The microfluidic device contains 165 parallel tapered channels, all connected to an inlet reservoir. The width of each channel is w c = 40 µm at the inlet. It tapers to 4 µm at the outlet over a length l c ≈ 5 cm, at an angle θ ≈ 0.02 • (Fig. ; not to scale). The channels are ∼10 µm deep, allowing up to two layers of particle packing in each clog. The microfluidic devices are fabricated with polydimethylsiloxane (Dow SYLGARD TM 184) using standard soft lithography methods. The elastomer base and curing agent are mixed in the ratio 8:1, and allowed to cure in an oven at 65 • C. The surface of the device containing the channels is plasma cleaned and bonded on a microscope glass slide. The glass slides are also plasma cleaned before bonding. This treatment makes the surfaces of the channels hydrophilic. Hydrophobicity returns to the PDMS device on a time scale of hours after plasma treatment . Therefore, devices are used immediately upon bonding.