Cell scaffold blood-brain-barrier. (Credit: A. Marino/ Smart Bio-Interfaces, IIT Pontedera)

A microflow measurement system can track the movement of extremely tiny amounts of liquids — as small as nanoliters. The invention is designed to fill a need in the rapidly expanding field of microfluidics, in which precisely measuring tiny flow rates is critical. For example, some medical drug-delivery pumps dispense as little as tens of nL per minute into the bloodstream.

The optical microflow measurement system monitors the speed of fluorescent molecules in liquid as they travel down a channel about the width of a human hair, measuring the time interval between the molecules’ responses to two separate laser pulses.

To mark a start-time reference point, a UV laser pulse (with a wavelength of 375 nm) is fired along an optical wave-guide and into the channel. There, the pulse strikes a chemically protected fluorescent molecule moving in the stream. The flow rate is deduced from careful measurements of the time between laser pulses and the channel dimensions.

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