A METHOD, A SYSTEM AND A PACKAGE FOR PRODUCING AN ELECTRICALLY CONDUCTIVE COMPOSITE

Abstract

Provided is a method for producing an electrically conductive composite, wherein the method includes: a) providing a bed of a polymer in a non-continuous solid form; b) providing, on the polymer bed, a composition that comprises a chemical precursor dissolved in a liquid medium made to inhibit a chemical reaction of the chemical precursor into forming an electrically conductive inorganic component; c) forming an electrically conductive inorganic component from a chemical reaction of the chemical precursor, by at least evaporating the liquid medium; and d) exposing to electromagnetic radiation an electromagnetic radiation absorber of the composition, to sinter those portions of said polymer bed in thermal contact therewith, to form a polymer network that percolates an electrically conductive network formed with the electrically conductive inorganic component.

Also provided are a system and a package adapted to implement the presently disclosed method.

Claims

1. A method for producing an electrically conductive composite, wherein the method comprises: a) providing a bed of a polymer in a non-continuous solid form; b) providing a composition on at least a region of said polymer bed to wet and disperse across at least part of the thickness of the polymer bed, wherein said composition comprises a chemical precursor dissolved in a liquid medium, wherein said liquid medium is made to inhibit a chemical reaction of said chemical precursor into forming an electrically conductive inorganic component, and wherein at least one of said composition, by-products formed therefrom, said chemical precursor, chemical intermediates, and said electrically conductive inorganic component is an electromagnetic radiation absorber; c) forming said electrically conductive inorganic component from a chemical reaction of the chemical precursor, by at least evaporating said liquid medium, wherein said electrically conductive inorganic component forms an at least partially continuous electrically conductive network; and d) exposing to electromagnetic radiation at least said electromagnetic radiation absorber, to photothermally generate heat to sinter at least those portions of said polymer bed in thermal contact therewith, to form an at least partially continuous polymer network, wherein said at least partially continuous electrically conductive network and said at least partially continuous polymer network at least partially percolate each other.

2. A method according to claim 1, wherein said formation of the electrically conductive inorganic component of step c) further comprises heating solid residues formed from the chemical precursor upon said evaporation of the liquid medium, wherein said solid residues contain said electrically conductive inorganic component and non-electrically conductive elements, to at least partially break down said solid residues and remove said non-electrically conductive elements therefrom.

3. A method according to claim 2, wherein at least part of step c) is performed simultaneously to step d), so that at least heat used for said heating of said solid residues is obtained from said photothermal heat generated by the electromagnetic radiation absorber.

4. A method according to claim 3, wherein all of step c) is performed simultaneously to step d), so that also heat used for said evaporation of the liquid medium is obtained from said photothermal heat generated by the electromagnetic radiation absorber.

5. A method according to claim 1, wherein steps c) and d) are performed sequentially, so that said electromagnetic radiation absorber exposed to electromagnetic radiation at step d) is said electrically conductive inorganic component formed at step c).

6. A method according to claim 1, wherein said electrically conductive inorganic component comprises a plurality of inorganic particles, the method further comprising at least one of aggregating, sintering, and annealing said inorganic particles to form said at least partially continuous electrically conductive network, from heat applied at said step c) and/or from said photothermal heat generated by the electromagnetic radiation absorber.

7. A method according to claim 1, wherein said electromagnetic radiation absorber is made to absorb at least two times more strongly said electromagnetic radiation compared to said polymer.

8. A method according to claim 1, wherein said electromagnetic radiation absorber is not optically resonant.

9. A method according to any of claim 1, wherein said electromagnetic radiation absorber is optically resonant to at least a specific wavelength, so that when exposed at step d) to an electromagnetic radiation having said specific wavelength, the electromagnetic radiation absorber optically resonates to heat up.

10. A method according to claim 1, wherein said chemical precursor is in form of solvated individual metal atoms or ions or/and in form of molecular metallic complexes.

11. A method according to claim 1, wherein the composition is deposited on at least said region of the polymer bed by droplet deposition.

12. A method according to claim 1, wherein the electromagnetic radiation to which at least said electromagnetic radiation absorber is exposed in step d) is selected to be of a wavelength range from 250 nm to 4000 nm, preferably from 350 nm to 2000 nm.

13. A method according to claim 1, wherein said percolated polymer and electrically conductive networks form a base layer of the composite, the method comprising producing a three-dimensional object using a layer-by-layer deposition process, by repeating a step a) of providing at least a further bed of a polymer in a non-continuous solid form over said base composite layer, and repeating steps b), c) and d) with respect to said further polymer bed.

14. A system for producing an electrically conductive composite, wherein the system comprises: at least one supplier device configured and arranged for providing: a polymer bed in a non-continuous solid form; and a composition on at least a region of said polymer bed to wet and disperse across at least part of the thickness of the polymer bed, wherein said composition comprises a chemical precursor dissolved in a liquid medium, wherein said liquid medium is made to inhibit a chemical reaction of said chemical precursor into forming an electrically conductive inorganic component, and wherein at least one of said composition, by-products formed therefrom, said chemical precursor, chemical intermediates, and said electrically conductive inorganic component is an electromagnetic radiation absorber; a supply of polymer in a non-continuous solid form and a supply of said composition, to feed said at least one supplier; an evaporating mechanism configured and arranged for evaporating said liquid medium, to at least collaborate in forming said electrically conductive inorganic component from a chemical reaction of the chemical precursor, to form an at least partially continuous electrically conductive network with said electrically conductive inorganic component; a controllable electromagnetic radiation source configured and arranged for exposing at least said electromagnetic radiation absorber to electromagnetic radiation, in order to photothermally generate heat to sinter at least those portions of said polymer bed in thermal contact therewith, to form an at least partially continuous polymer network, wherein said at least partially continuous electrically conductive network and said at least partially continuous polymer network at least partially percolate each other; and at least one controller adapted to control said at least one supplier device to provide said polymer bed and said composition, and said controllable radiation source to emit said electromagnetic radiation to expose the electromagnetic radiation absorber.

15. A package for producing an electrically conductive composite, wherein the package comprises, enclosed therein, a composition that comprises a chemical precursor dissolved in a liquid medium, wherein said liquid medium is made to inhibit a chemical reaction of said chemical precursor into forming an electrically conductive inorganic component, wherein at least one of said composition, by-products formed therefrom, said chemical precursor, chemical intermediates, and said electrically conductive inorganic component is an electromagnetic radiation absorber, and wherein the package is configured and arranged to cooperate with at least one supplier device of a system for producing an electrically conductive composite, for providing said composition by extracting the same from the package, wherein said system comprises: said at least one supplier device configured and arranged for providing: a polymer bed in a non-continuous solid form; and said composition on at least a region of said polymer bed to wet and disperse across at least part of the thickness of the polymer bed; a supply of polymer in a non-continuous solid form and a supply of said composition, to feed said at least one supplier; an evaporating mechanism configured and arranged for evaporating said liquid medium, to at least collaborate in forming said electrically conductive inorganic component from a chemical reaction of the chemical precursor, to form an at least partially continuous electrically conductive network with said electrically conductive inorganic component; a controllable electromagnetic radiation source configured and arranged for exposing at least said electromagnetic radiation absorber to electromagnetic radiation, in order to photothermally generate heat to sinter at least those portions of said polymer bed in thermal contact therewith, to form an at least partially continuous polymer network, wherein said at least partially continuous electrically conductive network and said at least partially continuous polymer network at least partially percolate each other; and at least one controller adapted to control said at least one supplier device to provide said polymer bed and said composition, and said controllable radiation source to emit said electromagnetic radiation to expose the electromagnetic radiation absorber.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0093] In the following some preferred embodiments of the invention will be described with reference to the enclosed figures. They are provided only for illustration purposes without however limiting the scope of the invention.

[0094] FIG. 1 depicts a schematic and simplified view of the steps of the method of the first aspect of the present invention, for an embodiment.

[0095] FIGS. 2a to 2e schematically shows also the steps of the method of the first aspect of the invention, but for a more detailed embodiment than that of FIG. 1.

[0096] FIG. 3 shows a graph of the electrical resistance (Ohm) measured versus the length across a printed PA12-Ag composite stripe of 5 mm width according to Example 1 described below.

[0097] FIG. 4 schematically shows the system and package of the second and third aspects of the present invention, for an embodiment.

DETAILED DESCRIPTION OF THE INVENTION

[0098] Hereinafter, some embodiments associated to different modes for carrying out the present invention are described in detail.

[0099] A new method for printing/obtaining electrically conductive two-dimensional (2D) or three-dimensional (3D) objects is provided, which can be used as stand-alone conductors of electricity or as electrical components of more complex 2D and 3D objects. The obtained electrically conductive objects are composites made of plastic and inorganic materials, and the composites and final objects carry some beneficial properties from both parts of the composite, namely: they are flexible and robust like the polymer and they also are electrically conductive like the inorganic material. Compared to previous methods for printing similar objects, the invention method is simpler and can be used for 2D and 3D printing of electrically conductive objects. In addition, the claimed method is easy to integrate with complementary processes for 2D and 3D printing of various other materials.

[0100] Moreover, the method according to the first aspect of the present invention can be applied for the fabrication and production of consumer electronics, electrical appliances and electrical and electronic components of such devices and systems.

[0101] The method can be summarized as follows, for an embodiment: a precursor ink composition, which contains metal atoms and/or molecular organometallic complexes dissolved in a liquid medium/solvent, is deposited on and diffuses throughout a bed of powder polymer, which thus form a mixture. Electromagnetic irradiation is then applied to the powder-ink mixture, which is preferentially absorbed by one or more of the components of the ink composition, or any of its products, intermediates and by-products, and results to formation of electrically conductive inorganic particles, sintering of the polymer, and optionally sintering of the particles, and then the formation of a polymer/inorganic particle network which is electrically conductive. It is emphasized that the absorption of the electromagnetic radiation and generation of heat by the polymer are negligible. The method steps can be repeated several times in the context of 2D and 3D printing of electrically conductive objects. This method can further be combined with other 2D and 3D printing technologies.

[0102] More detailed, the printing method starts with the deposition of a thin polymer powder bed on a surface and is followed by the deposition of the ink composition on top of a thin layer of the polymer powder as shown in FIG. 1 (first image), where the ink composition has been identified with reference C and the polymer powder particles with reference P. The ink composition is preferentially being deposited in the form of droplets. The powder polymer layer, once deposited on the surface, is a non-continuous solid and consequently its morphology is not preserved when a significant mechanical stress is applied to it since the powder polymer particles in the layer are not bounded and attached to each other at this step of the method. When the ink composition is deposited onto the powder polymer layer, the former wets the latter and disperses across part of the upper surface of the powder layer as well as throughout the cross section on the powder polymer layer. The volume and geometrical characteristics of the part of the powder polymer layer that is wet by the ink composition, such as the shape and the total upper surface area of the wet area, and the thickness of the cross section that is wet, depends on the volume of the ink being deposited. The latter further depends on the number and size of the droplets and the volume of each individual droplet. In addition, the volume of the powder polymer layer that is wet by the ink composition and its geometrical characteristics, such as its shape and the total surface area, also depends on the viscosity of the ink and its wetting and chemical affinity to the surface of the polymer particles. The method works when the ink composition does wet the surface of the polymer powder particles. Preferably, the ink composition has to disperse across the entire thickness of the powder polymer layer. Therefore, all of the aforementioned parameters are engineered as to achieve the desired wetting behavior.

[0103] The ink composition in its original form, and until it is deposited on the powder polymer layer, contains atomic and molecular species which can act as precursors for the subsequent formation of inorganic and electrically conductive solids. These atomic and molecular species may be metal atoms, metal salts and organometallic complexes dissolved in a liquid solvent or mixture of liquid solvents capable of inhibiting the reaction of the precursors into forming inorganic conductive particulates or large conductive solids. This is an important difference compared to any other printing methods which rely on the deposition of preformed inorganic conductive particles such as a silver ink containing silver flakes.

[0104] After the removal of the liquid medium/solvent, which, for an embodiment, starts to happen after the deposition of the ink composition due to slow or fast evaporation depending on the temperature of the system, the precursors may or may not react at room temperature to form metallic inorganic particles. Therefore, as further shown in FIG. 1 (second image) and indicated by reference HEv, after the deposition of the ink composition, the powder-ink mixture can be optionally heated to accelerate the evaporation of the ink composition's liquid medium/solvent and that may further result to formation of metallic inorganic particles, such as silver if the ink contains silver atoms, dispersed throughout the powder polymer layer. Those inorganic particles are schematically shown in the second image of FIG. 1 and identified with reference M. Nevertheless, it must be noted that generally the temperature at which the mixture may be heated in this step, is not sufficiently high to result to sintering of the particles of powder polymer. Therefore, up to this step, the printing method is not complete, and the composite is not still finished.

[0105] The method is completed, for an embodiment, by irradiating the ink-polymer composite with electromagnetic radiation, as indicated with reference R in FIG. 1, which is absorbed by the ink composition or any of its products, intermediates and by-products which could have been formed up until the radiation is applied. The wavelength and intensity of the electromagnetic irradiation is chosen as to preferentially or completely be absorbed by one or more component of the deposited ink composition, or any of its products, chemical intermediates, such as solid residues that are left after the ink composition's liquid medium/solvents are evaporated, and by-products, such as any metallic inorganic particles formed after the ink composition has been deposited. Upon absorbing the electromagnetic radiation, the ink composition, its solid residue, products (inorganic particles), intermediates, and/or any of its by-products are heated, via a photo-thermal effect, to a temperature which coincides or exceeds the sintering temperature and/or melting temperature and/or glass transition temperature of the particles of powder polymer. This induces sintering of the polymer particles, meaning that they become interconnected forming a polymer network identified in FIG. 1 with reference PN.

[0106] The aforementioned photo-thermal effect also results to reaction of the precursors of the ink composition into forming inorganic electrically conductive solids or solid particulates which form an at least partially continuous inorganic network, identified in FIG. 1 with reference MN, that is dispersed throughout the sintered polymer particles. In fact, the photo-thermal effect may also result to sintering, aggregating and/or annealing of any inorganic particulates that may have been formed prior to or during the application of the electromagnetic irradiation. This results to an increase of the electrical conductivity of the inorganic network. In addition, the photo-thermal effect may result to evaporation of any unreacted by-products of the ink composition or of any remaining organic contents of the ink composition, and this further improves the conductivity and elemental purity of the inorganic network. The intensity of the applied radiation and duration of the irradiation process are adjusted as to maximize the aforementioned effects related to sintering of the polymer particles, and, optionally, to sintering, aggregating and/or annealing of the inorganic solids. When the electromagnetic irradiation stops, the system cools down and the composite is complete. In its final form the composite consists of two inter-percolated networks: an at least partially continuous polymer network and an at least partially continuous inorganic and electrically conductive network. The overall composite is both flexible and mechanically robust which are qualities similar to the ones of the polymer network, and electrically conductive which is a quality similar to the one of the inorganic network.

[0107] A graphical representation of the steps of the method of the first aspect of the invention, for a more elaborated and realistic embodiment than that of FIG. 1 is shown in FIGS. 2a to 2e, and is described below.

[0108] Starting by FIG. 2a, there step a) of the method of the inventions is illustrated, where a polymer powder P is deposited or otherwise prepared, whether at room temperature or at higher temperatures. Any temperature beneath the sintering temperature of the polymer powder is valid.

[0109] Step b) is depicted in FIG. 2b, where an ink composition C containing metal complexes is deposited onto the polymer powder P. The ink composition C is designed to wet and coat the polymer powder P. No chemical change has occurred yet.

[0110] FIG. 2c shows a situation which, for the illustrated embodiment, corresponds to part of step c), as although the evaporation of the liquid medium/solvent occurs, the electrically conductive inorganic component is not yet fully formed. Particularly, FIG. 2c shows how once the ink composition has been evaporated, some (or all) of the metal complexes may decompose to form metal nanoparticles NP for some types of precursor, and some (or all) of them form a solid residue CR of the complex (could be organic or inorganic). Said nanoparticles NP and complex solid residue CR for a solid residue SR that may include other impurities. The network of metal nanoparticles NP (if they have formed here) is not continuous, and contains much non-metallic components. This reduces conductivity, so once all the liquid medium/solvent of the ink composition is evaporated further heat is required to remove the non-metal residue.

[0111] FIGS. 2d and 2e show the rest of steps of the method of the first aspect of the invention, for the illustrated embodiment, and can be performed simultaneously or sequentially (in the order illustrated).

[0112] FIG. 2d shows part of step c), specifically how the metal complexes break down via the above mentioned further heating. That further heating could be due to the temperatures of the polymer powder (often >150° C. for 3D printing) or from photothermal heat coming from incident light, which is absorbed by the solid residues SR. Due to the further heating the solid residue SR is broken down and the non-metal element is removed, leaving only metal nanoparticles NP. These metal nanoparticles NP may aggregate or anneal to form a more continuous network.

[0113] At FIG. 2e, step d) has been applied, i.e. the sample (the composite being formed) is exposed to electromagnetic radiation, generally light, that is absorbed by the metal/solid residue (could be either or both at this stage, depending mainly if the step of FIG. 2e is performed after or simultaneously to that of FIG. 2d), which according to a photothermal effect heats up and transfers heat to the polymer powder P. Heat is enough to melt polymer powder P, which sinters to form an at least partially continuous network PN. Heat may also further sinter or anneal the metal particles NP together, forming or improving an already formed, if so, metal network MN.

[0114] Hence, a composite is produced that includes an electrically conductive metal-polymer interjoined network, formed by a metal network MN percolated with a polymer network PN.

[0115] As stated above, to improve conductivity, more ink composition C may be added to the polymer powder P, and to create a 3D object all steps can be repeated the desired number of times.

[0116] The morphology of the final composite will depend on the morphology of the initial powder bed, the volume and deposition area of the ink composition, and the morphological changes that will be induced by the sintering process. Generally, the planar morphology of the initial powder polymer bed/layer is preserved and translated to a planar morphology of the final conductive composite. The dimensions and shape of the final sintered composite depend on the shape and dimensions of the powder polymer area which was wet by the ink composition. Therefore, by wetting, with the ink composition, the powder polymer bed across an area of a simple or complex shape, such a square, or a circle, or a stripe or any more complex two dimensional pattern, the method according to the first aspect of the invention can result to the ultimate formation of a composite pattern.

[0117] Since the sintering process happens only across the area and volume which is wet by the ink composition and irradiated by electromagnetic radiation, the final sintered object, which is a solid and continuous object, can be removed from or cleaned from the surrounding materials which were not wet by the ink composition and/or were not irradiated by the external electromagnetic irradiation. That allows for at least two variations of 2D printing using the method of the invention: one where the printed pattern is determined by the pattern of the irradiated layer, and one where the printed pattern is determined by the deposition pattern of the ink composition. A combination of these two variations is also possible.

[0118] If the conductivity of the printed object is not high enough, e.g. due to insufficient amount of ink composition being mixed with the powder polymer as to fill all the free volume within the polymer layer, then more ink composition can be deposited after the first deposition and before or after the irradiation of the ink-polymer mixture/composite, as to transform it into a solid composite, that is a 3D composite. In such case, the composite can be irradiated with electromagnetic radiation more than one times, e.g. every time after deposition of the ink composition. This process can be repeated several times. 3D printing of conductive objects, or of conductive parts of more complex objects, can be made through repetition of the method steps a) to d), meaning that after a conductive composite has been formed, that is steps a) to d) have been carried out, then, a new powder polymer layer can be deposited on top, ink composition is then deposited on this new or second powder polymer layer, the ink-polymer mixture/composite can be optionally heated, and then it is irradiated with electromagnetic irradiation. This process can be repeated several times in the context of the additive manufacturing which is a well know concept in the prior art.

[0119] The method according to the first aspect of the present invention and any obvious variations of it can be combined, in a successive manner, with other additive manufacturing methods for making complex objects that contain, only partially, electrically conductive components which are made with the method of the present invention. The electrically conductive objects produced/printed via the method of the first aspect of the present invention can be selectively detached from the surfaces on which they are attached to during and after printing, so as to become free standing objects.

[0120] On the other side, an electrically conductive produced/object printed according to the present invention can be prepared as illustrated below in its preparation example in Example 1.

EXAMPLES

[0121] Hereinafter, the present invention is described in more detail and specifically with reference to the Examples and Figures, which however are not intended to limit the present invention.

Example 1

[0122] In a specific example, the ink-composition is a metal-precursor molecular ink composition that has been previously prepared using the method described in J. Am. Chem. Soc., 2012, 134 (3), pp 1419-1421, which main parts are below reproduced.

[0123] 1 g of silver acetate was dissolved in 2.5 ml of aqueous ammonium hydroxide. Then, 0.2 ml of forming acid was added drop wise under stirring. Subsequently, the solution was centrifuged and, then, filtered through a 200 nm pore size filter. The filtered solution was clear. Then, this metallic molecular ink was deposited in nylon polymer powder for making the ink-polymer composite. While the ink is suitable to be used for making conductive patterns on continuous solid substrates, it could not be readily used for the purpose of the present invention because it does not wet the powder particles, which are very hydrophobic. For this purpose, this ink was further mixed with 2 ml of ethanol. Due to this modification, the ink did wet the powder bed, meaning that it was able to deposit a droplet of the ink on a layer of powder PA12 nylon, and the droplet dispersed and got absorbed by the powder PA12 nylon layer.

[0124] Then, the ink-PA12 nylon composite was irradiated with 800 nm IR light coming from LED array. This wavelength is absorbed by the deposited ink but not by the powder PA12 nylon itself. The light causes the ink to heat resulting to its transformation to metallic silver and in this example the temperature was actually increased to >180° C. causing also sintering of the powder PA12 nylon polymer. As result, a solid polymer-silver composite was formed at the region where ink was deposited. The polymer layer region where ink had not been deposited did not get sintered despite being also illuminated by the LED array. After the formation of the composite, the IR light source was switched off, and the sample was left to cool down. Then, the composite could easily be removed by hand from the not sintered part of the powder layer.

Example 2

[0125] In this example, the metal-precursor molecular ink composition prepared in Example 1 was deposited across a rectangular region looking like a stripe, and the final composite had this stripe-like shape. The strip had good mechanical properties, meaning, that it could be handled by hand and be mechanically stretched and bended without breaking apart or being damaged. This stripe was conductive as shown in FIG. 3. The electrical resistivity of the stripe, which as made had an electrical resistance of 13.4 ohms, did not change significantly when the stripe was bended, in the latter case the electrical resistance was 13.9 ohms.

Example 3

[0126] This example differs from example 1 in that the metal-precursor molecular ink composition was applied across the entire surface area of the polymer powder layer. Then, using a scanning laser beam, wavelength 800 nm, a composite-pattern of zig-zag shape was sintered.

Example 4

[0127] This example differs from example 1 in that the metal-precursor molecular ink composition was deposited using an inkjet commercial printer, making a zigzag-shaped pattern on part of the surface of the polymer powder layer. Then, the entire powder polymer layer was illuminated with IR light using a LED array, and the zigzag-shaped pattern of the powder was transformed into a sintered composite pattern of same size and dimensions, which further appeared to exhibit metallic colour due to the metallization of the ink.

Example 5

[0128] In another example, the electrically conductive inorganic network consists of copper which as an element is much more abundant in earth's crust and, thus, has lower financial cost compared to silver. An example of metal-precursor molecular ink composition suitable for printing copper-based composites with the method according to the present invention can be found in the literature, for example, in Advanced Materials Interfaces, 2015, 2, 1400448, and similarly made as follows: copper formate was partially or completely dissolved or dispersed in a solvent. A non-limited list of suitable solvents are water, dipropylene glycol, monoethylether and mixtures thereof. The prepared metal-precursor molecular ink compositions were subsequently deposited on a layer of powder polymer and be transformed to copper once the temperature of the polymer powder-ink mixture approaches or reaches or exceeds a temperature of 180° C. The printing method may be carried out under ambient environmental conditions or under a chemically inert atmosphere such under nitrogen or argon gas.

[0129] As described above in detail, the method according to the first aspect of the present invention has the following advantages: [0130] The 2D and 3D printing of electrically conductive composites comprising polymer and metal (or another type of inorganic material) retain the beneficial mechanical properties of polymers, specifically they are flexible and robust under external mechanical stress and the electrical conductivity of metal (or of another type of inorganic material). This allows for creating flexible and robust objects that are electrically conductive. Such objects can be used as stand-alone conductors of electricity or as respective components in electrical and electronic devices; [0131] The method of the invention does not require pre-formation of conductive inorganic particles, which in itself is tedious task since the morphology of these particles often needs to be engineered into forming complex shapes such as high aspect ratio rods and wires; [0132] The method of the invention has the advantage of being simpler compared to other ones which rely on the separate formation of a plastic continuous layer and the subsequent deposition of second metallic (electrically conductive) layer on top of the plastic layer; [0133] The two networks are formed substantially at the same time (as explained above, depending on the embodiment, steps c) and d) can be carried out at least in part simultaneously and/or at least in part sequentially) and, at least partially, percolate each other; [0134] The method of the invention avoids the potential problem of delamination and detachment of the polymer and metallic part of the composite; [0135] The method of the invention is simpler because the electrically conductive material is formed into the sintered polymer, compared to other methods which rely on the separate fabrication of metallic and polymeric components, or in general electrically conductive materials such as nano- and micro-particles, and then mixing of these materials with the polymer; [0136] The method of the invention allows for printing electrically conductive 2D and 3D objects, which can be used as standalone objects or as ones that are embedded within other printed complex objects; [0137] The method of the invention can be used in combination with other methods and instruments for 2D and 3D printing objects, and allows for creating our conductive objects directly inside other complex objects and while the latter are being created.

[0138] Finally, a schematic representation of the system and package of the second and third aspects of the present invention is shown in FIG. 4.

[0139] Specifically, for the illustrated embodiment, a package Ct is shown which comprises, enclosed therein, a supply of composition C that comprises a chemical precursor dissolved in a liquid medium, wherein said liquid medium is made to inhibit a chemical reaction of said chemical precursor into forming an electrically conductive inorganic component, wherein at least one of said composition C, by-products formed therefrom, said chemical precursor, chemical intermediates, and said electrically conductive inorganic component is an electromagnetic radiation absorber.

[0140] Package Pa is configured and arranged to cooperate with at least one supplier device of the system for producing an electrically conductive composite.

[0141] The system of the second aspect of the present invention comprises, for the embodiment illustrated by FIG. 4: [0142] a common supplier device Sp which is coupled to the package Pa to receive a supply of the composition C, and to a further package/container Ps to receive a supply of polymer P; wherein the common supplier Sp is configured and arranged for providing, through respective nozzles Pn, Cn: [0143] a polymer P bed in a non-continuous solid form; and [0144] the composition C on at least a region of the polymer bed to wet and disperse across at least part of the thickness of the polymer bed; [0145] a controllable electromagnetic radiation source F configured and arranged for exposing the electromagnetic radiation absorber to electromagnetic radiation R, in order to photothermally generate heat to sinter at least those portions of said polymer P bed in thermal contact therewith, to form an at least partially continuous polymer network, wherein the at least partially continuous electrically conductive network and the at least partially continuous polymer network at least partially percolate each other; and [0146] a controller U adapted to control the common supplier device Sp to provide the polymer P bed and the composition C through the respective nozzles Pn, Cn, and the controllable radiation source F to emit the electromagnetic radiation R to expose the electromagnetic radiation absorber.

[0147] For the embodiment illustrated in FIG. 4, the evaporating mechanism of the system is implemented by the controllable radiation source F, where heat obtained from the photothermal heat generated by the electromagnetic radiation absorber is used for evaporating the liquid medium of the composition C, to collaborate in forming the electrically conductive inorganic component from a chemical reaction of the chemical precursor, to form an at least partially continuous electrically conductive network MN with the electrically conductive inorganic component, as explained above with reference to FIGS. 1 and 2.

[0148] It is a matter of course that the features mentioned above can be used in other combinations in addition to those described, on in isolation, without departing from the scope of the invention as it is defined in the attached claims.