A method for making a composite material and composite material

Abstract

Herein described is a method for making a composite material, comprising the steps of (a) swelling a blank hydrogel or a blank organogel using an inorganic precursor mixture to form an inorganic precursor-containing solvent-containing gel, wherein the inorganic precursor mixture comprises a solvent and one or more inorganic precursors, and (b) converting the inorganic precursor into ceramic or metal within the solvent-containing gel by introduction of reagents and / or stimuli to obtain a composite material. Optionally, the composite material can be converted into an inorganic material with an additional step (c) comprising thermally treating the composite material. Also described are the resultant composite material and the optional resultant inorganic material.

Description

[0001]March 4, 2025 A method for making a composite material and composite material TECHNICAL FIELD The invention relates to a method for making a composite material as well as to a composite material containing ceramic and / or metal obtainable by the method. BACKGROUND In recent years, the additive manufacturing of composites, ceramics, and metals has become a significant area of interest as it has the potential to remove the geometrical limitations associated with the current state of the art methods used to form and shape these materials. In particular, the use of polymer-based additive manufacturing processes (such as material extrusion, vat photopolymerization, and material jetting processes, etc.) to fabricate composites, ceramics, and metals has garnered significant interest due to the accessibility and versatility of these printing techniques. However multiple challenges remain in utilizing these polymer-based techniques for the fabrication of composites, ceramics, and metals. Some issues include the need for polymer composite resins with high loading of ceramic and / or metal particles as starting materials, which results in high-viscosity resins that are difficult to print. Moreover, homogeneous distribution of the ceramic and / or metal particles within the polymer composite resin is difficult to achieve. Furthermore, in the case with vat photopolymerization, the solid ceramic and / or metal particles increase the refractive index of the resin and scatter the incident light, reducing both the cure depth and the dimensional accuracy of the print. Furthermore, the additive manufacturing of each new polymer composite resin via vat photopolymerization currently necessitates the time- and resource-consuming redesign and reformulation of the entire photoresin due to differences in light scattering, viscosity, and material compatibility between each matrix and filler. Thus, there exists a need in the art for versatile additive manufacturing processes that can make a wide range of materials, including composites, metals, and ceramics. A wide range of applications require or can benefit from composite, metallic or ceramic materials with customized sizes and geometries. Examples of such applications are thermal management, such as in applications requiring metallic nano- or micro-scale features, energy generation, such as for battery electrodes where customizable composition, porosity, and geometry can translate to increased performance, and medical devices, such as biologically inert, non-decomposing, bio-scaffolds or prostheses. As mentioned above, the incorporation of particles in a polymer composite resin poses many issues in the fabrication of composites, ceramics, and metals with vat photopolymerization. To circumvent the issue associated with having particles in the resin, several in-situ post-printing syntheses of particles within a polymer have been developed; however, in all cases the particle precursors were already present in the photoresin during vat photopolymerization. Moreover, spatial control of the particles is challenging using this particle-in-resin approach (Alketbi, A. S.; Raza, A.; Sajjad, M; Li, H; AlMarzooqi, F; Zhang, T. J., EcoMat.2022, 4, e12157; Sun, Z.-B.; Dong, X.-Z.; Chen,W.-Q.; Shoji, S.; Duan, X.-M.; Kawata, S., Nanotechnol. 2008, 19, 035611; Chiappone, A.;Fantino, E.; Roppolo, I.; Lorusso, M.; Manfredi, D.; Fino, P.; Pirri, C. F.; Calignano, F., ACSAppl. Mater. Interfaces 2016, 8, 5627–5633).Another issue often encountered when fabricating ceramics and / or metal materials by polymer -based additive manufacturing processes, in particular when using methods that rely on the use of inorganic-organic hybrid photoresins or metal precursors, is large shrinkage of the resultant ceramic and / or metal materials compared to the hybrid polymer that was used as starting material. This shrinkage is often undesired. HT / so 240174WO 04 March 2025 Thus, it is an object of the present invention to provide a method that addresses these and other needs in the state of the art by enabling additive manufacturing of complex three-dimensional composites and optionally also inorganic materials such as ceramics and metals, without requiring re-optimization of resins and curing parameters for different materials. Such a method should enable quick iteration, compositional tuning, and the ability to fabricate multi-materials, as well as spatial control of the composite material. Furthermore, it is an object of the present invention to provide a method that reduces the degree of shrinkage of the material during thermal treatment, compared with the composite material prior to thermal treatment, thus reducing unwanted warping and porosity of the resultant inorganic material. Other and further objects, features and advantages of the present invention will become apparent more fully from the following description. SUMMARY OF THE INVENTION Some or all of these objects are achieved with the present invention by the method according to claim 1 and the composite material according to claim 17. It was surprisingly found that the method according to the invention allowed the synthesis of composite materials by first swelling a blank hydrogel or blank organogel using an inorganic precursor mixture to form an inorganic precursor-containing solvent-containing gel, the inorganic precursor mixture comprising a solvent, preferably water, and one or more inorganic precursors. In a second step, the inorganic precursor was successfully converted into a ceramic or metal within the solvent-containing gel by the introduction of reagents and / or stimuli to obtain a composite material. In an optional third step, the composite material could then further be treated thermally to arrive at an inorganic material. The composite material may be a ceramic- and / or metal-containing material. The inorganic material may also be a ceramic- and / or metal-containing material. HT / so 240174WO 04 March 2025 The method according to the invention avoids the issues associated with printing of composite materials using vat photopolymerization, such as light scattering by the inorganic particles or the need for highly viscous printing slurries, by synthesizing the inorganic particles in-situ after printing of the hydrogel or organogel. The viscosity of the photopolymerization mixture can be kept low, improving processability. Furthermore, there is no light scattering caused by the presence of inorganic particles, which increases the accuracy and resolution of the printed hydrogel or organogel. Moreover, since the inorganic precursor is introduced into a blank hydrogel or organogel after the printing, various different composite materials can be produced by simply exchanging the inorganic precursor. This avoids the need for a reformulation of the photopolymerization mixture for each inorganic precursor, and it also avoids the need to reoptimize the printing parameters for each composite material. In addition, with the method according to the invention, it is possible to synthesize hollow ceramic and / or metal structures. Without wishing to be bound by scientific theory, it is believed that, using the method according to the invention, it is possible to exert at least some control over the spatial distribution of the ceramic and / or metal within the solvent-containing gel and / or the composite material through the suitable choice of reagents and / or stimuli. As an example, the reagent can be chosen according to its pKb value or standard reduction potential, which may influence the spatial distribution of the ceramic and / or metal within the solvent-containing gel and / or composite material. In this way, the ceramic and / or metal may, for example, be present only close to the surface of the composite material, or alternatively distributed throughout the entire composite material. Further, it is possible to increase the amount of inorganic precursor and / or ceramic of metal within the solvent-containing gel by repeating steps (a) and (b) of the method according to the invention, resulting in an increased amount of metal and / or ceramic within the composite material. Surprisingly, this results in reduced shrinkage of the HT / so 240174WO 04 March 2025 inorganic material during optional subsequent thermal treatment. Also, the loading with ceramic or metal in the composite material may be increased. By using different inorganic precursors in subsequent cycles of steps (a) and (b) of the method according to the invention, it is also possible to synthesize composite materials with multiple components, such as several metals, a mixture of both metals and ceramics, or several ceramics. Inorganic materials prepared from these composite materials may then also contain multiple components, such as several metals, a mixture of both metals and ceramics, or several ceramics. Without wishing to be bound by scientific theory, it is believed that the repetition of steps (a) and (b) of the method according to the invention allows to overcome the issue of the limited solubility of the inorganic precursor in the solvent of the inorganic precursor mixture, which otherwise limits the amount of inorganic precursor that can be introduced into the hydrogel or organogel by swelling alone. Additionally, step (b) of the method according to the invention, during which the inorganic precursor is transformed into a metal or ceramic, brings a further advantage in that the composite material may optionally be washed and / or soaked, for example with deionized water, prior to an optional thermal treatment in an optional additional step (c). This optional washing and / or soaking step removes the remainder of the inorganic precursor mixture, in particular of the inorganic precursor, such as nitrates, from the composite material. If step (b) were not included in the method according to the invention, the entire inorganic precursor mixture would have to remain within the solvent-containing gel for an optional subsequent thermal treatment, since no washing and / or soaking would be possible without also inadvertently removing the inorganic precursor. If significant amounts of, for example, nitrates remained in the composite material during the thermal treatment, they might react violently, potentially causing a runaway reaction and resulting in holes in the resultant inorganic material as the polymer part of the composite material would be burned too quickly. The ability to remove these remainders of the inorganic precursor mixture prior to thermal treatment increases the potential reliability and consistency of the overall synthesis process and improves the quality of the resultant inorganic material. HT / so 240174WO 04 March 2025 Step (b) of the method of the invention thus allows for repeating steps (a) and (b) thereby increasing the load of ceramic or metal and also allows for washing and / or soaking the composite material. Shrinkage of the inorganic material obtained after an optional thermal treatment step (c) may thus be tuned. Also, the quality of the resultant inorganic material may be improved. This is not possible if only steps (a) and (c) are performed. The composite material according to the invention preferably has a structure or a shape. In particular, the composite material is an object with a shape, in particular a designed shape. The shape of the object is in particular not limited. Hence, examples of structures are monolithic structures such as a cube, a sphere, a polyhedron, a disc, in particular a round disc, a trigonal disc or a polygonal disc; grids or nets; rods, or more complex structures such as lattices that are periodic or aperiodic in nature, beam- based lattices, plate-based lattices, triply periodic minimal surfaces, woven structures, and spinodal structures. The method according to the invention may in particular be a method for making a composite structure. The composite material according to the invention may in particular be a composite structure. The inorganic material preferably also has a structure or a shape. Preferably, the details concerning the structure or shape of the composite material correspondingly also apply to the structure or shape of the inorganic material. More preferably, the shape of the inorganic material is at least partially determined by the shape of the composite material. Metalloid elements in particular include B, Si, Ge, As, Sb, and Te. The term “metal alloy” may in particular refer to an alloy of two or more metals. The term “ceramic” may in particular refer to a solid material comprising a compound of metal, non-metal, or metalloid atoms substantially or essentially held in ionic or ionic and covalent bonds. For example, a ceramic material can be characterized as having cations (e.g., metal ions, which can be metalloid ions) and anions (e.g., oxygen HT / so 240174WO 04 March 2025 ions, nitrogen ions, carbide ions) substantially or essentially held together in ionic or ionic and covalent bonds. However, solvated ions or associated ions in a solvent do not fall under the term “ceramic”. Exemplary ceramic materials include, but are not limited to, barium titanate, bismuth strontium calcium copper oxide, boron oxide, boron nitride, ferrite, lead zirconate titanate magnesium diboride, silicon carbide, silicon nitride, sialon (silicon aluminum oxyni­tride), aluminum oxide, copper oxide, cobalt oxide, zinc oxide, steatite, titanium carbide, titanium oxide, uranium oxide, yitrium barium copper oxide, zirconium dioxide, and any combinations of these. The term “hydrogel” may in particular refer to a material comprising a network of one or more polymers, preferably one or more hydrophilic polymers, and comprising water. Preferably, but not necessarily, a hydrogel comprises a water content selected from the range of 1 wt. % to 90 wt. %, more preferably, but not necessarily, selected from the range of 10 wt. % to 90 wt. %. Optionally, a hydrogel further comprises one or more co-solvent in addition to water, where the co-solvent can be a water-miscible non-water solvent. The co-solvent(s), if present in a hydrogel, may be present in an amount (e.g., wt. %) less than a corresponding amount (e.g., wt. %) of water in the same hydrogel. As used herein, the term “organogel” may in particular refer to a material comprising a network of one or more polymers, preferably one or more hydrophilic polymers, and comprising a water-miscible non-water solvent. Preferably, but not necessarily, an organogel comprises a water-miscible non-water solvent content selected from the range of 1 wt. % to 90 wt. %, more preferably selected from the range of 10 wt. % to 90 wt. % Optionally, an organogel further comprises water, in addition to the water­miscible non-water solvent, where the water, if present in the organogel, is present in an amount (e.g., wt. %) less than a corresponding amount (e.g., wt. %) of the water-miscible non-water solvent in the same organogel. Hydrogels are further characterized and described in Ahmed (“Hydrogel: Preparation, characterization, and applications: A review”, Journal of Advanced Research, vol.6, issue.2, pgs.105-121, published Jul.18, 2013), which is incorporated herein by reference to the extent not inconsistent herewith. Organogels are further characterized and described in Murdan (“Organo­gels in drug delivery”, Expert HT / so 240174WO 04 March 2025 Opinion on Drug Delivery, vol.2, issue 3, pages 489-505, published May 10, 2005), which is incorporated herein by reference to the extent not inconsistent herewith. The term “photosensitive binder” may in particular refer to a cross­linkable material or chemical species (e.g., compound or molecule) that can be induced to cross-link with another photosensitive binder via electromagnetic radiation, such as light, such as visible light or ultra-violet light. Exemplary photosensitive binders include, but are not limited to, monomers, macromolecules, and polymers. Photosensitive binders particularly include but are not limited to poly(ethylene glycol) macromolecules with acrylate functional groups, acrylic acid, acrylamide, and 2-acrylamido-2- methylpropane sulfonic acid. The term “non-water” in reference to a solvent may in particular refer to a solvent other than water. Exemplary non-water water-miscible solvents include, but are not limited to, dimethyl sulfoxide (DMSO), N,N-dimethylformamide (DMF), isopropanol, methanol, glycerol, ethanol, and any combinations of these. The term “blank” in reference to a hydrogel (e.g., blank hydrogel) or an organogel (e.g., blank organogel) may in particular refer to a hydrogel or organogel, respectively, that is capable of and does take up (e.g., swell-in; e.g., via diffusion, absorption, and / or adsorption) inorganic precursors, such as metal salts or metal ions, in particular during a method for making a composite material, such as any method for making a composite material disclosed herein, such as during a step of swelling of any method for making a composite material disclosed herein. Preferably, but not necessarily, each of any blank hydrogel and any blank organogel has less than or equal to 0.5 wt. % of inorganic precursors such as metal and metal-containing chemical species (e.g., metal salts, metal ions, metal-containing nanoparticles). Preferably, but not necessarily, each of any blank hydrogel and any blank organogel has less than or equal to 0.6 wt. %, preferably less than or equal to less than 0.5 wt. %, more preferably less than or equal to 0.4 wt. %, optionally less than or equal to 0.3 wt. %, optionally less than or equal to 0.2 wt. %, optionally less than or equal to 0.1 wt. %, less than or equal to 0.05 wt. %, HT / so 240174WO 04 March 2025 and optionally less than or equal to 0.01 wt. %, of inorganic precursors such as metal and metal-containing chemical species (e.g., metal salts, metal ions, metal-containing nanoparticles). Preferably, each of any blank hydrogel and any blank organogel can be independently characterized as being free of inorganic precursors, such as metal and metal-containing species, other than photoinitiator(s) and UV-blocker(s). A “blank” mixture may in particular refer to a mixture that is free of inorganic precursors, such as metal and metal-containing species, other than photoinitiator(s) and UV-blocker(s). Optionally, a blank mixture can have trace or impurity amounts of inorganic species such as metal(s) or metal-containing species. A “blank aqueous mixture” may in particular refer to a mixture capable of and used to form a blank hydrogel, such as via a photopolymerization process performed on the blank aqueous mixture. A “blank nonaqueous mixture” may in particular refer to a mixture capable of and used to form a blank organogel, such as via a photopolymerization process performed on the blank nonaqueous mixture. The term “photopolymerization” may in particular refer to a process that uses electromagnetic radiation, such as light, such as visible light, infrared light, and / or ultra-violet light, to initiate and propagate a polymerization or cross-linking reaction between or among cross-linkable materials or chemical species. Photolithography is a non-limiting example of a photopolymerization process. The term “additive manufacture process” may in particular refer to a process for forming a material, a structure, or feature via deposition, or otherwise building up, of a material. The terms “additive manufacture process” and “additive manufacturing process” may be used interchangeably. An additive manufacture process can involve layer-by-layer and / or continuous or volume deposition of a material to form a three- dimensional structure or element. The deposited material may include, but is not limited to, inorganic materials, hybrid organic-inorganic materials, polymers, metals, or combinations of these. Exemplary additive manufacture processes include, but are not limited to, 3D printing, stereolithography (SLA), continuous liquid interface production, fused deposit modelling (FDM), 2-photon lithography, digital light HT / so 240174WO 04 March 2025 processing (DLP) printing , direct ink writing, micro-stereolithographic (µ-SLA), interference lithography, holographic lithography, stimulated emission depletion (STED) lithography, vat photopolymerization, material extrusion, material jetting, and powder bed fusion. In some embodiments, an additive manufacture process does not require a subtractive manufacture to form the structure or element. Examples of subtractive manufacture processes include, but are not limited to, milling, machining, electron discharge machining, carving, shaping, grinding, drilling, and etching. In an embodiment, an additive manufacture process involves or is aided by computer-aided design (CAD). The term “swelling” may in particular refer to a first material, such as a hydrogel or an organogel or a composite material, taking up at least one other material and / or chemical species (e.g., inorganic precursor such as metal ion(s)) such that said at least one other material and / or chemical species becomes a part of the composition of said first material. Preferably, but not necessarily, swelling refers to the taking up of at least one inorganic precursor such as metal and / or metal-containing species (e.g., metal salt; e.g., metal ions). Swelling, or the “taking up”, can occur by absorption, adsorption, and / or diffusion, for example, of said at least one other material and / or chemical species into said first material. Preferably, the swelling is a process involving a liquid mixture wherein the first material (e.g., a hydrogel or an organogel or a composite material) is exposed to a liquid mixture (e.g., an aqueous metal salt mixture), in which the at least one other material and / or chemical species (preferably, at least one inorganic precursor such as a metal and / or metal-containing species) is dispersed or dissolved, such that the at least one other material and / or chemical species (preferably, at least one inorganic precursor such as a metal and / or metal- containing species) is taken up from said liquid mixture (e.g., an aqueous metal salt mixture) into the first material (e.g., a hydrogel or an organogel or composite material). Optionally, the at least one other material and / or chemical species taken-up remains dispersed or dissolved in a solvent in the first material. For example, a hydrogel or an organogel may take up a mixture of water and at least one aqueous HT / so 240174WO 04 March 2025 metal salt, where at least a portion of the at least one metal salt taken-up remains dissolved in the mixture. PREFERRED EMBODIMENTS OF THE INVENTION The invention provides for a method for the synthesis of a composite material , the method comprising the steps of: (a) swelling a blank hydrogel or a blank organogel using an inorganic precursor mixture to form an inorganic precursor-containing solvent-containing gel, wherein the inorganic precursor mixture comprises a solvent, preferably water, and one or more inorganic precursors; and (b) converting the inorganic precursor into ceramic or metal within the solvent- containing gel by introduction of reagents and / or stimuli to obtain a composite material. Further advantageous embodiments of the invention are specified in the dependent claims and are elucidated in detail herein below. The composite material is preferably a polymer composite material. The ceramic into which the inorganic precursor is formed within the solvent- containing gel in step (b) of the method of the invention preferably comprises or consists of ceramic particles. The metal into which the inorganic precursor is formed within the solvent-containing gel in step (b) of the method of the invention preferably comprises or consists of metal particles. According to an embodiment, the composite material is thermally treated in an additional step (c) after step (b) to form an inorganic material, such as a ceramic and / or a metal. Before thermally treating the composite material, it may optionally also be treated with a solvent in step (c). By treating the composite material with a solvent in step (c), the organic component, in particular the polymer component of the HT / so 240174WO 04 March 2025 hydrogel may be removed yielding an inorganic material. By thermally treating the material in step (c) the ceramic or metal may in particular be sintered. The skilled person is familiar with suitable solvents that can be used for removing the polymer component of the hydrogel. The composite material may be in the form of a gel, for example a hydrogel or an organogel. The composite material may also be dried, in particular after step (b). Advantageously, step (a) of the method according to the invention is conducted at a temperature higher than room temperature, preferably at a temperature of from 50 to 80°C, particularly preferably from 60 to 70°C. Further, step (a) may be conducted for different periods of time. Preferably, step (a) is conducted for a duration of from 1 to 5 h, preferably from 2 to 4 h, particularly preferably from 2.5 to 3.5 h. Step (b) of the method according to the invention is advantageously conducted at a temperature of from -10 to 70°C, preferably from -5 to 55°C. Further, step (b) may be conducted for different periods of time. Preferably, step (b) is conducted for a duration of from 1 to 120 min, preferably from 3 to 60 min, particularly preferably from 5 to 30 min. In an embodiment, the composite material is washed with a solvent, preferably deionized water, and / or soaked in a solvent, preferably deionized water, prior to an optional step (c) comprising a thermal treatment. Preferably, the composite material is first washed with a solvent, preferably deionized water, and then soaked in a solvent, preferably deionized water, prior to an optional step (c) comprising a thermal treatment. Moreover, the composite material is preferably dried after soaking in a solvent and before an optional step (c), for example at a temperature from 10 to 80°C, or from 15 to 50°C. The composite material may be washed and / or soaked in a solvent for a duration of from 6 to 18 h, preferably from 10 to 14 h, or from 1 to 18 h, preferably from 1 to 5 h, prior to an optional step (c) comprising a thermal treatment. By washing and / or soaking the composite material before an optional step (c) HT / so 240174WO 04 March 2025 comprising a thermal treatment, potentially detrimental inorganic precursor residues such as nitrates may be removed. According to an embodiment, steps (a) and (b) of the method according to the invention are repeated one or more times. The skilled person understands that when repeating steps (a) and (b) in this embodiment, the composite material is preferably swelled instead of the blank hydrogel or the blank organogel with an inorganic precursor mixture. For example, steps (a) and (b) may be repeated once, twice, three times, four times, five times, six times, seven times, eight times, nine times, or ten times. Steps (a) and (b) may be conducted at least two times, preferably at least five times, more preferably at least ten times. Preferably, each repetition of step (a) comprises using the inorganic precursor mixture containing the solvent and the one or more inorganic precursors. Alternatively, each repetition of step (a) preferably comprises using a different inorganic precursor mixture containing a solvent and a different one or more inorganic precursors. By repeating steps (a) and (b) one or more times, the amount of ceramic and / or metal in the composite material can be increased significantly, since the issue of limited solubility of the inorganic precursor or precursors in the solvent is circumvented. Since a higher amount of inorganic precursor and / or ceramic or metal can be introduced into the hydrogel or organogel or composite material through the repetition of steps (a) and (b), the shrinkage observed when optionally converting the composite material into an inorganic material in an optional step (c) comprising a thermal treatment can be reduced to a significant degree. For example, without repeating steps (a) and (b) and performing step (c) immediately after step (a), shrinkage of more than 50% compared to the blank hydrogel may be observe. By repeating steps (a) and (b), the shrinkage may be reduced to 40% or less. Undesired warping and porosity in the obtained inorganic material caused by large shrinkage may thus be avoided. Furthermore, by using different inorganic precursor mixtures, it is possible to synthesize composite materials and / or inorganic materials containing different compositions, such as two or more metals, two or more ceramics, or both metals and ceramics. Moreover, by repeating steps (a) and (b) of the invention, possible solubility limitations of the HT / so 240174WO 04 March 2025 inorganic precursor can be overcome. This may also allow conducting steps (a) and / or (b) under mild conditions, such as low temperatures. In step (b) of the method according to the invention, the ceramic or metal is preferably obtained by a precipitation or a coprecipitation of the inorganic precursor in the inorganic precursor-containing solvent-containing gel. Advantageously, the reagents and / or stimuli used in step (b) of the method according to the invention may be selected from the group consisting of bases, photolatent bases, reducing agents, hydrolyzing agents, water, ultrasound, radiation, and mixtures and combinations thereof. Preferably, the reagents and / or stimuli are selected from the group consisting of sodium borohydride, ascorbic acid, sodium hydroxide, ammonia, glucose, hydrazine, trisodium citrate, hydroxylamine hydrochloride, potassium hydroxide, tetrabutylammonium hydroxide, ultrasound, UV light, and mixtures and combinations thereof. Particularly preferably the reagents and / or stimuli are selected from the group consisting of sodium borohydride, ascorbic acid, sodium hydroxide, ammonia, and mixtures thereof. It was found that by choosing suitable reagents and / or stimuli, it is possible to control the spatial distribution of the ceramic and / or metal within the composite material, which is difficult to achieve using the state-of-the-art hydrogel infusion additive manufacturing techniques. In a preferred embodiment, the reagents used in step (b) of the method according to the invention have a pKb value of from -30 to 30, referably, from 5 to 15, more preferably from -2 to 4, even more preferably from 0 to 2. In another preferred embodiment, the reagents used in step (b) of the method according to the invention have a pKb value of from -30 to 30, referably, from 5 to 15, more preferably from 4 to 10, and most preferably from 4 to 6. In another preferred embodiment, the reagents used in step (b) of the method according to the invention have a standard reduction potential of from -4.1 to +1.5 V vs. the standard hydrogen electrode (SHE), preferably from -4.1 to +0.8 V vs. SHE, HT / so 240174WO 04 March 2025 more preferably from -2.5 to -0.5 V vs. SHE, even more preferably from -2.0 to -0.5 V vs. SHE. In another preferred embodiment, the reagents used in step (b) of the method according to the invention have a standard reduction potential of from -4.1 to +1.5 V vs. the standard hydrogen electrode (SHE), preferably from -0.5 to +1.5 V vs. SHE, more preferably from 0.0 to +1.0 V vs. SHE. Step (b) may also be conducted at different temperatures. Advantageously, step (b) may be conducted at a temperature of 10°C to 90°C, preferably 10°C to 80°C, more preferably 15°C to 70°C. By varying the temperature at which step (b) is conducted, the properties of the resulting composite and / or the resulting inorganic material if optional step (c) is included may be adjusted. Without wishing to be bound by scientific theory, it is believed that reagents with a low pKb value, i.e. strong bases such as sodium hydroxide, can achieve the presence of ceramic and / or metal only in the surface areas of the composite material, which results in a core-shell type structure of the composite material. Alternatively, using reagents with low pKb value, i.e. weak bases such as ammonia, may result in the presence of ceramic and / or metal throughout the entire composite material. Without wishing to be bound by scientific theory, it is further believed that reagents with a very negative standard reduction potential vs. SHE, i.e. strong reductants such as sodium borohydride, may result in a thinner layer of distribution of the metal and / or ceramic in the surface region of the composite material, while reagents with a comparatively less negative standard reduction potential vs. SHE, i.e. weak reductants such as ascorbic acid, may result in a thicker layer of distribution of the metal and / or ceramic in the surface region of the composite material or even throughout the inside of the composite material. By choosing suitable reagents, it is also possible to distribute one metal or ceramic evenly throughout the composite material and to restrict a second metal or ceramic to the surface region of the composite material, resulting in a composite material with a core-shell structure. This core-shell structure HT / so 240174WO 04 March 2025 may also be present in an inorganic material that can be obtained in an optional step (c) comprising a thermal treatment. According to an embodiment, the composite material contains a metal, a metal alloy and / or a ceramic. The inorganic material obtained from the composite material may contain a metal, a metal alloy and / or a ceramic. The optional thermally treating in step (c) advantageously comprises debinding, pyrolysis, calcination, sintering, high-temperature annealing, or a combination thereof. Through this thermal treatment, the polymer phase of the composite material can be removed or converted into carbonaceous moieties, and the ceramics and / or metal particles can be sintered together to yield the desired inorganic material. The thermal treatment is preferably performed at temperatures from 50 to 1500°C, more preferably 100 to 1300°C. The heating rates employed for reaching these temperatures preferably range from 0.1 to 10 °C / min, more preferably from 0.1 to 5 °C / min. Heating protocols using various heating rates and / or constant intermediate heating plateaus may be employed in step (c). Debinding may also be conducted by applying a solvent to the composite material before an optional step (c). Various inorganic precursors can be used in the method according to the invention. According to an embodiment of the invention, each of the one or more inorganic precursors independently is a nitrate salt, an acetate salt, a chloride salt, a sulfate salt, a bicarbonate salt, an oxynitrate salt, a hydroxide salt, a bromide salt, a fluoride salt, an iodide salt, a chlorate salt, a cyanide salt, a cyanate salt, a thiocyanate salt, a phosphate salt, a dichromate salt, a perchlorate salt, a benzoate salt, a chromate salt, an acetylacetonate, an alkoxide such as a methoxide, an ethoxide, an isopropoxide, or any combination thereof. Preferably each of the one or more aqueous water-soluble inorganic precursors is a nitrate salt or a chloride salt. Most preferably each of the one or more aqueous water-soluble inorganic precursors is a nitrate salt. By selecting an HT / so 240174WO 04 March 2025 inorganic precursor with a high solubility in the chosen solvent, higher loadings of the metal and / or ceramic within the composite material can be achieved per cycle of steps (a) and (b) of the method according to the invention. The solvent of the inorganic precursor mixture may be selected from the group consisting of water, methanol, ethanol, isopropanol, diethyl ether, hexane, heptane, N,N-dimethylformamide, carbon tetrachloride and mixtures thereof. Preferably, the solvent is selected from the group consisting of water, methanol, ethanol, hexane, and mixtures thereof. More preferably, the solvent is water. The solvent of the blank hydrogel is preferably water. The solvent of the blank organogel may be selected from the group consisting of water, N,N- dimethylformamide, methanol, ethanol, isopropanol, diethyl ether, hexane, heptane, and mixtures thereof. The solvent of the organogel may be the same or different from the solvent of the inorganic precursor mixture. According to an embodiment, each of the one or more inorganic precursors used in the method according to the invention independently contains one or more elements selected from the group consisting of Fe, Zn, Li, Co, Al, Ni, Mo, La, In, Sn, Ba, Y, Ca, Bi, Sr, Cu, Ti, U, Zr, Mg, Pb, V, Na, K, Sc, Cr, Mn, Ga, Ag, Cd, Hf, W, Au, B, Si, Ge, As, Sb, Te, Se, Ce, P, Be or any combination thereof, preferably selected from the group consisting of Fe, Zn, Co, Ni, Y, Cu, Ag, B, Si, Ce, P, Al, Cr, or any combination thereof. Most preferably, each of the one or more inorganic precursors used in the method according to the invention contains one or more elements selected from the group consisting of Fe, Ag, Cu, Ni, Al, Cr, Ce or any combination thereof. By choosing an appropriate element or combination of elements, it is possible to synthesize a wide variety of inorganic materials with various functional and mechanical properties, such as magnetic or conductive inorganic materials. Inorganic precursors containing any one of the aforementioned metal elements in the form of ions are preferably used as aqueous solutions of the appropriate metal salt as the inorganic precursor mixture, more preferably the salts described herein. HT / so 240174WO 04 March 2025 In an embodiment of the method according to the invention, the inorganic precursor mixture comprises at least two different inorganic precursors. These may be, for example, ions of different metals, such as Fe2+and Ti2+, or ions of the same metal in different valence states, such as Fe2+and Fe3+, or ions and other compounds, such as Fe2+and Ti(OEt)4, or different compounds, such as Si(OEt)4 and Ti(OEt)4. This allows the synthesis of composite materials and / or inorganic materials comprising, for example, both metal and ceramic characteristics, or multi-metal structures or alloys. According to an embodiment, the composite material is exposed to a thermal- treatment atmosphere during optional step (c). The thermal-treatment atmosphere may in particular refer to chemical species, or lack thereof, in the gas / vapor space to which the thermally treated material (e.g., a hydrogel or a composite material) is exposed during the thermal treatment. Advantageously, the composite material is exposed to a thermal-treatment atmosphere during optional step (c), wherein the composition of the inorganic material is at least partially determined by the composition of the thermal-treatment atmosphere. By using different thermal-treatment atmospheres, it is possible to influence whether the resultant inorganic material is at least partially a metal or metal alloy, a ceramic, or a carbide. The thermal-treatment atmosphere during optional step (c) of the method according to the invention may be a reducing atmosphere and at least a portion of the inorganic material may be a metal or metal alloy. Alternatively, the thermal-treatment atmosphere may be an oxidizing atmosphere and at least a portion of the inorganic material may be a ceramic. Alternatively, the thermal-treatment atmosphere may be an inert atmosphere and at least a portion of the inorganic material may be a carbide. By choosing a suitable thermal-treatment atmosphere, it is possible to synthesize different types of inorganic materials, such as metals, ceramics, or carbides. HT / so 240174WO 04 March 2025 According to an embodiment, optional step (c) of the method according to the invention comprises a plurality of thermal treatment steps. In this way, it is possible to synthesize an inorganic material that is, for example, partially a metal and partially a ceramic. Furthermore, the rate of thermal degradation of the composite material can be controlled. Advantageously, a shrinkage of 80% or less, preferably 50% or less, particularly preferably 30% or less, of the inorganic material occurs during optional step (c) of the method according to the invention, compared to the composite material and / or the blank hydrogel. With conventional hydrogel infusion additive manufacturing techniques, due to the limited amount of inorganic precursor in the composite material, large amounts of shrinkage are typically observed upon thermal conversion. Since only a metal and / or a ceramic is left behind after a optional step (c) comprising a thermal treatment in particular in an oxidizing atmosphere, with the remainder of the composite material burned away, this significant reduction in mass results in large volume shrinkages during the process. This large shrinkage can result in undesirable warping and porosity in the final inorganic material. One possibility to avoid a high degree of shrinkage is an increase in the loading of metal and / or ceramic within the composite material. However, adapting the conventional method of printing a polymer composite resin to include a high loading of inorganic precursor in the printing slurry is difficult due to the increased viscosity of the slurry as well as light scattering by the inorganic precursor particles. The method according to the invention overcomes these challenges by adding the inorganic precursor to the hydrogel or organogel only after printing. Additionally, the method according to the invention allows higher loadings of the metal and / or ceramic within the composite material through the possibility to conduct multiple cycles of steps (a) and (b) of the method according to the invention, thus reducing the shrinkage during optional step (c). According to an embodiment, the blank hydrogel used in the method according to the invention is formed from an aqueous hydrogel precursor mixture using a photopolymerization, wherein the aqueous hydrogel precursor mixture comprises or HT / so 240174WO 04 March 2025 consists of water and one or more aqueous photosensitive binders. In an alternative embodiment, the blank organogel used in the method according to the invention is formed from a nonaqueous organogel precursor mixture using a photopolymerization, wherein the nonaqueous organogel precursor mixture comprises or consists of a non- water solvent, preferably a water-miscible non-water solvent, and one or more photosensitive binders. The blank organogel may in particular be further converted to a blank hydrogel by soaking it in water prior to further use. With conventional vat photopolymerization techniques, it is difficult to print composite materials because the presence of inorganic precursor particles causes light scattering, which lowers the accuracy and resolution of the printing process, and also high viscosity of the printing slurry, which lowers processability. In addition, adjustments need to be made to the vat photopolymerization process for each new inorganic precursor due to differences in scattering, viscosity, and compatibility. These disadvantages are avoided by using the method according to the invention, which employs blank hydrogels or blank organogels that are only treated with the inorganic precursor mixture after the photopolymerization has already taken place. Advantageously, the blank hydrogel or blank organogel used in the method according to the invention is prepared via an additive manufacturing process. This allows the preparation of complex three-dimensional structures to which the inorganic precursor mixture can then be added. Composite materials having a shape or structure with micron to sub-micron features can be achieved by using the method according to the invention. The corresponding inorganic materials that can be derived from these composite materials preferably have the same shape or structure. According to an embodiment of the invention, the method comprises the steps of: (a) swelling a blank hydrogel or a blank organogel using an inorganic precursor mixture to form an inorganic precursor-containing solvent- containing gel, wherein the inorganic precursor mixture comprises a solvent, preferably water, and one or more inorganic precursors; HT / so 240174WO 04 March 2025 (b) converting the inorganic precursor into ceramic or metal within the solvent-containing gel by introduction of reagents and / or stimuli to obtain a composite material; optionally repeating steps (a) and (b) at least once, preferably at least four times; (c) treating, preferably thermally treating, the composite material to form an inorganic material, preferably a ceramic or a metal. In this embodiment, steps (a) and (b) are preferably conducted at least twice, more preferably five times, before the composite structure is converted into an inorganic material in step (c) using a solvent or preferably by thermal treatment. The invention also relates to a composite material containing ceramic and / or metal obtainable by the method according to the invention. The invention further relates to an inorganic material containing ceramic and / or metal, obtainable by the method according to the invention. According to an embodiment of the composite material according to the invention, the composite material has a core-shell structure, the ceramic and / or the metal preferably being present in the shell. According to another embodiment, the inorganic material has a shell containing the ceramic and / or the metal and is hollow. As explained herein, core-shell structures or hollow structures can be achieved by choosing suitable reagents and / or stimuli during step (b) of the method according to the invention, so that a core-shell composite material is obtained, with the ceramic and / or metal present in the surface region of the composite material (i.e. the shell). During thermal treatment in optional step (c) of the method according to the invention, the polymeric parts of the composite material in both core and shell are preferably removed, leaving behind the metal and / or ceramic of the shell and resulting in a hollow inorganic material. Advantageously, the shell has a thickness of from 0.1 µm to 1000 µm, preferably from 0.5 µm to 500 µm, more preferably from 1 µm to 200 µm. The thickness of the shell HT / so 240174WO 04 March 2025 can be tuned by choosing reagents and / or stimuli during step (b) of the method according to the invention that have, for example, comparatively stronger or weaker reducing abilities. The thickness of the shell may also be tuned by repeating steps (a) and (b) of the method according to the invention as explained herein. The thickness of the shell may also be tuned by changing the temperature during step (b). In particular, the thickness of the shell may be increased by increasing the temperature in step (b). The thickness of the shell may also be increased by increasing the duration of step (b). In the following, the invention is further described by way of examples that are in no way meant to be limiting. DESCRIPTION OF FIGURES Fig.1 shows a scheme of steps (a) and (b) as well as optional step (c) of the method according to the invention. By using multiple rounds of infusion according to step (a) and coprecipitation according to step (b), the shrinkage during optional thermal conversion in step (c) may be reduced. Fig.2 shows an embodiment in which a blank hydrogel is swelled using a solution containing ions for swelling in step (a), the ions diffusing into the blank hydrogel yielding an ion-infused hydrogel as the inorganic precursor- containing solvent-containing gel. Upon introducing a reagent or a stimulus in step (b), the ions are converted to particles yielding a polymer composite as the composite material. Fig.3 shows a series of photographs illustrating steps (a) and (b) of the method of the invention starting from a blank hydrogel (labelled blank polymer in Fig. 3) that is swelled with an aqueous solution of FeCl3 and FeCl2 in step (a) to yield as an inorganic precursor-containing solvent containing gel an Fe2+ / Fe3+infused hydrogel (labelled Fe2+ / Fe3+infused polymer in Fig.3, upper path) that is subsequently converted into an iron oxide-containing HT / so 240174WO 04 March 2025 composite as a composite material (labelled iron oxide composite in Fig.3) by introducing reagents and / or stimuli according to step (b). Alternatively, the blank hydrogel is swelled with an aqueous silver nitrate solution in step (a) to yield as an inorganic precursor-containing solvent containing gel an Ag+infused hydrogel (labelled Ag+infused polymer in Fig.3, lower path) that is subsequently converted into a silver-containing composite as a composite material (labelled Ag Polymer composite in Fig.3) by introducing reagents and / or stimuli according to step (b). All scale bars in Fig.3 are 3 mm. Fig.4 shows examples of other composite materials such as a copper oxide- containing composite material (labelled CuO in Fig.4), a cerium oxide- containing composite material (labelled CeO2 in Fig.4), and a copper- containing composite material (labelled Cu in Fig.4). All scale bars in Fig.4 are 3 mm. Fig.5 shows a series of photographs illustrating steps (a) and (b) of the method of the invention as described in Example 1 below. All scale bars in Fig.5 are 3 mm. Fig.6a shows the increase in mass occurring in step (b) for a composite material relative to a blank hydrogel that was swelled with an aqueous solution containing Fe3+and Fe2+(Fe2+ / Fe3+= 1:1.8 ratio) according to Example 1, wherein different concentrations of the aqueous solution containing Fe3+and Fe2+were used before the introduction of NaOH. Fig.6b shows the increase in mass occurring in step (b) for a composite material relative to a blank hydrogel that was swelled with an aqueous solution containing Fe3+and Fe2+(Fe2+ / Fe3+= 1:1.8 ratio) according to Example 1, wherein the swelling (step (a)) and the precipitation using NH4OH (step (b)) HT / so 240174WO 04 March 2025 were repeated several times, each time using the same solution with the same concentration. Fig.7a shows X-ray diffractograms of the crushed composite hydrogels (as composite materials) obtained using NaOH as a reagent in step (b), solid line, as well as of Fe3O4 particles prepared in solution with the same reagents, dashed and dotted line. Fig.7b shows X-ray diffractograms of the crushed composite hydrogels (as composite materials) obtained using NH4OH as a reagent in step (b), dotted line, as well as of Fe3O4 particles prepared in solution with the same reagents, dashed line. Fig.8 shows X-ray diffractograms of crushed composite hydrogels (as composite materials) obtained using NH4OH as a reagent in step (b), wherein steps (a) and (b) were not repeated (dashed line), repeated twice (dotted line) or four times (solid line). Fig.9a shows a scanning electron microscopy (SEM) image of a cross-section of a composite material prepared according to Example 1 using NaOH (top) as well as an energy dispersive X-ray spectroscopy (EDS) spectrum (bottom) of a line scan along the white line in the top part of the Figure. Fig.9b shows a scanning electron microscopy (SEM) image of a cross-section of a composite material prepared according to Example 1 using NH4OH (top) as well as an energy dispersive X-ray spectroscopy (EDS) spectrum (bottom) of a line scan along the white line in the top part of the Figure (two repetitions of steps (a) and (b)). Fig.10a shows an SEM image of a cross-section of a composite material prepared according to Example 1 using NH4OH (top) as well as an energy dispersive X- HT / so 240174WO 04 March 2025 ray spectroscopy (EDS) spectrum (bottom) of a line scan along the white line in the top part of the Figure (no repetition of steps (a) and (b)). Fig.10b shows an SEM image of a cross-section of a composite material prepared according to Example 1 using NH4OH (top) as well as an energy dispersive X- ray spectroscopy (EDS) spectrum (bottom) of a line scan along the white line in the top part of the Figure (two repetitions of steps (a) and (b)). Fig.11 shows a graph of the thickness of Fe3O4 composite hydrogels (as composite materials) made with NaOH according to Example 1 versus the time during the coprecipitation of step (b) at 50°C (dashed line) and at 70°C (solid line). Fig.12 shows a graph of the magnetization versus the magnetic field of Fe3O4 composite hydrogels (as composite materials) prepared using NH4OH in step (b) (solid line) or NaOH in step (b) (dashed line). The conditions were otherwise as in Example 1. Fig.13 shows a graph of the magnetization versus the magnetic field of Fe3O4 composite hydrogels (as composite materials) prepared using NaOH in step (b), wherein the temperature in step (b) was 25°C (solid line), 50°C (dashed line) or 70°C (dotted line). The conditions were otherwise as in Example 1. Fig.14 shows a graph of the magnetization versus the magnetic field of Fe3O4 composite hydrogels (as composite materials) prepared using NH4OH in step (b), wherein the number of repetitions of steps (a) and (b) were increased (solid line: no repetition; dashed line: two repetitions; dotted line: four repetitions). The conditions were otherwise as in Example 1. Fig.15 shows a series of photographs illustrating steps (a) and (b) of the method of the invention applied in Example 2 below and starting from a blank hydrogel that is swelled with an aqueous silver nitrate solution in step (a) (labelled HT / so 240174WO 04 March 2025 Swell-in in Fig.15) to yield as an inorganic precursor-containing solvent containing gel an Ag+infused hydrogel (labelled Ag gel in Fig.15) that is subsequently converted into a silver-containing composite as a composite material using NaBH4 (labelled NaBH4 in Fig.15) or ascorbic acid (labelled Ascorbic Acid in Fig.15) as reagents and / or stimuli according to step (b). All scale bars are 3 mm. Fig.16 shows X-ray diffractograms of the crushed composites made using NaBH4 and ascorbic acid (solid line: NaBH4; dashed and dotted line: ascorbic acid). Fig.17a shows an SEM image of a cross-section of a composite material prepared according to Example 2 using NaBH4 (top) as well as an EDS spectrum (bottom) of a line scan along the white line in the top part of the Figure. Fig.17b shows an SEM image of a cross-section of a composite material prepared according to Example 2 using ascorbic acid (top) as well as an EDS spectrum (bottom) of a line scan along the white line in the top part of the Figure. Fig.18 shows a graph of the thickness of the silver composite hydrogel (as composite material) shell versus the duration of step (b) according to Example 2. Fig.19 shows an SEM image of a cross section of a silver composite gel (as composite material) prepared according to Example 2 using ascorbic acid (5 repetitions). The light regions correspond to silver particles. The dark regions are the polymer. The cut was prepared using a focused-ion beam. Fig.20 shows a series of photographs illustrating step (b) and optional step (c) of the method of the invention applied in Example 3 below and starting from a silver composite hydrogel into which NaBH4 is introduced as reagents and / or stimuli according to step (b) as detailed for Example 2 (labelled Co- HT / so 240174WO 04 March 2025 precipitation in Fig.20). Subsequent heating the silver composite hydrogel in air in optional step (c) (labelled Calcination in Fig.20) yielded a hollow silver structure, wherein the hollow nature of the structure can be seen in the magnified photograph in Fig.20. Scale bars are as indicated in Fig.20. Fig.21 shows the mass increase of the hydrogels of Example 7 as a function of infusion temperature and time. The infusion solution contained 1.5M Fe2+and 2.7M Fe3+. The masses measured were the dry masses of the hydrogel, i.e. after drying. Fig.22 shows the mass increase of the composites as a function of coprecipitation temperature and time.30 vol% ammonia was used to initiate the coprecipitation process. The masses measured were the dry masses of the composite, i.e. after drying. Fig.23 shows the mass increase of the hydrogel composite as a function of infusion- coprecipitation cycles. The masses measured were the dry masses of the composite, i.e. after drying. Fig.24 shows an EDS line scan of a gold-coated cross-section of a five-cycle IONP composite (coprecipitation temperature of 30˚C). Iron was detected throughout the structure. Fig.25 shows a histogram of IONP sizes measured from SEM images taken from cross-sections of an IONP composite (five-cycles, 30˚C). Fig.26 shows XRD patterns of crushed IONP hydrogel composites fabricated using different number of infusion-coprecipitation cycles and precipitation temperatures. HT / so 240174WO 04 March 2025 Fig.27a-e show hysteresis loops (measured by VSM, 300 K) of dried IONP composites fabricated at varying temperatures and number of infusion- coprecipitation cycles. Fig.28 shows representative engineering stress-strain curves (measured in compression) of dried IONP composites fabricated at varying temperatures and number of infusion-coprecipitation cycles. Fig.29 shows the resistivity of the dried silver hydrogel composites as a function of the number of in-situ silver synthesis cycles. Fig.30 shows the X-ray diffraction pattern from pulverized Ag composites. Fig.31 shows the mass increase of the dried silver hydrogel composites as a function of the number of in-situ silver synthesis cycles. Fig.32 shows EDS line scans of Ag-IONP composite cross-sections. Iron was detected across the entire line indicating that the IONP was distributed homogenously throughout the structure. Silver was only detected within 30 µm of the surface. The EDS line scan suggests that the Ag-IONP composite had a core shell like microstructure, with an IONP composite core and an Ag- IONP composite shell. Fig.33 shows the mass increase of the hydrogels as a function of infusion temperture and time. The infusion solution contained 1.5M Fe2+and 2.7M Fe3+. The masses measured were the dry masses of the hydrogel, i.e. after drying. Fig.34 shows the mass increase of the hydrogel composite as a function of infusion- coprecipitation cycles. The masses measured were the dry masses of the composite, i.e. after drying. HT / so 240174WO 04 March 2025 Fig.35 shows optical images of the hydrogels throughout different cycles of infusion and coprecipitation process. Fig.36a-b show a sample SEM image and a histogram of IONP sizes measured from SEM images taken from cross-sections of an IONP composite (10-cycles). Scale bar: 200 nm. Fig.37a-c show µCT scan images of composites dried at a) room temperature, b) 65°C and c) 4°C (with drying agent). Scale bars: 200 μm. Fig.38a-b show TGA plots of the first two steps of thermal treatments (debinding in N2 and sintering in air) on dried composites prepared with 10 cycles of infusion-coprecipitation and final soaking in iron salt solution. Fig.39 shows XRD patterns of powders prepared from pulverizing the 3D ceramic structures. The IONP composite structures were converted into Fe2O3 after the two-step debinding and sintering thermal treatments. Fig.40 shows XRD patterns of the flattened metal structure revealed that the Fe2O3 structures were successfully reduced into Fe after heating in forming gas. Fig.41 shows Optical images of the dried 10-cycle infused composite structure, the Fe2O3 structure, and the Fe structure. Fig.42 µCT scan of iron lattice. Scale bar: 200 μm. EXAMPLES Materials HT / so 240174WO 04 March 2025 FeCl3.6H2O (97%, Sigma-Aldrich), FeCl2.4H2O (98%, Sigma-Aldrich), NaOH solution (50% in H2O, Sigma-Aldrich), NH4OH solution (28.0-30.0%, Sigma-Aldrich), AgNO3 (99%, Sigma-Aldrich), NaBH4 (98%, Sigma-Aldrich), L-Ascorbic Acid (99%, Sigma- Aldrich), poly(ethylene glycol) diacrylate Mn = 700 (PEGda) (Sigma-Aldrich), tartrazine (≥85%, Sigma-Aldrich), lithium phenyl-2,4,6-trimethylbenzoylphosphinate (LAP) (≥95%, Sigma-Aldrich). Cu(NO3)2.3H2O (99-104%, Sigma-Aldrich), Ce(NO3)3.6H2O (99%, Sigma-Aldrich) Analytical Methods X-ray diffraction (XRD) XRD (Bruker D8 Advance Diffractometer) data was collected at 40 kV and 40 mA using a Cu source. All powders were obtained by grinding with a mortar and pestle. Energy-dispersive X-ray spectroscopy (EDS) EDS data was generated in a Zeiss GEMINI 2 equipped with an Oxford X-Max SDD EDS system. The applied voltage of Fe3O4 and Ag composites were 12kV and 10 kV respectively. Vibrating sample magnetometry (VSM) VSM data was collected in a Quantum Design PPMS DynaCool measurement system equipped with vibrating sample magnetometer kit. The temperature was 300K and the atmosphere pressure was about 26Torr. Example 1: In-situ synthesis of Fe3O4 particles within a 3D-printed hydrogel A printed blank hydrogel was soaked in an aqueous solution containing Fe3+and Fe2+ions (Fe2+ / Fe3+= 1:1.8 ratio) at 65°C for 3 h (Fig.5, step Swell-in). The iron-ion infused hydrogel (Fig.5, Fe gel) was then placed in either an 1M NaOH solution (Fig.5, step NaOH) or a 30 vol% NH4OH solution (Fig.5, step NH4OH) to induce the coprecipitation of Fe3O4 particles within the hydrogel. The iron-ion infused hydrogel was soaked in the base (NaOH or NH4OH) at 50°C for 5 min. Finally, the composite hydrogel (as composite material) was washed with deionized water for 3 times and HT / so 240174WO 04 March 2025 then soaked in deionized water for 12 h before drying. The final product obtained by this method had magnetic properties. X-ray diffraction (XRD) of the crushed composite hydrogels confirmed that the particles were Fe3O4 (Fig.7a and 7b, solid line). Fe3O4 composite hydrogels (as composite materials) made with NaOH had an Fe3O4 composite hydrogel shell and a hydrogel core, while Fe3O4 composite hydrogels made with NH4OH had a much more even distribution of Fe3O4 particles within the hydrogel. The difference in particle distributions was confirmed by energy-dispersive X-ray spectroscopy (EDS) line scans of cross-sections of the Fe3O4 composite hydrogels. The EDS iron signal was only detected near the surface for the NaOH samples but was present throughout the volume of the NH4OH samples. The mass of Fe3O4 particles within the composite hydrogel (as composite material) could be controlled in different ways. Increasing the concentration of iron salts used in the initial swelling solution led to an increase in the mass of Fe3O4 particles in the composite as shown in Fig.6a. Fig.6a further shows that the mass change and thus the amount of iron oxide within the hydrogel achieved for the Fe3O4 particle-containing composite gel (as composite material) relative to the blank hydrogel reproducibly depends on the concentration of the iron salt solution used for the swelling in step (a). The concentration denoted on the x-axis in Fig.6a was calculated based on the total mass of both salts in the solution. The conditions for step (b) were as described above in Example 1. The mass of Fe3O4 particles within the composite hydrogel (as composite material) could also be increased by repeating the infusion and coprecipitation cycles as shown in Fig.6b. Fig.6b further shows that the mass change and thus the amount of iron oxide within the hydrogel achieved for the Fe3O4 particle-containing composite gel (as composite material) relative to the blank hydrogel reproducibly depends on the number of repetitions (1 round being no repetition of steps (a) and (b), 2 being 1 HT / so 240174WO 04 March 2025 repetition of steps (a) and (b) etc.). The conditions for step (b) were as described above in Example 1. A comparison of Fe3O4 particles prepared in solution with the same reagents to the crushed composite Fe3O4 particle-containing hydrogels showed that the particles synthesized within the hydrogel were not as crystalline (see Fig.7a and 7b, solid and dotted lines for the composite hydrogels and dashed line as well as dashed and dotted line for the particles prepared in solution). Multiple rounds of coprecipitation using NH4OH did not change the crystallinity of the iron oxide particles significantly (Figure 8, dashed line one precipitation (no repetition), dotted line two repetitions, solid line four repetitions). The large difference in mass change between the NaOH and NH4OH systems evidenced by Fig.6a and 6b is due to the difference in the particle distributions within the polymer composite. Iron oxide polymer composites (as composite material) made with NaOH had an iron oxide polymer composite shell and a polymer core, while iron oxide polymer composites made with NH4OH had a much more even distribution of iron oxide particles within the polymer, as can be seen from Fig.9a for NaOH and from Fig.9b for NH4OH. Since the iron oxide particles for the NaOH precipitation are only confined to the surface, the mass increase is lower than for the NH4OH systems. This is evident from Fig.9a showing an EDS spectrum of a line scan along the white line in the top SEM image of a cross-section of an iron-oxide polymer composite obtained using NaOH in step (b) according to Example 1. The EDS spectrum in Fig.9a shows that the EDS iron signal was only detected near the surface. Fig.9b shows an EDS spectrum of a line scan along the white line in the top SEM image of a cross-section of an iron- oxide polymer composite (as composite material) obtained using NH4OH in step (b) according to Example 1. The EDS spectrum in Fig.9b shows that the EDS iron signal was detected throughout the volume of the structure. HT / so 240174WO 04 March 2025 The intensity of the iron EDS line scan signals increased with the number of infusion and coprecipitation rounds for the NH4OH samples as can be seen in Fig.10a and Fig. 10b. For the Fe3O4 composite hydrogels (as composite material) made with NaOH, the thickness of the Fe3O4 composite hydrogel shell could be controlled by varying the temperature and time during the coprecipitation. Increasing the temperature and / or time both increased the thickness of the shell as shown in Fig.11 for 50°C (dashed line) and at 70°C (solid line) in step (b) and for varying coprecipitation times in step (b). The thickness was determined from the EDS line scans obtained from the respective SEM images. The magnetic properties of the Fe3O4 composite hydrogels were determined using a vibrating sample magnetometer (VSM) as shown in Fig.12. The magnetic properties of samples made using NaOH (see Fig.12, dashed line) were more pronounced than those of the sample made using NH4OH (see Fig.12, solid line). Moreover, for the composite hydrogels (as composite materials) made using NaOH, increasing the temperature during the coprecipitation process (step (b)) further increased the magnetic properties of the composite hydrogel as shown in Fig.13 for a temperature in step (b) of 25°C (solid line), 50°C (dashed line) or 70°C (dotted line). For the Fe3O4 composite hydrogels (as composite materials) prepared using NH4OH, increasing the number of infusion and coprecipitation cycles increased the magnetic properties of the composite hydrogel since the mass of Fe3O4 within the composite hydrogel was increased as shown in Fig.14 for different numbers of repetitions (Fig. 14–-solid line: no repetition; dashed line: two repetitions; dotted line: four repetitions). Example 2: In-situ synthesis of Ag particles within a 3D printed hydrogel HT / so 240174WO 04 March 2025 A printed blank hydrogel was soaked in an aqueous solution containing Ag+ions at 65°C for 3 h. The silver-ion infused hydrogel was then placed in either a 5 mg / mL NaBH4 solution or a 1Mascorbic acid solution to grow Ag nanoparticles in-situ. For NaBH4, the reaction time was 5 min at 0°C, while for ascorbic acid the reaction time was 25 min at 20°C. Finally, the composite hydrogel (as composite material) was washed with deionized water for 3 times and then soaked in deionized water for 12 h before drying. The final product obtained was conductive. Fig.15 shows photographs showing the blank hydrogel, the silver-ion infused hydrogel (Fig.15, Ag gel), and the silver-containing composites (as composite material) obtained using NaBH4 and ascorbic acid. XRD of the crushed silver composite hydrogels confirmed that the particles were silver as shown in Fig.16 (solid line: NaBH4; dashed and dotted line: ascorbic acid). Similar to Example 1, the choice of reagent impacted the distribution of silver in the composite. Both NaBH4 and ascorbic acid resulted in core-shell structures consisting of a silver composite hydrogel shell and a hydrogel core (see Fig.17a and Fig.17b). However, the thickness of the silver composite hydrogel shell was thicker for the ascorbic acid samples (≈150 µm, Fig.17b) than for the NaBH4 samples (≈50 µm, Fig. 17a). The shell thicknesses were determined via EDS line scans of cross-sections of the silver composite hydrogels (see Fig.17a and Fig.17b). For the samples in Example 2 prepared with NaBH4, increasing the reaction time from 5 to 15 min increased the thickness of the silver composite hydrogel shell (see Fig. 18). The NaBH4 concentration was 5 mg / mL, the temperature was 0°C, the duration was as indicated in Fig.18. The thickness was determined by the EDS line scans obtained from the SEM images. However, it was still not as thick as those prepared using ascorbic acid. Figure 19 shows an SEM image of a cross section of a silver composite gel (as composite material) prepared using ascorbic acid (5 repetitions of infusion and HT / so 240174WO 04 March 2025 precipitation). The light regions correspond to silver particles. The dark regions are the polymer. The cut was prepared using a focused-ion beam. It is clear that silver can be found 100s of microns into the surface of the composite gel. Example 3: Fabrication of hollow silver structures via in-situ synthesis of Ag particles within a 3D-printed hydrogel followed by calcination Hollow silver structures could be fabricated by calcination (thermal treatment in air) of the silver composite hydrogels (subjecting the composite material to optional step (c)). Since synthesis with NaBH4 resulted in a core-shell structure (see Example 2), heating the silver composite hydrogel in air resulted in the thermal degradation of the hydrogel in both the core and the shell, leaving behind the silver that was only present in the shell layer as shown in Fig.20 showing step (b) and optional step (c) of the method according to the invention for the silver composite hydrogel. Example 4: In-situ synthesis of CuO particles within a 3D-printed hydrogel (Composite material) A printed blank hydrogel was soaked in a 1g / mL aqueous solution of copper (II) nitrate trihydrate. Then, the copper-ion infused hydrogel was placed in an 1M NaOH solution at 50˚C for 5 minutes to induce the formation of CuO nanoparticles within the hydrogel. Finally, the composite hydrogel was washed with deionized water for 3 times and then soaked in deionized water for 12 h before drying. The final product obtained by this method (see Fig.4, CuO) could be used for sensing. Example 5: In-situ synthesis of CeO2 particles within a 3D-printed hydrogel (Composite material) A printed blank hydrogel was soaked in a 1g / mL aqueous solution of cerium nitrate hexahydrate. Then, the cerium-ion infused hydrogel was placed in an 1M NaOH solution at 50˚C for 5 minutes to induce the formation of CeO2 nanoparticles within the hydrogel. Finally, the composite hydrogel was washed with deionized water for 3 times and then soaked in deionized water for 12 h before drying (Fig.4, CeO2). HT / so 240174WO 04 March 2025 Example 6: In-situ synthesis of Cu particles within a 3D-printed hydrogel (Composite material) A printed blank hydrogel was soaked in a 1g / mL aqueous solution of copper nitrate trihydrate. Then, the copper-ion infused hydrogel was placed in a 5 mg / mL NaBH4 solution at 0˚C for 15 minutes to induce the formation of Cu nanoparticles within the hydrogel. Finally, the composite hydrogel was washed with deionized water for 3 times and then soaked in deionized water for 12 h before drying (Fig.4, Cu). Example 7: In-situ synthesis of iron oxide nanoparticles (IONP) within a 3D printed hydrogel fabricated using volumetric additive manufacturing A “blank” poly(ethylene glycol) diacrylate-based hydrogel photoresin was prepared by first mixing 0.65 mg of 2,2,6,6-tetramethylpiperidin-1-yl)oxyl (TEMPO) and 3 mg DCPI 3001 (a dual-color photoiniator from xolo GmbH) in 75 µL dimethyl sulfoxide (DMSO). The TEMPO-DCPI-DMSO solution was then added to a mixture of 15 g of xoloPEGDA Component A (a proprietary base mixture of water, coinitiator, and rheology modifier used for preparation of various hydrogel formulations for Xolography) and 10 g of poly(ethylene glycol) diacrylate Mn = 700 (PEGDA 700) in a 50 mL centrifuge tube. The resin was then mechanically stirred followed by centrifugation at 4000 RPM for 5 minutes to remove residual air bubbles. The hydrogel photoresin was then used with Xolography, a volumetric additive manufacturing technology, to fabricate the “blank” hydrogel structures. The ”blank” hydrogel structures were then soaked in an aqueous solution containing 2.7M Fe3+and 1.5M Fe2+ions to infuse them with iron ions. The hydrogel was soaked in the iron-ion solution for varying temperatures and time to control the amount of iron-ions infused into the hydrogel (Figure 21). Increasing the infusion temperature and time led to an increase in the mass of iron-ions infused into the hydrogel. An infusion time of 2 hours and an infusion temperature of 60˚C was chosen for the purposes of this example. Post-infusion, the iron-ion infused hydrogels were removed from the iron-ion solution and dabbed dry with a paper towel to remove any excess HT / so 240174WO 04 March 2025 iron solution from the structure. Hydrogels infused under these conditions (60˚C, 2 hours) had a 70% increase in mass after drying. The iron-ion infused hydrogels were then immersed in a 30 vol% ammonia solution at either 30˚C or 60˚C to initiate the coprecipitation reaction. The orange-brown iron-ion infused hydrogels turned black almost immediately on contact with the ammonia solution. The iron-ion infused hydrogels were left in the ammonia solution for some time (5, 10, or 15 minutes), removed from the ammonia solution, washed with deionized water thrice, ultrasonicated in water for 30 seconds, and then soaked in deionized water for 1 hour to remove any excess ammonia in the hydrogel composite. The black IONP hydrogel composites were then dried and weighed to determine the impact of the ammonia coprecipitation conditions on the mass change. As seen in Figure 22, there was no significant difference between all combinations of coprecipitation temperatures (30˚C vs.60˚C) and times (5 vs.10 vs.15 minutes). The IONP hydrogel composites exhibited a 25 – 30% increase in mass as compared to the initial “blank” polymer. For the purposes of this example, coprecipitation was conducted for 5 minutes at 30˚C or 60˚C. The infusion-coprecipitation process described above was repeated to increase the mass of IONP in the hydrogel composites. Figure 23 shows the mass change of the composite as a function of infusion-coprecipitation cycles. The increase in composite mass was found to be almost linear with the number of infusion-coprecipitation cycles. With our approach, we were able to fabricate composites with up to 65 wt% of fillers (IONP). Composites with such high wt% of fillers are extremely difficult to achieve with other VP methods due to the high viscosities of such slurry resins (resins that contain particles). In addition, in the context of volumetric additive manufacturing, which requires highly transparent resins and thus cannot be used to fabricate composites, our approach now enables this capability. HT / so 240174WO 04 March 2025 Energy-dispersive X-ray spectroscopy (EDS) line scans of gold-coated cross-sections of a five-cycle IONP composite (coprecipitation temperature of 30˚C) revealed that iron was detected throughout the entire structure (Figure 24). This indicates that our in-situ synthesis approach enables the fabrication of IONP composites with a homogeneous distribution of IONP. The nanoparticles in the structure, as observed from scanning electron microscopy (SEM), were determined to be approximately spherical in shape with a size of 38 ^ 13 nm (Figure 25). X-ray diffraction (XRD) of the pulverized composite hydrogels confirmed that the particles were Fe3O4 (Figure 26). The magnetic properties of the IONP composites were determined using a vibrating- sample magnetometer (VSM) (Figure 27a-e). As expected, increasing the number of growth cycles, and thus the mass of IONPs in the composite, led to a direct increase in its magnetic properties. In addition, composites fabricated at higher coprecipitation temperatures (60˚C instead of 30˚C) had a marked increase in their magnetization despite having a similar amount of IONP in the hydrogel (Figure 23). For example, at 15 kOe, a 3-cycle composite fabricated at 30˚C exhibited a magnetization of approximately 5 emu / g whereas its counterpart fabricated at 60˚C had a magnetization of around 15 emu / g instead. Importantly, the results from Figure 27a-e showed that coprecipitation temperature, instead of growth rounds, played a much larger role in dictating the composite magnetic properties — at 15 kOe, a 1-cycle composite fabricated at 60˚C had similar magnetic properties as a 3-cycle composite fabricated at 30˚C. The mechanical properties of the IONP composites were also measured under compression (Figure 28). Compared to the “blank” polymers, all the composites showed a significant increase in their compressive strength. We also observed a qualitative increase in the stiffness with the number of growth cycles, which is expected since the composite stiffness should be a function of the wt% of IONPs in the HT / so 240174WO 04 March 2025 composite. The strain at the onset of structural failure was observed to increase and then decrease with the number of growth cycles. For example, at a coprecipitation temperature of 30˚C, the 3-cycle and 5-cycle composites had a maximum compressive stress of approximately 2.52 ^ 0.13 and 3.87 ^ 0.39 MPa and an onset of structural failure strain of 0.24 ^ 0.01 and 0.16 ^ 0.01 respectively. For comparison, the “blank” polymer had a maximum compressive stress and failure strain of 0.03 ^ 0.01 MPa and 0.17 ^ 0.02 respectively. Example 8: In-situ synthesis of silver nanoparticles within a 3D printed hydrogel fabricated using volumetric additive manufacturing A “blank” poly(ethylene glycol) diacrylate-based hydrogel photoresin was prepared by first mixing 0.65 mg of 2,2,6,6-tetramethylpiperidin-1-yl)oxyl (TEMPO) and 3 mg DCPI 3001 (a dual-color photoiniator from xolo GmbH) in 75 µL dimethyl sulfoxide (DMSO). The TEMPO-DCPI-DMSO solution was then added to a mixture of 15 g of xoloPEGDA Component A (a proprietary base mixture of water, coinitiator, and rheology modifier used for preparation of various hydrogel formulations for Xolography) and 10 g of poly(ethylene glycol) diacrylate Mn = 700 (PEGDA 700) in a 50 mL centrifuge tube. The resin was then mechanically stirred followed by centrifugation at 4000 RPM for 5 minutes to remove residual air bubbles. The hydrogel photoresin was then used with Xolography, a volumetric additive manufacturing technology, to fabricate the “blank” hydrogel structures. The ”blank” hydrogel structures were then soaked in an aqueous solution in an aqueous solution containing 2M Ag+ions for 1 hour at 60˚C. The silver-ion infused hydrogels were then immersed in an ice-cold 5 mg / mL sodium borohydride solution to initiate the in-situ synthesis of silver nanoparticles. The reaction time was 5 minutes. The silver composites were washed 3 times with deionized water and then ultrasonicated in water for 30 seconds to remove any excess silver nanoparticles on the surface. The structures were then soaked in fresh deionized water for 1 hour before further treatments. HT / so 240174WO 04 March 2025 The dried Ag composites appeared silver and had a resistivity of approximately 0.2 ^m (Figure 29), which was sufficiently low to close an electrical circuit. X-ray diffraction (XRD) (Figure 30) confirmed the presence of silver in the composite, validating the success of the in-situ reduction reaction. The mass of silver in the Ag hydrogel composite could be increased by repeating the silver infusion-reduction cycle (Figure 31), which resulted in a concomitant decrease in its resistivity — after two cycles of silver growth, the Ag composites exhibited a resistivity of approximately 0.01 ^m (Figure 29). Example 9: In-situ synthesis of silver and iron oxide nanoparticles within a 3D printed hydrogel fabricated using volumetric additive manufacturing A “blank” poly(ethylene glycol) diacrylate-based hydrogel photoresin was prepared by first mixing 0.65 mg of 2,2,6,6-tetramethylpiperidin-1-yl)oxyl (TEMPO) and 3 mg DCPI 3001 (a dual-color photoiniator from xolo GmbH) in 75 µL dimethyl sulfoxide (DMSO). The TEMPO-DCPI-DMSO solution was then added to a mixture of 15 g of xoloPEGDA Component A (a proprietary base mixture of water, coinitiator, and rheology modifier used for preparation of various hydrogel formulations for Xolography) and 10 g of poly(ethylene glycol) diacrylate Mn = 700 (PEGDA 700) in a 50 mL centrifuge tube. The resin was then mechanically stirred followed by centrifugation at 4000 RPM for 5 minutes to remove residual air bubbles. The hydrogel photoresin was then used with Xolography, a volumetric additive manufacturing technology, to fabricate the “blank” hydrogel structures. The ”blank” hydrogel structures were then subjected to three-cycles of in-situ IONP growth, followed by two-cycles of in-situ silver nanoparticle growth. The IONP in-situ synthesis conditions are identical to that outlined in Example 7. In brief, a 1.5M Fe2+and 2.7M Fe3+solution was first prepared. The “blank” hydrogels were HT / so 240174WO 04 March 2025 first soaked in the iron-ion solution at 60˚C for 2 hours to infuse them with iron-ions. The iron-ion infused hydrogels were dabbed dry with a paper towel and then immersed in a 30˚C 30 vol% ammonia solution for 5 minutes. Post-coprecipitation, the IONP composites were washed with deionized water thrice, ultrasonicated in water for 30 seconds, and then soaked in water for 1 hour. The iron infusion-coprecipitation process was then repeated two more times. The silver in-situ synthesis conditions are identical to that outlined in Example 8. In brief, the three-cycle IONP hydrogel composites were soaked in a 2M Ag+solution at 60˚C for 1 hour. The silver-ion infused IONP hydrogel composites were dabbed dry with a paper towel before being immersed in an ice-cold 5 mg / mL sodium borohydride solution for 5 minutes. Post silver precipitation, the Ag-IONP hydrogel composites were washed with water thrice, ultrasonicated in water for 30 seconds, and then soaked in water for 1 hour to remove any byproducts formed during the reduction process. The silver infusion-coprecipitation process was then repeated one more time. The Ag-IONP composites appeared outwardly silver but still maintained their magnetic properties, as they can be manipulated using an external magnet. EDS line scans of dried IONP-Ag composite cross-sections revealed a core-shell microstructure, with iron distributed homogenously throughout the beam, and silver only present within 30 µm of the surface (Figure 32). A possible explanation for the inhomogeneous growth of silver is the rapid kinetics of silver nanoparticle formation as compared to IONP. As sodium borohydride rapidly reduce metal ions, it is possible that it is unable to diffuse far into the volume of the structure as it is rapidly being consumed by the counter-diffusing silver ions. Regardless of the shell-formation mechanism, these results highlight the ability of the method according to the invention to fabricate multifunctional composites using our infusion-precipitation approach. In addition, they also show that core-shell composites can be fabricated with the inventive approach, which is impossible with conventional composite printing methods that utilize slurry resins. HT / so 240174WO 04 March 2025 Example 10: Multi-material structures via spatial control of the in-situ synthesis of iron oxide nanoparticles within a 3D printed hydrogel fabricated using volumetric additive manufacturing The method according to the invention, in particular the in-situ synthesis approach, also enables the fabrication of multi-material structures that are challenging to achieve with state-of-the-art VP technology. Since the fillers are not incorporated into the resin but instead grown under specific reaction conditions, their formation can be spatially controlled by selectively initiating the (co)precipitation reactions. To demonstrate the feasibility of the multi-material printing process, printed springs and pendulums were printed using Xolography and selectively grew IONP in the structure to enable remote actuation with an external magnet. To achieve spatial growth, the spring and pendulum structures were first partially soaked in iron salt solution (1.5M Fe2+and 2.7M Fe3+) at 60 ˚C for 1 hour. The spring structure was carefully positioned such that only the top base plate of the spring structure came into contact with the iron salt solution. Similarly, the pendulum structure was positioned in a way that only the pendulum joint of the structure came into contact with the infusion solution. The spatially infused samples were then completely immersed in ammonium hydroxide solution at room temperature for 10 mins to initiate the in-situ synthesis of IONP in the iron-ion infused areas. The multi- material IONP composites were then washed 3 times with deionized water and ultrasonicated in water for 30 seconds to remove any excess iron oxide nanoparticles on the surface. Following that, the structures were soaked in fresh deionized water for 1 hour to remove any excess ammonia solution. The spatial-infusion global- coprecipitation process was repeated 2 more times for a total of 3 cycles. The multi-material spring and pendulum structures could then remotely actuated using an external magnet. For clarity, the multi-material structure is made of the following two materials — material 1: IONP hydrogel composite; material 2: hydrogel. HT / so 240174WO 04 March 2025 Example 11: Iron structure fabricated via repeated in-situ synthesis of iron oxide within DLP printed hydrogels followed by thermal treatment. A “blank” poly(ethylene glycol) diacrylate-based hydrogel photoresin was prepared by first mixing 20 mg of Lithium phenyl-2,4,6-trimethylbenzoylphosphinate (LAP) and 15 mg Tartrazine in 5 mL deionized water. The LAP-Tartrazine aqueous solution was then added to 5 mL of poly(ethylene glycol) diacrylate Mn = 700 (PEGDA 700) in a 15 mL centrifuge tube. The resin was then mechanically stirred followed by standing for 30 minutes to remove residual air bubbles. The hydrogel photoresin was then used with a digital light processing (DLP) printer to fabricate the “blank” hydrogel structures. The ”blank” hydrogel structures were then soaked in an aqueous solution containing 2.7M Fe3+and 1.5M Fe2+ions to infuse them with iron ions. The hydrogel was soaked in the iron-ion solution for varying temperatures and time to control the amount of iron- ions infused into the hydrogel (Figure 33). Increasing the infusion temperature and time led to an increase in the mass of iron-ions infused into the hydrogel. An infusion time of 1 hours and an infusion temperature of 65˚C was chosen for the purposes of this example. Post-infusion, the iron-ion infused hydrogels were removed from the iron-ion solution and dabbed dry with a paper towel to remove any excess iron solution from the structure. Hydrogels infused under these conditions (65˚C, 1 hours) had an approximately 75% increase in mass after drying. The iron-ion infused hydrogels were then immersed in a 30 vol% ammonia solution at room temperature to initiate the coprecipitation reaction. The orange-brown iron-ion infused hydrogels turned black almost immediately on contact with the ammonia solution. The iron-ion infused hydrogels were left in the ammonia solution for 5 minutes, removed from the ammonia solution, washed with deionized water thrice, ultrasonicated in water for 30 seconds, and then soaked in deionized water for 1 hour to remove any excess ammonia in the hydrogel composite. The black IONP hydrogel composites were then dried and weighed. The infusion-coprecipitation process HT / so 240174WO 04 March 2025 described above was repeated to increase the mass of IONP in the hydrogel composites. Figure 34 shows the mass change of the composite as a function of infusion- coprecipitation cycles. The increase in composite mass was found to be almost linear with the number of infusion-coprecipitation cycles. With the approach according to the invention, it was possible to fabricate composites with up to 80 wt% of fillers (IONP). Composites with such high wt% of metal particles are extremely difficult to achieve with prior art methods due to the limitation of metal salt solubility in water. Optical images of the hydrogels throughout different cycles of infusion and coprecipitation process are shown in Figure 35. The volume of composites grew with the number of infusion- coprecipitation cycles. The nanoparticles grown within the 10-cycle polymer composites, as observed from SEM cross-sections of the structure, were determined to be approximately spherical in shape with a size of 22 ^ 6 nm (Figure 36a and 36b). (The particle size is different from that in Example 7 due to the difference in hydrogel composition used.) The hydrogel composites were then soaked in in an aqueous solution containing 2.7M Fe3+and 1.5M Fe2+ions at 65˚C for 1 hour to infuse them with iron ions again. The iron- ion infused composites were dried at different temperatures (room temperature, 4˚C and 65˚C) overnight before thermal treatments. As seen in Figure 37a-c, micro computer tomography (µCT) scans of the dried infused-composites showed that slow drying at room temperature helped to reduce drying-induced cracking. They also indicate that our in-situ synthesis approach enables the fabrication of IONP composites with a homogenous distribution of IONP. The dried infused-composites were then converted into a ceramic using a two-step debinding and sintering process. A tube furnace with multiple gaslines was employed to conduct the thermal treatments. The debinding step (step I) was conducted in nitrogen using the thermal profile outlined in Table 1. The debinded samples were then HT / so 240174WO 04 March 2025 calcined and sintered (step II) in air using the thermal profile outlined in Table 1. Thermogravimetric analysis (TGA) of the dried-infused composites indicated that an overall mass loss of approximately 34% was observed after the debinding and sintering process (Figure 38a for step I and Figure 38b for step II). A mass loss of approximately 40% was observed after debinding, followed by a mass gain of 10% during the calcination step due to oxidation. Table 1: Heating programs of N2 debinding and air sintering process. Step I – N2 (debinding) Temperature [°C] Duration [min] Heating rate [°C / min] 20-200 90 2 200 30 - 200-350 600 0.25 350-1000 325 2 1000 30 - Step II – air (sintering) 20-400 190 2 400-700 300 1 700-1000 150 2 1000 30 - XRD patterns of powders prepared from pulverizing the 3D ceramic structures revealed that the IONP composites were converted into Fe2O3 after the two-step debinding and sintering thermal treatment (Figure 39). The 3D Fe2O3 structures were then heated in forming gas (95% N2 and 5% H2) to reduce them into iron structures. The structures were first heated from room temperature to 1000˚C at a heating rate of 3˚C per minute, followed by an isothermal hold at 1000˚C for 3 hours. XRD patterns of the flattened metal structure revealed that the Fe2O3 structures were successfully reduced into Fe (Figure 40). HT / so 240174WO 04 March 2025 The optical images of the dried 10-cycle infused composite structure, the Fe2O3 structure, and the Fe structure are shown in Figure 41. Compared to printed “blank hydrogels”, the ceramic Fe2O3 structure and the Fe structure exhibited a linear shrinkage of 25% and 38% respectively. µCT was conducted on the Fe structures to assess its quality. As seen in Figure 42, iron structures fabricated using our process was dense. As elucidated in the given examples, the method according to the invention allows the synthesis of a wide variety of composite materials and inorganic materials with various functional and mechanical properties, circumventing the disadvantages inherent in the established methods of the prior art. HT / so 240174WO 04 March 2025

Claims

March 4, 2025 Cl a i m s1. A method for making a composite material, the method comprising the steps of: (a) swelling a blank hydrogel or a blank organogel using an inorganic precursor mixture to form an inorganic precursor-containing solvent- containing gel, wherein the inorganic precursor mixture comprises a solvent, preferably water, and one or more inorganic precursors; and (b) converting the inorganic precursor into ceramic or metal within the solvent-containing gel by introduction of reagents and / or stimuli to obtain a composite material.

2. The method according to claim 1, characterized in that the composite material is thermally treated in an additional step(c) after step (b) to form an inorganic material.

3. The method according to any one of claims 1 or 2, characterized in that steps (a) and (b) are repeated one or more times, each repetition of step (a) preferably comprising using the inorganic precursor mixture containing the solvent and the one or more inorganic precursors or using a different inorganic precursor mixture containing a solvent and a different one or more inorganic precursors.

4. The method according to any one of the preceding claims, characterized in that the reagents and / or stimuli used in step (b) are selected from the group consisting of bases, photolatent bases, reducing agents, hydrolyzing agents, water, ultrasound, radiation, and mixtures and combinations thereof, preferably selected from the group consisting of sodium borohydride, ascorbic acid, sodium hydroxide, ammonia, glucose, hydrazine, trisodium citrate, hydroxylamine hydrochloride, potassium hydroxide, tetrabutylammonium hydroxide, ultrasound, UV light, and mixtures and combinations thereof, particularly- 2 - preferably selected from the group consisting of sodium borohydride, ascorbic acid, sodium hydroxide, ammonia, and mixtures and combinations thereof.

5. The method according to any one of the preceding claims, characterized in that the reagents used in step (b) have a pKb value of from -30 to 30, preferably from -5 to 15, more preferably from -2 to 4, even more preferably from 0 to 2, or from -30 to 30, preferably from -5 to 15, more preferably from 4 to 10, even more preferably from 4 to 6, and / or a standard reduction potential of from -4.1 to +1.5 V vs. SHE, preferably from -4.1 to +0.8 V vs. SHE, more preferably from -2.5 to -0.5 V vs. SHE, even more preferably from -2.0 to -0.5 V vs. SHE or from -4.1 to +1.5 V vs. SHE, preferably from -0.5 to +1.5 V vs. SHE, more preferably from 0.0 to +1.0 V vs. SHE.

6. The method according to any one of the preceding claims, wherein the composite material and / or the inorganic material contains a metal, a metal alloy and / or a ceramic.

7. The method according to any one of claims 2 to 6, characterized in that thermally treating in step (c) comprises debinding, pyrolysis, calcination, sintering, high- temperature annealing, or a combination thereof.

8. The method according to any one of the preceding claims, characterized in that each of the one or more inorganic precursors independently is a nitrate salt, an acetate salt, a chloride salt, a sulfate salt, a bicarbonate salt, an oxynitrate salt, a hydroxide salt, a bromide salt, a fluoride salt, an iodide salt, a chlorate salt, a cyanide salt, a cyanate salt, a thiocyanate salt, a phosphate salt, a dichromate salt, a perchlorate salt, a benzoate salt, a chromate salt, an acetylacetonate, an alkoxide or any combination thereof, preferably a nitrate salt or a chloride salt, most preferably a nitrate salt.

9. The method according to any one of the preceding claims, characterized in that each of the one or more inorganic precursors independently contains one or more elements selected from the group consisting of Fe, Zn, Li, Co, Al, Ni, Mo, La, HT / so 240174WO 04 March 2025- 3 - In, Sn, Ba, Y, Ca, Bi, Sr, Cu, Ti, U, Zr, Mg, Pb, V, Na, K, Sc, Cr, Mn, Ga, Ag, Cd, Hf, W, Au, B, Si, Ge, As, Sb, Te, Se, Ce, P, Be or any combination thereof, preferably selected from the group consisting of Fe, Zn, Co, Ni, Y, Cu, Ag, B, Si, Ce, P, Al, Cr or any combination thereof, most preferably selected from the group consisting of Fe, Ag, Cu, Ni, Al, Cr, Ce, or any combination thereof.

10. The method according to any one of the preceding claims, characterized in that the inorganic precursor mixture comprises at least two different inorganic precursors.

11. The method according to any one of claims 2 to 10, characterized in that the composite material is exposed to a thermal-treatment atmosphere during step (c), wherein the composition of the inorganic material is at least partially determined by the composition of the thermal-treatment atmosphere.

12. The method according to any one of the preceding claims, characterized in that the composite material is exposed to a thermal-treatment atmosphere during step (c), wherein (i) the thermal-treatment atmosphere is a reducing atmosphere and at least a portion of the inorganic material is a metal or metal alloy; or (ii) the thermal-treatment atmosphere is an oxidizing atmosphere and at least a portion of the inorganic material is a ceramic; or (iii) the thermal-treatment atmosphere is an inert atmosphere and at least a portion of the inorganic material is a carbide.

13. The method according to any one of claims 2 to 12, characterized in that step (c) comprises a plurality of thermal treatment steps.

14. The method according to any one of claims 2 to 13, characterized in that a shrinkage of 80% or less, preferably 50% or less, most preferably 30% or less, of the inorganic material occurs during step (c), compared to the composite material. HT / so 240174WO 04 March 2025- 4 - 15. The method according to any one of the preceding claims, characterized in that (i) the blank hydrogel is formed from an aqueous hydrogel precursor mixture using a photopolymerization, wherein the aqueous hydrogel precursor mixture comprises or consists of water and one or more aqueous photosensitive binders, or (ii) the blank organogel is formed from a nonaqueous organogel precursor mixture using a photopolymerization, wherein the nonaqueous organogel precursor mixture comprises or consists of a non-water solvent, preferably a water-miscible non-water solvent, and one or more photosensitive binders, and wherein the blank organogel is optionally further converted to a blank hydrogel by soaking it in water prior to further use.

16. The method according to any one of the preceding claims, characterized in that the blank hydrogel or blank organogel is prepared via an additive manufacturing process.

17. A composite material containing ceramic and / or metal obtainable by the method according to any one of claims 1 to 16 or an inorganic material containing ceramic and / or metal obtainable by the method according to any one of claims 2 to 16.

18. The composite material according to claim 17, characterized in that the composite material has a core-shell structure, the ceramic and / or the metal preferably being present in the shell; or in that the inorganic material has a shell containing the ceramic and / or the metal and is hollow.

19. The composite material or the inorganic material according to claim 18, characterized in that the shell has a thickness of from 0.1 µm to 1000 µm, preferably from 0.5 µm to 500 µm, more preferably from 1 µm to 200 µm. HT / so 240174WO 04 March 2025

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