These features highly mimicked axons and presynaptic terminals [98]. To enable out-of-plane printing, several companies and researchers are developing extrusion AM systems for polymers that use a robotic arm for deposition [2022]. The authors combined this optimal scaffold geometry with low-intensity pulsed ultrasound (LIPUS) and achieved improved HMSCs function evaluated by increased proliferation, calcium deposition, total protein content, and alkaline phosphatase activity [94]. Combined with appropriate open porosity, the bioscaffold could enhance bone regeneration and allow the ingrowth of blood vessels.

The build platform can be moved vertically up and down while the nozzle can move horizontally in an x-y direction. Figure 11.5. Although LFAM systems do not employ heated enclosures, other approaches to reduce part warping and deformation, such as a combination of high throughput and printing with CFreinforced systems, have been demonstrated to be effective [5,23]. (4) Exposure apparatus: Atlas Weather-Ometer. Xinchang Zhang, Frank Liou, in Additive Manufacturing, 2021. Fig. The flexible and mechanically robust material retained its electrical conductivity (higher than 800S/m), and in the absence of neurogenic stimuli, it supported HMSC adhesion, proliferation, viability, and neurogenic differentiation. Maria P. Nikolova, Murthy S. Chavali, in Additive Manufacturing, 2021, Utilizing material extrusion, vat photopolymerization or cell printing techniques, AM could be used for the fabrication of organs, blood vessels, ligaments, soft tissue, and bone prosthesis. (5) Exposure time (days): 83.3. Join our Community and stay up-to-date. 80 (2015) 369378. After extrusion, once the material sets and forms a strong bond between layers. Figure 8.24. 8.5. Currently, industrial adoption of this technology is still limited due to high capital cost, limited reach of the robotic arm (build volume), limited maximum weight capacity of the arm, and control system complexity. The main issue for polymer/nanoceramic composites remains the agglomeration of the ceramic NPs in the polymer matrix. Apart from the advantages of hydrogels that most closely simulate the native tissue environment concerning water content, texture, morphology, and biodegradability, for some highly loaded hard tissue applications, they have inadequate mechanical performance. This is also referred to as Plastic Jet Printing. Rasheedat Modupe Mahamood, Esther T. Akinlabi, in Additive Manufacturing, 2021. Gantry systems are easier to control, more economical, and possess the most robust deposition accuracy among the existing motion systems. Note: (1) Density: 0.95g/cm3. MTT analysis suggested that the doped samples triggered increased cellular attachment and proliferation [88]. Tensile strength after Weather-Ometer exposure of Chevron Phillips Marlex HDPE with 1% TiO2 and various UV absorbers.4, Figure 8.28. Different strategies for integrating reinforcements have been investigated in recent works (Asprone et al., 2018; Mechtcherine et al., 2018). Tensile strength after Arizona outdoor weathering of yellow Chevron Phillips Marlex HDPE.4, Figure 8.20. 1.5 shows an illustration of the FDM process [9]. For example, the 3D-printable nanocellulosealginate porous hydrogel was found to be a suitable platform for the development of drug-releasing material for wound healing. Material extrusion is now the most popular additive manufacturing process in terms of availability for general consumer demand and quality.

In LFAM processes, for both thermoplastics and reactive extrusion, the build platform consists of precision-machined aluminum platens with a stainless steel substructure. Additive processing of biopolymers for medical applications, Polymer and composites additive manufacturing, Additive manufacturing in skin systems: trends and future perspectives, Buswell, Leal de Silva, Jones, & Dirrenberger, 2018, Asprone et al., 2018; Mechtcherine et al., 2018, There are several aspects of geometric design that affect scaffold mechanical performance. Tensile strength after Weather-Ometer exposure of Chevron Phillips Marlex HDPE with various degrees of carbon black pigment dispersion.4, Figure 8.29. Ceramic faade components have been printed at a smaller scale and higher resolution by StudioRAP (Studio RAP, 2019) (Fig. However, the uncontrolled release of metal or oxide NPs from scaffolds is still an unresolved issue because they may not be taken by the surrounding cell, and if translocated to other organs, they can cause undesired toxicity or other adverse effects. Fused filament fabrication (FFF) and fused deposition modeling (FDM) are two examples of material extrusion technology. There are many other factors related to the scaffold design that affect mechanical properties, as identified in more detail elsewhere [8,84]. For material extrusion additive manufacturing, the orientation of extruded filaments has been widely studied and shown to be an important factor for mechanical performance [65,73,74,79]. A wide variety of biomaterials can be printed in FDM, and the most common biopolymers are PLA and PCL with a low melting point, which are well known for their biocompatible and biodegradable properties and hence, widely used for medical applications [74]. There is lots to learn and discover about AM in the fast-paced world of technology. 8.3. Table 8.1. Moreover, the 3D-printed hydrogels cross-linked with CaCl2 showed the potential to be functionalized with small bioactive molecules such as biotin, growth factors, antibodies, antibiotics, or peptides that are required as specific adhesion-mediated signals. Time of exposure in Weather-Ometer to 50% tensile retention vs. concentration of HAS in HDPE tape.1. Finite element analysis simulations demonstrate how staggered filaments in a scaffold lead to a lower elastic modulus. Material extrusion is an AM technique in which a polymer filament is continuously fed into the printing area through extruding nozzles where it will be heated (usually in the range of 150250C) and then deposited onto the building platform layer by layer. Figure 17.3.

These capabilities have resulted in the application of MEX technologies in a diverse range of commercial fields including the development of functional engineering prototypes and systems, and the fabrication of high-value clinically functional materials. Tensile strength after Weather-Ometer exposure of orange Chevron Phillips Marlex HDPE.4. Tensile strength after Weather-Ometer exposure of red Chevron Phillips Marlex HDPE.4, Figure 8.22. Figure 8.34. Irrespective of the build volume, a majority of widely adopted AM systems for polymers and composites use a three-axis gantry-based motion platform. Compared with pure TCP scaffold, the doped samples revealed decreased porosity and a 250% increase in compressive strength. Initiation step of the photooxidation in polyethylene. This greatly reduces the need for support structures, especially for applications that demand structures with overhangs at angles greater than 45 degrees. Overall, benefits of ME include low cost, high speed, and simplicity of the process. Tensile Strength after Accelerated Weathering of Chevron Phillips Marlex HDPE with UV Absorber and Various Orange Pigment Systems4. The platform is also equipped with a vacuum port to hold down the build sheets on which the parts are printed, facilitating ease of removal. (3) Test method ASTM 01499. Despite the extensive application of MEX technologies, there remain significant opportunities for commercially relevant research contributions in this space. However, these enclosures add to the overall energy consumption and limit process scalability. This allows the complete elimination of support structures and the production of dynamic, nonplanar surfaces with higher quality surface finish, more design flexibility, and greater part strength.

The regeneration of damaged neurogenic tissue remains a challenging task because most of the implanted scaffolds demonstrate a lack of electrical properties.

Material Extrusion. CaP incorporation facilitates the proliferation of human osteoblast-like cell line (SaOS-2) and ALP expression, No statistical difference in cell proliferation was found for CHA/PLLA and PLLA indicating concentration dependence, Initial burst released of the protein was observed because of diffusion from the surface, After that, nearly constant release for 28days was observed, Nanodoped scaffolds were more hydrophilic than micro-HA/PCL scaffolds, The attachment and MG-63 cell proliferation on nanoHA/PCL was better than on micro-HA/PCL scaffolds, The majority of CNTs/PCL nanocomposites showed good MG-63 compatibility with values higher than 75% as opposed to the bare PCL, Osteoblast viability depended on the intrinsic rigidity of the substrate, 15wt% GS-loaded scaffold was able to eliminate both G+ and G bacteria (Pseudomonas aeruginosa and Staphylococcus aureus) within 2h and demonstrated good biocompatibility with dermal fibroblast cells, The wounds in mice model healed rapidly and were earlier reepithelized with no signs of overall infection by day 7, 15wt% GS-loaded scaffold demonstrated antiadhesive properties, Cells of modified human osteoblast cell line (HOB) attached and anchored on the composite substrate, The samples were nontoxic for the osteoblast cells, The scaffolds promoted osteoblast infiltration, The cell was well spread and attached on the surface of the scaffolds, Osteoblast infiltration in the pores was 4.2 times greater than adhesion on the surface, Preosteoblastic cells (MC3T3-E1) adhered and spread well-forming intimate contact with micropore surface. A widely used printing process based on the material extrusion technique is fused deposition modeling (FDM), also known as fused filament fabrication. Various biomedical materials such as metals, alloys, bioactive glasses, plastics, and ceramics have been used for implant 3D manufacturing [71]. Tensile Strength after Accelerated Weathering of Chevron Phillips Marlex HDPE with Various Degrees of Pigment Dispersion4. The 3D-printed composite hydrogel architecture was encoded with localized anisotropic swelling behavior determined by the cellulose nanofiber alignment along prescribed 4D printing paths. The extrusion head is usually lightweight in comparison with a gantry-based system, and the work area or the build space is also much larger. } NPs loaded in a hydrogel matrix could also generate multiplexed spatial gradients, while the particles properties could be adjusted to control the payload release kinetic. Figure 8.3. (2) Hydroxybenzophenone (UV absorber): 0.5%, CP Cadmium red 0.5%. Personalized product innovation through digitalization to meet market demands and reduce costs, Faster time to market, fewer errors for Software Development. Figure 8.4. .breadcrumb_a_span1:before { content: 'Our Story'; } However, ceramic interconnected porous scaffolds fabricated directly using direct inkjet printing and sintering of nanopowder (550nm) of TCP with silica (SiO20.5wt%) and ZnO (0.25wt%) additives demonstrated enhanced mechanical and biological properties. Desktop-scale gantry systems are capable of speeds up to 60mm/s. Variation in hardness of LDPE vs. accelerated aging duration under Weather-Ometer weathering conditions.2, Figure 8.17.

[72]. Data for Ultrahigh molecular weight polyethylene plastics is found in Fig. Here, the extrusion head is moved throughout the workspace by manipulating the lengths of the cables used. One option is to print an electroactive scaffold from liquid ink. Tensile Strength after Accelerated Weathering of Chevron Phillips Marlex HDPE with UV Absorber and Various Yellow Pigments4. A number of companies are currently providing equipment for large-scale 3D concrete printing (3DCP), which is by volume the most utilized material in the market of additive construction (Lee et al., 2019). One can imagine how branching in the polymer chain can disrupt the crystalline regions. Data for LDPE plastics are found in Figs 8.138.18. With six degrees of freedom, robotic arms make printing more flexible and enable novel deposition strategies for out-of-plane printing and printing over curved surfaces. Material extrusion is an additive manufacturing technique that uses a continuous filament of thermoplastic or composite material to construct 3D parts. Variation in hardness of LDPE vs. accelerated aging duration under QUV-weathering conditions.2, Figure 8.18. (4) Exposure apparatus: Atlas Weather-Ometer. It has been shown that the alignment of filaments across multiple layers of an additively manufactured scaffold increases the elastic modulus [8083], which is to be expected from computer simulations as shown in Fig. (5) Exposure note: exposure time indicates time required to cause surface crazing and cracking. Table 8.7. Note: (1) Density: 0.95g/cm3.

Figure 8.26. Fused filament fabrication (FFF) is another type that falls under this category developed by the members of the RepRap project which is not restricted to use by others. To obtain processability along with end-use properties, control of the molecular weight distribution is critical. Manufacturers and trade names: Dow Chemical Dowlex, Exopack Sclairfilm, ExxonMobil Chemical. .breadcrumb_a_span2:before { content:''; } Most material extrusion AM systems are out-of-oven deposition systems, devoid of heated enclosures. Variation in hardness of LLDPE vs. accelerated aging duration under QUV-weathering conditions.3. (4) Exposure apparatus: Atlas Weather-Ometer. After finishing the deposition of one layer, the print bed moves in the Z direction in a layer thickness for the printing of the next layer. HDPE polymers are highly crystalline, tough materials. More complex and intricate geometries can be created with 5-axis ME setups that enable the nozzle to rotate on two axes in addition to 3D movement. Figure 8.19. Although gantry-based systems are reliable and easy to operate, with their limited degrees of freedom (three), they are primarily suited only for planar structures and not for out-of-plane printing applications without an additional support structure. Accumulating in the intended location, magnetic NPs can be used for initiation of drug desorption, hyperthermia therapy in cancer cells under alternating magnetic field [99] or even visualizing the place by magnetic resonance imaging. Table 8.2. Variation in density of LLDPE vs. accelerated aging duration under Weather-Ometer weathering conditions.3, Figure 8.10. It was found out that the magnetic alignment of 15wt% of platelets in the tensile loading direction increased the strength, elastic modulus, and swelling strain by 49%, 52%, and 30%, respectively, compared with perpendicularly aligned platelets. Table15.2 summarizes the effect of the different NPs embedded in ceramic, polymer, or hydrogel scaffold on the biological performance of the nanocomposites. By printing from different directions, in fact, the part can come out much sturdier than by simply stacking layers in the Z direction. From left, COBOD (2020) BOD2 Gantry printer; WASP Crane Printer for Clay; Ceramic production by Studio RAP (2020).

PEGDA/magnetite cartilage scaffold and PCL/magnetite bone scaffolds indicated good adhesion and spreading of HMSCs without applying an external magnetic field that was thought to guide bone regeneration [100]. 11.5AD). 8.26). This process continues so that the physical object can be obtained based on the CAD model. B Eng. The term fused deposition modeling (FDM) and its abbreviation FDM are trademarked by StratasysInc, a company co-founded by Scott Crump. (4) Exposure apparatus: Atlas Weather-Ometer. For example, a mixture of bioresorbable and easily available PCL, montmorillonite (MMT), and HA nanofiller was successfully produced as new feedstock filament for the FDM process [90]. Siemens PLM Software, a leader in media and telecommunications software, delivers digital solutions for cutting-edge technology supporting complex products in a rapidly changing market.

@media (min-width:768px) { Table 8.3. Conceptual Designis an early phase of thedesignprocess, in which the broad What is Stress concentration? High molecular weight, HDPEs (HMW-HDPE) are a special class of linear resins with molecular weights in the 200,000500,000 range. FDM also has many drawbacks. We use cookies to help provide and enhance our service and tailor content and ads. (3) Test method ASTM 01499. Table 8.6. enhanced invitro cartilage tissue culturing while giving auditory sensing for radio frequency (up to 5GHz) reception of 3D-printed bionic ear [97]. 8.6. @media (min-width:768px) { For, The Effect of UV Light and Weather on Plastics and Elastomers (Third Edition), Specimen type: ASTM D638, type IV; strain rate: 508, Specimen type ASTM D638, type IV, strain rate 508, Specimen Type ASTM D638, Type IV, strain rate 508, 3D network of interconnected pores from powder 58S (3060, Scaffolds with different compositions (TCP/HA: 0/100, 10/90, 30/70, 50/50, 70/30, and 100/0); porosity 61%; pore size ranged in 0.81.2, Invitro studies with MG-63 indicated that TCP/HA (30/70) and TCP/HA (50/50) revealed higher biological efficiency because of the optimal balance between stability and dissolution rate of the scaffold, Scaffolds with interconnected pores with different 58S content, MG-63 cell adhesion enhanced with increase in the amount of nano-58S bioactive glass, Highly interconnected porous scaffold with macropores (350450, No scaffolds fabricated because of PVA particle fused when CS reached 20, A tetragonal porous scaffold of biomolecule-loaded microspheres that protect their biological activity and temporally released them, Scaffolds with interconnected macropores; 72%73% porosity; pore size 500, Scaffolds with hexagonal square, octagonal cell grids, and 3D bone-like morphology and changing ration of CNTs to PCL (from 5.9 to 83 relative wt% CNTs), Wound healing PCL-20% TCP scaffold with honeycomb-like pattern loaded with gentamicin sulfate (GS5, 15, and 25, Different cylindrical porous scaffolds with 20.5 vol% TCP, the pore size of 160, Composite cubic scaffolds with cubic pores (100, Ultranox 626 (AntioxidantGeneral Electric), Weston 619 (AntioxidantGeneral Electric). Hydrogels are commonly synthesized in 3D bioprinting process by hydrophilic polymer chains in a water-based environment. Light and weathering resistance of semifinished and finished products made from Ticona GUR UHMWPE exhibit surface embrittlement within about 3months when used in outdoor applications under central European climatic conditions. Figure 8.7. (5) Exposure time (days): 333.3.