclosure. The addition of microspheres may improve the comfort of the device. For example, foam is a compressible material, which allows the earmold to be compressed to insert and seat into the ear canal, allowing the earmold to expand gently.

[0024] Generally, the storage modulus (E') and tan δ are calculated by the following equations: TIFF2025505016000002.tif14170In the formula, δ is defined as the phase lag between two sine waves, the load (stress) wave and the displacement (strain) wave (measured in radians). Perfectly elastic materials, such as metals, ceramics, and rigid plastics, are in phase and have values ​​of ∂ and tan ∂ near zero. Mathematically, this is expressed as E″ (or loss modulus) equal to 0, meaning all the energy is stored elastically. Figure 4 shows an example of displacement and load over time.

[0025] Figure 5 shows an example of a nematic liquid crystal elastomer that was tested. The glassy region of the polymer behaves like a conventional polymer network. The liquid crystal (i.e., nematic) region shows an elevated tan ∂ (bottom of the curve). The isotropic region shows a return of tan ∂ to its normal low value (near 0) and behaves like a conventional polymer network. The storage modulus transitions from nematic to isotropic, T i Note that there is a slight dip (dip) at

[0026] Figure 6 shows a direct comparison of a conventional polymer network with a liquid crystal elastomer ("amorphous network" should be interpreted as a conventional elastomer). These polymers have similar crosslink density and structure, as shown by the similar first half of the tan ∂ function and the peak of the tan ∂ function. g One distinguishing feature of liquid crystal elastomers over conventional elastomers is that tan ∂ increases with increasing temperature above T g The key point is that the rate of increase in the supply of electricity remains elevated above 100%.

[0027] Figure 7 shows mesogen rotation. Liquid crystals have long range order in their long axes (similar to conventional crystals). However, unlike conventional crystals, mesogens are not fixed in a particular position but are restricted to a configuration. Mesogens can rotate to accommodate stress while retaining their orientation. This rotation within the system causes the T g This allows for enhanced energy dissipation beyond the

[0028] Figure 8 shows the dynamic mechanical analysis (DMA curve) for the 3D printing resin of the present disclosure. According to Figure 8, the glass transition temperature is around 0°C, which means that the polymer is considered elastic around body temperature. The tan ∂ remains elevated around body temperature. The elevated tan ∂ is favorable for vibration isolation and sound damping.

[0029] Figure 9 shows a comparison of the tan ∂ of liquid crystal elastomers to silicone. The liquid crystal elastomers exhibit a much higher tan ∂ compared to traditional elastomers (silicone) used in cochlear molds.

[0030] In terms of acoustic attenuation, Figure 10 shows that the liquid crystal elastomers have improved attenuation over conventional viscoelastic foams due to the extended and broader tan ∂ behavior. The liquid crystal elastomer foams have improved attenuation compared to solid liquid crystal elastomers due to the relatively more scattering / reflection of sound waves within the material.

[0031] In general, LCEs and LCE foams have good sound attenuation. As the tan ∂ of a material increases, so does the sound attenuation performance of the material. For many materials, the glass transition temperature (i.e., the peak of tan ∂) is tuned to the operating temperature to maximize its sound attenuation. However, at the glass transition temperature, the material is not as soft / flexible as materials heated above the glass transition temperature. Silicone (which has a very low modulus) is well above the glass transition temperature, but has a very low value of tan ∂. Figures 5, 6, 7, and 9 show that LCEs are ideal acoustic attenuators because they are able to maintain high tan ∂ values ​​above the glass transition temperature, which is a unique combination of properties. By utilizing 3D printed foamed LCEs, very low durometer / stiffness materials (Figure 11) are created with optimized sound attenuation.

[0032] FIG. 11 shows durometer measurements (i.e., measurements of hardness) for silicone, printed solid liquid crystal elastomer, and printed foam liquid crystal elastomer. Traditional silicone cochlear materials do not exhibit any viscoelastic behavior. For example, when the durometer is measured, the viscoelastic behavior remains constant. Liquid crystal elastomer materials exhibit a durometer that can relax over time. This can improve comfort as the mold is allowed to relax within the ear canal. Foam liquid crystal elastomers exhibit a lower durometer than solid liquid crystal elastomers.

[0033] In one embodiment, the present disclosure relates to a method for forming a three-dimensional (3D) printed resin. In some embodiments, the method includes forming a mixture by combining a mesogen with a solvent and a stabilizer, heating the mixture to improve miscibility, adding a spacer to the mixture, and adding a catalyst to the mixture. In some embodiments, the heating can be performed at a temperature between 80-100° C.

[0034] In some embodiments, the mesogen is a reactive mesogen. In some embodiments, the mesogen can be selected from the group consisting of 2-methyl-1,4-phenylene bis(4-(3-(acryloyloxy)propoxy)benzoate), 4-[[[4-[(1-oxo-2-propenyl)oxy]butoxy]carbonyl]oxy]benzoic acid 2-methyl-1,4-phenylene ester, 4-[4-[(1-oxo-2-propenyl)oxy]butoxy]-,2-methyl-1,4-phenylene ester, 2-methyl-1,4-phenylene bis(4-((6-(acryloyloxy)hexyl)oxy)benzoate), 4,4′-bis(acryloyl)biphenyl, 4-(6-(acryloyloxy)hexyloxy)phenyl 4-(6-(acryloyloxy)hexyloxy)benzoate, Mesogens may include, but are not limited to, acrylic acid 6-[4'-(6-acroyloxy-hexyloxy)biphenyl-4-yloxy]hexyl ester, 1,4:3,6-dianhydride-D-glucitol bis[4-[[4-[[[4-[(1-oxo-2-propenyl)oxy]butoxy]carbonyl]oxy]benzoyl]oxy]benzoate], 1,4-phenylene bis[4-[6-(acroyloxy)hexyloxy]benzoate], 1,4-phenylene bis(4-((acroyloxy)methoxy)benzoate), [4-(3-prop-2-enoyloxypropoxy)phenyl]4-(3-prop-2-enoyloxypropoxy)benzoate, and combinations thereof. In some embodiments, the solvent may include, but is not limited to, toluene, dichloromethane, acetone, chloroform, tetrahydrofuran, benzene, hexane, and combinations thereof. In some embodiments, the stabilizer may include, but is not limited to, dibutylhydroxytoluene (butylated hydroxytoluene; BHT), 1,3,5-trimethyl-2,4,6-tris(3,5-di-tert-butyl-4-hydroxybenzyl)benzene, hydroquinone monomethyl ether, 2-(2-hydroxyphenyl)-2H-benzotriazole, benzophenone, bisphenylene, and combinations thereof.In some embodiments, the spacer can include, but is not limited to, 2,2'-(ethylenedioxy)diethanethiol (EDDET); ethane-1,2-dithiol, 1,3-propanedithiol, 1,6-hexanedithiol, 1,9-nonanedithiol, 1,11-undecanedithiol, poly(ethylene glycol)dithiol, tetra(ethylene glycol)dithiol, hexa(ethylene glycol)dithiol, 1,4-benzenedimethanethiol, N-butylamine, ethylene glycol bis(3-mercaptopropionate), and combinations thereof. In some embodiments, the catalyst can include, but is not limited to, dipropylamine (DPA), hexylamine, triethylamine, tetramethyl-1,8-naphthalenediamine, 1,8-diazabicyclo[5.4.0]undec-7-ene, 1,5-diazabicyclo[4.3.0]non-5-ene, tripropylphosphine, dimethylphenylphosphine, methyldiphenylphosphine, pentamethyldiethylenetriamine, and combinations thereof.

[0035] In some embodiments, the catalyst initiates a chemical reaction with the components in the mixture. In some embodiments, after the addition of the catalyst, the mixture is sealed in a container and transferred to a furnace. In some embodiments, the container is heated at approximately 70° C. for 8 hours or more. In some embodiments, the above process marks the end of the first stage reaction.

[0036] In some embodiments, the method further includes mixing a photoinitiator with the mixture, heating the mixture, and remixing the mixture until the photoinitiator is completely dissolved.

[0037] In some embodiments, the photoinitiator may include, but is not limited to, phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide (PPO), 2-hydroxy-2-methylpropiophenone, diphenyl(2,4,6-trimethylbenzoyl)phosphine oxide, bis(2,4,6-trimethylbenzoyl)-phenylphosphine oxide), 2,2-dimethoxy-2-phenylacetophenone, and combinations thereof. In some embodiments, the photoinitiator is added after the above steps to prevent pre-photopolymerization of the print resin. In some embodiments, the photoinitiator may be mixed by vigorous shaking and / or stirring for several minutes. In some embodiments, the mixture with the photoinitiator may be heated to approximately 70° C. In some embodiments, remixing is performed to ensure complete dissolution of the photoinitiator.

[0038] In some embodiments, a thermal initiator may be added to the mixture. In some embodiments, a thermal initiator may be used to aid in cross-linking of the resin. In some embodiments, a photoinitiator is used to form the features through printing, and a thermal initiator is used to ensure complete cross-linking. In some embodiments, heat is utilized to cure each layer.

[0039] In some embodiments, the thermal oxidant can include, but is not limited to, peroxides, hydroperoxides, ketone peroxides, dialkyl peroxides, peroxyketals, peroxyesters, monoperoxycarbonates, diacyl peroxides, peroxydicarbonates, tert-butylperoxy-2-ethylhexanoate, n-butyl-4,4-di(tert-butylperoxy)valerate, 1,1-di(tert-butylperoxy)-3,3,5-trimethylcyclohexane, 1,1-bis(tert-amylperoxy)cyclohexane, 1,1-bis(tert-butylperoxy)cyclohexane, t-butylperoxyneodecanoate, tert-butylperoxybenzoate, and combinations thereof.

[0040] In some embodiments, a thermal initiator is utilized in place of a photoinitiator. In some embodiments, a thermal initiator is utilized along with a photoinitiator. In some embodiments, the resins of the present disclosure may be utilized to make thermally conductive composites.

[0041] In some embodiments, the method further comprises mixing the filler into the mixture until the filler is uniformly distributed throughout the resin, and allowing the mixture to cool to room temperature. In some embodiments, the mixing may be performed by vigorous shaking and / or stirring until the filler is uniformly distributed throughout the mixture. In some embodiments, the room temperature is between approximately 22-25°C.

[0042] In some embodiments, the disclosed method may include a porous lattice. In some embodiments, the filler may include, but is not limited to, microspheres, EXPANCEL® 920 DE 80d30, EXPANCEL® 920 DE 40d30, EXPANCEL® 031 DU40, DUALITE® E135-025D, DUALITE® U015-135D, Kureha m330, Kureha m430, and combinations thereof. In some embodiments, the filler may be a microsphere. In some embodiments, the microsphere is approximately 80 microns in diameter. In some embodiments, the microsphere is less than 80 microns in diameter. In some embodiments, the microsphere has a diameter that is determined by the height of the layer during printing. For example, in some embodiments, if each layer is 100 microns, the diameter of the microsphere will be determined by the height of the layer (e.g., a height of 200 microns in diameter is not allowed). In some embodiments, the microspheres occupy less than about 75% by volume (e.g., less than about 74% by volume). In some embodiments, the microspheres occupy between about 5-30% by volume. In some embodiments, the microspheres can improve the recovery of materials formed with 3D printing resins. In some embodiments, the microspheres are already expanded when placed in the mixture. In some embodiments, the microspheres are expanded after the printing process is completed. In some embodiments, the microspheres are pre-expanded or are not expanded when heated.

[0043] In some embodiments, the method further includes adjusting the viscosity of the mixture by adding a second solvent to the mixture. In some embodiments, the adjusted viscosity can be between approximately 2000-3000 cp. In some embodiments, adding microspheres to the mixture increases the viscosity of the mixture. In some embodiments, the second solvent can further disrupt the liquid-crystal order, which provides better properties, such as sound attenuation. In some embodiments, this further reduces the viscosity of the mixture.

[0044] In some embodiments, the second solvent can include, but is not limited to, toluene, dichloromethane, acetone, chloroform, tetrahydrofuran, benzene, hexane, and combinations thereof.

[0045] In some embodiments, the method further comprises mixing a thermal initiator into the mixture. In some embodiments, the thermal initiator may include, but is not limited to, peroxides, hydroperoxides, ketone peroxides, dialkyl peroxides, peroxyketals, peroxyesters, monoperoxycarbonates, diacyl peroxides, peroxydicarbonates, tert-butylperoxy-2-ethylhexanoate, n-butyl-4,4-di(tert-butylperoxy)valerate, 1,1-di(tert-butylperoxy)-3,3,5-trimethylcyclohexane, 1,1-bis(tert-amylperoxy)cyclohexane, 1,1-bis(tert-butylperoxy)cyclohexane, t-butylperoxyneodecanoate, tert-butylperoxybenzoate, and combinations thereof.

[0046] In another embodiment, the present disclosure relates to a printing resin comprised of a mixture formed by the disclosed method of forming a three-dimensional (3D) printing resin.

[0047] In further embodiments, the present disclosure relates to a method of forming (e.g., printing) a material. In some embodiments, the method includes pouring a three-dimensional (3D) printing resin formed by the method of the present disclosure into a tank of a 3D printer and printing the material. In some embodiments, for printing, ultraviolet (UV) light is utilized to initiate a reaction of components in the 3D printing resin. In some embodiments, the reaction is a second stage reaction. In some embodiments, the 3D printing resin is UV cured layer by layer. In some embodiments, the printing is performed at ambient conditions.

[0048] In some embodiments, the UV light converts the low molecular weight 3D printing resin into a crosslinked liquid crystal elastomer. In some embodiments, the method further includes adding a color dye to the 3D printer tank before printing the material.

[0049] In some embodiments, the method further includes a post-treatment. In some embodiments, the post-treatment may include, but is not limited to, washing the material in a solvent, post-curing the material in a UV oven, drying the material in a vacuum oven, mechanical buffing, dip coating (e.g., dipping in a similar LCE resin or silicone resin and curing a thin glossy layer), and combinations thereof. In some embodiments, the post-crosslinking ensures complete polymerization of the material and / or eliminates the "tackiness and / or adhesion" of the material (e.g., when using post-crosslinking in a UV oven). In some embodiments, the post-treatment may include activating a thermal initiator for the post-cure. In some embodiments, the thermal initiator may be 2,2'-azobis(2-methylpropionitrile), tert-butyl peroxide, benzoyl peroxide, cumene hydroperoxide, and combinations thereof.

[0050] In some embodiments, post-treatment includes drying the material in a vacuum oven. In some embodiments, the drying may include, for example, heating the material in a vacuum oven at 70° C. for approximately 24 hours, and then increasing the temperature of the vacuum oven to 120° C. until the material is completely dry. In some embodiments, the pressure in the vacuum oven is approximately 0.08 MPa. In some embodiments, a desiccant is placed in the vacuum oven to assist with absorbing moisture. In some embodiments, when the material is washed in a solvent, the solvent is gradually or slowly removed. For example, in some embodiments, the temperature is gradually increased from a low temperature to a high temperature to avoid cracking the material as the solvent is removed.

[0051] In some embodiments, a design of the material is prepared and loaded into the 3D printer. In some embodiments, the design takes into account the shrinkage of the material. For example, in some embodiments, the material may shrink by approximately 20% after post-processing. Thus, the design may take into account the approximate amount of shrinkage.

[0052] In some embodiments, the material is printed into forms that may include, but are not limited to, ear molds, sound insulation clips, acoustic panels and baffles, ear cushions and covers for headphones, anti-vibration pads, ear tips for earbuds, packing bumpers, vibration isolators, shock isolators, base mounts, stud mounts, foot mounts, engine mounts, mounts for electronics, exhaust brackets, anti-vibration gloves, rotary tool grips, oscillating tool grips, sporting goods grips, and combinations thereof.

[0053] In further embodiments, the present disclosure relates to three-dimensional (3D) foam devices constructed from porous materials and printed into forms by the printing methods (e.g., forming materials) described in detail herein.

[0054] In some embodiments, the morphology includes a solid portion, a lattice portion, or a macroporous portion, hi some embodiments, the morphology includes a solid exterior morphology and a lattice-like interior.

[0055] In some embodiments, the 3D foam device has a slow recovery time when deformed and released. In some embodiments, the 3D foam device has an improved recovery rate. In some embodiments, the 3D foam device has a high range of porosity. In some embodiments, the 3D foam device has a tailored porosity.

[0056] In some embodiments, the 3D foam device has a relatively low overall stiffness / durometer. In some embodiments, the relatively low overall stiffness / durometer improves the comfort of the 3D foam device. In some embodiments, the 3D foam device has improved acoustic dampening. In some embodiments, the improved acoustic dampening increases the performance of the 3D foam device.

[0057] In some embodiments, the 3D foam device exhibits a hierarchical structure. In some embodiments, the 3D foam device softens when the temperature of the 3D foam device is from room temperature to body temperature. In some embodiments, the 3D foam device is composed of closed cell liquid crystalline elastomer foam.

[0058] In some embodiments, the 3D foam devices have the form of, but are not limited to, ear molds, sound insulation clips, acoustic panels and baffles, ear cushions and covers for headphones, anti-vibration pads, ear tips for earbuds, packing bumpers, vibration isolators, shock isolators, base mounts, stud mounts, foot mounts, engine mounts, electronics mounts, exhaust brackets, anti-vibration gloves, rotary tool grips, oscillating tool grips, sporting goods grips, and combinations thereof.

[0059] Although various embodiments of the present disclosure have been described in the accompanying drawings and the foregoing detailed description, it is understood that the present disclosure is not limited to the embodiments disclosed herein, but rather that many rearrangements, modifications, and substitutions are possible without departing from the spirit of the present disclosure as defined above.

[0060] The term "substantially" is intended to broadly define what is specified, but not necessarily completely, as will be understood by those of skill in the art. With respect to the disclosed embodiments, the terms "substantially," "approximately," "generally," and "about" can be substituted with "within (a percentage)" of what is specified, where that percentage includes 0.1, 1, 5, and 10 percent.

[0061] The features of some embodiments have been outlined above to enable those skilled in the art to better understand the aspects of the present disclosure. Those skilled in the art should appreciate that they can readily use the present disclosure as a basis for designing or modifying other processes and structures to carry out the same purposes and / or achieve the same advantages of the aspects described herein. Those skilled in the art should also recognize that such equivalent constructions do not depart from the spirit and scope of the present disclosure, and that those skilled in the art can make various changes, substitutions and alterations without departing from the spirit and scope of the present disclosure. The scope of the present invention should be determined solely by the language of the following claims. The term "comprising" in the claims is intended to mean "including at least" such that the elements recited in the claims are in an open group. "A," "an," and other singular terms are intended to include the plural unless expressly excluded.

Claims

1. 1. A method of forming a three-dimensional (3D) printed resin, comprising: forming a mixture comprising combining a mesogen with a solvent and a stabilizer; heating the mixture to improve miscibility; adding a spacer to the mixture; and Adding a catalyst to the mixture A method comprising:

2. The mesogen may be 2-methyl-1,4-phenylenebis(4-(3-(acryloyloxy)propoxy)benzoate)), 4-[[[4-[(1-oxo-2-propenyl)oxy]butoxy]carbonyl]oxy]benzoic acid 2-methyl-1,4-phenylene ester, 4-[4-[(1-oxo-2-propenyl)oxy]butoxy]-,2-methyl-1,4-phenylene ester, 2-methyl-1,4-phenylenebis(4-((6-(acryloyloxy)hexyl)oxy)benzoate), 4,4'-bis(acryloyl)biphenyl, 4-(6-(acryloyloxy)hexyloxy)phenyl 4-(6-(acryloyloxy)hexyloxy)benzoate, acrylic acid 6-[ 2. The method of claim 1, wherein the alkyl group is selected from the group consisting of 4'-(6-acroyloxy-hexyloxy)biphenyl-4-yloxy]hexyl ester, 1,4:3,6-dianhydride-D-glucitol bis[4-[[4-[[[4-[(1-oxo-2-propenyl)oxy]butoxy]carbonyl]oxy]benzoyl]oxy]benzoate], 1,4-phenylene bis[4-[6-(acroyloxy)hexyloxy]benzoate], 1,4-phenylene bis(4-((acroyloxy)methoxy)benzoate), [4-(3-prop-2-enoyloxypropoxy)phenyl]4-(3-prop-2-enoyloxypropoxy)benzoate, and combinations thereof.

3. 10. The method of claim 1, wherein the solvent is selected from the group consisting of toluene, dichloromethane, acetone, chloroform, tetrahydrofuran, benzene, hexane, and combinations thereof.

4. 2. The method of claim 1, wherein the stabilizer is selected from the group consisting of dibutylhydroxytoluene (butylated hydroxytoluene; BHT), 1,3,5-trimethyl-2,4,6-tris(3,5-di-tert-butyl-4-hydroxybenzyl)benzene, hydroquinone monomethyl ether, 2-(2-hydroxyphenyl)-2H-benzotriazole, benzophenone, bisphenylene, and combinations thereof.

5. 2. The method of claim 1, wherein the spacer is selected from the group consisting of 2,2'-(ethylenedioxy)diethanethiol (EDDET); ethane-1,2-dithiol, 1,3-propanedithiol, 1,6-hexanedithiol, 1,9-nonanedithiol, 1,11-undecanedithiol, poly(ethylene glycol)dithiol, tetra(ethylene glycol)dithiol, hexa(ethylene glycol)dithiol, 1,4-benzenedimethanethiol, N-butylamine, ethylene glycol bis(3-mercaptopropionate), and combinations thereof.

6. 2. The method of claim 1, wherein the catalyst is selected from the group consisting of dipropylamine (DPA), hexylamine, triethylamine, tetramethyl-1,8-naphthalenediamine, 1,8-diazabicyclo[5.4.0]undec-7-ene, 1,5-diazabicyclo[4.3.0]non-5-ene, tripropylphosphine, dimethylphenylphosphine, methyldiphenylphosphine, pentamethyldiethylenetriamine, and combinations thereof.

7. mixing a photoinitiator with the mixture; heating the mixture; and remixing the mixture until the photoinitiator is completely dissolved; The method of claim 1 further comprising:

8. 8. The method of claim 7, wherein the photoinitiator is selected from the group consisting of phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide (PPO), 2-hydroxy-2-methylpropiophenone, diphenyl(2,4,6-trimethylbenzoyl)phosphine oxide, bis(2,4,6-trimethylbenzoyl)-phenylphosphine oxide), 2,2-dimethoxy-2-phenylacetophenone, and combinations thereof.

9. mixing the filler into the mixture until the filler is evenly distributed throughout the resin; and Allowing the mixture to cool to room temperature; The method of claim 1 further comprising:

10. 10. The method of claim 9, wherein the filler is selected from the group consisting of the following microspheres: EXPANCEL® 920 DE 80d30, EXPANCEL® 920 DE 40d30, EXPANCEL® 031 DU40, DUALITE® E135-025D, DUALITE® U015-135D, Kureha m330, Kureha m430, and combinations thereof.

11. 8. The method of claim 7, further comprising adjusting the viscosity of the mixture by adding a second solvent to the mixture.

12. 12. The method of claim 11, wherein the second solvent is selected from the group consisting of toluene, dichloromethane, acetone, chloroform, tetrahydrofuran, benzene, hexane, and combinations thereof.

13. The method of claim 1 further comprising mixing a thermal initiator with the mixture.

14. 14. The method of claim 13, wherein the thermal initiator is selected from the group consisting of peroxides, hydroperoxides, ketone peroxides, dialkyl peroxides, peroxyketals, peroxyesters, monoperoxycarbonates, diacyl peroxides, peroxydicarbonates, tert-butylperoxy-2-ethylhexanoate, n-butyl-4,4-di(tert-butylperoxy)valerate, 1,1-di(tert-butylperoxy)-3,3,5-trimethylcyclohexane, 1,1-bis(tert-amylperoxy)cyclohexane, 1,1-bis(tert-butylperoxy)cyclohexane, t-butylperoxyneodecanoate, tert-butylperoxybenzoate, and combinations thereof.

15. Pouring three-dimensional (3D) printing resin into a tank of a 3D printer; and Printing the material using at least one of visible light, near-infrared (IR) light, ultraviolet (UV) light, or heat to initiate a reaction of components in the 3D printing resin. A method of forming a material comprising:

16. 16. The method of claim 15, wherein at least one of visible light, near-IR light, or UV light converts the low molecular weight 3D printing resin into a crosslinked liquid crystal elastomer.

17. 16. The method of claim 15, further comprising adding a coloring dye to a tank of the 3D printer before printing the material.

18. The method of claim 15 further comprising post-processing.

19. 20. The method of claim 18, wherein the post-treatment is selected from the group consisting of washing the material in a solvent, post-curing the material in a UV oven, drying the material in a vacuum oven, mechanical buffing, dip coating, and combinations thereof.

20. 16. The method of claim 15, wherein the material is printed in a form selected from the group consisting of earmolds, sound insulation clips, acoustic panels and baffles, headphone ear cushions and covers, anti-vibration pads, ear tips for earphones, packing bumpers, vibration isolators, shock isolators, base mounts, stud mounts, foot mounts, engine mounts, electronics mounts, exhaust brackets, anti-vibration gloves, rotary tool grips, oscillating tool grips, sporting goods grips, and combinations thereof.

21. 16. A three-dimensional (3D) foam device comprising a porous material printed into a form by the printing method of claim 15.

22. 22. The 3D foam device of claim 21, wherein the morphology comprises at least one of a solid portion, a lattice portion, or a macroporous portion.

23. 22. The 3D foam device of claim 21, wherein the foam comprises a solid exterior form and a lattice-like interior.

24. 22. The 3D foam device of claim 21 having a form selected from the group consisting of earmolds, sound insulation clips, acoustic panels and baffles, headphone ear cushions and covers, anti-vibration pads, ear tips for earphones, packing bumpers, vibration isolators, shock isolators, base mounts, stud mounts, foot mounts, engine mounts, electronics mounts, exhaust brackets, anti-vibration gloves, rotary tool grips, oscillating tool grips, sporting goods grips, and combinations thereof.

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