CLIAMS:1. A material system for 3D printing of patient specific scaffolds, the material system comprising:
powder comprising any or a combination of metals, alloys of metals, and ceramic powder particles; and
a binder; wherein the binder is a maltodextrin-based liquid formulation, and wherein the liquid formulation is injected from print-head of a 3D printing machine during the 3D printing of patient specific scaffolds.
2. The material system of claim 1, wherein the powder comprises any or a combination of Ti, Ti-6Al-4V, Co-Cr, stainless steel, hydroxyapatite, alumina, and zirconia powders.
3. The material system of claim 1, wherein water is used as a solvent in the binder formulation.
4. The material system of claim 1, wherein the binder further comprises a surfactant and an antimicrobial agent.
5. The material system of claim 4, wherein the surfactant is Triton×100.
6. The material system of claim 4, wherein the antimicrobial agent is sodium azide.
7. The material system of claim 1, wherein the patient-specific scaffolds are homogeneously porous.
8. The material system of claim 7, wherein the homogeneously porous scaffolds have compressive strength more than 25 MPa and compression modulus less than 3 GPa.
9. The material system of claim 1, wherein the patient-specific scaffold is printed using anatomical location-specific data obtained by computed tomography (CT), and wherein the anatomical location-specific data is processed by a computer-aided design (CAD) software before being used for 3D printing.
10. A method for fabricating patient-specific scaffolds, the method comprising steps:
obtaining location-specific data using computed tomography (CT);
processing the location-specific data by a computer-aided design (CAD) software to generate a STL file;
formulating a maltodextrin-based liquid binder using water as a solvent, Triton×100 as a surfactant and sodium azide as an antimicrobial agent;
selecting a powder wherein the powder comprises any or a combination of Ti, Ti-6Al-4V, Co-Cr, stainless steel, hydroxyapatite, alumina, and zirconia powders;
printing the scaffold on a 3D printing machine, wherein maltodextrin-based liquid binder is injected from printhead of the 3D printing machine;
subjecting the scaffold to hardening and removing loose powder; and
heating the scaffold for binder removal, followed by sintering.
,TagSPECI:TECHNICAL FIELD
[0001] The present disclosure relates generally to the field of rapid prototyping and particularly to three-dimensional (3D) inkjet printing. Specifically, the present disclosure pertains to a material system for 3D printing of human patient-specific implants such as porous biomaterial scaffolds that includes a novel binder formulation.
BACKGROUND
[0002] Background description includes information that may be useful in understanding the present invention. It is not an admission that any information provided herein is prior art or relevant to the presently claimed invention, or that any publication specifically or implicitly referenced is prior art.
[0003] Advent of rapid prototyping (also known as solid free-form manufacturing, and layered manufacturing) enabled production of prototypes or articles and small quantities of functional parts, as well as structural ceramics and ceramic shell molds for metal casting, directly from computer-generated design data. Initial methods to form a three-dimensional article including a selective laser-sintering process did not gain much popularity on account of high cost of equipment and expertize required. Therefore rapid prototyping and its applications remained limited to producing models and prototype parts as a vehicle for visualization and for testing.
[0004] With the invention of three-dimensional printing using an ink-jet print-head at Massachusetts Institute of Technology, fabrication of prototype articles and small quantities of functional parts became a much simpler process and gained popularity. In accordance with the process, an ink-jet print-head is used to deposit a liquid ink or binder onto a print plane i.e. powder bed. The combination of liquid binder and solid powder solidifies to form a finished article.
[0005] The three-dimensional ink-jet printing technique involves applying a layer of a powdered material to a flat surface using a counter roller. After the powdered material is applied to the surface, the ink-jet print-head selectively delivers a liquid binder to the layer of powder. The binder infiltrates into gaps in the powder material, hardening to bond the powder material into a solidified layer. The hardened binder also bonds each layer to the previous layer. After the first cross-sectional portion is formed, the previous steps are repeated, building successive cross-sectional portions until the final article is formed. Optionally, the binder can be suspended in a carrier that evaporates, leaving the hardened binder behind. The powdered material can be ceramic, metal, plastic or a composite material, and can also include fibre. The liquid-binder material can be organic or inorganic. Typical organic binder materials used are polymeric resins, or ceramic precursors such as polycarbosilazane. Inorganic binders are used where the binder is incorporated into the final articles; silica is typically used in such an application.
[0006] In the technology of ink-jet printing, there are a number of different types of print-heads distinguished by the mechanism by which ink is ejected onto the printing plane. The two broadest classes of print-heads are called, "continuous jet" and "drop-on-demand." In a continuous-jet print-head, a liquid ink or binder is projected continuously through a nozzle. To print segmented lines, the jet is deflected alternatively onto the print plane or into a collector that masks the printing plane. In a drop-on-demand print-head, ink or binder is ejected when it is needed by sending an impulse, most usually electrical, that causes an actuator in the print-head to eject a droplet of ink or binder onto the print plane.
[0007] FIG. 1A and FIG. 1B illustrate exemplary schematic representation of 3D powder printing (3DPP) methodology as known in the art. The exemplary representation in FIG.1A pertains to drop-on-demand print-head 104 wherein ink or binder is ejected when it is needed. The process involves creation of a bubble 102 by rapid vaporization at a high temperature such as 350-400° C that usually is attained using a heater 110. Rapid vaporization causes an actuator in the print-head 104 to eject a droplet 106 of ink or binder onto the print plane 108. Thus droplets 106 of ink or binder can be made to flow by sending an impulse, most usually electrical to the print-head 104. Referring to FIG. 1B, the printing plane 108 can be fed with powder 114 by means of a roller 112. As successive layers are printed one over the other, the previous printed layer is lowered to maintain its relationship/distance from the print-head 104. After printing, 3D object can be subjected to sintering to allow the powder to attain its potential mechanical properties
[0008] With 3D printing gaining popularity and acceptance as means for producing prototype articles and small quantities of functional parts, it is natural that its use in the field of human health care is explored where it can be used to fabricate patient-specific scaffolds for load bearing orthopaedic and dental applications.
[0009] The conventional methods for fabricating such implants for the bone tissue applications depend on machining of implantable biomaterials, followed by coating of bioactive material, like hydroxyapatite. This technique is expensive due to excessive loss of material during machining process and involvement of an additional step of coating further increases the cost of implant. Apart from these problems, such implants are not patient-specific and therefore, are at best a compromise in respect of their long term performance. Other techniques, like electron beam melting and selective laser sintering-based 3D printing can be useful to fabricate a patient-specific implant and to improve the performance. However, on account of melting and solidification involved in the process, composite materials that are required to provide both strength and bioactivity cannot be printed using such techniques as they have distinct melting points.
[0010] FIG. 2A illustrates a typical macro and microstructure of bone with vascularized tissues, and FIG. 2B illustrates an exemplary ideal bone material that can provide required structural support for large vessels 252, medium sized vessels 254, and capillary vessels 256, and thus can be helpful in vascularization. Conventional methods of fabrication of implantable devices such as metal casting, sintering, and freeze-drying do not provide such ideal structure, as shown in FIG. 2B.
[0011] FIG. 3A and FIG. 3B illustrate a typical freeze casted 3D structure that does not have any periodic/interconnected pore architecture that could promote vascularization. FIG. 4A and FIG. 4B illustrate exemplary ideal porous scaffolds 400 and 430 for bone tissue engineering applications, and FIG. 4C illustrates a typical micro-CT image 470 of an exemplary ideal porous scaffold showing interconnected pores in 3D scaffold.
[0012] Another aspect of the implants is anatomical location-specific designs that can be helpful in providing an optimum long term performance. The conventional methods of fabrication of implantable devices, such as metal casting, sintering, and freeze-drying do not provide advantage of fabricating anatomical location-specific designs. This can be obtained from computed tomography (CT) data, processed by dedicated computer-aided design (CAD) software. Moreover, blood vessel ingrowth and thus vascularization is hindered in absence of tortuosities pores in implant processed by conventional methods. Additive manufacturing methods such as 3D printing method can overcome these shortcomings related to the tissue specific implant fabrication.
[0013] In another aspect, to ensure long term survival and ability to endure sudden impact, the implants are expected to have sufficient strength with high energy absorption capability as well as good biocompatibility. Metal structures fulfill the requirement of an ideal biomaterial for load bearing orthopedic applications, a role which ceramics fail to perform due to lack of load bearing capability due to inherent brittleness. However, segmental bone defects filled by ceramic materials can be stabilized with the help of supporting metal plates but leads to delay in healing due to insufficient load transfer through implanted ceramic material on account of higher stiffness of supporting metal plates compared to the ceramic porous scaffold. This problem can be taken care by use of a metallic porous scaffold for the filling of bone defects, which is characterized by high strength and low elastic modulus and therefore load transfer through the implant can lead to faster healing. Thus, the use of supporting metal plates can be minimized.
[0014] The above problems associated with conventional methods can be overcome by using 3D powder printing process that can print powder of a metal or hydroxyapatite premixed with metal powder for patient specific designs. The 3D powder printing of patient-specific scaffold of CaPO4 cement based biomaterial has already been investigated by many researchers. However, as discussed above, such ceramic biomaterials are not suitable for the load bearing application and they need external support to minimize the risk of catastrophic failure. The metals/alloys, like Ti and Ti-6Al-4V, CoCr that possess good strength as well as are biocompatible are already in use for implants such as for total hip replacement (THR) as well as total knee replacement (TKR) surgery. These metal implants need high temperature processing, which often leads to oxidation. In this scenario, 3D powder printing can be helpful in fabrication of desired geometry using metal powder at room temperature.
[0015] Table 1 below provides a comparison of 3D printing method with conventional methods for scaffolds fabrication for bone tissue engineering applications.

Properties Conventional processing 3D printing
Approach Replacement of affected bone with implant with limited integration with living tissue Better integration with living tissue around the scaffold due the presence of interconnected and clinically relevant porosity
Structural complexity Very limited Can produce very complex structural features
Porosity Difficult to control the porosity distribution Gradient porosity can be introduced
Mechanical strength Generally stronger than 3D printed prototype Better strength properties can be achieved with intelligent design of multi scale porosity
Time Time consuming process Faster process

Table 1: Comparison of 3D printing method with conventional methods for scaffolds fabrication for bone tissue engineering applications
[0016] At present, 3D powder printers are facing serious limitations due to non-availability of a universal liquid binder for metals and ceramics. Few commercially available binders are very costly and cannot be used for both metals as well as ceramics. Also, chemicals, like phosphoric acid can be used as a binder for the printing. However, associated risk of serious hazard to various machine components with such chemical limits their use as a binder.
[0017] There is therefore a need for a material system for fabricating patient-specific scaffolds for load bearing orthopaedic and dental applications using 3D printing that can overcome the limitations of the conventional methods and material systems.
[0018] All publications herein are incorporated by reference to the same extent as if each individual publication or patent application were specifically and individually indicated to be incorporated by reference. Where a definition or use of a term in an incorporated reference is inconsistent or contrary to the definition of that term provided herein, the definition of that term provided herein applies and the definition of that term in the reference does not apply.
[0019] In some embodiments, the numbers expressing quantities of ingredients, properties such as concentration, reaction conditions, and so forth, used to describe and claim certain embodiments of the invention are to be understood as being modified in some instances by the term “about.” Accordingly, in some embodiments, the numerical parameters set forth in the written description and attached claims are approximations that can vary depending upon the desired properties sought to be obtained by a particular embodiment. In some embodiments, the numerical parameters should be construed in light of the number of reported significant digits and by applying ordinary rounding techniques. Notwithstanding that the numerical ranges and parameters setting forth the broad scope of some embodiments of the invention are approximations; the numerical values set forth in the specific examples are reported as precisely anatomical location-specific designs with certain errors necessarily resulting from the standard deviation found in their respective testing measurements.
[0020] As used in the description herein and throughout the claims that follow, the meaning of “a,” “an,” and “the” includes plural reference unless the context clearly dictates otherwise. Also, as used in the description herein, the meaning of “in” includes “in” and “on” unless the context clearly dictates otherwise.
[0021] The recitation of ranges of values herein is merely intended to serve as a shorthand method of referring individually to each separate value falling within the range. Unless otherwise indicated herein, each individual value is incorporated into the specification as if it were individually recited herein. All methods described herein can be performed in any suitable order unless otherwise indicated herein or otherwise clearly contradicted by context. The use of any and all examples, or exemplary language (e.g. “such as”) provided with respect to certain embodiments herein is intended merely to better illuminate the invention and does not pose a limitation on the scope of the invention otherwise claimed. No language in the specification should be construed as indicating any non-claimed element essential to the practice of the invention.
[0022] Groupings of alternative elements or embodiments of the invention disclosed herein are not to be construed as limitations. Each group member can be referred to and claimed individually or in any combination with other members of the group or other elements found herein. One or more members of a group can be included in, or deleted from, a group for reasons of convenience and/or patentability. When any such inclusion or deletion occurs, the specification is herein deemed to contain the group as modified thus fulfilling the written description of all Markush groups used in the appended claims.
OBJECTS OF THE INVENTION
[0023] An object of the present disclosure is to overcome problems associated with conventional methods for fabricating patient specific scaffolds for load bearing orthopaedic and dental applications.
[0024] Another object of the present disclosure is to provide a material system for fabricating patient specific scaffolds for load bearing orthopaedic and dental applications using 3D printing process.
[0025] Another object of the present disclosure is to provide a material system and method for fabricating tissue specific implants that do not hinder blood vessel ingrowth, and thus promote vascularization by providing tortuosities pores in implant.
[0026] Another object of the present disclosure is to provide a material system and method for fabricating implants that possess long term survival and impact enduring capability as well as good biocompatibility properties.
[0027] Another object of the present disclosure is to provide a material system and method for fabricating implants that minimizes the probability of implant failure due to stress shielding effect.
[0028] Another object of the present disclosure is to provide a material system and method for fabricating implants that possess adequate strength to withstand abrupt impact load.
[0029] Another object of the present disclosure is to provide a material system that uses a liquid binder that is compatible with both metal and ceramic powders.
[0030] Another object of the present disclosure is to provide a material system and method for fabricating implants that reduces cost of implants.

SUMMARY
[0031] Aspects of present disclosure relate to a material system and method for fabricating patient specific scaffolds (also referred to as implants and the two terms used interchangeably hereinafter) for load bearing orthopaedic and dental applications. In an aspect, the disclosure provides for fabrication of anatomical location-specific implants by 3D printing method using location-specific data obtained using computed tomography (CT) and processed by dedicated computer-aided design (CAD) software.
[0032] In another aspect, the present disclosure provides a material system that is biocompatible and results in implants that are strong enough to avoid catastrophic failure due to abrupt impact and yet possess adequate resilience to avoid failure due to stress shielding effect. In an aspect, the implants fabricated using the disclosed method and material system incorporate macropores created by CAD design and micropores in strands of 3D powder printed scaffolds that provide it adequate resilience. At the same time, metallic constituent in the material system gives it enough compressive strength to withstand impact loads. In yet another aspect of the disclosure, interconnected pores in the scaffolds fabricated using the disclosed material system and method can enable blood vessel ingrowth and thus promote vascularization.
[0033] In another aspect of the disclosure, the material system can include one or more powders selected out of various metal and alloy powders such as Ti, Ti-6Al-4V, Co-Cr, stainless steel as well as ceramics, such as hydroxyapatite, alumina, and zirconia. Further a binder that can be used in liquid form for injection through print-head of an inkjet printer and is compatible with metal and/ or ceramics has been provided. In an embodiment, formulation of a maltodextrin-based liquid binder for the thermal inkjet printing of scaffolds of metal and/ or ceramics is provided. In an aspect, use of liquid binder through the print-head does away with cumbersome process of premixing of powder material with an adhesive.
[0034] In an aspect, the disclosure also provides a method for binder formulation and preparation, post-printing treatment and post-fabrication treatment. For maltodextrin-based binder preparation, water can be used as a solvent with Triton-×100 added as a surfactant and sodium azide added to prevent the bacterial/fungal contamination to the binder. During post-printing treatment, the printed structure can be illuminated with 100 Watt bulb for 30 minutes to improve strength of the printed scaffold followed by de-powdering of the scaffolds to remove the loose powder. Post-fabrication treatment can be carried out by heating the scaffolds for binder removal, followed by sintering in an inert atmosphere. The exemplary scaffold can be subjected to heating at 450 °C and sintering can be performed at 1300 °C in argon atmosphere.
[0035] In an aspect, scaffolds for load bearing orthopedic application that are fabricated using the disclosed material system and method, exhibit comparable properties (from the perspective of stress shielding effect and ability to withstand impacts) to those fabricated using conventional processes such as electron beam melting (EBM) and selective laser sintering (SLS). The exemplary homogenously porous scaffolds of the present disclosure show modest strength in combination with lower elastic modulus than their solid counterpart fabricated by conventional methods. Lower elastic modulus gives them enough resilience to ward off stress shielding effect, while the modest strength is adequate to withstand abrupt impact forces to avoid catastrophic failures. The exemplary homogenously porous 3D printed scaffold fabricated using the disclosed material system and method showed a compressive strength and elastic modulus of 27 MPa and 2 GPa, respectively compared to 546 MPa and 10 GPa, respectively of graded porous scaffold. Apart from macropores created by CAD design, presence of micropores in strands of the proposed 3D powder printed scaffolds results in decreased elastic modulus.
[0036] Various objects, features, aspects and advantages of the inventive subject matter will become more apparent from the following detailed description of preferred embodiments, along with the accompanying drawing figures in which like numerals represent like components.
BRIEF DESCRIPTION OF THE DRAWINGS
[0037] The accompanying drawings are included to provide a further understanding of the present disclosure, and are incorporated in and constitute a part of this specification. The drawings illustrate exemplary embodiments of the present disclosure and, together with the description, serve to explain the principles of the present disclosure.
[0038] FIG.1A and FIG. 1B illustrate exemplary schematic representation of 3D powder printing (3DPP) methodology as known in the art.
[0039] FIG. 2A and FIG. 2B illustrate a typical macro and microstructure of bone with vascularized tissues and an exemplary ideal implant structure that can provide required structural support and vascularization.
[0040] FIG. 3A and FIG. 3B illustrate a typical freeze casted 3D structure that does not have any periodic/interconnected pore architecture that could promote vascularization.
[0041] FIG. 4A to FIG. 4C illustrate typical ideal porous scaffolds for the bone tissue engineering applications and micro-CT image of scaffold of FIG. 4B showing the interconnected pores in 3D scaffold.
[0042] FIG. 5 illustrates an exemplary heating cycle to sinter a 3D printed scaffold of Ti-6Al-4V powder in accordance with the present disclosure.
[0043] FIG.6A illustrates an exemplary block diagram of work flow for fabricating patient specific scaffolds/implants in accordance with the present disclosure.
[0044] FIG.6B illustrates an exemplary flow diagram for fabricating patient specific scaffolds/implants in accordance with the present disclosure.
[0045] FIG. 7 illustrates exemplary compressive stress – strain diagrams of 3D printed scaffolds with gradient structure (one side porous and other side solid) along with its CAD design and actual 3D printed scaffolds in accordance with embodiments of the present disclosure.
[0046] FIG. 8 illustrates exemplary compressive stress – strain diagrams of 3D printed scaffolds with uniform porous architecture respectively along with its CAD design and actual 3D printed scaffolds in accordance with embodiments of the present disclosure.
DETAILED DESCRIPTION
[0047] The following is a detailed description of embodiments of the disclosure depicted in the accompanying drawings. The embodiments are in such detail as to clearly communicate the disclosure. However, the amount of detail offered is not intended to limit the anticipated variations of embodiments; on the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the present disclosure as defined by the appended claims.
[0048] Each of the appended claims defines a separate invention, which for infringement purposes is recognized as including equivalents to the various elements or limitations specified in the claims. Depending on the context, all references below to the "invention" may in some cases refer to certain specific embodiments only. In other cases, it will be recognized that references to the "invention" will refer to subject matter recited in one or more, but not necessarily all, of the claims.
[0049] As used in the description herein and throughout the claims that follow, the meaning of “a,” “an,” and “the” includes plural reference unless the context clearly dictates otherwise. Also, as used in the description herein, the meaning of “in” includes “in” and “on” unless the context clearly dictates otherwise.
[0050] All methods described herein can be performed in any suitable order unless otherwise indicated herein or otherwise clearly contradicted by context. The use of any and all examples, or exemplary language (e.g. “such as”) provided with respect to certain embodiments herein is intended merely to better illuminate the invention and does not pose a limitation on the scope of the invention otherwise claimed. No language in the specification should be construed as indicating any non-claimed element essential to the practice of the invention.
[0051] Various terms as used herein are shown below. To the extent a term used in a claim is not defined below, it should be given the broadest definition persons in the pertinent art have given that term as reflected in printed publications and issued patents at the time of filing.
[0052] Embodiments of the present disclosure relate to a material system and method for fabricating patient specific scaffolds/implants for load bearing orthopaedic and dental applications. The bone defects created due to injury and malignancy can be treated using suitable biomaterial to restore the body function. For faster wound healing, it is important that the properties of implantable biomaterials match the host tissues. Ideally, the scaffold should perform various functions, like providing temporary or permanent support to the damaged part and supporting cell colonization, migration, proliferation, and differentiation for enhanced bone growth and vascularization. As is known in the art, these properties are related to the material composition, its physical properties (e.g. stiffness), pore size and pore interconnectivity.
[0053] In an embodiment, the present disclosure provides a material system that is bio compatible and results in implants that are strong enough to avoid catastrophic failure due to abrupt impact and yet possess adequate resilience to avoid failure due to stress shielding effect. In an aspect, the implants fabricated using the disclosed method and material system incorporate macro pores created by CAD design and micropores in strands of 3D powder printed scaffolds that provide it adequate resilience. At the same time, metallic constituent in the material system gives it enough compressive strength to withstand impact loads. In yet another aspect of the disclosure, interconnected pores in the scaffolds fabricated using the disclosed material system and method can enable blood vessel ingrowth and thus promote vascularization.
[0054] In 3D printing, two methodologies are generally used to bind the loose metal/ceramic powder into a green body. The first method involves addition of a liquid binder directly on powder stack to bind the powder particles. In the second, powder is mixed with an adhesive such as polyvinyl alcohol (PVA) or polysaccharide e.g. maltodextrin and water or alcohol used as a liquid binder. In the second approach, liquid binder dissolves the adhesive present in the powder and thus allows the binding of powder particles during 3D printing. However, premixing of adhesive to the base powder can lead to the generation of additional non-uniform porosity in the sintered scaffolds due to removal of adhesive during heating cycle and resultant decreased mechanical properties. Besides, the additional step of mixing leads to additional cost. In contrast, first method provides an easy and convenient method printing of 3D scaffolds at low cost. The first approach is significantly affected by the physical and chemical properties of the binder which depend on the composition of the binder. Therefore, it is very important to understand the role of each component added in the solvent in respect of viscosity, vaporization temperature, and surface tension. Additionally, the liquid binder should also possess antibacterial and antifungal properties to avoid the clogging of the print-head. Most importantly, binder should not be very acidic or alkaline to prevent the permanent damage to the print-head and machine components. It is therefore desirable to use the first approach (direct binder addition) for the 3D printing in place of using an adhesive in the powder.
[0055] In an embodiment, the disclosure provides a material system for 3D printing of patient specific scaffolds, that can include one or more powder selected out of various metal and alloy powders such as Ti, Ti-6Al-4V, Co-Cr, stainless steel as well as ceramics, such as hydroxyapatite, alumina, and zirconia. Further, a binder that can be used in liquid form for injection through print-head of an inkjet printer and is compatible with metal and/ or ceramics has been provided. In an embodiment, formulation of a maltodextrin-based liquid binder for the thermal inkjet printing of scaffolds of metal and/ or ceramics is provided. In an aspect, use of liquid binder through the print-head does away with cumbersome process of premixing of powder material with an adhesive.
[0056] In an embodiment, the disclosure provides method for binder formulation and preparation, wherein a maltodextrin-based binder is prepared using water as a solvent with Triton-×100 added as a surfactant and sodium azide added to prevent bacterial/fungal contamination to the binder. Table 2 below illustrates the composition of an exemplary maltrodextrin based binder for 3D powder printing of metal and ceramics.
Materials Amount (for 100 ml binder) Role
Water 100 ml Solvent
Maltodextrin 20 g Binder
Triton×100 1 ml Surfactant
Sodium azide 10 mg Antimicrobial agent

Table 2: The formulation of maltrodextrin-based binder for 3D powder printing of metal and ceramics

[0057] In an embodiment, the present disclosure provides a method of post-printing treatment and post-fabrication treatment. During post-printing treatment, the printed structure can be illuminated with 100 Watt bulb for 30 minutes to improve the strength of the printed scaffold followed by de-powdering of the scaffolds to remove the loose powder. Post-fabrication treatment can be carried out by heating the scaffolds for binder removal, followed by sintering in an inert atmosphere. The exemplary scaffold was subjected to heating at 450 °C and was sintered at 1300 °C in argon atmosphere. FIG. 5 illustrates an exemplary heating cycle to sinter a 3D printed scaffold of Ti-6Al-4V powder indicating heating at 450°C for 60 min for binder removal followed by sintering at 1300 °C for 120 min.
[0058] FIG.6A illustrates an exemplary block diagram 600 of work flow for fabricating patient specific scaffolds/implants in accordance with the present disclosure, wherein at step 602 a STL file of patient specific scaffold is generated. In an aspect, location-specific data obtained using computed tomography (CT) and processed by dedicated computer-aided design (CAD) software can be used to develop the STL file. At step 604, based on the STL file of patient specific scaffold, a 3D powder printing machine can be used to fabricate a patient specific scaffold, wherein the powder used for fabrication can include one or more powder selected out of various metal and alloy powders such as Ti, Ti-6Al-4V, Co-Cr, stainless steel as well as ceramics, such as hydroxyapatite, alumina, and zirconia. The binder used for printing can be a maltodextrin-based formulation. At step 606, the fabricated scaffold can be post-printing treatment during which the printed structure can be illuminated with 100 Watt bulb for 30 minutes to improve the strength followed by de-powdering of the scaffolds to remove the loose powder. At step 608, a post-fabrication treatment can be carried out by heating the scaffolds for binder removal, followed by sintering in an inert atmosphere. The exemplary scaffold of Ti-6Al-4V powder was subjected to heating at 450 °C and was sintered at 1300 °C in argon atmosphere. 610 and 612 illustrate exemplary micro-CT images of the scaffold after completion of the process.
[0059] FIG.6B illustrates an exemplary flow diagram 650 for process of fabricating patient specific scaffolds/implants in accordance with the present disclosure wherein step 652 of the process can involve obtaining anatomical location-specific data using computed tomography (CT). The obtained location-specific data can at step 654 be processed by a dedicated computer-aided design (CAD) software to develop a STL file. Step 656 can be formulating a maltodextrin-based liquid binder, wherein water can be used as solvent, Triton×100 as a surfactant and sodium azide as an antimicrobial agent. Powder to be used for 3D printing of the scaffold can be selected at step 658, wherein the powder can be any or a combination of Ti, Ti-6Al-4V, Co-Cr, stainless steel, hydroxyapatite, alumina, and zirconia powders. At step 660, a 3D printing machine can be used to print a scaffold based on the STL file using the selected powder and maltodextrin-based liquid binder wherein the liquid binder is injected from print-head of the printer. At step 662, the fabricated scaffold can be subjected to post-printing treatment such as hardening during which the printed structure can be illuminated with 100 Watt bulb for 30 minutes to improve the strength followed by de-powdering of the scaffolds to remove the loose powder at step 664. A post-fabrication treatment can be carried out at step 666 by heating the scaffolds for binder removal. The exemplary scaffold of Ti-6Al-4V powder was subjected to heating at 450 °C for binder removal. At step 668, the scaffold can be subjected to sintering in an inert atmosphere. The exemplary scaffold of Ti-6Al-4V powder was subjected to sintering at 1300 °C in argon atmosphere.
[0060] In an aspect, the scaffolds for load bearing orthopedic application, which are fabricated using the disclosed material system and method, exhibit superior combination of properties (from the perspective of stress shielding effect and ability to withstand impacts) when compared to those fabricated using conventional processes, such as electron beam melting (EBM) and selective laser sintering (SLS). As shown in the Table 3 below, the exemplary homogenously porous scaffolds, show modest though lower, strength in combination with lower elastic modulus than their solid counterpart fabricated by conventional methods. Lower elastic modulus gives them enough resilience to ward off stress shielding effect, while the modest strength is adequate to withstand abrupt impact forces to avoid catastrophic failures. In an embodiment, the exemplary homogenously porous 3D printed scaffold fabricated using the disclosed material system and method show a compressive strength and elastic modulus of 27 MPa and 2 GPa respectively compared to 546 MPa and 10 GPa respectively of graded porous scaffold. Apart from macropores, created by CAD design, the presence of micro pores in strands of 3D powder printed scaffolds results in decreased elastic modulus.
Manufacturing technology Structural features Porosity (%) Mechanical properties
Compressive Strength
(MPa) compression modulus
(GPa)
Electron beam melting Homogeneously porous 65 110 3
Graded porous 46 367 65
Selective laser melting Scaffold with rectangular struts 70 155 5
Scaffold with shifted strut alignment 72 145 4
Scaffold with diagonal struts 69 164 7
3D powder printing Homogeneously porous
40 27 2
Graded porous 546 10
Table 3: Comparison of mechanical properties of 3D scaffold of Ti-6Al-4V alloy fabricated by various additive manufacturing methods

[0061] FIG. 7 and FIG. 8 illustrate exemplary compressive stress – strain diagrams of 3D printed scaffolds with gradient structure (one side porous and other side solid) and uniform porous architecture respectively along with their CAD design and actual 3D printed scaffolds in accordance with embodiments of the present disclosure. Both the scaffolds were made of Ti-6Al-4V powder. The compressive stress – strain diagrams make it clear that scaffold with uniform porous architecture undergoes successive failure due to homogeneously distributed pores resulting in high energy absorption capability as compared to scaffold with non-uniformly distributed pores that exhibits a sudden failure. This clearly brings out the superiority of a scaffold having a uniform porous architecture that results in better resilience and energy absorption capability of the scaffold and thus prevent failure due to stress shielding.
[0062] Thus, the 3D powder printed porous scaffolds using disclosed material system are characterized by mechanical properties comparable to the scaffolds fabricated by well-known additive manufacturing methods such as EBM and SLS. Therefore, the newly developed binder has been found to be useful in producing tissue specific implant at much lower cost due to economical processing.
[0063] While the foregoing describes various embodiments of the invention, other and further embodiments of the invention may be devised without departing from the basic scope thereof. The scope of the invention is determined by the claims that follow. The invention is not limited to the described embodiments, versions or examples, which are included to enable a person having ordinary skill in the art to make and use the invention when combined with information and knowledge available to the person having ordinary skill in the art.

ADVANTAGES OF THE INVENTION
[0064] The present disclosure overcomes problems associated with conventional methods for fabricating patient specific scaffolds for load bearing orthopaedic and dental applications.
[0065] The present disclosure provides a material system for fabricating patient specific scaffolds for load bearing orthopaedic and dental applications using 3D printing process.
[0066] The present disclosure provides a material system and method for fabricating tissue specific implants that do not hinder blood vessel ingrowth and thus promotes vascularization by providing tortuosities pores in implant.
[0067] The present disclosure provides a material system and method for fabricating implants that possess long term survival and impact enduring capability as well as good biocompatibility properties.
[0068] The present disclosure provides a material system and method for fabricating implants that minimizes the probability of implant failure due to stress shielding effect.
[0069] The present disclosure provides a material system and method for fabricating implants that possess adequate strength to withstand abrupt impact load.
[0070] The present disclosure provides a material system that uses a liquid binder that is compatible with both metal and ceramic powders.
[0071] The present disclosure provides a material system and method for fabricating implants that reduces cost of implants.