We record gel deposition, clog formation and ablation using an inverted microscope (Leica DMi8) at 10x magnification in phase contrast mode. Images collected from several different devices and over different conditions show that the gelation looks approximately the same, even despite differences in the smoothness of the channel wall (SI Fig. ). Two videos of flow through the first 1.2mm of the channel beyond the junction with simultaneous measurement of ∆P can be found in the SI. One video represents 5 minutes of footage, sped up by a factor of 5. The other shows the first minute of the same footage in real time, capturing a single deposition and ablation event, with annotations added to describe the process. The location of the sidewalls of the channel remains fixed during the duration of the flow test, despite deposition and ablation events, suggesting that the presence of alginate gel does not lead to deformation of the PDMS device.