Engineering Starch for Non-Food Additive Manufacturing: Properties, Printability, and Emerging Uses
The development of sustainable materials for additive manufacturing (AM) has positioned starch as a compelling alternative to conventional thermoplastics. However, the successful implementation of starch in 3D printing (3DP) relies on precise control of its supramolecular organization, rheological behavior, and processing conditions. This article analyzes starch-based hydrogels for extrusion-driven AM, establishing explicit links between molecular architecture, gelatinization, and viscoelastic performance. The influence of key rheological parameters on extrudability and shape fidelity is examined in parallel with critical processing conditions. Chemical and physical modification routes of starch are compared in terms of their structural impact and printability enhancement. The integration of additives such as polysaccharides, proteins, and inorganic salts is discussed as a strategy to overcome intrinsic mechanical limitation. Emerging non-food application in drug delivery, tissue engineering, or conductive/intelligent hydrogels demonstrates the expanding technological relevance of starch-based formulation. Remaining challenges include predictive, rheology-based design, and the development of multifunctional 4D-printing capabilities. Progress in this field is crucial for positioning starch as a robust platform for sustainable AM, but, despite this progress, a systematic and quantitative framework linking starch molecular architecture and rheological behavior to printing-process parameters and outcomes is still lacking, thus constituting the central gap addressed in this review.