Kinetic evaluation of the starch molecular behavior under extrusion-based or laser powder bed fusion 3D printing systems: A systematic structural and biological comparison

Supramolecular polymers are the most used materials for 3D printing applications because of their ability to improve the flow behavior of inks, and consequently enhance the mechanical strength of printed architectures. However, their interactions are assessed without considering the fact that their formed structures are affected by the printing process. Here, the effects of printer temperature of an extrusion-based printing system, or surface temperature of a laser powder bed fusion printer, on the molecular behavior of starch were investigated. Starch, being a highly branched polymer, was selected as the tested biopolymer since it provides numerous noteworthy benefits for an investigation of the depolymerization/crosslinking mechanisms upon printing, which could shed light on the impact of 3D printing on non-degradable materials. Completely different behaviors of starch functional properties are found between the two printing systems, where the extrusion-based printer promoted a significant degradation of the starch chains, while the laser powder bed fusion offered a typical behavior associated with crosslinking/branching. Extrusion 3D printing induced a reduction in starch molecular size and therefore in the structural strength of networks formed from it. However, this was also found to increase the starch digestibility rate/extent. In contrast, laser powder bed fusion increased the molecular size, inducing a viscoelastic gel-like character. At the same time, it decreased the starch digestion rate/extent. The obtained data offers information that can support the mechanistic interpretation of the depolymerization/crosslinking kinetics on the non-degradable materials, where it may be much harder to obtain the branch-length distribution. Therefore, the mechanistic information provided from starch can also be useful in understanding the degradation/chain branching of synthetic branched polymers undergoing the same printing processes.