Development of a taste sensor with high sensitivity, stability and selectivity is highly desirable for the food and beverage industries. The main goal of a taste sensor is to reproduce five kinds of senses of humans, which is quite difficult. The importance of knowing quality of beverages and drinking water has been recognized as a result of increase in concern in environmental pollution issues. However, no accurate measuring system appropriate for quality evaluation of beverages is available. A highly sensitive microsensor using horizontally polarized Surface Acoustic Waves (SH-SAW) for the detection and identification of soft drinks is presented in this paper. Different soft drinks were tested using this sensor and the results which could distinguish between two popular soft drinks like Pepsi and Coca cola is presented in this paper. The SH-SAW microsensors are fabricated on 36°-rotated Y cut X propagating LiTaO3 (36YX.LT) substrate. This design consists of a dual delay line configuration in which one line is free and other one is metallized and shielded. Due to high electromechanical coupling of 36YX.LT, it could detect difference in electrical properties and hence to distinguish different soft drinks. Measured electrical characteristics of these soft drinks at X-band frequency using free space system show distinguishable results. It is clear from these results that the microsensor based on 36YX.LT is an effective liquid identification system for quantifying human sensory expressions.
In this paper we present design, fabrication and integration of a micro fluidic cell for use with the electronic tongue. The cell was machined using microstereo lithography on a Hexanediol Diacrylate (HDDA) liquid monomer. The wet cell was designed to confine the liquid under test to the sensing area and insure complete isolation of the interdigital transducers (IDTs). The electronic tongue is a shear horizontal surface acoustic wave (SH-SAW) device. Shear horizontally polarized Love-waves are guided between transmitting and receiving IDTs, over a piezoelectric substrate, which creates an electronic oscillator effect. This device has a dual delay line configuration, which accounts for the measuring of both mechanical and electrical properties of a liquid, simultaneously, with the ability to eliminate environmental factors. The data collected is distinguished using principal components analysis in conjunction with pre-processing parameters. The experiments show that the micro fluidic cell for this electronic tongue does not affect the losses or phase of the device to any extent of concern. Experiments also show that liquids such as Strawberry Hi-C, Teriyaki Sauce, DI Water, Coca Cola, and Pepsi are distinguishable using these methods.