  Comprehensive understanding of particle motion in microfluidic devices is
essential to unlock novel technologies for shape-based separation and sorting
of microparticles like microplastics, cells and crystal polymorphs. Such
particles interact hydrodynamically with confining surfaces, thus altering
their trajectories. These hydrodynamic interactions are shape-dependent and can
be tuned to guide a particle along a specific path. We produce strongly
confined particles with various shapes in a shallow microfluidic channel via
stop flow lithography. Regardless of their exact shape, particles with a single
mirror plane have identical modes of motion: in-plane rotation and cross-stream
translation along a bell-shaped path. Each mode has a characteristic time,
determined by particle geometry. Furthermore, each particle trajectory can be
scaled by its respective characteristic times onto two master curves. We
propose minimalistic relations linking these timescales to particle shape.
Together these master curves yield a trajectory universal to particles with a
single mirror plane.
