Microbial biosurfactant hydrogels with tunable rheology for precision 3D printing of soft scaffolds

Bio-based surfactants, derived from microbial fermentation, are appealing biocompatible amphiphiles traditionally employed in depollution, pest control, personal care, cosmetics, and medicine, although their potential in biomedical scaffolds remains largely unexplored due to the limited adaptability of their rheological properties for extrusion-based 3D printing. This work demonstrates that microbial biosurfactants can function as low-molecular-weight gelators with facile, tunable rheological functionalities, enabling their integration into additive-free 3D printing processes. A hydrogel, formed by complexing a single-glucose oleyl lipid surfactant with calcium ions, exhibits shear-thinning behavior, viscoelasticity, yield stress, thixotropic response, and elongational properties, all essential for extrusion-based printing. A comprehensive rheological study reveals that the hydrogel's shear-thinning behavior allows controlled extrusion using conventional methods, while its yield stress ensures structural integrity by resisting capillary and gravitational stresses during deposition. Furthermore, the hydrogel demonstrates rapid stress recovery, enabling it to rebuild yield stress post-extrusion and prevent spreading. It's controlled fragility under stretching and shear ensures that structures can be printed without significant deformation, maintaining high fidelity throughout the process. Beyond its printability, the hydrogel exhibits stimuli-responsive functionality, particularly pH sensitivity, unlocking opportunities for 4D printing applications, where material properties evolve dynamically post-fabrication. This work positions biosurfactant-based hydrogels as a sustainable, high-performance material platform, paving the way for the use of this class of molecules for soft material engineering.