Introduction

Additive manufacturing (AM) has been one of the great intelligent automation technologies that emerged with Industry 4.0, the fourth industrial revolution [1,2,3], and reached demanding areas of rapid prototyping in product development. The AM, layer by layer, has become consolidated as cost-effective and less resource usage, customization, on-demand, and decentralized production [4]. Besides, AM can be highlighted due to its energy conservation [5] and sustainability due to lower pollutant emissions [6, 7].

As one of many kinds of AM, fused deposition modeling (FDM) is a 3D printing technique based on melting extruded thermoplastic filaments and their deposition of layers [8], the melted and extruded material passes through a nozzle in a heated printer head onto an x–y–z-platform [9], according to pre-set parameters. FDM technique has been attractive for its advantages like common use and availability [10], flexibility, and the ability to build complex parts [11]. Besides, previous studies demonstrated the crescent interest of FDM filament fabrication as an important area [12, 13]. Therefore, with FDM technology, regenerative medicine gained a tool to obtain scaffolds, small three-dimensional structures with interconnected pores, which act as a support for tissue regeneration and can be demonstrated by the literature [14, 15].

Biomaterials can be applied to temporarily support tissue growth [16]. In order to mimic the tissues of a living organism, Diermann et al. [17] mentioned that a scaffold material must be biocompatible, biodegradable, and bioactive (common characteristics of biopolymers and bioceramics). The feasibility of the FDM technique for printing scaffolds can be found in several scientific articles. Choi et al. used poly (lactic acid) (PLA) as extruded filaments to print porous scaffolds by the FDM technique with design freedom as a one-step process [18]. Kovalcik et al. obtained scaffolds by FDM technique from different polyhydroxyalcanoates (PHA’s), where polyhydroxybutyrate-cohydroxyvalerate (PHBV) scaffolds stood out for having excellent cell proliferation, nontoxic, with good thermal and mechanical properties [19]. Saska et al. used poly(3-hydroxybutyrate) (PHB) functionalized with osteogenic growth peptide for printing scaffolds by FDM [20]. Ceretti et al. produced multilayered scaffolds of polycaprolactone (PCL) using an open-source FDM printer to study the filament extrusion in the heated print head [14]. Figure 1 evidences the FDM technique of printing a scaffold.

Fig. 1
figure 1

FDM printing a scaffold

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An example of biopolymers with those characteristics had been the PHA’s polyhydroxyalcanoates group (PHA’s) [21], such as PHB and PHBV for example. Produced from natural resources by bacterial fermentation [22], PHA’s are known for having similar properties of low-density polyethylene [23] and good bone regeneration when implanted in an in vivo in bone tissue [24]. Therefore, polyhydroxybutyrate-cohydroxyvalerate (PHBV) biopolymer is an attractive PHA’s for medical applications [25], for its biocompatibility properties and good cellular response, as well as its degradation in vivo to hydroxybutyric acid, metabolized by the body [26] although PHBV has shortcomings such as a narrow processing window, expensive, thermal instability, and low impact resistance [25]. Thus, improvement alternatives can solve these drawbacks, such as oxide incorporation in the PHBV matrix or cellulose incorporation, as mentioned in the literature. Shuai et al. proposed the incorporation of zinc oxide in the PHBV matrix to improve its mechanical properties, as well as increasing its crystallinity and its antibacterial character [27]. Rivera-Briso et al. used graphene oxide nanosheets and carbon nanofiber in the PHBV matrix to improve thermal properties, compression characteristics, wettability, and cell proliferation [28]. Augustine et al. incorporated cerium oxide nanoparticles to improve PHBV properties for diabetic wound healing applications [29]. Benini et al. used nanocellulose from pineapple crown in the PHBV matrix and obtained improvements in thermal behavior and crystallinity [30].

Compounds of inorganic oxides have been used to improve polymer properties [31]. Organic–inorganic composite materials and the affinity of the different phases can enhance the polymeric matrix properties. That behavior occurs due to covalent bonds or physical interactions among the organic polymer matrix and inorganic material [23]. In a PHBV matrix, the literature already demonstrated studies with the following reinforcements: zinc oxide [32], silicon dioxide [33], graphite oxide [34], titanium dioxide [35], clay [36], calcium phosphate [37], bioglass [38], attapulgite [39], hydroxyapatite [40], graphene [41], etc. However, there is a lack of studies with PHBV reinforced with zirconium oxide (ZrO2).

The objective of this research was to develop and characterize PHBV composite filaments reinforced with hydrous zirconium oxide (ZrO2·nH2O) to obtain scaffolds using the FDM 3D printing technique. Zirconium oxide (ZrO2) is an inorganic material that is an excellent bioceramic due to its good mechanical strength, toughness, chemical stability, biocompatibility, and ability to proliferate osteoblast cells in bone tissue engineering [42]. Da Silva et al. [23] indicated that the addition of ZrO2 to the polyhydroxybutyrate (PHB) matrix caused thermal and mechanical improvements. Subsequently, ZrO2·nH2O can also be a good alternative to improve PHBV properties.

The novelty of this work is based on the lack of studies dealing with ZrO2 as the reinforcement of PHBV biopolymer, especially for applications of FDM filaments for scaffold manufacturing. There is also a lack of studies with the particle analysis of reinforcements in FDM filaments and studies with Vickers hardness test for FDM filaments. Moreover, the development of filaments encourages the use of the FDM technique, one of the most accessible for manufacturing materials of noble application in tissue engineering.

Materials and method

Materials

With the purpose of obtaining the composite filaments (PHBV/ZrO2), the PHBV from Biocycle 1000 was supplied by PHB Industrial S/A [43]. PHBV properties provided by the supplier can be seen in Table 1. The ZrO2·nH2O synthesis was according to the method of conventional precipitation described by Mulinari and Da Silva [44].

Table 1 PHBV Properties
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Preparation of PHBV/ ZrO2·nH2O filaments

Firstly, PHBV dried pellets were mixed with the ZrO2·nH2O (1 to 10% wt/wt). The filaments of PHBV reinforced with different amounts of ZrO2·nH2O (1 to 10% wt/wt) were obtained using a mini-extruder (brand Weellzoom, model B Desktop, Guangdong Prov, China), and the composite samples with ZrO2·nH2O were called PHBV/ X%ZrO2 where X stands for 1, 2.5, 5, 7.5 and 10% of dispersed ZrO2·nH2O.

Characterization PHBV, ZrO2·nH2O, and PHBV/ ZrO2·nH2O

The morphology of the filaments (pristine PHBV and composites) was investigated by Stereomicroscopy (brand ZEISS, model Axio Imager 2, New York, USA). The microstructure of the filaments (composites and pristine PHBV) and the morphology of the ZrO2·nH2O were also examined by scanning electron microscopy (SEM) microscope (brand HITACHI, Mannheim, Germany), with tungsten filament operating at 5 kV, employing a low-vacuum technique and secondary electron detector. Samples were dispersed on brass support and fixed with a double face 3 M tape. The particle analysis was performed in the images of the filaments by SEM. The ImageJ software measured the diameter of all extruded filaments and analyzed the ZrO2·nH2O particles on the surface of each composite filament.

Thermal analyses were performed to evaluate the stability of the ZrO2·nH2O, pristine PHBV filament, and composite filaments (PHBV/ZrO2) through a thermogravimetric analyzer (TA Instruments simultaneous TGA/DSC system, model SDT Q600, New Castle, USA). Experiments were carried out under continuous nitrogen flow, with a heating rate of 10 °C min−1, from 30 °C to 600 °C and a specimen weight of 5 mg.

The physical structures of the materials were evaluated by X-ray diffraction (diffractometer Shimadzu Scientific Instruments Incorporated, model XDR-6100, Kyoto, Japan). The measuring conditions were: CuKa radiation with graphite monochromator, 30 kV voltage, and 40 mA electric current. The patterns were obtained in 10–50° angular intervals with 0.05 step and 1 s of counting time.

Micrometer Vickers hardness analysis was performed with a micrometer (HVS Micro Hardness Tester, Hong Kong, China) with a pyramidal diamond tip, on 0.5-mm-thick segments of the material. The material was subjected to indentation with a load of 0.01 mgf/msec and subsequently the indentation area generated for hardness calculation was measured.

The chemical structures of the ZrO2·nH2O, pristine PHBV filament, and composite filaments (PHBV/ZrO2) were analyzed by attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectroscopy (Perkin Elmer® Inc, model Spectrum 100, Massachusetts, USA). The analysis was performed in a transmittance mode, in a range of 4500–400 cm−1, at a resolution of 4 cm−1.

Manufacture of PHBV/ ZrO2·nH2O scaffolds

The pristine PHBV and PHBV/ZrO2·nH2O composite scaffolds (1–7.5% ZrO2·nH2O) were designed in TinkerCAD software in cylindrical format and 3D printed using their respective filaments by FDM (GO3DS 3D printer, São José dos Campos, Brazil) with 50% filling and processing temperature of ~ 165 °C.

Relative density estimation

Relative density estimation weights and dimensions of the scaffolds (pristine PHBV and PHBV/ ZrO2·nH2O composite scaffolds with 1–7.5% ZrO2·nH2O) were measured to calculate their densities. The relative density value of scaffolds (pristine PHBV and PHBV/ ZrO2.nH2O composite scaffolds with 1–7.5% ZrO2·nH2O) was calculated as Eq. (1) [45]:

$$ \rho^*\, = \frac{{\rho_{{{\text{scaffold}}}} }}{{\rho_{{{\text{solid}}}} }} $$
(1)

where ρsolid is the PHBV solid density of 1.23 g/cm3 (Table 1).

Results

Preparation of PHBV/ ZrO2·nH2O filaments

The processing temperature of the composite filaments (PHBV/ ZrO2·nH2O) in the mini-extruder (Fig. 2) was mostly 165 °C (except, PHBV/10% ZrO2·nH2O with 160 °C), slightly lower than the melting temperature (Tmelting) in Table 1 (167.2 °C). The extrusion speed can influence filament linearity [46]. The extrusion speed used to obtain the most linear filaments was 370 mm/min. The extrusion process can be seen in Fig. 2. Geng et al. [46] obtained polyether-ether-ketone (PEEK) filaments analogous to the appearance of the filaments in this research.

Fig. 2
figure 2

Filaments extrusion process (left) and photograph images of the all obtained filaments (right)

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Physical–chemical characterization

Figure 3 shows the filaments submitted to the stereomicroscopy technique. It was observed that the filaments did not reveal extreme changes in color except the filaments PHBV/2.5% ZrO2·nH2O and PHBV/10% ZrO2·nH2O (with the highest percentage of oxide), possibly due to the agglomeration of the oxide in the extrusion, also observed by Barbosa and Kenny [47] in polypropylene filaments reinforced with glass fibers. The color change may have been caused by agglomeration but randomly. The process of mixing the reinforcement in the matrix medium may have been insufficient to promote a homogeneous mixture during the extrusion, forming localized parts with a greater amount of oxide than others due to the change in viscosity with the addition of oxide. This fact shows the need for better mixing methods, for better dispersion of the particles. Costa et al. achieved a good dispersion of alumina particles (Al2O3) by a thermokinetic mixer that did not compromise the thermal properties of the high-density polyethylene (HDPE) matrix, guaranteeing good mechanical and thermal properties due to good dispersion of the dispersed phase in the composites [48]. The agglomeration might cause an increase in the roughness in the filament surface, making it difficult to slide the filament through the parts of the 3D printer. Lubricants, precise temperature regulation, and extrusion speed control would be needed to improve the surface quality, and possibly contribute to lower mechanical properties [49].

Fig. 3
figure 3

Stereomicroscopy of the filaments: a PHBV; b PHBV/1%ZrO2, c PHBV/2.5%ZrO2, d PHBV/5%ZrO2, e PHBV/7.5%ZrO2 and f) PHBV/10%ZrO2

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On the other hand, a change was evidenced in the filament microstructures observed by the SEM technique (Fig. 4). The morphology of ZrO2·nH2O demonstrated the formation of blocks with their agglomerated particles (Fig. 4a–c), which may inhibit the homogenization process between oxide and polymeric matrix, causing defects in the filament. Thus, the addition of oxide in the composition of the filaments was noted whitish points on the surface of the filaments (Fig. 4d–o), also observed by Mallakpour and Ahmadreza [50] in nanocomposites based on modified ZrO2 nanoparticles and by Bedi, Singh, and Ahuja [51] in recycled LDPE filaments reinforced with SiC/Al2O3.

Fig. 4
figure 4

SEM of ZrO2.nH2O (a, b and c); SEM of the composite filaments: PHBV(d and e); PHBV/1% ZrO2(f and g); PHBV/2.5% ZrO2(h and i); PHBV/5% ZrO2 (j and k); PHBV/7.5% ZrO2(l and m); PHBV/10%ZrO2 (n and o)

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Table 2 reveals the results of the ImageJ analysis by the SEM images. It was observed that the filament diameters were homogeneous, due to the small standard deviation. Compared to the pristine PHBV filament, the diameters of the composite filaments (PHBV/ ZrO2·nH2O) decreased. Besides, all filaments were smaller than the diameter found in standard industrial filaments (1.75 mm) [52]. The analysis of ZrO2·nH2O particles revealed that there was an increase in the number of particles detected on the filament surface when adding ZrO2·nH2O, as well as an increase in the total area (%) in the image. An effect of particle agglomeration with the addition of ZrO2·nH2O (also observed by steromicroscopy) can be noted in the increase in measurements referring to the particle perimeter and the particle area. The smallest perimeter measurements were the same, as they reached the minimum size of the program according to the 1 mm scale of the SEM images.

Table 2 Measurement of the diameter of all filaments and analysis of ZrO2 particles from composite filaments using the SEM images
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The thermal stability of the pristine PHBV, ZrO2·nH2O, and composite filaments (PHBV/ ZrO2·nH2O) was investigated by thermogravimetric analysis —Fig. 5 shows the TG and DTG results. The curve obtained for pristine PHBV filament and composite filaments (PHBV/ ZrO2·nH2O) demonstrated one single event of weight loss in a narrow temperature range attributed to the thermal decomposition of PHBV, demonstrating the remarkable thermal stabilization effect induced by the presence of the ZrO2·nH2O particles. The TG and DTG curves displayed, respectively, that the degradation Tonset and the temperature of the maximum rate of weight loss of the composite filaments (PHBV/ ZrO2·nH2O) with the two highest concentrations of ZrO2·nH2O—notably PHBV/7.5% ZrO2·nH2O and PHBV/10% ZrO2·nH2O—shifted toward slightly lower temperatures compared to the pristine PHBV filament.

Fig. 5
figure 5

a TG and b DTG curves for PHBV filament, ZrO2.nH2O and PHBV/ZrO2 composites

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The good dispersion of ZrO2·nH2O in the matrix and the strong interactions between the two composite components via hydrogen bonding would originate a barrier effect against the transport of decomposition products from the bulk of the matrix to the gas phase, result in enhanced thermal stability for the composites [42]. Besides, a gradual increase in the residue was noted with increasing ZrO2·nH2O content, indicating that a higher fraction of material did not volatilize upon thermal degradation. Similar thermal behavior was seen by Thiré et al. [39] in nanocomposites based on PHBV and organophilicattapulgite. Table 3 summarizes the results obtained from TG, DTG, and DSC curves.

Table 3 TGA and DSC results for PHBV filament, ZrO2.nH2O and PHBV/ZrO2 composites: crystallization temperature (Tc), melting temperature (Tm), onset temperature (Tonset) of the degradation process, temperature of maximum rate of weight loss (Td), mass loss temperature data from TG curves and amount of residue at 600 °C
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Figure 6 demonstrates DSC curves for the pristine PHBV filament, ZrO2·nH2O, and composite filaments (PHBV/ ZrO2·nH2O). The values of crystallization temperature (Tc) and crystalline melting temperature (Tm) which are described in Table 3, were obtained from these graphs. The shape of the DSC curves obtained for PHBV filament and ZrO2·nH2O composites revealed the same profile—the small endothermic peak related to the melting process, indicating that the crystalline structure of both components was maintained. The incorporation of ZrO2·nH2O decreased the cold crystallization temperature, indicating an enhanced crystallization ability of PHBV. The ZrO2·nH2O acted as a nucleation agent and induced PHBV crystallization at lower temperatures. A slight increase in melting temperatures was observed with the addition of ZrO2·nH2O when compared to the pristine PHBV filament; however, the increase of the percentage of ZrO2·nH2O and nucleate did not have a significant influence on this variation. It is, however, worth mentioning that the presence of the oxide on the studied PHBV composite filaments (PHBV/ ZrO2·nH2O) did not affect the processing and the printing temperature as compared with pristine PHBV since the composites' thermal properties presented similarities. Analogous behavior has been reported by Díez-Pascual and Díez-Vicente [53] to study PHBV composites reinforced with 1, 2, 4, and 8% (wt) of ZnO.

Fig. 6
figure 6

DSC curves for PHBV filament, ZrO2.nH2O, and PHBV/ZrO2 composites

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The crystallinity in polymers can affect the mechanical properties [54] and the rate of degradation of the bioresorbable scaffolds (related to water absorption) [55]. In Fig. 7, it was possible to observe the sample diffractograms. The most distinct curve was ZrO2·nH2O (Fig. 7a), approximating a line due to its amorphous nature, also seen by literature [56].

Fig. 7
figure 7

Diffractograms of the ZrO2.nH2O, pristine PHBV and composite filaments: a range of 10°–50°; b zoom corresponding the range of ~ 10°to ~ 19° and c zoom corresponding the range of ~ 19°to ~ 24°

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The diffractograms of the PHBV sample revealed characteristic well-defined peaks (2θ) at 13.6°, 17.1°, 21.7°, 22.7°, 25.6° and 30.7°, which correspond to the (020), (110), (101), (111), (121) and (002) reflections of the orthorhombic crystalline lattice, respectively. The diffraction profile of pristine PHBV was equivalent to the PHB homopolymer [57], (Fig. 7c). However, it was noted a decrease in the peaks with ZrO2·nH2O addition, especially at the peaks of ~ 13.4°, ~ 16.8°, ~ 21.4°; ~ 22.5°; ~ 25.4°, ~ 27.1° and ~ 30.7º (Fig. 7b and c). Then, the addition of the ZrO2·nH2O affected the characteristic peaks of PHBV, decreasing the crystallinity of the composites. On the other hand, it can be observed that the peak positions remain practically unchanged in diffractograms of the composite filaments (PHBV/ ZrO2·nH2O). This fact suggests that the pristine PHBV crystalline lattice did not change appreciably in the presence of ZrO2·nH2O. That occurrence can be beneficial for its application in scaffolds, since, their degradation in the bioreabsorption process occurs first in the water penetrating and diffusing in the amorphous regions of the material, and later in the union of the polymeric chains [55].

Figure 8 reveals the spectra related to the samples analyzed by the FTIR. As can be seen in the XRD, the ZrO2·nH2O addition to the PHBV matrix affected the behavior of the composite filaments (PHBV/ZrO2) when compared to the pristine PHBV filament. Most of the characteristic bands of the PHBV matrix decreased after the addition of ZrO2·nH2O (Fig. 8b–d). The PHBV characteristic bands were (Fig. 8a): the asymmetric stretch of methyl C–H at 2981 cm−1; C–H asymmetric stretching of methylene at 2930 cm−1; C=O stretching band of the ester at 1721 cm−1; absorption band present at 1173 cm−1 corresponded to the asymmetric vibration of the C–O–CO (responsible for the bonding of the monomers in the form of polymers with a long chain); folding of the bond in the C=O group at 1459 cm−1; stretch in the C–C connection by 979 cm−1 [58, 59]. This high-intensity C=O band was attributed to the crystalline form of PHBV. The incorporation of the ZrO2·nH2O to the PHBV led to a sharp absorption in the wavelengths (absorption maxima in the 3370 − 3390 cm−1 region) of the O−H absorption observed for the ZrO2·nH2O. In Fig. 8a was possible to identify the low transmittance bands characteristic of amorphous zirconium oxide: the stretching of hydroxyls for 3228 cm−1 band (Fig. 8b) and vibrations of doubling of absorbed H2O for a 1618 cm−1 band (Fig. 8c) [60,61,62]. The sharp band at 640 cm−1 is the characteristic of m-ZrO2. A broad band around 1500 cm−1 is ascribed to Zr-O vibrations of t-ZrO2 [63].

Fig. 8
figure 8

FTIR spectra of the ZrO2.nH2O, pristine PHBV, and composite filaments: a range of 4000–630 cm−1; b zoom corresponding the range of 3600–2800 cm−1; c zoom corresponding the range of 2000–500 cm−1 and d zoom corresponding the range of 1500–630 cm−1

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The hardness of a polymer is related to the critical stress necessary to overcome the cohesive forces of the polymeric chain [64]. For the study of hardness, the strength of the indentation must be analyzed, through the depth of the indentation produced by a material with external penetration [65]. In the case of this work, the Vickers test can be considered a novelty, since there is a lack of researches in literature analyzing Vickers hardness in thermoplastic filaments for 3D application.

The pristine PHBV (Fig. 9) demonstrated a microhardness value of 105 MPa = 10.7 HV, and an analogous microhardness (13.2 HV) in PHBV composites was found in the literature [66]. As for the composite filaments (PHBV/ ZrO2·nH2O), the microhardness values were in the range of 90 to 105 MPa (9.2 to 10.7 HV), similar to pristine PHBV filament. The Vickers microhardness of the composites, tended to decrease with the addition of ZrO2·nH2O, suggesting the presence of microvoids. However, PHBV/7.5% ZrO2·nH2O had the highest microhardness value (162 MPa = 16.5 HV) and can be promising for scaffold applications in tissue engineering. An analogous microhardness value was found by Ramrakhiani et al. [67], representing a male skull bone (14.7 HV).

Fig. 9
figure 9

Microhardness of the composite filaments

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In addition to the presence of microvoids influencing the microhardness of the samples, the behavior of PHBV/7.5% ZrO2·nH2O may be related to the oxide agglomeration during extrusion (as seen in the stereomicroscopy results), compromising reinforcement contents above 7.5% ZrO2·nH2O and interfering in the composite hardness (making it fragile and mechanically unstable). The microhardness behavior in the PHBV/10% ZrO2·nH2O can corroborate with the impossibility to print this composite, which will be discussed in the next topic.

Additive manufacture of composite scaffolds PHBV/ ZrO2·nH2O with 1–7.5% ZrO2·nH2O

Scaffolds were developed with pristine PHBV filament and composite filaments (PHBV/ZrO2) from 1 to 7.5% w/w of ZrO2·nH2O. The common diameter of a commercial extruded filament for 3D printing is 1.75 mm [52]. From Table 2, it was seen that the filaments obtained in this work did not have values less than 1.47 mm in diameter (with 5% ZrO2·nH2O) being 16% smaller than commercial filaments. Although the diameter of the filaments was smaller than industrialized filaments (Table 2) [52], there were no difficulties in printing scaffolds due to this difference. However, the PHBV/10% ZrO2·nH2O was not capable of FDM printing due to the fragility in handling, probably due to the higher oxide load causing particle agglomeration (as seen by SEM and stereomicroscopy). Due to its fragility, the PHBV/10% ZrO2·nH2O composite filament broke when placed in the hole that feeds the FDM printer. In Fig. 10 was possible to notice the appearance of the scaffolds obtained and their cylindrical structure with rounded inner pores. As seen in Fig. 10a, the scaffold obtained was printed with interconnected pores. Figures 10b and c show the SEM images of the scaffolds with regular pores obtained by FDM printing. The literature demonstrated similar scaffolds to the ones obtained by this research [68,69,70,71,72]. The scaffold microstructure can determine its properties and applications [73]. The architecture of a scaffold must mimic the injured area which will be regenerated [74]. Therefore, the porosity of the scaffold is necessary, providing space and supply for cell growth. These pores must be interconnected, so that cell diffusion occurs in the surrounding tissue, as well as the vascularization of the new tissue in development [75].

Fig. 10.
figure 10

3D printed PHBV scaffold (a) and SEM images (b and c)

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The diameter of the printed scaffolds did not exceed the measurement of 14.73 mm and its thickness did not exceed the measurement of 4.19 mm (Table 4). The mass of the composites was greater than the pristine PHBV (except for PHBV/7.5% ZrO2·nH2O), the same was seen in the density where the boost in density was detected as the proportion of oxide rose (except for 5%).

Table 4 Measurements to find the relative density estimation (ρ*) of the scaffolds
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Conclusion

The overall appearance of the printed composites was acceptable: cylindrical structures and rounder inner pores. For the composite filaments, the addition of ZrO2·nH2O altered the filament behavior when compared with the pristine PHBV filament. SEM analysis showed that the extruded filaments were smaller than the standard industrialized filaments (however it did not affect their 3D printing). Besides, it was observed (by the particle analysis) that with the increase in ZrO2·nH2O to the PHBV, more particles were detected on the filament surface, the larger the area and the perimeter of the filament (due to agglomeration). The amount of ZrO2·nH2O incorporated into the matrix also influenced the thermal properties, a greater amount of residue was observed, and the melting temperature was higher. FT-IR spectra demonstrated that ZrO2·nH2O decreased the characteristic peaks of pristine PHBV in the composite filaments. XRD diffractograms demonstrated that the percentage of ZrO2·nH2O reinforced to the PHBV increased the amorphous phase (possibly facilitating bioreabsoption in its application as a scaffold). PHBV/7.5% ZrO2·nH2O composite filament presented the higher microhardness of them all, assembling to a male skull bone microhardness. As future works, it would be necessary to investigate the characteristics of the printed scaffolds as well as their applications in vitro and in vivo systems.