Diamagnetic particle separation by shape in ferrofluids

Abstract

Separating particles, which can be either biological or synthetic, in a continuous label-free manner is essential to many applications. Magnetic separation has several advantages over other field-driven particle separation techniques. It, however, has been limited primarily to situations where particles differ in size or magnetization. We demonstrate in this paper a continuous-flow separation of equal-volumed spherical and peanut-shaped diamagnetic particles in a dilute ferrofluid. This separation is attributed to the shape-dependent magnetophoretic motion, which is the combined result of the shape dependences of the magnetic force and viscous drag. We also develop a three-dimensional numerical model to understand this shape-based diamagnetic particle separation and predict the effects of the determining factors.