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This study proposes self-assembly-induced 3D plotting as an innovative solid freeform fabrication (SFF) technique for the production of macro/nano-porous collagen scaffolds, particularly comprised of nanofibrous collagen filaments. In this technique, collagen filaments deposited in a coagulation bath could be effectively gelled through the self-assembly of collagen molecules into fibrils, accordingly, enabling the 3-dimensional deposition of collagen filaments with a collagen nanofiber network. The unique macro/nano-structure could be structurally stabilized by dehydration process coupled with chemical cross-linking. The porous collagen scaffolds produced had 3-dimensionally interconnected macropores (~ 451×305 μm in pore width) separated by nanoprous collagen filaments. In addition, the macro/nano-porous collagen scaffolds showed the tensile strength of~353 kPa and compressive strength of~31 kPa at a porosity of~95 vol% and excellent in vitro biocompatibility, assessed using pre-osteoblast MC3T3-E1 cells.

Highly porous gelatin–silica hybrid scaffolds with high porosity, large pores and large interconnections, as well as tailored surface textures were produced using a newly developed direct foaming/freezing. Two different types of precursors as the silica source, 3-glycidoxyproyltrimethoxysilane (denoted as “GS”) and sol–gel derived silica (denoted as “SS”), were used for producing the porous GLA–GS and GLA–GS–SS hybrid scaffolds. In this method, air bubbles could be vigorously incorporated into the GLA–GS and GLA–GS–SS mixtures and then stabilized by rapid freezing of the foamed mixtures at −70 °C. Both the porous GLA–GS and GLA–GS–SS hybrid scaffolds produced herein had a highly porous structure (porosity > 90 vol%, pore size = 200–500 μm, interconnection size = 100–200 μm) with a uniform distribution of the silica phase in the gelatin matrix. In addition, surface textures with a rugged morphology could be created after immersion of the porous GLA–GS and GLA–GS–SS hybrid scaffolds in ethanol at −20 °C for 24 h. The porous GLA–GS and GLA–GS–SS hybrid scaffolds showed much higher mechanical properties than the porous GLA scaffold, while preserving excellent in vitro biocompatibility, demonstrating potential application as the bone scaffold.

This study demonstrates the utility of nonsolvent induced phase separation (NIPS)-based 3D plotting as a novel SFF technique for the production of 3-dimensionally macrochanneled poly( e -caprolactone) (PCL) scaffolds with highly porous PCL frameworks. In particular, a PCL/tetrahydrofuran (THF) solution was deposited in an EtOH bath to rapidly solidify PCL filaments with a highly porous structure through exchange of THF solvent and EtOH nonsolvent. All the scaffolds produced with various PCL concentrations (14 wt%, 18 wt%, and 22 wt%) showed well-constructed 3-D macrochannels with highly porous PCL frameworks. However, the mechanical properties of the scaffolds, measured by compressive and tensile strength tests, increased with an increase in PCL concentration owing to a decrease in the overall porosity.

This study reports the utility of tantalum (Ta) coating for improving the surface hardness, in vitro bioactivity and biocompatibility of Co–Cr implants. The use of direct current sputtering allowed for the deposition of a dense and uniform Ta film onto a Co–Cr substrate, which was composed of β-phase Ta grains. This hard Ta coating significantly improved the surface hardness of the Co–Cr by a factor of > 2.3. In addition, the Ta-deposited Co–Cr substrate showed a vigorous precipitation of apatite crystals on its surface after 4 weeks of immersion in simulated body fluid, suggesting its excellent in vitro bioactivity. This bioactive Ta coating led to a considerable improvement in the in vitro biocompatibility of the Co–Cr, which was assessed in terms of the attachment, proliferation and differentiation of pre-osteoblasts (MC3T3-E1).

This study investigated the effect of the addition of sol–gel derived nanoscale bioactive glass (NBG) particles on the mechanical properties and biological performances of PCL polymer, in order to evaluate the potential applications of PCL/NBG composites for bone tissue regeneration. Regardless of the NBG contents (10, 20, and 30 wt.%), the NBG particles, which were synthesized through the sol–gel process using polyethylene glycol (PEG) polymer as a template, could be uniformly dispersed in the PCL matrix, while generating pores in the PCL/NBG composites. The elastic modulus of the PCL/NBG composites increased remarkably from 89 ± 11 MPa to 383 ± 50 MPa with increasing NBG content from 0 to 30 wt.%, while still showing good ultimate tensile strength in the range of 15–19 MPa. The hydrophilicity, water absorption and degradation behavior of the PCL/NBG composites were also enhanced by the addition of the NBG particles. Furthermore, the PCL/NBG composite with a NBG content of 30 wt.% showed significantly enhanced in vitro bioactivity and cellular response compared to those of the pure PCL.

This study reports a novel way of increasing the pore size of highly aligned porous alumina ceramics by heat-treating an extruded alumina/camphene body at a temperature near its solidification point. The pore size obtained increased remarkably from 51 ± 8 to 125 ± 27 μm with increasing heat-treatment time from 1 to 24 h, due to the continuative overgrowth of the camphene dendrites during heat-treatment, while a highly aligned porous structure was preserved. In addition, interestingly, this heat-treatment enabled alumina walls to be densified quite well, whereas porous walls were observed in the sample produced without heat-treatment, which led to a considerable increase in compressive strength. The sample produced with a heat-treatment time of 12 h showed a high compressive strength of 11.6 ± 1.2 MPa at a porosity of approximately 84 vol%, which was much higher than that (0.28 ± 0.1 MPa) of the sample produced without heat-treatment.

This study reports a new way of enhancing the compressive strength of porous calcium phosphate (CaP) ceramics by creating highly elongated pores. These elongated pores were produced by casting a CaP/camphene slurry into stretched polymeric sponges with a thick carbon coating layer used as a template. The sample produced after sintering at 1250 °C for 3 h showed a highly elongated porous structure with a porosity of 38 ± 1.2 vol%, where elongated pores with a size of 512 ± 96 μm were formed as a replica of the template. In addition, CaP walls with a thickness of 841 ± 239 μm were fully densified without any noticeable defects due to the high CaP content of 40 vol% in the CaP/camphene slurry. The compressive strength of the sample was as high as 21 ± 4.9 MPa when tested parallel to the direction of pore elongation, which is much higher than that (12 ± 2.4 MPa) of the sample tested normal to the direction of pore elongation. The sample also showed good biocompatibility, as assessed by the in vitro cell test using a pre-osteoblast cell line.

We herein propose a new technique for producing highly aligned porous ceramics by extruding a frozen ceramic/camphene body. To accomplish this, an alumina/camphene slurry with an initial alumina content of 10 vol% was first frozen unidirectionally in a 20 mm × 20 mm mold and extruded through a reduction die with a cross-section of 5 mm × 5 mm at room-temperature. This simple process enabled the formation of porous alumina ceramics with highly aligned pores as a replica of the camphene dendrites with a preferential orientation parallel to the extrusion direction. The sample showed much higher compressive strength of 280 ± 80 kPa with a porosity of 83 vol% when tested parallel to the direction of pore alignment. In addition, these materials could be used as a valuable framework for the production of ceramic/epoxy composites, particularly with a lamellar structure, which would result in a remarkable increase in mechanical properties.

This paper proposes a novel, simple way to improve the compressive strength of reticulated porous hydroxyapatite (HA) ceramics using carbon-coated polymeric sponges with elongated pores as a novel template. This template allowed samples to have two interconnected pore networks with a preferential orientation, in which an addition pore network was newly formed by removing the carbon-coated polymeric struts, while preserving the pre-existing pore network. The compressive strength of the sample was as high as 2.9 ± 0.3 MPa with a porosity of 76% when tested parallel to the direction of pore elongation. In addition, the in vitro cell test using a pre-osteoblast cell line revealed the samples to have good biocompatibility.

This paper reports a novel way of synthesizing porous poly(e-caprolactone) (PCL)/silica hybrid membranes with a patterned surface pores by casting a mixture containing a PCL solution and sol–gel derived silica sol at room temperature. When the initial TEOS content in relation to the PCL content in the mixture was ≥ 20 vol.%, a highly porous structure containing patterned surface pores, ~ 40–70 μm in size, was formed successfully. The silica phase was hybridized uniformly with the PCL polymer without any noticeable phase separation, as confirmed by energy dispersive X-ray spectroscopy (EDS). The porosity increased from 4.5 to 39.2 vol.% with increasing initial TEOS content from 0 to 40 vol.%. However, the hybrid membranes prepared at an initial TEOS content of ≥ 20 vol.% showed a reasonably high tensile strength and elastic modulus, ranging from 7.6 to 5.0 MPa and 79 to 51 MPa, respectively.

This paper proposes a novel way of producing aligned porous alumina ceramics with larger dimensions by assembling unidirectionally frozen alumina/camphene bodies, particularly those containing polystyrene (PS) polymer as the binder. The compressive strength of the samples sintered at 1450 °C for 3 h increased remarkably from 2 ± 0.1 to 16 ± 2 MPa with increasing PS content from 5 to 20 vol.% due to the prevention of cracks generally caused by drying shrinkage. In addition, frozen samples with a PS content of 20 vol.% could be assembled into larger dimensions without difficulty. The height of the assembled sample produced with a lamination number of 5 could be increased to ∼24 mm without a severe decrease in compressive strength (16 ± 3 MPa at a porosity of ∼79 vol.%) due to the maintenance of an aligned porous structure with good interfacial bonding between the laminations.

A novel type of porous hydroxyapatite (HA) scaffolds with a functionally graded core/shell structure was fabricated by freeze casting HA/camphene slurries with various HA contents into fugitive molds containing a graphite template with three-dimensionally interconnected pores for the creation of a highly porous core. All the fabricated samples had functionally graded core/shell structures with 3-D periodic pore networks in a core surrounded by a relatively dense shell. The overall porosity of the sample decreased from 60 to 38 vol% with increasing HA content in the HA/camphene slurry from 20 to 36 vol% due to a decrease in porosity in both the core and shell regions. In addition, the compressive strength was improved remarkably from 12 ± 1.1 to 32 ± 3.0 MPa. The in vitro cell test using a pre-osteoblast cell line showed that the samples had good biocompatibility.

This paper reports a novel way of improving the mechanical properties and biocompatibility of porous Ti scaffolds using a combination of the modified sponge replication method and anodization process. The use of a stretched polymeric sponge as a novel template allowed the creation of elongated pores in a porous Ti scaffold, which, accordingly, led to a high compressive strength of 24.2 ± 2.08 MPa at a porosity of approximately 70 vol%. Furthermore, the surfaces of the Ti walls were coated successfully with a bioactive nanoporous TiO2 layer using the anodization process, which enhanced the biocompatibility remarkably, as assessed by the attachment of MC3T3-E1 cells.

This study reports a novel way of directly coating a poly(e-caprolactone) (PCL) nanofibrous scaffold with bioactive sol–gel derived silica by directly co-electrospinning (Co-ES) a PCL solution and silica sol, used as the core and shell materials, respectively. In particular, the silica sols prepared using a sol–gel process at room temperature were heat-treated at 60 °C for various times, ranging from 0 to 9 h, in order to improve their spinability. The surface of the individual PCL nanofibers could be covered completely with a bioactive silica layer using a silica sol heat-treated at 60 °C for more than 6 h, whilst preserving the nanofibrous structure. Fourier-transform infrared spectroscopy (FT-IR) revealed only the characteristic bands associated with the PCL and sol–gel derived silica materials without any noticeable band shift.

This paper demonstrates the utility of an electrodeposition technique to deposit a layer of biodegradable sol–gel derived silica on a Ti substrate coated with a nanoporous TiO 2 layer in a controlled manner. The deposition pattern of the silica phase was tailored by controlling the silica sol content in the diluted solution and the deposition time. This allowed the nanopores to be filled with the silica phase, confirmed by energy dispersive spectroscopy and Fourier-transform infrared spectroscopy, whilst preserving the nanoporous surface, particularly when electrodeposition was carried out in a dilute solution with a silica sol content of 30 vol.% for

This study reports a simple way of improving the compressive strength of highly porous hydroxyapatite (HA) scaffolds by adopting elongated polymeric sponges as a novel template. In this method, as-received polymeric sponges with isotropic pores were stretched uniaxially to 50% elongation at 200 °C for 2 h, and then coated with a HA slurry. The HA-coated sponges were heat-treated at 800 °C for 3 h to remove the polymeric sponges and at 1250 °C for 3 h to sinter the HA walls. The fabricated samples showed a highly anisotropic pore structure with elongated pores parallel to the direction of the elongation of the polymeric sponge. This simple method allowed a highly porous scaffold to have a high compressive strength of 3.8 ± 0.1 MPa at a porosity of 76% when tested parallel to the direction of pore elongation.

This paper reports a novel type of porous titanium (Ti) scaffolds with two interlaced periodic pores that were produced by coating the surfaces of a dual-channeled hydroxyapatite (HA) scaffold, as a supporting framework, with a titanium hydride (TiH 2 ) slurry followed by heat-treatment at 1200 °C for 3 h in a vacuum to convert TiH 2 to Ti metal. This method allowed the porous Ti scaffolds to mimic the original pore structure of the dual-channeled HA scaffold in a tightly controlled manner. It was observed that the Ti layer was strongly adhered to the HA layer, owing to the diffusion of P ions into the Ti layer. The fabricated sample showed a high compressive strength of 6.0 ± 0.77 MPa and a porosity of 78 vol.% due to its unique pore structure, as well as perfect interconnections between the pores.