Nanostructured films of poly(o-ethoxyaniline) and sulfonated polystyrene as sensing parts for taste sensor development

Nanostructured films of poly(o-ethoxyaniline) POEA and sodium sulfonated polystyrene PSS produced by the layer-by-layer technique (LBL) have been employed as part of sensory units in a taste sensor system, also known as electronic tongue (ET). The sensitivity of these films to standard taste solutions has been investigated by means of electrical capacitance measurements. At this moment we have observed that the film architecture plays an important role on the film electrical response to different tastes, which also depended on the frequency of the input signal. For instance, the sensitivity of films to sour (HCl 5mM) and salty (NaCl 5 mM) tastes increased as the number of POEA/PSS layers increased when they were interrogated in low frequency (100 Hz). However, at higher frequencies, above 1 kHz, the film sensitivity seemed to be independent on the number of POEA/PSS layers. Also, we have investigated the performance of these films in terms of reprodueibility and repeatability of their electrical response to different tastes. In general, the electrical response of POEA/PSS films has been highly reproducible and repetitive independently on the film architecture and frequency of interrogation. An array containing five LBL POEA/PSS films with different numbers of polymeric layers was able to distinguish liquids according to their taste and was also able to quantify NaCl at concentrations much lower than the human detection capacity. Such results have been demonstrating the potentiality of these films on the development of taste sensor systems.