Rheological optimization and aging-driven performance of glycolipid-based hydrogels for high-fidelity 3D printing

Microbial glycolipids are emerging as sustainable building blocks for soft bio-based materials, yet their use as extrusion-printable hydrogels remains limited by the lack of quantitative control over rheology, aging, and processing conditions. This study establishes a formulation rheology process map for a supramolecular hydrogel formed by complexation of the microbial glycolipid G-C18:1 with Ca²⁺ ions, aimed at high-fidelity extrusion-based 3D printing. Hydrogels were prepared over a range of G-C18:1 concentrations (3-10 wt%), calcium-to-glycolipid ratios (α = [Ca²⁺]/[G-C18:1] = 0.6-1.2), aging times (15 min to 5 days), and mixing protocols (pre-gelled versus in situ gelation). These variables were systematically mapped onto key rheological descriptors, storage modulus, yield stress, shear-thinning index, thixotropic recovery, and brittle extensional failure, and correlated with the printability of calibrated motifs such as hollow cylinders. A printable concentration threshold of ≈ 6 wt% G-C18:1 was identified under near-stoichiometric conditions (α = 0.9), while optimal fidelity for thin-walled, self-supporting structures was achieved at 10 wt% and α = 1.2. In this regime, the hydrogel combines a substantial yield stress (> 250 Pa, exceeding gravitational and capillary stresses), pronounced shear-thinning and rapid stress recovery (> 90% within a few seconds), with low-ductility, brittle filament failure that suppresses stringing during nozzle retraction. Aging reinforces the elastic modulus and yield stress over several days without altering the brittle fracture stress, leading to progressively improved structural fidelity. In contrast, in situ gelation strategies that rely solely on stopped-flow or static mixing fail to develop sufficient yield stress and homogeneity for robust printing. Overall, this work positions G-C18:1/Ca²⁺ hydrogels as a sustainable, high-performance platform and provides quantitative design rules for exploiting biosurfactant-based and more broadly low-molecular-weight gelator hydrogels in 3D bioprinting. • A rheology-informed framework is established to relate supramolecular assembly, aging, and mechanical behavior to extrusion printability in microbial glycolipid hydrogels. • Yield stress, shear-thinning behavior, extensional brittleness, and rapid structural recovery are quantitatively mapped to printability windows using calibrated extrusion motifs. • Calcium stoichiometry and controlled aging enable precise temporal tuning of gel mechanics, from immediate printability to delayed maturation. • The hydrogels are fully additive-free and formed from renewable microbial amphiphiles, offering a sustainable platform for extrusion biofabrication. • The study provides transferable design rules for low-molecular-weight supramolecular bioinks where kinetic evolution and shear history govern printing fidelity.