The operation of this cell sorting mechanism relies on two key design principles: First, cells are deformed through an asymmetrical, funnel-shaped constriction, which we previously showed to require less pressure to transit cells in the direction of the taper (Fig. 1B) than against the taper (Fig. 1C)38. Second, cells are transported using a biased oscillatory flow that results in a net upward migration. The coupling of these two effects enables selective transport of cells based on their ability to deform through microscopic constrictions in a ratcheting manner. The ability to filter cells using oscillatory flow is essential to the perpetuation of the filtration process, as each reverse flow clears the funnel filters of non-specific adherent cells to eliminate clogging, which enables the processing of high-density samples like whole blood. Moreover, since cells come into contact with the funnel filters only momentarily during oscillatory flow, the hydrodynamic resistance of the filter, and consequently the filtration force experienced by each incoming cell, remains consistent during the entire process (supplemental information, Figure S1, Table S1). Finally, unlike traditional binary separation, the array-based sorting process allows a heterogeneous sample to be sorted into multiple fractions in a single run.