An evaporation based digital microflow meter

Abstract

In this work, we present a digital microflow meter operating in the range 30–250 nl min−1 for water. The principle is based on determining the evaporation rate of the liquid via reading the number of wetted pore array structures in a microfluidic system, through which continuous evaporation takes place. A proof-of-principle device of the digital flow meter was designed, fabricated, and tested. The device was built on foil-based technology. In the proof-of-principle experiments, good agreement was found between set flow rates and the evaporation rates estimated from reading the number of wetted pore structures. The measurement range of the digital flow meter can be tuned and extended in a straightforward manner by changing the pore structure of the device.

Research and Application Progress of Intelligent Wearable Devices

“…As shown in Fig. 2A, Nie et al [45] prepared a flexible microfluidic chip for continuous detection of sweat for a long time. The chip was made of three layers of PET film.…”

“…The flexibility provided by scalability can not only relieve the mechanical strain Fig. 2 Common materials for wearable devices: (A) Flexible material [45] ; (B) Paper-based material [51] ; (C) Nanometer material [52] ; (D) Organic material [53] caused by bending, but also relieve the mechanical strain caused by other disturbances such as compression, tension and torsion [48] . The flexible and stretchable wearable device can be firmly combined with the skin, reduce the stress at the interface as much as possible, and realize the monitoring of human activities and personal health under the strong pressure generated in the process of normal body movement and muscle movement [49,50] .…”