Pillar-based microfluidic filters for size-based particle separation are limited by clogging. In dead-end filters, micropillars are arranged perpendicular to the flow to facilitate capture of rare cells. But these filters get clogged fast (~ minutes). Cross-flow filters avoid clogging by arranging the pillars parallel to the main flow and use side flows to sort smaller particles. We report a novel microfluidic filter that combines the respective advantages of dead-end and cross-flow designs. We have separated 1µm polystyrene beads from 7µm beads with 99% purity. The device could operate for ~ 8 hours without clogging or needing any reverse flow.