Tomographic bath photopolymerization for 3D printing of objects with internal property variations

Abstract

The present disclosure relates to a method for manufacturing a multi-material three-dimensional object, the method including: calculating a number of projections describing the multi-material three-dimensional object formed from different orientation angles of the object, the number of projections including first number of projections describing a first configuration of the object formed from a first material and second number of projections describing a second configuration of the object formed from a second material; providing a build volume including a first photosensitive component that can be polymerized into the first material upon irradiation with light having a first wavelength and a second photosensitive component that can be polymerized into a second material upon irradiation with light having a second wavelength, the second material having different mechanical properties than the first material; illuminating the build volume with light in the number of patterns as defined by the projections at respective corresponding orientations and wavelengths, such that the light having the first wavelength deposits energy according to a first energy distribution and the light having the second wavelength deposits energy according to a second energy distribution, thereby physically recreating the multi-material three-dimensional object.

Description

[Technical Field]

[0001] The present disclosure relates to methods and systems for manufacturing multi-material three-dimensional objects by irradiating a build volume with several patterns of light at specific orientations and wavelengths. The method includes irradiating the build volume such that a three-dimensional energy distribution is produced for each wavelength that defines the solidified material and properties of the illuminated objects in the build volume. [Background technology]

[0002] 3D printing is an additive manufacturing (AM) technique for producing a wide range of structures and complex geometric shapes based on three-dimensional model data. The process relies on successive layers of material printed on top of each other. The technology was first developed by Charles Hull in 1986 in a process known as stereolithography (SLA).

[0003] SLA uses UV light or an electron beam to initiate a chain reaction on a layer of a resin or monomer solution, such as an acrylic or epoxy system. The monomer is UV-activated and converts into a polymer chain after activation (radicalization). Polymerization creates a pattern within the resin layer, which solidifies and can hold subsequent layers. After printing, unreacted resin is removed. Additionally, post-processing treatments such as heating or light curing can be applied to the printed object, depending on the material and desired mechanical properties.

[0004] SLA is a versatile method and is widely used, largely due to its success in rapid and inexpensive prototyping. However, it suffers from a slow printing speed. This is inherent to SLA, as it is a layer-by-layer process. Once a layer is irradiated and cured, a new layer of uncured material must be applied above or below the solid layer, depending on the build direction. Most commonly, uncured material is applied by mechanically recoating the surface, which not only lengthens print times but can also distort the resulting part. Summary of the Invention

[0005] The inventors have recognized that 3D printing need not be limited to layer-by-layer processing. Instead, the inventors have recognized that 3D printing can be achieved by a method that can reproduce an object by a three-dimensional energy distribution projected onto a build volume. The build volume can contain multiple photosensitive components, and activation of each photosensitive component can form materials with different properties, such as different mechanical properties. In this way, this method can enable rapid manufacturing of complex materials. Furthermore, the build volume can contain cells, such as undifferentiated stem cells, e.g., induced pluripotent stem cells. This method can be applied to the formation of artificial tissues, for example, for in vitro drug screening or in vivo implantation.

[0006] Thus, the present disclosure relates in a first aspect to a method for manufacturing a multi-material three-dimensional object, comprising: This method is calculating a number of projections describing the multi-material three-dimensional object formed from different orientation angles of the object, the number of projections comprising: several first projections describing a first configuration of an object formed from a first material; several second projections describing second configurations of the object formed from a second material; and providing a build volume, the build volume comprising: a first photosensitive component capable of polymerizing into a first material upon irradiation with light having a first wavelength; a second photosensitive component capable of polymerizing into a second material upon irradiation with light having a second wavelength, the second material having different mechanical properties than the first material; including giving and illuminating the build volume with several patterns of light, as defined by the projections, at respective corresponding orientations and wavelengths, such that light having a first wavelength deposits energy according to a first energy distribution and light having a second wavelength deposits energy according to a second energy distribution; This allows us to physically recreate multi-material three-dimensional objects, Includes.

[0007] Tomographic bath photopolymerization enables ultrafast 3D printing that is not limited to layer-by-layer processing. Because the method can involve multiple photosensitive components and one or more light sources to generate light at multiple wavelengths, it allows the reproduction of multi-material three-dimensional objects with voxel-defined internal property variations.

[0008] By selecting several photosensitive components to form materials with specific desired properties, such as different stiffness, upon activation in combination with the formation of wavelength-specific three-dimensional energy distributions corresponding to each photosensitive component, the property distribution of the multi-material three-dimensional object can be individually selected for each voxel. Preferably, the method is arranged such that dose ratios between different wavelengths can be individually specified for each voxel of the build volume, which translates into, for example, customization of chemical and mechanical properties for each voxel.

[0009] Preferably, the steps of calculating the first and second projections are defined by a distribution of mechanical properties of the multi-material three-dimensional object. For example, the multi-material three-dimensional object may be reproduced in several voxels of the build volume, and the calculating step comprises determining, for each voxel, a ratio between light having a first wavelength and light having a second wavelength, such that upon illumination of the voxel by these ratios the mechanical properties of each voxel are determined.

[0010] Typically, a three-dimensional multi-material object is composed of or includes a functionally graded material such that the mechanical stiffness of the object varies gradually across three dimensions. While some embodiments may include sequential activation of the photosensitive components, it is preferred that the activation of the photosensitive components at least partially overlap, preferably fully overlap, i.e., the photosensitive components are activated simultaneously. Generally, only simultaneous illumination of the build volume with light comprising a first wavelength and a second wavelength can produce such a functionally graded material. That is, the first and second wavelengths can be used to separately activate at least one of the first and second photosensitive components of the build volume.

[0011] The build volume can contain several photosensitive components, and the build volume can be irradiated with a corresponding number of three-dimensional energy distributions, each typically provided by a different wavelength distribution and / or wavelength of light to activate a separate photosensitive component, such that each three-dimensional energy distribution results in a distribution of material, and therefore mechanical or other properties, in the reproduced object, corresponding to the wavelength distribution of the irradiation.

[0012] The present disclosure relates in a second aspect to a system for manufacturing a multi-material three-dimensional object from a build volume, comprising: This system is a processing unit configured to calculate a number of projections describing a multi-material three-dimensional object formed from different orientation angles of the object, the number of projections comprising: several first projections describing a first configuration of an object formed from a first material; several second projections describing second configurations of the object formed from a second material; a processing unit including: a projection system capable of emitting light in a controlled spatial pattern at multiple wavelengths, the controlled spatial pattern resulting from the projection; A build volume, a first photosensitive component capable of polymerizing into a first material upon irradiation with light having a first wavelength; and a second photosensitive component capable of polymerizing into a second material upon irradiation of the photosensitive material with light having a second wavelength; a build volume, including: a direction adjusting unit for controllably varying the direction of incidence of the light of these patterns relative to the build volume; a controller configured to control the orientation adjustment unit and the projection system such that the build volume is illuminated with several patterns of light, as defined by the projections, at respective corresponding orientations and wavelengths, such that light having a first wavelength deposits energy according to a first energy distribution and light having a second wavelength deposits energy according to a second energy distribution; Includes.

[0013] These projections can be formed, for example, by application of a Radon transform followed by a tomographic reconstruction filter. The resulting projections can be two-dimensional patterns, each with a corresponding orientation angle. Illumination of the build volume can be performed by using multiple light sources, which may illuminate the build volume from different angles, or a single light source may be used. However, it is preferred that the light pattern based on the first projection is illuminated with a different wavelength distribution than the light pattern based on the second projection.

[0014] Preferably, the system is configured to illuminate the build volume with a first sequence of spatial light patterns at a first wavelength and, concurrently or subsequently, illuminate the build volume with a second sequence of spatial light patterns at a second wavelength until the multi-material three-dimensional object is formed, although the system may be configured to illuminate the build volume with any number of sequences of spatial light patterns, each having a different wavelength and each including a corresponding photosensitive component activated by the respective wavelength. [Brief explanation of the drawings]

[0015] [Figure 1]1 illustrates a system for manufacturing a multi-material three-dimensional object from a build volume, according to certain embodiments of the present disclosure. [Figure 2] The structural formula of an exemplary monomer is shown. [Figure 3] 1 shows a flowchart outlining a method for manufacturing a multi-material three-dimensional object, according to certain embodiments of the present disclosure. [Figure 4] 1 shows a flowchart outlining communication between components of a system for manufacturing a multi-material three-dimensional object from a build volume, according to certain embodiments of the present disclosure. [Figure 5] 1 illustrates an exemplary multi-material three-dimensional object. [Figure 6] 1 shows the projection of a multi-material three-dimensional object. DETAILED DESCRIPTION OF THE INVENTION

[0016] As used herein, the term photosensitive component refers to a material that changes its properties when exposed to electromagnetic radiation, typically light in the visible or ultraviolet range. These changes often manifest structurally, such as hardening of the material as a result of cross-linking upon exposure to light. The material may contain photoinitiators and / or photosensitizers to be activated by electromagnetic radiation. Activation can result in polymerization of other components of the photosensitive component, such as monomers and / or prepolymers.

[0017] As used herein, the term polymerization refers to the process of reacting prepolymer and / or monomer molecules together in a chemical reaction to form polymer chains or three-dimensional networks. Photopolymerization reactions are usually chain polymerizations initiated by the absorption of visible or ultraviolet light. The light may be absorbed either directly by the reactant monomers (direct photopolymerization) or by a photosensitizer or photoinitiator.

[0018] As used herein, the term prepolymer refers to a monomer or monomer system that has been reacted to an intermediate molecular mass state that can be polymerized or further polymerized to a higher molecular weight state via reactive groups.

[0019] As used herein, the term photoinitiator refers to a molecule that, upon irradiation with light, absorbs photons and forms reactive species from an excited state, which in turn initiates subsequent reactions. These initiating species can be radicals, cations, or anions. Different photoinitiators are distinguished by the wavelength range in which they exhibit high-energy absorption and are therefore easily described by their unique absorption spectra. Therefore, the choice of wavelength of the excitation light source and the composition of the photoinitiator are closely related to each other.

[0020] As used herein, the term orientation adjustment unit refers to a system configured to control the relative orientation of the build volume and the projection unit. For example, the orientation adjustment unit can include an orientation adjustment unit configured to project onto the build volume from multiple orientations by rotating the build volume, such as while the projection unit is stationary. Alternatively, or in addition, the projection unit can rotate about the build volume. Typically, the pivoting and / or rotation is in a horizontal plane, but can be in any plane.

[0021] As used herein, the term voxel refers to each of an array of volumetric elements that make up a conceptual three-dimensional space, and in particular each of an array of discrete elements into which a representation of a three-dimensional object, such as a multi-material three-dimensional object, is divided. In contrast, a point or pixel typically refers to a discrete point, such as the smallest addressable discrete element.

[0022] In a first aspect, the present disclosure relates to a method for manufacturing a three-dimensional object comprising multiple materials, the method comprising calculating a number of projections describing a multi-material three-dimensional object formed from different orientation angles of the object, where the number of projections can include a number of first projections describing a first version of the object formed from a first material and a number of second projections describing a second version of the object formed from a second material.

[0023] In a further embodiment of the present disclosure, a method includes providing a build volume, e.g., housed in a receptacle. The build volume typically includes several components that polymerize when exposed to light, such as light of a particular wavelength. Preferably, the build volume includes a first photosensitive component that can polymerize into a first material when irradiated with light having a first wavelength. Alternatively, or in addition, the build volume may include a second photosensitive component that can polymerize into a second material when irradiated with light having a second wavelength, which may be different from the first wavelength. In certain embodiments, the first and second photosensitive components can be polymerized by the same wavelength, but in such cases, it may be preferable for these components to have different responses to the same wavelength. For example, they may have different absorbances so that one of the first or second photosensitive components has a faster polymerization reaction. For example, it may be preferable for the absorption maximum of the first photosensitive component to be different from the absorption maximum of the second photosensitive component.

[0024] In a further embodiment of the present disclosure, the method includes illuminating the build volume. Preferably, the illumination includes illuminating the build volume with light in several patterns based on several projections. The illumination is preferably performed at corresponding orientations and wavelengths. These orientations preferably correspond to the angles of the projections. These wavelengths are selected based on the photosensitive components of the build volume. Typically, multiple photosensitive components are used, for example, photosensitive components that can be used to manufacture tilted objects. In the case of multiple photosensitive components, the wavelengths are preferably selected in combination with the orientations and energy distributions so that certain features of the object are formed from a first photosensitive component and other features of the object are formed from a second photosensitive component. By using photosensitive components that polymerize into materials with different properties, such as mechanical properties, complex objects can be rapidly formed. In one embodiment of the present disclosure, the illuminating step includes or consists of illuminating the build volume with several patterns of light, as defined by the projections, at respective corresponding orientations and wavelengths, such that in the build volume, light having a first wavelength deposits energy according to a first energy distribution and light having a second wavelength deposits energy according to a second energy distribution, preferably configured such that the multi-material three-dimensional object is reproduced within the build volume.

[0025] In one embodiment of the present disclosure, the mechanical properties of each point of the reproduced multi-material three-dimensional object are determined by the ratio between a first energy distribution and a second energy distribution accumulated at that point. By selecting photosensitive components such that the first photosensitive component is capable of polymerizing into a first material when irradiated with light having a first wavelength and the second photosensitive component is capable of polymerizing into a second material when irradiated with light having a second wavelength, the ratio between the first energy distribution and the second energy distribution can determine the mechanical properties of each point of the multi-material three-dimensional object, such as each voxel of the multi-material three-dimensional object. In one embodiment of the present disclosure, the method includes calculating several projections describing the multi-material three-dimensional object formed from different orientation angles of the object, providing a build volume, and illuminating the build volume with several patterns of light, where the illuminating step occurs after the calculating several projections and the providing the build volume. Thus, in one embodiment of the present disclosure, the calculating step occurs after the calculating several projections and the providing the build volume. In certain embodiments, the providing the build volume occurs before the calculating several projections. In another embodiment, the step of calculating several projections is after the step of providing the build volume.

[0026] In a further embodiment of the present disclosure, the multi-material three-dimensional object is reproduced in several voxels of the build volume, and the calculating step comprises determining, for each of these voxels, a ratio between light having a first wavelength and light having a second wavelength, such that upon irradiating the voxel with these ratios, the mechanical properties of each voxel are determined. As the properties of the multi-material three-dimensional object are defined for each voxel of this object, the size of the voxels may be the resolution of the method.

[0027] In a further embodiment of the present disclosure, the calculation steps of the first projection and the second projection are defined by a distribution of mechanical properties of the multi-material three-dimensional object. For example, the calculation may be configured, together with the illumination step, such that illuminating the build volume with light in the patterns resulting from the projection recreates the multi-material three-dimensional object. The mechanical properties of the multi-material three-dimensional object, such as stiffness, can be determined by the ratio between the first energy distribution and the second energy distribution. The first and second energy distributions can be accumulated in the build volume in the illumination step as a result of illuminating the build volume with several patterns of light at respective orientations and wavelengths.

[0028] Preferably, the first and second materials have different properties. For example, the first and second materials may have different mechanical properties, such as when fully polymerized. However, the first and second materials may differ in alternative and / or additional properties. Those skilled in the art will recognize photosensitive components with different properties suitable for use in conjunction with the methods of the present disclosure, such that the multi-material three-dimensional object includes points and / or voxels that differ in one or more properties, such as one mechanical property. Thus, in certain embodiments of the present disclosure, the first material is more rigid than the second material, and at corresponding points of the multi-material three-dimensional object that are more rigid, the irradiating step includes accumulating a higher dose of light having the first wavelength relative to light having the second wavelength.

[0029] In one embodiment of the present disclosure, the first photosensitive component includes an epoxy monomer and a first photoinitiator that is activated upon irradiation with light having a first wavelength, and the second photosensitive component includes an acrylate monomer and a second photoinitiator that is activated upon irradiation with light having a second wavelength.

[0030] In one embodiment of the present disclosure, the irradiating step comprises: illuminating the build volume with light by a projection system in a first number of patterns defined by first projections, the light having a first wavelength; illuminating the build volume with light by the projection system in a second number of patterns defined by the second projections, the light having a second wavelength; Includes.

[0031] The projection system may include one of a plurality of projection units configured such that the build volume is illuminated with a first number of patterns of light by the projection unit and simultaneously and / or sequentially illuminated with a second number of patterns of light by the same projection unit or a separate projection unit. The projection system may, for example, include a first projection unit for illuminating the build volume with the first number of patterns of light defined by first projections, where the light has a first wavelength, and a second projection unit for simultaneously and / or sequentially illuminating the build volume with the second number of patterns of light defined by second projections, where the light has a second wavelength.

[0032] In one embodiment of the present disclosure, the first projection unit, the second projection unit, and the build volume lie in a plane, and the build volume rotates about an axis of rotation that is perpendicular to the plane and intersects the center of the build volume.

[0033] In one embodiment of the present disclosure, the projections, such as the first projection and / or the second projection, are calculated using any one of the following list: a Radon transform followed by a tomographic reconstruction filter, a fan beam algorithm followed by a tomographic reconstruction filter, and / or a cone beam algorithm followed by a tomographic reconstruction filter.

[0034] The first and second wavelengths are preferably two different wavelengths sufficiently spectrally separated so that only irradiation by the first light or the second light results in polymerization of one of the first photosensitive component or the second photosensitive component, In one embodiment of the present disclosure, one of the first wavelength and the second wavelength is in the UV region and the other is in the visible region.

[0035] In one embodiment of the present disclosure, the reproduced multi-material three-dimensional object is comprised of a functionally graded material (FGM), which can be characterized by variations in composition and structure over a volume, which can result in corresponding changes in the properties of the material.

[0036] In one embodiment of the present disclosure, the multi-material three-dimensional object comprises portions, such as voxels and / or points, having Young's moduli that differ by at least two orders of magnitude, preferably at least four orders of magnitude, more preferably at least five orders of magnitude, and even more preferably at least six orders of magnitude.

[0037] In one embodiment of the present disclosure, the multi-material three-dimensional object is an artificial tissue, such as for in vitro drug screening or in vivo implantation. The multi-material three-dimensional object can be a scaffold for tissue engineering. In one embodiment of the present disclosure, the build volume contains cells, and the cells are arranged such that upon irradiation of the build volume, the cells are incorporated into the multi-material three-dimensional object. In one embodiment of the present disclosure, the cells can be induced pluripotent stem cells (iPS cells).

[0038] graded material In one embodiment of the present disclosure, the projection calculation is defined at least in part by the distribution of mechanical properties of the multi-material three-dimensional object. The multi-material three-dimensional object may include or consist of a functionally graded material, for example, a functionally graded material. The projection may be defined by a combination of the shape of the three-dimensional object and the property distribution of the object. The projection calculation can, for example, be configured to derive projections of the three-dimensional object at multiple angles, where the projections include wavelength and / or energy distributions. Preferably, the calculation is such that, when the projections are projected onto the build volume at respective orientations, they produce a multi-material three-dimensional object. The wavelengths and energy distributions of the projections are preferably selected such that, when projected onto the build volume at the relevant orientations, they produce an object having a desired distribution of one or more properties, such as mechanical properties. These projections can, for example, each be performed with a specific pattern and a specific wavelength or a specific wavelength distribution. Preferably, the wavelengths or wavelength distributions are selected to correspond to photosensitive components of the build volume, for example, the first and second photosensitive components, respectively. They may, for example, each be or include the absorption maximum of each photosensitive component.

[0039] In one embodiment of the present disclosure, the calculation of materials to be polymerized or activated for use in forming a particular feature of a multi-material three-dimensional object is defined by the object's property distribution, such as the distribution of mechanical properties. The property distribution of the three-dimensional object is therefore typically important for the calculation of the projection. The projection may include or consist of a two-dimensional energy distribution at multiple wavelengths or a single wavelength, but is preferably configured such that, when projected at their respective orientations onto the build volume, the energy and wavelength distribution of the projection results in a three-dimensional energy and wavelength distribution within the build volume. The build volume is preferably configured to polymerize into the multi-material three-dimensional object upon receiving the three-dimensional energy and wavelength distribution. It is further preferred that the object be a functionally graded material having variations in composition and / or structure.

[0040] In one embodiment of the present disclosure, each projection includes or consists of an energy distribution, and the calculation of the energy distribution of the projection is defined by the distribution of mechanical properties of the multi-material three-dimensional object. The projection may include or consist of a two-dimensional energy distribution that, when projected onto the build volume at each angle defined during the calculation, results in a three-dimensional energy and / or wavelength distribution. Preferably, the build volume is configured such that this three-dimensional energy and / or wavelength distribution results in the production of a multi-material three-dimensional object. For example, the build volume may include multiple photosensitive components that each polymerize at specific, e.g., different wavelengths, and / or above specific, e.g., different energy thresholds.

[0041] In one embodiment of the present disclosure, the materials, such as the first material and the second material, have different mechanical properties, such as when fully polymerized. The multi-material three-dimensional object can thereby include multiple materials with different properties. The materials, such as the first and second materials, can differ in any type of property, for example, mechanical, optical, electrical, thermal, chemical, acoustic, atomic, magnetic, and / or radiological properties. The multi-material three-dimensional object can thereby be composed of functionally graded materials, in which any of the mechanical, optical, electrical, thermal, chemical, acoustic, atomic, magnetic, and / or radiological properties varies throughout its volume.

[0042] In one embodiment of the present disclosure, during the irradiation step, the build volume is provided with an energy distribution that is based on or derived from the distribution of mechanical properties of the multi-material three-dimensional object. Preferably, the present disclosure includes calculating several projections of the object at a specific orientation and then projecting one of the projections onto the build volume so that the object is reproduced in the build volume. The reproduced object preferably has the same properties as the initial object. Here, the initial object can be said to be a model, e.g., a model of the three-dimensional multi-material object. Preferably, the model includes information about the shape and distribution of at least one property, such as the distribution of the mechanical property. Preferably, the model is reproduced by calculating several projections of the model at a specific orientation and projecting these projections onto the build volume. It should be noted that the reproduced object may be modified relative to the model, e.g., scaled uniformly or non-uniformly.

[0043] In one embodiment of the present disclosure, the energy distribution varies for each wavelength. Preferably, each calculated projection includes or consists of a two-dimensional pattern. Then, a three-dimensional energy distribution is preferably rendered within the build volume by projecting the two-dimensional pattern onto the build volume at each calculated orientation of each projection. Projecting these projections may be performed with a single wavelength to activate or polymerize only one or a few of the photosensitive components with each successive projection. It should also be noted that projections of multiple wavelengths may activate or polymerize only one or a few of the photosensitive components with each successive projection. In such cases, the multiple wavelengths are preferably selected to activate or polymerize only one or a few of the photosensitive components. In any of these cases, only one or a few of the photosensitive components are activated or polymerized by one or more wavelengths, and these projections can include multiple projection sequences, i.e., multiple sequences of two-dimensional patterns, which, when projected onto the build volume in their respective orientations as calculated during the calculation step, activate and / or photopolymerize one or substantially only one of the photosensitive components, resulting in the formation of a first model of the three-dimensional multi-material object. Projecting additional projection sequences, i.e., two-dimensional patterns, onto the build volume can activate and / or photopolymerize additional, e.g., second, model of the three-dimensional multi-material object, which have properties different from those of the first model.

[0044] In a preferred embodiment of the present disclosure, the calculated projections include at least a first projection sequence and a second projection sequence. Each projection sequence is preferably configured to produce a three-dimensional multi-material object, such as a first object or a second object, when projected onto the build volume at a corresponding orientation. Each of these three-dimensional multi-material object structures preferably has different properties, such as mechanical properties. Each projection sequence is preferably projected at one or more wavelengths specific to only one of the photosensitive components, and these one or more wavelengths are preferably selected to produce a three-dimensional multi-material object structure having desired properties, such as mechanical properties, to replicate one or more properties of the corresponding object of the model.

[0045] In one embodiment of the present disclosure, at least a portion of the features of a multi-material three-dimensional object formed from a first material and a second material overlap. As a result, following this projection of one or more projection sequences onto the build volume, where each projection sequence can have a wavelength distribution specific to one or more photosensitive components, the resulting three-dimensional energy distributions for each wavelength distribution can overlap. Preferably, each wavelength distribution is selected to activate or photopolymerize only or primarily a single photosensitive component. Each projection of the projection sequence is preferably projected onto the build volume with a specific wavelength distribution, such as a wavelength distribution specific to one photosensitive component. Preferably, each projection of the projection sequence is projected with a specific wavelength distribution, and each projection of the projection sequence is performed to result in a three-dimensional energy distribution for each wavelength distribution. In certain embodiments of the present disclosure, the three-dimensional energy distributions of at least two wavelength distributions at least partially overlap. This allows the reproduced multi-material three-dimensional object to include features that include or consist of multiple materials, such as the first material, the second material, and / or several additional materials.

[0046] In one embodiment of the present disclosure, a multi-material three-dimensional object is composed of gradient materials, such as functionally graded materials. Functionally graded materials (FGMs) are multifunctional materials that contain spatial variations in composition and / or microstructure for the specific purpose of controlling variations in properties, such as mechanical, thermal, structural, and / or functional properties. FGMs can be characterized by variations in composition and structure over a volumetric range, which can result in corresponding changes in material properties. These materials can be designed for specific functions and applications.

[0047] In one embodiment of the present disclosure, a multi-material three-dimensional object includes portions having Young's moduli that differ by at least one order of magnitude, preferably at least two orders of magnitude, and more preferably at least three orders of magnitude. An advantage of embodiments of the present disclosure is their ability to reproduce objects with properties, such as mechanical properties, that vary over large intervals. This is often the case in nature, for example, in vertebrates with soft and hard tissues. This allows the methods of the present disclosure to be used to accurately reproduce complex objects.

[0048] In one embodiment of the present disclosure, the calculating step further includes calculating at least one additional projection describing at least one additional feature of the object formed from at least one additional material. As disclosed elsewhere herein, any features of the object, such as the first feature, the second feature, and / or any additional features, may partially or completely overlap, thereby allowing features of the object to include multiple materials. In certain embodiments of the present disclosure, the three-dimensional energy distribution per wavelength distribution resulting from each projection of the projection sequence onto the build volume results in a degree of activation and / or photopolymerization corresponding to the energy at each location / voxel of the three-dimensional energy distribution. As a result, the properties of the reconstructed object may be a result of the energy and wavelength distributions at each voxel, i.e., a three-dimensional distribution, and the resulting properties do not depend solely on whether the energy at each voxel is above or below a threshold energy, but rather the properties of each voxel are determined by the sequential response to energy.

[0049] In one embodiment of the present disclosure, the build volume further includes at least one additional photosensitive component that can be polymerized into at least one additional material. In principle, there is no limit to the number of materials of the reproduced multi-material three-dimensional object. In one embodiment of the present disclosure, the build volume includes multiple photosensitive components, each responsive to a different wavelength distribution, such as being activated and / or polymerized by a different wavelength distribution, such as a single wavelength or multiple wavelengths. It is further preferred that several projection sequences are calculated, each including several projections of the three-dimensional multi-material object or model at a specific orientation. When this projection sequence is projected onto the build volume, an energy distribution within the build volume is generated for each wavelength distribution, thereby activating and / or polymerizing a specific photosensitive component. It is preferred to select specific photosensitive components so that the properties of the reproduced three-dimensional multi-material object correspond to the three-dimensional multi-material object / model. Thereby, for each voxel of the build volume, a projection and the projection of this projection are configured such that the energy distribution for each wavelength distribution activates and / or polymerizes specific photosensitive components, rendering the voxel of a recreated three-dimensional multi-material object having the properties of the three-dimensional multi-material object / model.

[0050] photosensitive component In one embodiment of the present disclosure, each of the photosensitive components includes a prepolymer, such as a monomer, and a photoactivator, such as a photosensitizer, a photoinitiator, or a mixture thereof. Preferably, the photosensitive components are configured to be activated by irradiation with light, which causes polymerization of the prepolymer. Activation typically occurs through activation of a photoactivator, typically through catalytic action. Generally, photoactivators are easily activated within a specific wavelength range / wavelength distribution. In one embodiment of the present disclosure, at least one of the first and second wavelengths can activate and / or polymerize both the first and second photoresponsive components. However, it is preferred that at least one of the first and second wavelengths, e.g., both, cannot activate and / or polymerize both the first and second photoresponsive components. In certain embodiments of the present disclosure, the first and second photoresponsive components are activated by different wavelengths.

[0051] For photoinitiation to proceed efficiently, the absorption band of the photoinitiator must overlap with the emission spectrum of the light source, i.e., the wavelength distribution used to polymerize that particular photosensitive component, and preferably there must be minimal competing absorption by components of the formulation at wavelengths corresponding to excitation of the photoinitiator.

[0052] In one embodiment of the present disclosure, each photosensitive component includes a different type of photoactivatable agent and / or prepolymer. Preferably, each photosensitive component includes at least a different type of photoactivatable agent, e.g., a photoactivatable agent activated with a different wavelength distribution. This allows specific photoactivatable agents to be activated by changing the wavelength distribution of the projected light and, therefore, the wavelength distribution of the resulting three-dimensional energy distribution. More preferably, each photosensitive component includes a different prepolymer. This allows three-dimensional structures of objects to be manufactured from specific materials by selecting an appropriate wavelength distribution corresponding to the specific photosensitive component. The prepolymers of the different photosensitive components can be configured, for example, so that the resulting polymeric materials have different mechanical properties after polymerization.

[0053] In one embodiment of the present disclosure, the photoinitiator is selected from a list including free radical photoinitiators, cationic photoinitiators, or a combination thereof. Photoinitiators are molecules that are sensitive to light. Upon absorbing light, they undergo photochemical cleavage to generate reactive species (either free radicals or Bronsted or Lewis acids) that interact with the active ingredient in the formulation. There are two classes of photoinitiators: Type I and Type II. Type I photoinitiators undergo unimolecular bond cleavage to generate reactive species after absorbing light. No other species is required for these photoinitiators to function. Type II photoinitiators undergo bimolecular reactions. After absorbing light, the photoinitiator reaches an excited state, from which it reacts with another molecule (a coinitiator or synergist) to generate a reactive species. Photosensitizers are molecules that cause a chemical change in another molecule during a photochemical process.

[0054] In one embodiment of the present disclosure, the prepolymer is selected from the list comprising acrylate-based monomers, epoxy-based monomers, or a combination thereof.

[0055] In one embodiment of the present disclosure, the illuminating wavelengths, such as the first wavelength and the second wavelength, are different wavelengths. These illuminating wavelengths may each comprise a single wave, or a wavelength distribution consisting of multiple wavelengths, such as a wavelength band or multiple discrete wavelengths, or may consist of a wavelength distribution. Thus, any of the first wavelength, second wavelength, and / or any additional wavelengths may comprise multiple wavelengths, such as one or more wavelength bands, or multiple single wavelengths, where any of the first wavelength, second wavelength, and / or any additional wavelengths may partially overlap.

[0056] In one particular embodiment of the present disclosure, any of the illumination wavelengths used for projecting a particular projection sequence may overlap with the illumination wavelengths used for projecting another projection sequence. However, it may be preferable for different photosensitive components not to have overlapping absorption maxima and / or substantially overlapping absorption spectra. As a result, in one embodiment of the present disclosure, different photosensitive components, such as the first and second photosensitive components, have absorption spectra that do not substantially overlap.

[0057] projection In one embodiment of the present disclosure, these projections are calculated at least in part using any one of the following projection algorithms: Radon transform, fan beam algorithm, cone beam algorithm, tomographic reconstruction filter, iterative reconstruction technique, algebraic reconstruction technique, and / or diffraction tomography algorithm, or a combination thereof.

[0058] As a result, the calculation may include applying a tomographic reconstruction filter after a Radon transform, a tomographic reconstruction filter after a fan-beam algorithm, a tomographic reconstruction filter after a cone-beam algorithm, an iterative reconstruction technique, an algebraic reconstruction technique, or a diffraction tomographic algorithm, or a combination thereof. In one embodiment of the present disclosure, the projection is obtained by applying at least one projection algorithm to the computer-based model. Thus, the method can be considered a method for fabricating a multi-material three-dimensional object that is a reproduction of the computer-based model. In one embodiment of the present disclosure, the method is a computer-implemented method or a processor-implemented method.

[0059] In one embodiment of the present disclosure, the build volume is irradiated with the first and second wavelengths at intervals and / or intensities such that irradiation is completed simultaneously. This typically ensures high accuracy in the reproduction of multi-material three-dimensional objects. For example, if one of these wavelengths activates both the first and second photosensitive components, the irradiation is preferably arranged so that irradiation of both the first and second wavelengths is stopped simultaneously. In this way, light contamination, i.e., undesired polymerization, as a result of sequential irradiation with a single wavelength (one that activates both the first and second photopolymerization initiators) can be minimized.

[0060] In one embodiment of the present disclosure, the illumination of the build volume with light having the first wavelength is completed at the same time as the illumination of the build volume with light having the second wavelength, and to achieve this, the time at which illumination with each wavelength begins and / or the intensity of each wavelength are adjusted so that illumination with the first and second wavelengths ends at the same time.

[0061] In a preferred embodiment of the present disclosure, the build volume is simultaneously illuminated with light having a first wavelength and light having a second wavelength.

[0062] Sinogram Calculation In a preferred embodiment of the present disclosure, the method includes measuring the polymerized first and / or second materials at regular intervals, and these measurements are used as feedback to correct the light in subsequent patterns to improve the accuracy of the reproduced multi-material three-dimensional object.

[0063] Relative Angle Preferably, the orientation and / or position of at least one of the build volume and the projection unit is changed during the projection. For example, the projection unit can rotate around the build volume while the build volume remains stationary, with the projection always directed toward the center, such as the horizontal center, of the build volume. Alternatively, the build volume can be rotated about an axis of rotation that is typically perpendicular to the projection plane. As known to those skilled in the art, several configurations of the positioning and / or orientation of the build volume and the projection unit are possible for reconstructing a three-dimensional multi-material object. Furthermore, multiple projection units can be used, and the projection units can be positioned at different locations, e.g., each projection unit can be positioned at a corresponding position for each projection. Thus, in certain embodiments of the present disclosure, the projection unit and the build volume remain stationary, but several projection units are positioned at corresponding angles of the projection of the three-dimensional object to be reconstructed, as defined during calculation.

[0064] As previously mentioned, multiple configurations of projection units and build volumes are possible. In one embodiment of the present disclosure, the patterns of light are generated by a first projection unit projecting a first pattern of light and a second projection unit projecting a second pattern of light, with the first projection unit projecting light substantially perpendicular to the second projection unit. In a specific embodiment of the present disclosure, the build volume rotates about a vertical axis of rotation that intersects the center of the build volume. In a further embodiment of the present disclosure, the patterns of light are generated by a projection unit projecting the patterns of light substantially parallel to the plane of rotation of the build volume. In a further embodiment of the present disclosure, the patterns of light are generated by a projection unit projecting the patterns of light substantially perpendicular to the plane of rotation of the build volume. In yet another embodiment of the present disclosure, the patterns of light are generated by a first projection unit projecting the first pattern of light substantially perpendicular to the plane of rotation of the build volume and a second projection unit projecting the second pattern of light substantially parallel to the plane of rotation of the build volume. In one embodiment of the present disclosure, these patterns of light are generated by a projection unit that rotates around the build volume and projects these patterns of light towards the build volume.

[0065] Post-processing In one embodiment of the present disclosure, the method further comprises removing the uncured build material from the build volume. The removing step is preferably after the step of irradiating the build volume, such as immediately after the step of irradiating the build volume. In one embodiment of the present disclosure, the method further comprises a solvent exchange step, such as to remove residual prepolymer and photoinitiator and make the material compatible with living cells. In one embodiment of the present disclosure, the solvent exchange comprises soaking the multi-material three-dimensional object in ethanol or isopropanol, such as for two days, followed by soaking in water, such as for two days with two changes of water.

[0066] Purpose In one embodiment of the present disclosure, the multi-material three-dimensional object is an artificial tissue, such as for in vitro drug screening or in vivo implantation.

[0067] In one embodiment of the present disclosure, the build volume contains cells, such as undifferentiated stem cells, for example iPS cells.

[0068] In one embodiment of the present disclosure, the patterns are generated and / or projected by at least one of a spatial light modulator, a digital micromirror device, a galvanometer scanner, or an acousto-optic deflector. In certain embodiments of the present disclosure, the patterns are generated and / or projected by a DLP projector, an LED projector, an LCD projector, and / or a laser projector. Generally, it is preferred that the patterns be projected onto the build volume during a maskless process, such as without the use of a photomask.

[0069] system In a second aspect, the present disclosure relates to a system for fabricating a multi-material three-dimensional object from a build volume, the system preferably comprising a processing unit for calculating a number of projections describing the multi-material three-dimensional object, preferably formed from different orientation angles of the object. Preferably, these projections include a number of first projections describing a first feature of the object formed from a first material and a number of second projections describing a second feature of the object formed from a second material. It should be noted that the first feature, the second feature, and / or any further features formed from any further materials preferably at least partially overlap.

[0070] In a further embodiment of the present disclosure, the system includes a projection system having at least one projection unit. The projection system is preferably configured to activate a plurality of photosensitive components, and then activate each photosensitive component. It is further preferred that the projection system is configured to emit a controlled spatial pattern of light at a wavelength corresponding to the activation wavelength of at least one of the photosensitive components. In a specific embodiment of the present disclosure, the projection unit is configured to emit the controlled spatial pattern of light at a plurality of wavelengths. Preferably, the projection system is configured to emit the controlled spatial pattern of light as defined by a calculated projection.

[0071] The projection system may include one of a plurality of projection units configured such that the build volume is illuminated with a first number of patterns of light by the projection unit and simultaneously and / or sequentially illuminated with a second number of patterns of light by the same projection unit or a separate projection unit. The projection system may, for example, include a first projection unit for illuminating the build volume with the first number of patterns of light defined by first projections, where the light has a first wavelength, and a second projection unit for simultaneously and / or sequentially illuminating the build volume with the second number of patterns of light defined by second projections, where the light has a second wavelength.

[0072] In one embodiment of the present disclosure, the build volume includes a first photosensitive component capable of polymerizing into a first material upon irradiation with light having a first wavelength. In a further embodiment of the present disclosure, the build volume includes a second photosensitive component capable of polymerizing into a second material upon irradiation of the photosensitive material with light having a second wavelength. In yet another embodiment of the present disclosure, the build volume includes any number of additional photosensitive components, each capable of polymerizing into a respective number of additional materials upon irradiation of the photosensitive material with light having any number of additional wavelengths. As disclosed elsewhere herein, the first material, the second material, and / or any additional materials preferably differ in any type of property. It is further noted that the properties of a build, such as a voxel of a reconstructed three-dimensional multi-material object, may depend on the material polymerized at that voxel, and further these properties may depend on the energy distribution experienced by that voxel; for example, the resulting properties of the illustrated voxel may depend not only on being above or below a threshold energy, but may also be a continuous response to energy or a continuous response above a certain threshold energy.

[0073] In a further embodiment of the present disclosure, the system includes a direction adjustment unit. Preferably, the direction adjustment unit is configured to controllably vary the incident direction of the light of these patterns relative to the build volume. The direction adjustment unit can rotate the build volume and / or the projection system. Preferably, the rotation is configured such that the light of these patterns is projected onto the build volume at multiple angles during the irradiation step. The direction adjustment unit can further include movement of mirrors and / or lenses, and while the illumination source of the projection unit and the build volume are fixed in place and do not rotate, the direction adjustment unit can include several lenses configured such that several patterns of light are projected onto the build volume at corresponding angles and corresponding wavelengths, as defined in the calculation step by the processing unit.

[0074] In yet another embodiment of the present disclosure, the system includes a controller. Preferably, the controller is configured to control the orientation adjustment unit and / or the projection unit. More preferably, the controller is configured to control the projection unit and the orientation adjustment unit such that the build volume is illuminated with controlled patterns of light at specific wavelengths from directions corresponding to different orientation angles. The controller may be a computer, and the computer may further include a processing unit.

[0075] In a further embodiment of the present disclosure, the system is configured to perform a method for manufacturing a multi-material three-dimensional object, as disclosed elsewhere herein. In one embodiment of the present disclosure, the method is a computer-implemented method or a processor-implemented method.

[0076] In one embodiment of the present disclosure, the system includes a receptacle, such as a vessel, for containing a build volume, which is optically transparent to light of these patterns. The receptacle is preferably cylindrical, but may also have a multi-sided shape. For example, the receptacle may be a vertically protruding polygon, such as a pentagon or decagon. In such cases, the system may include one projection unit positioned on each side of the multi-sided receptacle.

[0077] In an embodiment of the present disclosure, the processing unit is configured to calculate the projection based on a property distribution of the multi-material three-dimensional object, such as a distribution of mechanical properties.

[0078] In a further embodiment of the present disclosure, the processing unit is configured to calculate materials to use for forming a particular feature of the multi-material three-dimensional object based on a distribution of properties of the object, such as mechanical properties.

[0079] In an embodiment of the present disclosure, the projection comprises or consists of an energy distribution, and the processing unit is configured to calculate the energy distribution of the projection based on a property distribution of the multi-material three-dimensional object, such as a distribution of mechanical properties.

[0080] In one embodiment of the present disclosure, these projections include or consist of two-dimensional energy distributions. In a further embodiment of the present disclosure, the processing unit is configured to calculate the projections, the materials used, the wavelengths used to project each pattern of light onto the build volume, and / or the corresponding orientation angles. In a further embodiment of the present disclosure, the processing unit is configured to control the controller.

[0081] In one embodiment of the present disclosure, the build volume further includes at least one additional photosensitive component that can be polymerized into at least one additional material. In principle, there is no limit to the number of materials of the reproduced multi-material three-dimensional object. In one embodiment of the present disclosure, the build volume includes multiple photosensitive components, each responsive to a different wavelength distribution, such as being activated and / or polymerized by a different wavelength distribution, such as a single wavelength or multiple wavelengths. It is further preferred that several projection sequences are calculated, each including several projections of the three-dimensional multi-material object or model at a specific orientation. When this projection sequence is projected onto the build volume, an energy distribution within the build volume is generated for each wavelength distribution, thereby activating and / or polymerizing a specific photosensitive component. It is preferred to select specific photosensitive components so that the properties of the reproduced three-dimensional multi-material object correspond to the three-dimensional multi-material object / model. Thereby, for each voxel of the build volume, a projection and the projection of this projection are configured such that the energy distribution for each wavelength distribution activates and / or polymerizes specific photosensitive components, rendering the voxel of a recreated three-dimensional multi-material object having the properties of the three-dimensional multi-material object / model.

[0082] In a further embodiment of the present disclosure, a method includes providing a build volume. This build volume typically contains several components that polymerize into an object when exposed to light, such as light of a particular wavelength. Preferably, the build volume contains a first photosensitive component that can polymerize into a first material when irradiated with light having a first wavelength. Alternatively, or in addition, the build volume may contain a second photosensitive component that can polymerize into a second material when irradiated with light having a second wavelength, which may be different from the first wavelength. Note, however, that while the first and second photosensitive components may be polymerized by the same wavelength, in such cases, it is preferred that they have different responses to this same wavelength. For example, they may have different absorbances so that one of the first or second photosensitive components has a faster polymerization reaction. For example, it may be preferred that the absorption maximum of the first photosensitive component is different from the absorption maximum of the second photosensitive component.

[0083] In a further embodiment of the present disclosure, the system has a build volume containing at least two photosensitive components, including a first photosensitive component capable of polymerizing into a first material upon irradiation with light having a first wavelength and a second photosensitive component capable of polymerizing into a second material upon irradiation of the photosensitive material with light having a second wavelength. In a further embodiment of the present disclosure, the build volume includes several additional photosensitive components, each capable of polymerizing with several additional materials upon irradiation with light having several additional wavelengths.

[0084] In one embodiment of the present disclosure, the projection unit is configured to illuminate the build volume with light of different wavelengths. The projection unit may be configured to project several first projections within a wavelength distribution, such as a wavelength or wavelength band, and then project several second projections with another wavelength distribution. Typically, the first projections are configured to form a first material in a first build of the three-dimensional multi-material object following activation of a first light-sensitive component at a corresponding orientation, and the second projections are configured to form a second material in a second build of the three-dimensional multi-material object following activation of the first light-sensitive component at a corresponding orientation.

[0085] In one embodiment of the present disclosure, the system comprises a second projection unit configured to further illuminate the build volume with at least one pattern of light from an angle perpendicular to the pattern of light from the (first) projection unit.

[0086] In one embodiment of the present disclosure, the projection unit is configured to sequentially emit multiple wavelength distributions. In certain embodiments of the present disclosure, the projection unit comprises multiple light sources with different wavelength distributions and / or a single light source arranged to generate multiple separated wavelengths, such as a single light source combined with a filter unit configured for wavelength filtering to select a desired wavelength, such as a first wavelength or a second wavelength. The light source(s) may be, for example, one or more LEDs and / or lasers.

[0087] In one embodiment of the present disclosure, the projection unit includes at least one of a spatial light modulator, a digital micromirror device, a galvanometer scanner, or an acousto-optic deflector. In a specific embodiment of the present disclosure, the projection unit is a DLP projector, an LED projector, an LCD projector, and / or a laser projector. Generally, it is preferred that the pattern is projected onto the build volume during a maskless process, i.e., without the use of a photomask.

[0088] In general, the projection unit is preferably arranged to form several patterns of light, preferably simultaneously, where these patterns comprise light having a first wavelength that deposits energy according to a first energy distribution and light having a second wavelength that deposits energy according to a second energy distribution. The projection unit is preferably arranged to simultaneously illuminate the build volume with these patterns of light, and therefore preferably does not rely on the use of photomasks and / or filters to form the patterns.

[0089] By illuminating the build volume with light in several patterns as defined by the projection, separate energy distributions at different wavelengths can be obtained, allowing for the formation of objects containing gradient materials and / or features, such as voxels, that contain both the first and second materials.

[0090] In a preferred embodiment of the present disclosure, the build volume is simultaneously illuminated with several patterns of light as defined by the projections, at respective corresponding orientations and wavelengths such that light having a first wavelength deposits energy according to a first energy distribution and light having a second wavelength deposits energy according to a second energy distribution. Preferably, the method includes illuminating the build volume with light having a first wavelength simultaneously with light having a second wavelength. Preferably, the build volume includes multiple photosensitive components that are separately responsive to these first and second wavelengths.

[0091] In one embodiment of the present disclosure, the light source includes one or more incandescent lamps, such as halogen lamps, or one or more fluorescent lamps, such as lasers, LEDs, or discharge lamps.

[0092] Preferably, the orientation and / or position of at least one of the build volume and the projection unit is changed during the projection. For example, the projection unit can rotate around the build volume while the build volume remains stationary, with the projection always directed toward the center, such as the horizontal center, of the build volume. Alternatively, the build volume can be rotated about an axis of rotation that is typically perpendicular to the projection plane. As known to those skilled in the art, several configurations of the positioning and / or orientation of the build volume and the projection unit are possible for reconstructing a three-dimensional multi-material object. Furthermore, multiple projection units can be used, and the projection units can be positioned at different locations, e.g., each projection unit can be positioned at a corresponding position for each projection. Thus, in certain embodiments of the present disclosure, the projection unit and the build volume remain stationary, but several projection units are positioned at corresponding angles of the projection of the three-dimensional object to be reconstructed, as defined during calculation.

[0093] As previously mentioned, multiple configurations of projection units and build volumes are possible. In certain embodiments of the present disclosure, the build volume rotates about a vertical axis of rotation that intersects the center of the build volume. In further embodiments of the present disclosure, the patterns of light are generated by a projection unit that projects the patterns of light substantially parallel to the plane of rotation of the build volume. In further embodiments of the present disclosure, the patterns of light are generated by a projection unit that projects the patterns of light substantially perpendicular to the plane of rotation of the build volume. In yet another embodiment of the present disclosure, the patterns of light are generated by a first projection unit that projects a first pattern of light substantially perpendicular to the plane of rotation of the build volume and a second projection unit that projects a second pattern of light substantially parallel to the plane of rotation of the build volume. In one embodiment of the present disclosure, the patterns of light are generated by a projection unit that rotates about the build volume and projects the patterns of light toward the build volume.

[0094] In a preferred embodiment of the present disclosure, these patterns of light are generated by a first projection unit projecting a first pattern of light and a second projection unit projecting a second pattern of light, with the first projection unit projecting light substantially perpendicular to the second projection unit.

[0095] In one embodiment of the present disclosure, the orientation adjustment unit is configured to either rotate the build volume within the illumination field of the first projection unit and / or rotate the first projection unit around the build volume, such as while the projection unit is always pointed at the build volume.

[0096] In one embodiment of the present disclosure, the system is configured such that the build volume is illuminated with a first sequence of spatial light patterns at a first wavelength distribution, and concurrently or subsequently, the build volume is illuminated with a second sequence of spatial light patterns at a second wavelength until a multi-material three-dimensional object is formed.

[0097] In another embodiment of the present disclosure, the system is configured such that the build volume is illuminated with a first sequence of spatial light patterns at a first wavelength distribution, and in parallel or thereafter the build volume is illuminated with a second sequence of spatial light patterns at a second wavelength, and in parallel or thereafter the build volume is illuminated with any number of further sequences of spatial light patterns, each illuminated with any number of further wavelengths, until a multi-material three-dimensional object is formed.

[0098] Detailed Description of the Drawings The present invention will now be described in more detail with reference to the accompanying drawings, which are exemplary and intended to illustrate some of the features of the disclosed methods and systems for manufacturing multi-material three-dimensional objects, and should not be construed as limiting the disclosed invention.

[0099] FIG. 1 illustrates a tomographic bath photopolymerization system (1) for fabricating a multi-material three-dimensional object from a build volume according to certain embodiments of the present disclosure. FIG. 1A illustrates a system in which the build volume is contained by a receptacle (2). The exemplary system includes a projection system with two projection units: a first projection unit and a second projection unit. The first projection unit is a visible light DLP projector (3), and the second projection unit is an ultraviolet light DLP projector (4). Both projection units of the projection system are fixed in position and oriented to illuminate at least a build object in the build volume. As shown, the system can include an optical system (5), such as a lens, between the projector and the receptacle. While fixed in position, the receptacle is suspended from an orientation adjustment unit (5), illustrated herein as a rotating platform. This allows the build volume to rotate, and the projector units to project several patterns of light at their respective orientations and wavelengths. FIG. 1B illustrates the same system from an alternative angle.

[0100] Figure 2 shows the structural formulas of exemplary monomers that can be used to fabricate multi-material three-dimensional objects: i. polyethylene glycol diacrylate (PEGDA) and ii. 3,4-epoxycyclohexylmethyl 3,4-epoxy-cyclohexanecarboxylate (EEC). Different monomers can polymerize materials with different properties, such as mechanical properties. Materials based on PEGDA-based monomers are typically softer than those based on EEC. PEGDA can be used with photoinitiators that activate at specific wavelengths in the visible range, while EEC can be used with photoinitiators that activate at specific wavelengths in the UV range. The system can then be configured to generate specific three-dimensional energy distributions for each photoinitiator associated with EEC and PEGDA. The two distributions can be overlaid on the same geometric shape to define the relative light intensity per voxel.

[0101] FIG. 3 shows a flowchart outlining a method for fabricating a multi-material three-dimensional object according to certain embodiments of the present disclosure. The method can include calculating several projections (31), including several first projections describing a first structure of the object formed from a first material and several second projections describing a second structure of the object formed from a second material, to describe the multi-material three-dimensional object formed from different orientation angles of the object. Typically, several projection sequences are calculated, such as a first projection sequence including the first projections and a second projection sequence including the second projections. The method further includes providing a build volume (32). The build volume typically includes a first photosensitive component capable of polymerizing into a first material when irradiated with light having a first wavelength and a second photosensitive component capable of polymerizing into a second material when irradiated with light having a second wavelength. The method can further include physically recreating the multi-material three-dimensional object based on the projections by irradiating it with several patterns of light at respective corresponding orientations and wavelengths (33).

[0102] FIG. 4 shows a flowchart of communication between components of a system for fabricating a multi-material three-dimensional object from a build volume, according to certain embodiments of the present disclosure. A processing unit (41) can be used to calculate several projections describing the multi-material three-dimensional object formed from different orientation angles of the multi-material three-dimensional object. These orientation angles can include several first projections describing a first version of the object formed from a first material and several second projections describing a second version of the object formed from a second material. The first and second projections are communicated to a controller (42). The controller can be, for example, a computer different from or the same as the processing unit. The controller is connected to a direction adjustment unit (43) and a projection system (44) including at least one projection unit. The direction adjustment unit is configured to controllably vary the direction of incidence of light of these patterns relative to the build volume. The at least one projection unit is configured to emit light at multiple wavelengths in controlled spatial patterns, and these controlled spatial patterns result from the projections. The controller is configured to control the direction adjusting unit and the at least one projection unit such that the build volume is illuminated with controlled patterns of light at specific wavelengths from directions corresponding to different orientation angles.

[0103] Figure 5 shows an illustration of an exemplary multi-material three-dimensional object. The object includes a Baby Yoda figure (51) with isotropic mechanical properties, a brain (52) with a low Young's modulus, a heart (53) with a medium Young's modulus, and a lightsaber (54) with a high Young's modulus. The multi-material three-dimensional object thereby possesses multiple properties, exemplified herein as mechanical properties. To recreate the final object, the figure, brain, heart, and lightsaber are integrated into a continuous solid object with various mechanical properties, e.g., various degrees of stiffness.

[0104] FIG. 6 shows projections of the multi-material three-dimensional object shown in FIG. 5. FIG. 6A shows several first projections describing a first build of an object formed from a first material, and FIG. 6B shows several second projections describing a second build of an object formed from a second material. In this example, each first projection has an equivalent orientation angle between the second projections; for example, FIG. 6A(a) corresponds to FIG. 6B(a), FIG. 6A(b) corresponds to FIG. 6B(b), and so on. The gray value in each image represents the intensity of light projected onto the build volume. This allows for the ratio between the dose per wavelength at each orientation for each light projection / pattern, assuming the light is projected for the same duration. The first projections are used to irradiate a corresponding number of patterns of light at each corresponding orientation with a first wavelength distribution, exemplified herein as UV light. Similarly, the second projections are used to irradiate a corresponding number of patterns of light at each corresponding orientation with a second wavelength distribution, exemplified herein as visible light. In this example, the build volume contains two different photosensitive components. The first photosensitive component is exemplified as comprising 3,4-epoxycyclohexylmethyl 3,4-epoxy-cyclohexanecarboxylate (EEC) and a photoinitiator activated upon irradiation with UV light, e.g., a photocationic polymerization initiator based on triarylsulfonium hexafluoroantimonates (CAT2) activated using 365 nm illumination. The second photosensitive component is exemplified as comprising polyethylene glycol diacrylate (PEGDA) and a photoinitiator activated upon irradiation with visible light, e.g., the photoradical polymerization initiator camphorquinone activated using 450 nm illumination. To enhance selectivity of the first and second wavelengths, the illumination light can be filtered, e.g., with a low-pass, band-pass, or high-pass filter, so that each wavelength activates only one photosensitive component, or so that only one wavelength can activate both photosensitive components. Preferably, only one photosensitive component is activated upon illumination with light of each wavelength, e.g., the first or second wavelength, of each number of patterns.

[0105] item 1. A method for manufacturing a multi-material three-dimensional object, comprising: calculating a number of projections describing the multi-material three-dimensional object formed from different orientation angles of the object, the number of projections comprising: a number of first projections describing a first configuration of the object formed from a first material; a number of second projections describing second configurations of the object formed from a second material; said calculating including: providing a build volume, the build volume comprising: a first photosensitive component capable of polymerizing into said first material upon irradiation with light having a first wavelength; a second photosensitive component capable of polymerizing into said second material upon irradiation with light having a second wavelength, said second material having different mechanical properties than said first material; providing, illuminating the build volume with several patterns of light, as defined by the projections, at respective corresponding orientations and wavelengths, such that the light having the first wavelength deposits energy according to a first energy distribution and the light having the second wavelength deposits energy according to a second energy distribution; thereby physically reproducing said multi-material three-dimensional object; The method comprising:

[0106] 2. The method according to item 1, wherein the mechanical properties of each point of the reconstructed multi-material three-dimensional object are determined by the ratio between the first energy distribution and the second energy distribution deposited at the point.

[0107] 3. The method according to any one of the preceding items, wherein the steps of calculating the first projection and the second projection are defined by a distribution of the mechanical properties of the multi-material three-dimensional object.

[0108] 4. The method of any one of the preceding items, wherein the first material is more rigid than the second material, and at points of the multi-material three-dimensional object that are more rigid, the irradiating step comprises accumulating a higher dose of the light having the first wavelength relative to the light having the second wavelength.

[0109] 5. The method of any one of the preceding items, wherein the multi-material three-dimensional object is reproduced in several voxels of the build volume, and wherein the calculating step includes determining, for each of the voxels, a ratio between the light having the first wavelength and the light having the second wavelength, such that the mechanical property of each voxel is determined upon irradiating the voxel with said ratio.

[0110] 6. The method of any one of the preceding items, wherein the first photosensitive component comprises an epoxy monomer and a first photoinitiator that is activated upon irradiation with the light having the first wavelength, and the second photosensitive component comprises an acrylate monomer and a second photoinitiator that is activated upon irradiation with the light having the second wavelength and / or the first wavelength.

[0111] 7. The irradiating step includes: illuminating the build volume with light by a first projection unit in a first number of patterns defined by the first projections, the light having the first wavelength; illuminating the build volume with light by a second projection unit in a second number of patterns defined by the second projections, the light having the second wavelength; and Including, 10. The method of claim 1, wherein the first projection unit, the second projection unit, and the build volume lie in a plane, and the build volume rotates about a rotation axis that is perpendicular to the plane and intersects a center of the build volume.

[0112] 8. The method of any one of the preceding items, wherein the projections are calculated using one of the following list: a Radon transform followed by a tomographic reconstruction filter, a fan beam algorithm followed by a tomographic reconstruction filter, and / or a cone beam algorithm followed by a tomographic reconstruction filter.

[0113] 9. The method of any one of the preceding items, wherein one of the first wavelength and the second wavelength is in the UV region and the other is in the visible region.

[0114] 10. The method of any one of the preceding items, wherein the reproduced multi-material three-dimensional object comprises or consists of a functionally graded material.

[0115] 11. The method of any one of the preceding items, wherein the multi-material three-dimensional object comprises portions having Young's moduli that differ by at least two orders of magnitude.

[0116] 12. The method of any one of the preceding items, wherein the multi-material three-dimensional object is an artificial tissue, such as for in vitro drug screening or in vivo implantation.

[0117] 13. The method of any one of the preceding items, wherein the build volume comprises cells, the cells being arranged such that upon irradiation of the build volume, the cells are incorporated into the multi-material three-dimensional object.

[0118] 14. The method according to any one of the preceding items, wherein the calculation of the first projection and the second projection is defined by a distribution of the mechanical properties of the multi-material three-dimensional object.

[0119] 15. The method of any one of the preceding items, wherein the calculation of the materials to be used to form a particular feature of the multi-material three-dimensional object is defined by the distribution of the mechanical properties of the object.

[0120] 16. A method according to any one of the preceding items, wherein each projection comprises or consists of an energy distribution, and the calculation of the energy distribution of the projection is defined by the distribution of the mechanical properties of the multi-material three-dimensional object.

[0121] 17. The method of any one of the preceding items, wherein the mechanical properties of the materials, such as the first material and the second material, such as when fully polymerized, are different.

[0122] 18. The method according to any one of the preceding items, wherein the build volume is provided with an energy distribution during the irradiation step that determines the distribution of the mechanical properties of the multi-material three-dimensional object.

[0123] 19. The method according to item 18, wherein the energy distribution varies for each wavelength.

[0124] 20. The method of any one of the preceding items, wherein at least a portion of the features of the multi-material three-dimensional object formed from the first material and the second material overlap.

[0125] 21. The method of any one of the preceding items, wherein the reproduced multi-material three-dimensional object is composed of graded materials.

[0126] 22. The method of any one of the preceding items, wherein the multi-material three-dimensional object comprises portions having Young's moduli that differ by at least two orders of magnitude.

[0127] 23. The method of any one of the preceding items, wherein the calculating step includes calculating a number of third projections describing a third feature of the object formed from a third material.

[0128] 24. The method of claim 23, wherein the build volume comprises a third photosensitive component capable of polymerizing into the third material upon irradiation with light having a third wavelength.

[0129] 25. Each of the photosensitive components comprises: a. Prepolymers such as monomers, and b. a photoinitiator that is activated upon irradiation with light having an initiation wavelength, such as the first wavelength and the second wavelength, that is different for each of the photosensitive components; 10. The method of any one of the preceding items, comprising:

[0130] 26. The method of any one of the preceding items, wherein each photosensitive component comprises a different type of photoinitiator and / or prepolymer.

[0131] 27. The method of any one of the preceding items, wherein the photoinitiator is selected from the list comprising a free radical photoinitiator, a cationic photoinitiator, or a combination thereof.

[0132] 28. The method of any one of the preceding items, wherein the prepolymer is selected from the list comprising acrylate-based monomers, epoxy-based monomers, or combinations thereof.

[0133] 29. The method of any one of the preceding items, wherein the irradiation wavelengths, such as the first wavelength and the second wavelength, are different wavelengths.

[0134] 30. The method of any one of the preceding items, wherein the photosensitive components, such as the first photosensitive component and the second photosensitive component, have absorption spectra that are substantially non-overlapping.

[0135] 31. The method of any one of the preceding items, wherein the projections are calculated using any one of the following list: a Radon transform followed by a tomographic reconstruction filter, a fan beam algorithm followed by a tomographic reconstruction filter, a cone beam algorithm followed by a tomographic reconstruction filter, an iterative reconstruction technique, an algebraic reconstruction technique, or a diffraction tomography algorithm.

[0136] 32. The method of any one of the preceding items, wherein the build volume is rotated about a vertical axis of rotation that intersects the center of the build volume.

[0137] 33. The method of any one of the preceding items, wherein the pattern of light is generated by a projection unit projecting the pattern of light substantially parallel to a plane of rotation of the build volume.

[0138] 34. The method according to any one of items 1 to 31, wherein the pattern of light is generated by a projection unit that rotates around the build volume and projects the pattern of light towards the build volume.

[0139] 35. The method of any one of the preceding items, wherein the method further comprises removing uncured build material from the build volume following irradiation of the build volume.

[0140] 36. The method of any one of the preceding items, wherein the method further comprises a solvent exchange, such as to remove residual prepolymer and photoinitiator to make the material compatible with living cells.

[0141] 37. The method of any one of the preceding items, wherein the solvent exchange comprises immersing the multi-material three-dimensional object in ethanol, for example for two days, followed by immersion in water, for example for two days with two changes of water.

[0142] 38. The method of any one of the preceding items, wherein the multi-material three-dimensional object is an artificial tissue, such as for in vitro drug screening or in vivo implantation.

[0143] 39. The method of any one of the preceding items, wherein the build volume comprises cells, such as undifferentiated stem cells, e.g., iPS cells.

[0144] 40. A system for producing a multi-material three-dimensional object from a build volume, comprising: a processing unit for calculating a number of projections describing the multi-material three-dimensional object formed from different orientation angles of the object, the number of projections comprising: a number of first projections describing a first configuration of the object formed from a first material; a number of second projections describing second configurations of the object formed from a second material; the processing unit including a projection system capable of emitting light in a controlled spatial pattern at multiple wavelengths, the controlled spatial pattern resulting from the projection; and The build volume, a first photosensitive component capable of polymerizing into said first material upon irradiation with light having a first wavelength; and a second photosensitive component capable of polymerizing into said second material upon irradiation of said photosensitive material with light having a second wavelength; the build volume comprising: a direction adjusting unit for controllably varying the direction of incidence of the pattern of light relative to the build volume; a controller configured to control the orientation adjustment unit and the projection system such that the build volume is illuminated with light in several patterns, as defined by the projections, at respective corresponding orientations and wavelengths, such that the light having the first wavelength deposits energy according to a first energy distribution and the light having the second wavelength deposits energy according to a second energy distribution; The system comprising:

[0145] 41. The system described in item 40, wherein the system is configured to perform the method described in any one of items 1 to 39.

[0146] 42. The system of any one of items 40-41, further comprising a container for containing the build volume, the container being optically transparent to the light of the pattern.

[0147] 43. The system of any one of items 40 to 42, wherein the processing unit is configured to calculate the projection based on the distribution of the mechanical properties of the multi-material three-dimensional object.

[0148] 44. The system of any one of items 40 to 43, wherein the processing unit is configured to calculate the materials to use in forming a particular feature of the multi-material three-dimensional object based on the distribution of the mechanical properties of the object.

[0149] 45. The system described in any one of items 40 to 44, wherein the projection includes or consists of an energy distribution, and the processing unit is configured to calculate the energy distribution of the projection based on the distribution of the mechanical properties of the multi-material three-dimensional object.

[0150] 46. ​​The system has a build volume containing at least two photosensitive components; The at least two photosensitive components are a. a first photosensitive component capable of polymerizing into said first material upon irradiation with light having a first wavelength; b. a second photosensitive component capable of polymerizing into said second material upon irradiation of said photosensitive material with light having a second wavelength; 46. ​​The system according to any one of items 40 to 45, comprising:

[0151] 47. The system of any one of items 40 to 46, wherein the projection unit is configured to illuminate the build volume with light of different wavelengths.

[0152] 48. A system according to any one of items 40 to 47, wherein the projection unit is configured to further illuminate the build volume with a pattern of light at a second wavelength, e.g., from another angle.

[0153] 49. A system described in any one of items 40 to 48, wherein the projection unit includes a single light source arranged to generate a plurality of separated wavelengths, such as a plurality of light sources having different spectra, or a single light source coupled to a filter unit configured to filter out wavelengths such as the first wavelength or the second wavelength.

[0154] 50. A system described in any one of items 40 to 49, wherein the projection unit includes at least one of a spatial light modulator, a digital micromirror device, a galvanometer scanner, or an acousto-optic deflector.

[0155] 51. A system according to any one of items 40 to 50, wherein the light source comprises one or more incandescent lamps, such as halogen lamps, or one or more fluorescent lamps, such as lasers, LEDs, or discharge lamps.

[0156] 52. A system described in any one of items 40 to 51, wherein the orientation adjustment unit is configured to either rotate the build volume within the illumination area of ​​the first projection unit and / or rotate the first projection unit relative to the build volume.

[0157] 53. A system described in any one of items 40 to 52, wherein the first projection unit is oriented such that the illumination direction is parallel to the plane of rotation of the build volume.

[0158] 54. The system of any one of items 40 to 53, wherein the system is configured such that the build volume is illuminated by a first sequence of spatial light patterns at a first wavelength, and in parallel or subsequently, the build volume is illuminated by a second sequence of spatial light patterns at a second wavelength until the multi-material three-dimensional object is formed.

Claims

1. 1. A method for manufacturing a multi-material three-dimensional object, the method comprising: calculating, for each voxel of the object, a ratio between light having a first wavelength and light having a second wavelength based on a desired mechanical property of the voxel, and calculating, from different orientation angles, a plurality of projections defined by a distribution of the desired mechanical property throughout the object resulting from the ratio, the plurality of projections comprising: a plurality of first projections describing first features of the object formed from a first material; a plurality of second projections describing second configurations of the object formed from a second material; and providing a single build volume, the single build volume comprising: a first photosensitive component capable of polymerizing into said first material upon irradiation with light having a first wavelength; a second photosensitive component chemically different from the first photosensitive component and capable of polymerizing into the second material upon irradiation with light having a second wavelength, the second material having different mechanical properties than the first material; and and illuminating the single build volume in parallel with light in a pattern derived from the first projection at the first wavelength and the second projection at the second wavelength, such that the light having the first wavelength deposits energy in a plurality of voxels of the single build volume according to a first energy distribution and the light having the second wavelength deposits energy in the voxels according to a second energy distribution; thereby physically fabricating the multi-material three-dimensional object in a single build process; A method comprising:

2. The method of claim 1 , wherein the steps of calculating the first projection and the second projection are defined by a distribution of mechanical properties of the multi-material three-dimensional object.

3. 10. The method of claim 1, wherein the first material has a higher Young's modulus than the second material, and wherein the irradiating step comprises depositing a higher dose of light having the first wavelength relative to light having the second wavelength at corresponding voxels of the multi-material three-dimensional object having the higher Young's modulus.

4. The method of claim 1 , wherein one of the first wavelength and the second wavelength is in the UV region and the other is in the visible region.

5. The method of claim 1 , wherein the completion of the illumination of the single build volume with light having the first wavelength is completed simultaneously with light having the second wavelength.

6. Each of the first photosensitive component and the second photosensitive component comprises: a. a prepolymer, and b. A photopolymerization initiator that is activated when irradiated with light having a different initiation wavelength for each of the photosensitive components. Equipped with The method of claim 1 , wherein activation of the photoinitiator polymerizes the prepolymer.

7. 10. The method of claim 1, wherein the first photosensitive component comprises an epoxy monomer and a first photoinitiator that is activated upon irradiation with light having the first wavelength, and the second photosensitive component comprises an acrylate monomer and a second photoinitiator that is activated upon irradiation with light having the second wavelength.

8. The method of claim 1 , wherein the multi-material three-dimensional object being manufactured comprises voxels comprising both the first material and the second material.

9. The method of claim 1 , wherein the multi-material three-dimensional object being fabricated comprises features having Young's moduli that differ by at least two orders of magnitude.

10. The method of claim 1 , wherein the pattern is irradiated in a maskless process.

11. 1. A system for manufacturing a multi-material three-dimensional object from a build volume, the system comprising: a processing unit configured to calculate, for each voxel of the object, a ratio between light having a first wavelength and light having a second wavelength based on a desired mechanical property of the voxel, and to calculate, from different orientation angles, a plurality of projections defined by a distribution of the desired mechanical property over the object resulting from said ratio, wherein said plurality of projections comprises: a plurality of first projections describing first features of the object formed from a first material; a plurality of second projections describing second configurations of the object formed from a second material; a processing unit including: a projection system capable of emitting light in a controlled spatial pattern at multiple wavelengths, the controlled spatial pattern resulting from the projection; and The build volume, a first photosensitive component capable of polymerizing into said first material upon irradiation with light having a first wavelength; a second photosensitive component chemically different from the first photosensitive component and capable of polymerizing into the second material upon irradiation with light having a second wavelength, the second material having different mechanical properties than the first material; and the build volume comprising both a direction adjusting unit for controllably varying the direction of incidence of the pattern of light relative to the build volume; a controller configured to control the direction adjustment unit and the projection system such that the build volume is concurrently illuminated with multiple patterns of light, as defined by the projections, at respective corresponding orientations and wavelengths, wherein the build volume is simultaneously illuminated with light having the first wavelength and light having the second wavelength, such that light having the first wavelength deposits energy in some voxels of the build volume according to a first energy distribution and light having the second wavelength deposits energy in the voxels according to a second energy distribution, such that formation of the first material and the second material occurs in a single, continuous volumetric build process; and A system comprising:

12. The system of claim 11 , wherein the system is configured to simultaneously illuminate the build volume with light having the first wavelength and light having the second wavelength.

13. The system includes a build volume comprising at least two photosensitive components, the at least two photosensitive components comprising: a. a first photosensitive component capable of polymerizing into said first material upon irradiation with light having a first wavelength; and b. a second photosensitive component capable of polymerizing into said second material upon irradiation with light having a second wavelength. The system of claim 11 , comprising:

14. The system of claim 11 , wherein the projection system comprises at least one projection unit selected from the list comprising a spatial light modulator, a digital micromirror device, a galvanometer scanner, and an acousto-optic deflector.

15. 12. The system of claim 11, wherein the system is configured such that the build volume is illuminated with a first sequence of spatial light patterns at a first wavelength, and concurrently or subsequently, the build volume is illuminated with a second sequence of spatial light patterns at a second wavelength until the multi-material three-dimensional object is fabricated.

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