The invention relates to a microfluidic device (3) comprising: - an inlet channel (31) having an inlet configured to be operatively connected with a droplet source (2) wherein the inlet channel (31) has a width wi and height hi; and - an outlet channel with at least one outlet channel branch (32) operatively connected with the inlet channel (31) at a passage point (33), said outlet channel (32) having a width wo, wherein the width wo of the at least one outlet channel branch (32) and the height ℎi and the width wi of the inlet channel (31) satisfy a geometrical condition of formula (I), said z > 1.