Abstract: A device for separating and concentrating particles present in a fluid, including: a first microchannel, having at least one first aperture; and at least one second microchannel, having at least one second aperture, and an end is disclosed. The first microchannel surrounds part or all of the second microchannel at the end. The first microchannel and the second microchannel are connected, at the end, by at least one nanochannel, the nanochannel(s) forming a restriction between the first microchannel and the second microchannel. A cap bounds the first microchannel, the second microchannel and the nanochannel at the end. The first microchannel and the second microchannel are made in a first substrate. The first aperture and the second aperture open into a same face of this substrate. The device may be used for separating and concentrating particles of biological samples, such as viruses, DNA or synthesic molecules.