Sensor Array for Water Analysis Based on Interdigitated Electrodes Modified With Fiber Films of Poly(Lactic Acid)/Multiwalled Carbon Nanotubes

A disposable low cost and simple flow-cell electronic tongue for water analysis is described. A sensor array is used that is comprised of six interdigitated microelectrodes coated with nanofiber films of poly(lactic acid)/mutliwalled carbon nanotube (MWCNT) composites. Fiber films are deposited directly on the interdigitated electrodes surface by solution blow spinning. Fiber film thickness is varied by using different deposition times (1, 3, and 15 min). Analysis of scanning electron microscopy and transmission electron microscopy micrographs indicates that average fiber diameters are 400 nm for neat poly lactic acid (PLA) and 200 nm for the PLA/MWCNT composite. The MWCNT is poorly dispersed in the PLA fiber matrix and formed aggregates interspersed throughout the fiber length. There are also MWCNTs exposed or partially exposed at the fiber surface. Fiber films containing MWCNT (1%) give the highest dc conductivity values and the most linear I-V profiles at room temperature. Sensor arrays with thin fiber film coatings (1 min deposition time) provide the best result for discriminating potable water samples using principal component analysis (PCA). The flow-cell electronic tongue coupled with PCA is used to discriminate potable water samples from non-potable water contaminated with metals or traces of pesticides.