A multi-lumen mixing device is described. The multi-lumen mixing device includes a mixer body having an inlet portion and an outlet portion. The multi-lumen mixing device also includes an array of capillary channels within the mixer body, in which each capillary channel has approximately a same length. An inlet for each of the capillaries is proximate to the inlet portion and an outlet for each of the capillaries is proximate to the outlet portion. The array of capillary channels has at least three different cross-sectional areas.