## 1 Introduction
[PERSON] and [PERSON] [28] studied the effect of build orientation on surface quality in rapid prototyping and found that as layer thickness decreases, traditional concerns about surface roughness due to inclined planes may diminish, and scan orientation within layers becomes a more important factor. This suggests that optimizing scan orientation may be critical to improving the surface quality of 3D printed parts. [PERSON] et al. [10] have further demonstrated the significant impact of printing orientation on the mechanical properties of SLA-printed resin samples, emphasizing the necessity for meticulous optimization toachieve optimal tensile strength, compressive strength, and flexural modulus. In particular, the influence of the rotation angle relative to the x, y, and z axes was subjected to a comprehensive investigation, revealing that strategic adjustments in these parameters can result in substantial improvements in mechanical performance. In a related study by [PERSON] et al. [29], an extensive experimental methodology framework was proposed for the study and characterization of materials printed by stereolithography (SLA). The authors' work concentrated on tensile and compression tests at varying strain rates, intending to elucidate the impact of printing parameters, including printing angles (0-90 degrees) and layer heights (100 \(\upmu\)m and 50 \(\upmu\)m). Moreover, the effects of curing time and temperature on the mechanical behavior of SLA-printed materials were examined. Current research on the mechanical properties of additively manufactured materials, particularly those produced via stereolithography, has focused primarily on quasi-static tensile and compressive tests. However, limited attention has been paid to the fracture toughness and energy release rate of these materials, especially in biocompatible applications. This knowledge gap is critical, as these properties are essential for ensuring the durability and safety of components in medical devices. Our study seeks to address this by evaluating the fracture toughness of LFS-printed biocompatible materials, contributing valuable insights to the field of biomedical engineering. This study aims to examine the fracture behavior of specimens produced using low-force stereolithography. In particular, the study determines the fracture toughness of compact polymer samples produced using Durable Resin by FormLabs (Somerville, MA, USA) [30], a material that emulates the strength and rigidity of polyethylene and is certified as biocompatible. The study examines the impact of print orientation by analyzing samples printed at 0\({}^{\circ}\), 45\({}^{\circ}\), and 90\({}^{\circ}\). Fracture toughness tests were conducted to determine the material's fracture toughness and energy release rate, in addition to the initial stiffness and peak load derived from the experimental data. Notwithstanding the considerable progress made in understanding the mechanical characteristics of AM materials, several constraints persist. Most studies have focused on quasi-static tensile and flexural tests, with relatively little attention paid to the dynamic performance or the impact of varying manufacturing parameters on mechanical behavior. Although this study focuses on quasi-static tests to evaluate fracture toughness and energy release rate, dynamic tests such as impact and fatigue tests are planned for future research to provide a more comprehensive understanding of the material's behavior. It is recommended that future research be expanded to include a broader range of testing conditions and materials, as well as the development of constitutive models to predict the behavior of 3D printed materials better. Implementing such models would facilitate using numerical tools to design materials more efficiently, optimize mechanical performance, and expand the practical applications of AM technologies.