Discontinuous Clogging of Rigid Particles in Tapered Microchannels

This study describes the clogging of rigid particles in a microfluidic device made up of parallel microchannels which taper from the inlet to the outlet, where the constriction width is equal to the particle size. The geometry summarizes clogging dynamics in flow channels that narrow over multiple length scales. Flow tests are conducted at constant driving pressures for different particle volume fractions, and a power-law decay peculiar to the tapered geometry of the channels is observed in all cases. Compared to non-tapered channels, the power-law exponent shows the flow decay rate is significantly lower in a tapered channel. Changes in particle volume fraction at a constant driving pressure affect the clogging rate without impacting the underlying dynamics. Also, the post-clogging permeability of the device reveal two distinct driving pressure regimes, though only a small portion of the device volume and channels surface area were occupied by clogs, regardless of the particle volume fraction – which suggests differences in particle packing behavior.

Unlike non-tapered channels, clogs in the tapered channels do not grow continuously from their points of inception. Rather, multiple clogs with increasing number of particles in their cross section are successively formed as the cake grows: the growth of a clog is truncated by the formation of a new clog upstream. Features of this discontinuity are assessed by analyzing the distribution of the clog widths and lengths. The lengths are exponentially distributed while the widths follow a lognormal distribution. Interestingly, the exponential distribution of clog length suggests a Poisson process, in which clogging events are independent, while the lognormal distribution of width indicates simultaneous occurrence of multiple random processes during clog growth. Evidence supports that the formation of discontinuous clogs in parallel tapered channels occurs both independently of, and dependent on, other clogs.