A spoonful of sugar helps control fluid flow

04-Jun-2013 - USA

Research describes a simple, instrument-free method for controlling fluid flow in paper microfluidic devices by applying sugar solutions at different concentrations to slow down the flow of liquid.

Many diagnostic assays require the addition of several solutions and washing steps in a precise sequence that is carried out by either a human or a machine. The use of microfluidics to miniaturise such assays is now common, but until now no simple method reported for automated sequential addition in paper devices has been reported. Paper microfluidic devices have a useful application in point-of-care diagnostics. 

Scientists in the United States dried sugar solutions at different concentrations onto paper strips and showed that the sugar paper delayed the flow of fluid by minutes up to a whole hour. They designed a 2-dimensional branched paper network and applied different concentrations of sugar solution to each arm to create a device that allowed multiple fluids, which were applied to the device simultaneously, to be delivered sequentially to a detection zone. The scientists successfully applied this design to deliver a signal-amplified sandwich immunoassay for a malaria biomarker on paper.

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