Buoyancy-driven centripetal pumping for nested sample preparation in bioassays

In this paper we present a method of buoyancy-driven centripetal pumping utilizing a heavy, water-immiscible liquid to displace an aqueous sample radially inwards against the prevailing centrifugal force. Using formerly introduced dissolvable-film valving, we demonstrate metering and bidirectional periodical pumping of a single sample in the radial direction. We then show integrated sample discretisation, meter-ing and buoyancy-driven inward pumping in a microfluidic structure designed towards multi-parameter bioassays. This structure permits centrifugation of sample on the periphery of a disc (where the centrifugal field p) and proves a high degree of metering accuracy better than 1.2%