Analysis of the Detection of Organophosphate Pesticides in Aqueous Solutions Using Hydrogen-Bond Acidic Coating on SH-SAW Devices

The work presented in this paper focuses on the synthesis and characterization of a hybrid organic/inorganic chemically sensitive layer for rapid detection and analysis of OPs in aqueous solutions using SH-SAW devices. Coated SH-SAW devices on 36° YX-LiTaO and 42.75° YX-Quartz (ST-90° X Quartz), are used to determine the optimum operating conditions for achieving rapid sensor responses with high sensitivity. Three analytes (parathion-methyl, parathion, and paraoxon), having similar molecular mass and volume, are used to evaluate the performance of the hybrid organic/inorganic coating in terms of sensor properties of interest including sensitivity, selectivity, reproducibility. It is shown that the coating has a high degree of partial selectivity and sensitivity towards the analytes. With the present non-optimized chemical sensor, a limit of detection of 60 (ppb), 20 (ppb) and 100 (ppb) is estimated for parathion-methyl, parathion, and paraoxon, respectively, when using a 0.5 -thick BPA-HMTS sensing layer. Concentrations as low as 500 (ppb) parathion have been measured. This concentration is significantly much lower than the typical concentrations found on agricultural produce (≥10 ppm)

Combined electronic nose and tongue for a flavour sensing system

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

Improved performance of motor-drive systems by SAW shaft torque feedback

The paper describes the application of a non-contact, high bandwidth, low cost, SAW-based torque measuring system for improving the dynamic performance of industrial process motor-drive systems. Background to the SAW technology and its motor integration is discussed and a resonance ratio control (RRC) technique for the coordinated motion control of multi-inertia mechanical systems, based on the measurement of shaft torque via a SAW-based torque sensor is proposed. Furthermore, a new controller structure, RRC plus disturbance feedback is proposed, which enables the controller to be designed to independently satisfy tracking and regulation performance. A tuning method for the RRC structure is given based on the ITAE index, normalized as a function of the mechanical parameters enabling a direct performance comparison between a basic proportional and integral (PI) controller. The use of a reduced-order state observer is presented to provide a dynamic estimate of the load-side disturbance torque for a multi-inertia mechanical system, with an appraisal of the composite closed-loop dynamics. The control structures are experimentally validated and demonstrate significant improvement in dynamic tracking performance, whilst additionally rejecting periodic load side disturbances, a feature previously unrealisable except by other, high-gain control schemes that impose small stability margins

Contactless measurement of electric current using magnetic sensors

We review recent advances in magnetic sensors for DC/AC current transducers, especially novel AMR sensors and integrated fluxgates, and we make critical comparison of their properties. Most contactless electric current transducers use magnetic cores to concentrate the flux generated by the measured current and to shield the sensor against external magnetic fields. In order to achieve this, the magnetic core should be massive. We present coreless current transducers which are lightweight, linear and free of hysteresis and remanence. We also show how to suppress their weak point: crosstalk from external currents and magnetic fields

Diamond semiconductor technology for RF device applications

This paper presents a comprehensive review of diamond electronics from the RF perspective. Our aim was to find and present the potential, limitations and current status of diamond semiconductor devices as well as to investigate its suitability for RF device applications. While doing this, we briefly analysed the physics and chemistry of CVD diamond process for a better understanding of the reasons for the technological challenges of diamond material. This leads to Figure of Merit definitions which forms the basis for a technology choice in an RF device/system (such as transceiver or receiver) structure. Based on our literature survey, we concluded that, despite the technological challenges and few mentioned examples, diamond can seriously be considered as a base material for RF electronics, especially RF power circuits, where the important parameters are high speed, high power density, efficient thermal management and low signal loss in high power/frequencies. Simulation and experimental results are highly regarded for the surface acoustic wave (SAW) and field emission (FE) devices which already occupies space in the RF market and are likely to replace their conventional counterparts. Field effect transistors (FETs) are the most promising active devices and extremely high power densities are extracted (up to 30 W/mm). By the surface channel FET approach 81 GHz operation is developed. Bipolar devices are also promising if the deep doping problem can be solved for operation at room temperature. Pressure, thermal, chemical and acceleration sensors have already been demonstrated using micromachining/MEMS approach, but need more experimental results to better exploit thermal, physical/chemical and electronic properties of diamond

Fabrication of high temperature surface acoustic wave devices for sensor applications

Surface acoustic devices have been shown to be suitable not only for signal processing but also for sensor applications. In this paper high temperature surface acoustic wave devices based on gallium orthophosphate have been fabricated, using a lift-off technique and tested for high frequency applications at temperatures up to 600 ºC. The measured S-parameter (S11) has been used to study the mass loading effect of the platinum electrodes and turnover temperature of GaPO4 with a 5? cut. The analysis of these results shows that the mass loading effect can be used to predict the desired resonant frequency of the SAW devices. Also two different adhesion layers for Pt metallisation were studied. Our results show that Zirconium is a more suitable under layer than Titanium

Compact personal distributed wearable exposimeter

A compact wearable personal distributed exposimeter (PDE) is proposed, sensing the power density of incident radio frequency (RF) fields on the body of a human. In contrast to current commercial exposimeters, our PDE, being composed of multiple compact personal wearable RF exposimeter sensor modules, minimizes uncertainties caused by the proximity of the body, the specific antenna used, and the exact position of the exposimeter. For unobtrusive deployment inside a jacket, each individual exposimeter sensor module is specifically implemented on the feedplane of a textile patch antenna. The new wearable sensor module's high-resolution logarithmic detector logs RF signal levels. Next, on-board flash memory records minimum, maximum, and average exposure data over a time span of more than two weeks, at a one-second sample period. Sample-level synchronization of each individual exposimeter sensor module enables combining of measurements collected by different nodes. The system is first calibrated in an anechoic chamber, and then compared with a commercially available single-unit exposimeter. Next, the PDE is validated in realistic conditions, by measuring the average RF power density on a human during a walk in an urban environment and comparing the results to spectrum analyzer measurements with a calibrated antenna

High-performance control of dual-inertia servo-drive systems using low-cost integrated SAW torque transducers

Abstract—This paper provides a systematic comparative study of compensation schemes for the coordinated motion control of two-inertia mechanical systems. Specifically, classical proportional–integral (PI), proportional–integral–derivative (PID), and resonance ratio control (RRC) are considered, with an enhanced structure based on RRC, termed RRC+, being proposed. Motor-side and load-side dynamics for each control structure are identified, with the “integral of time multiplied by absolute error” performance index being employed as a benchmark metric. PID and RRC control schemes are shown to be identical from a closed-loop perspective, albeit employing different feedback sensing mechanisms. A qualitative study of the practical effects of employing each methodology shows that RRC-type structures provide preferred solutions if low-cost high-performance torque transducers can be employed, for instance, those based on surface acoustic wave tecnologies. Moreover, the extra degree of freedom afforded by both PID and RRC, as compared with the basic PI, is shown to be sufficient to simultaneously induce optimal closed-loop performance and independent selection of virtual inertia ratio. Furthermore, the proposed RRC+ scheme is subsequently shown to additionally facilitate independent assignment of closed-loop bandwidth. Summary attributes of the investigation are validated by both simulation studies and by realization of the methodologies for control of a custom-designed two-inertia system

Fabrication And Thermoelectric Characterization Of Stretchable Conductive Latex-Based Composites

Miniaturized stretchable electronic devices that can be bent and strained elastically without breaking, have drawn considerable research interest in recent years for wearable computers and integrated bio-sensor applications. Portable electrical power harvesting remains a critical challenge in flexible electronics materials. One proposed solution has been to convert waste heat from the human body into electricity using thermoelectric materials. Traditionally, however, these materials are brittle ceramic semiconductors with limited fracture resistance under deformation. The primary objective of this thesis is to address this challenge by fabricating and studying the mechanical, thermal and electrical performance of stretchable composites combining natural latex polymer with either metallic (Ni) or thermoelectric (InSb) powders. Ni-based and InSb-based latex specimens were synthesized with different powder concentrations up to 36 vol.%. The effects of the powder concentration on tensile elongation, electrical conductivity, and thermal conductivity of the composites were measured at ambient temperature. Strong dependences of mechanical and electrical properties on powder concentration were found. By contrast, thermal conductivity was observed to remain low at all concentrations, suggesting that the predominant heat transport process is through the low-conductivity latex matrix rather than the conductive particles. This thesis was conducted with the support of a Vermont Space Grant Consortium graduate research assistantship

Wireless body sensor networks for health-monitoring applications

This is an author-created, un-copyedited version of an article accepted for publication in Physiological Measurement. The publisher is not responsible for any errors or omissions in this version of the manuscript or any version derived from it. The Version of Record is available online at http://dx.doi.org/10.1088/0967-3334/29/11/R01