We present a geometrically scalable active micro-mixer suitable for biomedical and bioengineering applications and potentially assimilable in a lab-on-chip. Our micro-mixer is able to process volumes of fluid in the range of 10−6–10−9 l; its actuation system induces fast mixing; its constructive simplicity facilitates its realizability, assimilability and reusability; it is geometrically scalable and, therefore, assimilable to microfluidic systems of different dimensions. We characterize the mixing performance of our micro-mixer in terms of Reynolds, Strouhal and Péclet numbers in order to establish a practical range of operating conditions for our micro-mixer. Finally, we demonstrate the geometrical scalability of our micro-mixer.