<i>In situ</i>printing of biphasic jammed inks for conformal deposition on convex anatomical surfaces, with microgravity validation.

Abstract

Rapid<i>in situ</i>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 mm²·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<i>in situ</i>bioprinting in regenerative medicine, austere trauma care, and space-based healthcare.