## 1 Introduction
From a process engineering perspective, it is important to study the relationships between these process parameters, strand dimensions, and resulting mechanical properties of the scaffold. Understanding these relationships can enable the engineering of application-specific scaffolds with greater precision and reproducibility. Several studies have modeled the effects of extrusion-based AM parameters on the quality of fabricated structures. For example, [PERSON] et al. mapped the effects of layer height, strand width, and nozzle speed on the surface roughness of the FDM-printed specimens [20]. [PERSON] et al. modeled the effects of lay orientation, layer height, and layer filling strategy on the mechanical strength, surface quality, accuracy, and manufacturing time of FDM-printed acrylonitrile butadiene styrene structures [21]. In terms of additively manufactured PCL scaffolds, [PERSON] and [PERSON] reported on the mechanical properties of SLS-printed PCL with different strand lay orientations and micro-architectures [22]. [PERSON] et al. determined the effects of screw rotational speed and melting temperature on tensile strength and crystalline structure of extruded PCL filaments [23]. [PERSON] and [PERSON] demonstrated the effects of two 3 DB parameters, extrusion temperature and nozzle inner diameter, on the strand width and compression modulus of PCL scaffolds [11]. However, for the 3 DB process, the effects of extrusion pressure, nozzle speed, and strand orientation on strand width and mechanical properties of extruded PCL have not been characterized in the literature. Furthermore, computational models to estimate the mechanical properties are not available in literature either. This study aimed to contribute to our overall understanding of the process-structure interactions in melt extrusion-based 3 DB of PCL. The focus was on experimental characterization and subsequent statistical and finite element (FE) modeling of the effects of process parameters on structural and tensile properties of bioplotted PCL. The study was conducted in three interconnected phases (Figure 1). In Phase-1, the relationships between strand width and extrusion pressure, nozzle speed, lay orientation, and strand length were characterized. A regression model to estimate the strand width based on critical process parameters was developed and validated. To test the validity of the hypothesis that the strand width has an effect on the cell proliferation within a scaffold, two sets of porous scaffolds (\(\mathcal{O}\) 20 \(\times\) 2 mm, 0\({}^{\circ}\)/90\({}^{\circ}\) strand lay orientation) with contrasting strand widths resulting from extreme combinations of extrusion pressure and nozzle speed within the established design space were tested with NIH/3T3 fibroblast cells over 7 days in culture. Once the process-structure characteristics were understood, in Phase-2, the effect of stand lay orientation on tensile properties of bulk bioplotted PCL structures was determined. In the context of this study, bulk refers to a specimen bioplotted with non-porous gage sections, i.e., adjacent strands printed with no inter-strand spacing. These bulk tensile properties were critical in creating the FE model. Finally, in Phase-3, using the strand width data from Phase-1 and tensile testing results from Phase-2, an FE model was developed and validated to computationally estimate the tensile strength of 3D bioplotted porous PCL structures.