3D bioprinting involves the extrusion of bio-inks through narrow nozzles to enable fabrication of intricate shapes. Bio-inks are complex fluids typically composed of a mixture of cells and crosslinked bio-polymers. Bulk rheology is used to characterize inks and optimize their design . For proper flowability and printability, inks should be viscous, shear thinning, and have a high yield stress . Polymers can be crosslinked before, during, or after the print to influence these properties and form the hydrogel structure. Failure to optimize the ink appropriately may When alginate and calcium mix in a microfluidic Y-shaped junction at a flow rate ratio of 4:1, an interesting intermittent flow behavior emerges: the gel repeatedly deposits on channel walls and ablates. The flow phase diagram is labeled to indicate regimes of flow (blue), clogging (red), and intermittency (yellow) as a function of alginate and calcium concentrations. The plotted pressure traces correspond to the starred conditions. Data point color indicates deposition/ablation frequency; the color map is on a log scale. Data points in white indicate flow and in orange indicates clogs, or flow failure. The gel crosslinked in flow maintains its shape upon ablation to form micro-rods, as seen in fluorescence microscopy. Notably, this method of rod formation does not require a second, immiscible liquid. result in print failure. An example of failure is nozzle clogging, where some obstruction prevents the flow of ink through the nozzle. Clogging causes interruption in flow and consequent unevenness in the print, and may require the replacement of the nozzle during a print .