Abstract:We describe two novel centrifugal microfluidic platform designs that enable passive pumping of liquids radially inward while the platform is in motion. The first design uses an immiscible liquid to displace an aqueous solution back towards the center of the platform, while the second design uses an arbitrary pumping liquid with a volume of air between it and the solution being pumped. Both designs demonstrated the ability to effectively pump 55% to 60% of the solution radially inward at rotational frequencies as low as 400 rpm (6.7 Hz) to 700 rpm (11.7 Hz). The pumping operations reached completion within 120 s and 400 s respectively. These platform designs for passive pumping of liquids do not require moving parts or complex fabrication techniques. They offer great potential for increasing the number of sequential operations that can be performed on centrifugal microfluidic platforms, thereby reducing a fundamental limitation often associated with these platforms.

A three-dimensional structure was constructed to demonstrate contact-free liquid addition and distribution to a conventional centrifugal microfluidic platform. The structure allowed a continuous stream of liquid to be added to the rotating platform where it was dispensed and metered to a series of reservoirs with 9% relative standard deviation of the volume. An off-platform generated gradient was used to demonstrate this design's potential to make gradient centrifugal microfluidic chromatography possible without the use of platform space for liquid storage. The system demonstrates a convenient and versatile "World-to-Chip" or more appropriately, World-to-Disk, macro-to-micro interface.