Orthoses and prostheses (O&P) play crucial roles in assisting individuals with limb deformities or amputations. Proper material selection for these devices is imperative to ensure mechanical robustness and biocompatibility. While traditional manufacturing methods have limitations in terms of customization and reproducibility, additive manufacturing, particularly pellet extrusion (PEX), offers promising advancements. In applications involving direct contact with the skin, it is essential for materials to meet safety standards to prevent skin irritation. Hence, this study investigates the biocompatibility of different thermoplastic polymers intended for skin-contact applications manufactured through PEX. Surface morphology analysis revealed distinct characteristics among materials, with TPE-70ShA exhibiting notable irregularities. Cytotoxicity assessments using L929 fibroblasts indicated non-toxic responses for most materials, except for TPE-70ShA, highlighting the importance of material composition in biocompatibility. Our findings underscore the significance of adhering to safety standards in material selection and manufacturing processes for medical devices. While this study provides valuable insights, further research is warranted to investigate the specific effects of individual ingredients and explore additional parameters influencing material biocompatibility. Overall, healthcare practitioners must prioritize patient safety by meticulously selecting materials and adhering to regulatory standards in O&P manufacturing.

Nowadays, 3D printing is becoming an increasingly common option for the manufacturing of sensors, primarily due to its capacity to produce intricate geometric shapes. However, a significant challenge persists in integrating multiple materials during printing, for various reasons. In this study, we propose a straightforward approach that combines 3D printing with metal coating to create an array of resistive force sensors from a single material. The core concept involves printing a sensing element using a conductive material and subsequently separating it into distinct parts using metal-coated lines connected to the electrical ground. This post-printing separation process involves manual intervention utilizing a stencil and metallic spray. The primary obstacle lies in establishing a sufficient contact surface between the sprayed metal and the structure, to ensure effective isolation among different zones. To address this challenge, we suggest employing a lattice structure to augment the contact surface area. Through experimental validation, we demonstrate the feasibility of fabricating two sensing elements from a single-material 3D-printed structure, with a maximum electrical isolation ratio between the sensors of above 30. These findings hold promise for the development of a new generation of low-tech 3D-printed force/displacement sensor arrays.

Multi‐material pellet extrusion additive manufacturing (PEX‐AM) can integrate ultrasoft thermoplastic elastomers (TPEs) that are impractical as filaments. However, the reliability of the interfacial adhesion remains unknown. This study aims to quantify and optimize adhesion in ultrasoft (TPE30‐00) and soft (TPE45A) TPE systems manufactured via PEX‐AM. FT‐IR and thermal analyses are conducted to identify material and define stable processing windows. The processing windows of 195°C–225°C (TPE30‐00) and 195°C–245°C (TPE45A) are chosen accordingly. Interfacial performance is assessed using a modified ISO 11339 T‐peel geometry. Furthermore, a design of experiments (DoE) with a Taguchi L9 orthogonal array evaluates the main effects of head temperature/flow couples and raster angles for both materials. Mean peel resistance ranges from 273 to 881 N/m. The dominant factor is the TPE30‐00 head temperature/flow setting, followed by the raster angle of the TPE45A. The DoE increases the optimum peel resistance to 964.8 N/m and shifts failure toward cohesive fibrillation of the TPE30‐00 interlayer rather than premature interfacial debonding. Durability is tested by displacement‐controlled cyclic shear (Δδ = 10 mm, 2 Hz) to 10 ⁶ cycles. Dynamic modulus remains essentially stable, with changes lower than 4%, while the secant modulus decreases, consistent with viscoelastic/preloaded relaxation rather than interfacial degradation.