## 3 Results and Discussion
### Device Building  
The prototype required approximately 6 h to print the polymer components, which weighed 134 g (Figure 27), while the assembly and finishing process took about 3 h.  
The fully assembled device (Figure 28) reached a final weight of 240 g, an essential factor for the user adaptation process. The combination of mechanical strength and low  
Figure 27: Images of (**a**) printing the palm and directional coupling and (**b**) printing the wrist. Figure 26: Software-generated image for initiating the three-dimensional printing process. weight is crucial in the development of prosthetic devices, as it significantly contributes to efficiency and comfort during rehabilitation. In this context, the choice of a polymeric material like Tritan in the 3D printing process proved to be ideal. Tritan, in addition to being a lightweight material, allows for manufacturing with 25% infill, resulting in an effective density of approximately 1 g/cm\({}^{3}\). Its mechanical properties include a yield strength of 13.79 MPa, a maximum stress of 24.29 MPa, and an elasticity modulus of 332.54 MPa, characteristics that ensure a balance between lightness and robustness, making it an excellent choice for functional and comfortable prostheses. The stiffness of the material can be evaluated through the value of the modulus of elasticity, while the initial plastic deformation value can be assessed by the yield strength or limit. These values demonstrate that it is feasible to use Fused Deposition Modeling (FDM) technology in the fabrication of hand prostheses, providing the orthopedic device with good mechanical strength and lightness. After assembly, the prosthetic device was designed with the potential to be installed on the amputated limb using Velcro stabilizers with cushioned medical foam, protective sleeves, and tension adjustments made through a directional ratchet. These elements were planned to ensure comfort, stability, and functionality during daily use. The ratchet allows for the adjustment of the prosthesis movement through the tensioning of cables, while high-strength lines on the upper surface enable gripping movements at wrist flexion angles of 20\({}^{\circ}\) to 30\({}^{\circ}\). The calibration of these movements can be performed with a goniometer, which measures the angles of the phalanges and wrist, ensuring precision and efficiency. The mechanical functioning of the prosthesis is enabled by the use of high-density orthodontic elastics positioned on top of the interphalangeal joints, allowing for passive extension of the fingers. Finger flexion is achieved through high-strength cords fixed along the palmar surface and phalanges, activated by wrist flexion at angles of 20\({}^{\circ}\) to 30\({}^{\circ}\). This configuration enables coordinated movement, where the wrist acts to flex the fingers toward the palm, providing functionality and precision in the movements. This work focused on the development of the engineering aspects of the prosthesis, including material characterization and selection, design project, mechanical feasibility study through finite element analysis, and the development of parameterization for manufacturing. The prosthesis was designed to operate mechanically through muscular propulsion, incorporating elements such as directional coupling to adjust the biomechanical alignment of the prosthesis, high-density cords, screws, and other components that contribute to its functionality. Additionally, the material used in the prosthesis was chosen for its biocompatibility, ensuring that it does not cause allergic reactions on the user's skin. The prosthesis  
Figure 28: Images of the constructed device model. was designed to provide maximum functionality for future patients, taking into account adaptation to each individual's anatomy and needs. Although the prosthesis development was completed, it is important to emphasize that this study did not include any clinical validation phase.