The Fused Deposition Modeling (FDM) process often produces parts with high surface roughness, limiting their end-use applications, especially in the biomedical field. This paper presents an experimental study on improving the surface finish of 3D-printed polycaprolactone (PCL) samples using a robotic burnishing process. A key innovation is the development of a low-cost sensorless setup using a 5-DOF manipulator, which controls the applied force by correlating a precise robotic displacement with the known stiffness of springs via Hooke’s law. Ten PCL samples were tested using two burnishing directions: 90° (perpendicular) and 0° (parallel) relative to the printing orientation. The as-printed samples showed a highly anisotropic surface. The 90° trajectory (group 1) proved to be more effective in reducing primary roughness ($R_{a_{\perp }}$), lowering the mean $R_a$ from $2.11\mathsf{\mu }\mathrm{m}$ to $1.44\mathsf{\mu }\mathrm{m}$ (a mean reduction of 29.9%). In contrast, the 0° trajectory (group 2) was more effective in reducing roughness $R_{a_{\Vert }}$, lowering its mean $R_a$ from $0.225\mathsf{\mu }\mathrm{m}$ to $0.144\mathsf{\mu }\mathrm{m}$ (a mean reduction of 34.0%). The results demonstrate that the proposed sensorless system is a valid method for surface post-processing of FDM parts when the required forces fall below a specific threshold, ensuring a significant reduction in roughness without damaging the samples. The lower surface roughness obtained with the proposed post-processing strategy may represent a promising approach for improving the surface characteristics of FDM-fabricated polymer scaffolds intended for biomedical applications.

Cosmetic products contain numerous metals used as pigments, UV filters, preservatives, antiperspirants and antimicrobial agents, which are responsible for allergic skin reactions, with the most common being nickel. To reduce skin penetration of Ni, innovative pharmaceutical formulations such as lipogels with chelating action against the metal ions themselves can be used. Chelation therapy allows a chelating agent to combine with metal ions to form a stable ring structure called a chelate. The chelate structure is more soluble in water than the toxic metal, which facilitates removal of the toxic metal from the tissue and its excretion by the kidneys. The aim of the following work was to evaluate the chelating properties against nickel ions of different types of lipogels containing flavonoids such as resveratrol and epigallocatechin gallate with chelating activities largely dependent on the number and position of their hydroxyl groups. The results obtained showed that lipogels based on epigallocatechin gallate show high chelating action against nickel, especially at low concentrations. In addition, rheological studies showed an ideal profile to ensure viscoelasticity and swelling of the lipogel within 48 h, confirming reports of 75% epigallocatechin release from the lipogel after 48 h. Tests have shown that lipogels based on epigallocatechin gallate have high chelating action against nickel, especially at low concentrations.

Extrusion-based bioprinting is one of the most accessible and versatile additive manufacturing techniques for bioengineering applications, enabling the controlled deposition of a wide range of materials, including hydrogels. These soft and viscoelastic materials, composed of polymeric chains connected by physical or chemical bonds, are crucial in ensuring cell viability and proliferation, because of their ability in absorbing significant amounts of liquid. In this context, shape fidelity, defined as the degree of correspondence between the printed construct and its digital model, emerges as a critical performance metric. This study investigates the influence of key process parameters, i.e. inlet pressure, printing speed and bio-ink temperature, on shape fidelity in the extrusion bioprinting of two hydrogels: a natural alginate/cellulose blend and a synthetic polyethylene glycol-based material. Comprehensive rheological characterization, including oscillatory tests and flow curves, was performed to assess the materials’ viscoelastic behavior and shear-thinning properties. A shape fidelity index (SFI) was introduced and applied to quantify dimensional accuracy across 24 different parameter configurations. The resulting construct quality revealed clear correlations between process conditions and material rheology. The synthetic hydrogel exhibited greater stability under varying process conditions, making it easier to achieve high SFI values. In contrast, the natural hydrogel was more sensitive to the applied process parameters, showing notable instability. Nevertheless, when optimized input variables are used, the natural hydrogel can attain even higher SFI values. These findings underscore the importance of integrated rheological analysis and parameter optimization for advancing bioprinting performance and improving the fabrication of complex and high-resolution biomedical structures.