Measuring out fluids microdrop by microdrop

HEADNOTE

Combining innovative sensors, precise pumps, valves with no dead volumes, and some elegant engineering lets designers deliver drugs and other fluids in small but accurate doses.

More and more lab equipment

is being built for medical research and diagnosis. And researchers want machines that can handle thousands of samples quickly, precisely, and efficiently. One way to do this is to design machines that use extremely small samples and amounts of reagents - in the submicroliter to nanoliter range. This lets chemicals react faster throughout the sample and reduces the amount of reagent and sample used, both of which can be expensive.

Delivering microdoses of liquids requires accurate flow measurement, small-volume pumps, and valves with no dead volume. Valves with significant dead volumes - the amount of fluid trapped in the valve when there is no flow - could dispense differing fluid volumes if the valve doesn't operate consistently. And fluid trapped in the valve can contaminate or "carry over" into the next sample. Until now, however, reliable interaction between these components has been a challenge in both lab and industrial applications. Engineers have answered this challenge with a microflow sensor that measures pressure differences across a fluidic restriction and controls a miniature valve for ultraprecise fluid control.