3D-Printed PLA Gyroid Filter Supports: Manufacturing, Mechanical Response and Hydrochar Deposition Screening

This study investigates the design, fabrication, and manufacturing/mechanical charac- terization of 3D-printed polylactic acid (PLA) cylindrical filter supports developed as substrates for subsequent hydrochar functionalization. Filters with an outer diameter of 30 mm, a height of 20 mm, and a wall thickness of 3 mm were manufactured by material extrusion additive manufacturing and internally filled with gyroid architectures generated in Bambu Studio at three density levels, namely 10%, 15%, and 20%. The printed filters were first evaluated in terms of weight and compressive response. The main focus of the work was the manufacturing consistency and mechanical response of the gyroid supports, while hydrochar deposition was considered as an initial functionalization screening step. The results showed that increasing gyroid density led to higher maximum compressive stress, while mass-normalized analysis revealed a trade-off between absolute mechanical re- sistance and material efficiency. Surface-treatment screening trials were then carried out on flat PLA specimens to evaluate whether algae-derived hydrochar could be retained on PLA after alkaline activation. Visual and SEM observations showed partial and heterogeneous hydrochar-related surface coverage, with localized agglomerates and partial masking of the original printing lines, but without the formation of a homogeneous coating. EDX analysis of selected agglomerates revealed C and O together with Na, Cl, K, and Ca, supporting the presence of hydrochar-related/mineral-containing deposits on the treated PLA surface, although K may also be associated with residual species from the KOH activation step. FTIR analysis did not reveal clear hydrochar-related spectral features, indicating that FTIR alone was not sufficient to demonstrate effective homogeneous surface functionalization and supporting the interpretation of heterogeneous surface retention. Overall, the study provides a first manufacturing-oriented basis for PLA gyroid filter supports intended for hydrochar deposition and highlights the need for improved surface activation strategies before subsequent functional validation.