Scaling Direct Ink Writing: A Multiscale Materials–Process–System Framework

ABSTRACT Direct ink writing (DIW) enables unparalleled materials diversity and multimaterial integration, yet its scalability remains fundamentally constrained. Achievable part‐size‐to‐feature‐size ratios rarely exceed three orders of magnitude, highlighting a persistent gap between laboratory‐scale resolution and manufacturing‐scale throughput. This review shows that this limitation is not incidental, but arises from tightly coupled, multiscale constraints that preclude monotonic scaling of DIW processes. We develop a unified framework that identifies six interacting sources of limitation, spanning nozzle geometry, flow‐rate and deposition dynamics, ink rheology, interlayer bonding, filament and structural mechanics, and system‐level control and environmental effects. We treat material classes as boundary conditions for scalability and formulate scaling relationships that connect throughput, recovery kinetics, bonding windows, filament stability, and attainable part‐size‐to‐feature‐size ratios. These relations distinguish scaling barriers that are fundamentally materials‐limited from those addressable through architectural or control innovations, and clarify how post‐deposition transformation and constraint ultimately bound manufacturability at scale.