Slender body theory for ultrathin plates in two-dimensional viscous flow

Modelling ultrathin platelike particles in viscous flow is notoriously difficult due to the influence of their edges. This work introduces a two-dimensional slender body theory that bypasses these complexities by systematically excluding edge effects. Derived from the boundary integral formulation of Stokes flow, the theory reduces the problem to a nonlocal line integral along the particle's centerline. The resulting model accurately captures the flow and rheology of passive and active particles across a range of conditions.