Melt electrowriting of PCL/BaTiO₃ composites: Printability, anisotropic mechanical properties, and cytocompatibility

Melt electrowriting (MEW) is a less-explored yet promising additive manufacturing technique for fabricating tissue-engineered scaffolds with the designed microarchitecture. One of the significant advantages of MEW is the ability to manufacture scaffolds with controlled thinner fiber strands, which cannot be produced by other competitive techniques, like electrospinning. The key requirements for melt electrowritability include melt viscosity, electroactivity of the biomaterial ink, among other factors. Although poly (ε-caprolactone) (PCL) scaffolds have been widely investigated in the MEW domain, their inherently low electroactivity remains a major limitation. To address these challenges, we systematically investigated the melt electrowritability of biomaterial inks comprising of PCL and barium titanate (10-30 wt% BT), with a particular focus on component miscibility, rheological behavior, printability, mechanical strength /modulus and cytocompatibility. The MEW process parameters for PCL/10BT were systematically optimized to achieve consistent fiber deposition (∼30 μm diameter) and high-fidelity deposition. In contrast, PCL/20BT and PCL/30BT scaffolds exhibited poor and irreproducible printability. The interplay between MEW process parameters (printing pressure, collector distance, printing speed melt temperature) and printability has been critically analyzed in terms of BaTiO₃ loading-dependent melt viscosity, shear alignments of fibers, flow stability, and fiber trajectory/structure continuity. While 10 % BaTiO₃ addition to PCL biomaterial ink substantially enhances 3D printability and buildability (10 layers) in MEW route, the orientational dependence of tensile properties (strength/modulus) is attributed to multilayered structure, with anisotropic behavior being analogous to fiber-reinforced composites. Additionally, the buildability limitation, beyond 40 layers of PCL/10BT to produce a fibrous scaffold construct has been attributed to the polarization-induced residual surface charge accumulation and spatial distribution, promoting interlayer repulsion. Cytocompatibility study using NIH3T3 fibroblasts revealed excellent cellular alignment and growth on melt electrowritten fiber strands of PCL/10BT, in a manner much better than pristine PCL. Overall, this study demonstrates the beneficial effect of BaTiO₃ incorporation on the mechanical and biological performance of MEW-processed PCL scaffolds, while highlighting printability limitations at higher BaTiO₃ contents.