Fabrication and characterization of patterned carbon nanotube flow sensor cell

Patterned flow sensor cell consisting of single-walled carbon nanotubes (SWCNTs) network and polydimethylsiloxane (PDMS) are fabricated, based on the process of vacuum filtration, photolithography, and plasma etching. The sensor cell is a composite thin film and packaged to form a flow sensor, and then tested in different flow rates with different liquids, such as deionized (DI) water and NaCl solution. The induced-voltage increases with increasing flowing velocity and liquid concentration. The relation between induced-voltage and sensor cell conductivity is tested in the same liquid at the same flow rate. The higher the conductivity is, the higher the induced-voltage is. Some of the SWCNTs are fixed in the PDMS matrix, simultaneously some of them protrude above the composite thin film, which are exposed to the liquid and contribute to the voltage generation. The fabrication method can make the flow sensor scaled down to dimensions on the order of micrometers, which makes it suitable in very small liquid volumes.