In situ printing of biphasic jammed inks for conformal deposition on convex anatomical surfaces, with microgravity validation

Abstract Rapid in situ bioprinting on complex, human-scale anatomical surfaces remains a key challenge for point-of-care use. Precise biomaterial ink or bioink deposition is required not only in operating theatres but also in resource-limited environments such as rural clinics and spaceflight missions. Here, we present a strategy for rapidly and conformally delivering biphasic biomaterial inks and bioinks composed of jammed gelatin microgels, optionally suspended in a cell-laden fibrinogen matrix. The formulation exhibits yield-stress behavior, preserves shape fidelity immediately after extrusion independent of gelation kinetics, maintains cell viability above 85%, and supports proliferation. The bioink is delivered through multinozzle printheads with 16 exit nozzles. During deposition at 450 mm ² ·s ⁻¹ , a ladder-rung channel architecture provided more uniform area coverage compared with a bifurcated design. Two printhead configurations were investigated: (1) a pneumatically actuated soft-robotic printhead with real-time adaptation to physiologically relevant convex surface curvatures, and (2) a rigid printhead integrated with a handheld bioprinter that enabled the first demonstration of biphasic jammed biomaterial ink deposition in microgravity. Considered radii of curvature and gravitational accelerations ranged from 10–100 mm and 0–1 g, respectively. Together with fibrin network formation, these results establish a translationally relevant biofabrication framework for in situ bioprinting in regenerative medicine, austere trauma care, and space-based healthcare.