Sensors Research Laboratory
University of Warwick
Tel: 02476 574494
Smart Electronic Tongue for Liquid Sensing
Novel liquid sensors, based on shear horizontal surface acoustic (SH-SAW) devices without selective membranes have been developed. The SH-SAW devices consist of two delay lines, one shorted (metallised and electrically shielded) and the other free (electrically active). This dual configuration allows the measurement of both the mechanical and acoustoelectric properties of the adjacent liquid analyte and removes common mode effects such as drift/fouling. The approach adopted is based on a generic fingerprint correlated to key physical parameters and does not employ any bio-chemical selective layers, thus ameliorating the problems with electrochemical type sensors and increasing the robustness and lifetime of the sensors.
The sensing system has demonstrated the ability to discriminate between four basic tastes without the use of selective membranes, responding to various physical parameters of the liquid ? an indirect measure of taste. A detection limit of < 0.1% was achieved. The theory of the electro-acoustic interactions has been used to relate the experimental results to electrical properties of the liquids. Complex samples related to more than a simple basic taste, such as cow?s milk, have been analysed. Milks of different fat contents have been classified with a very encouraging sensitivity figure of about 0.1% fat. Promising results were obtained on the milk freshness tests showing possible application of the sensors as milk freshness indicators. The taste sensors presented the ability to discriminate between different levels of sourness in milk, with an encouraging detection limit of ca. 102 - 103 cfu/ml, suggesting their possible application in the dairy industry and also biomedical sensing.