We investigate the behaviour of a simple microfluidic device designed to separate particles based on density. The device consists of a separation-channel with three inlet and two outlet channels. The particle samples were loaded in the middle of the main channel. The results of separation experiments using model particles provide clear evidence that this approach can be used to achieve good separation of particles of close density populations. Particle separation was found more favourable with low flow rates. Forces exerted on particles were modelled by Stokes' law and found to be consistent with experimental results. One advantage of this microfluidic system is low exposure of the sample to hydrodynamic shear stresses compared with conventional methods. This device may be adopted to precisely handle single cells and easily interface with other tools and separation techniques.