We refer to the above device preparation as "pristine flow tests," in which particles are suspended in pure water and the channels surfaces are treated by plasma cleaning only. In a subset of flow tests, particles are dispersed in a 1 M NaCl solution to screen out electrostatic repulsion between particles. This induces both particle aggregation and deposition on the channel walls. In these flow tests, particles aggregate, deposit and clog upstream in the channels, in the widest portions of the channels and in the inlet area (see Videos S1 and S2 in SI). In another subset of flow tests, pristine channels are pretreated by flushing 5% CTAB through a device for at least 5 minutes before running the flow test. The CTAB prewash induces electrostatic attraction between the particles and the channel walls, causing particle deposition at the inlet of the channels (see Video S3 in SI). We also run one flow test after using a preflush of Aquapel TM to make the surface hydrophobic . Interestingly, making the channel surfaces hydrophobic does not change the clogging process (see Fig. in SI).