A novel system for measuring liquid flow rates with nanoliter per minute resolution

An experimental system for liquid flow-rate measurements of pressure-driven flow through microchannels is described. The displacement of a meniscus is tracked in a precision borehole using a laser distance meter mounted on a feed-back controlled traversing stage. Successful measurements of flow rates as small as 30 pl/s are reported when using non-evaporative hexadecane, and evaporative fluids such as ethanol are measured at flow rates of 0.1 nl/s. The set-up can also be used for measurements in time-dependent flows. Finally, a discussion of the influence of dissolved nitrogen on the measured flow rates is given.