Dynamics of capillary flow in an open superoleophilic microchannel and its application to sensing of oil
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We report the dynamics of capillary flow of oil in an open superoleophilic channel. The superoleophilic surface is fabricated by spin coating a layer of PDMS + n-hexane followed by candle sooting. The occurrence of various flow regimes, including the inertial, visco-inertial, and Lucas–Washburn regimes, are studied using analytical modelling as well as experiments. In case of a superoleophilic channel, much shorter inertial regime is observed as compared to that in an oleophilic channel due to the wicking of oil into the micro-roughness grooves ahead to moving bulk liquid meniscus. The study of the effect of channel aspect ratio \(\varepsilon\) on the mobility parameter \(k~\)showed that the mobility parameter \(k\) is maximum for an aspect ratio of \(\varepsilon =1.6\), which is attributed to the balance between the capillary and viscous forces. Finally, we demonstrate the application of the superoleophilic channel integrated with electrodes for impedance-based sensing of oil from an oil–water emulsion.
This work was supported by the Science and Engineering Research Board (SERB), Department of Science and Technology (DST), India, via Grant no. EMR/2014/001151 and IIT Madras via project no. MEE1516843RFTPASHS. The author would like to thank the NCCRD, IIT Madras for the measurements of viscosity and surface tension of the oil. The author would also like to thank Mr. N. Kumar for helping with the micro-milling operation.
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