Polymeric blends are employed in the production of filaments for additive manufacturing to balance mechanical and processability properties. The mechanical and thermal properties of polymeric filaments made of poly (lactic acid) (PLA), polyhydroxyalkanoates (PHA), and its blend (PLA–PHA) are investigated herein and correlated to their measured structural and physicochemical properties. PLA exhibits the highest stiffness and tensile strength, but lower toughness. The mechanical properties of the PLA–PHA blend were similar to those of PLA, but with a significantly higher toughness. Despite the lower mechanical properties of neat PHA, incorporating a small amount (12 wt.%) of PHA into PLA significantly enhances toughness (approximately 50%) compared to pure PLA. The synergistic effect is attributed to the spherulitic morphology of blended PHA in PLA, promoting interactions between the amorphous regions of both polymers. Thermal stability is notably improved in the PLA–PHA blend, as determined by thermogravimetric analysis. The blend also exhibits lower cold crystallization and glass transition temperatures as compared to PLA, which is beneficial for additive manufacturing. Following additive manufacturing, X-ray photoelectron spectroscopic showed that the three filaments present an increase in C–C and C=O bonds associated with the loss of C–O bonds. The thermal process induces a slight increase in crystallinity in PHA due to chain reorganization. The study provides insights into the thermal and structural changes occurring during the melting process of additive manufacturing.

Articular cartilage is a specialized tissue that provides a smooth surface for joint movement and load transmission. Unfortunately, it has limited regenerative capacity. Tissue engineering, combining different cell types, scaffolds, growth factors, and physical stimulation has become an alternative for repairing and regenerating articular cartilage. Dental Follicle Mesenchymal Stem Cells (DFMSCs) are attractive candidates for cartilage tissue engineering because of their ability to differentiate into chondrocytes, on the other hand, the polymers blend like Polycaprolactone (PCL) and Poly Lactic-co-Glycolic Acid (PLGA) have shown promise given their mechanical properties and biocompatibility. In this work, the physicochemical properties of polymer blends were evaluated by Fourier Transform Infrared Spectroscopy (FTIR) and Scanning Electron Microscope (SEM) and were positive for both techniques. The DFMSCs demonstrated stemness by flow cytometry. The scaffold showed to be a non-toxic effect when we evaluated it with Alamar blue, and the samples were analyzed using SEM and phalloidin staining to evaluate cell adhesion to the scaffold. The synthesis of glycosaminoglycans was positive on the construct in vitro. Finally, the PCL/PLGA scaffold showed a better repair capacity than two commercial compounds, when tested in a chondral defect rat model. These results suggest that the PCL/PLGA (80:20) scaffold may be suitable for applications in the tissue engineering of articular hyaline cartilage.

Carbon nanotube yarns (CNTYs) are porous hierarchical fibers that exhibit a strong property-structure relationship. The morphology and structure of dry-spun CNTYs are characterized and correlated with their quasi-static and dynamic mechanical properties. These characterizations include assessment of the CNTY homogeneity by means of Raman spectroscopy mapping, determination of linear density and porosity, atomic force microscopy, and dedicated measurements of the statistical distribution of the yarn’s diameter. Tensile testing of CNTYs yielded a specific strength of 0.21–0.34 N/tex, and a specific elastic modulus of 3.59–8.06 N/tex, depending on the gage length. While the strength is weakly sensitive to the gage length, the elastic modulus depends on the gage length. The importance of subtracting the machine compliance for the determination of the CNTY’s elastic modulus is highlighted, since the error can reach up to 28%. Dynamic mechanical analysis shows that the CNTY is a stiff material with an extraordinary high damping ratio, which increases with temperature and reaches ∼0.6 at 60 °C. In addition, the CNTY presents a frequency-stiffening behavior in the 18–48 Hz range, with storage modulus (E′) and loss modulus (E″) which increase ∼2.5 times (E′) and ∼7 times (E″) at 48 Hz.

Carbon nanotube yarns (CNTYs) are outstanding hierarchical fibers with electrical properties that depend on temperature and mechanical stimuli, which makes them attractive as smart materials for sensing applications. In order to better understand the electrical response of CNTYs under a combination of dynamic loading and variations of temperature, their monotonic and cyclic tensile mechanical response, in situ Raman spectroscopy, mechanical hysteresis, and dynamic mechanical analysis (DMA) are investigated herein. The piezoresistivity and thermoresistivity of CNTYs were characterized to correlate the contribution of temperature and strain to the effective electrical response of the CNTY under DMA testing. It was found that the tensile load bearing of the CNTYs is governed mainly by structural changes of its bundles/fibrils, rather than by stretching of the carbon bonds. The large energy dissipation capabilities of the CNTYs arise mainly from friction among their fibrils and bundles, and also due to irreversible morphological changes in their hierarchical structure. The (mechanically constrained) thermoresistive characterization showed that the electrical resistance of the CNTYs decreases with increasing temperature, yielding an average temperature coefficient of resistance of −8.63 × 10⁻⁴ K⁻¹. The electrical response of the CNTYs during DMA temperature scans is governed by their thermoresistive response.

Developing scaffolds with all the necessary mechanical and biological characteristics to mimic cancellous bone and enable its regeneration presents significant challenges. In this work, we leveraged the distinct mechanical properties, elasticity, and degradation kinetics of three distinct polymers. To achieve this, a porogen with a customized internal architecture was produced via 3D printing. A solution containing the blend of the three polymers and jarosite powder was subsequently injected into the printed mold. The porogen structure was then leached away, leaving behind a porous scaffold with the desired internal geometry. This technique enables the fabrication of scaffolds with sinusoidal pores of varying sizes, which facilitate cell viability, proliferation, and nutrient transport. The primary objective of this study was to evaluate the synergistic effects of the three-polymer blend, jarosite doping, and a sinusoidal pore morphology on the behavior of human dental pulp mesenchymal stem cells (hDPMSCs). In vitro evaluations demonstrated that the constructed scaffolds are non-toxic, supporting cell viability, migration, and robust proliferation. Furthermore, the bioactive properties of jarosite and its associated ion release actively promote the differentiation of hDPMSCs into osteogenic lineages, demonstrating strong potential for bone tissue engineering applications.