Separation of suspensions can be carried out by microfiltration and microfluidic techniques, although both rely on different principles. Conventional microfiltration involves retention of particles by a porous membrane, but is limited by (irreversible) particle accumulation and concentration polarization that can only be (partially) controlled by back pulsing that transfers particles back into the bulk. Microfluidic separation devices employ a combination of inertial forces and sometimes geometric constraints to control particle migration behaviour, which allows splitting of suspensions into concentrated and diluted streams. Considering their effectiveness, inertia-based microfluidic separation is regarded an interesting alternative to microfiltration; therefore, this paper focusses on the use of inertial forces in suspension separation. This resulted in the selection of three concepts, which were: (1) fluid skimming, which is a combination of microfiltration and controlled particle migration behaviour, (2) spiral inertial microchannel separation, in which particles migrate fast towards an equilibrium position, and (3) sparse deterministic ratchets, which use geometric interactions to induce particle migration. In a concluding section, the application of controlled migration behaviour in relation to scalability of inertia-based microfluidic separation techniques and the effect of suspension properties on separation are discussed in detail. (C) 2016 Elsevier B.V. All rights reserved.