The invention relates to a microfluidic device for promoting crystallisation of target molecules, such as proteins. The device comprises a solid structure with a top face and an opposite bottom face and with a least one liquid channel. The liquid channel comprises a target molecule solution inlet and at least two precipitant inlets. The target molecule solution inlet is in liquid communication with each of the precipitant inlets through the liquid channel. The liquid channel comprises a branching channel section adjacent to the target molecule solution inlet, crystallisation channel sections adjacent to the respective precipitant inlets and flow break channel sections arranged between the branching channel section and each of the crystallization channel sections. The liquid channel is branched from 1 to X in the branching channel section, wherein X is the number of crystallisation channel sections, and the flow break channel sections comprise a flow break arrangement capable of breaking up the liquid communication between said respective branching channel section and crystallisation channel sections.