Abstract: A device for manipulating particles present in a fluid medium is disclosed. The device comprises a planar substrate, formed with at least one primary microchannel to allow passage of the fluid medium therethrough. The primary microchannel(s) has walls and a base and being in fluid communication with a plurality of secondary microchannels via at least one branching point. The device further comprises one or more ultrasound transmission pairs, positioned at opposite sides of the walls to generate ultrasound waves propagating through the fluid medium, substantially parallel to the planar substrate, such as to form a standing wave within the primary microchannel.