Mixing an alginate stream with a calcium stream at constant Q T in a microfluidic Y-junction results in one of several phenomena. In the absence of calcium, alginate flows through the micro-channel without clogging, even at concentrations as high as C Alg = 10 mg/mL. At high concentrations of alginate and calcium, the system clogs irreversibly. In between these two extremes of flow and clogging, an interesting intermittent flow behavior emerges. Fig. shows ∆P (t) during this intermittent flow. The system demonstrates periodic behavior where, starting at t i0 and a baseline ∆P 0 (triangles), the pressure begins to increase. ∆P then reaches a maximum (circles), followed by an abrupt drop in pressure back to ∆P 0 . The cycle then continues, with increases in ∆P (t) reaching a relatively constant maximum value before falling back to the baseline ∆P 0 . The supplementary video "Annotated Deposition and Ablation.mp4" shows the synchronized microscopy and pressure trace data of a deposition/ablation event in real time with descriptive annotations. A phase contrast microscopy video of the first 1.2 mm of the channel after the junction is shown on the top. Alginate flows in through the channel at the top of the image, at C Alg = 0.1 mg/mL, while the calcium solution flows in from the channel at the bottom of the image, at C Ca 2+ = 100 mM. Fluid flows from left to right in the frame; Q T = 12.0µL/min, and the linear velocity of the fluid is 20 mm/s. The trace of the driving pressure is shown below the microscopy video, plotted as a dashed line and corresponding to the pressure trace seen in Fig. . The annotated video begins with a clean channel following an ablation event. Immediately, gel begins to deposit on the channel wall, starting at the junction where the streams meet. The gel deposit continues to grow for 39s, as evidenced by the darkening of the channel. Concurrently, the driving pressure increases to maintain a constant flow rate. Ablation occurs at 0:39, and the driving pressure returns to baseline within 5s. A slight transverse motion of the gel starts just before 10s, in which the gel moves ∼ 10µm in a few seconds. It is worth noting that this displacement occurs at a rate much slower than the linear velocity of the fluid. The annotated video documents approximately the first minute of Fig. in real time. A second supplementary video file, "Intermittent Deposition and Ablation.mp4", is also one minute long: it shows the microscopy and corresponding pressure trace seen in Fig. in its entirety, sped up by a factor of 5. Both videos are approximately one minute long.