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Processing of 45S5 Bioglass® by lithography-based additive manufacturing
Materials Letters 74 (2012) 81–84
Contents lists available at SciVerse ScienceDirect
Materials Letters journal homepage: www.elsevier.com/locate/matlet
Processing of 45S5 Bioglass® by lithography-based additive manufacturing Passakorn Tesavibul a,⁎, Ruth Felzmann a, Simon Gruber a, Robert Liska b, Ian Thompson c, Aldo R. Boccaccini d, Jürgen Stampfl a a
Institute of Materials Science and Technology, Vienna University of Technology, Favoritenstraße 9-11/E308, A-1040 Vienna, Austria Institute of Applied Synthetic Chemistry, Vienna University of Technology, Getreidemarkt 9/E163, 1060 Vienna, Austria Dental Institute, Biomaterials Unit, King's College London, London SE1 9RT, UK d Institute of Biomaterials, Department of Materials Science and Engineering, University of Erlangen-Nuremberg, Cauerstr. 6, 91058 Erlangen, Germany b c
a r t i c l e
i n f o
Article history: Received 5 October 2011 Accepted 5 January 2012 Available online 12 January 2012 Keywords: Biomaterials Biomimetic Porous materials Structural
a b s t r a c t Lithography-based Additive Manufacturing Technologies (AMTs) were used for fabricating cellular structures made of 45S5 Bioglass®. Using AMTs it is possible to design and fabricate cellular structures with a resolution of around 40 μm and wall thicknesses down to 200 μm. The presented process relies on selectively polymerizing a photosensitive, ceramic-filled resin with a dynamic mask. The dynamic mask is based on a digital mirror array which projects blue light (light emitting diodes with a wavelength of 460 nm) onto the resin. The mechanical properties of sintered bulk samples (biaxial strength) and cylindrical cellular structures (compressive strength) were determined. The biaxial strength of the manufactured samples was 40 MPa, and the compressive strength of the cellular structure was 0.33 MPa, which is slightly lower than the strength of porous Bioglass® structures made by the foam replica method. Lithography-based AMT offers an excellent alternative to existing bone implant and scaffold fabrication methods providing accurate control of 3D morphology and pore architecture. © 2012 Elsevier B.V. All rights reserved.
1. Introduction Bone tissue engineering (BTE) requires scaffolds (3D porous structures) fabricated with materials which exhibit high surface reactivity in physiological fluids leading to the formation of strong bonds to bone tissue [1,2]. These scaffolds must exhibit high and interconnected porosity, and in combination with relevant cells and signaling molecules, should promote the regeneration of new vascularized bone tissue [2,3]. Bioactive silicate glasses, originally developed by Hench et al. 40 years ago [4], represent attractive materials for the development of BTE scaffolds due to their proven in vitro and in vivo bioactivity [5]. The application of bioactive glasses in BTE is an expanding research field, with more than 100 papers being published each year (based on a search in Web of Science® using the combined keywords “bioactive glass” and “scaffold”), and the latest innovations in the field have been comprehensively covered in recent review papers [6–8]. Not only the chemical composition of the scaffold material but also the microstructure and 3D morphology of the scaffold, characterized by a highly interconnected pore network, as well as the mechanical competence of the structure and the macroscopic shape determine the suitability of a scaffold for BTE [1–3]. The analysis of the literature reveals that there are still considerable research efforts related to identifying suitable manufacturing methods for BTE scaffolds based
⁎ Corresponding author. Tel.: + 43 1 58801 30857; fax: + 43 1 58801 30895. E-mail address: [email protected] (P. Tesavibul). 0167-577X/$ – see front matter © 2012 Elsevier B.V. All rights reserved. doi:10.1016/j.matlet.2012.01.019
on bioactive glasses exhibiting the required porosity, pore structure, mechanical integrity as well as for obtaining parts with complex shapes and reproducible properties [6–8]. In this context, rapid prototyping methods for bioactive glass scaffolds have started to be investigated, including fused deposition modeling and 3D printing [9,10], direct ink writing [11], solid freeform fabrication (e.g. freeze extrusion) [12], and rapid prototyping based on laser cladding [13]. In the present investigation we have explored for the first time the application of lithography-based additive manufacturing techniques (AMTs), a special additive manufacturing method, to produce Bioglass® based scaffolds. AMTs are a group of manufacturing methods suitable for the fabrication of cellular solids. Especially in cases where high feature resolution and small pore sizes are requested, lithographybased AMTs [14] offer several benefits in comparison with alternative AMTs (selective laser sintering [15], powder-based 3D-printing). For applications in regenerative medicine of hard tissues, ceramic scaffolds with pore sizes between 100 μm and 500 μm are usually required, a size regime that fits well into the capabilities of lithography-based AMTs. For obtaining glass or ceramic parts with lithography-based AMTs it is necessary to process a photopolymer which is filled with large amounts of glass or ceramic particles (typically 40–60 vol% solid loading). Commercially available processes like stereolithography or digital light processing (DLP) can be modified in order to be capable to process such highly filled, viscous photopolymers [16–19]. A recently developed DLP-based process [20] has been used for the first time in this work to fabricate bulk and cellular structures made from 45S5 Bioglass®. The structures were characterized in
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P. Tesavibul et al. / Materials Letters 74 (2012) 81–84
terms of macrostructure visualization and microstructure analysis, and in case of scaffolds, also in terms of mechanical properties. 2. Material and methods 2.1. Fabrication 45S5 Bioglass® powder of particle size in the range 5–30 μm was mixed with acrylate-based monomer, an organic solvent (polypropylene glycol), light absorber and photoinitiator at 43% of solid loading, leading to a photosensitive slurry. Then, the above mentioned system (DLP) was used to solidify the Bioglass® slurry in a layer by layer fashion resulting in free forming the geometry of the Bioglass® “green part” with high resolution, such as 25 μm in layer thickness and 50 μm in the x/y-plane, as illustrated in Fig. 1. With a certain level of light intensity, 0.05 wt% of photoinitiator and 5 s of exposure time, Bioglass® green part samples can be fabricated. After that, a thermal treatment process was applied for removing the solvent, decomposing the polymeric binder and sintering the samples. The program for thermal treatment was developed based on TGA measurement, with a lower heating rate in regions of high weight loss. Finally, the part was sintered for 1 hour at 1000 °C to obtain a partially crystallized Bioglass® product. 2.2. Characterization The viscosity of the slurry was determined by a rheometer (MCR 300 from Anton Paar, Austria). The produced parts were visually inspected and samples are depicted in Fig. 2. The primary characterization carried out was in terms of mechanical properties. Biaxial strength samples (13 mm in diameter and 2 mm thickness) and
Fig. 2. Bioglass® parts fabricated by lithography-based AMT after sintering: (a) cylindrical cellular structure (scaffold) used for compressive strength testing and (b) customized bone implant.
cylindrical cellular structures (9.8 mm in diameter and 11.6 mm height) for compressive strength testing were fabricated. The 3Dmodels of the samples were designed by CAD software (Magics from Materialise, Leuven, Belgium). The biaxial strength test was performed according to the DIN EN ISO 6872 standard. The biaxial and the compressive strength tests were performed with 1 mm/min cross head speed using a universal mechanical testing machine (Zwick-Z050, Germany). The density of the solid sample was measured and compared with that of fully dense 45S5 Bioglass®. 3. Results and discussion
Fig. 1. Digital light processing system for processing highly filled photosensitive slurries: (a) photograph of the device, and (b) schematic setup of the utilized machine.
Typical Bioglass® parts fabricated by the present lithographybased AMT are shown in Fig. 2. A microscopy image of the cylindrical cellular structure for compressive test is indicated in Fig. 2a. The customized Bioglass® component for orthopedic implant in the maxillofacial area, which can be designed and fabricated with accurate shape and dimensions, is shown in Fig. 2b. The characterization results are shown in Table 1. The density of the solid samples were measured using Archimedes's method, and a result of 2.45 g/cm³ was obtained, which corresponds to 91% of the theoretical density of the 45S5 Bioglass® (2.7 g/cm 3) [5]. The SEM images are shown in Fig. 3. Clearly, sintering for 1 hour at 1000 °C has not led to full densification of the material. In previous studies, the sintering of bioactive glass powder has been investigated showing
P. Tesavibul et al. / Materials Letters 74 (2012) 81–84 Table 1 Summary of material properties of 45S5 Bioglass® specimens processed by lithographybased AMT. Density of solid sample (g/cm3) Biaxial strength (MPa) Compressive strength of cellular structure (MPa) Porosity of the cellular structure (%)
2.45 40 0.33 50
that attainment of full densification is impaired by the simultaneous crystallization that occurs at temperature >600 °C [21]. The strength from biaxial testing (see Table 1) is comparable to the flexural strength of traditionally processed Bioglass®, which was reported to be 42 MPa [22]. This result confirms that the sintered structure with a relative density of 91% is sufficiently uniform, e.g. no large voids
83
or defects (microcracks) are present which would detrimentally affect the mechanical strength. As indicated by Fig. 3 the residual micro-porosity originates from small pores which probably are caused by insufficient deagglomeration during the mixing-process of the slurry. The compressive strength of the cellular structure is, however, rather low in comparison with equivalent bioactive glass scaffolds reported in literature [6–8]; hence optimization of the sintering parameters will need to be carried out in following experiments. The viscosity of the Bioglass® slurry used in the present study was measured at 7.3 Pa s which is rather high compared to photosensitive slurries used in conventional lithography-based AMT systems. Nevertheless, by utilizing the modified DLP-process described in Section 2 these slurries can be processed on a routine basis. The ability to utilize such high viscosity slurries allows the process to be applied to fabricate parts from various ceramic and glass powders with sufficiently high solids loading. AMT will facilitate fabrication of parts with patientspecific geometries as well as structures whose cellular architecture (porosity, pore size, pore geometry) has been optimized for providing suitable mechanical properties as well as biological performance tailored for the specific application in BTE. 4. Conclusions It has been shown for the first time that 45S5 Bioglass® powder can be processed using lithography-based additive manufacturing to form 3D parts with predetermined shape and tailored macroscopic and microstructural features. Using the presented AMT it is possible to fabricate Bioglass®-based cellular structures with arbitrary porosity and pore sizes of the order of 500 μm, which is similar to the pore dimensions in trabecular bone. The method offers thus a convenient alternative technology for the design of patient-specific bone implants and scaffold architectures which could be beneficial in BTE and bone replacement strategies, especially considering the highly bioactive behavior and bone bonding ability of Bioglass®. Acknowledgements Financial support by The European Union (FP7 260043 PHOCAM) is gratefully acknowledged. References
Fig. 3. SEM images of biaxial testing specimen in various magnifications: (a) 61, (b) 350, and (c) 1000.
[1] Hutmacher DW, Schantz JT, Lam CXF, Tan KC, Lim TC. State of the art and future directions of scaffold-based bone engineering from a biomaterials perspective. J Tissue Eng Regen Med 2007;1:45–60. [2] Guarino V, Causa F, Ambrosio L. Bioactive scaffolds for bone and ligament tissue. Expert Rev Med Devices 2007;4:405–18. [3] Santos MI, Reis RL. Vascularization in bone tissue engineering: physiology, current strategies, major hurdles and future challenges. Macromol Biosci 2010;10:12–27. [4] Hench LL, Splinter RJ, Allen WC, Greenlee TK. Bonding mechanisms at the interface of ceramic prosthetic materials. J Biomed Mater Res 1971;2:117–41. [5] Chen QZ, Thompson ID, Boccaccini AR. 45S5 Bioglass®-derived glass-ceramic scaffolds for bone tissue engineering. Biomaterials 2006;27:2414–25. [6] Baino F, Vitale-Brovarone C. Three-dimensional glass-derived scaffolds for bone tissue engineering: current trends and forecasts for the future. J Biomed Mater Res A 2011;97A:514–35. [7] Rahaman MN, Day DE, Bal BS, Fu Q, Jung SB, Bonewald LF, et al. Bioactive glass in tissue engineering. Acta Biomater 2011;7:2355–73. [8] Gerhardt LC, Boccaccini AR. Bioactive glass and glass-ceramic scaffolds for bone tissue engineering. Materials 2010;3:3867–910. [9] Wu C, Luo Y, Cuniberti G, Xiao Y, Gelinsky M. Three-dimensional printing of hierarchical and tough mesoporous bioactive glass scaffolds with a controllable pore architecture, excellent mechanical strength and mineralization ability. Acta Biomater 2011;7:2644–50. [10] Mezaros R, Zhao R, Travitzky N, Fey T, Greil P, Wondraczek L. Three-dimensional printing of a bioactive glass. Glass Technol Eur J Glass Sci Technol A 2011;52: 111–6. [11] Fu Q, Saiz E, Tomsia AP. Direct ink writing of highly porous and strong glass scaffolds for load-bearing bone defects repair and regeneration. Acta Biomater 2011;7:3547–54.
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P. Tesavibul et al. / Materials Letters 74 (2012) 81–84
[12] Huang TS, Rahaman MN, Doiphode ND, Leu MC, Bal BS, Day DE, et al. Porous and strong bioactive glass (13–93) scaffolds fabricated by freeze extrusion technique. Mater Sci Eng C 2011;31:1482–9. [13] Comesana R, Lusquinos F, del Val J, Lopez-Alvarez M, Quintero F, Riveiro A, et al. Three-dimensional bioactive glass implants fabricated by rapid prototyping based on CO2 laser cladding. Acta Biomater 2011;7:3476–87. [14] Stampfl J, Liska R. Polymerizable hydrogels for rapid prototyping: chemistry, photolithography, and mechanical properties. In: Bartolo P, editor. Stereolithography. New York: Springer-Verlag; 2011. p. 161–82. [15] Kolan KCR, Leu MC, Hilmas GE, Brown RF, Velez M. Fabrication of 13–93 bioactive glass scaffolds for bone tissue engineering using indirect selective laser sintering. Biofabrication 2011;3:025004. [16] Stampfl J, Liu HC, Nam SW, Sakamoto K, Tsuru H, Kang S, et al. Rapid prototyping and manufacturing by gelcasting of metallic and ceramic slurries. Mater Sci Eng A 2002;334:187–92. [17] Dufaud O, Marchal P, Corbel S. Rheological properties of PZT suspensions for stereolithography. J Eur Ceram Soc 2002;22:2081–92.
[18] Halloran JW, Tomeckova V, Gentry S, Das S, Cilino P, Yuan D, et al. Photopolymerization of powder suspensions for shaping ceramics. J Eur Ceram Soc 2011;31: 2613–9. [19] Chu TG, Orton DG, Hollister SJ, Feinberg SE, Halloran JW. Mechanical and in vivo performance of hydroxyapatite implants with controlled architectures. Biomaterials 2002;23:1283–93. [20] Liska R, Patzer J, Stampfl J, Wachter W, Appert C, Technische Universität Wien. Device and method for processing light-polymerizable material for building up an object in layers. WO 2010/045951 A1; 2010. [21] Bretcanu O, Chatzistavrou X, Paraskevopoulos K, Conradt R, Thompson I, Boccaccini AR. Sintering and crystallisation of 45S5 Bioglass® powder. J Eur Ceram Soc 2009;29:3299–306. [22] Hench LL, Kokubo T. Properties of bioactive glasses and glass-ceramics. In: Black J, Hastings G, editors. Handbook of biomaterial properties. London: Chapman & Hall; 1998. p. 355–63.
Contents lists available at SciVerse ScienceDirect
Materials Letters journal homepage: www.elsevier.com/locate/matlet
Processing of 45S5 Bioglass® by lithography-based additive manufacturing Passakorn Tesavibul a,⁎, Ruth Felzmann a, Simon Gruber a, Robert Liska b, Ian Thompson c, Aldo R. Boccaccini d, Jürgen Stampfl a a
Institute of Materials Science and Technology, Vienna University of Technology, Favoritenstraße 9-11/E308, A-1040 Vienna, Austria Institute of Applied Synthetic Chemistry, Vienna University of Technology, Getreidemarkt 9/E163, 1060 Vienna, Austria Dental Institute, Biomaterials Unit, King's College London, London SE1 9RT, UK d Institute of Biomaterials, Department of Materials Science and Engineering, University of Erlangen-Nuremberg, Cauerstr. 6, 91058 Erlangen, Germany b c
a r t i c l e
i n f o
Article history: Received 5 October 2011 Accepted 5 January 2012 Available online 12 January 2012 Keywords: Biomaterials Biomimetic Porous materials Structural
a b s t r a c t Lithography-based Additive Manufacturing Technologies (AMTs) were used for fabricating cellular structures made of 45S5 Bioglass®. Using AMTs it is possible to design and fabricate cellular structures with a resolution of around 40 μm and wall thicknesses down to 200 μm. The presented process relies on selectively polymerizing a photosensitive, ceramic-filled resin with a dynamic mask. The dynamic mask is based on a digital mirror array which projects blue light (light emitting diodes with a wavelength of 460 nm) onto the resin. The mechanical properties of sintered bulk samples (biaxial strength) and cylindrical cellular structures (compressive strength) were determined. The biaxial strength of the manufactured samples was 40 MPa, and the compressive strength of the cellular structure was 0.33 MPa, which is slightly lower than the strength of porous Bioglass® structures made by the foam replica method. Lithography-based AMT offers an excellent alternative to existing bone implant and scaffold fabrication methods providing accurate control of 3D morphology and pore architecture. © 2012 Elsevier B.V. All rights reserved.
1. Introduction Bone tissue engineering (BTE) requires scaffolds (3D porous structures) fabricated with materials which exhibit high surface reactivity in physiological fluids leading to the formation of strong bonds to bone tissue [1,2]. These scaffolds must exhibit high and interconnected porosity, and in combination with relevant cells and signaling molecules, should promote the regeneration of new vascularized bone tissue [2,3]. Bioactive silicate glasses, originally developed by Hench et al. 40 years ago [4], represent attractive materials for the development of BTE scaffolds due to their proven in vitro and in vivo bioactivity [5]. The application of bioactive glasses in BTE is an expanding research field, with more than 100 papers being published each year (based on a search in Web of Science® using the combined keywords “bioactive glass” and “scaffold”), and the latest innovations in the field have been comprehensively covered in recent review papers [6–8]. Not only the chemical composition of the scaffold material but also the microstructure and 3D morphology of the scaffold, characterized by a highly interconnected pore network, as well as the mechanical competence of the structure and the macroscopic shape determine the suitability of a scaffold for BTE [1–3]. The analysis of the literature reveals that there are still considerable research efforts related to identifying suitable manufacturing methods for BTE scaffolds based
⁎ Corresponding author. Tel.: + 43 1 58801 30857; fax: + 43 1 58801 30895. E-mail address: [email protected] (P. Tesavibul). 0167-577X/$ – see front matter © 2012 Elsevier B.V. All rights reserved. doi:10.1016/j.matlet.2012.01.019
on bioactive glasses exhibiting the required porosity, pore structure, mechanical integrity as well as for obtaining parts with complex shapes and reproducible properties [6–8]. In this context, rapid prototyping methods for bioactive glass scaffolds have started to be investigated, including fused deposition modeling and 3D printing [9,10], direct ink writing [11], solid freeform fabrication (e.g. freeze extrusion) [12], and rapid prototyping based on laser cladding [13]. In the present investigation we have explored for the first time the application of lithography-based additive manufacturing techniques (AMTs), a special additive manufacturing method, to produce Bioglass® based scaffolds. AMTs are a group of manufacturing methods suitable for the fabrication of cellular solids. Especially in cases where high feature resolution and small pore sizes are requested, lithographybased AMTs [14] offer several benefits in comparison with alternative AMTs (selective laser sintering [15], powder-based 3D-printing). For applications in regenerative medicine of hard tissues, ceramic scaffolds with pore sizes between 100 μm and 500 μm are usually required, a size regime that fits well into the capabilities of lithography-based AMTs. For obtaining glass or ceramic parts with lithography-based AMTs it is necessary to process a photopolymer which is filled with large amounts of glass or ceramic particles (typically 40–60 vol% solid loading). Commercially available processes like stereolithography or digital light processing (DLP) can be modified in order to be capable to process such highly filled, viscous photopolymers [16–19]. A recently developed DLP-based process [20] has been used for the first time in this work to fabricate bulk and cellular structures made from 45S5 Bioglass®. The structures were characterized in
82
P. Tesavibul et al. / Materials Letters 74 (2012) 81–84
terms of macrostructure visualization and microstructure analysis, and in case of scaffolds, also in terms of mechanical properties. 2. Material and methods 2.1. Fabrication 45S5 Bioglass® powder of particle size in the range 5–30 μm was mixed with acrylate-based monomer, an organic solvent (polypropylene glycol), light absorber and photoinitiator at 43% of solid loading, leading to a photosensitive slurry. Then, the above mentioned system (DLP) was used to solidify the Bioglass® slurry in a layer by layer fashion resulting in free forming the geometry of the Bioglass® “green part” with high resolution, such as 25 μm in layer thickness and 50 μm in the x/y-plane, as illustrated in Fig. 1. With a certain level of light intensity, 0.05 wt% of photoinitiator and 5 s of exposure time, Bioglass® green part samples can be fabricated. After that, a thermal treatment process was applied for removing the solvent, decomposing the polymeric binder and sintering the samples. The program for thermal treatment was developed based on TGA measurement, with a lower heating rate in regions of high weight loss. Finally, the part was sintered for 1 hour at 1000 °C to obtain a partially crystallized Bioglass® product. 2.2. Characterization The viscosity of the slurry was determined by a rheometer (MCR 300 from Anton Paar, Austria). The produced parts were visually inspected and samples are depicted in Fig. 2. The primary characterization carried out was in terms of mechanical properties. Biaxial strength samples (13 mm in diameter and 2 mm thickness) and
Fig. 2. Bioglass® parts fabricated by lithography-based AMT after sintering: (a) cylindrical cellular structure (scaffold) used for compressive strength testing and (b) customized bone implant.
cylindrical cellular structures (9.8 mm in diameter and 11.6 mm height) for compressive strength testing were fabricated. The 3Dmodels of the samples were designed by CAD software (Magics from Materialise, Leuven, Belgium). The biaxial strength test was performed according to the DIN EN ISO 6872 standard. The biaxial and the compressive strength tests were performed with 1 mm/min cross head speed using a universal mechanical testing machine (Zwick-Z050, Germany). The density of the solid sample was measured and compared with that of fully dense 45S5 Bioglass®. 3. Results and discussion
Fig. 1. Digital light processing system for processing highly filled photosensitive slurries: (a) photograph of the device, and (b) schematic setup of the utilized machine.
Typical Bioglass® parts fabricated by the present lithographybased AMT are shown in Fig. 2. A microscopy image of the cylindrical cellular structure for compressive test is indicated in Fig. 2a. The customized Bioglass® component for orthopedic implant in the maxillofacial area, which can be designed and fabricated with accurate shape and dimensions, is shown in Fig. 2b. The characterization results are shown in Table 1. The density of the solid samples were measured using Archimedes's method, and a result of 2.45 g/cm³ was obtained, which corresponds to 91% of the theoretical density of the 45S5 Bioglass® (2.7 g/cm 3) [5]. The SEM images are shown in Fig. 3. Clearly, sintering for 1 hour at 1000 °C has not led to full densification of the material. In previous studies, the sintering of bioactive glass powder has been investigated showing
P. Tesavibul et al. / Materials Letters 74 (2012) 81–84 Table 1 Summary of material properties of 45S5 Bioglass® specimens processed by lithographybased AMT. Density of solid sample (g/cm3) Biaxial strength (MPa) Compressive strength of cellular structure (MPa) Porosity of the cellular structure (%)
2.45 40 0.33 50
that attainment of full densification is impaired by the simultaneous crystallization that occurs at temperature >600 °C [21]. The strength from biaxial testing (see Table 1) is comparable to the flexural strength of traditionally processed Bioglass®, which was reported to be 42 MPa [22]. This result confirms that the sintered structure with a relative density of 91% is sufficiently uniform, e.g. no large voids
83
or defects (microcracks) are present which would detrimentally affect the mechanical strength. As indicated by Fig. 3 the residual micro-porosity originates from small pores which probably are caused by insufficient deagglomeration during the mixing-process of the slurry. The compressive strength of the cellular structure is, however, rather low in comparison with equivalent bioactive glass scaffolds reported in literature [6–8]; hence optimization of the sintering parameters will need to be carried out in following experiments. The viscosity of the Bioglass® slurry used in the present study was measured at 7.3 Pa s which is rather high compared to photosensitive slurries used in conventional lithography-based AMT systems. Nevertheless, by utilizing the modified DLP-process described in Section 2 these slurries can be processed on a routine basis. The ability to utilize such high viscosity slurries allows the process to be applied to fabricate parts from various ceramic and glass powders with sufficiently high solids loading. AMT will facilitate fabrication of parts with patientspecific geometries as well as structures whose cellular architecture (porosity, pore size, pore geometry) has been optimized for providing suitable mechanical properties as well as biological performance tailored for the specific application in BTE. 4. Conclusions It has been shown for the first time that 45S5 Bioglass® powder can be processed using lithography-based additive manufacturing to form 3D parts with predetermined shape and tailored macroscopic and microstructural features. Using the presented AMT it is possible to fabricate Bioglass®-based cellular structures with arbitrary porosity and pore sizes of the order of 500 μm, which is similar to the pore dimensions in trabecular bone. The method offers thus a convenient alternative technology for the design of patient-specific bone implants and scaffold architectures which could be beneficial in BTE and bone replacement strategies, especially considering the highly bioactive behavior and bone bonding ability of Bioglass®. Acknowledgements Financial support by The European Union (FP7 260043 PHOCAM) is gratefully acknowledged. References
Fig. 3. SEM images of biaxial testing specimen in various magnifications: (a) 61, (b) 350, and (c) 1000.
[1] Hutmacher DW, Schantz JT, Lam CXF, Tan KC, Lim TC. State of the art and future directions of scaffold-based bone engineering from a biomaterials perspective. J Tissue Eng Regen Med 2007;1:45–60. [2] Guarino V, Causa F, Ambrosio L. Bioactive scaffolds for bone and ligament tissue. Expert Rev Med Devices 2007;4:405–18. [3] Santos MI, Reis RL. Vascularization in bone tissue engineering: physiology, current strategies, major hurdles and future challenges. Macromol Biosci 2010;10:12–27. [4] Hench LL, Splinter RJ, Allen WC, Greenlee TK. Bonding mechanisms at the interface of ceramic prosthetic materials. J Biomed Mater Res 1971;2:117–41. [5] Chen QZ, Thompson ID, Boccaccini AR. 45S5 Bioglass®-derived glass-ceramic scaffolds for bone tissue engineering. Biomaterials 2006;27:2414–25. [6] Baino F, Vitale-Brovarone C. Three-dimensional glass-derived scaffolds for bone tissue engineering: current trends and forecasts for the future. J Biomed Mater Res A 2011;97A:514–35. [7] Rahaman MN, Day DE, Bal BS, Fu Q, Jung SB, Bonewald LF, et al. Bioactive glass in tissue engineering. Acta Biomater 2011;7:2355–73. [8] Gerhardt LC, Boccaccini AR. Bioactive glass and glass-ceramic scaffolds for bone tissue engineering. Materials 2010;3:3867–910. [9] Wu C, Luo Y, Cuniberti G, Xiao Y, Gelinsky M. Three-dimensional printing of hierarchical and tough mesoporous bioactive glass scaffolds with a controllable pore architecture, excellent mechanical strength and mineralization ability. Acta Biomater 2011;7:2644–50. [10] Mezaros R, Zhao R, Travitzky N, Fey T, Greil P, Wondraczek L. Three-dimensional printing of a bioactive glass. Glass Technol Eur J Glass Sci Technol A 2011;52: 111–6. [11] Fu Q, Saiz E, Tomsia AP. Direct ink writing of highly porous and strong glass scaffolds for load-bearing bone defects repair and regeneration. Acta Biomater 2011;7:3547–54.
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P. Tesavibul et al. / Materials Letters 74 (2012) 81–84
[12] Huang TS, Rahaman MN, Doiphode ND, Leu MC, Bal BS, Day DE, et al. Porous and strong bioactive glass (13–93) scaffolds fabricated by freeze extrusion technique. Mater Sci Eng C 2011;31:1482–9. [13] Comesana R, Lusquinos F, del Val J, Lopez-Alvarez M, Quintero F, Riveiro A, et al. Three-dimensional bioactive glass implants fabricated by rapid prototyping based on CO2 laser cladding. Acta Biomater 2011;7:3476–87. [14] Stampfl J, Liska R. Polymerizable hydrogels for rapid prototyping: chemistry, photolithography, and mechanical properties. In: Bartolo P, editor. Stereolithography. New York: Springer-Verlag; 2011. p. 161–82. [15] Kolan KCR, Leu MC, Hilmas GE, Brown RF, Velez M. Fabrication of 13–93 bioactive glass scaffolds for bone tissue engineering using indirect selective laser sintering. Biofabrication 2011;3:025004. [16] Stampfl J, Liu HC, Nam SW, Sakamoto K, Tsuru H, Kang S, et al. Rapid prototyping and manufacturing by gelcasting of metallic and ceramic slurries. Mater Sci Eng A 2002;334:187–92. [17] Dufaud O, Marchal P, Corbel S. Rheological properties of PZT suspensions for stereolithography. J Eur Ceram Soc 2002;22:2081–92.
[18] Halloran JW, Tomeckova V, Gentry S, Das S, Cilino P, Yuan D, et al. Photopolymerization of powder suspensions for shaping ceramics. J Eur Ceram Soc 2011;31: 2613–9. [19] Chu TG, Orton DG, Hollister SJ, Feinberg SE, Halloran JW. Mechanical and in vivo performance of hydroxyapatite implants with controlled architectures. Biomaterials 2002;23:1283–93. [20] Liska R, Patzer J, Stampfl J, Wachter W, Appert C, Technische Universität Wien. Device and method for processing light-polymerizable material for building up an object in layers. WO 2010/045951 A1; 2010. [21] Bretcanu O, Chatzistavrou X, Paraskevopoulos K, Conradt R, Thompson I, Boccaccini AR. Sintering and crystallisation of 45S5 Bioglass® powder. J Eur Ceram Soc 2009;29:3299–306. [22] Hench LL, Kokubo T. Properties of bioactive glasses and glass-ceramics. In: Black J, Hastings G, editors. Handbook of biomaterial properties. London: Chapman & Hall; 1998. p. 355–63.