Hollow Filaments Research Articles

A novel printing strategy to fabricate polyetheretherketone (PEEK)-based composites via hollow filaments filled with multiple reinforcements

ABSTRACT Polyetheretherketone (PEEK)-based composites fabricated by material extrusion (ME) have attracted broad research attention; however, the complex pre-made composite filament process makes them inflexible. In this work, a novel composite printing strategy was proposed by filling composite powder into hollow filaments to construct composite filaments for printing. This strategy eliminated the screw extrusion composite filament process and fabricated composite parts directly using composite powders. Hydroxyapatite-reinforced polyetheretherketone (HA-PEEK) and carbon fibre-reinforced polyetheretherketone (CF-PEEK) composite specimens were fabricated based on the proposed printing method, and their chemical, physical, and mechanical properties were investigated. To improve the mechanical performance of the specimens, annealing was conducted. It was found that the printed composite specimens had excellent mechanical properties. The highest flexural strengths of the 10% HA-PEEK-R and 5% CF-PEEK-R specimens were detected as 352.9 and 399.4 MPa, respectively. The compression strengths of the 10% HA-PEEK-R and 20% CF-PEEK-R specimens peaked, representing 123.0 and 137.2 MPa, respectively. Furthermore, adding different functional reinforcement fillers or various filler contents to different segments of hollow filaments, sandwich structures and gradient structures were successfully fabricated.

Hollow Filaments from Coaxial Dry-Jet Wet Spinning of a Cellulose Solution in an Ionic Liquid: Wet-Strength and Water Interactions.

Hollow tubing and tubular filaments are highly relevant to membrane technologies, vascular tissue engineering, and others. In this context, we introduce hollow filaments (HF) produced through coaxial dry-jet wet spinning of cellulose dissolved in an ionic liquid ([emim][OAc]). The HF, developed upon regeneration in water (23 °C), displays superior mechanical performance (168 MPa stiffness and 60% stretchability) compared to biobased counterparts, such as those based on collagen. The results are rationalized by the effects of crystallinity, polymer orientation, and other factors associated with rheology, thermal stability, and dynamic vapor sorption. The tensile strength and strain of the HF (dry and wet) are enhanced by drying and wetting cycles (water vapor sorption and desorption experiments). Overall, we unveil the role of water molecules in the wet performance of HF produced by cellulose regeneration from [emim][OAc], which offers a basis for selecting suitable applications.

3D coaxial printing of porous construct stacked with hollow filaments for heavy metal removal

Biopolymers-based hydrogels/aerogels have been widely used for removing heavy metals from water. However, the adsorption efficiency is limited by the monolithic macroscopic structure due to low exposed adsorption sites and ion diffusion rate. In this study, we report a proof-of-concept micro-extrusion-based 3D coaxial printing technology to solve the aforementioned problems in heavy metal removal. The 3D printed grid-like architectures stacked with hollow filaments prepared by alginate and cellulose nanocrystal showed excellent heavy metals (including Cu, Zn, Cr, and Cd) removal performance over other common adsorbents. The Cu(II) adsorption was greatly influenced by the initial pH and ionic strength. It followed pseudo-second order kinetics and Langmuir isotherms models. The maximum adsorption capacity of the porous construct was found to be 97.22 mg∙g−1 at room temperature. Moreover, the equilibrium adsorption capacity and adsorption rate of Cu(II) in the hierarchical porous adsorbents (~68 mg∙g−1, 2.29×10−3 g∙mg−1∙min−1) were much higher than that in its corresponding solid chunk hydrogel (~48 mg∙g−1, 7.27×10−4 g∙mg−1∙min−1). It exemplifies that the 3D coaxial printing strategy for wastewater treatment enables shape-specific applications of functional hierarchical porous adsorbents.

Composite filament with super high effective thermal conductivity

The low thermal conductivity of the clothing filament constrains the efficiency of the thermal management garments. In this paper, a super thermal conductive composite filament (STCCF) was proposed for body thermal management, which was fabricated by hollow Teflon filaments incorporated with hollow copper filaments in the heating and cooling sections. By introducing R134a into the hollow filament, a thermally driven flow was generated due to the pressure imbalance caused by the evaporation and condensation of R134a, which enhanced the heat transport capability significantly. The apparent thermal conductivity of the STCCF increased with the increasing heat power, being up to 5042 W/(m·K) at the heating temperature of 49 °C. Furthermore, bending only had a small effect on the thermal performance of STCCF due to the flow pattern transition in the curved section. Moreover, the heat transfer capacity could be enhanced by a lower temperature difference between the hot and cool sections under constant heat power. Therefore, the proposed STCCF has great potential for human body thermal management, which could contribute to human health and thermal comfort as well as building energy saving.

Self-Assembly of Soot Nanoparticles on the Surface of Resistively Heated Carbon Microtubes in Near-Hexagonal Arrays of Micropyramids.

Almost regular hexagonal arrays of microscopic pyramids consisting of soot nanoparticles are formed on the surface of graphitized hollow filaments, which are resistively heated to ∼1800-2400 °C under an Ar atmosphere containing trace amounts of oxygen (∼300 ppm). At higher temperatures (T > 2300 °C, approximately) the soot particles are represented mainly by multishell carbon nano-onions. The height and width of the pyramids are strongly dependent on the temperature of the resistive heating, diminishing from 5 to 10 μm at T ≈ 1800 °C to ∼1 μm at 2300-2400 °C. Quasi-hexagonal arrays of the micropyramids are organized in the convex "craters" on the surface of the microtubes, which grow with the time of the thermal treatment. The pyramids always point normally to the surface of the craters, except at the boundaries between the craters, where the normal direction is not well-defined. The pyramids are soft and can be easily destroyed by touching them but can be hardened by heating them under an oxygen-free atmosphere. The pyramids are observed only on the exterior surface of the microtubes, not on their inner surface. This suggests that the thermophoretic force generated by a strong temperature gradient near the external surface of the tubes may be the cause of the micropyramid formation. Electrostatic charging of the soot nanoparticles due to thermionic emission may also be relevant to this phenomenon. The micropyramids can function as field emission point sources, as demonstrated with the use of a micronanoprobing station, mounted in a scanning electron microscope.

Active entanglement enables stochastic, topological grasping

Grasping, in both biological and engineered mechanisms, can be highly sensitive to the gripper and object morphology, as well as perception and motion planning. Here, we circumvent the need for feedback or precise planning by using an array of fluidically actuated slender hollow elastomeric filaments to actively entangle with objects that vary in geometric and topological complexity. The resulting stochastic interactions enable a unique soft and conformable grasping strategy across a range of target objects that vary in size, weight, and shape. We experimentally evaluate the grasping performance of our strategy and use a computational framework for the collective mechanics of flexible filaments in contact with complex objects to explain our findings. Overall, our study highlights how active collective entanglement of a filament array via an uncontrolled, spatially distributed scheme provides options for soft, adaptable grasping.

Human endothelial cells form an endothelium in freestanding collagen hollow filaments fabricated by direct extrusion printing

Fiber-shaped materials have great potential for tissue engineering applications as they provide structural support and spatial patterns within a three-dimensional construct. Here we demonstrate the fabrication of mechanically stable, meter-long collagen hollow filaments by a direct extrusion printing process. The fibres are permeable for oxygen and proteins and allow cultivation of primary human endothelial cells (ECs) at the inner surface under perfused conditions. The cells show typical characteristics of a well-organized EC lining including VE-cadherin expression, cellular response to flow and ECM production. The results demonstrate that the collagen tubes are capable of creating robust soft tissue filaments. The mechanical properties and the biofunctionality of these collagen hollow filaments facilitate the engineering of prevascularised tissue engineering constructs.

Physical properties enhancement of carbon fiber obtained from isotropic pitch doped by ultra-long carbon nanotubes

• DWCNT-doped isotropic petroleum pitch used successfully for carbon fiber formation • DWCNT doping leads to jump in both thermal and electrical conductivity of fibers • Inner cavities appear in the fibers at DWCNT content close to 1.0 wt. % • Hollow filaments formed at high DWCNT content paving way to hollow fiber technology Carbon fibers (CF) were formed from carbon nanotube-doped isotropic petroleum pitch. Ultra-long (the length of a single filament is more than 10,000 nm) double-walled carbon nanotubes (DWCNT) were used for doping in concentrations from 0.1 to 1.0 wt. %. The produced CF were investigated both in pristine and graphitized form. Physical properties (electrical resistivity, thermal conductivity coefficient), as well as X-ray diffraction (XRD) analysis and Raman spectroscopy of obtained DWCNT-doped CF were investigated. The influence of DWCNT concentration on the properties is nonlinear due to the influence on the CF molding mode and heterogeneity of the DWCNT distribution in the filament body. An increase in the DWCNT concentration, on the one hand, causes an enhancement in the thermal conductivity coefficient, and a decrease in the electrical resistivity of the fibers, on the other hand, it leads to local inhomogeneities formation in the material structure («gas bubbles»), as well as distortions of the CF outer surface. An increase in the DWCNT concentration also leads to an increase in CF average diameter and hollow filaments formation. This feature is paving the way to the development of novel technological methods to control CF properties and morphology, especially to feasible hollow CF composites manufacture.

Microtubules in Microorganisms: How Tubulin Isotypes Contribute to Diverse Cytoskeletal Functions.

The cellular functions of the microtubule (MT) cytoskeleton range from relatively simple to amazingly complex. Assembled from tubulin, a heterodimeric protein with α- and β-tubulin subunits, microtubules are long, hollow cylindrical filaments with inherent polarity. They are intrinsically dynamic polymers that utilize GTP binding by tubulin, and subsequent hydrolysis, to drive spontaneous assembly and disassembly. Early studies indicated that cellular MTs are composed of multiple variants, or isotypes, of α- and β-tubulins, and that these multi-isotype polymers are further diversified by a range of posttranslational modifications (PTMs) to tubulin. These findings support the multi-tubulin hypothesis whereby individual, or combinations of tubulin isotypes possess unique properties needed to support diverse MT structures and/or cellular processes. Beginning 40 years ago researchers have sought to address this hypothesis, and the role of tubulin isotypes, by exploiting experimentally accessible, genetically tractable and functionally conserved model systems. Among these systems, important insights have been gained from eukaryotic microbial models. In this review, we illustrate how using microorganisms yielded among the earliest evidence that tubulin isotypes harbor distinct properties, as well as recent insights as to how they facilitate specific cellular processes. Ongoing and future research in microorganisms will likely continue to reveal basic mechanisms for how tubulin isotypes facilitate MT functions, along with valuable perspectives on how they mediate the range of conserved and diverse processes observed across eukaryotic microbes.

Efficient transport system of cultivated mushroom mycelium enables its derived carbon with high performance electrochemical desalination capability

Capacitive deionization (CDI) is regarded as a promising desalination technology because of its high efficiency and low energy consumption. Electrode materials with high surface area, abundant active sites, and interconnected pore structure are the key to enhancing the electrochemical performance of CDI devices. Here, we selectively cultivated mushroom mycelia as the precursor to fabricate a hierarchically porous carbon electrode that consists of interwoven and hollow filaments for the CDI. By using the high-efficiency transport system of mycelia that natural evolution endows with, the resultant mycelia-derived carbon (MDC) exhibits a high surface area of 3603 m2 g−1 and delivers a high capacity of 260 F g−1. The assembled CDI devices could realize a superior salt removal capacity of 24.17 mg g−1. Efficient transport system of mycelia enables MDC to rapidly remove salts from solution with an extremely short characterization time. Such a high-efficiency CDI electrode could be attributed to the use of naturally-optimized transport system, high surface area, and heteroatomic surface. In contrast with artificial chemical synthesis, biologic cultivation offers some higher-order structures that conventional technologies would not easily achieve. This work provides an alternative approach to improving the transport of hierarchical CDI electrodes from living things.

Hollow Filaments Synthesized by Dry-Jet Wet Spinning of Cellulose Nanofibrils: Structural Properties and Thermoregulation with Phase-Change Infills.

We use dry-jet wet spinning in a coaxial configuration by extruding an aqueous colloidal suspension of oxidized nanocellulose (hydrogel shell) combined with airflow in the core. The coagulation of the hydrogel in a water bath results in hollow filaments (HF) that are drawn continuously at relatively high rates. Small-angle and wide-angle X-ray scattering (SAXS/WAXS) reveals the orientation and order of the cellulose sheath, depending on the applied shear flow and drying method (free-drying and drying under tension). The obtained dry HF show Young’s modulus and tensile strength of up to 9 GPa and 66 MPa, respectively. Two types of phase-change materials (PCM), polyethylene glycol (PEG) and paraffin (PA), are used as infills to enable filaments for energy regulation. An increased strain (9%) is observed in the PCM-filled filaments (HF-PEG and HF-PA). The filaments display similar thermal behavior (dynamic scanning calorimetry) compared to the neat infill, PEG, or paraffin, reaching a maximum latent heat capacity of 170 J·g–1 (48–55 °C) and 169 J·g–1 (52–54 °C), respectively. Overall, this study demonstrates the facile and scalable production of two-component core-shell filaments that combine structural integrity, heat storage, and thermoregulation properties.

Combining Optical Microscopy and X-ray Computed Tomography Reveals Novel Morphologies and Growth Processes of Methane Hydrate in Sand Pores

Understanding the mechanisms involved in the formation and growth of methane hydrate in marine sandy sediments is crucial for investigating the thermo-hydro-mechanical behavior of gas hydrate marine sediments. In this study, high-resolution optical microscopy and synchrotron X-ray computed tomography were used together to observe methane hydrate growing under excess gas conditions in a coarse sandy sediment. The high spatial and complementary temporal resolutions of these techniques allow growth processes and accompanying redistribution of water or brine to be observed over spatial scales down to the micrometre—i.e., well below pore size—and temporal scales below 1 s. Gas hydrate morphological and growth features that cannot be identified by X-ray computed tomography alone, such as hollow filaments, were revealed. These filaments sprouted from hydrate crusts at water–gas interfaces as water was being transported from their interior to their tips in the gas (methane), which extend in the µm/s range. Haines jumps are visualized when the growing hydrate crust hits a water pool, such as capillary bridges between grains or liquid droplets sitting on the substrate—a capillary-driven mechanism that has some analogy with cryogenic suction in water-bearing freezing soils. These features cannot be accounted for by the hydrate pore habit models proposed about two decades ago, which, in the absence of any observation at pore scale, were indeed useful for constructing mechanical and petrophysical models of gas hydrate-bearing sediments.

A synthetic tubular molecular transport system

Creating artificial macromolecular transport systems that can support the movement of molecules along defined routes is a key goal of nanotechnology. Here, we report the bottom-up construction of a macromolecular transport system in which molecular pistons diffusively move through micrometer-long, hollow filaments. The pistons can cover micrometer distances in fractions of seconds. We build the system using multi-layer DNA origami and analyze the structures of the components using transmission electron microscopy. We study the motion of the pistons along the tubes using single-molecule fluorescence microscopy and perform Langevin simulations to reveal details of the free energy surface that directs the motions of the pistons. The tubular transport system achieves diffusivities and displacement ranges known from natural molecular motors and realizes mobility improvements over five orders of magnitude compared to previous artificial random walker designs. Electric fields can also be employed to actively pull the pistons along the filaments, thereby realizing a nanoscale electric rail system. Our system presents a platform for artificial motors that move autonomously driven by chemical fuels and for performing nanotribology studies, and it could form a basis for future molecular transportation networks.

UV curing–assisted 3D plotting of core-shelled feedrod for macroporous hydroxyapatite scaffolds comprised of microporous hollow filaments

The present study demonstrates the manufacturing of macroporous hydroxyapatite (HA) scaffolds, comprised of microporous hollow filaments with high shape retention, by UV curing-assisted 3D plotting using a feedrod comprised of a photocurable HA shell and a carbon black (CB) core. Two types of scaffolds with different filament interspaces (0.5 mm and 1 mm) were produced by depositing core-shelled filaments extruded through a 1.07-mm-diameter nozzle with in situ polymerization process. Both scaffolds exhibited that the hollow HA filaments were produced after the removal of CB core by heat-treatment, while micropores in the HA walls were created as the replica of camphene-camphor crystals. Overall porosity and macroporosity obtained using a camphene-camphor content of 60 vol% increased from 74.3 vol% to 79.3 vol% and from 50.7 vol% and 64.6 vol%, respectively, with an increase in filament interspace sizes from 0.5 mm to 1 mm. Both scaffolds exhibited reasonably high compressive strengths (2.36 ― 3.58 MPa) and modulus (68–86 MPa).

Influence of biotic vs abiotic processes on the genesis of non‐marine carbonates along the Cameroon Volcanic Line (Cameroon) and palaeofluid provenance

AbstractContinental spring carbonates are perfect examples of the interaction of biotic and abiotic processes, and they preserve evidence of the velocity of the flow and the chemical composition of the spring water. This study focuses on non‐marine carbonates from fossil and active springs from the Bongongo and Ngol areas along the Cameroon Volcanic Line in South‐West Cameroon. Here, hydrothermal fluids reach the surface giving rise to small thermal springs, with temperatures between 31 and 49°C, and streams creating waterfalls, terracettes and barrage carbonate deposits. Petrographic analyses of these carbonates revealed that they are made up of stacked laminae of fibrous coarse crystals of low‐Mg calcite and laminae of alternate microsparite and micrite. The fibrous coarsely crystalline calcite, often with feather‐like fabric, grows from thin layers of micrite and peloids. Filaments of putative microbial origin are preserved within this peloidal micrite. The laminated microsparite and micrite microfacies is characterised by an intricate mesh of hollow filaments of microbial origin. The long feather‐like crystals of calcite formed in fast‐flowing water where the enhanced CO2 degassing has favoured the precipitation of CaCO3. The laminated micrite and microsparite, on the other hand, are probably formed in ponds where degassing and CO2 removal was lower and the calcite precipitation was fostered by microbial activity. The fast‐forming carbonates show higher Ce contents and very low total rare earth elements, revealing a preferential uptake of Ce with respect to other rare earth elements. This process would explain the positive or null Ce anomaly in continental spring carbonates elsewhere. The geochemical composition of these carbonates can be used as proxy for the characterisation of fluid/rock interactions between the groundwater and the substratum and for the characterisation of the sources of calcium and other elements that constitute tufa and travertines. The samples from Ngol are characterised by light rare earth element enrichment while those from Bongongo are overall enriched in heavy rare earth elements. Carbonates from both localities have a strong positive Eu anomaly (>4), suggesting a contribution from deep‐seated, hydrothermal, crustal fluids in contact with volcanic rocks and the breakdown of plagioclase from the Cameroon Volcanic Line alkali basalts.

Combustion/decomposition characteristics of 3D-printed Al/CuO, Al/Fe2O3, Al/Bi2O3 and Al/PTFE hollow filaments

In recent decades, the preparation of various metastable intermolecular composites (MICs) has been widely reported in pursuit of excellent reactivity and safety. However, there is still relatively little research on structural energetic materials (EMs) through 3D printing of MICs inks. In this work, the hollow filaments with different MICs formulas were prepared by 3D printing using a core-shell nozzle. The morphology, thermal decomposition and gas-generation performance of the filaments were characterized, and the different combustion stages of the filaments were analyzed. The results show that the hollow filaments exhibit shorter unsteady combustion time and significantly increased steady flame propagation rate compared with solid filaments. For the hollow filaments of Al/CuO/F2311 formula (15 wt % of F2311), the unsteady combustion time is as low as 0.65 ms, and the steady flame propagation rate reaches 206.936 g/s. Thermal analysis and constant-volume combustion tests show that Al/CuO/F2311 formula provides the lowest thermal decomposition onset temperature (288 °C) and the best gas-generation performance (peak pressure: 0.191 MPa, pressurization rate: 12.337 MPa/s) compared with other composites.

Quantitative detection of optical anisotropy of single microtubules by polarization-sensitive interferometric scattering microscopy

Microtubules (MTs) are ubiquitous cytoskeletal biopolymers essential for diverse cellular processes. MTs consist of strictly ordered tubulin dimers arranged into hollow cylindrical filaments and are known to be optically anisotropic, which enables their direct observation in microscopes based on polarization contrast. However, there are no experimental data to quantify the relation between the momentary optical anisotropy of the MT and the immediate arrangement of proteins in the MT structure. In this work, we introduce polarization-sensitive microscopy based on interferometric detection of scattering to quantify the scattering anisotropy of single unlabeled MTs with high precision. Our data explain the structural origin of MT anisotropy with a marginal contribution of the intrinsic asymmetry of a single tubulin molecule. We monitor changes in the MT scattering resulting from the binding of tau proteins to single MTs with a resolution of several proteins per diffraction-limited spot. We associate the changes in the contrast as well as in the scattering anisotropy with the formation of a shell around the MT formed by densely packed tau proteins. Our experimental results match closely with the theoretical model of the MT and include quantitative details about the polarization-dependent interaction of light with biological matter.

Designed and fabrication of triple-layered vascular scaffold with microchannels

Currently, one of the best preparation strategies for the triple-layered vascular scaffold is to imitate the three-layer structure of natural blood vessels to achieve the biofunctional characteristics of vascular transplantation. Here, we developed a combinatorial method to fabricate triple-layered vascular scaffold (TVS) by using electrospinning and coaxial 3 D printing. First, Polycaprolactone-collagen (PCL-Col) was applied to prepared the inner layer of TVS by electrospinning. Second, egg white/sodium alginate (EW/SA) blend hydrogel was extruded to form hollow filaments by coaxial 3 D printing and crosslinking mechanism, which enwound around the surface of the inner layer in a circumferential direction as the intermediate layer of TVS. Finally, electrospun PCL-Col nanofibers were wrapped on the surface of hydrogel layer as the outer layer of TVS. The morphological characterization and mechanical strength of the fabricated TVS were measured. Compared with natural blood vessels, results shown that ultimate tensile stress (UTS), strain to failure (STF), the estimated burst strength and the suture retention strength (SRS) of TVS were superior. Also, the fabricated TVS exhibits good hydrophilicity and excellent flexibility. Moreover, the biocompatibility of TVS was investigated through human umbilical vein endothelial cells (HUVECs), the results demonstrated that cells can successfully attach the surface of graft and maintain high viability. In summary, all of results demonstrated that this method could fabricate a novel triple-layered vascular scaffold, possessing appropriate mechanical properties and good biological properties, which has the potential to be used in tissue engineered vascular grafts applications.

THE MORPHOLOGY FEATURES OF NANOSTRUCTURE OF ZIRCONIUM, MOLYBDENUM AND WOLFRAM OXIDES SYNTHESISED BY LASER ABLATION OF METALS IN WATER

The paper gives the investigation results of composition and morphology of oxide nanostructures of transition metals – zirconium, molybdenum and wolfram synthesized by laser ablation pure metals in water. High temperatures and pressures in zone of interaction of the pulse laser beam with the surface of metal in water contribute to the intensive synthesis of oxides in the form of clusters of particles with size about 1−2 nanometres. This is characteristic for metals with high ionization potential. As it follows from the data of X-ray diffraction analysis and scanning electron microscopy, specifically, the clusters are amorphous building material for nanostructures of the oxides of the metals enumerated above. The paper demonstrates the general pattern of their structure, namely, the stratification of the material from which the foam formations, thin-walled hollow round particles, plates, filaments, and other forms of nanostructures are composed. The research of morphological features of the nanostructures of zirconium, molybdenum and wolfram oxides obtained by the authors indicates that their use as substrates will achieve high gain values of Raman scattering ~ 10 4 −10 8 . In this range, there are the gain data previously obtained by the authors in the experiments on the synthesis of zirconium nano-oxides when using them as a substrate. This indicates that the nanostructures of molybdenum and wolfram nano-oxides also can serve as the effective substrates and can be used as a sensor in the high sensitive composition of substances analyzers based on surface enhanced Raman scattering.

Coextrusion-Based 3D Plotting of Ceramic Pastes for Porous Calcium Phosphate Scaffolds Comprised of Hollow Filaments.

This paper demonstrates the utility of coextrusion-based 3D plotting of ceramic pastes (CoEx-3DP) as a new type of additive manufacturing (AM) technique, which can produce porous calcium phosphate (CaP) ceramic scaffolds comprised of hollow CaP filaments. In this technique, green filaments with a controlled core/shell structure can be produced by coextruding an initial feedrod, comprised of the carbon black (CB) core and CaP shell, through a fine nozzle in an acetone bath and then deposited in a controlled manner according to predetermined paths. In addition, channels in CaP filaments can be created through the removal of the CB cores during heat-treatment. Produced CaP scaffolds had two different types of pores with well-defined geometries: three-dimensionally interconnected pores (~360 × 230 μm2 in sizes) and channels (>100 μm in diameter) in hollow CaP filaments. The porous scaffolds showed high compressive strengths of ~12.3 ± 2.2 MPa at a high porosity of ~73 vol % when compressed parallel to the direction of the hollow CaP filaments. In addition, the mechanical properties of porous CaP scaffolds could be tailored by adjusting their porosity, for example, compressive strengths of 4.8 ± 1.1 MPa at a porosity of ~82 vol %. The porous CaP scaffold showed good biocompatibility, which was assessed by in vitro cell tests, where several the cells adhered to and spread actively with the outer and inner surfaces of the hollow CaP filaments.