Miniature taste sensing system based on dual SH-SAW sensor device: an electronic tongue

Abstract

We report on the design and performance of a novel analytical sensing system, a so-called electronic tongue; it is based upon a dual shear horizontal surface acoustic wave (SH-SAW) device that discriminates between liquids of different basic tastes. Sixty megahertz SH-SAW dual delay-line sensors were micro-fabricated on 36° rotated Y-cut X-propagating LiTaO3 and placed below a miniature PTFE housing containing the liquid under test. In this SAW sensor one delay-line is electrically shorted and the other is free. Synthetic samples were analyzed with the four basic tastes of sour, salt, bitter, and sweet. The electronic tongue classified correctly all of the different basic tastes without a selective biological or chemical coating. Theory relating to the electro-acoustic properties represented by the relative permittivity and conductivity of the sample liquid is presented and related to experimental results. Dilution tests have also been performed in order to determine the detection limit of this physical taste sensor and hence its application potential.