Issue 1, 2019

Digital nanoliter to milliliter flow rate sensor with in vivo demonstration for continuous sweat rate measurement

Abstract

Microfluidic flow rate sensors have constraints in both detection limits and dynamic range, and are not often easily integrated into lab-on-chip or wearable sensing systems. We constructed a flow rate sensor that easily couples to the outlet of a microfluidic channel, and measures the flow rate by temporarily shorting periodic droplets generated between two electrodes. The device was tested in a dynamic range as low as 25 nL min−1 and as high as 900 000 nL min−1 (36 000× range). It was tested to continuously operate up to ∼200 hours. The device is also simple to fabricate, requiring inexpensive parts, and is small enough to be integrated into wearable devices. The required input pressure is as low as 370 Pascals. An ultra-low flow rate application was demonstrated for wearable sweat biosensing where sweat generation rates (nL min−1 per gland) were accurately measured in human subjects. The digital nanoliter device provides real-time flow rates for sweat rates and may have other applications for low flow rates in microfluidic devices.

Graphical abstract: Digital nanoliter to milliliter flow rate sensor with in vivo demonstration for continuous sweat rate measurement

Supplementary files

Article information

Article type
Paper
Submitted
12 sept. 2018
Accepted
20 nov. 2018
First published
07 déc. 2018

Lab Chip, 2019,19, 178-185

Author version available

Digital nanoliter to milliliter flow rate sensor with in vivo demonstration for continuous sweat rate measurement

J. Francis, I. Stamper, J. Heikenfeld and E. F. Gomez, Lab Chip, 2019, 19, 178 DOI: 10.1039/C8LC00968F

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