de Kergariou, CharlesDay, Graham J.Perriman, Adam W.Armstrong, James P.K.Scarpa, Fabrizio2026-03-292026-03-291744-683XPubMed:38695256ORCID:/0000-0003-2205-9364/work/209746243https://hdl.handle.net/1885/733808035The mechanical and printing performance of a new biomaterial, flax fibre-reinforced alginate-poloxamer based hydrogel, for load-bearing and 4D printing biomedical applications is described in this study. The-self suspendable ability of the material was evaluated by optimising the printing parameters and conducting a collapse test. 1% of the flax fibre weight fraction was sufficient to obtain an optimum hydrogel composite from a mechanical perspective. The collapse test showed that the addition of flax fibres allowed a consistent print without support over longer distances (8 and 10 mm) than the unreinforced hydrogel. The addition of 1% of flax fibres increased the viscosity by 39% and 129% at strain rates of 1 rad s−1 and 5 rad s−1, respectively, compared to the unreinforced hydrogel. The distributions of fibre size and orientation inside the material were also evaluated to identify the internal morphology of the material. The difference of coefficients of moisture expansion between the printing direction (1.29 × 10−1) and the transverse direction (6.03 × 10−1) showed potential for hygromorphic actuation in 4D printing. The actuation authority was demonstrated by printing a [0°; 90°] stacking sequence and rosette-like structures, which were then actuated using humidity gradients. Adding fibres to the hydrogel improved the repeatability of the actuation, while lowering the actuation authority from 0.11 mm−1 to 0.08 mm−1. Overall, this study highlighted the structural and actuation-related benefits of adding flax fibres to hydrogels.CdK, FS and AWP would like to thank the UK Defence Science and Technology Laboratory for funding received for this project through the UK-France PhD Scheme (Grant ID: DSTLX-1000141168). CdK, FS and AWP would also like to acknowledge the support of the ERC-2020-AdG 101020715 NEUROMETA project. JPKA acknowledges funding from a UKRI Future Leaders Fellowship (MR/V024965/1). Ecotechnilin is also thanked for providing the flax fibres used in this work. The corresponding author would also like to thank Ms Francisca Marau dos Reis for her help with the collapse test. Finally, the corresponding author, CdK, would like to thank the EPSRC Doctoral Prize Fellowship for supporting the completion of this work (ID Grant: EP/W524414/1).14en©2024 The authors2024-05-0210.1039/d4sm00135d85192332432