Fagner Rodrigues Todão/LNNano
Electronic tongues (e-tongues) are promising analytical devices for a variety of applications by addressing the challenges of quality control in water monitoring and industries of foods, beverages, and pharmaceuticals. A crucial drawback is currently related to the necessity in recalibrating the device when one or more sensing units (usually with modified surface) have to be replaced. Other downside is the necessity to perform subsequent surface modifications and analyses to each one of the diverse sensing units, undermining the simplicity and analytical frequency of the method. All of these features have prevented a widespread commercial use of the e-tongues. Recently, researchers from Microfabrication Laboratory (LNNano/CNPEM) addressed a microfluidic e-tongue that overcomes all these limitations. The key principle of global selectivity of the e-tongue was achieved by recording only a single response, the equivalent admittance spectrum of an association of resistors in parallel regardless of the number of sensing units. Such resistors consisted of five non-functionalized stainless steel microwires (sensing units), which were in short circuit and coated with thin films of gold (Au), platinum (Pt), nickel (Ni), iron (Fe), and aluminum oxide (Al2O3). The microwires were inserted in a microchip composed of a single piece of polydimethylsiloxane (PDMS). Using impedance spectroscopy, the e-tongue was successfully applied in the classification of basic tastes at a concentration below the threshold for human tongue. In addition, our chip allowed the distinction of various contents of chemicals that are used in the oil industry. Finally, the cleanroom-free prototyping herein used allows the mass production of chips with easily replaceable and reproducible sensing units. Hence, one can now envisage the widespread dissemination of e-tongues with fast and reproducible results.