Analysis of the video shows that the change in brightness in the 500 µm after the junction, I in Fig. , correlates very well with ∆P (Fig. ). Thus, the required driving pressure increases to maintain a constant flow rate as the gel occludes the channel. Also due to constant flow rate, occlusion causes an increase in the fluid velocity and, therefore, the viscous shear stress on the wall. At a certain level of occlusion, shear stress pulls the clog from the wall and flushes it out of the device, returning the driving pressure to baseline. For this reason we refer to peaks in ∆P as ∆P Abl , the magnitude of which reflects the degree of occlusion. The gel then builds again, and, remarkably, the process repeats for up to hundreds of gel deposition/ablation events over several hours (Fig. ).