One example provides a microfluidic mixing device that includes a main fluidic channel to provide main fluidic channel flow and a number of I-shaped secondary channels extending outwardly from a portion of the main fluidic channel. A number of inertial pumps are located within the I-shaped secondary channels to create serpentine flows in the direction of the main fluidic channel flow or create vorticity-inducing counterflow in the main fluidic channel.