An apparatus for passive sorting of microdroplets including a main flow channel, a flow stream of microdroplets in the main flow channel wherein the microdroplets have substantially the same diameter and wherein the flow stream of microdroplets includes first microdroplets having a first degree of stiffness and second microdroplets having a second degree of stiffness wherein the second degree of stiffness is different than the first degree of stiffness. A second flow channel is connected to the main flow channel for the second microdroplets having a second degree of stiffness. A separator separates the second microdroplets having a second degree of stiffness from the first microdroplets and directs the second microdroplets having a second degree of stiffness into the second flow channel.