A method and system for producing a printable object

Abstract

Disclosed is a method for printing a 3D printable object, for example for a biomedical purpose, the method comprising: causing an injection tip (120) of a printing element comprised in a printing device to move at least horizontally within supporting material (115) such that the injection tip forms a cavern in to the supporting material, wherein the supporting material is complex fluid that has semi-solid gel-consistency and the cavern corresponds to the shape of the 3D printable object, injecting, using the injection tip, printing material (110) into the cavern, wherein the printing material comprises biodegradable or biostable resin or resin composite, and allowing a flow of the supporting material to cover the printing material after the movement of the injection tip.

Description

2023436301   14 Sep 2026 used as printable material called bioink in AM technologies. Hydrogel's consistency and viscosity can be controlled by temperature. In some hydrogels the viscosity increases by increasing the temperature in some other it is opposite. Hydrogels have low mechanical strength and thus may not be suitable to be used as load-bearing implant but can be used 5 as scaffold in tissue engineering where high strength is not needed. However, hydrogels can be cross-linked for retaining its shape. There are several 3D printing techniques, devices and resins available which are used to fabricate tissue engineering scaffolds, implants, implantable or per os delivered drug 10 releasing dossiers, dental constructs and even living cell constructs. 3D printing can be used also in tumor cell invasion scaffold fabrication which are used in cancer drug development and testing. An example of fabrication of biostable device is the use thermoset monomer system in implants and dental restorations. Printed material is mono or multifunctional acrylate or methacrylate monomer system or filler comprising resin 15 composite. On the other hand, biodegradable resin-based materials may be preferred for tissue engineering scaffolds and drug releasing dossiers. Monomers harden in polymerization by free radical polymerization, cationic polymerization, cationic photopolymerization or frontal polymerization which are reactions inhibited e.g. by oxygen, which can be understood as ambient oxygen. For having complete hardening, 20 i.e. degree of cure called monomer conversion (DC) of the monomers from inner part to the surface, oxygen should not be present in the curing process. Negative effect of ambient oxygen may be hindered for example by using oxygen protective barrier before final curing of the object is performed. One oxygen protective barrier in AM techniques is the supporting material which can comprise diffused gas or gas bubbles of 25 polymerization protection gas. Ideally the protection gas should be evenly distributed to the supporting material and retain the gas in the supporting material throughout the period of the printing process. This can be obtained by the tailoring the consistency and viscosity of the supporting material for not allowing gas to escape too fast from the material. By too fast it is meant the time of the printing process which can vary from 30 few seconds to several days for example. 2023436301   14 Sep 2026 Key issue in all 3D printing processes is support of the printing object for initial fixation of the printable material to the supporting platform and during printing the material layer-by-layer. In fabrication of 3D printed objects with diversity of shapes the critical overhangs, in some examples, cannot be balanced by the main body of the printable 5 object and consequently, the printing material collapses due to gravity. One attempt to overcome this problem is to multichannel plotting of temporary supporting material together with the main printing material. The system is called a polyjet printing system. As an example, in the polyjet 3D printing a separate supporting material can be printed simultaneously with the printing material. Supporting material will then be an integrated 10 part of the printable object and needs to be removed afterwards. After removal the polyjet supporting material, the printed object has a sticky polymerization inhibited, non-gloss and not biocompatible surface due to the printing process which has occurred in ambient air. 15 An alternative method for printing is to inject the material in the non-solid supporting material. The supporting material may be fluid, complex fluid, colloid, gel or semi-solid material. A system using this method can be used for example to deposit and cross-link bioink of mixture of cells, supporting matrix, nutrients to create tissue-like constructs. The bioink for example may be printed into gel poloxamer, which is poly(ethylene 20 oxide)-poly(propylene oxide)-poly(ethylene oxide) triblock copolymer (PEO-PPO-PEO) biocompatible gel supporting the printing bioink. When the poloxamer gel and other gels are used as supporting material for 3D printing with printing material that is of thermoset monomers or composites with the robocasting technique, the gel may however contaminate the surface of printing layers and the printing layers may therefore 25 not adhere to each other via polymerization, which may cause a weak construct of the printable object. In addition, movement of a printing tip of in the supporting gel may cause turbulent flow and unsteady vortices which are causing inaccuracy to the printing objects which is formed from the printing material. Fluid dynamics in the supporting liquids may also cause movement of the supporting material itself which deforms the 30 printed object by stretching. 2023436301   14 Sep 2026 Thus, it would be beneficial to have a system and / or method, that may be at least partly controlled using a computing device, to produce printable objects that have the planned form and dimensions by printing material in extrusion injection technique. Printing the material to the supporting material which have consistency and viscosity at room 5 temperature and pressure (RTP), physiological temperature, or at the temperature suitable for the printing material to be processed and which allows the injection tip of the printing device to move freely, to support the printing material against gravity and lateral spreading and to eliminate influence of oxygen inhibition of free radical polymerization on the surface of printable material is desired. 10 In an exemplary embodiment of a desired supporting material system, the supporting gel-consistency material allows tip of the printing tip to form a cavern to the supporting material when the tip moves horizontally. Force required to form the cavern should be such low that the tip of the injection head is not deformed. Thus, the shear 15 stress to cut the supporting material and to form the cavern should be lower than stress to deform the injection tip. Figure 1 illustrates an exemplary embodiment of such a system that is configured to implement a method for producing a printable object using 3D printing. In this 20 example embodiment, the system comprises a printing device that may comprise or be connected to a computing device that may be caused to execute computer instructions such that the printing of the printable object is controlled at least partly by the computing device. Further, the printing device comprises one or more printing heads, each comprising an injection tip. In the figure 1, one injection tip is illustrated. The 25 system in this example embodiment comprises a conical cylinder shaped injection tip 120 of the printing device which moves horizontally in the direction of arrows and cuts a cavern to the supporting material 115 into which the printing material 110 is injected using the injection tip. This is illustrated in the scenario 100 of the figure 1. Figure 1 also illustrates in the scenario 105 the event behind the horizontally moving injection 30 tip after a time period of approximately 0.5 to 60 seconds when the supporting material 115 flows from the walls of the cavern (side arrows) and covers the printable material 110 protecting the material from effects of oxygen inhibition of the ambient air. 2023436301   14 Sep 2026 Gradually the cavern is fully filled due to locally induced thixotropy of the supporting material by the moving injection tip (vertical arrows). The printing material 110 may be biodegradable or biostable resin or resin composite 5 of one of several functional reactive groups comprising polymerizable monomer or comonomer system with compounds allowing addition or condensation polymerization: free radical polymerization, ionic polymerization, ring opening polymerization or frontal polymerization of the resin or resin composite. After polymerization the resin can be either thermoplastic, thermoset, copolymer, blend or interpenetrating polymer 10 network (IPN) of any kinds. The printing material may also be a cross-linkable hydrogel or elastomer. It is also to be noted that the printing material may additionally comprise additional substances or materials. The supporting material 115 is, in this example embodiment, complex fluid gel-15 consistency liquid which supports the printing material 110 against gravity, lateral spreading, protects the printable material's polymerization from oxygen inhibition, keeps the intentionally applied gas (protecting gas for free radical polymerization of the printable resin or oxygen for living cells of the printable bioink) evenly distributed in the supporting material during the printing event and in the case of photoinduced 20 polymerization scatters the polymerization light to be not directly focused to the region of the injection tip which lowers risk for clogging of the injection tip. The supporting material 115 is, in this example embodiment, gel-consistency material of any kind like hydrogel of ethyl or methyl cellulose (MC) (C6H7O2(OH)x(OCH3)y) 25 or carboxymethyl cellulose in concentration of 0.5 to 50.0 wt-% in water, being preferably 5 wt-% . Biocompatible MC of homopolymer comprising glucose units by beta-1,4 bonds and methyl substitution degree of 1.6-1.8 making the MC soluble in water at RTP. Thus, MC is water soluble, and it is used as binder or thickener in pharmaceutical and food applications. MC is cellulose ester such as 30 hydroxypropylmethylcellulose, hydroxyethylcellulose and carboxymeyhylcellulose. Due to its viscosity properties and biocompatibility (Inactive Igredients Search for Approved Drug Products / FDA) MC hydrogel is used as bioink in extrusion based 2023436301   14 Sep 2026 printing. When heated MC gels in water and it is of thermoreversible nature. However, MC hydrogel is not a gel at RTP or physiologic temperature (37oC) which would be desired for bioprinting and 3D printing of free radical polymerizable resins and resin composites, or thermoplastics which need to be cooled and solidified by the 5 low temperature supporting material gel. At RTP MC hydrogel has not a gel viscosity and shows only limited capacity to support the printing material 110 against gravity and lateral spreading and also turbulent fluid flow by force by the movement of the injection tip 125 cause 10 dimensional inaccuracies to printable object. To avoid aforementioned problems the consistency of the supporting material 115 like MC-hydrogel can be adjusted by addition of molecules or colloidal particle systems. One suitable consistency modifier is disaccharide of glucose and fructose (sucrose) or difructose anhydride (caramel), lactose, maltose, galactose or liquid sugar which in the concentration of 0.5 - 99% 15 which change the consistency of hydrogel to be more jelly-like but enables movement of the injection tip 125 in the material and shear force cutting a cavern to the material. When addition of sugar to the MC hydrogel at RTP is used, it is intended to support MC's polymer chains to interact and form intermolecular association of the MC's alkyl 20 group of methyl groups of the polymer chains which is spontaneously taking place at the temperature of above 42.5 oC. Figure 2 illustrates intermolecular association 200 of MC with degree of methyl substitution (DS) of 1.7-2.0 making the MC water soluble and to have polymer chains enabling to form high viscosity gel at RTP. Gelation of MC in water at RTP takes place when the dissolution of sucrose in water and MC 25   hydrogel mixing with water are done simultaneously. Hydroxymethyl groups 210 of the dissolved sucrose form weak chemical interaction with the methyl group 220 of the MC polymers and the water molecules 230 are entrapped to intermolecular structure of MC polymer chains 240. Consequently, the formed environmental and biocompatible MC-sucrose hydrogel is having gel viscosity to be used in applications where such 30 viscosity is needed at room's or physiologic temperatures. 2023436301   14 Sep 2026 In the application of supporting material for 3D printing, the cavern should be closed for protecting the printable material from the effects of ambient gas like air. In the MC-hydrogel a suitable quantity of sucrose for obtaining the aforementioned properties is 80 wt%. Figure 3 illustrates a graph 300 regarding the effect of increasing 5 the sucrose content of MC hydrogel to time of spontaneous closing of the cavern at RTP. 80 wt% sucrose content of the MC hydrogel supports the printing material of dimethacrylate resin composite against gravity and lateral spreading. Sucrose disaccharide molecule (C12H22O11) with its dimeter of ca. 20 angtsrom (2 nm) 10 crystallize to some extend in MC-hydrogel and reaches the size of colloidal particles where sucrose nanoparticles especially at lower temperatures starts to scatter the light (Tyndals effect) which is used in photopolymerization and cross-linking the printable material with a typical light wave length of 465 nm. Light scattering hinders direct light to be focused to the region of the injection tip, lowers local light intensity and 15 power and thus hinders clogging of the injection tip to occur during photopolymerization of the injecting material. Thus, a printing system such as described above may utilize light scattering. Figure 4 illustrates a graph 400 regarding an amount of printing material of particulate filling resin composite which can be injected to MC-hydrogel with and without 80 wt-% sucrose addition before clogging 20 of the injection tip occurs in the set up where 465 nm LED curing light device radiation (ca. 900 mW / mm2) from 30 mm distance in an erlenmeyer glass is directed to the injection tip. If the MC-hydrogel, which is in this example the supporting material, with sucrose ccomprises also micro gas bubbles of protection gas like nitrogen or argon the light scattering is enhanced. 25 MC hydrogel supporting material with sucrose as viscosity modifier at low temperatures (RTP) allows thermoplastic polymers after melting to be printed to the supporting material. Figure 5 illustrates a modification of the printing system described in the example embodiment of figure 1. In this example embodiment, there is the 30 printing material 510 and supporting material 515, which in this example embodiment is temperature controlled. The printing material 510 has direction 535 and is thermoplastic and heated printing material which is to be solidified in a low 2023436301   14 Sep 2026 temperature of the supporting material. In this example embodiment, there is also a thermoelement 540 that keeps the supporting material cool and sucrose provide jelly consistency. In this example embodiment, printing of the printing material 510, which is polycaprolactone (PCL), is performed by the system after being melted at the 5   temperature of 60oC in the injection tip, and the printing material 510 is then injected to the supporting material 515 which has the supporting jelly-like viscosity at temperature of 20oC. When the melted printing material 510 reaches the lower temperature supporting material 515, solidification takes place and the printed object receives the intended shape and dimensions. The direction of the movement of the 10 injection tip is illustrated by the arrows 525 and the support by the supporting material 515 is illustrated using the arrows 545. MC hydrogel with sucrose additive and physiological oxygen (O2) partial pressure may be used as tissue engineering medium. Oxygen partial pressure (headspace O2) level is 15 ca. 18%. Figure 6 illustrates another variation of the printing system / method of the example embodiment illustrated in figure 1. In this example embodiment, the supporting material 615 is MC-sucrose supporting material, which acts as cell and tissue culturing medium which comprises ingredients including sucrose 654 and O2 656 for cells' wellbeing. The supporting material 615 may also comprise drugs or 20 other biologically active compounds 652. When a hollow structure like ball or closed cylinder is printed, by the injection tip 620 injecting the printing material 610 in the direction 635, the supporting material 615 with cells and ingredients are trapped inside of the printable object. When the printable material is biodegradable or resorbable, the printable object which can be implantable device or drug releasing dosier release the 25 cells and active compounds to the region of interest in the target e.g. to start healing tissue defect or disease. MC hydrogel can also be used as reservoir for living cells to be used in drug development for testing effect of the drug against cancer cell invasion. MC supporting 30 material which contains cells like cancer cells and sucrose as the viscosity modifier at the temperature of 37oC is used to print predetermined sized and shaped object of printable materials of matrigel or myomagel (Myogel). Without an effective drug 2023436301   14 Sep 2026 against cancer cells the cells invase from the supporting material, proliferate and migrate to the printed object of matrigel or myogel. On contrary, if the drug is effective against cancer cells, the invasion of cells to the printed matrigel of myogel object is inhibited. The cells' invasion to the printed object which demonstrates effect of the 5 drug is studied microscopically, colorimetrically or by immunological means from the printable object. Precise shape and volume of the printable object by the jelly-like consistency of the supporting material is required to calculate the degree of cell invasion. 10 Other hydrogels than MH can also be adjusted for their viscosity by adding sucrose molecules or some other molecules. Non-ionic polyacrylamide (PAM) ( (C3H5NO)n) -water hydrogel (PAH), cellulose micro fibrils, cellulose nanocrystals, potassium salt, chitosan, alginate, polyvinyl alcohol, starch, gelatin water hydrogels can be adjusted for the required consistency for the application of 3D printing supporting material or 15 bioink. Biodegradable hydrogels are natural-based hydrogels like polysaccharides (e.g. chitosan) and proteins (e.g. collagen), or synthetic such as poly(lactic acid) (PLA), poly(glycolic acid) (PGA) and polypropylene fumarate (PPF). The MC-sucrose-hydrogel can be used due to its environmental nature as supporting 20 material or printable material in 3D printing in all technical fields, due to its biocompatibility in all biotechnical and drug development and production field, and as food ingredient and food production. Even though the invention has been described above with reference to examples 25 according to the accompanying drawings, it is clear that the invention is not restricted thereto but can be modified in several ways within the scope of the appended claims. Therefore, all words and expressions should be interpreted broadly and they are intended to illustrate, not to restrict, the embodiment. It will be obvious to a person skilled in the art that, as technology advances, the inventive concept can be 30 implemented in various ways. Further, it is clear to a person skilled in the art that the described embodiments may, but are not required to, be combined with other embodiments in various ways. 2023436301   14 Sep 2026 It is to be understood that, if any prior art is referred to herein, such reference does not constitute an admission that the prior art forms a part of the common general knowledge in the art, in Australia or any other country. 5 In the claims which follow and in the preceding description of the invention, except where the context requires otherwise due to express language or necessary implication, the word “comprise” or variations such as “comprises” or “comprising” is used in an inclusive sense, i.e. to specify the presence of the stated features but not to preclude the presence or addition of further features in various embodiments of the invention.

Claims

1. A method for printing a 3D printable object, the method comprising: causing an injection tip of a printing element comprised in a printing5 device to move at least horizontally within supporting material such that the injection tip forms a cavern in to the supporting material, wherein the supporting material is complex fluid that has semi-soli gel-consistency and the cavern corresponds to the shape of the 3D printable object;injecting, using the injection tip, printing material into the cavern,10 wherein the printing material comprises biodegradable or biostable resin or resin composite; andallowing a flow of the supporting material to cover the printing material after the movement of the injection tip;wherein the supporting material has gel-consistency and holds protective 15 gas pf polymerization of the injected material evenly distributed in the supporting material.

2. A method according to claim 1, wherein the movement of the injection tip causes local thixotropic drop of viscosity in the walls of the cavern.

203. A method according to claim 1 or 2, wherein a force transmitted to the injection tip by the movement of the injection tip exceeds the yield shear strength of the supporting material.25 4. A method according to any previous claim, wherein the supporting material has gel-consistency that holds diffused oxygen or oxygen gas bubbles evenly distributed in the supporting material.

5. A method according to any previous claim, wherein the supporting30 material comprises molecular, solid, emulsion additives, or gas bubbles that enhance Mie Raleight type scattering of light and the method further comprises applying photopolymerization of the printing material.2023436301   14 Sep 20266. A method according to any previous claim, wherein the supporting material is hydrogel of methyl cellulose comprising added sucrose, and the supporting material is gel at room temperature and pressure, or in a physiological temperature, and 5 wherein the method further comprises melting the printing material in the injection tip before injecting in to a cavity.

7. A method according to claim 6, wherein the method further comprises keeping the temperature of the supporting material lower than the temperature of the 10 printing material.

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