A lab-on-chip device for the processing, in particular the separation, of a fluid mixture comprising two immiscible phases (liquid and/or solid), said device comprising a fluid line (1,2,5,6) which successively includes an inlet reservoir (1), a separation channel (2), a collection channel (5) and an outlet (6), said separation channel (2) being designed in a way as to allow a separation of the fluid mixture into said two phases.