Active pumping and control of flows in centrifugal microfluidics

This review is an account of centrifugal microfluidic systems that use various actuation strategies in addition to intrinsic centrifugal forces to accurately regulate the motion of fluids during rotation. Platforms that integrate active methods of pumping and flow control render centrifugal microfluidics more versatile as they facilitate integration and process automation by enabling (or improving the reliability of) important fluidic functions, such as metering, aliquoting, valving, flow switching, mixing, and inward pumping. Principles and working mechanisms underlying these strategies are described in the context of recent trends in instrument design and development where centrifugal platforms have been equipped with pneumatic, magnetic or electromechanical actuators serving as pumping and valving elements. The potential of these platforms to perform complex bioanalytical assays in an automated fashion is illustrated by several examples, which include on-chip preparation of aliquot libraries, nucleic acid purification, amplification and analysis as well as blood separation.