(482b) Intermittent Flow Dynamics of Polymers Crosslinking in Situ through a Microchannel

In this talk we present a study of intermittent flow dynamics of in situ cross-linking polymers. We investigate a model system of alginate polymers crosslinked by calcium, in which the merging of the two fluid streams at a microfluidic junction at constant flow rate leads to gelation, deposition, and occlusion of the channel. Rather than stop the flow in all cases, however, in situ gelation can lead to persistent, reproducible pattern of deposition and ablative removal of the adhered gel. We investigate the control of this intermittency as a function of flow rate, crosslinking density, and the concentration of the crosslinked gel. We find that, while the gel concentration strongly increases the frequency of ablation, increasing the crosslinking density has a lesser effect. The limits of the phenomena occur at high crosslinking density and high gel concentration, in which case the gel completely occludes the channel and causes clogging. Understanding this phase diagram lends important insights into the most efficient regimes for 3D printing and other additive manufacturing techniques in which crosslinking is desired somewhat before the material reaches the substrate. Furthermore, our investigations reveal a potential novel mechanism for the single-phase formation of very soft rodlike microgels.