We present a novel, smart sensing system developed for the flavour analysis of liquids. The system comprises both a so-called "electronic tongue" based on shear horizontal surface acoustic wave (SH-SAW) sensors analysing the liquid phase and a so-called "electronic nose" based on chemFET sensors analysing the gaseous phase.Flavour is generally understood to be the overall experience from the combination of oral and nasal stimulation and is principally derived from a combination of the human senses of taste (gustation) and smell (olfaction). Thus, by combining two types of microsensors, an artificial flavour sensing system has been developed. Initial tests conducted with different liquid samples, i.e. water, orange juice and milk (of different fat content), resulted in 100% discrimination using principal components analysis; although it was found that there was little contribution from the electronic nose.Therefore further flavour experiments were designed to demonstrate the potential of the combined electronic nose/tongue flavour system. Consequently, experiments were conducted on low vapour pressure taste-biased solutions and high vapour pressure, smell-biased solutions. Only the combined flavour analysis system could achieve 100% discrimination between all the different liquids. We believe that this is the first report of a SAW-based analysis system that determines flavour through the combination of both liquid and headspace analysis.
2016) High frequency surface acoustic wave resonator-based sensor for particulate matter detection. New SAWR based particle sensor, capable of detection of sub-micron size particles with masses below 1 ng. Sensitive, low-cost and robust acoustic sensor for particulate matter (PM10, PM2.5, UFP) detection for air-quality monitoring. Novel SAWR design with free and shorted sensing areas, used in differential mode of operation. Potential for low-power monolithic CMOS implementation. Frequency dependent sensitivity of SAW resonators can be tailored to the size of particles to make them capable for UFPs, PM2.5 and PM10 detection.Abstract: This paper describes the characterization of high frequency Surface Acoustic Wave Resonator-based (SAWR) sensors, for the detection of micron and sub-micron sized particles. The sensor comprises two 262 MHz ST-cut quartz based Rayleigh wave SAWRs where one is used for particle detection and the other as a reference. Electro-acoustic detection of different sized particles shows a strong relationship between mass sensitivity (Δf/Δm) and particle diameter (Dp). This enables frequency-dependent SAWR sensitivity to be tailored to the size of particles, thus making these types of sensors good candidates for PM10, PM2.5 and ultrafine particle (UFP) detection. Our initial characterisation demonstrated a typical SAWR frequency shift of 60 Hz in response to a deposition of ca. 0.21ng of 0.75 µm-sized gold particles (~50 particles) on sensor's surface. Sensor responses to different size particles, such as ~30 µm diameter silicon, gold (diameters of ~0.75 µm and ~20 µm), ~8 µm fine sugar, PTFE (~1 µm and ~15 µm), ~4 µm talcum powder, and ~2 µm molybdenum powder were evaluated, and an average mass sensitivity of 275 Hz/ng was obtained. Based on the results obtained in this study we believe that acoustic wave technology has great potential for application in airborne particle detection. Moreover, acoustic resonator devices can be integrated with CMOS interface circuitry to obtain sensitive, robust, low-power and low-cost particle detectors for variety of applications including outdoor environmental monitoring.
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